Final Regulatory
u^tedCth Determination 4
Environmental Protection - ¦-* a
Agency Support Document
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Office of Water (4607M)
EPA 815-R-21-001
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Disclaimer
This document is designed to provide technical background information for
Environmental Protection Agency's (EPA's) fourth Regulatory Determination (RD 4) for
drinking water contaminants under Safe Drinking Water Act (SDWA) provisions, based on
EPA's fourth Contaminant Candidate List (CCL 4).
This document is not a regulation itself, and it does not substitute for SDWA or EPA's
regulations. Mention of trade names or commercial products does not constitute endorsement or
recommendations for use.
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Executive Summary
This document provides background information to support the U.S. Environmental
Protection Agency's (EPA) fourth Regulatory Determination (RD 4) for drinking water
contaminants under the Safe Drinking Water Act (SDWA) provisions, based on the fourth
Contaminant Candidate List (CCL 4). The regulatory determination decisions are presented in
the Federal Register. This report, which accompanies EPA's final regulatory determination, does
not itself constitute a regulation or a formal determination.
This regulatory determination support document consists of an introductory chapter on
the CCL 4 and RD 4 process (Chapter 1), a chapter on data sources and data evaluation (Chapter
2), and chapters (Chapters 3-10) devoted to contaminants receiving a final regulatory
determination under RD 4: perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid
(PFOA), 1,1-dichloroethane, acetochlor, methyl bromide, metolachlor, nitrobenzene, andRDX.
It also includes several appendices that present information on additional contaminants not
receiving a determination, an annotated bibliography of PFOS and PFOA references, and the
protocol that EPA followed in RD 4 decision-making.
EPA evaluates contaminants for regulatory determination based on three statutory
criteria. Regulation with a national primary drinking water regulation (NPDWR) is warranted if:
(a) the contaminant may have an adverse effect on the health of persons;
(b) the contaminant is known to occur or there is substantial likelihood that the
contaminant will occur in public water systems (PWSs) with a frequency and at levels
of public health concern; and
(c) in the sole judgment of the Administrator, regulation of such contaminant presents a
meaningful opportunity for health risk reduction for persons served by PWSs.
EPA may determine that a contaminant satisfies all three criteria and warrants a NPDWR
(a positive determination), or that it does not satisfy all three criteria and does not warrant
regulation at this time (a negative determination). Another possible outcome for a contaminant is
a decision to make no regulatory determination. SDWA requires EPA to make a minimum of
five regulatory determinations per cycle.
Following a standard protocol to evaluate contaminants against the statutory criteria, EPA
gathered data and information on health effects and occurrence in PWSs, as well as physical and
chemical properties; source, use, and release; environmental fate and transport; and occurrence in
ambient water. EPA also evaluated the availability of analytical methods and treatment
technologies.
EPA has made final determinations that PFOS and PFOA satisfy all three criteria and
warrant regulation in drinking water, and that 1,1-dichloroethane, acetochlor, methyl bromide,
metolachlor, nitrobenzene, and RDX do not satisfy all three criteria and do not warrant
regulation at this time. The final determinations are presented formally in the Federal Register.
As required by SDWA, EPA will initiate the process to propose a NPDWR for PFOA and PFOS
within 24 months of the publication of these determinations in the Federal Register.
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Contents
Disclaimer i
Executive Summary iii
Contents v
Chapter 1: Introduction 1-1
Chapter 2: Data Sources and Data Evaluation 2-1
Chapter 3: Perfluorooctanesulfonic acid (PFOS) 3-1
Chapter 4: Perfluorooctanoic acid (PFOA) 4-1
Chapter 5: 1,1-Dichloroethane 5-1
Chapter 6: Acetochlor 6-1
Chapter 7: Methyl Bromide 7-1
Chapter 8: Metolachlor 8-1
Chapter 9: Nitrobenzene 9-1
Chapter 10: RDX 10-1
Appendix A: Additional Information on Contaminants on the CCL Not Receiving a Regulatory
Determination as Part of Regulatory Determination 4 A-l
Appendix B: 1,4-Dioxane B-l
Appendix C: 1,2,3-Trichloropropane C-l
Appendix D: PFOS and PFOA Annotated Bibliography D-l
Appendix E: Regulatory Determination 4 Protocol E-l
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Chapter 1:
Introduction
A chapter from:
Final Regulatory Determination 4 Support Document
EPA Report 815-R-21-001
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Contents
Contents 1-3
Exhibits 1-4
Abbreviations 1-5
Chapter 1: Introduction 1-7
1.1 Purpose and Scope 1-7
1.2 Background on the CCL and Regulatory Determinations 1-7
1.2.1 Statutory Requirements for CCL and Regulatory Determinations 1-7
1.2.2 The First Contaminant Candidate List (CCL 1) 1-8
1.2.3 The First Regulatory Determination (RD 1) for CCL 1 1-9
1.2.4 The Second Contaminant Candidate List (CCL 2) 1-9
1.2.5 The Second Regulatory Determination (RD 2) for CCL 2 1-9
1.2.6 The Third Contaminant Candidate List (CCL 3) 1-10
1.2.7 The Third Regulatory Determination (RD 3) for CCL 3 1-12
1.3 The Fourth Contaminant Candidate List (CCL 4) 1-13
1.4 Overview of the Fourth Regulatory Determination (RD 4) for CCL 4 1-13
1.4.1 RD 4 Phase 1: Data Availability 1-13
1.4.2 RD 4 Phase 2: Data Evaluation 1-16
1.4.3 RD 4 Phase 3: Regulatory Determination Assessment 1-18
1.5 References 1-19
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Exhibits
Exhibit 1-1: General Overview of the Approach Used to Establish CCL 3 1-11
Exhibit 1-2: Contaminants Proceeding from Phase 1 to Phase 2 1-14
Exhibit 1-3: Contaminants Not Proceeding from Phase 1 to Phase 2 1-15
Exhibit 1-4: Contaminants Proceeding from Phase 2 to Phase 3 1-16
Exhibit 1-5: Data and Rationale Summary for the 15 Contaminants Not Proceeding from Phase 2
to Phase 3 1-17
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Abbreviations
AM
Assessment Monitoring
CCL
Contaminant Candidate List
CCL 1
First Contaminant Candidate List
CCL 2
Second Contaminant Candidate List
CCL 3
Third Contaminant Candidate List
CCL 4
Fourth Contaminant Candidate List
CCLCP
Contaminant Candidate List Classification Process
CSF
Cancer Slope Factor
DBP
Disinfection Byproduct
D/DBP
Disinfectants/Disinfection Byproduct
DDE
1,1 -Dichloro-2,2-bis(/>chlorophenyl)ethylene
DW
Drinking Water
EPA
Environmental Protection Agency
EPTC
»Y-ethyl dipropylthiocarbamate
ESA
Ethanesulfonic Acid
HA
Health Advisory
HHRA
Human Health Risk Assessment
HRL
Health Reference Level
IRIS
Integrated Risk Information System
MCLG
Maximum Contaminant Level Goal
MDBP
Microbial/Disinfection By-Product
NA
Not Applicable
NCOD
National Contaminant Occurrence Database
NDBA
N-nitrosodibutylamine
NDEA
N-nitrosodi ethyl amine
NDMA
N-nitrosodimethylamine
NDPA
N-nitrosodipropylamine
NDPhA
N-Nitrosodiphenylamine
NDWAC
National Drinking Water Advisory Council
NIRS
National Inorganics and Radionuclides Survey
NMEA
N-nitrosomethylethylamine
NPDWR
National Primary Drinking Water Regulation
NPYR
N-pyrrolidine
NRC
National Research Council
OA
Oxanilic Acid
OPP
Office of Pesticide Programs
OW
Office of Water
PCCL
Preliminary Contaminant Candidate List
PCCL3
Third Preliminary Contaminant Candidate List
PFOA
Perfluorooctanoic Acid
PFOS
Perfluorooctanesulfonic Acid
PPRTV
Provisional Peer-Reviewed Toxicity Value
PWS
Public Water System
RD 1
First Regulatory Determination
RD 2
Second Regulatory Determination
RD 3
Third Regulatory Determination
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RD 4
Fourth Regulatory Determination
RDX
Royal Demolition eXplosive
RfD
Reference Dose
SAB
Science Advisory Board
SDWA
Safe Drinking Water Act
ss
Screening Survey
TPTH
Triphenyltin Hydroxide
UCM
Unregulated Contaminant Monitoring
UCMR 1
First Unregulated Contaminant Monitoring Rule
UCMR2
Second Unregulated Contaminant Monitoring Rule
UCMR 3
Third Unregulated Contaminant Monitoring Rule
UCMR 4
Fourth Unregulated Contaminant Monitoring Rule
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Chapter 1: Introduction
1.1 Purpose and Scope
The 1996 Safe Drinking Water Act (SDWA) Amendments (section 1412(b)(1)) direct the
Environmental Protection Agency (EPA) to publish every five years a list of currently
unregulated contaminants that may pose risks for drinking water (referred to as the Contaminant
Candidate List, or CCL) and to make determinations every five years of whether to regulate or
not regulate with a national primary drinking water regulation (NPDWR) at least five
contaminants from the CCL.
This document supports EPA's fourth Regulatory Determination (RD 4), which is based
on an evaluation of contaminants on the fourth Contaminant Candidate List (CCL 4). This
regulatory determination support document provides:
• A summary of the statutory requirements, previous activities related to the CCL and
regulatory determinations, and the approach used to select and evaluate CCL 4
contaminants for RD 4;
• Background information on the data sources used to evaluate CCL 4 contaminants,
including data sources on physical and chemical properties, use and environmental
release, environmental fate, health effects, and occurrence and exposure; and
• A description of the information evaluated by the Agency for each contaminant,
including information and data on physical and chemical properties, use and
environmental release, environmental fate, health effects, and occurrence and
exposure.
The eight regulatory determination candidates discussed in this document are:
perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), 1,1-dichloroethane,
acetochlor, methyl bromide, metolachlor, nitrobenzene, and RDX, also known as royal
demolition explosive.
This document also includes several appendices. Appendices A-C present information on
a number of contaminants that are not receiving a regulatory determination. Appendix A covers
multiple contaminants in a summary table format. Appendices B and C present more detailed
information on two contaminants discussed individually in the Federal Register notice: 1,4
dioxane and 1,2,3-trichloropropane, respectively. Appendix D presents an annotated
bibliography for PFOS and PFOA. Appendix E presents the protocol that EPA used for
Regulatory Determination 4 decision-making.
1.2 Background on the CCL and Regulatory Determinations
1.2.1 Statutory Requirements for CCL and Regulatory Determinations
The statutory requirements for the CCL and regulatory determinations are presented in
SDWA Section 1412(b)(1). The 1996 SDWA Amendments require EPA to publish the CCL
every five years. The CCL is a list of contaminants that are not subject to any proposed or
promulgated NPDWRs, are known or anticipated to occur in public water systems (PWSs), and
may require regulation under SDWA to protect public health. SDWA requires consultation with
the scientific community, including EPA's Science Advisory Board (SAB); opportunity for
public comments; and consideration of the National Contaminant Occurrence Database (NCOD),
established under section 1445(g) of the Act. The 1996 SDWA Amendments also direct EPA to
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determine whether to regulate or not regulate at least five contaminants from the CCL every five
years. There are three criteria to be considered in making a regulatory determination. A decision
to regulate is warranted if:
(a) the contaminant may have an adverse effect on the health of persons;
(b) the contaminant is known to occur or there is substantial likelihood that the
contaminant will occur in PWSs with a frequency and at levels of public health
concern; and
(c) in the sole judgment of the Administrator, regulation of such contaminant presents a
meaningful opportunity for health risk reduction for persons served by PWSs.
If, after considering public comment on a preliminary determination, the Agency makes a
determination to regulate a contaminant, EPA will initiate the process to propose and promulgate
an NPDWR. In that case, the statutory time frame provides for Agency proposal of a regulation
within 24 months and action on a final regulation within 18 months of proposal. When proposing
and promulgating drinking water regulations, the Agency must conduct a number of analyses.
The Agency may determine that there is no need for a regulation when a contaminant fails to
meet one or more of the criteria. A decision to not regulate is considered a final Agency action
and is subject to judicial review. Since SDWA does not require EPA to make a regulatory
determination for all contaminants on the CCL, another possible outcome for some contaminants
is no regulatory determination. In the case of a negative determination or no determination, the
Agency may choose to publish a Health Advisory (HA), which is a non-regulatory action, or
issue other guidance.
Additional information about the statutory requirements, the procedures EPA uses to
comply with them, and the inter-relationships between the Regulatory Determinations and other
SDWA-mandated programs is provided in Appendix E.
1.2.2 The First Contaminant Candidate List (CCL 1)
The 1996 SDWA Amendments required EPA to publish the first CCL (CCL 1)18
months after the date of enactment. Following the 1996 SDWA Amendments, EPA sought input
from the National Drinking Water Advisory Council (NDWAC) on the process that should be
used to identify contaminants for inclusion on CCL 1. For chemical contaminants, the Agency
developed screening and evaluation criteria based on recommendations from NDWAC. For
microbiological contaminants, NDWAC recommended that the Agency seek external expertise
to identify and select potential waterborne pathogens. As a result, the Agency convened an
international panel of microbiologists and public health experts who developed criteria for
screening and evaluation and subsequently developed an initial list of potential microbiological
contaminants.
With the short time frame required, the first CCL was largely based on expert knowledge
and the evaluation of readily available information. EPA obtained beneficial input from the
NDWAC, the scientific community, and the public through stakeholder meetings and the public
comments received on the draft CCL 1 published on October 6, 1997 (62 FR 52193; USEPA,
1997). EPA published the final CCL 1, which contained 50 chemical and 10 microbiological
contaminants, on March 2, 1998 (63 FR 10273; USEPA, 1998). A more detailed discussion of
how EPA developed CCL 1 can be found in the 1997 and the 1998 Federal Register notices (62
FR 52193; USEPA 1997 and 63 FR 10273; USEPA 1998).
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1.2.3 The First Regulatory Determination (RD 1) for CCL 1
EPA published its preliminary regulatory determinations for a subset of contaminants
listed on CCL 1 on June 3, 2002 (67 FR 38222; USEPA, 2002). The Agency published its final
regulatory determinations on July 18, 2003 (68 FR 42898; USEPA, 2003). EPA identified nine
contaminants from the 60 contaminants listed on CCL 1 that had sufficient data and information
available to make regulatory determinations. The nine contaminants werq Acanthamoeba, aldrin,
dieldrin, hexachlorobutadiene, manganese, metribuzin, naphthalene, sodium, and sulfate. The
Agency determined that a NPDWR was not necessary for any of these nine contaminants. The
Agency did, however, issue guidance on Acanthamoeba and health advisories for manganese,
sodium, and sulfate.
The decision-making process that EPA used to make its regulatory determinations for
CCL 1 was based on substantial expert input and recommendations from different groups
including stakeholders, the National Research Council (NRC), and NDWAC. In March 2000,
EPA convened a Working Group under NDWAC to help develop an approach for making
regulatory determinations. The Working Group developed a protocol for analyzing and
presenting the available scientific data and recommended methods to identify and document the
rationale supporting a regulatory determination decision. The Working Group developed
separate but similar protocols for microorganisms and chemicals. The approach for chemicals
was based on an assessment of the impact of acute, chronic, and lifetime exposures, as well as a
risk assessment that includes evaluation of occurrence, fate, and dose-response. The NDWAC
protocol for chemicals provided a semi-quantitative, systematic approach for addressing each of
the three Regulatory Determination criteria. The NDWAC Working Group report was presented
to and accepted by the entire NDWAC in July 2000. In June 2002, EPA consulted with the SAB
Drinking Water Committee and requested its review and comment on whether the protocol EPA
developed, based on the NDWAC recommendations, was consistently applied and appropriately
documented. SAB provided verbal feedback regarding the use of the NRC and NDWAC
recommendations in EPA's decision criteria for making its regulatory determinations. SAB
recommended that the Agency provide a transparent and clear explanation of the process for
making regulatory determinations. The Agency took SAB's recommendation into consideration
and further explained the regulatory determination evaluation process in the 2003 Federal
Register notice (68 FR 42898; USEPA, 2003) and in the supporting documentation.
1.2.4 The Second Contaminant Candidate List (CCL 2)
The process used to identify contaminants for inclusion on CCL was improved after
CCL 1. To develop an enhanced, more robust approach to evaluating the risk of potential
drinking water contaminants for future CCLs, the Agency requested assistance from the NRC.
The NRC's evaluation, and other parallel assessments, overlapped with the deadline
requirements to produce CCL 2. Hence, while EPA was developing the more rigorous process,
CCL 2 was based on the process used for CCL 1, and reflected the changes related to RD 1. The
CCL 2 carried forward the 51 chemical and microbial contaminants remaining on CCL 1 after
RD 1. The Agency published its draft CCL 2 Federal Register notice on April 2, 2004 (69 FR
17406; USEPA, 2004) and the final CCL 2 Federal Register notice on February 24, 2005 (70 FR
9071; USEPA, 2005).
1.2.5 The Second Regulatory Determination (RD 2) for CCL 2
Continuing to follow the process established under RD 1, the Agency published its
preliminary regulatory determinations for contaminants listed on CCL 2 on May 1, 2007 (72 FR
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24106; USEPA, 2007). In the May 1, 2007 notice, EPA made preliminary determinations for 11
of the 51 contaminants listed on the CCL 2. These contaminants were: boron, the dacthal mono-
and di-acid degradates, l,l-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE),
1,3-dichloropropene, 2,4-dinitrotoluene, 2,6-dinitrotoluene, »Y-ethyl dipropylthiocarbamate
(EPTC), fonofos, terbacil, and 1,1,2,2-tetrachloroethane. The Agency determined that an
NPDWR was not necessary for any of these 11 contaminants. EPA finalized those regulatory
determinations on CCL 2 on July 30, 2008 (73 FR 44251; USEPA, 2008a).
1.2.6 The Third Contaminant Candidate List (CCL 3)
As noted above, after CCL 1, the Agency realized the need to develop an enhanced
approach to evaluate the risk of potential drinking water contaminants based on occurrence in
drinking water and adverse health effects - both demonstrated and potential - for future CCLs.
The Agency requested assistance from the NRC for guidance on methods and processes to
identify and narrow a universe of potential contaminants into a smaller, more focused list of
contaminants in drinking water for the future CCLs. The NRC recommended a multi-step
process including using prototype classification algorithms that evaluate attributes in conjunction
with expert judgment to identify contaminants for future CCLs. The approach would be based on
predictive features or attributes that characterize the occurrence in drinking water and health
effects of each contaminant. The NRC described two health effects attributes, severity and
potency, and three occurrence attributes: prevalence, magnitude, and persistence/mobility.
The details of the NRC recommendation are available in the report entitled Classifying
Drinking Water Contaminants for Regulatory Considerations (NRC, 2001). It is important to
emphasize that the NRC report only gives a broad framework for EPA to develop its own
prototype classification scheme and then to calibrate the scheme using diagnostic contaminants.
Following up on the NRC recommendations, EPA requested that the NDWAC provide
advice on whether to pursue the stepped approach recommended in the NRC report and on how
it could be implemented. The NDWAC formed a subcommittee, the Work Group on the
Contaminant Candidate List Classification Process (CCLCP Work Group), to provide advice to
the NDWAC.
Based on the deliberations of the CCLCP Work Group, the NDWAC released a report in
June 2004 that found merit in the NRC recommendations, but noted that EPA may need several
CCL cycles to fully develop and implement the NRC recommended approach. While the
NDWAC agreed with the overall approach, the group noted that not all the data and information
needed to fully develop the NRC-envisioned CCL were available at the time. The NDWAC also
recognized that the Agency would be developing a new and powerful tool that could be refined
and improved in successive efforts. Therefore, the NDWAC recommended that the Agency take
advantage of the knowledge gained in implementing the approach and improve upon it in
subsequent CCLs using an adaptive management process.
Based on these consultations with expert groups and stakeholders, EPA developed a
systematic approach to select contaminants for CCL 3 that includes the following key steps:
(1) The identification of a broad universe of potential drinking water contaminants
(CCL 3 Universe);
(2) A screening process that uses readily available information on health effects and
occurrence in water to narrow that universe of contaminants to a Preliminary CCL
(PCCL); and
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(3) A structured classification process that "scores" and ranks contaminants, to develop a
CCL from the PCCL, involving prototype classification models as tools, coupled
with expert review and assessment.
New and emerging agents can enter the process at multiple points based on surveillance and
nomination. Exhibit 1-1 illustrates the process used to evaluate contaminants for CCL 3.
Exhibit 1-1: General Overview of the Approach Used to Establish CCL 3
STEP 1
Identify the
Universe
STEP 2
Screen
to a PCCL
STEP 3
Select the CCL
Universe
¦L
PCCL
Classification
Tools
Evaluation
Expert Review
1
r
Proposed CCL
K
r
| Final CCL |
V-J
Surveillance
and
Nomination
,
Chemical and microbial contaminants were evaluated separately. To populate the CCL 3
Universe of chemicals, an extensive preliminary list of substances was compiled from a wide
variety of data sources that met specific criteria. The preliminary list was refined by removing
chemicals with an existing NPDWR, substances that are considered mixtures of chemicals, and
"non-chemically defined" entries. The resultant CCL 3 Universe included approximately 6,000
chemicals (see USEPA, 2009a for further details on the CCL 3 Universe process).
The CCL 3 Universe of chemicals was then screened using a framework that took into
account both health effects and occurrence data. In the case of health effects, EPA evaluated both
quantitative and qualitative information on the hazard and/or dose-response properties of the
contaminants. For occurrence, EPA evaluated both quantitative and qualitative information on
occurrence in water, releases to the environment, and amounts produced. The result of this
screening process was that 561 chemical contaminants were selected for the Preliminary CCL 3
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(PCCL 3) from the approximately 6,000 chemicals in the CCL 3 Universe (see USEPA, 2009b
for details on the screening process).
To select contaminants for the CCL 3 from among the 561 PCCL 3 contaminants, EPA
used classification models as a support tool to handle larger, more complex assortments of data
in a consistent and reproducible manner. The classification models were trained based on past
expert decisions for a sample of chemicals. To enable numerical scoring of the contaminants,
using complex data, a scaling system was developed for four attributes: severity, potency,
magnitude, and prevalence (see USEPA, 2009c for details). Contaminants were scored for each
of these attributes, and the scores were run through three calibrated models. The EPA Evaluation
Team made several post-model refinements to compile the draft list of CCL 3 chemical
contaminants.
The protocol EPA used to select the microbial contaminants for the CCL 3, as described
in detail in the draft CCL 3 notice (73 FR 9628; USEPA, 2008b), followed the same general
outline. The first step was to identify a universe of potential microbial drinking water
contaminants. The second step was to screen that universe of microbiological contaminants to
develop a Preliminary Contaminant Candidate List (PCCL). Lastly, EPA selected the draft
CCL 3 microbial list by ranking the PCCL contaminants based on occurrence in drinking water
(including consideration of waterborne disease outbreaks) and human health effects.
EPA also put out a special call for nominations to the CCL 3 (USEPA, 2009d), held
expert panel consultations, consulted with the SAB, and accepted public comments (USEPA,
2009e). The draft CCL 3 was published on February 21, 2008 (73 FR 9628; USEPA, 2008b), and
the final CCL 3 was published on October 8, 2009 (74 FR 51850; USEPA, 2009f). The final
CCL 3 consisted of 104 chemicals or chemical groups, and 12 microbiological contaminants.
1.2.7 The Third Regulatory Determination (RD 3) for CCL 3
The Agency published its preliminary regulatory determinations for contaminants listed
on the CCL 3 Federal Register notice on October 20, 2014 (79 FR 62716; USEPA, 2014a). In
that notice, EPA made preliminary determinations for 5 of the 116 contaminants listed on the
CCL 3. A preliminary positive determination was made for strontium. Preliminary negative
determinations were made for dimethoate, 1,3-dinitrobenzene, terbufos, and terbufos sulfone.
EPA also announced in that notice that decisions about whether or not to regulate the
contaminants chlorate, N-nitrosodibutylamine (NDBA), N-nitrosodimethylamine (NDMA), N-
nitrosodipropylamine (NDPA), N-nitrosodiethylamine (NDEA), N-nitrosomethylethylamine
(NMEA), and N-pyrrolidine (NPYR) would not be made under Regulatory Determinations 3 but
rather as part of the Six-Year Review of existing Microbial / Disinfection By-Product (MDBP)
regulations. On January 4, 2016 (81 FR 13; USEPA, 2016a), EPA finalized the negative
determinations for dimethoate, 1,3-dinitrobenzene, terbufos, and terbufos sulfone. EPA
announced a delay in issuing a final regulatory determination on strontium in order to consider
additional data.
The RD 3 process was formalized in a protocol document that was reviewed by an expert
panel in October 2011, and revised in response to reviewer suggestions (USEPA, 2014b). The
RD 3 Protocol captures the process that had been used for Regulatory Determinations 1, 2, and 3
in accordance withNDWAC recommendations discussed in section 1.2.3.
In the Federal Register notice for the RD 2 preliminary determinations (72 FR 24106;
USEPA, 2007), EPA presented an update on the Agency's evaluation of perchlorate and solicited
public comment on the information and options for perchlorate. EPA published an off-cycle
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determination to regulate perchlorate on February 11, 2011 (76 FR 7762; USEPA, 2011); this
final regulatory determination for perchlorate was considered part of the third Regulatory
Determination cycle. Subsequently, after evaluating additional information, EPA withdrew the
determination to regulate perchlorate (85 FR 43990; USEPA, 2020a). Additional information
about the perchlorate determination can be found in that notice and on EPA's website:
https://www.epa.gov/dwstandardsregulations/perchlorate-drinking-water.
1.3 The Fourth Contaminant Candidate List (CCL 4)
The draft CCL 4 was published on February 4, 2015 (80 FR 6076; USEPA, 2015) and the
final CCL 4 was published on November 17, 2016 (81 FR 81099; USEPA, 2016b). The final
CCL 4 consists of 97 chemicals or chemical groups and 12 microbiological contaminants. Most
CCL 4 contaminants were carried over from CCL 3 (which, as described above, was developed
according to a rigorous process with input from multiple stakeholders over the course of multiple
years). EPA added two contaminants (manganese and nonylphenol) to the CCL 4 list based on
nominations. EPA struck from the list those CCL 3 contaminants that had been subject to recent
preliminary and/or final regulatory determinations (perchlorate, dimethoate, 1,3-dinitrobenzene,
terbufos, terbufos sulfone, strontium) and three pesticides with cancelled registrations
(disulfoton, fenamiphos, molinate).
1.4 Overview of the Fourth Regulatory Determination (RD 4) for CCL 4
The Regulatory Determinations 4 process is very similar to that used for RD 3 and in
earlier rounds of regulatory determinations. The three-phase process is described in detail in the
RD 4 protocol presented in Appendix E. The procedure is briefly described below, along with
outcomes.
1.4.1 RD 4 Phase 1: Data Availability
In the first phase, EPA evaluates data availability, including: (a) the availability of a
suitable health assessment, from which a critical health effect can be identified and a Health
Reference Level (HRL) calculated,1 (b) the availability of nationally representative finished
water occurrence data, and (c) the existence of a widely available analytical method for detecting
the contaminant in drinking water.
The list of contaminants evaluated included all 109 CCL 4 contaminants, plus 4-
androstene-3,17-dione, and testosterone. EPA announced a delay in issuing a final regulatory
determination on strontium during Regulatory Determination 3 in order to consider additional
data. EPA continues to evaluate strontium at this time. 4-Androstene-3,17-dione and testosterone
are contaminants that were monitored under the third Unregulated Contaminant Monitoring Rule
(UCMR 3).
As indicated in Exhibit 1-2, EPA found that 25 CCL 4 contaminants met the data
availability criteria. These contaminants proceeded to the second phase of the RD 4 process and
are referred to as the "short list."
1 An HRL is a health-based concentration against which the Agency evaluates occurrence data when making
decisions about regulatory determinations.
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Exhibit 1-2: Contaminants Proceeding from Phase 1 to Phase 2
CASRN
Common Name
Best Health Effects
Data Source
Best Occurrence
Data Source
Occurrence Data
Type
630-20-6
1,1,1,2-Tetrachloroethane
IRIS 1989
UCM
National DW
75-34-3
1,1-Dichloroethane
PPRTV 2006
UCMR 3 (AM)
National DW
96-18-4
1,2,3-Trichloropropane
IRIS 2009
UCMR 3 (AM)
National DW
123-91-1
1,4-Dioxane
IRIS 2010 for RfD;
2013 for CSF
UCMR 3 (AM)
National DW
30560-19-1
Ace p hate
OPP HHRA 2018
State data
Non-National DW
34256-82-1
Acetochlor
OPP HHRA 2018
UCMR 2 (SS)
National DW
319-84-6
alpha-
Hexachlorocyclohexane
IRIS 1987
State data
Non-National DW
62-53-3
Aniline
PPRTV 2007 for RfD;
IRIS 1988 for CSF
State data
Non-National DW
14866-68-3
Chlorate
OPP HHRA 2016
UCMR 3 (AM)
National DW
7440-48-4
Cobalt
PPRTV 2008
UCMR 3 (AM)
National DW
NA
Cyanotoxins
OW HA 2015
Supplemental
Non-National DW
NA
Legionella pneumophila
NA
Misc
Non-National DW
7439-96-5
Manganese
OW HA 2004
NIRS
National DW
74-83-9
Methyl bromide
(Bromomethane)
OPP HHRA 2006
UCMR 3 (AM)
National DW
51218-45-2
Metolachlor
OPP HHRA 2018
UCMR 2 (SS)
National DW
7439-98-7
Molybdenum
IRIS 1992
UCMR 3 (AM)
National DW
98-95-3
Nitrobenzene
IRIS 2009
UCMR 1 (AM)
National DW
55-18-5
N-Nitrosodiethylamine
(NDEA)
OW Six Year Review 3
Technical Support
Document 2016
UCMR 2 (SS)
National DW
62-75-9
N-Nitrosodimethylamine
(NDMA)
OW Six Year Review 3
Technical Support
Document 2016
UCMR 2 (SS)
National DW
621-64-7
N-Nitroso-di-n-
propylamine (NDPA)
OW Six Year Review 3
Technical Support
Document 2016
UCMR 2 (SS)
National DW
930-55-2
N-Nitrosopyrrolidine
(NPYR)
OW Six Year Review 3
Technical Support
Document 2016
UCMR 2 (SS)
National DW
1763-23-1
Perfluorooctanesulfonic
acid (PFOS)
OW HA 2016
UCMR 3 (AM)
National DW
335-67-1
Perfluorooctanoic acid
(PFOA)
OW HA 2016
UCMR 3 (AM)
National DW
121-82-4
RDX
IRIS 2018
UCMR 2 (AM)
National DW
7440-62-2
Vanadium
PPRTV 2009
UCMR 3 (AM)
National DW
Note: Chapter 2 provides a general overview of the sources of data that EPA used to evaluate drinking
water contaminants, including sources of health effects and occurrence data.
AM = Assessment Monitoring
CSF = Cancer Slope Factor
DW = Drinking Water
HA = Health Advisory
HHRA = Human Health Risk Assessment
IRIS = Integrated Risk Information System
NA = Not Applicable
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NIRS = National Inorganics and Radionuclides Survey
OPP = Office of Pesticide Programs
OW = Office of Water
PPRTV = Provisional Peer-Reviewed Toxicity Value
RfD = Reference Dose
SS = Screening Survey
UCM = Unregulated Contaminant Monitoring
UCMR 1 = First Unregulated Contaminant Monitoring Rule
UCMR 2 = Second Unregulated Contaminant Monitoring Rule
UCMR 3 = Third Unregulated Contaminant Monitoring Rule
For the remaining contaminants, Exhibit 1-3 summarizes why each did not proceed to the
second phase of the RD 4 process.
Exhibit 1-3: Contaminants Not Proceeding from Phase 1 to Phase 2
Has nationally representative finished water data but no health assessment
1,3-Butadiene
Ethinyl Estradiol (17-alpha ethynyl estradiol)
3-Hydroxycarbofuran
Germanium
4-Androstene-3,17-dione
Halon 1011 (bromochloromethane)
Acetochlor ethanesulfonic acid (ESA)
HCFC-22
Acetochlor oxanilic acid (OA)
Methyl tert-butyl ether
Alachlor ethanesulfonic acid (ESA)
Metolachlor ethanesulfonic acid (ESA)
Alachlor oxanilic acid (OA)
Metolachlor oxanilic acid (OA)
Chloromethane (Methyl chloride)
n-Propylbenzene
Equilin
sec-Butylbenzene
Estradiol (17-beta estradiol)
Tellurium
Estriol
Testosterone
Estrone
Has available or in process health assessment and other finished drinking water data but no occurrence at
levels > 1/2 RD 4 HRL
1-Butanol
Methamidophos
Acrolein
Methanol
Bensulide
N-Nitrosodiphenylamine (NDPhA)*
Benzyl chloride
Oxydemeton-methyl
Captan
Oxyfluorfen
Dicrotophos
Permethrin
Diuron
Profenofos
Ethoprop
Tebuconazole
Ethylene glycol
Tribufos
Ethylene thiourea (Maneb 12427382)
Vinclozolin
Formaldehyde
Ziram
Has other finished drinking water data but no health assessment
17alpha-estradiol
Erythromycin
Acetaldehyde
Hexane
Adenovirus*
Mestranol
Butylated hydroxyanisole
Mycobacterium avium*
Calicivi ruses*
Naeqleria fowleri*
Enterovirus*
Nonylphenol
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Equilenin |Norethindrone (19-Norethisterone)
Does not have nationally representative or other finished water data
2-Methoxyethanol
N-Methyl-2-pyrrolidone
2-Propen-1-ol
o-Toluidine
4,4'-Methylenedianiline
Oxirane, methyl-
Acetamide
Quinoline
Campylobacter jejuni
Salmonella enterica
Clethodim
Shigella sonnei
Cumene hydroperoxide
Tebufenozide
Dimethipin
Thiodicarb
Escherichia coli (0157)
Thiophanate-methyl
Ethylene oxide
Toluene diisocyanate
Helicobacter pylori
Triethylamine
Hepatitis A virus
Triphenyltin hydroxide (TPTH)
Hydrazine
Urethane
Nitroglycerin
"Does not have a widely available analytical method for occurrence monitoring
1.4.2 RD 4 Phase 2: Data Evaluation
In the second phase, EPA gathers and evaluates the full range of relevant data available
for "short list" contaminants. Occurrence data (both finished water and ambient water data) are
analyzed against the HRL threshold. Outcomes of the data evaluation include:
(1) Identifying contaminants occurring or likely to occur at levels and frequencies of
public health concern.
(2) Identifying contaminants that have no or low potential for public health concern and
no data gaps.
Those in the first group are candidates for a positive determination in Phase 3. Those in
the second group are candidates for a negative determination in Phase 3. Exhibit 1-4 lists the
contaminants that proceed from Phase 2 to Phase 3. Exhibit 1-5 summarizes the outcomes for
contaminants that do not proceed from Phase 2 to Phase 3.
Exhibit 1-4: Contaminants Proceeding from Phase 2 to Phase 3
1,1-Dichloroethane
Metolachlor
1,4-Dioxane
Nitrobenzene
1,2,3-Trichloropropane
PFOA
Acetochlor
PFOS
Methyl Bromide
RDX
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Exhibit 1-5: Data and Rationale Summary for the 15 Contaminants Not
Proceeding from Phase 2 to Phase 3
#
Contaminant
Health Data
Available
Occurrence Data
Available
Rationale
1
1,1,1,2-
Tetrachloroethane
Yes
Yes
Health data gap (a review of the current literature
is needed to decide if an update to the 1987 IRIS
health assessment is warranted)
2
Ace p hate
Yes
No
Occurrence data gaps (no nationally
representative finished water data
or sufficient other finished water data)
3
alpha-
Hexachlorocyclohexane
Yes
No
Occurrence data gaps (no nationally
representative finished water data
or sufficient other finished water data)
4
Aniline
Yes
No
Occurrence data gaps (no nationally
representative finished water data
or sufficient other finished water data)
5
Chlorate
Will be evaluated and considered as part of
the review of the existing Disinfectants /
Disinfection Byproducts (D/DBP) rules. [11 [2]
6
Cobalt
Yes
Yes
Health data gap (updated
health assessment needed to consider new
subchronic and developmental studies)
7
Cyanotoxins
Yes
No
Health advisories available for some specific
cyanotoxins (microcystins and
cylindrospermopsin); occurrence data gaps
(insufficient nationally representative finished
water data or other finished water data). Certain
cyanotoxins are being monitored under the fourth
Unregulated Contaminant Monitoring Rule
(UCMR 4) but final UCMR 4 data will not be
complete in time for a determination under
RD 4.
8
Legionella pneumophila
Yes
No
Maximum Contaminant Level Goal (MCLG)
available; occurrence data gaps (no nationally
representative finished water data
or sufficient other finished water data). Will be
evaluated and considered as part of the review
of the existing Surface Water Treatment Rules.
[21
9
Manganese
No
No
Health and occurrence data gaps (updated
health assessment [3] not completed by RD 4
cutoff date). Manganese is being monitored for
under UCMR 4 but final UCMR 4 data will not be
complete in time for a determination under
RD 4.
10
Molybdenum
No
Yes
Health data gap (updated assessment needed to
consider multiple new studies).
11
N-Nitrosodiethylamine
(NDEA)
Will be evaluated and considered as part of
the review of the existing D/DBP rules.[11
12
N-Nitrosodimethylamine
(NDMA)
Will be evaluated and considered as part of
the review of the existing D/DBP rules.[11
13
N-Nitroso-di-n-
propylamine (NDPA)
Will be evaluated and considered as part of
the review of the existing D/DBP rules. [11
14
N-Nitrosopyrrolidine
(NPYR)
Will be evaluated and considered as part of
the review of the existing D/DBP rules. [11
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#
Contaminant
Health Data
Available
Occurrence Data
Available
Rationale
15
Vanadium
Yes
Yes
Health data gap; undergoing assessment by
EPA IRIS:
https://www.epa.gov/sites/production/files/2019-
04/documents/iris program outlook apr2019.pdf
1] Under RD 3 (79 FR 62716), EPA noted that disinfection byproducts (DBPs) need to be evaluated collectively,
because the potential exists that the treatment used to control a specific DBP could affect the concentrations of other
DBPs and potentially microorganisms.
[2] Under the Six-Year Review 3 (82 FR 3518, USEPA, 2016c), the Agency completed a detailed review of 76
NPDWRs and determined that eight NPDWRs were candidates for regulatory revision. The eight NPDWRs are
included in the Stage 1 and the Stage 2 Disinfectants and Disinfection Byproducts Rules, the Surface Water
Treatment Rule, the Interim Enhanced Surface Water Treatment Rule and the Long Term 1 Enhanced Surface Water
Treatment Rule.
[3] Health Canada finalized their Manganese Guideline for Canadian Drinking Water Quality in June 2019. The
Guideline summarizes new health effects information published since EPA's manganese health assessment in 2004
(https://www.canada.ca/content/dam/hc-sc/documents/services/publications/healthy-living/guidelines-canadian-
drinking-water-quality-guideline-technical-document-manganese/pub-manganese-0212-2019-eng.pdf)
1.4.3 RD 4 Phase 3: Regulatory Determination Assessment
In the third and final phase, the Agency assesses contaminants that have reached this
point against the three statutory criteria listed in section 1.2.1 above. Additional detail on how
the statutory criteria are interpreted and applied is found in the Regulatory Determination 4
protocol in Appendix E.
Outcomes of the regulatory determination assessment can include a determination to
regulate, a determination not to regulate, or a decision to make no determination (for example: if
additional data-gathering is warranted, or if a contaminant will be evaluated as a candidate for
regulation as part of a different program or on a different schedule).
As the outcome of Phase 3, EPA is making a determination to regulate two of the
contaminants (PFOS and PFOA) and to not regulate six others (1,1-dichloroethane, acetochlor,
methyl bromide, metolachlor, nitrobenzene, and RDX). These eight contaminants are the subject
of chapters 3-10 of this support document. EPA is making no determination about the remaining
two contaminants, 1,4-dioxane and 1,2,3-trichloropropane. Information about these two
contaminants is presented in Appendices B and C. RD 4 Phase 3 outcomes are presented
formally in the Federal Register.
The final determinations were made following publication of preliminary determinations
(USEPA, 2020b) and consideration of public comments. Following the publication of the final
positive determinations for PFOS and PFOA, EPA has 24 months to publish a proposed MCLG
and NPDWR. After the proposal, the Agency has 18 months (which can be extended by an
additional 9 months) to publish a final MCLG and promulgate a final NPDWR (SDWA section
1412(b)(1)(E)).
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1.5 References
National Research Council (NRC). 2001. Classifying Drinking Water Contaminants for
Regulatory Considerations. Committee on Drinking Water Contaminants, Water Science
and Technology Board, Board on Environmental Studies and Toxicology, National
Research Council. National Academies Press.
United States Environmental Protection Agency (USEPA). 1997. Announcement of the Draft
Drinking Water Contaminant Candidate List; Notice. Federal Register. Vol. 62, No. 193,
p. 52193. October 6, 1997.
USEPA. 1998. Announcement of the Drinking Water Contaminant Candidate List; Notice.
Federal Register. Vol. 63, No. 40, p. 10273. March 2, 1998.
USEPA. 2002. Announcement of Preliminary Regulatory Determinations for Priority
Contaminants on the Drinking Water Contaminant Candidate List. Federal Register. Vol.
67, No. 106, p. 38222. June 3, 2002.
USEPA. 2003. Announcement of Regulatory Determinations for Priority Contaminants on the
Drinking Water Contaminant Candidate List. Federal Register. Vol. 68, No. 138, p.
42898. July 18, 2003.
USEPA. 2004. Drinking Water Contaminant Candidate List 2; Notice. Federal Register. Vol. 69,
No. 64, p. 17406, April 2, 2004.
USEPA. 2005. Notice—Drinking Water Contaminant Candidate List 2; Final Notice. Federal
Register. Vol. 70, No. 36, p. 9071, February 24, 2005.
USEPA. 2007. Drinking Water: Regulatory Determinations Regarding Contaminants on the
Second Drinking Water Contaminant Candidate List—Preliminary Determinations;
Proposed Rule. Federal Register. Vol. 72, No. 83, p. 24016, May 1, 2007.
USEPA. 2008a. Drinking Water: Regulatory Determinations Regarding Contaminants on the
Second Drinking Water Contaminant Candidate List. Federal Register. Vol. 73, No. 147,
p. 44251, July 30, 2008.
USEPA. 2008b. Drinking Water Contaminant Candidate List 3—Draft Notice. Federal Register.
Vol, 73. No 35. p. 9628, February 21, 2008.
USEPA. 2009a. Final Contaminant Candidate List 3 Chemicals: Identifying the Universe. EPA
815-R-09-006. August 2009.
USEPA. 2009b. Final Contaminant Candidate List 3 Chemicals: Screening to a PCCL. EPA
815-R-09-007. August 2009.
USEPA. 2009c. Final Contaminant Candidate List 3 Chemicals: Classification of PCCL to the
CCL. EPA 815-R-09-008. August 2009.
USEPA. 2009d. Summary of Nominations for the Third Contaminant Candidate List. EPA-815-
R-09-011. August 2009.
USEPA. 2009e. Final Comment Response Document for the Third Drinking Water Contaminant
Candidate List 3 Categorized Public Comments. EPA 815-R-09-010. August 2009.
USEPA. 2009f. Drinking Water Contaminant Candidate List 3-Final. Federal Register. Vol. 74,
No. 194, p. 51850, October 8, 2009.
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USEPA. 2011. Drinking Water: Regulatory Determination on Perchlorate. Federal Register.
Vol. 76, No. 29, p. 7762, February 11, 2011. Available on the Internet at:
https ://federalregister. gov/a/2011 -2603
USEPA. 2014b. Protocol for the Regulatory Determinations 3. Including Appendices A-F. EPA-
815-R-14-005. April 2014.
USEPA 2014a. Announcement of Preliminary Regulatory Determinations for Contaminants on
the Third Drinking Water Contaminant Candidate List. Federal Register. Vol. 79, No.
202, p. 62716.
USEPA. 2015. Drinking Water Contaminant Candidate List 4—Draft. Federal Register. Vol. 80
No. 23, p. 6076, February 4, 2015.
USEPA. 2016a. Announcement of Final Regulatory Determinations for Contaminants on the
Third Drinking Water Contaminant Candidate List. Federal Register. Vol. 81 No. 1, p.
13, January 4, 2016.
USEPA. 2016b. Drinking Water Contaminant Candidate List 4—Final. Federal Register. Vol.
81 No. 222, p. 81099, November 17, 2016.
USEPA. 2020a. Drinking Water: Final Action on Perchlorate. Federal Register. Vol. 85 No. 140,
p. 43990, July 21, 2020.
USEPA. 2020b. Announcement of Preliminary Regulatory Determinations for Contaminants on
the Fourth Drinking Water Contaminant Candidate List. Federal Register. Vol. 85 No.
47, p. 14098, March 10, 2020.
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Chapter 2:
Data Sources and Data Evaluation
A chapter from:
Final Regulatory Determination 4 Support Document
EPA Report 815-R-21-001
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Contents
Contents 2-2
Exhibits 2-3
Abbreviations 2-4
Chapter 2: Data Sources and Data Evaluation 2-7
2.1 Contaminant Background, Chemical, and Physical Properties 2-7
2.2 Contaminant Production, Use, and Release 2-7
2.3 Environmental Fate and Transport 2-11
2.4 Adverse Health Effects 2-14
2.4.1 EPA Health Assessments: 2-14
2.4.2 Non-EPA Health Assessments: 2-17
2.5 Contaminant Occurrence and Exposure 2-19
2.5.1 General Considerations 2-19
2.5.2 Occurrence in Ambient Water 2-21
2.5.3 Occurrence in Drinking Water - Primary Data Sources 2-25
2.5.4 Occurrence in Water - Secondary Data Sources 2-32
2.6 Analytical Methods 2-38
2.7 Treatment Technologies 2-39
2.8 References 2-39
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Exhibits
Exhibit 2-1: Chemical Volume Production (Including Importation) Ranges Used in IUR and
CDR Reporting 2-8
Exhibit 2-2: Persistence Scale 2-13
Exhibit 2-3: Mobility Scale 2-14
Exhibit 2-4: Cross-section States for UCM Round 1 and Round 2 2-31
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Abbreviations
AQUA
Automated Quantitative Usage Analysis
ATSDR
Agency for Toxic Substances and Disease Registry
AwwaRF
American Water Works Association Research Foundation
BF
Biodegrades Fast
BFA
Biodegrades Fast with Acclimation
BS
Biodegrades Slowly
BSA
Biodegrades Slowly with Acclimation
BST
Biodegrades Sometimes/Recalcitrant
CBI
Confidential Business Information
CCL
Contaminant Candidate List
CCL 3
Third Contaminant Candidate List
CCL 4
Fourth Contaminant Candidate List
CCR
Consumer Confidence Reports
CDC
Centers for Disease Control and Prevention
CDR
Chemical Data Reporting
CDW
Committee on Drinking Water
CUS
Chemical Update System
CWS
Community Water System
CWSS
Community Water System Survey
DBP
Disinfection Byproduct
DWTP
Drinking Water Treatment Plant
EPA
Environmental Protection Agency
EPCRA
Emergency Planning and Community Right-to-Know Act
EPI
Estimation Program Interface
EWG
Environmental Working Group
FIFRA
Federal Insecticide, Fungicide, and Rodenticide Act
FQPA
Food Quality Protection Act
GDWQ
Guidelines for Drinking-Water Quality
HA
Health Advisory
HBSL
Health-Based Screening Level
HC
Health Canada
HESD
Health Effects Support Document
HHRA
Human Health Risk Assessment
HRL
Health Reference Level
HSDB
Hazardous Substances Data Bank
ICR
Information Collection Request
IOC
Inorganic Compound
IRED
Interim Reregi strati on Eligibility Decision
IRIS
Integrated Risk Information System
IUR
Inventory Update Reporting
Kh
Henry's Law Constant
Koc
Organic Carbon Partitioning Coefficient
Kow
Octanol-Water Partitioning Coefficient
LCMRL
Lowest Concentration Minimum Reporting Level
MCL
Maximum Contaminant Level
MRL
Minimum Reporting Level
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MTBE
Methyl Tertiary Butyl Ether
NAWQA
National Water Quality Assessment
NCEA
National Center for Environmental Assessment
NCFAP
National Center for Food and Agricultural Policy
NCOD
National Drinking Water Contaminant Occurrence Database
NDWAC
National Drinking Water Advisory Council
NHANES
National Health and Nutrition Examination Survey
NIRS
National Inorganics and Radionuclides Survey
NPDWR
National Primary Drinking Water Regulation
NPL
National Priorities List
NPS
National Pesticide Survey
NREC
National Reconnaissance of Emerging Contaminants
NWIS
National Water Information System
OGWDW
Office of Ground Water and Drinking Water
OPP
Office of Pesticide Programs
ORD
Office of Research and Development
OW
Office of Water
PCCL
Preliminary Contaminant Candidate List
PDP
Pesticide Data Program
PFAS
Per- and Polyfluoroalkyl Substances
PFOA
Perfluorooctanoic Acid
PFOS
Perfluorooctanesulfonic Acid
PMP
Pilot Monitoring Program
PPRTV
Provisional Peer Reviewed Toxicity Value
PWS
Public Water System
QA
Quality Assurance
RD 4
Fourth Regulatory Determination
RED
Reregi strati on Eligibility Decision
RfC
Reference Concentration
RfD
Reference Dose
RSC
Relative Source Contribution
SDWA
Safe Drinking Water Act
SDWIS/Fed
Safe Drinking Water Information System/Federal Version
SOC
Synthetic Organic Compound
STEWARDS
Sustaining the Earth's Watersheds-Agricultural Research Data System
STORET
Storage and Retrieval Data System
SYR
Six-Year Review
SYR2
Second Six-Year Review
SYR3
Third Six-Year Review
TRED
Tolerance Reassessment Progress and Risk Management Decision
TRI
Toxics Release Inventory
TSCA
Toxic Substances Control Act
IT
Treatment Technique
UCM
Unregulated Contaminant Monitoring
UC MR
Unregulated Contaminant Monitoring Rule
UCMR 1
First Unregulated Contaminant Monitoring Rule
UCMR2
Second Unregulated Contaminant Monitoring Rule
UCMR 3
Third Unregulated Contaminant Monitoring Rule
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UCMR4
Fourth Unregulated Contaminant Monitoring Rule
USD A
United States Department of Agriculture
USGS
United States Geological Survey
USNLM
United States National Library of Medicine
uv
Ultraviolet
voc
Volatile Organic Compound
WHO
World Health Organization
WQP
Water Quality Portal
WQX
Water Quality Exchange
WRD
Water Resources Discipline
WRF
Water Research Foundation
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Chapter 2: Data Sources and Data Evaluation
This chapter provides a general overview of the sources of data that the Environmental
Protection Agency (EPA) used to evaluate drinking water contaminants under the fourth
Regulatory Determination (RD 4), based on the fourth Contaminant Candidate List (CCL 4), in
accordance with the requirements of the Safe Drinking Water Act (SDWA). The chapter includes
information about the quality of the data and about how EPA used the data. For more
information about the RD 4 process, see Chapter 1 of this report and the RD 4 protocol in
Appendix E. For an overview of RD 4 outcomes, see Chapter 1 of this report. For detailed
findings on individual contaminants receiving a final regulatory determination under RD 4, see
Chapters 3-10 of this report. For information about select contaminants not receiving a final
determination under RD 4, see Appendices A-C.
The outline of this chapter mirrors the organization of the contaminant-specific chapters
that follow. Section 2.1 identifies the sources used to gather contaminant background
information and chemical and physical properties. Section 2.2 describes information sources
used to characterize contaminant production, use, and release. Section 2.3 describes how
environmental fate and transport were evaluated and what information sources were used.
Section 2.4 describes the sources of information used for health effects evaluations, the process
of evaluating health effects information, and the use of carcinogenic and non-carcinogenic health
effects data for the derivation of a health reference level (HRL). Section 2.5 describes the
primary and supplemental sources of ambient and drinking water occurrence information used to
evaluate contaminant occurrence and exposure and provides information about occurrence data
handling (involving detection and reporting thresholds and rounding). Section 2.6 presents
information on evaluation of analytical methods, and Section 2.7 describes the processes used to
evaluate the availability of treatment technologies.
2.1 Contaminant Background, Chemical, and Physical Properties
EPA consulted a number of standard sources to gather information on contaminant
background and properties. These sources include the U.S. National Library of Medicine's
(USNLM) Hazardous Substances Data Bank (HSDB), Toxicity Profiles from the U.S. Agency
for Toxic Substances and Disease Registry (ATSDR), USNLM's ChemlDplus database, reports
regarding pesticide reregi strati on or registration review prepared by EPA's Office of Pesticide
Programs (OPP), and standard chemistry reference books. To fill some information gaps,
primary literature was consulted as well, with preference given to peer-reviewed sources.
2.2 Contaminant Production, Use, and Release
Quantitative data on natural and anthropogenic sources, including data on production,
use, and industrial releases, were obtained from specific primary sources and data compilations.
The most important of these are profiled in the following paragraphs.
Inventory Update Reporting (IUR) and Chemical Data Reporting (CDR) Program
The Toxic Substances Control Act (TSCA) requires EPA to compile, keep current, and
publish a Chemical Substance Inventory, a list of chemical substances that are manufactured or
processed in the United States. Following the promulgation of the 1986 Inventory Update
Reporting (IUR) rule, chemical manufacturers (including importers) were required to report to
EPA every four years the identity of and basic manufacturing information for organic chemical
substances manufactured (including imported) in quantities of 10,000 pounds or more annually
at individual sites. Modifications of the IUR rule in 2003 and 2005 expanded the range of
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chemicals and plant sites reporting, expanded the type of data reported, raised the production
volume threshold that triggers reporting from 10,000 pounds to 25,000 pounds, and made certain
further adjustments. Additional information on domestic processing and use was required to be
reported for chemicals produced or imported in amounts of 300,000 pounds or more at a single
site. In 2011 the Agency issued the Chemical Data Reporting (CDR) Rule, which replaced the
IUR Rule and established a somewhat modified program, including annual data gathering and
periodic reporting. CDR makes use of a two-tiered system of reporting thresholds, with 25,000
pounds the threshold for some contaminants and 2,500 pounds the threshold for others (USEPA,
2016a).
Data on production volumes submitted under IUR are housed in the Chemical Update
System (CUS). EPA makes certain non-confidential information available to the public. This
includes aggregated national total annual production volumes for chemicals based on reports
filed. As a result of the changes in reporting thresholds and other program modifications, the
results from 2006 onward might not be directly comparable to results from earlier years. The first
reporting year under the CDR Rule was 2011. As of the time of report preparation, the most
recent year of data available for analysis was 2015.
In making total annual national production volumes for chemicals available to the public,
the Agency assigned production volumes to bins. Eight production and importation volume
ranges were used under IUR. The ranges used for 2006 data differ slightly from those used for
earlier years. Under CDR the number of bins was expanded from 8 to 29. Exhibit 2-1 shows the
production and importation volume categories used for 1986-2002 data, 2006 data, and more
recent data.
If no reports were filed for a chemical in a particular year, the chemical is flagged as
having "no reports." If production quantities were withheld from publication by EPA so as not to
compromise companies' confidential business information (CBI), the quantities are flagged as
"withheld."
Exhibit 2-1: Chemical Volume Production (Including Importation) Ranges Used in
IUR and CDR Reporting
1986 -2002
2006
Post-20061
10,000 pounds - 500,000 pounds
<500,000 pounds
<25,000
>500,000 - 1 million pounds
500,000 to <1 million pounds
25,000 to 100,000
>1 million -10 million pounds
1 million to <10 million pounds
100,000 to 500,000
>10 million - 50 million pounds
10 million to <50 million pounds
500,000 to 1 million
>50 million -100 million pounds
50 million to <100 million pounds
1 million to 10 million
>100 million - 500 million pounds
100 million to <500 million
10 million to 50 million
> 500 million -1 billion pounds
500 million to <1 billion pounds
50 million to 100 million
Over 1 billion pounds
1 billion pounds or greater
100 million to 250 million
250 million to 500 million
500 million to 750 million
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1986 -2002
2006
Post-20061
750 million to 1 billion
1 billion to 5 billion
Sources: USEPA, 2012a.; USEPA 2016a
1CDR currently uses 29 bins for reporting volumes, including the 12 listed here and an additional 17 bins for
production quantities greater than 5 billion pounds. The additional 17 bins not shown in this table are not applicable to
RD 4 chemicals.
Several factors should be considered when interpreting production ranges assigned to
chemicals. Site-specific production volumes less than 10,000 pounds (25,000 pounds from 2006
on) were not reported and thus are not included in the totals. Production volume ranges for
reporting changed in 2006 and changed again in 2012. Furthermore, the data provide a snapshot
of annual production (including importation) only every four years through 2006, and therefore
do not capture fluctuation from year to year prior to initiation of the CDR in 2012.
Toxics Release Inventory (TRI)
EPA established the Toxics Release Inventory (TRI) in 1987 in response to Section 313
of the Emergency Planning and Community Right-to-Know Act (EPCRA). EPCRA section 313
requires facilities to report to both EPA and states annual information on toxic chemical releases
from facilities that meet reporting criteria. EPCRA section 313 also requires EPA to make this
information available to the public through a computer database. The database is accessible
through EPA's TRI Explorer. In 1990 Congress passed the Pollution Prevention Act, which
required that additional data on waste management and source reduction activities be reported
under TRI. The TRI database details not only the types and quantities of toxic chemicals released
to the air, water, and land by facilities, but also provides information on the quantities of
chemicals sent to other facilities for further management (USEPA, 2019a; USEPA, 2003a).
Facilities are required to report releases and other waste management activities related to
TRI chemicals if they manufacture, process, or otherwise use more than established threshold
quantities of these chemicals. Currently, for most chemicals, reporting of releases is required if
25,000 pounds or more of the chemical are manufactured or processed at a facility, or if 10,000
pounds or more are used at the facility. In 2000, special thresholds were added for persistent
bioaccumulative toxic chemicals such as dioxin and dioxin-like compounds (USEPA, 2019a). As
of 2017, when data were downloaded for RD 4, TRI included information on releases of
approximately 670 chemicals.
Although TRI can provide a general idea of release trends, these trends should be
interpreted with caution since reporting requirements have changed over time. For example, the
reporting threshold for the manufacturing and processing of TRI chemicals changed between
1987 and 1989, dropping from 75,000 pounds per year in 1987 to 50,000 in 1988 to the current
25,000 in 1989; this creates the potential for uncertainty in data trends over time (USEPA,
1999a). In addition, only those facilities that meet specific criteria are required to report to the
TRI program. For example, small facilities (those with fewer than 10 full-time employees and
those that do not exceed certain manufacture and use thresholds) are not required to report
releases. Finally, TRI data on releases cannot be used as a direct measure of general public
exposure to a chemical (USEPA, 2019a).
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Pesticide Usage Estimates from EPA's Office of Pesticide Programs (OPP) Reregistration
Documents
OPP sometimes presents estimates of annual U.S. usage of individual pesticides in its
pesticide reregistration documents (e.g., Reregistration Eligibility Decisions (REDs), Interim
Reregistration Eligibility Decisions (IREDs), Tolerance Reassessment Progress and Risk
Management Decisions (TREDs) or registration review documents (e.g., summary documents,
preliminary work plans and final work plans). For pesticides first registered prior to 1984, EPA
implemented the "reregistration" process to periodically evaluate the registration status of
pesticides. Pesticides that were first registered after 1984 are subject to the "registration review"
process. For several years, the older pesticides remained subject to the reregistration process
while the more recently registered pesticides were evaluated under registration review. Over the
past few years, EPA has moved all registered pesticides to the registration review process, which
involves an evaluation of whether the pesticide continues to meet the Federal Insecticide,
Fungicide, and Rodenticide Act (FIFRA) standard. Registration review is scheduled to be
performed at least every 15 years for registered pesticides. EPA no longer develops REDs to
accompany the reregistration process.
Many details of pesticide production and use are considered confidential business
information and are not publicly released. OPP relies on an Automated Quantitative Usage
Analysis (AQUA) program to automatically extract information about individual pesticides from
relevant Agency databases and calculate estimated total annual usage, among other figures (e.g.,
estimates of application rate, number of applications, and amount of crops treated). The estimate
of total usage represents an approximate maximum annual value. The likely maximum is
calculated using statistical procedures that set a usage level below which actual usage is expected
to fall 95 percent of the time (USEPA, 2000a). The values generated by AQUA are reviewed,
modified as necessary based on additional information not contained in the electronic databases,
and validated by comparison to other sources within and outside the Agency. The AQUA
methodology has been revised and refined over time since it was introduced in 1993 (USEPA,
2000a).
EPA Pesticide Industry Sales and Usage Report
EPA's OPP and Office of Chemical Safety and Pollution Prevention periodically issue
Pesticides Industry Sales and Usage reports. The reports provide contemporary and historical
information on U.S. pesticide production, imports, exports, usage, and sales, particularly with
respect to dollar values and quantities of active ingredient. The most recent report presents data
from 2012 (USEPA, 2017).
The data presented in EPA's Pesticide Industry Sales and Usage reports represent the best
information available to EPA from public and proprietary databases and market research reports
determined to meet the Agency's data quality standards. Publicly available data come from
OPP's Pesticide Data Center, and from a variety of other sources, including national data from
the United States Department of Agriculture (USDA). Proprietary data sources include widely
used commercial data compilations (USEPA, 2017).
Certain considerations apply when using or interpreting data presented in the Pesticide
Industry Sales and Usage reports. OPP cautions that "the numbers in the report represent
approximate values rather than precise values with known statistical properties" (USEPA, 2017).
In addition, OPP notes: "We caution the reader not to infer too much from changes in the amount
of pesticides used from year to year. Changes in the amount of pesticides used are not
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necessarily correlated to changes in the level of pest control or changes in the human health or
environmental risks associated with pesticide use" (USEPA, 2017).
National Center for Food and Agricultural Policy (NCFAP) Pesticide Use Database
The National Center for Food and Agricultural Policy (NCFAP), a private non-profit
institution, has assembled a national Pesticide Use Database. NCFAP annual pesticide use
estimates for circa 1992 and circa 1997 are based on state-level commercial agriculture usage
patterns for the periods 1990-1993 and 1995-1998, and state-level crop acreage for 1992 and
1997. The database contains estimates of pounds applied and acres treated in each state for 220
active ingredients and 87 crops. The majority of the chemicals monitored are herbicides, but the
database also follows significant numbers of fungicides and insecticides (NCFAP, 2000).
The NCFAP data are estimates and have several limitations. First, the database only
includes applications of pesticides to cropland (foliar, soil, and in furrow applications). Non-
cropland applications, such as uses for homes, greenhouses, livestock, ornamentals, or golf
courses are not included. The database does not include non-bearing orchards or vineyards, or
governmental Areawide Eradication programs. Second, in interpreting the NCFAP database, it
should be noted that records are compiled from a wide variety of sources. NCFAP states that
there is no way to determine the accuracy of any of the estimates in the database, adding that
some are based on surveys of farmers, while others are expert opinions from knowledgeable
extension service specialists. (As noted, the details of pesticide manufacture, sales, and use are
confidential business information.) When data for particular states and crops are unavailable, as
they are in many cases, values are assigned on the basis of data from a nearby state (NCFAP,
2000).
United States Geological Survey (USGS) Pesticide Use Maps
The United States Geological Survey (USGS, 2018) produces maps of annual usage for
several hundred pesticide active ingredients used in United States crop production. The pesticide
use maps show the average annual pesticide use intensity expressed as average weight (in
pounds) of a pesticide applied to each square mile of agricultural land in a county. The USGS
maps are created using data from proprietary surveys of farm operations, USD A Census of
Agriculture, and other sources.
USGS used two methods to estimate pesticide usage, since pesticide usage information
was not available in some districts. "EPest-High" estimates were generated by projecting usage
estimates for such districts based on usage in neighboring districts. "EPest-Low" estimates were
generated by assuming no usage in such districts.
USGS notes that the maps are suitable for making national, regional, and watershed
assessments of annual pesticide use, but that reliability of estimates generally decreases with
scale (USGS, 2018).
2.3 Environmental Fate and Transport
In the Environmental Fate section of each chapter, the initial discussion is focused on
available data in the literature regarding persistence and mobility. HSDB is typically used as the
primary source. Other sources consulted include ATSDR Toxicological Profiles, EPA pesticide
registration documents, and journal articles. Important parameters include the organic carbon
partitioning coefficient (Koc), the octanol-water partitioning coefficient (expressed as log Kow),
the Henry's Law constant (Kh), water solubility, vapor pressure, and half-life.
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Following this discussion of available data, qualitative conclusions about persistence and
mobility are drawn, as applicable, using Koc, log Kow, Kh, water solubility, and suitable half-lives
in the context of the persistence/mobility evaluation protocol. This protocol was originally
developed and used during the third Contaminant Candidate List (CCL 3) to score contaminants
on the Preliminary Contaminant Candidate List (PCCL) for the attribute Magnitude in cases
where only production data were available as a potential indicator of occurrence (USEPA,
2009a). It has been adapted for use in Regulatory Determinations. Use of the protocol helps to
ensure that generalizations about the persistence and mobility of compounds are made using
standardized scales. Below is a more detailed explanation of how qualitative conclusions about
persistence and mobility are drawn using the protocol.
Persistence
Persistence refers to the length of time a contaminant remains in the environment, or in a
particular medium like soil or water, when introduced. There are two primary mechanisms of
degradation that are of greatest importance in the Regulatory Determination process:
biodegradation and hydrolysis. Of primary importance is degradation in water. However, since
release of contaminants to soil can result in migration to surface water and/or groundwater (and
some contaminants, such as pesticides, are designed to be applied to crops and/or soil),
biodegradation in soil is also of importance. Chemical reactivity with soil organic matter may
also be important; however, data for this process are not common in sources such as HSDB.
Although other processes can result in either degradation of a contaminant (i.e.,
photolysis) or contaminant loss from an environmental system (i.e., volatilization), they are of
lesser importance in the context of drinking water. Photolysis can occur in surface water but not
in groundwater; therefore, photolytic degradation may not be applicable to all sources of
drinking water. Volatilization from soil or water to the atmosphere is a loss mechanism;
however, it is not a destructive loss mechanism. Thus, contaminants that volatilize can be re-
introduced to a given environmental medium through atmospheric deposition. Volatilization also
does not occur in surface water and in groundwater by identical mechanisms or at identical rates.
Values for photolysis and/or volatilization half-life are presented when available in HSDB;
however, only biodegradation, hydrolysis, and soil reactivity half-lives are assigned a qualitative
conclusion for persistence by processing them through the persistence/mobility ranking protocol.
Exhibit 2-2 summarizes the Persistence Scale in the form of derived numerical time
scales, qualitative biodegradation codes and their corresponding qualitative textual descriptions
(used for the CCL 3 process), and qualitative conclusions for persistence.
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Exhibit 2-2: Persistence Scale
A: Numerical Time Scale for Use
when Interpreting Literature
Values (for half-life)
B: Qualitative Code from
CCL 3 Modeling Using
BIODEG
C: Qualitative Conclusion
for Persistence
Hours-2 days
BF (Biodegrades fast)
Low persistence
>2 days-14 days
BFA (Biodegrades fast with
acclimation1)
Low persistence
>14 days-30 days
BS (Biodegrades slowly)
Moderate persistence
>30 days-59 days
BSA (Biodegrades slowly with
acclimation1)
Moderate persistence
>60 days
BST (Biodegrades
sometimes/recalcitrant)
High persistence
Source: Adapted from USEPA, 2009a
1 The term "acclimation" typically means that a contaminant does not begin to biodegrade until the requisite
microorganisms have become acclimated to the metabolism of a particular contaminant under a given set of
environmental conditions. Here, "acclimation" is used in a less specific manner (i.e., "Biodegrades fast with
acclimation" is a designation to indicate that biodegradation is not as rapid as "Biodegrades fast" but not as slow as
"Biodegrades slowly" and "Biodegrades slowly with acclimation" is a designation to indicate that biodegradation is not
as rapid as "Biodegrades slowly" but not as slow as "Biodegrades sometimes/recalcitrant").
The output of the persistence evaluation is shown in Column C. The preferred input is
measured or modeled half-lives from the literature (especially HSDB), evaluated against the
categories in Column A. The numerical time scale in Column A is applicable to a range of
degradation processes, including biodegradation, hydrolysis, and soil reactivity. If no numerical
values for degradation half-life that are broadly applicable to potential drinking water resources
are available from HSDB and other sources in the literature, the next preferred input to the
persistence evaluation is a qualitative biodegradation code (corresponding to one of the codes in
Column B), as derived by modeling performed during the development of CCL 3 using EPA's
BIODEG model.
If no qualitative biodegradation code from CCL 3 modeling is available, the BIOWIN
module of EPA's Estimation Program Interface (EPI Suite™ USEPA, 2012a) is used to provide
a qualitative estimate of persistence. The BIOWIN (v4.10) module of EPI Suite™ uses several
models to predict biodegradation, including complete degradation to a primary metabolite and
complete degradation to carbon dioxide and water. Although these predictions are not half-lives
and therefore cannot be directly compared to the categories for half-lives in the Persistence
Scale, an inference regarding persistence can often be made from the BIOWIN data relative to
the protocol's duration ranges for low, medium/moderate, and high persistence.
Mobility
Mobility refers to how readily a contaminant can partition from one environmental
medium to another. In the context of Contaminant Candidate List (CCL) and Regulatory
Determination, it is used specifically to refer to how readily a contaminant partitions to or
remains in water. That is, for CCL and in Regulatory Determination, the way that mobility
affects concentrations of a contaminant in water is of greatest importance. Exhibit 2-3
summarizes the Mobility Scale for data elements in the form of "bins" that establish cut-offs for
low, medium/moderate and high mobility rankings. A low ranking (Column B) minimizes the
resulting concentration in water while a high ranking (Column D) maximizes the resulting
concentration in water. Thus, those contaminants with a high ranking are of relatively greater
concern for their potential to occur in water than those with a low ranking. Note that depending
on how a parameter is defined, a large numerical value may result in either a low or a high
ranking, as explained in Column E of Exhibit 2-3. Since "mobility" can refer to the tendency to
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partition both into and out of water, textual descriptions of the results of these rankings are
presented not in terms of "high mobility" and "low mobility" but "high likelihood of partitioning
to water" and "low likelihood of partitioning to water."
Exhibit 2-3: Mobility Scale
A: Parameter
B: Low
Ranking
C: Medium/
Moderate
Ranking
D: High
Ranking
E: Effect on Water Concentration
Organic Carbon
Partitioning Coefficient
(Koc)
>1,000 mL/g
100-1,000
mL/g
<100 mL/g
Lower values for Koc (Column D) favor
dissolution in water over adsorption to
soil/sediment
Log Octanol/Water
Partitioning Coefficient
(log Kow)
>4
1-4
<1
Lower values for log Kow (Column D) favor
dissolution in water over adsorption to
soil/sediment or accumulation in animal tissue
Henry's Law Constant
(Kh)
>10-3 atm-
m3/mol
10"7-10"3 atm-
m3/mol
<10"7 atm-
m3/mol
Lower values for Kh (Column D) favor
dissolution in water over volatilization to air
Water Solubility
<1 mg/L
1-1,000 mg/L
>1,000 mg/L
Larger values for water solubility (Column D)
may favor higher water concentrations unless
sorption or volatility are more important
Source: Adapted from USEPA, 2009a
2.4 Adverse Health Effects
Health Assessments from a variety of both EPA and non-EPA sources were evaluated by
EPA for use in RD 4. The most important sources are profiled here.
2.4.1 EPA Health Assessments:
Integrated Risk Information System (IRIS)
(httvs://cfvub.eva.8Qv/ncea/iris drafts/'atoz.cfm?list type=alpha)
EPA's Integrated Risk Information System (IRIS) is a human health assessment program
that compiles and evaluates information on health effects that may result from exposure to
environmental contaminants. Through the IRIS Program, EPA provides the highest quality
science-based human health assessments to support the agency's regulatory activities. The IRIS
database contains information on more than 550 chemical substances containing information on
human health effects that may result from exposure to various substances in the environment.
The IRIS database is prepared and maintained by EPA's National Center for Environmental
Assessment (NCEA) within the Office of Research and Development (ORD).
The heart of the IRIS database is its collection of searchable documents that describe the
health effects of individual substances and that contain descriptive and quantitative information
in the following categories:
• Non-cancer effects: Oral reference doses and inhalation reference concentrations (RfDs
and RfCs, respectively) for effects known or assumed to be produced through a nonlinear
(possibly threshold) mode of action. In most instances, RfDs and RfCs are developed for
the noncarcinogenic effects of substances.
• Cancer effects: Descriptors that characterize the weight of evidence for human
carcinogenicity, oral slope factors, and oral and inhalation unit risks for carcinogenic
effects. Where a nonlinear mode of action is established, RfD and RfC values may be
used.
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Provisional Peer Reviewed Toxicity Value (PPRTV)
(httys://hhvvrtv. orttl. sov/auickview/pprtv papers, php)
A PPRTV is a toxicity value derived for use in the Superfund Program when such value
is not available in EPA's Integrated Risk Information System (IRIS, the first tier in the
Superfund hierarchy of human health toxicity values). PPRTVs are derived after a review of the
relevant scientific literature using the methods, sources of data, and guidance for value derivation
used by the EPA IRIS Program. All provisional peer-reviewed toxicity values receive internal
review by EPA scientists and external peer review by independent scientific experts. PPRTVs
differ in part from IRIS values in that PPRTVs do not receive the multi-program consensus
review provided for IRIS values. This is because IRIS values are generally intended to be used in
all EPA programs, while PPRTVs are developed specifically for the Superfund Program.
PPRTV assessments are eligible to be updated on a 5-year cycle to incorporate new data
or methodologies that might impact the toxicity values or characterization of potential for
adverse human health effects and are revised as appropriate. Questions regarding nomination of
chemicals for update can be sent to the appropriate EPA Superfund and Technology Liaison
(https://www.epa.gov/research/fact-sheets-regional-science). In general, the need for a PPRTV is
eliminated once an analogous IRIS value becomes available. Once IRIS values become
available, PPRTVs are removed from the PPRTV electronic library. It should also be noted that
sometimes available information is not sufficient to derive a PPRTV. Some PPRTV Derivation
Support Documents conclude that a PPRTV cannot be derived based upon the available
information.
Office of Pesticide Program's (OPP) REDs, IREDs, TREDs, HHRAs
(http://iaspub. epa. sov/apex/pesticides/f?p=chemicalsearch:l)
In 2008, EPA completed a review of older pesticides (those initially registered prior to
November 1984) under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) to
ensure that they met current scientific and regulatory standards. This process, called
reregi strati on, enabled EPA to call in and review supporting scientific studies, complete human
health and ecological risk assessments, and develop risk mitigation measures as needed using
current science, transparency, and input from stakeholders and the public. EPA also reassessed
existing tolerances (pesticide residue limits in food) to ensure that they met the safety standard
established by the Food Quality Protection Act (FQPA) of 1996. EPA integrated reregistration
and tolerance reassessment to most effectively accomplish the goals of both programs. When
EPA completes its review of a pesticide for reregi strati on or tolerance reassessment, the agency
issues a risk management decision document known as a RED, an IRED, or a TRED. EPA
publishes Notices of Availability in the Federal Register.
Reregistration Eligibility Decisions (REDs)
When EPA completes the review and risk management decision for a pesticide that is
subject to reregistration (that is, one initially registered before November 1984), the agency
generally issues a Reregistration Eligibility Decision or RED document. The RED summarizes
the risk assessment conclusions and outlines any risk reduction measures necessary for the
pesticide to continue to be registered in the U.S.
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Interim Reregistration Eligibility Decisions (IREDs)
EPA issues an IRED for a pesticide that is undergoing reregistration, requires a
reregistration eligibility decision, and also needs a cumulative assessment as a result of FQPA
because it is part of a group of pesticides that share a common mechanism of toxicity. The IRED,
issued after EPA completes the individual pesticide's aggregate risk assessment, may initiate risk
reduction measures—for example, reducing risks to workers or eliminating uses that the registrant
no longer wishes to maintain—to gain the benefits of these changes before the final RED can be
issued, following the agency's consideration of cumulative risks.
Reports on FQPA Tolerance Reassessment Progress and Risk Management Decisions
(TREDs)
EPA issues a TRED for a pesticide that requires tolerance reassessment decisions, but
does not require a reregistration eligibility decision at present because (a) the pesticide was
initially registered after November 1, 1984, and by law is not included within the scope of the
reregistration program; (b) EPA completed a RED for the pesticide before FQPA was enacted on
August 3, 1996; or (c) the pesticide is not registered for use in the U.S. but tolerances are
established that allow crops treated with the pesticide to be imported from other countries.
A TRED may be issued as a document if no changes in the tolerances for a pesticide are
required as a result of EPA's review. If tolerance revisions are required, then the TRED may be
issued as a Federal Register Notice. Like IREDs, some TREDs will not become final until EPA
considers the cumulative risks of all the pesticides in the cumulative group.
Human Health Risk Assessments (HHRAs)
(https://www.epa.siov/pesticide-science-and-assessinsi-pesticide-risks/overview-risk-
assessment-vesticide-yrosram#human health)
EPA issues a human health risk assessment (HHRA) for a pesticide when a pesticide is
undergoing registration, registration review, or a tolerance is being reviewed or established for a
new use (for more information on the tolerance reassessment process see:
https://www.epa.gov/sites/production/files/2015-08/documents/paper44.pdf). The HHRA
estimates the nature and probability of adverse health effects in humans who may be exposed to
chemicals in contaminated environmental media, now or in the future. HHRAs use the National
Research Council's four-step process for risk assessment: (a) hazard identification, (b) dose
response assessment, (c) exposure assessment, and (d) risk characterization. EPA uses HHRAs to
make informed decisions about approving new pesticides and new uses of registered pesticides,
and during our regular review of existing pesticides.
Office of Water (OW) Assessments:
(htty://water. eya. sov/drink/standards/hascience. cfm)
OW's health effects support documents (HESDs) address the exposure from drinking
water and other media, toxicokinetics, hazard identification, and dose-response assessment, for
chemicals known or anticipated to be found in drinking water. HESDs address the first two steps
of risk assessment process: hazard identification and dose response assessment. To prepare an
HESD, the agency performs a literature search for studies published after the most recent health
assessment (identified from the sources listed in Section 2.4) to determine if new information
suggests a different outcome. The agency collects and evaluates any peer-reviewed publications
identified through the literature search for their impact on the RfD and/or cancer assessment. The
HESDs are independently and externally peer-reviewed.
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Office of Water's health advisories (HAs) address the third and fourth steps of the risk
assessment process: exposure assessment and risk characterization. EPA develops HAs to
provide information on the chemical and physical properties, occurrence and exposure, health
effects, quantification of toxicological effects, other regulatory standards, analytical methods,
and treatment technology for drinking water contaminants. HAs describe concentrations of
drinking water contaminants at which adverse health effects are not anticipated to occur over
specific exposure durations (e.g., one-day, ten-days, and a lifetime). EPA's health advisories are
non-enforceable and non-regulatory and provide technical information to states agencies and
other public health officials on health effects, analytical methodologies, and treatment
technologies associated with drinking water contamination.
2.4.2 Non-EPA Health Assessments:
These non-EPA health assessments were recognized by the agency because of their
standardized methods for characterizing health effects data, relevancy to drinking water
exposures, and comparability to EPA methods.
Agency for Toxic Substances & Disease Registry (ATSDR)
(htty://www. atsdr. cdc. eov/az/a. html)
By Congressional mandate, the Agency for Toxic Substances and Disease Registry
(ATSDR) produces "toxicological profiles" for hazardous substances found at National Priorities
List (NPL) sites. These hazardous substances are ranked based on frequency of occurrence at
NPL sites, toxicity, and potential for human exposure. Toxicological profiles are developed from
a priority list of 275 substances. The ATSDR toxicological profile succinctly characterizes the
toxicological and adverse health effects information for hazardous substances. Each peer-
reviewed profile identifies and reviews the key literature that describes a hazardous substance's
toxicological properties. Other pertinent literature is also presented, but is described in less detail
than the key studies.
ATSDR establishes oral Minimal Risk Levels for non-neoplastic endpoints for acute (14
days or less), intermediate (15-364 days), and chronic (365 days or more) exposure durations.
Minimal Risk Levels for oral chronic exposure are similar to EPA's RfDs. However, ATSDR
and EPA use different approaches when the database is limited to subchronic studies and no
adequate chronic study is available. ATSDR derives an intermediate duration Minimal Risk
Level that protects against exposures up to 10 percent of a lifetime, and it does not incorporate an
uncertainty factor to account for using a less-than-lifetime study. ATSDR does not perform
quantitative cancer assessments or assign formal cancer classifications or descriptors.
World Health Organization (WHO)
(httys://www. who, int/water sanitation health/publications/drinkins-water-auality-suidelines-
4-includine-l st-adden du m/en/)
The World Health Organization (WHO) Guidelines for Drinking-Water Quality (GDWQ)
include facts sheets and comprehensive review documents for many individual chemicals. WHO
derives guideline values for many of these chemicals. For each chemical contaminant or
substance considered, a lead institution prepared a background document evaluating the risks for
human health from exposure to the particular chemical in drinking water. Under the
responsibility of the coordinators for a group of chemicals considered in the guidelines, the draft
health criteria documents were submitted to a number of scientific institutions and selected
experts for peer review. Comments were taken into consideration by the coordinators and authors
before the documents were submitted for final evaluation by the experts meetings. A "final task
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force" meeting reviewed the health risk assessments and public and peer review comments and,
where appropriate, decided upon guideline values.
The guidelines are intended to be used as a basis for the development of national
standards that, if properly implemented, will ensure the safety of drinking water supplies through
the elimination, or reduction to a minimum concentration, of constituents of water that are
known to be hazardous to health. WHO's guideline value is a drinking water concentration that
uses different default assumptions than EPA for estimating water concentration from doses,
including a 60 kg adult body weight, daily water consumption of 2 L/day, and a default relative
source contribution (RSC) for drinking water of 10 percent (unless data is available to derive an
RSC). WHO develops one guideline value that is based on either cancer or non-cancer health
effects.
Health Canada (HC) Guidelines for Canadian Drinking Water Quality Technical Documents
(https://www.canada.ca/en/health-canada/services/environmental-workplace-health/reports-
publications/water-quality. html#tech doc)
The Guidelines for Canadian Drinking Water Quality are established by Health Canada in
collaboration with the Federal-Provincial-Territorial Committee on Drinking Water (CDW) and
other federal government departments. Each guideline is established based on current, published
scientific research related to health effects, aesthetic effects, and operational considerations.
Health-based guidelines are established on the basis of comprehensive review of the known
health effects associated with each contaminant, on exposure levels, and on the availability of
treatment and analytical technologies. Aesthetic effects (e.g., taste, odor) are taken into account
when these play a role in determining whether consumers will consider the water drinkable.
Operational considerations are factored in when the presence of a substance may interfere with
or impair a treatment process or technology (e.g., turbidity interfering with chlorination or
ultraviolet (UV) disinfection) or adversely affect drinking water infrastructure (e.g., corrosion of
pipes).
Guidelines for Canadian Drinking Water Quality specifically for contaminants that meet
all of the following criteria:
• Exposure to the contaminant could lead to adverse health effects in humans;
• The contaminant is frequently detected or could be expected to be found in a large
number of drinking water supplies throughout Canada; and
• The contaminant is detected, or could be expected to be detected, in drinking water at a
level that is of possible human health significance.
If a contaminant or issue of interest does not meet all these criteria, Health Canada and
CDW may choose not to establish a numerical guideline or develop a guideline technical
document. In that case, advice may be provided through a guidance document in order to convey
operational or management information related to a contaminant or issue of concern. Guidelines
are systematically reviewed to assess the need to update them. When a guideline is reaffirmed,
both the year of the original publication and the year of reaffirmation are shown after the name
of the parameter.
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2.5 Contaminant Occurrence and Exposure
2.5.1 General Considerations
Detection and Reporting Thresholds
Several types of concentration thresholds are important in the characterization of
chemical contaminant occurrence in drinking water. This section clarifies some of the
terminology used in this report.
Typically, an analytical method allows for low-level detection of a contaminant in water
at concentrations that cannot be reliably quantified. Thus, there is a distinction between the
detection limit (the threshold at or above which the presence or absence of an identified
compound can be distinguished with a specified degree of confidence) and a quantitation limit or
reporting level (a somewhat higher threshold, at or above which the concentration of a
contaminant can be measured with a specified degree of precision and/or accuracy). Such
thresholds can vary from method to method, contaminant to contaminant, laboratory to
laboratory, and even from technician to technician, based on method limitations, chemical
properties, technician skill, and the quality of analytical instrumentation. Published analytical
methods specify the standards of precision and accuracy that define acceptable laboratory
performance, and often estimate "normal" or expected detection limits. In practice, the limits
vary.
The reporting level is the threshold at or above which a contaminant's presence or
concentration is officially quantitated. Reporting levels may be established by the laboratory or
by those who design and carry out a study. The requirements for precision and accuracy that are
included in a published analytical method help to dictate where laboratories establish a reporting
level for a particular analyte.
In the absence of an otherwise established reporting level, laboratories generally report
results as low as can be reliably measured based on precision and accuracy acceptance criteria
and the lowest calibration standard used in the development of their instrument calibration curve,
i.e., at the quantitation level. Sometimes the terms "quantitation level" and "reporting level" are
used interchangeably in the laboratory context.
In a well-designed occurrence study, the investigator will establish a reporting level for
each contaminant in advance of data collection, based on analytical method(s) chosen, laboratory
capabilities, and other considerations. Setting a reporting level is a balancing act: A reporting
level set too high will result in the under-reporting of contaminants that are present, while a
reporting level set too low may lead to data quality problems-e.g., some of the participating
laboratories may be unable to reliably quantify results at the low threshold. In the case of many
of EPA's nation-wide drinking water studies, the selected reporting level is known officially as
the Minimum Reporting Level (MRL). The MRL for each contaminant in each study is set at a
level that EPA believes can be achieved with specified confidence by a broad spectrum of
capable laboratories across the nation.
In some cases, an investigator may establish a "common reporting level," a high, uniform
reporting threshold for multiple contaminants that facilitates inter-contaminant comparison. A
common reporting level may be applied retrospectively. Some studies report results at low
contaminant-specific thresholds and also at a high common reporting level. Longitudinal studies
and data compilations sometimes select a high retrospective reporting level to facilitate
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comparison of results from older data collection efforts with results from newer efforts that
employed more advanced analytical techniques with lower quantitation limits.
Knowing the reporting level(s) associated with a study or data set can help with
interpretation of the results. For instance, knowing that the reporting level is lower than a health-
based threshold provides assurance that all exceedances of that threshold were captured in the
study results. Also, knowledge of reporting levels can help a reader to determine whether data
from two studies are directly comparable. Compilations of data from multiple sources must be
interpreted with caution if reporting levels are not documented, as they may have varied widely
(e.g., the percentage of positive results is highly dependent upon the reporting level used in each
study).
To facilitate interpretation of occurrence results in the contaminant-specific chapters that
follow, reporting levels are provided whenever they are available. In many cases reporting levels
are not known, and this too is documented. In some cases, the lowest reported concentration
values can give a rough idea of what the reporting threshold(s) might have been. (Generally, the
reporting level could not have been higher than the lowest reported concentration. If a
sufficiently large number of detections are reported, the lowest reported concentration is likely a
good approximation of the reporting level.)
Frequently the word detection is used in discussions of contaminant occurrence as
shorthand for a sampling result that is equal to or exceeds a given reporting level, and non-
detection for a result that does not equal or exceed the reporting level. Thus, even a sample that
exhibits a result that exceeds the laboratory detection limit could, in the context of a particular
study or data compilation, be considered a non-detection. That convention is followed in this
report, unless otherwise noted. For ambient water samples, laboratories will often report
estimated values that are equal to or greater than the detection limit but less than the reporting
level. In EPA drinking water programs, this practice is not used.
For more on detection levels, reporting levels, and MRLs in the context of analytical
method evaluation, see Section 2.6.
Rounding
In reporting quantitative occurrence findings, EPA is sensitive to the issue of presenting
numbers with the proper number of significant digits, if it can be determined, and the challenge
of presenting findings in a uniform format. EPA draws data from a wide variety of sources, some
of which are better-documented than others, and calculates other values from available data.
EPA uses the following guidelines in this support document.
When presenting results obtained from published studies or other sources, EPA reports
the numbers exactly as given in the source or retains the number of significant figures given in
the source. (All water concentration values are converted to micrograms per liter.)
When calculating new values, EPA follows the following guidelines: With limited
exceptions, calculated percentages are presented to two decimal places. With limited exceptions,
calculated concentration values (e.g., median and 99th percentile concentrations) are rounded, if
necessary, to have no more than three significant figures, and extrapolated population estimates
are also rounded, if necessary, to have no more than three significant figures. Beyond these
guidelines, ordinary best practices for rounding are applied.
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2.5.2 Occurrence in Ambient Water
This section describes sources EPA consulted to evaluate the occurrence in U.S. ambient
water (e.g., aquifers, rivers, lakes) of RD 4 contaminants receiving a regulatory determination.
USGS National Water Quality Assessment (NAWQA) — Ambient Water Analysis
The USGS instituted the National Water Quality Assessment (NAWQA) program in
1991 to examine ambient water quality status and trends in the United States. The NAWQA
program generates high quality contaminant occurrence and other water quality parameter data
for significant watersheds and aquifers across the nation. The program collects data on surface
and groundwater chemistry, hydrology, land use, stream habitat, and aquatic life in parts or all of
nearly all 50 States. The program is designed to apply nationally consistent methods to provide a
uniform basis for contaminant occurrence comparisons and assessments among study basins
across the country and over time. The occurrence assessments can also serve to facilitate
interpretation of natural and anthropogenic factors affecting national water quality. The Water
Quality Portal (WQP) houses a collection of chemical, biological, and physical water quality
data used in the NAWQA Program. For more detailed information on NAWQA program design
and implementation, refer to Leahy and Thompson (1994) and Hamilton et al. (2004).
The process of sampling, analysis, and data synthesis is divided into cycles of
approximately ten years: Cycle 1 covered 1991-2001, Cycle 2 covered 2002-2012, and Cycle 3 is
ongoing and covers 2013-2023. Study units are sampled and analyzed on a staggered schedule
within each cycle. Each NAWQA cycle begins with a two-year startup phase for planning and
retroactive analysis, followed by a three-year intensive data collection phase, and finally a five-
year phase for analyzing the data, developing reports, and continuing a low level of monitoring
(NRC, 2012).
During Cycle 1 (1991-2001), 51 study units were sampled. A total of 6,307 wells from
272 groundwater networks or clusters were monitored in Cycle 1. Surface water sampling points
(6,400 sampling points from 505 sites) were located on rivers and streams; lakes, reservoirs, and
coastal waters were excluded from the monitoring program.
In Cycle 2 (2002-2012), the number of study units was reduced from 51 in Cycle 1 to 42.
(NRC, 2012). Long-term stream monitoring was established at 113 streams representing 8 major
river basins. Long-term groundwater monitoring was established at sites representing 20
principal aquifers with more than 10 to 15 years of consistent monitoring data available (Rowe et
al., 2013).
Sampling for Cycle 3 is currently underway (2013-2023). Surface water monitoring will
be conducted at 313 sites, increased from 113 sites in Cycle 2 (Rowe et al., 2013). Groundwater
assessments in Cycle 3 will be designed to evaluate status and trends at the principal aquifer and
national scales. Assessments are planned in 24 principal aquifers that account for the majority of
current and future national groundwater use for drinking water. Note that data through 2017 are
presented in this report. For more details on the Cycle 3 sampling design, refer to Rowe et al.
(2010 and 2013).
EPA evaluated contaminant monitoring results from the NAWQA data downloaded from
the Water Quality Portal in September 2018 (WQP, 2018). EPA's analysis of the NAWQA data
is a simple, non-parametric analysis that provides summary statistics to characterize contaminant
occurrence. EPA calculated detection frequencies as the percentage of samples and the
percentage of sites with at least one detection, without any censoring or weighting. (A detection
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is an analytical result equal to or greater than the reporting level.) EPA reported the minimum
and maximum detection concentrations and calculated other descriptive statistics including the
median, 90th percentile, and 99th percentile (based only on samples with detections). Reporting
levels varied over time during the NAWQA program. In some cases, therefore, the minimum
concentration reported as a detection could be lower than the highest reporting level.
USGS issues many special reports based on NAWQA data that are summarized for
individual contaminant discussions. It may happen that multiple USGS reports rely on the same
underlying data. Also, depending on the purpose of the report, USGS sometimes restricts its
attention to a subset of data from an area (e.g., related to a specific land use). Selected special
USGS programs are noted in following paragraphs.
Note that there may be some overlap between the general NAWQA data assessment and
data presented in individual NAWQA studies and projects and compilations described below.
USGS Analysis: National Synthesis Assessments
Through a series of National Synthesis efforts, the USGS NAWQA program prepares
comprehensive analyses of data on topics of particular concern. These National Synthesis
assessments aggregate NAWQA contaminant occurrence and water quality parameter data from
individual study units and other sources to provide a national perspective on those topics.
Pesticide National Synthesis Project: Pesticides in the Nation's Streams and Ground
Water
The NAWQA Pesticide National Synthesis Project is a national-scale assessment of the
occurrence and behavior of pesticides in streams and groundwater of the United States and the
potential for pesticides to adversely affect drinking-water supplies or aquatic ecosystems.
Results from the Pesticide National Synthesis analysis, based on complete Cycle 1 (1992-
2001) data from NAWQA study units, are posted on the NAWQA Pesticide National Synthesis
website (Gilliom et al., 2007). Data for surface water and groundwater are presented separately,
and results in each category are subdivided by land use category. Land use categories include
agricultural, urban, mixed (deeper aquifers of regional extent in the case of groundwater), and
undeveloped. The Pesticide National Synthesis analysis is a first step toward the USGS goals of
describing the occurrence of pesticides in relation to different land use and land management
patterns and developing a deeper understanding of the relationship between spatial occurrence of
contaminants and their fate, transport, persistence, and mobility characteristics.
The surface water summary data presented in the Pesticide National Synthesis (Gilliom et
al., 2007) only includes stream data. Sampling data from a single one-year period, generally the
year with the most complete data, were used to represent each stream site. Sites with few data or
significant gaps were excluded from the analysis. NAWQA stream sites were sampled repeatedly
throughout the year to capture and characterize seasonal and hydrologic variability.
Groundwater data reported in the Pesticide National Synthesis only include samples from
wells; data from springs and agricultural tile drains were not included. In the National Synthesis
analysis (Gilliom et al., 2007), USGS uses a single sample to represent each well, generally the
earliest sample with complete data for the full suite of analytes.
Over the course of Cycle 1, some NAWQA analytical methods were improved or
changed. Hence, detection thresholds varied over time for some compounds (Gilliom et al.,
2007).
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Volatile Organic Compounds (VOC) National Synthesis: Volatile Organic Compounds in
the Nation's Ground Water andDrinking-Water Supply Wells
Zogorski et al. (2006) discuss the major findings and conclusions of a national
assessment of 55 VOCs in groundwater from 1985-2002. VOC data from 2,401 domestic wells
and 1,096 public wells were available from aquifer studies, shallow groundwater studies, and a
national source-water survey to characterize the occurrence of VOCs. One VOC analysis per
well was included in the assessment.
VOC National Synthesis: Random and Focused VOC Surveys
The VOC National Synthesis began in 1994. The most comprehensive VOC National
Synthesis reports to date are one random survey and one focused survey funded cooperatively by
the American Water Works Association Research Foundation (AwwaRF) (now known as the
Water Research Foundation, or WRF) and carried out by USGS in collaboration with the
Metropolitan Water District of Southern California and the Oregon Health & Science University.
The random survey (Grady, 2003) targeted surface and groundwaters used as source water by
community water systems (CWSs). Samples were taken from the source waters of 954 CWSs in
1999 and 2000. The random survey was designed to be nationally representative of CWS source
water. In the focused survey (Delzer and Ivahnenko, 2003), 451 samples were taken from source
waters serving 134 CWSs between 1999 and 2001. These surface and groundwaters were chosen
because they were suspected or known to contain Methyl Tertiary Butyl Ether (MTBE). The
focused survey was designed to provide insight into temporal variability and anthropogenic
factors associated with VOC occurrence. Details of the monitoring plan for these two studies,
including detection limits, are provided by Ivahnenko et al. (2001). Separately, AwwaRF also
published the results of this monitoring effort (AwwaRF, 2003).
VOC National Synthesis: Compilation of Historical VOC Monitoring Data
Additional products of the VOC National Synthesis include a compilation of historical
VOC monitoring data from multiple studies (Squillace et al., 1999). The data, collected from
2,948 wells between 1985 and 1995 by local, state, and federal agencies, were reviewed to
ensure they met data quality criteria. Most of the data were from early study unit monitoring. The
samples represent both urban and rural areas, and both drinking water and non-drinking water
wells.
Trace Elements National Synthesis Project: Trace Elements and Radon in Groundwater,
1992-2003
Ayotte et al. (2011) conducted an assessment as part of the NAWQA program, collecting
water samples in ambient groundwater and drinking water aquifers to evaluate the occurrence of
trace-element concentrations. A total of 1,309 samples were collected between 1992 and 2003
across the United States from more than 40 principal and other aquifers.
Non-NA WQA National Water Information System (NWIS) Data
The National Water Information System (NWIS) is the Nation's principal repository of
water resources data USGS collects from more than 1.5 million sites (USGS, 2016). NWIS-Web
is the general online interface to the USGS NWIS database. Discrete water-sample and time-
series data are available from sites in all 50 States, including 5 million water samples with 90
million water-quality results. All USGS water quality and flow data are stored in NWIS,
including site characteristics, streamflow, groundwater level, precipitation, and chemical
analyses of water, sediment, and biological media, though not all parameters are available for
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every site. NWIS houses the NAWQA data and includes other USGS data from unspecified
projects. NWIS contains many more samples at many more sites than the NAWQA Program.
Although NWIS is comprised of primarily ambient water data, some finished drinking water data
are included as well. The non-NAWQA data housed in NWIS generally involve fewer
constituents per sample than the NAWQA data. Unlike the NAQWA data, the non-NAWQA
data are a miscellaneous collection, so they are not as well-suited for making temporal and
geographic comparisons.
EPA evaluated contaminant monitoring results from the non-NAWQA data in NWIS
separately from NAWQA data; NWIS data were downloaded from the Water Quality Portal in
December 2017 (WQP, 2017).
Storage and Retrieval (STORET) Data System / Water Quality Exchange (WQX) / Water
Quality Portal Data System (WQP)
EPA's Water Quality Exchange (WQX) is the data format and mechanism for publishing
monitoring data available through the Water Quality Portal (WQP). In June of 2018, the WQX
replaced STORET as the mechanism for data partners to submit water monitoring data to EPA.
The Water Quality Portal is the mechanism for anyone, including the public, to retrieve water
monitoring data that were previously in STORET (referred to below as WQP STORET data), as
well as USDA Sustaining the Earth's Watersheds-Agricultural Research Data System
(STEWARDS) and USGS NWIS/BIODATA. The WQP contains raw biological, chemical, and
physical data from surface and groundwater sampling by federal, state and local agencies, Native
American tribes, volunteer groups, academics, and others. The WQP database includes data from
monitoring locations in all 50 states as well as multiple territories and jurisdictions of the United
States. Most data are from ambient waters, but in some cases finished drinking water data are
included as well. Data owners are responsible for providing data of documented quality, so that
data users can choose to access only those data collected and analyzed with data quality
objectives that meet their study needs. For more general WQX data information, please refer to:
https://www.epa.gov/waterdata/water-qualitv-data-wqx. To retrieve the data via WQP, please
refer to: https://www.waterqualitvdata.us/portal/.
The WQP STORET data presented in the contaminant-specific chapters were
downloaded from the WQP in December 2017 (WQP, 2017). (STORET data were downloaded
from the WQP by selecting the STORET database from the dropdown menu of available data
sources.) EPA reviewed WQP STORET groundwater data from wells and surface water data
from lakes, rivers/streams, and reservoirs (WQP, 2017). The WQP STORET data also included
public water system (PWS) data from four states (Indiana, Missouri, Ohio, and Washington);
EPA reviewed these as well (WQP, 2017). It is unclear if the PWS data were collected prior to or
subsequent to treatment.
Limitations of WQP STORET data quality include variations in the extent of national
coverage and data completeness from parameter to parameter. Data may have been collected as
part of targeted, rather than randomized, monitoring. Furthermore, there are no restrictions on
submission of data based on analytical methods or quality assurance (QA) practices.
Since reporting levels vary and are not always provided in the WQP STORET data, it is
generally not possible to present a single reporting level or even a range of reporting levels.
Instead, the chapters that follow point out the minimum detected concentration. The minimum
detected concentration, being equal to or probably no more than a little higher than one reporting
level, is probably in or near the range of reporting levels (see Section 2.5.1).
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2.5.3 Occurrence in Drinking Water - Primary Data Sources
The primary sources of the drinking water occurrence data used to support the RD 4
process, including selection and evaluation of RD 4 contaminants receiving a regulatory
determination, were the following:
the First Unregulated Contaminant Monitoring Rule (UCMR 1)
the Second Unregulated Contaminant Monitoring Rule (UCMR 2)
the Third Unregulated Contaminant Monitoring Rule (UCMR 3)
Rounds 1 and 2 of the Unregulated Contaminant Monitoring (UCM) program
• the Information Collection Rule (full title: "Monitoring Requirements for Public
Drinking Water Supplies: Cryptosporidium, Giardia, Viruses, Disinfection
Byproducts, Water Treatment Plant Data and Other Information Requirements")
the National Inorganics and Radionuclides Survey (NIRS)
All six of these sources are national assessments that were administered or overseen by
EPA. UCMR 1, UCMR 2, UCMR 3, and NIRS are designed to be statistically representative of
national contaminant occurrence in public drinking water systems. (NIRS, which does not
include surface water systems, is designed to be statistically representative of national
contaminant occurrence in groundwater systems.) The UCM program was a predecessor to the
Unregulated Contaminant Monitoring Rule (UCMR) program. Although UCM was not designed
to be statistically representative of national contaminant occurrence, the Agency subsequently
developed a peer-reviewed cross-section-based approach to elicit national estimates from UCM
data (see further discussion in the sub-sections of the report that follow). The design of the
Information Collection Rule included a census of large systems (serving greater than 100,000
people), so it can be considered representative of large systems, but not for systems serving
fewer than 100,000 people.
Summary occurrence values calculated for contaminants from primary data sources as
part of the RD 4 process include counts of the number and percent of systems, and population
served by systems, with at least one analytical detection above a given concentration threshold
(i.e., HRLs). EPA considered this to be a straightforward and accurate way to present these data
for the regulatory determination process. More specifically, EPA used the data sources to
generate the following occurrence and potential for exposure summary statistics for RD 4
contaminants receiving regulatory determinations:
• The total number of systems and the total population served by systems;
• The number and percentage of samples with detections, the 90th and 99th
percentile concentrations from samples with detections, and the minimum,
median, and maximum concentration from samples with detections;
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• The number and percentage of systems with at least one detected concentration
greater than or equal to the MRL, greater than the V2 HRL1 and greater than the
HRL; and
• The number and percentage of population served by systems with at least one
detected concentration greater than or equal to the MRL, greater than the V2 HRL
and greater than the HRL.
The final published UCMR 2 and UCMR 3 data sets provide source water type (e.g.,
groundwater, surface water) for the specific PWS facility at which the sample was taken. The
UCMR figures for "population served" are based on the PWS as a whole. For the purpose of the
analysis presented in this document, EPA used the PWS-level source water designations from the
Safe Drinking Water Information System/Federal Version (SDWIS/Fed) and population served
information from UCMR (based on the SDWIS/Fed population data as of the UCMR
applicability date: June 30, 2005, for UCMR 2 and December 31, 2010, for UCMR 3) for each
UCMR round (USEPA, 2009b; USEPA, 2014). Note that some systems' source waters include
both groundwater and surface water. To establish a single PWS-level source water type,
SDWIS/Fed categorized any system that includes both groundwater and surface water sources as
a "surface water" system. In this analysis, therefore, some results attributable to a surface water
system may be associated with a groundwater source at a mixed source water system.
Where the data from the primary sources permit, national extrapolations are made to
estimate the number of systems and the population in various size and source categories
potentially exposed to a given level of contamination. The extrapolations are made primarily
using national inventory information from the SDWIS/Fed. Other sources of data used to support
national extrapolations include the Community Water System Survey (CWSS) and the UCMR
program. When SDWIS/Fed data are used for national extrapolation of findings from a survey,
the SDWIS/Fed data freeze is selected to coincide most closely with the timing of the survey
design. For example, 2010 SDWIS/Fed inventory information was used for all extrapolations of
UCMR 3 results.
The analytical approach that is used to evaluate the contaminant monitoring data was
previously developed for other EPA Office of Ground Water and Drinking Water (OGWDW)
national occurrence studies, including the first Six-Year Review of National Primary Drinking
Water Regulations (USEPA, 2003b), UCMR 1 (USEPA, 2008a), and previous rounds of the
regulatory determination process (USEPA, 2002a; USEPA, 2008b). In each case, the data
analysis process and presentation were peer-reviewed and subject to public and stakeholder
review and comment.
Robust data from the UCMR program can support a more involved statistical analysis
(Stage 2 analysis) to assess and estimate the annual mean concentrations at systems, for
comparisons with HRLs. The Stage 2 approach, also peer-reviewed, is presented in the reports
Occurrence Estimation Methodology and Occurrence Findings for Six-Year Review of National
Primary Drinking Water Regulations (USEPA, 2003b) and The Analysis of Regulated
Contaminant Occurrence Data from Public Water Systems in Support of the Second Six-Year
Review of National Primary Drinking Water Regulations (USEPA, 2009c).
1 The use of the Vi HRL threshold is based on a recommendation from the National Drinking Water Advisory
Council (NDWAC) working group that provided recommendations on the first regulatory determinations effort
(USEPA, 2000b).
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The following sections provide a brief summary of primary drinking water data sources
and the approach used to estimate contaminant occurrence in each case. The ongoing UCMR
program is discussed first (covering the first three cycles, in order), followed by the older UCM
and NIRS programs. For some data sources, readers are referred to support documents from
earlier CCL and Regulatory Determination efforts for additional study details.
First Unregulated Contaminant Monitoring Rule (UCMR 1)
In 1999, EPA developed the UCMR program in coordination with the CCL and the
National Drinking Water Contaminant Occurrence Database (NCOD) to provide national
occurrence information on unregulated contaminants (64 FR 50556; USEPA, 1999b). The
UCMR is currently EPA's primary authority for collecting monitoring data on the occurrence of
unregulated contaminants in PWSs.
EPA designed the UCMR 1 data collection with three parts (or tiers) for monitoring,
primarily based on the availability of analytical methods and related analytical laboratory
capability. Contaminants for which well-established laboratory methods were available were
scheduled to undergo full UCMR 1 List 1 Assessment Monitoring. Contaminants whose
laboratory methods were newly developed and less widely available were placed on List 2; these
were scheduled for a "Screening Survey" at a smaller group of systems. The purpose of the
Screening Survey was to develop a preliminary assessment of national occurrence for
contaminants of concern that may be difficult to monitor at the larger scale of Assessment
Monitoring. List 3 monitoring ("Pre-Screen Testing") was intended to address contaminants with
analytical methods that are in an early stage of development; the analyses would be limited to a
few special laboratories. The expectation was that Pre-Screen Testing would only involve a
limited number of systems determined to be most vulnerable to the targeted contaminants. EPA
did not implement Pre-Screen Testing under UCMR 1 due to the lack of suitable candidate
methods.
EPA required all large PWSs (serving more than 10,000 people), plus a statistically
representative national sample of 800 small PWSs (serving 10,000 people or fewer), to conduct
Assessment Monitoring of List 1 contaminants.2 Approximately one-third of the participating
small systems were scheduled to monitor for the List 1 contaminants during each calendar year
from 2001 through 2003. Large systems could conduct one year of monitoring anytime during
the 2001-2003 UCMR 1 period. EPA specified a quarterly monitoring schedule for surface water
systems and a twice per year, six-month-interval monitoring schedule for groundwater systems.
Monitoring was scheduled so that one sampling event occurred during the most vulnerable
season for the water system.3 The objective of the peer-reviewed UCMR 1 sampling approach
for small systems was to collect contaminant occurrence data from a statistically selected,
nationally representative sample of small systems. The small system sample was stratified and
population-weighted, and included some other sampling adjustments such as ensuring the
selection of at least two systems from each state. With contaminant monitoring data from all
large PWSs and a nationally representative sample of small PWSs, the UCMR 1 List 1
2 Large and small systems that purchase 100 percent of their water supply were not required to participate in the
UCMR 1 Assessment Monitoring or Screening Survey.
3 Under UCMR1, the most vulnerable season was considered to be the season of greatest likelihood of contaminant
occurrence, generally in the months of late spring and early summer, which are characterized by high volumes of
surface water runoff and groundwater recharge.
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Assessment Monitoring program provides a contaminant occurrence data set suitable for national
drinking water estimates.
In total, 372,086 sample results were collected under the UCMR 1 List 1 Assessment
Monitoring program at 3,090 large systems and 797 small systems. Approximately 33,800
samples were collected for each contaminant. The UCMR 1 List 1 Monitoring program included
systems from all 50 states, the District of Columbia, four U.S. territories, and tribal lands in five
EPA Regions. See USEPA (2001a) and USEPA (2008a) for more information on UCMR 1 study
design and data analysis.
Second Unregulated Contaminant Monitoring Rule (UCMR 2)
UCMR 2 monitoring was conducted from 2008 through 2010 and was designed to
provide nationally representative contaminant occurrence data. Similar in design to UCMR 1,
UCMR 2 required surface water systems to monitor quarterly and groundwater systems to
monitor semi-annually to capture seasonal variability. As with UCMR 1, there were multiple
tiers of monitoring: Assessment Monitoring for contaminants with commonly used analytical
method technologies, and Screening Survey monitoring for contaminants that require specialized
analytical method technologies not in wide or common use at the time of study. (Again, there
was no Pre-Screen Testing.)
One difference between the UCMR 1 and UCMR 2 is that the UCMR 2 Screening
Survey consists of a larger sample of PWSs, as described in following paragraphs, and therefore
provides monitoring data statistically robust enough to support national contaminant occurrence
estimates. See USEPA (2005), USEPA (2007), and USEPA (2015) for more information on the
UCMR 2 program, including study design and data analysis.
For UCMR 2, all large PWSs (serving more than 10,000 people), plus a statistically
representative national sample of 800 small PWSs (serving 10,000 people or fewer), were
required to conduct Assessment Monitoring during a 12-month period between January 2008 and
December 2010. In total, 321,481 sample results were collected under the UCMR 2 List 1
Assessment Monitoring program at 3,340 large systems and 800 small systems.
For the UCMR 2 Screening Survey, monitoring was required by all PWSs serving more
than 100,000 people (approximately 400 PWSs, serving a large proportion of the national
population), 320 representative PWSs serving 10,001-100,000 people, and 480 representative
PWSs serving 10,000 people or fewer, during a 12-month period between January 2008 and
December 2010. With approximately 1,200 systems participating in the Screening Survey,
sufficient data were generated to provide a confident national estimate of contaminant
occurrence and population exposure. In UCMR 2, the 1,200 PWSs, provided more than 11,000
to 18,000 analyses (depending on the sampling design for the different contaminants). In total,
209,123 sample results were collected under the UCMR 2 List 2 Screening Survey Monitoring
program at 718 large systems and 480 small systems. Analysis of UCMR 2 results is found in the
chapters that follow and in Occurrence Data from the Second Unregulated Contaminant
Monitoring Regulation (UCMR 2) (USEPA, 2015).
Third Unregulated Contaminant Monitoring Rule (UCMR 3)
UCMR 3 monitoring was conducted from 2013 through 2015. Similar in design to
UCMR 1 and UCMR 2, UCMR 3 required surface water systems to monitor quarterly and
groundwater systems to monitor semi-annually to capture seasonal variability. As with UCMR 1
and UCMR 2, there were multiple tiers of monitoring: Assessment Monitoring for contaminants
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with commonly used analytical method technologies, Screening Survey monitoring for
contaminants that require specialized analytical method technologies not in wide or common use,
and pre-screen testing for contaminants that require newer analytical method technologies not in
wide or common use. See USEPA (2012b) and USEPA (2019b) for more information on the
UCMR 3 study design and data analysis, including a complete list of analytes.
For UCMR 3, all large and very large PWSs (serving between 10,001 and 100,000 people
and serving more than 100,000 people, respectively), plus a statistically representative national
sample of 800 small PWSs (serving 10,000 people or fewer), were required to conduct
Assessment Monitoring during a 12-month period between January 2013 and December 2015. In
total, 981,384 sample results were collected under the UCMR 3 List 1 Assessment Monitoring
program at 4,124 large systems and 799 small systems.
Analysis of UCMR 3 results is found in the chapters that follow and in Occurrence Data
from the Third Unregulated Contaminant Monitoring Regulation (UCMR 3) (USEPA, 2019b).
Unregulated Contaminant Monitoring (UCM) Program Rounds 1 and 2
In 1987, EPA initiated the UCM program to fulfill a 1986 SDWA Amendment
requirement to monitor for specified unregulated contaminants. The UCM required PWSs
serving more than 500 people to conduct monitoring. The intent of the monitoring was to gather
information on the occurrence of select contaminants in drinking water for future regulatory
decision-making purposes.
EPA implemented the UCM program in two phases or rounds. The first round of UCM
monitoring generally extended from 1988 to 1992 and is referred to as UCM Round 1
monitoring. The second round of UCM monitoring generally extended from 1993 to 1997 and is
referred to as UCM Round 2 monitoring.
UCM Round 1 monitoring initially involved 34 required VOCs, 14 VOCs to be
monitored at states' discretion, and two synthetic organic compounds (SOCs). Monitoring for
unregulated compounds was to be conducted alongside monitoring for regulated compounds (52
FR 25720; USEPA, 1987). The final database for this round of monitoring included 62 regulated
and unregulated contaminants (USEPA, 2001b). UCM Round 2 involved monitoring for 20
VOCs from the Round 1 required list and 14 VOCs from the Round 1 discretionary list, plus 13
SOCs and sulfate. The final database for this round of monitoring included 48 unregulated
contaminants (USEPA, 2001b). There was no requirement that the monitoring data be reported
to EPA and individual states maintained the data in different forms and formats. In the context of
various initiatives and information collection requests, many states voluntarily submitted the
UCM data to EPA. EPA worked to assemble the state data into a composite data set that would
support national occurrence estimates.
The UCM Round 1 and Round 2 data sets do not contain detailed reporting level
information. Reporting levels varied and were not explicitly labeled as MRLs, method detection
limits (MDLs), etc.
The UCM Round 1 database contains contaminant occurrence data from 38 states,
Washington, D.C., and the U.S. Virgin Islands. The UCM Round 2 database contains data from
35 states and several tribes. However, some state data sets were incomplete; hence national
occurrence estimates based on raw UCM Round 1 or Round 2 data could be skewed to low-
occurrence or high-occurrence settings (e.g., some states only reported detections). In addition,
certain types of land use and geologic/hydrologic settings could be over- or under-represented.
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To address potential biases in the data (including those due to incompleteness and lack of
representativeness), EPA developed national cross-sections from the UCM Round 1 and Round 2
state data using an approach similar to that used for EPA's 1999 Chemical Monitoring Reform
(USEPA, 1999c), the first Six-Year Review (USEPA, 2003b), and the first round of Regulatory
Determinations (USEPA, 2002a). This national cross-section approach for occurrence analyses
was supported by scientific peer reviewers and stakeholders. Using this approach, EPA
constructed national cross-sections using 24 of the 38 states from the UCM Round 1 database
and 20 of the 34 states from the UCM Round 2 data base. The support document The Analysis of
Occurrence Data from the Unregulated Contaminant Monitoring (UCM) Program and National
Inorganics and Radionuclides Survey (NIRS) in Support of Regulatory Determinations for the
Second Drinking Water Contaminant Candidate List (USEPA, 2008c) provides a description of
how the national cross-sections for the Round 1 and Round 2 data sets were developed and
utilized for making regulatory determinations.
Since UCM Round 1 and Round 2 data represent different time periods and include
occurrence data from different states, EPA developed separate national cross-sections for each
data set. The UCM Round 1 national cross-section, consisting of data from 24 states, includes
approximately 3.3 million records from approximately 22,000 unique PWSs. The UCM Round 2
national cross-section, consisting of data from 20 states, includes approximately 3.7 million
records from slightly more than 27,000 unique PWSs. The UCM Round 1 and 2 national cross-
sections represent significantly large samples of national occurrence data. Within each cross-
section, the actual number of systems and analytical records for each contaminant varies.
EPA constructed the national cross-sections in a way that provides a balance and range of
states with varying pollution potential indicators, a wide range of geologic and hydrologic
conditions, and a very large sample of monitoring data points. While EPA recognizes that some
limitations exist, the Agency believes that the national cross-sections do provide a reasonable
estimate of the overall distribution and the central tendency of contaminant occurrence across the
United States. For more information on the development of national cross-sections, refer to
USEPA (1999c), USEPA (2002a), and USEPA (2003b). See Exhibit 2-4 for a listing of states in
each national cross-section.
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Exhibit 2-4: Cross-section States for UCM Round 1 and Round 2
Alabama
Minnesota*
Alaska*
Alaska*
Montana
Arkansas
Arizona
New Jersey
Colorado
California
New Mexico*
Kentucky*
Florida
North Carolina*
Maine
Georgia
Ohio*
Maryland*
Hawaii
South Dakota
Massachusetts
Illinois
Tennessee
Michigan
Indiana
Utah
Minnesota*
Iowa
Washington*
Missouri
Kentucky*
West Virginia
Maryland*
Wyoming
New Hampshire
New Mexico*
North Carolina*
North Dakota
Ohio*
Oklahoma
Oregon
Rhode Island
Texas
Washington*
UCM Round 1 - 24-State Cross-Section
UCM Round 2 - 20-State Cross-Section
Source: USEPA, 2008c
* States in both Round 1 and Round 2 Cross-sections
National Inorganics and Radionuclides Survey (NIRS)
In the mid-1980's, EPA implemented NIRS to provide a statistically representative
sample of the national occurrence of select inorganic and radionuclide contaminants in CWSs
served by groundwater. The survey is stratified based on system size (population served by the
system). Most of the NIRS data are from smaller systems (92 percent from systems serving
3,300 persons or fewer).
The NIRS database includes findings for 42 radionuclides and inorganic compounds
(IOCs). NIRS provides contaminant occurrence data from 989 groundwater CWSs in 49 states
(all except Hawaii) as well as Puerto Rico. Surface water systems were not included in the study,
in part because IOCs tend to occur more frequently and at higher concentrations in groundwater
than in surface water. Each of the 989 randomly selected CWSs was sampled once between 1984
and 1986.
Because the NIRS data were collected in a randomly designed sample survey, the
summary statistics are representative of national occurrence in groundwater CWSs. Information
about NIRS monitoring and data analysis is available in Longtin (1988) and USEPA (2008c).
One limitation of the NIRS is a lack of occurrence data for surface water systems. To
provide perspective on the occurrence of the inorganic compounds in surface water systems
relative to groundwater systems, EPA also reviewed various supplemental data sources.
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2.5.4 Occurrence in Water - Secondary Data Sources
The Agency evaluated many additional sources of drinking water occurrence information
(including information on occurrence in "source" or "untreated" water, e.g., at the wellhead in
groundwater systems) to augment the primary drinking water occurrence data, to evaluate the
likelihood of contaminant occurrence, and/or to more fully characterize a contaminant's presence
in the environment. These data sources are generally narrower in geographic scope than the
primary drinking water data sources.
This section provides brief descriptions of many of the supplemental drinking water
information/data sources cited in contaminant data discussions in this document. In addition,
EPA considered selected studies published in the technical literature.
Information Collection Rule
The Monitoring Requirements for Public Drinking Water Supplies: Cryptosporidium,
Giardia, Viruses, Disinfection Byproducts, Water Treatment Plant Data and Other Information
Requirements (61 FR 24353; USEPA, 1996), also known as the "Information Collection Rule,"
required all PWSs serving at least 100,000 people to monitor and collect data on disinfection
byproducts (DBPs) over an 18-month period from July 1997 to December 1998. The DBP data
were collected from 296 very large water systems (that is, systems serving a population of more
than 100,000), including both surface water systems and groundwater systems. These very large
systems provided extensive information on the occurrence of DBPs and on water treatment
operations. The Information Collection Rule data were collected as part of a national research
project to support development of national drinking water standards. EPA used the data to
identify national and regional patterns. The data were not intended to support conclusions about
individual systems or treatment plants.
Information Collection Rule monitoring was conducted on a "per plant" basis; some
participating systems had more than one water treatment plant. For each plant, samples were
collected at source water, treatment plant, and distribution system locations. Sampling points
generally represented the point of entry into the distribution system, a point of maximum
residence time, or a point of average residence time. Samples were collected monthly for some
parameters such as pH, alkalinity, total organic carbon, etc. Quarterly samples were collected for
other parameters such as the trihalomethanes and haloacetic acids (USEPA, 1996).
While the Information Collection Rule only covered 296 systems, it was a census of the
largest systems in the nation, serving over half of the nation's population served by PWSs.
Additional details on the data collection process for the Information Collection Rule, along with
an independent analysis of the data, can be found in a report sponsored by the
Microbial/Disinfection Products Council (McGuire et al., 2002).
State Monitoring Data
Because there is no available national database that receives and stores all relevant data
regarding the occurrence of regulated contaminants in public drinking water systems, EPA
conducts voluntary data requests from the states, territories, and tribes in support of national
occurrence assessments. These assessments are part of the Six-Year Review (SYR).
Under the second and third Six-Year Review (SYR2 and SYR3), a few states submitted
PWS occurrence data for unregulated contaminants along with the requested data on regulated
contaminants. For SYR2, the result was a collection of unregulated contaminant monitoring data
from nine states and other entities, such as tribes, territories, and EPA Regions. For SYR3, the
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data set of unregulated contaminant monitoring data included results from 14 states/entities. For
both rounds of the SYR, these unregulated data provide varying degrees of completeness in their
coverage of the states/entities and are not necessarily representative of occurrence in those
states/entities. For more details on the SYR-Information Collection Request (ICR) data set for
SYR2, refer to USEPA (2009c). For more details on the SYR3-ICR Data set, refer to EPA's
SYR3 occurrence analysis (USEPA, 2016b).
The nine states/entities with SYR2 data were: California, Florida, Illinois, North
Carolina, Ohio, Region 9 Tribes, South Dakota, Texas, and Wisconsin. For SYR3, the data set of
unregulated contaminant monitoring data included results from 14 states/entities. The 14
states/entities with SYR3 data were: America Samoa, Region 1 Tribes, California, Florida,
Massachusetts, Michigan, Minnesota, Navajo Nation, Region 9 Tribes, Pennsylvania, South
Dakota, Washington, Washington, D.C., and Wisconsin.
For perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) specifically,
consistent with the Agency's commitment in the Per- and Polyfluroalkyl Substances (PFAS)
Action Plan to highlight "key information gathered by the Agency and our partners to date," the
Agency has supplemented its UCMR data with data collected by states who have made their data
publicly available. Based on public comments received for the preliminary RD 4 proposal where
some commenters identified additional data available in some specific states, recommended EPA
consider all readily available drinking water sampling conducted by states, or requested EPA
conduct a general search of all states for available data, EPA gathered updated state data during
the summer of 2020; chapters 3 and 4 of this document discuss state-specific dates for each state
in Exhibits 3-9 and 4-13. Using these assembled occurrence data, EPA updated the summary of
state occurrence data presented in the preliminary Regulatory Determination 4 Support
Document. EPA collected these occurrence data by downloading publicly available monitoring
data from state websites. Drinking water monitoring data for select contaminants were available
online from several states, including Alabama, Alaska, Arizona, California, Colorado, Georgia,
Kentucky, Maine, Massachusetts, Michigan, Missouri, New Hampshire, New Jersey, North
Carolina, North Dakota, Ohio, Pennsylvania, Rhode Island, and Vermont. For additional states,
EPA also considered data summarized from state websites, published studies, and/or publicly
available presentations that did not contain downloadable occurrence data. The available state
data are varied in terms of quantity and coverage. In many cases they represent targeted
monitoring. Thus, the monitoring data from each state are not necessarily representative of
occurrence in the state. Comprehensive information about methods used and reporting levels is
not available for the state monitoring data. Minimum detected concentrations reported may be
indicative of reporting levels used (see Section 2.5.1). Please see chapters 3 and 4 of this
document for more information on state data collected for PFOA and PFOS specifically.
2000 Community Water System Survey (2000 CWSS)
The 2000 Community Water System Survey (CWSS) (USEPA, 2002b; USEPA, 2002c)
gathered data on the financial and operating characteristics of a random sample of CWSs
nationwide. In addition, the Survey asked all CWSs serving more than 500,000 people (a total of
83 systems) to provide monitoring results for five regulated compounds (arsenic, atrazine, 2,4-D,
simazine, and glyphosate) and four unregulated compounds (radon, MTBE, metolachlor, and
boron), including results from raw water (i.e., before treatment) at each intake and from finished
water (i.e., following treatment) at each treatment plant. EPA received completed questionnaires
from 58 of the 83 systems. Not all systems answered every question. Note that because reported
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results are incomplete, they are only illustrative, not statistically representative, and are only used
as supplemental information.
2006 Community Water System Survey (2006 CWSS)
The 2006 CWSS (USEPA, 2009d; USEPA, 2009d) gathered data on the financial and
operating characteristics of a random sample of CWSs nationwide. All systems serving more
than 500,000 people (94 systems in 2006) were included in the sample, and systems in that size
category were asked questions about concentrations of unregulated contaminants in their raw and
finished water. Not all systems responded to the survey and, of the systems that responded to the
survey, not all systems answered every question. EPA supplemented the data set by gathering
additional information about contaminant occurrence at the systems in this size category from
publicly available sources (e.g., consumer confidence reports). Note that because reported results
are incomplete, they are only illustrative, not statistically representative, and are only used as
supplemental information.
Water Systems' Consumer Confidence Reports (CCRs)
CCRs are annual water quality reports that CWSs are required to provide to their
customers. These reports summarize information on water sources, detected contaminants, and
system compliance with EPA drinking water standards; they may also include general
educational material. Under the CCR Rule (40 CFR Subpart O), CWSs with 15 or more
connections or serving at least 25 year-round residents must prepare and distribute a CCR to all
billing units or service connections every year. Systems serving 100,000 or more residents are
also required to post their current CCRs on a publicly accessible Internet site. EPA reviewed
CCRs published by the 22 systems that serve over 1 million customers (as identified in the
UCMR 3 database) for unregulated contaminant occurrence information for the years 2010
through 2018. Note that because reported results are incomplete, they are more illustrative than
statistically representative, and are only used as supplemental information. In addition, CCRs
from 2013 to 2015 were not reviewed for contaminants with UCMR 3 data since UCMR 3 is
expected to provide more comprehensive data from the same period.
United States Department of Agriculture (USDA) Pesticide Data Program (PDP)
The USDA Pesticide Data Program (PDP) maintains a national pesticide residue
database. PDP was initiated in 1991 to collect data on pesticide residues in food with sampling
conducted on a statistically defensible representation of pesticide residuals in the United States
food supply (USDA, 2018). Sampling and testing are conducted on fruits and vegetables, select
grains, milk, and (as of 2001) drinking water.
The PDP drinking water program was initiated at CWSs in New York and California in
2001. Since then, the drinking water sampling program has expanded, though a somewhat
changing mix of states is sampled each year. At one time or another, CWSs in 29 states and
Washington, D.C., have contributed raw and/or finished water data to the program (USDA,
2018). The CWSs selected for sampling tend to be small- and medium-sized systems (primarily
CWSs serving under 50,000), systems served by surface water, and systems located in regions of
heavy agriculture. Sampling of untreated water in addition to treated water began in 2004;
sampling continued until 2013 (USDA, 2018). Note that temporal trends cannot be evaluated
based on these data since, with the exception of 2002 and 2003, samples were not collected from
the same sites and states in consecutive years.
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USGS-EPA Pilot Monitoring Program (PMP)
In 1999, the Pilot Monitoring Program (PMP) was initiated by the USGS and EPA to
provide information on pesticide concentrations in drinking water. This study particularly
focused on small drinking-water supply reservoirs in areas with high pesticide use to test the
sampling approach in areas where pesticides are probably present (Blomquist et al., 2001).
Sampling sites represent a variety of geographic regions, as well as different cropping patterns.
The ideal site candidates were mostly small reservoirs located in high pesticide-use areas, with a
high runoff potential. Twelve water-supply reservoirs, considered vulnerable to pesticide
contamination, were selected from the list of candidates. These 12 sites were located in
California, Indiana, Ohio, Oklahoma, Louisiana, Missouri, South Carolina, South Dakota, New
York, North Carolina, Pennsylvania, and Texas. Sampling began in 1999 and, because of
drought conditions in the Eastern United States and California in 1999, the program was
extended through 2000 at nine of the twelve monitoring sites.
Samples were collected quarterly throughout the year and at weekly or biweekly intervals
following the primary pesticide-application periods. Water samples were collected from the raw-
water intake and from finished drinking water taps prior to entering the distribution system. At
some sites, samples were also collected at the reservoir outflow.
USGS NA WQA — Source Water and Drinking Water Studies
Selected Trace Elements in Ground Water in the Glacial Aquifer System of the
Northern United States (Groschen etal., 2009), 1991-2003
Using NAWQA data, Groschen et al. (2009) assessed the occurrence and distribution of
several contaminants in groundwater of the glacial aquifer system in the Northern United States,
which underlies portions of New England, the Midwest, the Pacific Northwest, and Alaska. The
study analyzed data collected from 1,590 monitoring wells and water supply wells sampled
between 1991 and 2003.
Organic Compounds in Source Water of Selected Community Water Systems (Hopple
et al., 2009 and Kingsbury et al., 2008)
As part of the NAWQA program, Hopple et al. (2009) and Kingsbury et al. (2008)
conducted studies to characterize anthropogenic organic compounds in waters used as source
waters for PWSs in the United States. Hopple et al. (2009) focused on groundwater and
Kingsbury et al. (2008) focused on surface water. In Phase 1 of the studies, geographically
diverse source water samples were collected between October 2002 and July 2005 from 9 CWSs
served by streams and from 12 aquifers. In Phase 2, USGS collected source and finished water
samples at a subset of sites between June 2004 and September 2005.
Volatile Organic Compounds in Drinking Water of Selected Community Water
Systems (Grady and Casey, 2001), 1993-1998
USGS compiled and analyzed occurrence data for VOCs in finished drinking water in 12
Northeast and Mid-Atlantic states (Connecticut, Delaware, Maine, Maryland, Massachusetts,
New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Virginia).
State agencies supplied USGS with VOC data collected during 1993 through 1998 for 20 percent
of the CWSs in the 12-state area, which were chosen to be representative in terms of geography,
water source, and system size. Grady and Casey (2001) summarizes information on the quality of
drinking water from 2,110 randomly selected CWSs in the study area.
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Water Quality in Public-Supply Wells (Toccalino et al., 2010)
A study by Toccalino et al. (2010), conducted as part of the NAWQA Program, provides
information about the occurrence of regulated and unregulated contaminants in the environment.
Water samples were collected from source water (in this case, untreated groundwater) from 932
public-supply wells located in parts of 40 NAWQA Study Units in 41 states. Each well was
sampled once between 1993 and 2007. Six water-quality properties and 215 chemical
contaminants (58 regulated and 157 unregulated in drinking water) were analyzed. Whenever
possible, contaminant concentrations were compared to human-health benchmarks: Maximum
Contaminant Levels (MCLs) for 58 EPA-regulated contaminants and Health-Based Screening
Levels (HBSLs) for 96 of the unregulated contaminants. The public wells sampled in this study
represented 629 unique PWSs. The 629 PWSs with one or more wells sampled in this study
represent about 0.5 percent of the approximately 140,000 groundwater-supplied PWSs but nearly
25 percent of the population served by groundwater PWSs in the United States.
Water Quality in Domestic Wells (DeSimone, 2009)
As part of the NAWQA Program, USGS also conducted an assessment of the quality of
water from domestic wells across the United States (DeSimone, 2009). The program analyzed
the concentrations of major ions, trace elements, nutrients, radon, and organic compounds
(pesticides and VOCs) at approximately 2,100 domestic wells (private drinking water wells)
across 48 states, covering 30 regional aquifers. Water samples were collected between 1991 and
2004 from domestic wells. In addition, USGS summarized data from wells sampled for
NAWQA agricultural land-use assessment studies to provide an indication of the potential
effects of agricultural land-use practices on the groundwater in the aquifers studied.
Water Quality in Principal Aquifers of the United States (DeSimone et al., 2014), 1991-
2010
Another USGS report based on NAWQA Program ambient groundwater sampling
presents summaries of pesticide and other constituent occurrence in principal aquifers
(DeSimone et al., 2014). Samples were collected between 1990 and 2010 across the U.S. from
more than 60 principal aquifers that supply most of the groundwater pumped across the Nation
for drinking water, irrigation, and other uses.
Water Quality in Carbonate Aquifers (Lindsey et al., 2008)
A study by Lindsey et al. (2008), conducted as part of the NAWQA Program, provided
an assessment of the water quality in carbonate aquifers in the United States. Analytical results
from groundwater samples from 865 wells and 177 springs from 14 NAWQA study units (in 20
states) formed the basis of this study. The study analyzed samples collected between 1993 to
2005 for major ions, radon, nutrients, pesticides and VOCs. The 12 aquifer systems selected for
this study represent a wide range of climate, land-use types, and degrees of confinement. The
water use associated with the sampling sites used in this study fell into four categories: domestic
water use, public water use, "unused" (e.g., monitoring well or an abandoned domestic well), and
other (e.g., aquaculture, commercial, dewatering, industrial cooling, etc.). The study authors
evaluated occurrence of most VOCs at a uniform assessment level of 0.2 (J,g/L.
Volatile Organic Compounds (VOCs) in Domestic Wells (Moran et al., 2002; Rowe et
al., 2007), 1986-1999 and 1996-2002
As part of the NAWQA program, USGS studied the occurrence of VOCs in groundwater
from untreated rural self-supplied domestic wells between 1986 and 1999 (Moran et al., 2002).
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These sources of drinking water are not subject to EPA drinking water regulations. Water
samples were collected at the wellhead prior to treatment or storage. In most samples, 55 target
VOCs were analyzed. Reporting levels varied; results for most VOCs were reported at an
assessment level of 0.2 (J,g/L.
USGS also published the findings of a national assessment of VOCs in domestic wells
between 1996 and 2002 (Rowe et al., 2007). In this study, 2,401 domestic wells were sampled
between 1985 and 2002. Samples were collected at the wellhead before treatment of water and
analyzed for 55 VOCs.
USGS National Reconnaissance of Emerging Contaminants (NREC)
The USGS Water Resources Discipline (USGS WRD) prepared and provided various
water quality data to EPA for the deliberations and analyses used to develop the CCL 3. One of
the data sources, referred to as NREC (USEPA, 2008d), includes water quality occurrence data
collected by the USGS WRD Toxic Substances Hydrology Program from 1999 to 2004. Data are
included on approximately 100 chemicals, including various pharmaceuticals (human and
veterinary antibiotics, prescription and nonprescription drugs), various industrial and household
wastewater products (e.g., personal care products), some pesticides and their degradates, and
other wastewater-related compounds. There are two components to the NREC data: the national
reconnaissance data and the national aggregate data. The national reconnaissance data came from
nationally designed reconnaissance surveys that collected samples from streams, wells, and other
selected effluent sites from 30 states across the United States (and some of the data published in
Kolpin et al., 2002; Focazio et al., 2008; and Barnes et al., 2008). The national aggregate data
include data from additional sample collection and studies conducted by the WRD Science
Centers from 36 states across the country.
EPA / United States Geological Survey (USGS) Nationwide Reconnaissance of Contaminants
of Emerging Concern
As part of a joint study by EPA and the USGS to assess human exposure to contaminants
of emerging concern, water samples were collected from 25 drinking water treatment plants
(DWTPs) in 24 states (Glassmeyer et al., 2017). Participation in the study was voluntary, and
candidate locations were selected based on nomination by EPA and the USGS regional personnel
and DWTP self-nomination as well as consideration of high wastewater contribution and the
availability of pharmaceutical concentration data. Final sample locations were chosen to
represent a wide range of geography, diversity in disinfectant type used, and a range of
production volumes. Phase I of the study (2007) analyzed a subset of contaminants and sites to
test experimental design. During Phase II of the study (2010-2012), samples were collected from
groundwater and surface water sources and treated drinking water from 25 DWTPs.
National Pesticide Survey (NPS)
In 1990, EPA completed a national survey of pesticides in the source water of drinking
water wells. The purpose of the National Pesticide Survey (NPS) was to determine the national
occurrence frequencies and concentrations of select pesticides in the nation's drinking water
wells, and to improve EPA's understanding of how pesticide occurrence in groundwater
correlates with patterns of pesticide usage and groundwater vulnerability. The survey included
approximately 1,300 CWS wells and rural domestic wells. Sampling was conducted between
1988 and 1990. The survey targeted areas representing a variety of pesticide usage levels and
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groundwater vulnerability. The survey was designed to provide a statistically reliable estimate of
pesticide occurrence in the nation's drinking water wells. It was not designed to provide
statistically valid results at the state or local level. Wells were sampled for 101 pesticides, 25
pesticide degradates, and nitrate (USEPA, 1990).
Environmental Working Group (EWG) Drinking Water Database
In July 2017, the EWG released their "National Drinking Water Database" which
includes drinking water occurrence data for both regulated and unregulated drinking water
contaminants. Results were compiled for samples collected between 2010 and 2015 from all 50
states and the District of Columbia (EWG, 2018). According to EWG, the 2017 database
includes results for 502 contaminants.
The EWG reports that it reviewed the data for inconsistencies and invited the American
Water Works Association and the Association of Metropolitan Water Agencies to review their
data and/or have the data verified by the PWSs included in the study.
The EWG online data include counts, by state, of the number of systems that had
detections of each contaminant and the population served by those systems, as well as counts
(when available) of the number of systems with exceedances of contaminant-specific thresholds
and the associated population served. The EWG established the thresholds by surveying health-
based and legal limits established by state and federal agencies and selecting the most
conservative one for each contaminant. Note that although the EWG provides some data on
contaminant concentration, the presentation of the concentration data is not complete.
Specifically, the EWG only provides concentration data (study-wide average and range of daily
average detected concentrations) from the ten water systems with the highest average detected
concentrations of each contaminant. Hence, the data are not sufficient to estimate the magnitude
of occurrence. EWG data are not discussed further in this report.
The Centers for Disease Control and Prevention (CDC) Fourth National Report on Human
Exposure to Environmental Chemicals, 2019 Updated Tables
To assess the U.S. population's exposure to environmental chemicals, CDC monitors
concentrations of select chemicals in human blood and urine. Since 1999, the National Health
and Nutrition Examination Survey (NHANES) has examined the U.S. population annually and
released the data in 2-year cycles. The survey is based on a representative sample of the U.S.
population based on age, gender, and race/ethnicity (CDC, 2019). Thq Fourth National Report
on Human Exposure to Environmental Chemicals was published in 2009 (CDC, 2009). The
exposure data tables have been updated several times since the original publication, most
recently in 2019 (CDC, 2019). EPA consulted the 2019 updated tables for additional perspective
on exposure.
2.6 Analytical Methods
EPA has evaluated the availability of drinking water analytical methods for the
contaminants currently prioritized for regulatory determination. In the case of a positive
regulatory determination, EPA needs to ensure that laboratories have a standardized and
validated analytical method that can measure the newly regulated contaminant with confidence at
the MCL by the time a NPDWR using an MCL goes into effect. Note that SDWA provides for
the promulgation of a NPDWR that requires the use of a Treatment Technique (TT) rather than
an MCL in the event that it is not economically or technologically feasible to ascertain the level
of the contaminant in water (SDWA 1412(b)(7)(A).
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The following analytical method performance metrics are useful and are typically
available for assessing method sensitivity. The Lowest Concentration Minimum Reporting Level
(LCMRL) is generally representative of the single EPA laboratory that developed the method,
while the Minimum Reporting Level (MRL) is designed to be applied nationally in the context of
UCMR monitoring during a specific UCMR cycle for which that MRL was developed:
• LCMRL - The LCMRL is a single-laboratory reporting level for selected EPA analytical
methods. It is determined via a statistical model of future analyte recovery using the
method, where the future recovery is predicted to fall between 50% to 150% with 99%
confidence.
• MRL - The MRL is a reporting level used for national application in EPA's UCMR
program. For UCMR 1 analytes, the MRL was established by EPA in light of anticipated
laboratory capability. For UCMR 2, UCMR 3, and Fourth Unregulated Contaminant
Monitoring Rule (UCMR 4) analytes, the MRL has been determined via a statistical
model from raw LCMRL study data from multiple laboratories (typically three per
MRL).
2.7 Treatment Technologies
EPA evaluates whether suitable treatment technologies are available prior to
promulgating a final National Primary Drinking Water Regulation (NPDWR).
EPA reviewed information on treatment technologies for the contaminants that proceeded
to phase 3 and summarized that information in the chapters that follow. Where available, EPA
relied on information in the Agency's Drinking Water Treatability Database (USEPA, 2020). In
cases where Database did not provide coverage for a contaminant, EPA relied on literature
searches conducted in prior years.
2.8 References
American Water Works Association Research Foundation (AwwaRF). 2003. Occurrence of
MTBE and VOCs in Drinking Water Sources of the United States.
Ayotte, J.D., J.M. Gronberg, andL.E. Apodaca. 2011. Trace Elements and Radon in
Groundwater Across the United States. U.S. Geological Survey Scientific Investigations
Report 2011-5059. 115 pp. Available from:
https://pubs.usgs.gov/sir/201 l/5059/pdf/sir2011-5059 report-covers 508.pdf
Barnes, K.K., D.W. Kolpin, E.T. Furlong, S.D. Zaugg, M.T. Meyer, and L.B. Barber. 2008. A
National Reconnaissance of Pharmaceuticals and Other Organic Wastewater
Contaminants in the United States—I. Groundwater. Science of the Total Environment.
402(2-3): 192-200.
Blomquist, J.D., J.M. Denis, J.L. Cowles, J.A. Hetrick, R.D. Jones, and N.B. Birchfield. 2001.
Pesticides in Selected Water-Supply Reservoirs and Finished Drinking Water, 1999-
2000: Summary of Results from a Pilot Monitoring Survey. U.S. Geological Survey
Open-File Report 01-456. 65 pp. Available on the Internet at:
https://pubs.er.usgs.gov/publication/ofr01456.
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Centers for Disease Control and Prevention (CDC). 2009. Fourth National Report on Human
Exposure to Environmental Chemicals, Department of Health and Human Services,
Centers for Disease Control and Prevention. Available on the Internet at:
https://www.cdc.gov/exposurereport/pdf/fourthreport.pdf.
CDC. 2019. Fourth National Report on Human Exposure to Environmental Chemicals, Updated
Tables, January 2019: Volume One. Department of Health and Human Services, Centers
for Disease Control and Prevention. Available on the Internet at:
http://www.cdc.gov/exposurereport/.
Delzer, G.C. and T. Ivahnenko. 2003. Occurrence and Temporal Variability of Methyl tert-Butyl
Ether (MTBE) and Other Volatile Organic Compounds in Select Sources of Drinking
Water: Results of the Focused Survey. U.S. Geological Survey Water-Resources
Investigations Report 02-4084. 65 pp. Available on the Internet at:
https://pubs.er.usgs.gov/publication/wri024084.
DeSimone, L.A. 2009. Quality of Water from Domestic Wells in Principal Aquifers of the United
States, 1991-2004. U. S. Geological Survey Scientific Investigations Report 2008-5227.
139 pp. Available on the Internet at: http://pubs.usgs.gov/sir/2008/5227/.
DeSimone, L.A., P.B. McMahon, and M.R. Rosen. 2014. The Quality of Our Nation's Waters—
Water Quality in Principal Aquifers of the United States, 1991-2010. U.S. Geological
Survey Circular 1360, 151 p. Available on the Internet at: http://pubs.usgs.gov/circ/1360/.
Environmental Working Group (EWG). 2018. EWG's Tap Water Database, Data Sources and
Methodology. Available on the Internet at:
https://www.ewg.org/tapwater/methodology.php. Accessed December 5, 2018.
Focazio, M.J., D.W. Kolpin, K.K. Barnes, E.T. Furlong, M.T. Meyer, S.D. Zaugg, L.B. Barber,
and E.M. Thurman. 2008. A National Reconnaissance of Pharmaceuticals and Other
Organic Wastewater Contaminants in the United States—II. Untreated Drinking Water
Sources. Science of the Total Environment 402(2-3):201-216.
Gilliom, R.J., J.E. Barbash, C.G. Crawford, P.A. Hamilton, J.D. Martin, N. Nakagaki, L.H.
Nowell, J.C. Scott, P.E. Stackelberg, G.P. Thelin, and D.M. Wolock. 2007. The Quality
of Our Nation's Waters - Pesticides in the Nation's Streams and Ground Water, 1992-
2001. Appendix 7. Statistical summaries of water-quality data. U.S. Geological Survey
Circular 1291. 172 pp. Available on the Internet at:
http://water.usgs.gov/nawqa/pnsp/pubs/circl291/appendix7/.
Glassmeyer, S.T., E.T. Furlong, D.W. Kolpin, A.L. Batt, R. Benson, J. S. Boone, O. Conerly,
M.J. Donohue, D.N. King, M.S. Kostich, H.E. Mash, S.L. Pfaller, K.M. Schenck, J.E.
Simmons, E.A. Varughese, S.J. Vesper, E.N. Villegas, and V.S. Wilson. 2017.
Nationwide Reconnaissance of Contaminants of Emerging Concern in Source and
Treated Drinking Waters of the United States. Science of the Total Environment (581-
582):909-922.
Grady, S.J. and G.D. Casey. 2001. Occurrence and Distribution of Methyl tert-Butyl Ether and
Other Volatile Organic Compounds in Drinking Water in the Northeast and Mid-Atlantic
Regions of the United States, 1993-98. U.S. Geological Survey Water-Resources
Investigations Report 00-4228. 128 pp. Available on the Internet at:
https://pubs.er.usgs.gov/publication/wri004228.
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Grady, S.J. 2003. A National Survey of Methyl tert-Butyl Ether and Other Volatile Organic
Compounds in Drinking-Water Sources: Results of the Random Survey. U.S. Geological
Survey Water-Resources Investigations Report 02-4079. 85 pp. Available on the Internet
at: https://pubs.er.usgs.gov/publication/wri024079.
Groschen, G.E., T.L. Arnold, W.S. Morrow, and K.L. Warner. 2009. Occurrence and
Distribution of Iron, Manganese, and Selected Trace Elements in Ground Water in the
Glacial Aquifer System of the Northern United States. U.S. Geological Survey Scientific
Investigations Report 2009-5006. 89 pp. Available on the Internet at:
http://pubs.usgs.gov/sir/2009/50Q6/.
Hamilton, P. A., T.L. Miller, and D.N. Myers. 2004. Water Quality in the Nation's Streams and
Aquifers: Overview of Selected Findings, 1991-2001. USGS Circular 1265. Available on
the Internet at: http://water.usgs.gov/pubs/circ/2004/1265/pdf/circularl265.pdf.
Hopple, J.A., G.C. Delzer, and J.A. Kingsbury. 2009. Anthropogenic Organic Compounds in
Source Water of Selected Community Water Systems that Use Groundwater, 2002-05.
U.S. Geological Survey Scientific Investigations Report 2009-5200. 74 pp. Available on
the Internet at: http://pubs.usgs.gov/sir/2009/5200/pdf/sir2009-5200.pdf.
Ivahnenko, T., S.J. Grady, and G.C. Delzer. 2001. Design of a National Survey of Methyl tert-
Butyl Ether and Other Volatile Organic Compounds in Drinking-Water Sources. U.S.
Geological Survey Open-File Report 01-271. 42 pp. Available on the Internet at:
https://pubs.er.usgs.gov/publication/ofr01271.
Kingsbury, J.A., G.C. Delzer, and J.A. Hopple. 2008. Anthropogenic Organic Compounds in
Source Water of Nine Community Water Systems that Withdraw from Streams, 2002-05.
U.S. Geological Survey Scientific Investigations Report 2008-5208. 66 pp. Available on
the Internet at: http://pubs.usgs.gov/sir/2008/5208/pdf/sir2008-5208.pdf.
Kolpin, D.W., E.T. Furlong, M.T. Meyer, E.M. Thurman, S.D. Zaugg, L.B. Barber, and H.T.
Buxton. 2002. Pharmaceuticals, Hormones, and Other Organic Wastewater Contaminants
in U.S. Streams, 1999-2000: A National Reconnaissance. Environmental Science and
Technology 3 6(6): 1202-1211.
Leahy, P.P. and T.H. Thompson. 1994. The National Water-Quality Assessment Program. U.S.
Geological Survey Open-File Report 94-70. 4 pp. Available on the Internet at:
http://water.usgs.gov/nawqa/NAWOA.OFR94-7Q.html.
Lindsey, B.D., M.P. Berndt, B.G. Katz, A.F. Ardis, and K.A. Skach. 2008. Water Quality in
Carbonate Aquifers in the United States, 1993-2005. U.S. Geological Survey Scientific
Investigations Report 2008-5240. Available on the Internet at:
http://pubs.usgs.gov/sir/2008/524Q/.
Longtin, J.P. 1988. Occurrence of Radon, Radium and Uranium in Groundwater. Journal of the
American Water Works Association. 80(7): 84-93.
McGuire, M.J., J.L. McLain, and A. Obolensky. 2002. Information Collection Rule Data
Analysis. Sponsored by the Microbial/Disinfection By-Products Research Council.
Jointly funded by AwwaRF and USEPA. Published by AwwaRF and AWWA.
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Moran, M.J., W.W. Lapham, B.L. Rowe, and J.S. Zogorski. 2002. Occurrence and Status of
Volatile Organic Compounds in Ground Water from Rural, Untreated, Self-Supplied
Domestic Wells in the United States, 1986-1999. U.S. Geological Survey Water-
Resources Investigations Report 02-4085. 51 pp.
National Center for Food and Agricultural Policy (NCFAP). 2000. Pesticide Use in U.S. Crop
Production: 1997. National Summary Report. Available on the Internet at:
http://www.ncfap.org/documents/nationalsummaryl997.pdf.
National Research Council (NRC). 2012. Preparing for the Third Decade of the National Water-
Quality Assessment Program. Washington, D.C.: National Academies Press.
Rowe, B.L., P.L Toccalino, M.J. Moran, J.S. Zogorski, and C.V. Price. 2007. Occurrence and
Potential Human-Health Relevance of Volatile Organic Compounds in Drinking Water
from Domestic Wells in the United States. Environmental Health Perspectives 115(11):
1539-46.
Rowe, G.L., K. Belitz, H.I. Essaid, R.J. Gilliom, P A. Hamilton, A.B. Hoos, D.D. Lynch, M.D.
Munn, and D.W. Wolock. 2010. Design of Cycle 3 of the National Water-Quality
Assessment Program, 2013-2023: Part 1: Framework of Water-Quality Issues and
Potential Approaches. U.S. Geological Survey Open-File Report 2009-1296.
https://pubs.usgs.gov/of/2009/1296/
Rowe, G.L., K. Belitz, C.R. Demas, H.I. Essaid, R.J. Gilliom, P A. Hamilton, A.B. Hoos, C.J.
Lee, M.D. Munn, and D.W. Wolock. 2013. Design of Cycle 3 of the National Water-
Quality Assessment Program, 2013-23: Part 2: Science Plan for Improved Water-Quality
Information and Management. U.S. Geological Survey. Open-File Report 2013-1160.
https://pubs.er.usgs.gov/publication/ofr20131160.
Squillace, P.J., M.J. Moran, W.W. Lapham, C.V. Price, R.M. Clawges and J.S. Zogorski. 1999.
Volatile organic compounds in untreated ambient groundwater of the United States,
1985-1995. Environmental Science and Technology. 33(23):4176-4187. Available on the
Internet at: https://pubs.er.usgs.gov/publication/70021047.
Toccalino, P.L., J.E. Norman, and K.J. Hitt. 2010. Quality of Source Water from Public-supply
Wells in the United States, 1993-2007. U.S. Geological Survey Scientific Investigations
Report 2010-5024. 206 pp. Available on the Internet at:
http://pubs.usgs.gov/sir/2010/5Q24/.
United States Department of Agriculture (USDA). 2018. PDP Drinking Water Project (2001 -
2013). Available on the Internet at: https://www.ams.usda.gov/datasets/pdp/pdp-drinking-
water-proiect.
USEPA. 1987. National Primary Drinking Water Regulations-Synthetic Organic Chemicals;
Monitoring for Unregulated Contaminants: Final Rule. Federal Register. Vol. 52, No.
130, p. 25720, July 8, 1987.
USEPA. 1990. National Pesticide Survey: Survey Analytes. EPA 570-9-90-NPS2. Available on
the Internet at: http://www.epa.gov/nscep/index.html [Search for document number
570990NPS2.]
USEPA. 1996. Monitoring Requirements for Public Drinking Water Supplies. Federal Register.
Vol. 61, No. 94, p. 24353, May 14, 1996.
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USEPA. 1999a. "Chapter 3 - Year-to-Year Comparison of Toxics Release Inventory Data," in
1997 Toxics Release Inventory. Office of Pollution Prevention and Toxics. April. EPA
745-R-99-003. Available on the Internet at:
https://nepis.epa.gov/Exe/ZvPDF.cgi/20001JP4.PDF?Dockey=20001JP4.PDF.
USEPA. 1999b. Revisions to the Unregulated Contaminant Monitoring Regulation for Public
Water Systems; Final Rule. Federal Register. Vol. 64, No. 80, p. 50556, September 17,
1999.
USEPA. 1999c. A Review of Contaminant Occurrence in Public Water Systems. EPA-816-R-99-
006, Office of Water.
USEPA. 2000a. The Role of Use-Related Information in Pesticide Risk Assessment and Risk
Management. August 21, 2000. Office of Pesticide Programs. Available on the Internet
at: https://archive.epa.gov/pesticides/trac/web/pdf/use-related.pdf.
USEPA. 2000b. National Drinking Water Advisory Council Minutes of Meeting Held June 14,
2000. EPA 810-S-00-001. August 2000.
USEPA. 2001a. Reference Guide for the Unregulated Contaminant Monitoring Regulation.
Office of Water. EPA 815-R-01-023. 65 pp.
USEPA. 2001b. Occurrence of Unregulated Contaminants in Public Water Systems: An Initial
Assessment. EPA 815-P-00-001. May, 2001.
USEPA. 2002a. Analysis of National Occurrence of the 1998 Contaminant Candidate List (CCL)
Regulatory Determination Priority Contaminants in Public Water Systems. May 2002.
EPA-815-D-01-002, Office of Water.
USEPA. 2002b. Community Water System Survey 2000. Volume I: Overview. EPA 815-R-02-
005A. December. Available on the Internet at:
http://nepis.epa. gov/Exe/ZyPDF.cgi?Dockev=20001ZK5.txt.
USEPA. 2002c. Community Water System Survey 2000. Volume II: Detailed Tables and Survey
Methodology. EPA 815-R-02-005B. December. Available on the Internet at:
http://nepis.epa. gov/Exe/ZyPDF.cgi?Dockev=2000JTKL.txt.
USEPA. 2003a. How are the Toxics Release Inventory Data Used? EPA 260-R-002-004. May.
Available on the Internet at:
https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockev=900B0I00.TXT.
USEPA. 2003b. Occurrence Estimation Methodology and Occurrence Findings for Six-Year
Review of National Primary Drinking Water Regulations. EPA Report 815-R-03-006,
Office of Water.
USEPA. 2005. Unregulated Contaminant Monitoring Regulation (UCMR) for Public Water
Systems Revisions; Proposed Rule. Federal Register. Vol. 70, No. 161, p. 49093, August
22, 2005.
USEPA. 2007. Unregulated Contaminant Monitoring Regulation (UCMR) for Public Water
Systems Revisions. Federal Register. Vol. 72, No. 2, p. 367, January 4, 2007.
USEPA. 2008a. The Analysis of Occurrence Data from the First Unregulated Contaminant
Monitoring Regulation (UCMR 1) in Support of Regulatory Determinations for the
Second Drinking Water Contaminant Candidate List. EPA 815-R-08-012. June 2008.
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USEPA. 2008b. Drinking Water: Regulatory Determinations Regarding Contaminants on the
Second Drinking Water Contaminant Candidate List. Federal Register. Vol. 73, No. 147,
p. 44251. July 30, 2008.
USEPA. 2008c. The Analysis of Occurrence Data from the Unregulated Contaminant
Monitoring (UCM) Program and National Inorganics and Radionuclides Survey (NIRS)
in Support of Regulatory Determinations for the Second Drinking Water Contaminant
Candidate List. EPA 815-R-08-012. June 2008.
USEPA. 2008d. Contaminant Candidate List 3 Chemicals: Identifying the Universe. EPA 815-R-
08-002. Draft.
USEPA. 2009a. Final Contaminant Candidate List 3 Chemicals: Classification of the PCCL to
CCL. Office of Water. EPA 815-R-09-008. Available on the Internet at:
https://www.epa.gov/sites/production/files/2014-05/documents/ccl3 pccltoccl 08-31-
09 508.pdf
USEPA. 2009b. Excel file titled "UCMR2 applicable systems (Novl8_2009).xls," emailed from
Dan Hautman (EPA) to Clifton Townsend (EPA) on November 18, 2009.
USEPA. 2009c. The Analysis of Regulated Contaminant Occurrence Data from Public Water
Systems in Support of the Second Six-Year Review of National Primary Drinking Water
Regulations. EPA-815-B-09-006. October 2009.
USEPA. 2009d. Community Water System Survey 2006. Volume 1: Overview. EPA 815-R-09-
001. Available on the Internet at:
https://nepis. epa.gov/Exe/ZyPDF. cgi?Dockev=P 1009JJI.txt.
USEPA. 2009d. Community Water System Survey 2006. Volume II: Detailed Tables and Survey
Methodology. EPA 815-R-09-002. Available on the Internet at:
https://nepis. epa.gov/Exe/ZyPDF. cgi?Dockev=P 1009USA.txt.
USEPA. 2012a. Estimation Program Interface (EPI Suite™) Program Modification & New
Features in v4.11 (November 2012). Available on the Internet at:
https://19ianuarv2017snapshot.epa.gov/tsca-screening-tools/estimation-program-
interface-epi-suite-tm-program-modifications-new-features .html
USEPA. 2012b. Revisions to the Unregulated Contaminant Monitoring Regulation (UCMR 3)
for Public Water Systems. Federal Register. Vol 77. No. 85, p. 26072, May 2, 2012.
USEPA. 2014. Excel file titled "Population and Size.xls," containing NCOD data for October
2014, emailed via weblink from Michella Karapondo (EPA) to Brent Ranalli (The
Cadmus Group) on November 7, 2014.
USEPA. 2015. Occurrence Data from the Second Unregulated Contaminant Monitoring
Regulation (UCMR 2). December 2015. EPA-815-R-15-013.
USEPA. 2016a. 2016 Chemical Data Reporting Frequent Questions. Available on the Internet at:
https://www.epa.gov/chemical-data-reporting/2016-chemical-data-reporting-frequent-
questions. Last updated July 11, 2016.
USEPA. 2016b. Analysis of Occurrence Data from the Third Six-Year Review of Existing
National Primary Drinking Water Regulations: Chemical Phase Rules and Radionuclides
Rules. December 2016. EPA-810-R-16-014.
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USEPA. 2017. Pesticide Industry Sales and Usage: 2008 to2012 Market Estimates. Biological
and Economic Analysis Division, Office of Pesticide Programs. Available on the Internet
at: https://www.epa.gov/sites/production/files/2017-01/documents/pesticides-industry-
sales-usage-2016 O.pdf.
USEPA. 2019a. Factors to Consider When Using Toxics Release Inventory Data. Available on
the Internet at: https://www.epa.gov/toxics-release-inventorv-tri-program/factors-
consider-when-using-toxics-release-inventory-data.
USEPA. 2019b. Occurrence Data from the Third Unregulated Contaminant Monitoring Rule
(UCMR 3). EPA 815-R-19-007.
USEPA. 2020. Drinking Water Treatability Database.
https://iaspub.epa.gov/tdb/pages/general/home.do. Last updated March 2020.
United States Geological Survey (USGS). 2016. National Water Information System (NWIS)
Water-Quality Web Services, https://waterdata.usgs.gov/nwis. Last modified December
2016.
USGS. 2018. Pesticide National Synthesis Project, Pesticide Use Maps. Available on the Internet
at: http://water.usgs.gov/nawqa/pnsp/usage/maps/compound listing.php?vear=02.
Accessed December 2018.
Water Quality Portal (WQP). 2017. Water Quality Portal Data Warehouse. Available on the
Internet at: https://www.waterqualitvdata.us/. Data Warehouse consulted December 2017.
WQP. 2018. Water Quality Portal Data Warehouse. Available on the Internet at:
https://www.waterqualitvdata.us/. Data Warehouse consulted September 2018.
Zogorski, J.S., J.M. Carter, T. Ivahnenko, W.W. Lapham, M.J. Moran, B.L. Rowe, P.J.
Squillace, and P.L. Toccalino. 2006. Volatile Organic Compounds in the Nation's
Ground Water andDrinking-Water Supply Wells. USGS Circular 1292. Available on the
Internet at: http://pubs.usgs.gov/circ/circl292/pdf/circularl292.pdf.
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Chapter 3:
PFOS
A chapter from:
Final Regulatory Determination 4 Support Document
EPA Report 815-R-21-001
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Contents
Contents 3-2
Exhibits 3-3
Abbreviations 3-4
3.1 Contaminant Background, Chemical and Physical Properties 3-6
3.2 Sources and Environmental Fate 3-9
3.2.1. Production, Use, and Release 3-9
3.2.2. Environmental Fate 3-10
3.3 Health Effects 3-11
3.4 Occurrence 3-12
3.4.1. Occurrence in Ambient Water 3-13
3.4.2. Occurrence in Drinking Water 3-14
3.4.3. Other Data 3-35
3.4.4. Combined PFOS and PFOA and Other Co-Occurrence Analyses 3-36
3.5 Analytical Methods 3-51
3.6 Treatment Technologies 3-52
3.7 References 3-53
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Exhibits
Exhibit 3-1: Chemical Structure of PFOS 3-8
Exhibit 3-2: Physical and Chemical Properties of PFOS 3-8
Exhibit 3-3: IUR Reported Annual Manufacture and Importation of PFOS in the United
States, 1986-2006 (pounds) 3-10
Exhibit 3-4: PFOS Occurrence Data from UCMR 3 Assessment Monitoring - Summary of
Detected Concentrations 3-16
Exhibit 3-5: PFOS National Occurrence Measures Based on UCMR 3 Assessment Monitoring
Data - Summary of Samples 3-16
Exhibit 3-6: PFOS National Occurrence Measures Based on UCMR 3 Assessment Monitoring
Data - Summary of System and Population Served Data — Detections 3-17
Exhibit 3-7: PFOS National Occurrence Measures Based on UCMR 3 Assessment Monitoring
Data - Summary of System and Population Served Data — Detections > '/2 HRL (0.035
ug/I.) 3-18
Exhibit 3-8: PFOS National Occurrence Measures Based on UCMR 3 Assessment Monitoring
Data - Summary of System and Population Served Data - Detections > HRL (0.07
ug/I.) 3-19
Exhibit 3-9: Summary of Available Primary State Monitoring Data 3-20
Exhibit 3-10: PFOS Primary State Drinking Water Occurrence Data - Summary of Detected
Concentrations 3-23
Exhibit 3-11: PFOS Primary State Drinking Water Occurrence Data - Summary of Samples 3-25
Exhibit 3-12: PFOS Primary State Drinking Water Occurrence Data - Summary of Systems 3-27
Exhibit 3-13: Summary of New York State PFOA-PFOS Sampling Results 3-33
Exhibit 3-14: Drinking Water Treatment Plants - Summary of PFOS Samples (Glassmeyer et
aL 2017) 3-34
Exhibit 3-15: 95th Percentiles of Serum PFOS Concentrations, 1999-2000 and 2003-2016 3-35
Exhibit 3-16: PFOS+PFOA Occurrence Data from UCMR 3 Assessment Monitoring -
Summary of Concentrations 3-37
Exhibit 3-17: PFOS+PFOA National Occurrence Measures Based on UCMR 3 Assessment
Monitoring Data - Summary of Samples 3-37
Exhibit 3-18: PFOS+PFOA National Occurrence Measures Based on UCMR 3 Assessment
Monitoring Data - Summary of System and Population Served Data — Detections 3-38
Exhibit 3-19: PFOS+PFOA National Occurrence Measures Based on UCMR 3 Assessment
Monitoring Data - Summary of System and Population Served Data — Concentrations
> Vi HRL (0.035 ug/I.) 3-39
Exhibit 3-20: PFOS+PFOA National Occurrence Measures Based on UCMR 3 Assessment
Monitoring Data - Summary of System and Population Served Data — Concentrations
> HRL (0.07 ug/I.) 3-40
Exhibit 3-21: PFOS+PFOA State Drinking Water Occurrence Data - Summary of
Concentrations 3-41
Exhibit 3-22: PFOS+PFOA State Drinking Water Occurrence Data - Summary of Samples.. 3-43
Exhibit 3-23: PFOS+PFOA State Drinking Water Occurrence Data - Summary of Systems.. 3-46
Exhibit 3-24: Co-Occurrence Matrix (Odds Ratios for Association Between PFAS Pairs) 3-50
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Abbreviations
ADEQ
Arizona Department of Environmental Quality
Alaska DEC
Alaska Department of Environmental Conservation
BW
Body Weight
CAS
Chemical Abstracts Service
CCL 4
Fourth Contaminant Candidate List
CDC
Centers for Disease Control and Prevention
CDPHE
Colorado Department of Public Health and Environment
CDR
Chemical Data Reporting
DNR
Department of Natural Resources
DWI
Drinking Water Intake
EPA
Environmental Protection Agency
EPISuite™
Estimation Programs Interface Suite™
GAEPD
Georgia Environmental Protection Division
GAC
Granular Activated Carbon
GWUDI
Groundwater Under the Direct Influence of Surface Water
HA
Health Advisory
HDL
High-Density Lipoprotein
HRL
Health Reference Level
HSDB
Hazardous Substances Data Bank
Iowa ANG
Iowa Air National Guard
Iowa DNR
Iowa Department of Natural Resources
IUR
Inventory Update Reporting
Kh
Henry's Law Constant
Koc
Organic Carbon Partitioning Coefficient
Kow
Octanol-Water Partitioning Coefficient
LC/MS/MS
Liquid Chromatography/Tandem Mass Spectrometry
LCMRL
Lowest Concentration Minimum Reporting Level
LOD
Limit of Detection
MDH
Minnesota Department of Health
Michigan EGLE
Michigan Department of Environment, Great Lakes, and Energy
MP ART
Michigan PFAS Action Response Team
MPCA
Minnesota Pollution Control Agency
MRL
Minimum Reporting Level
Missouri DNR
Missouri Department of Natural Resources
NAWQA
National Water-Quality Assessment
ND
No Detection
NDEQ
Nebraska Department of Environmental Quality
Nebraska DHHS
Nebraska Department of Health and Human Services
NHANES
National Health and Nutrition Examination Survey
NHDES
New Hampshire Department of Environmental Services
NIRS
National Inorganics and Radionuclides Survey
NJDEP
New Jersey Department of Environmental Protection
NPDWR
National Primary Drinking Water Regulation
NYS
New York State
NYSDOH
New York State Department of Health
PFAA
Perfluorinated Alkyl Acid
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PFAS
Per- and Polyfluoroalkyl Substances
PFBS
Perfluorobutane Sulfonate
PFCA
Perfluoroalkyl Carboxylate
PFHpA
Perfluoroheptanote
PFHxS
Perfluorohexane Sulfonate
PFNA
Perfluorononanoate
PFOA
Perfluorooctanoic Acid
PFOS
Perfluorooctanesulfonic Acid
PFSA
Perfluoroalkyl Sulfonate
pKa
Acid Dissociation Constant
PWS
Public Water System
QA
Quality Assurance
RfD
Reference Dose
RIDOH
Rhode Island Department of Health
RSD
Relative Standard Deviation
SDWIS/Fed
Safe Drinking Water Information System/Federal Version
SNUR
Significant New Use Rule
STORET
Storage and Retrieval Data System
TOC
Total Organic Carbon
TRI
Toxics Release Inventory
TSCA
Toxic Substances Control Act
UCM
Unregulated Contaminant Monitoring
UCMR
Unregulated Contaminant Monitoring Rule
UCMR 1
First Unregulated Contaminant Monitoring Rule
UCMR 2
Second Unregulated Contaminant Monitoring Rule
UCMR 3
Third Unregulated Contaminant Monitoring Rule
USGS
United States Geological Survey
UV
Ultraviolet
VT DEC
Vermont Department of Environmental Conservation
WQP
Water Quality Portal
WTP
Water Treatment Plant
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Chapter3: PFOS
The Environmental Protection Agency (EPA) is evaluating perfluorooctanesulfonic acid
(PFOS) as a candidate for regulation as a drinking water contaminant under the fourth
Contaminant Candidate List (CCL 4) Regulatory Determinations process. Information on the
CCL 4 process is found in Chapter 1. Background on data sources used to evaluate CCL 4
chemicals is found in Chapter 2.
This chapter presents information and analysis specific to PFOS, including background
information on the contaminant, information on contaminant sources and environmental fate, an
analysis of health effects, an analysis of occurrence in ambient and drinking water, and
information about the availability of analytical methods and treatment technologies.
3.1 Contaminant Background, Chemical and Physical Properties
Synonyms for PFOS include perfluorooctylsulfonic acid and
heptadecafluorooctanesulfonic acid. The acronym PFOS is also used to refer to the deprotonated
anionic form of the compound, perfluorooctane sulfonate, according to the Hazardous
Substances Data Bank (HSDB, 2016). PFOS belongs to a group of substances known as per- and
polyfluoroalkyl substances (PFAS).
PFOS is a perfluorinated aliphatic sulfonic acid. It has been used as a surfactant or
emulsifier in firefighting foam, circuit board etching acids, alkaline cleaners, and floor polish;
and as a pesticide active ingredient for insect bait traps (HSDB, 2016). The sole U.S.
manufacturer of PFOS agreed to a voluntary phaseout in 2000, and the last reported production
was in 2002 (USEPA, 2000; USEPA, 2018a). There are some limited ongoing uses of PFOS and
PFOS precursors (40 CFR § 721.9582). It is possible that some of these compounds, notably the
salt tetraethylammonium perfluorooctanesulfonate as a fume/mist suppressant in metal finishing
and plating baths, may result in the presence of PFOS (e.g., as its anionic sulfonate) in the
environment.
EPA issued a Significant New Use Rule (SNUR) in 2002 on PFOS and PFOS-related
chemical substances, and amended it in 2002, 2007, and 2013 (67 FR 11007, USEPA, 2002a; 67
FR 72854, USEPA, 2002b; 72 FR 57222, USEPA, 2007; 78 FR 62443, USEPA, 2013). The
SNUR requires notification of EPA in advance of proposed manufacture or importation of PFOS
and over 200 related substances. The 2007 Federal Register notice provides exemptions for
limited specific existing uses of PFOS-related compounds, including use as anti-erosion
additives in fire-resistant aviation hydraulic fluids, several uses in the manufacture of electronics,
use as fume/mist suppressant in metal finishing and plating baths, and generation as an
intermediate when producing other chemicals for such exempted applications. Such uses of
related compounds (e.g., tetraethylammonium perfluorooctanesulfonate) may still be associated
with the introduction of PFOS into the environment, and EPA indicated in 2007 that the Agency
intended to "continue to work with state agencies and industry to identify best management
practices for minimizing the release of this PFAS surfactant" (72 FR 57222; USEPA, 2007).
In 2013, EPA issued a SNUR requiring companies to report all new uses of certain
PFOA-related chemicals as part of carpets. The 2013 action expanded the scope of previous
PFAS SNURs to cover PFAS chemical substances that have completed the Toxic Substances
Control Act (TSCA) new chemical review process but have not yet commenced production or
import, and designated processing as a significant new use (78 FR 62443, USEPA, 2013). In
2015, EPA issued amendments to the SNUR on PFOA and PFOA-related chemicals, which
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included notice requirements for certain PFOA-related compounds as part of articles (80 FR
2885, USEPA, 2015). EPA finalized the 2015 SNUR amendments in 2020 (EPA-HQ-OPPT-
2013-0225, USEPA, 2020a). The 2020 final SNUR gives EPA the authority to review an
extensive list of products containing PFAS before they are manufactured, sold, or imported in the
United States. The final rule requires notice and EPA review prior to the new use of long-chain
PFAS that have been nationally phased out, thus strengthening the regulation of PFAS. In
addition, products that contain particular long-chain PFAS as a surface coating and carpet
containing perfluoroalkyl sulfonate chemical substances must undergo EPA review to be
imported into the United States). Concern remains about a limited number of ongoing uses of
PFOA-related chemicals, which are still available in existing stocks and from companies not
participating in the PFOA Stewardship Program. In addition, exposure could occur via goods
imported from countries where PFOS and PFOA are still used (USEPA, 2017a).
PFOS has been detected in up to 98% of serum samples taken in biomonitoring studies
that are representative of the U.S. general population. Since PFOS production ceased in the U.S.,
serum concentrations in the U.S. population have been declining (CDC, 2019). National Health
and Nutrition Examination Survey (NHANES) data show that 95th-percentile serum PFOS
concentrations have decreased from 75.7 |ig/L in the 1999-2000 cycle to 18.3 |ig/L in the 2015-
2016 cycle (CDC 2019; Jain, 2018; Calafat et al., 2007; Calafat et al., 2019). NHANES
biomonitoring data are discussed further in section 3.4.3.
PFOS may also be formed in the environment as a terminal degradation product of
commercial PFAS produced by electrochemical fluorination. Perfluorooctane sulfonyl fluoride
and A-alky 1 sulfonamido PFAS such as TV-methyl perfluorooctanesulfonamido ethanol and TV-
ethyl perfluorooctanesulfonamido ethanol are used to produce surfactants and polymers that may
degrade to PFOS (ITRC, 2020a; ITRC, 2020b; Buck et al., 2011).
The diagram in Exhibit 3-1 shows the straight-chain chemical structure of PFOS. PFOS
and related compounds can exist as either branched-chain or straight-chain isomers depending on
their method of manufacture (ATSDR, 2018). Physical and chemical properties and other
reference information are listed in Exhibit 3-2 (these properties typically represent mixtures of
branched and linear isomers rather than any particular isomer). There is uncertainty as to whether
values for certain physical/chemical properties of PFOS can be measured or estimated. For
example, HSDB (2016) reports a value for the log octanol/water partitioning coefficient (log
Kow) that is estimated using EPA's Estimation Programs Interface Suite™ (EPISuite™), while
ATSDR (2018) and Lange et al. (2006) indicate that log Kow is not applicable or cannot be
measured since PFOS is expected to form multiple layers in octanol and water mixtures. While
uncharged and very long-chain perfluoroalkyls form layers in water/hydrocarbon mixtures,
forms that are charged/ionized at typical environmental pH (such as PFOS) are fairly soluble in
water (ATSDR, 2018). Another example of apparent uncertainty is the Henry's Law Constant
(Kh). HSDB (2016) presents two values for Kh for PFOS, while ATSDR (2018) indicates that no
data are available for this property. HSDB states that one value for Kh, which is quite small,
effectively indicates that the anion of PFOS is not volatile in aqueous media. The second value
for Kh is substantially larger than the first but was estimated from vapor pressure and water
solubility using EPISuite™; thus, this value likely does not take into account the low pKa, which
may attenuate the effects of vapor pressure.
PFOS is a perfluorinated alkyl acid (PFAA) that exists as its sulfonate anion at typical
environmental pH values. Physical and chemical property data for various PFAS often
correspond to the protonated acid form of the compound in contrast to the deprotonated anion
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(ITRC, 2020a). Thus, the available physical and chemical property data for PFOS may not be
representative of how PFOS partitions in the environment.
In cases where there are different conclusions in the literature, information describing
differences is presented to highlight the uncertainty in this area.
Exhibit 3-1: Chemical Structure of PFOS
Exhibit 3-2: Physical and Chemical Properties of PFOS
Property
Data
Chemical Abstracts Service (CAS)
Registry Number
1763-23-1 (ChemlDPIus, 2019)
EPA Pesticide Chemical Code
Not Applicable
Chemical Formula
CsHFi/OsS (ChemlDPIus, 2019)
Molecular Weight
500.13 g/mol (HSDB, 2016)
Color/Physical State
Liquid (HSDB, 2016)
Boiling Point
249 deg C (HSDB, 2016)
Melting Point
>400 deg C (ATSDR, 2018; potassium salt)
Density
-
Freundlich Adsorption Coefficient
25.1 in clay, 14.0 in clay loam, 28.2 in sandy loam, 8.70 in river
sediment (HSDB, 2016)
Vapor Pressure
0.002 mm Hg at 25 deg C (est) (HSDB, 2016)
Henry's Law Constant (Kh)
4.1E-04 atm-m3/mol at 25 deg C (HSDB, 2016)
<4.9E-09 atm-m3/mol (HSDB, 2016)
No data (ATSDR, 2018)
Log Kow
4.49 (est) (dimensionless) (HSDB, 2016)
Cannot be measured (Lange et al., 2006)
Not applicable (ATSDR, 2018)
Koc
1,000 ±5.0 L/kg (mean of values ±1 standard deviation from
Zareitalabad et al., 2013; converted from log Koc to Koc)
pKa
<1.0 (HSDB, 2016)
Solubility in Water
0.0032 mg/L at 25 deg C (est) (HSDB, 2016)
570 mg/L (ATSDR, 2018; potassium salt in pure water)
Other Solvents
-
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Property
Data
Conversion Factors
(at 25 deg C, 1 atm)
-
Note:" indicates that no information was found.
3.2 Sources and Environmental Fate
3.2.1 Production, Use, and Release
Production data for PFOS are available from EPA's Inventory Update Reporting (IUR)
and Chemical Data Reporting (CDR) programs, described below.
No industrial release data are available from EPA's Toxics Release Inventory (TRI). (The
list of chemicals for which TRI reporting is required has never included PFOS (USEPA, 2016a.)
Inventory Update Reporting (IUR) / Chemical Data Reporting (CDR) Program
Under the authority of the TSCA, EPA gathers information on production (including both
manufacture and importation) of industrial chemicals. Under the IUR, producers provided
information once every four years from 1986 to 2006. Since 2012, producers have continued to
provide information in accordance with the CDR Rule that superseded the IUR in 2011. Under
CDR, producers collect annual production data and report it once every four years. Production of
PFOS is subject to CDR reporting.
Until 2006, the IUR regulation required manufacturers and importers of organic chemical
substances included on the TSCA Chemical Substance Inventory to report site and
manufacturing information for chemicals produced (i.e., manufactured or imported) in amounts
of 10,000 pounds or more at a single site. In 2006, the minimum threshold for reporting was
increased to 25,000 pounds and reporting began for inorganic chemicals (USEPA, 2008). Among
changes made under CDR, a two-tier system of reporting thresholds was implemented, with
25,000 pounds as the threshold for some contaminants and 2,500 pounds as the threshold for
others (USEPA, 2014; USEPA, 2018b). As a compound with a TSCA section 5(a)(2) SNUR,
PFOS is among those to which the 2,500 pound threshold applies. As a result of program
modifications, the results from 2006 and later might not be directly comparable to results from
earlier years. Under CDR, every four years manufacturers and importers are required to report
annual data from each of the previous four years, provided that the thresholds of 2,500 or 25,000
pounds are met during at least one of the four years (USEPA, 2018b).
For the historical IUR data, EPA assigned one of eight production volume ranges for
each chemical included in the inventory. The ranges used for the 2006 reports differ slightly
from those used in the 1986 through 2002 reports, as described in Chapter 2. Exhibit 3-3 presents
the publicly available information on production of PFOS in the United States from 1986 to 2006
as reported under IUR. Production did not exceed 500,000 pounds in any year with reported data.
No data were reported in 1986, 1990, 1998, or 2006. PFOS was phased out by 3M in 2002 and
the most recently reported data for PFOS are from the 2002 reporting cycle (which includes
production information from 2001 only).
Although PFOS is subject to CDR reporting, there are no reports of manufacture or
importation in the CDR dataset (USEPA, 2018b). Absence of recent reporting may indicate that
production (including import) of PFOS has halted or has been below the CDR reporting
thresholds. Although PFOS are not produced domestically or imported by the companies
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participating in the 2010/2015 PFOA Stewardship Program, PFOS may still be produced
domestically or imported below the CDR reporting thresholds by companies not participating in
the PFOA Stewardship Program.
Exhibit 3-3: IUR Reported Annual Manufacture and Importation of PFOS in the
United States, 1986-2006 (pounds)
Reporting Cycle
1986
1990
1994
1998
2002
2006
Range of
Production
Volume
No Reports
No Reports
10,000-
500,000
No Reports
10,000-
500,000
No Reports
Source: USEPA, 2008
3.2.2 Environmental Fate
As discussed in Chapter 2, the primary measures used by EPA to assess mobility include
(where available) the organic carbon partitioning coefficient (Koc), log Kow, Kh, water solubility
and vapor pressure. For PFOS, the log of the acid dissociation constant (pKa) is also important.
Modeling of atmospheric behavior at a vapor pressure of 0.002 mm Hg at 25 degrees C
suggest that PFOS will be present as a vapor if released to the atmosphere (HSDB, 2016). PFOS
can react with photochemically produced hydroxyl radicals in the atmosphere to degrade
(HSDB, 2016). A half-life for this reaction in air is estimated to be 115 days, based on a structure
estimation method (HSDB, 2016). (Note that radical reactions typically proceed more rapidly
than chemically- or microbially-mediated degradation reactions in other environmental media
such as water, soil, and/or sediment.) PFOS is not expected to undergo direct photolysis (HSDB,
2016).
Based on findings from laboratory studies, Zareitalabad et al. (2013) calculate an average
log Koc of 3.0 ±0.7, equivalent to a Koc of 1,000 ±5.0 L/kg, which suggests a propensity for PFOS
to be mobilized to groundwater and surface water rather than to bind to suspended solids or
sediments. The authors note that field studies indicate a greater propensity for PFOS to bind to
soil and sediment than the lab-derived Koc values would predict.
Based on the vapor pressure, PFOS is not expected to volatilize from dry soil (HSDB,
2016). With a pKa of <1.0 (HSDB, 2016), PFOS is expected to exist in its ionized form at typical
environment pH ranges of natural waters (HSDB, 2016; Lange et al., 2006). Thus, volatilization
from water at typical environment pH is not expected (HSDB, 2016).
PFOS is very stable chemically and is resistant to hydrolysis, photolysis, and
biodegradation (HSDB, 2016; Lange et al., 2006). Washington et al. (2010) found that PFOS had
a modeled disappearance half-life of 1.2 years in sludge-applied soils near Decatur, Alabama.
Washington et al. (2010) noted that this disappearance half-life is the time over which PFOS
concentration in the surface soil was diminished by half due to all environmental processes:
these processes could potentially include uptake into plants (c.f. Yoo et al., 2011), erosion,
leaching, ingrowth from precursors, and degradation. Washington et al. (2010) posits that among
these possible processes, leaching was likely a leading mode of loss. However, the chemical
stability of PFOS is much longer than this modeled disappearance half-life. Additionally, labile
PFAS precursors commonly present in sludge may degrade in soil settings, leading to ingrowth
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of recalcitrant PFAS such as PFOS, perfluorooctanoic acid (PFOA), and related compounds
(Wang et al., 2009; Martin et al., 2010; Washington et al., 2014; Washington et al., 2015).
Chapter 2 presents scales used by EPA to informally rank chemical contaminants' likely
mobility (understood as their tendency to partition to water rather than other media) and
persistence as "high," "moderate," or "low" based on physical and chemical properties (see
Exhibit 2-2 and Exhibit 2-3).For PFOS, a Kh of <4.9E-09 atm-m3/mol, a log Kow of 4.49, and a
water solubility of 0.0032 mg/L at 25 degrees C predict a low likelihood of partitioning to water.
The water solubility of the potassium salt of PFOS, 570 mg/L, which may be more indicative of
the anionic form that occurs at typical environmental pH, predicts a moderate likelihood of
partitioning to water. HSDB (2016) also lists a Kh of 4.1E-04 atm-m3/mol, but this value was
estimated from vapor pressure and water solubility using EPISuite™; thus, this value likely does
not take into account the low pKa, which may attenuate the effects of vapor pressure. A Koc value
of 1,000 ±5.0 L/kg predicts a moderate likelihood of partitioning to water. A resistance to
essentially all forms of degradation other than atmospheric processes indicates high persistence.
3.3 Health Effects
In 2016, EPA published health assessments for PFOA and PFOS based on the Agency's
evaluation of the latest peer reviewed science. For more specific details on the potential for
adverse health effects and approaches used to identify and evaluate information on hazard and
dose-response, please see USEPA (2016b) and USEPA (2016c).
In brief: epidemiological studies have reported associations between PFOS exposure and
both high serum cholesterol and reproductive and developmental parameters. The strongest
associations are related to serum lipids with increased total serum cholesterol and high-density
lipoproteins (HDLs). Human epidemiological studies suggest an association between higher
PFOS levels and decreases in female fecundity and fertility, decreased birth weights in offspring,
and other measures of postnatal growth (e.g., small for gestational age).
Short-term and chronic exposure studies in animals demonstrate increases in liver weight
consistently. Co-occurring effects in these studies include decreased cholesterol, hepatic
steatosis, lower body weight, and liver histopathology. One and two generation toxicity studies
also show decreased pup survival and body weights. Additionally, developmental neurotoxicity
studies show increased motor activity and decreased habituation and increased escape latency in
the water maze test following in utero and lactational exposure to PFOS. Gestational and
lactational exposures were also associated with higher serum glucose levels and evidence of
insulin resistance in adult offspring. Limited evidence suggests immunological effects in mice.
Short-term and subchronic duration studies are available in multiple animal species including
monkeys, rats, and mice. These studies also found increased serum glucose levels and insulin
resistance in adult animals exposed during development, developmental effects (decreased body
weight and survival), reproductive effects (impacts on mating behavior), liver toxicity (increased
liver weight co-occurring with decreased serum cholesterol, hepatic steatosis), developmental
neurotoxicity (impaired spatial learning and memory), suppressed immunological responses, and
cancer (thyroid and liver). Increased incidence of hepatocellular adenomas in the male (12% at
the high dose) and female rats (8% at the high dose) and combined adenomas/carcinomas in the
females (10% at the high dose) were observed, but they did not display a clear dose-related
response; Thyroid tumors (adenomas and carcinomas) were seen in males receiving 0, 0.5, 2, 5,
or 20 ppm and in females receiving 5 or 20 ppm in their diet. The tumor (adenomas +
carcinomas) prevalence for males was consistent across dose groups. In males the incidence of
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thyroid tumors was significantly elevated only in the high-dose, recovery group males exposed
for 52 weeks (10/39) but not in the animals receiving the same dose at 105 weeks. There were
very few follicular cell adenomas/carcinomas in the females (5 total) with no dose-response. The
most frequent thyroid tumor type in the females was C-cell adenomas, but the highest incidence
was that for the controls and there was a lack of dose response among the exposed groups. C-cell
adenomas were not observed in males (Thomford, 2002; Butenhoff et al., 2012). Overall, the
animal toxicity studies available for PFOS demonstrate that the developing fetus and newborn
rodent are sensitive to PFOS induced toxicity. PFOS is known to be transmitted to the fetus via
the placenta and to the newborn, infant, and child via breast milk (USEPA, 2016b).
Applying EPA's Guidelines for Carcinogen Risk Assessment (USEPA, 2005), there is
"suggestive evidence of carcinogenic potential" for PFOS. However, the weight of evidence for
humans is too limited to support a quantitative cancer assessment given that there was no
evidence for dose-response from which to derive a slope factor for the tumor types identified in
animals.
EPA calculated multiple candidate reference doses (RfDs) for PFOS in the Health Effects
Support Document (USEPA, 2016b) and selected the RfD of 0.00002 mg/kg/day based on
decreased neonatal rat body weight from both the one- and two-generation studies by Luebker et
al. (2005a; 2005b) for the derivation of a lifetime health advisory (HA). The RfD for PFOS was
calculated by applying uncertainty factors to account for interspecies variability (3) and
intraspecies differences (10). The Health Effects Support Document (USEPA, 2016b) describes
these uncertainties in Section 4. Additionally, uncertainties and limitations (i.e., human
epidemiologic data, immunological and mammary gland endpoints, and exposure) are discussed
in detail in Section 8 of the Health Advisory (USEPA, 2016c) document. The lifetime HA of
0.07 |ig/L was calculated using the 0.00002 mg/kg/day RfD for developmental effects, a
drinking water intake (DWI) to body weight (BW) ratio of 0.054 L/kg/day for the 90th percentile
for lactating women,1 and a 20 percent relative source contribution (USEPA, 2016c). The
lifetime HA of 0.07 |ig/L is used as the Health Reference Level (HRL) for Regulatory
Determination 4.
The RfDs for both PFOA and PFOS are based on similar developmental effects and are
numerically identical. Thus, when both chemicals co-occur at the same time and location, EPA
recommended a conservative and health-protective approach of 0.07 |ig/L for the PFOA/PFOS
total combined concentration (USEPA, 2016c).
EPA has initiated a systematic literature review of peer-reviewed scientific literature for
PFOA and PFOS published since 2013 with the goal of identifying any new studies that may be
relevant to human health assessment. An annotated bibliography of identified studies as well as
the protocol used to identify the relevant publications can be found in Appendix D.
3.4 Occurrence
This section presents data on the occurrence of PFOS in ambient water and drinking
water in the United States. As described in section 3.3, an HRL of 0.07 |ig/L was calculated for
PFOS based on non-carcinogenic effects. HRLs are risk-derived concentrations against which to
evaluate the occurrence data to determine if contaminants occur at levels of potential public
health concern. Occurrence data from various sources presented below are analyzed with respect
1 Consumers only estimate of combined direct and indirect community water ingestion; see Table 3-81 in USEPA
(2011).
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to the HRL and one-half the HRL. When possible, estimates of the population exposed at
concentrations above the HRL and one-half the HRL are presented. Also, when possible, studies
that are meant to be representative and studies that are targeted at known or suspected sites of
contamination are identified as such.
This section also presents occurrence analyses for combined PFOS and PFOA
concentrations against their common HRL of 0.07 |ig/L in cases where such analyses could be
performed (i.e., when a data source provides both PFOS and PFOA results for the same sample).
The analyses were performed for the third Unregulated Contaminant Monitoring Rule (UCMR 3)
and select state data sources. In addition, this section presents PFOS and PFOA findings from
UCMR 3 analyses conducted by non-EPA researchers.
For additional background information about data sources used to evaluate occurrence,
please refer to Chapter 2.
3.4.1 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the ambient sources of most drinking water. Contaminant
occurrence in ambient water provides information on the potential for contaminants to adversely
affect drinking water supplies. Occurrence data for PFOS in ambient water are not available
from the United States Geological Survey (USGS) National Water-Quality Assessment
(NAWQA). EPA's legacy Storage and Retrieval Data System (STORET) data available through
the Water Quality Portal (WQP) do contain some PFOS sampling data; however, none of those
results passed EPA's standard set of quality assurance (QA) filters used in the analysis of
STORET data for regulatory determination as they were all listed as wastewater effluent
samples. Thus, those data are not included in this report. Occurrence data for PFOS in ambient
water are available from several published studies summarized below.
Additional Ambient Water Studies
PFOS was detected in a number of additional ambient water studies conducted in
different parts of the United States and Canada. Hansen et al. (2002) conducted testing in
Decatur, Alabama for the presence of fluorochemicals along an approximately 80-mile reach of
the Tennessee River located near and downstream of a manufacturing facility for perfluorinated
compounds and the Decatur Wastewater Treatment Plant. The reporting level used for PFOS in
this study was 0.005 |ig/L. Forty ambient water samples were collected, and PFOS was detected
in all 40 samples (100 percent). Concentrations of PFOS ranged from 0.0168 |ig/L to 0.144
|ig/L, with a median concentration of 0.0523 |ig/L (Hansen et al., 2002).
Boulanger et al. (2004) analyzed samples from four locations in Lake Erie and four
locations in Lake Ontario. The locations were selected to represent urban-influenced and remote
locations, as well as the geographical limits of each lake. Samples were collected and analyzed in
duplicate from each location (total of 16 samples). PFOS was detected in all 16 samples (100
percent). The limit of quantification for PFOS in this study was 0.0007 |ig/L. Concentrations of
PFOS ranged from 0.011 |ig/L to 0.121 |ig/L, with a median concentration of 0.0365 |ig/L
(Boulanger et al., 2004).
A study conducted in 2008 by EPA in conjunction with several state agencies provides
information about the occurrence of 13 perfluorinated compounds in surface water from an
approximately 2,000 km reach of the Mississippi River and major tributaries. This study
involved the collection of 173 ambient water samples from 88 locations in and in close proximity
to the upper Mississippi River basin and was 0.00002 |ig/L. PFOS was detected in 168 (97.1
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percent) of the samples, with 71 percent having PFOS concentrations at or above the Level of
Quantitation of 0.001 |ig/L. The median concentration of PFOS was 0.00301 |ig/L, the 90th
percentile concentration was 0.017 |ig/L, and the maximum concentration, was 0.245 |ig/L
(Nakayama et al., 2010).
Konwick et al. (2008) measured concentrations of PFOS in a river and a pond near a land
application site for wastewater sludge in Georgia near the site of North America's largest carpet
manufacturing site, along with concentrations in a stream located away from the land application
site. Concentrations of PFOS in the stream near the land application site ranged from 0.192 |ig/L
to 0.318 |ig/L. The concentrations in the pond near the land application site were lower, ranging
from 0.015 |ig/L to 0.12 |ig/L. Concentrations away from the land application site ranged from
0.0026 |ig/L to 0.0027 |ig/L.
USGS (2011) measured PFOS concentrations at outfall locations of 11 waste water
treatment plants in Maryland and Washington D.C. from June to August 2010. PFOS was
detected in 8 of the 11 samples; detected concentrations ranged 0.004 to 0.027 |ig/L.
3.4.2 Occurrence in Drinking Water
Data sources reviewed by the Agency for information on contaminant occurrence in
drinking water included: EPA's first, second, and third Unregulated Contaminant Monitoring
Rules (UCMR 1, UCMR 2, UCMR 3); Rounds 1 and 2 of the Agency's Unregulated
Contaminant Monitoring (UCM) program that preceded the Unregulated Contaminant
Monitoring Rule (UCMR); EPA's Information Collection Rule; EPA's National Inorganics and
Radionuclides Survey (NIRS); and a range of others as discussed in Chapter 2. Among the
sources reviewed, the following had data and information on PFOS occurrence in drinking water.
These data and information are discussed in this section.
• EPA's Third Unregulated Contaminant Monitoring Rule (UCMR 3).
State drinking water monitoring programs.
USGS source water and drinking water studies.
Additional studies from the literature.
Note that there may be some overlap, as sources with different purposes and audiences
may have reported the same underlying data. UCMR 3 is a nationally representative data source.
Other data sources profiled in this section are considered "supplemental" sources.
Primary Data Sources
EPA's Third Unregulated Contaminant Monitoring Rule (UCMR 3)
UCMR 3 monitoring, designed to provide nationally representative contaminant
occurrence data, was conducted from 2013 through 2015. UCMR 3 List 1 Assessment
Monitoring occurrence data are available for PFOS. For UCMR 3, all large and very large public
water systems or PWSs (serving between 10,001 and 100,000 people and serving more than
100,000 people, respectively), plus a statistically representative national sample of 800 small
PWSs (serving 10,000 people or fewer), were required to conduct Assessment Monitoring during
a 12-month period between January 2013 and December 2015.2 Surface water (and groundwater
2 A total of 799 small systems submitted Assessment Monitoring results.
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under the direct influence of surface water (GWUDI)) sampling points were monitored four
times during the applicable year of monitoring, and groundwater sample points were monitored
twice during the applicable year of monitoring. See USEPA (2012) and USEPA (2019b) for
more information on the UCMR 3 study design and data analysis.
The design of UCMR 3 permits estimation of national occurrence by multiplying the total
number of systems (or population served) in the nation in a system size category by the percent
of systems expected to exceed a specified threshold. An extrapolation methodology is applied to
small systems because not all small systems were required to participate in the UCMR 3
Assessment Monitoring. Because all large and very large systems were required to participate in
the UCMR 3 Assessment Monitoring, national estimates of occurrence in these size categories
can be done using survey census figures rather than extrapolation. Total national occurrence is
estimated by summing the extrapolated figures for small systems and the census figures for the
large and very large systems.
Exhibit 3-4 through Exhibit 3-8 provide an overview of PFOS occurrence results from
the UCMR 3 Assessment Monitoring. Laboratories participating in UCMR 3 were required to
report values at or above minimum reporting levels (MRLs) defined by EPA. The MRLs are
established to ensure reliable and consistent results from the array of laboratories needed for a
national monitoring program and are set based on the capability of multiple commercial
laboratories prior to the beginning each UCMR round. The MRL used for PFOS in the UCMR 3
survey was 0.04 |ig/L (77 FR 26072; USEPA, 2012). Exhibit 3-4 shows a statistical summary of
PFOS concentrations by system size and source water type (including the minimum, median, 90th
percentile, 99th percentile, and maximum). Exhibit 3-5 presents a sample-level summary of the
results. Exhibit 3-6 through Exhibit 3-8 show system-level results, including national
extrapolations, at three thresholds: detections, one-half the HRL, and the HRL. Detections are
evaluated on a "greater than or equal to" basis (> the MRL), while health-based thresholds are
evaluated in terms of exceedances (> one-half HRL, and > HRL).
As noted above, UCMR 3 monitoring was required at a nationally representative sample
of small systems and at all large and very large systems. (Note that small systems selected to
monitor under UCMR 3 may not be representative of small systems located near potential PFOS
sources.) As a reminder that the figures from large and very large systems represent a census of
systems in those categories, results in those categories are labelled "CENSUS" in Exhibit 3-4
through Exhibit 3-8. No extrapolation was necessary in these categories, as it was for the small
systems, to derive national estimates of occurrence in these exhibits. National estimates of
occurrence are reported separately in each system size and source water category, and also in
aggregate.
A total of 36,972 finished water samples for PFOS were collected from 4,920 PWSs.
PFOS was measured > MRL in 0.79 percent of UCMR 3 samples. Reported PFOS
concentrations for these "positive" results ranged from 0.04 |ig/L (the MRL) to 7 |ig/L. Of 4,920
systems, 95 (1.9 percent of systems, serving 4.3 percent of the PWS-served population) reported
at least one detection. Since the MRL for PFOS was equal to 0.04 |ig/L, all detections were
greater than one-half the HRL of 0.035 |ig/L. A total of 46 PWSs (0.9 percent of PWSs, serving
1.6 percent of the PWS-served population) reported at least one detection greater than the HRL
of 0.07 |ig/L. Extrapolating these findings suggests that an estimated 304 PWSs serving 10.8
million people nationally would have at least one PFOS detection greater than one-half the HRL
and an estimated 151 PWSs serving 3.8 million people nationally would have at least one PFOS
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detection greater than the HRL. (See Section 3.4.4, including Exhibit 3-16 through Exhibit 3-20,
for a presentation of UCMR 3 occurrence results for combined PFOS plus PFOA.)
Exhibit 3-4: PFOS Occurrence Data from UCMR 3 Assessment Monitoring -
Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (in |jg/L)
> MRL of 0.04 ug/L
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Small Systems (serving < 10,000 people)
Groundwater
0.23
0.27
0.29
0.30
0.3
Surface Water
0.05
0.05
0.06
0.06
0.05853
All Small Systems
0.05
0.06
0.27
0.30
0.3
Large Systems (serving 10,001 -100,000 people) — CENSUS
Groundwater
0.04
0.06
0.24
0.54
0.60
Surface Water
0.04
0.07
0.37
3.57
7
All Large Systems
0.04
0.06
0.28
1.29
7
Very Large Systems (serving > 100,000 people) — CENSUS
Groundwater
0.041
0.09
0.34
0.50
0.53
Surface Water
0.041
0.05
0.11
1.35
1.8
All Very Large Systems
0.041
0.05
0.18
1.10
1.8
All Systems
All Water Systems
0.04
0.06
0.25
1.34
7
Source: USEPA, 2017b
Exhibit 3-5: PFOS National Occurrence Measures Based on UCMR 3 Assessment
Monitoring Data - Summary of Samples
Source Water Type
Total # of
Samples
Samples with
Detections
> MRL (0.04 |jg/L)
Samples with
Detections
> 1/2 HRL (0.035 |jg/L)1
Samples with
Detections
> HRL (0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Small Systems
serving < 10,000 people)
Groundwater
1,853
2
0.11%
2
0.11%
2
0.11%
Surface Water
1,421
4
0.28%
4
0.28%
0
0.00%
All Small Systems
3,274
6
0.18%
6
0.18%
2
0.06%
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
11,707
66
0.56%
66
0.56%
32
0.27%
Surface Water
14,860
138
0.93%
138
0.93%
65
0.44%
All Large Systems
26,567
204
0.77%
204
0.77%
97
0.37%
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
2,020
29
1.44%
29
1.44%
16
0.79%
Surface Water
5,111
53
1.04%
53
1.04%
9
0.18%
All Very Large Systems
7,131
82
1.15%
82
1.15%
25
0.35%
All Systems
All Water Systems
36,972
292
0.79%
292
0.79%
124
0.34%
Source: USEPA, 2017b
1 Since the MRL is greater than one-half the HRL, all detections are greater than one-half the HRL.
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Exhibit 3-6: PFOS National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data - Summary of
System and Population Served Data - Detections
Source Water Type
UCMR 3 Sample
Number With At Least
One Detection
> MRL (0.04 pig/L)
Percent With At Least
One Detection
> MRL (0.04 pig/L)
National Inventory1
National Estimate
of Number With At Least
One Detection2
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Groundwater
527
1,498,845
1
536
0.19%
0.04%
55,700
38,730,597
106
13,900
Surface Water
272
1,250,215
3
22,363
1.10%
1.79%
9,728
20,007,917
107
358,000
All Small Systems
799
2,749,060
4
22,899
0.50%
0.83%
65,428
58,738,514
213
372,000
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
1,453
37,141,418
29
1,070,732
2.00%
2.88%
1,470
37,540,614
29
1,070,000
Surface Water
2,260
69,619,878
38
1,314,380
1.68%
1.89%
2,310
70,791,005
38
1,310,000
All Large Systems
3,713
106,761,296
67
2,385,112
1.80%
2.23%
3,780
108,331,619
67
2,390,000
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
68
16,355,951
9
4,739,185
13.24%
28.98%
68
16,355,951
9
4,740,000
Surface Water
340
115,158,260
15
3,279,997
4.41%
2.85%
343
120,785,622
15
3,280,000
All Very Large Systems
408
131,514,211
24
8,019,182
5.88%
6.10%
411
137,141,573
24
8,020,000
All Systems
All Water Systems
4,920
241,024,567
95
10,427,193
1.93%
4.33%
69,619
304,211,706
304
10,800,000
Source: USEPA, 2017b
1 The small system national inventory numbers for systems and population served by systems were derived from a freeze of the December 2010 Safe Drinking Water
Information System / Federal Version (SDWIS/Fed) data. These counts are based on all community and non-transient non-community water systems that served 10,000
people or fewer. All large and very large systems were required to conduct UCMR 3 Assessment Monitoring; thus, the national inventory numbers for the large and very
large systems are based on the number of systems expected to complete UCMR 3 monitoring. SDWIS/Fed inventory data from 2010 were used for the UCMR 3
national extrapolations as these data were consistent with the UCMR 3 inventory data at the timeframe of the UCMR 3 sample design.
2 National estimates for the small systems are generated by multiplying the UCMR 3 national statistical sample findings of system/population percentages and national
system/population inventory numbers for PWSs. National estimates for the large and very large systems are based directly on the UCMR 3 results, since this was a
census. Due to rounding, some calculations may appear to be slightly off.
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Exhibit 3-7: PFOS National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data - Summary of
System and Population Served Data -- Detections > 1/2 HRL (0.035 |jg/L)
Source Water Type
UCMR 3 Sample
Number With At Least
One Detection
> 1/2 HRL (0.035 |jg/L)1
Percent With At Least
One Detection
> 1/2 HRL (0.035 |jg/L)1
National Inventory2
National Estimate of
Number With At Least
One Detection > 1/2 HRL3
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Groundwater
527
1,498,845
1
536
0.19%
0.04%
55,700
38,730,597
106
13,900
Surface Water
272
1,250,215
3
22,363
1.10%
1.79%
9,728
20,007,917
107
358,000
All Small Systems
799
2,749,060
4
22,899
0.50%
0.83%
65,428
58,738,514
213
372,000
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
1,453
37,141,418
29
1,070,732
2.00%
2.88%
1,470
37,540,614
29
1,070,000
Surface Water
2,260
69,619,878
38
1,314,380
1.68%
1.89%
2,310
70,791,005
38
1,310,000
All Large Systems
3,713
106,761,296
67
2,385,112
1.80%
2.23%
3,780
108,331,619
67
2,390,000
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
68
16,355,951
9
4,739,185
13.24%
28.98%
68
16,355,951
9
4,740,000
Surface Water
340
115,158,260
15
3,279,997
4.41%
2.85%
343
120,785,622
15
3,280,000
All Very Large Systems
408
131,514,211
24
8,019,182
5.88%
6.10%
411
137,141,573
24
8,020,000
All Systems
All Water Systems
4,920
241,024,567
95
10,427,193
1.93%
4.33%
69,619
304,211,706
304
10,800,000
Source: USEPA, 2017b
1 Since the MRL is greater than one-half the HRL, all detections are greater than one-half the HRL.
2 The small system national inventory numbers for systems and population served by systems were derived from a freeze of the December 2010 SDWIS/Fed data.
These counts are based on all community and non-transient non-community water systems that served 10,000 people or fewer. All large and very large systems were
required to conduct UCMR 3 Assessment Monitoring; thus, the national inventory numbers for the large and very large systems are based on the number of systems
expected to complete UCMR 3 monitoring. SDWIS/Fed inventory data from 2010 were used for the UCMR 3 national extrapolations as these data were consistent with
the UCMR 3 inventory data at the timeframe of the UCMR 3 sample design.
3 National estimates for the small systems are generated by multiplying the UCMR 3 national statistical sample findings of system/population percentages and national
system/population inventory numbers for PWSs. National estimates for the large and very large systems are based directly on the UCMR 3 results, since this was a
census. Due to rounding, some calculations may appear to be slightly off.
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Exhibit 3-8: PFOS National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data - Summary of
System and Population Served Data - Detections > HRL (0.07 |jg/L)
Source Water Type
UCMR 3 Sample
Number With At Least
One Detection
> HRL (0.07 |jg/L)
Percent With At Least
One Detection
> HRL (0.07 |jg/L)
National Inventory1
National Estimate of
Number With At Least One
Detection > HRL2
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Groundwater
527
1,498,845
1
536
0.19%
0.04%
55,700
38,730,597
106
13,900
Surface Water
272
1,250,215
0
0
0.00%
0.00%
9,728
20,007,917
0
0
All Small Systems
799
2,749,060
1
536
0.13%
0.02%
65,428
58,738,514
106
13,900
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
1,453
37,141,418
14
370,444
0.96%
1.00%
1,470
37,540,614
14
370,000
Surface Water
2,260
69,619,878
22
646,456
0.97%
0.93%
2,310
70,791,005
22
646,000
All Large Systems
3,713
106,761,296
36
1,016,900
0.97%
0.95%
3,780
108,331,619
36
1,020,000
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
68
16,355,951
5
1,741,685
7.35%
10.65%
68
16,355,951
5
1,740,000
Surface Water
340
115,158,260
4
1,030,710
1.18%
0.90%
343
120,785,622
4
1,030,000
All Very Large Systems
408
131,514,211
9
2,772,395
2.21%
2.11%
411
137,141,573
9
2,770,000
All Systems
All Water Systems
4,920
241,024,567
46
3,789,831
0.93%
1.57%
69,619
304,211,706
151
3,800,000
Source: USEPA, 2017b
1 The small system national inventory numbers for systems and population served by systems were derived from a freeze of the December 2010 SDWIS/Fed data.
These counts are based on all community and non-transient non-community water systems that served 10,000 people or fewer. All large and very large systems were
required to conduct UCMR 3 Assessment Monitoring; thus, the national inventory numbers for the large and very large systems are based on the number of systems
expected to complete UCMR 3 monitoring. SDWIS/Fed inventory data from 2010 were used for the UCMR 3 national extrapolations as these data were consistent with
the UCMR 3 inventory data at the timeframe of the UCMR 3 sample design.
2 National estimates for the small systems are generated by multiplying the UCMR 3 national statistical sample findings of system/population percentages and national
system/population inventory numbers for PWSs. National estimates for the large and very large systems are based directly on the UCMR 3 results, since this was a
census. Due to rounding, some calculations may appear to be slightly off.
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Supplemental Data Sources
Primary State PFOS Monitoring Data, 2013-2020
Consistent with the Agency's commitment in the PFAS Action Plan (USEPA, 2019c) to
highlight key information gathered by the Agency and our partners, the Agency has
supplemented its UCMR data with data collected by states who have made their data publicly
available. Subsequent to the preliminary Regulatory Determination 4 Federal Register Notice,
based on comments and information received on the proposed determination, the Agency
collected additional data from additional states. Also, EPA updated data, where applicable, for
those states for which EPA had previously gathered and presented state data in the preliminary
Regulatory Determination 4 documents. Some drinking water occurrence data from public water
systems for PFOS are available online from several states, including Alabama, California,
Colorado, Kentucky, Maine, Massachusetts, Missouri, New Hampshire, New Jersey, Ohio,
Pennsylvania, and Vermont. Very limited PFOS data were also available from Georgia and
North Dakota. EPA downloaded publicly available monitoring data from state websites. Note
that some states (e.g., Colorado, Michigan, and New Hampshire) conducted multiple, unique
sampling efforts over different time periods. The available state data are varied in terms of
quantity and coverage. Exhibit 3-9 provides a summary of the available state monitoring data,
including date range and a description of coverage and representativeness (including whether
monitoring was targeted or non-targeted). Note that Arizona, Michigan, and Rhode Island only
reported data for summed PFOS and PFOA concentrations. A description of those studies is also
included in Exhibit 3-9.
Exhibit 3-9: Summary of Available Primary State Monitoring Data
State
(Reference)
Date
Range
Type of
Water
Tested
Reporting
Limit
(M9/L)
Notes on Coverage
Survey
Type
Alabama
(ADEM,
2020)
2020 -
ongoing
Groundwater
and Surface
Water -
Finished
Water
Not
reported
The Alabama Department of Public Health
instructed water systems to carry out PFAS
monitoring at all public water systems
(PWSs) not previously sampled during UCMR
3. EPA reviewed the data available online
through March 2020. Only results that are
above the method reporting limit are posted
online.
Non-
Targeted
Arizona
(ADEQ,
2018)
2018
Groundwater
and Surface
Water -
Finished
Water
Not
reported
The Arizona Department of Environmental
Quality (ADEQ) sampled PWSs throughout
the state that were potentially impacted by
PFAS contamination. Finished drinking water
samples were collected between January and
May 2018 from 68 PWSs (109 drinking water
wells). Results are only reported for the sum
of PFOA and PFOS concentrations.
Targeted
California
(CADDW,
2020)
2013-
ongoing
Groundwater
and Surface
Water - Raw
and Finished
Water
Not
reported
EPA reviewed the data available online
through June 2020. Data were available from
approximately 300 PWSs. No discussion is
provided on the website regarding the
representativeness of the sampling effort. For
this analysis, EPA excluded results from sites
whose status was listed as monitoring well,
agriculture/ irrigation well, destroyed,
abandoned, or wastewater. Note that within
state reported data, there may be overlap
with UCMR 3 results from 2013 - 2015.
Targeted
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State
(Reference)
Date
Range
Type of
Water
Tested
Reporting
Limit
(M9/L)
Notes on Coverage
Survey
Type
Colorado
(CDPHE,
2018;
2013 -
2017
Surface
Water
(Finished
Water) and
Drinking
Water
Distribution
Samples
Not
reported
Data available from 28 "drinking water
distribution zones" (one or more per PWS) in
targeted sampling efforts at a known
contaminated aquifer region. Data were
collected by El Paso County Public Health,
local water districts and utilities, and the
Colorado Department of Public Health and
Environment (CDPHE). Results represent
data collected in a targeted region.
Targeted
CDPHE,
2020)
2020
Groundwater
and Surface
Water - Raw
and Finished
Water
0.0016 -
0.037
The Colorado Department of Public Health
and the Environment offered free testing to
PWSs serving communities, schools, and
workplaces and also to fire districts with
wells. Approximately 50% of PWSs in
Colorado participated in the 2020 PFAS
sampling project. Data included in this report
were collected in March through May of 2020.
Non-
Targeted
Georgia (GA
EPD, 2020)
2020
Surface
Water - Raw
and Finished
Water
0.018
EPA and the Georgia Environmental
Protection Division (GA EPD) conducted joint
sampling of the City of Summerville's drinking
water sources and finished drinking water on
January 23, 2020.
Targeted
Kentucky
(KYDEP,
2019)
2019
Groundwater
and Surface
Water -
Finished
Water
<=0.005
Sampling of finished drinking water data
between June and October 2019. Under this
sampling effort, data are available from 81
community public drinking water treatment
plants (WTPs), representing 74 PWSs.
Non-
Targeted
Maine
(Maine DEP,
2020)
2013-
2020
Drinking
Water
0.001 -
0.040 |jg/L
In March 2019, the Maine PFAS Task Force
was created to review the extent of PFAS
contamination in Maine. Drinking water
results collected from 2013 through 2020
have been collected at 60 locations
throughout the state. Data include results
from public and private sources. Note that
within state reported data, there may be
overlap with UCMR 3 results from 2013 -
2015.
Targeted
Massachuse
tts (MA EE A,
2020)
2016-
ongoing
Groundwater
and Surface
Water - Raw
and Finished
Water
Not
reported
EPA reviewed the data available online
through March 2020. Data were available
from 66 PWSs.
Targeted
Michigan
(Michigan
EGLE,
2020a;
Michigan
EGLE,
2018-
2019
(Phase
I)
Groundwater
and Surface
Water - Raw
and Finished
Water
0.002
Data available from 1,122 community water
systems. Results are from the Michigan
Department of Environment, Great Lakes,
and Energy (EGLE) statewide sampling for
PFAS in drinking water. Results are only
reported for the sum of PFOA and PFOS
concentrations.
Non-
Targeted
2020b;
Michigan
EGLE,
2020c;
Michigan
EGLE,
2020d)
2019
(Phase
II)
Groundwater
- Raw and
Finished
Water
Not
Reported
Data available from 690 PWSs, including
community, non-transient non-community,
transient, and tribal water systems, as well as
child care and medical facilities. Results are
from Phase II of the Michigan PFAS Action
Response Team (MPART) initiative. Results
are only reported for the sum of PFOA and
PFOS concentrations.
Non-
Targeted
3-21
-------
EPA - OGWDW
Final Regulatory Determination 4 Support Document - Ch 3, PFOS
January 2021
State
(Reference)
Date
Range
Type of
Water
Tested
Reporting
Limit
(M9/L)
Notes on Coverage
Survey
Type
2019
(Monthl
y)
Surface
Water - Raw
and Finished
Water
Not
Reported
Data available from 68 water systems.
Michigan EGLE collected monthly samples
from PWSs sampled during Phase I ofthe
Statewide PFAS Sampling Survey which
utilized surface water as a source. Results
are only reported for the sum of PFOA and
PFOS concentrations.
Non-
Targeted
2019-
2020
(Quarter
ly)
Groundwater
and Surface
Water - Raw
and Finished
Water
Not
Reported
Data available from 86 water
systems. Michigan EGLE collected quarterly
samples from PWSs sampled during Phase I
which had Total Tested PFAS levels > 0.010
|jg/L but did not exceed 0.070 |jg/L
PFOS+PFOA. Results are only reported for
the sum of PFOA and PFOS concentrations.
Targeted
Missouri
(Missouri
DNR, 2018)
2016-
2017
Groundwater
and Surface
Water - Raw
and Finished
Water
Not
reported
The Missouri Department of Natural
Resources (Missouri DNR) conducted
targeted sampling of finished drinking water
data between September 2016 and February
2017. Under this sampling effort, 30 water
samples were collected from 15 PWSs.
Targeted
New
Hampshire -
(NHDES,
2017;
NHDES,
2020)
2013 -
2017
Groundwater
and Surface
Water -
Finished
Water
Not
Reported
Data available from 295 PWSs providing
results, including PWSs near contaminated
sites. Results represent all PFOS water
quality data reported to the New Hampshire
Department of Environmental Services
(NHDES) through May 3, 2017. Note that
within state reported data, there may be
overlap with UCMR 3 results from 2013 -
2015.
Targeted
2019
Groundwater
and Surface
Water -
Finished
Water
0.002-
0.005
Data available from 785 PWSs providing
results. Results represent all PFOS water
quality data reported to the New Hampshire
Department of Environmental Services
(NHDES) for 2019.
Non-
Targeted
New Jersey
(NJDEP,
2020)
2019-
ongoing
Groundwater
and Surface
Water -
Finished
Water
Not
Reported
Statewide sampling of finished drinking water
data was available from 2019 and 2020. EPA
reviewed data available online through July
2020. In total, 7,957 water samples from
1,222 PWS were analyzed for PFOA and
PFOS.
Non-
Targeted
North
Dakota
(NDDEQ,
2019)
2018
Groundwater
and Surface
Water - Raw
and Finished
Water
Not
reported.
In October 2018, the North Dakota
Department of Health collected samples from
a variety of sites where PFAS would
potentially be present. Sampling included raw
and finished water from 7 drinking water
treatment plants that were chosen based on
either the population served or proximity to an
industrial site.
Targeted
Ohio (Ohio
DOH, 2020)
Feb
2020-
Ongoing
Groundwater
and Surface
Water - Raw
and Finished
Water
0.005
The Ohio EPA has coordinated sampling of
raw and finished drinking water from PWSs
throughout the state. EPA reviewed the data
available online through August 2020. During
this timeframe, data were available from 694
PWSs. (Sampling is ongoing and by the end
of 2020, all 1,500 PWSs anticipated to be
sampled.)
Non-
Targeted
3-22
-------
EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 3, PFOS January 2021
State
(Reference)
Date
Range
Type of
Water
Tested
Reporting
Limit
(M9/L)
Notes on Coverage
Survey
Type
Pennsylvani
a (PADEP,
2020)
2019-
ongoing
Groundwater
and Surface
Water -
Finished
Water
0.0019
A PFAS Sampling Plan was developed to test
PWSs across the state. A total of 493 PWSs
were identified for inclusion in the study as
being at the highest risk for PFAS
contamination. EPA reviewed data available
through September 2019 from 87 PWSs.
Sampling is expected to take a year to
complete.
Targeted
Rhode
Island (Rl
DOH, 2020)
2017-
2019
Groundwater
and Surface
Water -
Finished
Water
0.004
The Rhode Island Department of Health (Rl
DOH) sampled all major drinking water
supplies in the state, as well as water from
schools with their own well(s), between 2017
and 2019. Under this sampling effort, PFOA
and PFOS data were collected by 87 PWSs.
Results are only reported for the sum of
PFOA and PFOS concentrations.
Non-
Targeted
Vermont (VT
DEC, 2020)
2019-
ongoing
Groundwater
and Surface
Water -
Finished
Water
0.002
The newly adopted Vermont Water Supply
Rule requires all community and non-
transient non-community water systems to
sample for PFAS in 2020. EPA reviewed data
available online through June 2020 from
nearly 600 PWSs.
Non-
Targeted
A summary of primary state monitoring data from public water systems for PFOS is
presented in Exhibit 3-10 through Exhibit 3-12. As noted above, some of the monitoring data
from each state are limited and may not be representative of occurrence in the state. Overall,
detected concentrations ranged from 0.00024 |ig/L (Missouri) to 1.0 |ig/L (New Jersey). Eight
states had at least one detection of PFOS greater than the HRL of 0.07 |ig/L. Six states did not
report any detections of PFOS greater than the HRL.
See section 3.4.4 for a presentation of state monitoring results for summed PFOS and
PFOA concentrations, including the reported results from Arizona, Michigan, and Rhode Island.
Exhibit 3-10: PFOS Primary State Drinking Water Occurrence Data - Summary of
Detected Concentrations
State
Source Water Type1
Concentration Value of Detections (|jg/L)
(Sample Type)
Minimum
Median
90th
99th
Maximu
Percentile
Percentile
m
Alabama
(2020)
Groundwater (Finished)
0.0038
0.011
0.0182
0.02261
0.023
Surface Water (Finished)
0.0021
0.00915
0.0396
0.05583
0.057
Total2
0.0021
0.01
0.0209
0.05457
0.057
Groundwater (Raw)
0.00047
0.018
0.1007
0.4354
0.65
Groundwater (Finished)
0.0004
0.0129
0.02137
0.05492
0.074
California
(2013 -2020)
Groundwater (Not
Provided)3
0.0018
0.0029
0.00472
0.011208
0.012
Surface Water (Raw)
0.00092
0.0164
0.05096
0.1976
0.51
Surface Water (Finished)
0.0013
0.00685
0.03849
0.06381
0.25
Surface Water (Not
Provided)3
0.0017
0.013
0.041
0.04836
0.052
Not Provided4
ND
ND
ND
ND
ND
3-23
-------
EPA - OGWDW
Final Regulatory Determination 4 Support Document - Ch 3, PFOS
January 2021
State
Source Water Type1
(Sample Type)
Concentration Value of Detections (|jg/L)
Minimum
Median
90th
Percentile
99th
Percentile
Maximu
m
Total2
0.0004
0.016
0.05332
0.28
0.65
Colorado
(2013 -2017)
Distribution (Finished)
0.0023
0.06
0.1
0.19
0.21
Surface Water (Finished)
ND
ND
ND
ND
ND
Total2
0.0023
0.06
0.1
0.19
0.21
Colorado
(2020)
Groundwater (Raw)
0.00047
0.0036
0.00803
0.01571
0.017
Groundwater (Finished)
0.00042
0.0017
0.0062
0.01289
0.018
Surface water (Raw)
0.0013
0.01
0.0408
0.758
0.94
Surface water (Finished)
0.00055
0.002
0.00612
0.009404
0.011
Total2
0.00042
0.00275
0.011
0.1209
0.94
Georgia
(2020)
Surface Water (Raw)
ND
ND
ND
ND
ND
Surface Water (Finished)
0.049
0.049
0.049
0.049
0.049
Surface Water (Not
Provided)3
0.041
0.044
0.0464
0.04694
0.047
Total2
0.041
0.047
0.0486
0.04896
0.049
Kentucky
(2019)
Groundwater (Finished)
0.001
0.001625
0.010955
0.0181055
0.0189
Surface Water (Finished)
0.00101
0.00151
0.004216
0.0075986
0.00835
Total2
0.001
0.00151
0.004432
0.015524
0.0189
Maine
(2013-2020)
Not Provided (Raw)
0.000494
0.007015
0.01995
0.12
0.12
Not Provided (Finished)
0.000838
0.007495
0.2056
0.2848
0.29
Not Provided4
0.00146
0.00158
0.002164
0.0022954
0.00231
Total2
0.000494
0.00691
0.03378
0.2344
0.29
Massachuset
ts
(2016-2020)
Groundwater (Raw)
0.0017
0.0081
0.0722
0.2000
0.20
Groundwater (Finished)
0.0020
0.0083
0.0422
0.1000
0.16
Surface Water (Raw)
0.0020
0.0065
0.0125
0.0262
0.042
Surface Water (Finished)
0.0021
0.0069
0.0148
0.0276
0.042
Not Provided5 (Raw)
ND
ND
ND
ND
ND
Not Provided5 (Finished)
ND
ND
ND
ND
ND
Total2
0.0017
0.0076
0.0440
0.1732
0.2
Missouri
(2016-2017)
Not Provided5 (Raw)
0.00024
0.00043
0.00115
0.001546
0.00159
Not Provided5 (Finished)
0.00024
0.0005
0.001027
0.0011924
0.00121
Total2
0.00024
0.00046
0.00105
0.001514
0.00159
New
Hampshire
(2013 -2017)
Groundwater (Finished)
0.000893
0.006
0.017
0.117
0.16
Surface Water (Finished)
0.0044
0.008
0.009
0.01
0.0096
Not Provided4
0.004
0.01
0.014
0.015
0.015
Total2
0.000893
0.007
0.016
0.112
0.16
New
Hampshire
(2019)
Groundwater (Finished)
0.00089
0.00401
0.0168
0.08935
0.206
Surface Water (Finished)
0.00212
0.0028
0.003798
0.0047268
0.00483
Not Provided5 (Finished)
0.00233
0.00233
0.00233
0.00233
0.00233
Total2
0.00089
0.003875
0.0162
0.08365
0.206
New Jersey
(2019-2020)
Groundwater (Finished)
0.0005
0.0055
0.019
0.1364
0.6
Surface Water (Finished)
0.00068
0.0051
0.011
0.02216
0.055
Not Provided5 (Finished)
0.42
0.715
0.934
0.9934
1.00
Total2
0.0005
0.005445
0.0179
0.1297
1.00
North Dakota
(2018)
Not Provided5 (Raw)
0.0013
0.0013
0.0013
0.0013
0.0013
Not Provided5 (Finished)
0.00037
0.00045
0.00097
0.001087
0.0011
Total2
0.00037
0.000775
0.00124
0.001294
0.0013
3-24
-------
EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 3, PFOS January 2021
State
Source Water Type1
(Sample Type)
Concentration Value of Detections (|jg/L)
Minimum
Median
90th
Percentile
99th
Percentile
Maximu
m
Ohio
(2020)
Groundwater (Raw)
0.0052
0.0124
0.03944
0.06645
0.069
Groundwater (Finished)
0.0058
0.01235
0.0408
0.06345
0.066
Surface Water (Raw)
0.00647
0.006885
0.007217
0.0072917
0.0073
Surface Water (Finished)
0.0068
0.0068
0.0068
0.0068
0.0068
Total2
0.0052
0.0104
0.03952
0.06792
0.069
Pennsylvania
(2019)
Groundwater (Finished)
0.0018
0.0045
0.01188
0.0828
0.094
Surface Water (Finished)
0.0019
0.006
0.0084
0.01254
0.013
Total2
0.0018
0.00505
0.01085
0.074
0.094
Vermont
(2019-2020)
Groundwater (Finished)
0.002
0.005
0.020
0.105
0.161
Surface Water (Finished)
ND
ND
ND
ND
ND
Not Provided5 (Finished)
ND
ND
ND
ND
ND
Total2
0.002
0.005
0.020
0.105
0.161
ND = no detections in this category
1 Whenever possible, systems' source water type information was derived from a freeze of the December 2019
SDWIS/Fed data.
2 Total rows display the minimum, median, 90th percentile, 99th percentile, and maximum concentration values from
the entire state data set, regardless of water type or sample type.
3 The results were not identified in the state data set as having been collected from raw or finished water.
4 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
5 The results were not identified in the state data set as having been collected from groundwater or surface water.
Exhibit 3-11: PFOS Primary State Drinking Water Occurrence Data - Summary of
Samples
State
Source Water Type1
(Sample Type)
Total #
of
Samples
All Detections
Detections > V*
HRL (0.035 |jg/L)
Detections > HRL
(0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Alabama2
(2020)
Groundwater
(Finished)
-
14
-
0
-
0
-
Surface Water
(Finished)
-
14
-
2
-
0
-
Total
-
28
-
2
-
0
-
California
(2013 -2020)
Groundwater
(Raw)
1,697
724
42.66%
194
11.43%
91
5.36%
Groundwater (Finished)
459
128
27.89%
6
1.31%
1
0.22%
Groundwater
(Not Provided)3
27
12
44.44%
0
0.00%
0
0.00%
Surface Water (Raw)
2,369
1113
46.98%
284
11.99%
61
2.57%
Surface Water (Finished)
429
108
25.17%
14
3.26%
1
0.23%
Surface Water
(Not Provided)3
88
53
60.23%
11
12.50%
0
0.00%
Not Provided4
2
0
0.00%
0
0.00%
0
0.00%
Total
5,071
2,138
42.16%
509
10.04%
154
3.04%
Colorado
(2013-2017)
Distribution (Finished)
96
38
39.58%
23
23.96%
10
10.42%
Surface Water (Finished)
11
0
0.00%
0
0.00%
0
0.00%
Total
107
38
35.51%
23
21.50%
10
9.35%
Colorado
(2020)
Groundwater
(Raw)
87
44
50.57%
0
0.00%
0
0.00%
3-25
-------
EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 3, PFOS January 2021
State
Source Water Type1
(Sample Type)
Total #
of
Samples
All Detections
Detections > V*
HRL (0.035 |jg/L)
Detections > HRL
(0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Groundwater (Finished)
345
74
21.45%
0
0.00%
0
0.00%
Surface water
(Raw)
43
29
67.44%
3
6.98%
3
6.98%
Surface water (Finished)
238
43
18.07%
0
0.00%
0
0.00%
Total
713
190
26.65%
3
0.42%
3
0.42%
Georgia
(2020)
Surface Water (Raw)
1
0
0.00%
0
0.00%
0
0.00%
Surface Water (Finished)
2
1
50.00%
1
50.00%
0
0.00%
Surface Water
(Not Provided)3
2
2
100.00%
2
100.00%
0
0.00%
Total
5
3
60.00%
3
60.00%
0
0.00%
Kentucky
(2019)
Groundwater
(Finished)
38
6
15.79%
0
0.00%
0
0.00%
Surface Water
(Finished)
43
27
62.79%
0
0.00%
0
0.00%
Total
81
33
40.74%
0
0.00%
0
0.00%
Maine
(2013-2020)
Not Provided5
(Raw)
236
96
40.68%
7
2.97%
6
2.54%
Not Provided5 (Finished)
86
14
16.28%
4
4.65%
3
3.49%
Not Provided4
21
3
14.29%
0
0.00%
0
0.00%
Total
343
113
32.94%
11
3.21%
9
2.62%
Massachusetts
(2016-2020)
Groundwater
(Raw)
195
101
51.79%
30
15.38%
12
6.15%
Groundwater (Finished)
221
130
58.82%
22
9.95%
7
3.17%
Surface Water (Raw)
121
73
60.33%
1
0.83%
0
0.00%
Surface Water (Finished)
61
31
50.82%
0
0.00%
0
0.00%
Not Provided5
(Raw)
1
0
0.00%
0
0.00%
0
0.00%
Not Provided5 (Finished)
1
0
0.00%
0
0.00%
0
0.00%
Total
600
335
55.83%
53
8.83%
19
3.17%
Missouri
(2016-2017)
Not Provided5
(Raw)
26
9
34.62%
0
0.00%
0
0.00%
Not Provided5 (Finished)
29
12
41.38%
0
0.00%
0
0.00%
Total
55
21
38.18%
0
0.00%
0
0.00%
New
Hampshire
(2013-2017)
Groundwater
(Finished)
471
44
9.34%
2
0.42%
1
0.21%
Surface Water
(Finished)
107
3
2.80%
0
0.00%
0
0.00%
Not Provided5 (Finished)
6
2
33.33%
0
0.00%
0
0.00%
Total
584
49
8.39%
2
0.34%
1
0.17%
New
Hampshire
(2019)
Groundwater
(Finished)
866
146
16.86%
4
0.46%
2
0.23%
Surface Water
(Finished)
74
9
12.16%
0
0.00%
0
0.00%
Not Provided5 (Finished)
5
1
20.00%
0
0.00%
0
0.00%
Total
945
156
16.51%
4
0.42%
2
0.21%
New Jersey
(2019-2020)
Groundwater (Finished)
7,017
2269
32.34%
100
1.43%
35
0.50%
Surface Water (Finished)
959
543
56.62%
2
0.21%
0
0.00%
Not Provided5 (Finished)
12
4
33.33%
4
33.33%
4
33.33%
Total
7,988
2816
35.25%
106
1.33%
39
0.49%
North Dakota
(2018)
Not Provided5
(Raw)
7
1
14.29%
0
0.00%
0
0.00%
Not Provided5 (Finished)
7
3
42.86%
0
0.00%
0
0.00%
3-26
-------
EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 3, PFOS January 2021
State
Source Water Type1
(Sample Type)
Total #
of
Samples
All Detections
Detections > V*
HRL (0.035 |jg/L)
Detections > HRL
(0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Total
14
4
28.57%
0
0.00%
0
0.00%
Groundwater
(Raw)
588
18
3.06%
2
0.34%
0
0.00%
Ohio
(2020)
Groundwater
(Finished)
720
16
2.22%
2
0.28%
0
0.00%
Surface Water
(Raw)
38
2
5.26%
0
0.00%
0
0.00%
Surface Water
(Finished)
40
1
2.50%
0
0.00%
0
0.00%
Total
1,386
37
2.67%
4
0.29%
0
0.00%
Pennsylvania
(2019)
Groundwater
(Finished)
76
15
19.74%
1
1.32%
1
1.32%
Surface Water
(Finished)
20
11
55.00%
0
0.00%
0
0.00%
Total
96
26
27.08%
1
1.04%
1
1.04%
Groundwater
(Finished)
634
43
6.78%
1
0.16%
1
0.16%
Vermont
(2019-2020)
Surface Water
(Finished)
55
0
0.00%
0
0.00%
0
0.00%
Not Provided5 (Finished)
6
0
0.00%
0
0.00%
0
0.00%
Total
695
43
6.19%
1
0.14%
1
0.14%
1 Whenever possible, systems' source water type information was derived from a freeze of the December 2019
SDWIS/Fed data.
2 Only data for detections were available from Alabama.
3 The results were not identified in the state data set as having been collected from raw or finished water.
4 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
5 The results were not identified in the state data set as having been collected from groundwater or surface water.
Exhibit 3-12: PFOS Primary State Drinking Water Occurrence Data - Summary of
Systems
State
Source Water
Type1
(Sample Type)
Total # of
Systems/
Sites
Systems/Sites with
Detections
Systems/Sites with
Detections
> 1/2 HRL
(0.035 |jg/L)
Systems/Sites with
Detections > HRL
(0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Alabama2
(2020)
Groundwater
(Finished)
-
9
-
0
-
0
-
Surface Water
(Finished)
-
11
-
1
-
0
-
Total
-
20
-
1
-
0
-
California
(2013-2020)
Groundwater
(Raw)
166
78
46.99%
24
14.46%
10
6.02%
Groundwater
(Finished)
35
10
28.57%
3
8.57%
1
2.86%
Groundwater
(Not Provided)8
9
4
44.44%
0
0.00%
0
0.00%
Surface Water
(Raw)
125
64
51.20%
21
16.80%
8
6.40%
Surface Water
(Finished)
57
15
26.32%
4
7.02%
1
1.75%
Surface Water
(Not Provided)8
17
8
47.06%
4
23.53%
0
0.00%
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EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 3, PFOS January 2021
State
Source Water
Type1
(Sample Type)
Total # of
Systems/
Sites
Systems/Sites with
Detections
Systems/Sites with
Detections
> 1/2 HRL
(0.035 |jg/L)
Systems/Sites with
Detections > HRL
(0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Not Provided9
1
0
0.00%
0
0.00%
0
0.00%
Total
301
142
47.18%
46
15.28%
18
5.98%
Colorado3
(2013 -2017)
Distribution
(Finished)
23
12
52.17%
7
30.43%
4
17.39%
Surface Water
(Finished)
5
0
0.00%
0
0.00%
0
0.00%
Total
28
12
42.86%
7
25.00%
4
14.29%
Colorado
(2020)
Groundwater
(Raw)
24
13
54.17%
0
0.00%
0
0.00%
Groundwater
(Finished)
225
57
25.33%
0
0.00%
0
0.00%
Surface water
(Raw)
9
5
55.56%
2
22.22%
2
22.22%
Surface water
(Finished)
172
35
20.35%
0
0.00%
0
0.00%
Total
400
97
24.25%
2
0.50%
2
0.50%
Georgia
(2020)
Surface Water
(Raw)
1
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Finished)
1
1
100.00%
1
100.00%
0
0.00%
Surface Water
(Not Provided)8
1
1
100.00%
1
100.00%
0
0.00%
Total
1
1
100.00%
1
100.00%
0
0.00%
Kentucky4
(2019)
Groundwater
(Finished)
38
6
15.79%
0
0.00%
0
0.00%
Surface Water
(Finished)
43
27
62.79%
0
0.00%
0
0.00%
Total
81
33
40.74%
0
0.00%
0
0.00%
Maine5
(2013-2020)
Not Provided10
(Raw)
37
19
51.35%
4
10.81%
3
8.11%
Not Provided10
(Finished)
23
7
30.43%
3
13.04%
2
8.70%
Not Provided9
9
2
22.22%
0
0.00%
0
0.00%
Total
60
23
38.33%
6
10.00%
4
6.67%
Massachusetts
(2016-2020)
Groundwater
(Raw)
24
12
50.00%
4
16.67%
2
8.33%
Groundwater
(Finished)
46
23
50.00%
5
10.87%
2
4.35%
Surface Water
(Raw)
8
6
75.00%
1
12.50%
0
0.00%
Surface Water
(Finished)
11
8
72.73%
0
0.00%
0
0.00%
Not Provided10
(Raw)
1
0
0.00%
0
0.00%
0
0.00%
Not Provided10
(Finished)
1
0
0.00%
0
0.00%
0
0.00%
Total
66
34
51.52%
6
9.09%
3
4.55%
Missouri6
(2016-2017)
Not Provided10
(Raw)
14
5
35.71%
0
0.00%
0
0.00%
Not Provided10
(Finished)
15
7
46.67%
0
0.00%
0
0.00%
Total
15
8
53.33%
0
0.00%
0
0.00%
Groundwater
(Finished)
265
34
12.83%
2
0.75%
1
0.38%
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EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 3, PFOS January 2021
State
New
Hampshire
(2013-2017)
Source Water
Type1
(Sample Type)
Total # of
Systems/
Sites
Systems/Sites with
Detections
Systems/Sites with
Detections
> 1/2 HRL
(0.035 |jg/L)
Systems/Sites with
Detections > HRL
(0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Surface Water
(Finished)
24
3
12.50%
0
0.00%
0
0.00%
Not Provided10
(Finished)
6
2
33.33%
0
0.00%
0
0.00%
Total
295
39
13.22%
2
0.68%
1
0.34%
New
Hampshire
(2019)
Groundwater
(Finished)
743
131
17.63%
4
0.54%
2
0.27%
Surface Water
(Finished)
37
6
16.22%
0
0.00%
0
0.00%
Not Provided10
(Finished)
5
1
20.00%
0
0.00%
0
0.00%
Total
785
138
17.58%
4
0.51%
2
0.25%
New Jersey
(2019-2020)
Groundwater
(Finished)
1,120
459
40.98%
23
2.05%
9
0.80%
Surface Water
(Finished)
98
70
71.43%
1
1.02%
0
0.00%
Not Provided10
(Finished)
4
1
25.00%
1
25.00%
1
25.00%
Total
1,222
530
43.37%
25
2.05%
10
0.82%
North Dakota7
(2018)
Not Provided10
(Raw)
7
1
14.29%
0
0.00%
0
0.00%
Not Provided10
(Finished)
7
3
42.86%
0
0.00%
0
0.00%
Total
7
3
42.86%
0
0.00%
0
0.00%
Ohio
(2020)
Groundwater
(Raw)
546
14
2.56%
1
0.18%
0
0.00%
Groundwater
(Finished)
663
13
1.96%
1
0.15%
0
0.00%
Surface Water
(Raw)
30
2
6.67%
0
0.00%
0
0.00%
Surface Water
(Finished)
30
1
3.33%
0
0.00%
0
0.00%
Total
694
17
2.45%
1
0.14%
0
0.00%
Pennsylvania
(2019)
Groundwater
(Finished)
72
13
18.06%
1
1.39%
1
1.39%
Surface Water
(Finished)
15
8
53.33%
0
0.00%
0
0.00%
Total
87
21
24.14%
1
1.15%
1
1.15%
Vermont
(2019-2020)
Groundwater
(Finished)
547
28
5.12%
1
0.18%
1
0.18%
Surface Water
(Finished)
43
0
0.00%
0
0.00%
0
0.00%
Not Provided10
(Finished)
2
0
0.00%
0
0.00%
0
0.00%
Total
592
28
4.73%
1
0.17%
1
0.17%
1 Whenever possible, systems' source water type information was derived from a freeze of the December 2019
SDWIS/Fed data.
2 Only data for detections were available from Alabama.
3 For the Colorado distribution system samples collected between 2013 and 2017, "systems" were counted as unique
zones in which the sample was distributed.
4 For Kentucky, "systems" were counted as unique location names as PWSIDs from SDWIS/Fed could not always be
linked with the location names.
5 For Maine, "systems" were counted as unique site names as PWSIDs from SDWIS/Fed could not always be linked
with the site names.
6 For Missouri, "systems" were counted as unique facility numbers in which the sample was collected.
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7 For North Dakota, "systems" were counted as unique sites in which the sample was collected.
8 The results were not identified in the state data set as having been collected from raw or finished water.
9 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water
10 The results were not identified in the state data set as having been collected from groundwater or surface water.
In addition to the monitoring data available from public water systems, North Carolina
has made data from 17 private wells available associated with the Chemours facility in
Fayetteville (NCDEQ, 2018). The maximum PFOS concentration was 0.0195 |ig/L, while the
median was 0.001 |ig/L. PFOS concentrations did not exceed EPA HRL (0.07 |ig/L) at any of
the sampling sites. Note that EPA does not regulate private drinking water wells but may
evaluate data from private wells where the data may be indicative of contaminants in aquifers
that are used as sources for public water system wells.
Due to the multitude of requests for public records for PFAS analytical results, the
Alaska Department of Environmental Conservation (Alaska DEC) has made PFAS drinking
water sample results from private wells and public water systems available online (Alaska DEC,
2020). In samples collected from February 2014 through July 2020, a total of six communities
are listed as having drinking water sample results above EPA's Health Advisory Level. Twenty-
three communities are identified as having all drinking water sample results below the EPA
Health Advisory Level.
Additional Secondary Source Water and Drinking Water Studies
The discussion presented in this section represent secondary analyses summarized from
published studies and/or publicly available presentations that did not contain downloadable
occurrence data for evaluation purposes. For selected states that had publicly available
occurrence data for evaluation, please see Exhibit 3-9 through Exhibit 3-12 above.
The Division of Water Supply of the New Jersey Department of Environmental
Protection (NJDEP) collected 29 water samples (22 raw water and 7 finished water) from 23
water systems in 2006. Sites selected included those near facilities where PFOA may have been
used, handled, stored and/or manufactured, as well as facilities where previously collected data
indicated the presence of a large number of tentatively identified compounds. The samples were
tested for PFOS as well as PFOA. PFOS was detected in 13 of the 22 raw water samples, with
the detected concentrations ranging from <0.004 |ig/L to 0.049 |ig/L. PFOS was detected in four
of the seven finished water samples, with the detected concentrations ranging from <0.004 |ig/L
to 0.014 |ig/L. Note that there were seven detected concentrations (five in raw water and two in
finished water) that were detected but not quantified below the low calibration standard of 0.004
|ig/L (NJDEP, 2007).
Additional sampling conducted by the NJDEP occurred between July 2009 and February
2010. The main objective of sample site selection was to select sites throughout all of New
Jersey that serve as sources of drinking water. Therefore, at least one sampling location was
selected in each of 21 counties except Hudson County, as all water served to residents in that
county is purchased from sources outside the county (NJDEP, 2014). Since the objective of this
study was to determine the occurrence of PFAS in drinking water sources throughout New
Jersey, this study included only untreated water samples, in contrast to the 2006 study (described
above), which included samples from both raw (untreated) and treated water sources. A total of
33 raw water samples were collected from 31 PWSs in 20 of the 21 counties in New Jersey. (No
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January 2021
finished water samples were collected as part of this study.) PFOS was detected in 9 (27 percent)
of the 33 samples. Reported PFOS concentrations ranged from 0.005 |ig/L to 0.043 |ig/L
(NJDEP, 2014).
In Tucson, Arizona, PFOS was detected at four groundwater wells used for drinking
water in 2009, with concentrations ranging from 0.0039 to 0.065 |ig/L. The wells were
resampled in 2010 and three of the four wells were found to have PFOS at concentrations >0.2
|ig/L (Quanrud et al., 2010).
In 2018, the Iowa Air National Guard (Iowa ANG) completed site investigations of bases
located at the Sioux City and Des Moines airports (Iowa DNR, 2020). Detections of PFAS
compounds were identified at both locations. At Sioux City, the Site Investigation Report
suggested that private wells might be impacted by off-site migration of PFAS contamination.
The Iowa Department of Natural Resources (Iowa DNR) required sampling of raw water by the
Iowa ANG from selected private wells and a public well prior to the next phase of work
(Remedial Investigation). This work was completed in 2019 and the results of this testing
indicated the raw water for all wells tested were either below detection or below the drinking
water health advisory (Iowa DNR, 2020).
In Minnesota, sampling was conducted in 2004-2005 at selected municipal, non-
community, and private drinking water wells in the vicinity of perfluorinated compound waste
sites (Goeden and Kelly, 2006). In this targeted sampling study, PFOS was detected in six (16.2
percent) of the 37 municipal wells sampled, in none of the 26 private wells sampled, and in none
of the 22 non-community wells sampled. The aggregate results of this study showed that six (7.1
percent) of the 85 wells sampled had PFOS detections, with a maximum concentration of 1.4
Hg/L-
As a supplement to the data provided in Goeden and Kelly (2006), ATSDR published
some additional details/updates regarding PFOS occurrence in six Oakdale, Minnesota,
municipal wells (ATSDR, 2008). These wells are a subset of the wells in the Goeden and Kelly
(2006) targeted sampling study, discussed above. PFOS has been detected consistently in four of
the six (66.7 percent) municipal wells reported by ATSDR. Detected concentrations ranged from
0.15 |ig/L to 1.41 |ig/L. ATSDR (2008) reports that "in September 2007, the Minnesota
Department of Health (MDH) Public Health Laboratory issued new formal reporting levels for
the seven perfluorinated compounds of 0.3 micrograms per liter (|ig/L)." Presumably the
reported detections lower than 0.3 |ig/L were collected before that time.
In 2018, Kelly and Peterson (2018) presented the results of the sampling of perfluorinated
compounds in Minnesota in the East Metro area. This sampling began with drinking water
investigations near the 3M Cottage Grove plant and related legacy waste disposal sites in
Washington County (east of St. Paul) (MDH, 2019). The East Metro investigations have
identified an area of groundwater contamination covering over 150 square miles, affecting the
drinking water supplies of over 140,000 Minnesotans. Since 2003, about 2,500 private wells
have been sampled and more than 800 drinking water advisories have been issued (Kelly and
Peterson, 2018). Frequent and intensive monitoring was conducted at private wells near known
sources of contamination while less frequent monitoring was conducted at private wells with low
and stable PFAS concentrations.
The Minnesota Department of Health (MDH) is working with partner agencies to identify
and respond to PFAS contamination in Minnesota as needed. Ongoing efforts are described on
their website (MDH, 2020) and are summarized below.
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• In the East Metro of the Twin Cities, PFAS concentrations in most city wells have
remained stable or decreased slightly over time. MDH reports that there are currently five
community public water supplies in the East Metro that have individual wells above the
MDH health-based guidance values: Oakdale, Lake Elmo, Woodbury, Cottage Grove,
and St. Paul Park. Over 3,000 private wells have also been sampled in the East Metro
area.
• Bemidji's community public water supply wells are above the updated MDH health-
based guidance values. Since 2009, the Minnesota Pollution Control Agency (MPCA)
and MDH have sampled 25 residential and other wells to the east, northeast, and
southeast of the airport. MDH reported that on one occasion trace level detections of
PFBA were found in four of the wells, far below the Health Risk Limit. Otherwise, PFAS
have not been detected in the wells.
• In 2010-2011, the Air National Guard sampled 12 residential wells to the north,
northwest, and northeast of the Duluth Air National Guard Base. PFAS were detected in
three wells, at concentrations below the drinking water values in effect at that time. In
2016, when MDH lowered the guidance values for PFOS and PFOA, the state began
sampling wells around the airbase, including to the south. MDH (2020) reported that 57
wells have been sampled. Trace levels of PFAS have been detected in 22 wells, mainly
PFBA and PFPeA at concentrations similar to shallow groundwater samples statewide.
The Nebraska Department of Environmental Quality (NDEQ) formed a team to track
issue with the PFAS compounds. Initial sampling conducted at 25 PWSs between 2013 - 2015
by the Nebraska Department of Health and Human Services (Nebraska DHHS) Drinking Water
Program identified zero detections of PF AS. A statewide PF AS inventory was completed by
NDEQ in 2017 that identified 990 sites that potentially used or produced PFAS compounds
(NDEQ, 2020). Based on the inventory, NDEQ conducted initial PFAS sampling of nearby
private wells. NDEQ reported that while levels of concern have not been detected, they are early
in the investigation (NDEQ, 2020).
In 2018, the New York State Department of Health (NYSDOH) published a summary
presentation (Wilson, 2018) that described the occurrence of PFOA and PFOS throughout the
state. Data from three sources were summarized: (1) UCMR 3; (2) follow-up sampling in PWSs
and private wells near known and potential sources of contamination; and (3) a source water
assessment sampling program.
The presentation indicated that 10 percent of the PWSs had PFOA and PFOS
concentrations at or above 0.030 |ig/L and 15 percent of PWSs had concentrations at or above
0.020 |ig/L. Approximately 20 percent of PWSs reported concentrations at or above 0.010 |ig/L.
It was noted that the majority of the New York State (NYS) PWS occurrence data was targeted
sampling. Furthermore, although the sample size of the study was large, it represented only a
small percentage of the PWSs throughout NYS. A summary of the NYS occurrence data is
presented in Exhibit 3-13 below.
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Exhibit 3-13: Summary of New York State PFOA-PFOS Sampling Results
PFOA + PFOS Levels
Follow-Up Sampling near
Known/Suspected
Contamination: PWS
Occurrence
Source Water
Assessment
Sampling: PWS
Occurrence
Overall NYS
Occurrence
Data
Non-detect (< 0.002 pg/L)
45%
58%
50% (129)
0.002 to < 0.020 |jg/L
35%
36%
35% (91)
0.020 to < 0.070 |jg/L
12%
5%
9% (24)
Greater than 0.070 |jg/L (EPA
Health Advisory)
8%
1%
5% (13)
Source: Wilson, 2018
The presentation concluded that the NYS follow-up sampling and source water
assessment sampling findings were comparable to national occurrence findings from UCMR 3.
The lower reporting limit yielded more detections. (The detection limit in NYS sampling was
0.002 |ig/L for both PFOA and PFOS, while the minimum reporting level in UCMR 3 was 0.020
|ig/L for PFOA and 0.040 |ig/L for PFOS.)
In 2018, the Vermont Department of Environmental Conservation (VT DEC) published a
report titled "Perfluoroalkyl Substances (PFAS) Contamination Status Report" that summarized
the findings of an investigation of PFAS contamination at and around a known contaminated site
in the Bennington area (VT DEC, 2018). Results were described for 10 different types of
sampling sites, including wire coating facilities, semi-conductor facilities, groundwater at
landfills, surface water, sediment and fish, public drinking water supply testing, wastewater
treatment facilities, and more. DEC tested over 600 private drinking water wells in Bennington
and the two municipal water systems for Bennington and North Bennington. The VT DEC has
also posted the results of 2016 PFAS sampling from private wells in the Bennington area in PDF
format.
Quinones and Snyder (2009) reported monitoring results of perfluoroalkyl compounds,
including PFOS, from drinking water treatment facility samples collected across the United
States in 2008, and from associated surface, ground, and wastewater sources. Raw waters at
these facilities included sources regarded as having no impact from treated wastewater, as well
as two planned potable reuse facilities with influents composed entirely or nearly entirely of
treated wastewater. The method reporting limit for PFOS was 0.001 |ig/L. PFOS was the only
investigated perfluoroalkyl compound detected in minimally impacted surface waters. Surface
water samples from the Boulder Basin, Hoover Dam, and the Lower Colorado River had
reportable average PFOS levels in four of five sites at 0.001 |ig/L to 0.002 |ig/L.
Seven drinking water utilities with low, moderate, or high degrees of wastewater impact
exhibited varying concentrations and frequencies of detection of PFOS in their influents (raw
water) and effluents (finished water). Quinones and Snyder (2009) considered approximate
wastewater contributions above 50 percent to be "high" wastewater impacts at sites and facilities,
30-50 percent to be "medium," and 5 percent and less to be "low." (Note that the study did not
assign a category to the range of 5-30 percent.) Monitoring results include:
• Two utilities with low wastewater impact exhibited average detected concentrations
of PFOS that ranged from <0.001 |ig/L - 0.01 |ig/L with frequencies of detection that
ranged from 0 percent to 100 percent in influents, and average detected
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concentrations of PFOS that ranged from <0.001 |ig/L - 0.0094 |ig/L with
frequencies of detection that ranged from 0 percent to 100 percent in effluents.
• Three utilities with medium wastewater impact exhibited average detected
concentrations of PFOS that ranged from 0.0014 |ig/L - 0.022 |ig/L with frequencies
of detection that ranged from 50 percent to 100 percent in influents, and average
detected concentrations of PFOS that ranged from 0.0014 |ig/L - 0.022 |ig/L with
frequencies of detection that ranged from 43 percent to 100 percent in effluents.
• Two utilities with high wastewater impact exhibited average detected concentrations
of PFOS that ranged from 0.029 |ig/L - 0.041 |ig/L with frequencies of detection of
100 percent in both influents, and average detected concentrations of PFOS that
ranged from <0.001 |ig/L - 0.057 |ig/L with frequencies of detection that ranged from
0 percent to 100 percent in effluents.
EPA / United States Geological Survey (USGS') Nationwide Reconnaissance of Contaminants
of Emerging Concern
As part of a joint study by EPA and USGS to assess human exposure to contaminants of
emerging concern, water samples were collected from 25 drinking water treatment plants in 24
states (Glassmeyer et al., 2017). Participation in the study was voluntary. Final sample locations
were chosen to represent a wide range of geography, diversity in disinfectant type used, and a
range of production volumes. Phase I of the study (2007) analyzed a subset of contaminants and
sites to test experimental design; PFOS was not included in Phase 1. During Phase II of the study
(2010-2012), samples were collected from groundwater and surface water sources as well as
treated drinking water from 25 drinking water treatment plants and analyzed for PFOS
occurrence. The Lowest Concentration Minimum Reporting Level (LCMRL) was 0.00013 (J,g/L.
Results from Phase II are presented in Exhibit 3-14. Of the 25 source water samples, 88
percent exceeded the lowest concentration minimum reporting level (LCMRL). In treated water,
80 percent of samples exceeded the LCMRL. The maximum detected concentration in source
water was 0.0483 [j,g/L which is less than the HRL but greater than one-half the HRL. The
maximum detected concentration in treated water was 0.0369 [j,g/L which is also less than the
HRL but greater than one-half the HRL.
Exhibit 3-14: Drinking Water Treatment Plants - Summary of PFOS Samples
(Glassmeyer et al., 2017)
Source Water Type
Number of
Samples
All Detections
Median
Concentration
(ng/L)
Maximum
Concentration
(ng/L)
Number
Percent
Source Water
25
22
88%
0.00228
0.0483
Treated Drinking Water
25
20
80%
0.00162
0.0369
Source: Glassmeyer et al., 2017
A second published study by the same research team (Boone et al., 2019) compared the
team's findings at 24 of the participating PWSs in 2010-2012 with UCMR 3 results from the
same PWSs in 2013-2015. Detection frequencies were higher in the Boone et al. (2019) study
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than under UCMR 3, which is not surprising given the difference in reporting levels. With an
LCMRL of 0.00013 (J,g/L, Boone et al. (2019) found quantifiable levels of PFOS at 9 (79
percent) of the 24 systems (This information is in the supplemental tables that accompany the
study.) Under UCMR 3, with an MRL of 0.04 |ig/L, no detections were reported from the 24
systems; however, concentrations observed in the Boone et al. (2019) study tended to be lower
than concentrations observed under UCMR 3. The highest finished water concentration of PFOS
observed by Boone et al. (2019), 0.0369 |ig/L, is less than the HRL, while concentrations of up
to 7 |ig/L were observed in UCMR 3.
3.4.3 Other Data
The Centers for Disease Control and Prevention (CDC) Fourth National Report on Human
Exposure to Environmental Chemicals and Updated Tables, 1999-2000 and 2003-2016
Since 1999, the National Health and Nutrition Examination Survey (NHANES) has
examined the U.S. population annually and released the data in 2-year cycles. The survey is
based on a representative sample of the U.S. population based on age, gender, and race/ethnicity
(CDC, 2019). Published studies of NHANES data indicate that in early cycles PFOS was
detected in over 99 percent of samples (Kato et al., 2011). The Fourth National Report on
Human Exposure to Environmental Chemicals was published in 2009 (CDC, 2009). The
exposure data tables have been updated several times since the original publication, most
recently in 2019 (CDC, 2019). The 2019 updated tables include the PFOS exposure data
originally reported in the 2009 report, plus data from all of the subsequent updates. Exhibit 3-15
presents the 95th percentile values of PFOS analyzed in serum from years 1999 through 2016.
Overall, the concentrations in serum decreased over time. Please note that these 95th percentile
values cannot be directly compared to the HRL since the values represent human serum
concentrations, not drinking water concentrations. PFOS in human tissue can have its origin in
exposure via drinking water, food, or other routes.
Exhibit 3-15: 95th Percentiles of Serum PFOS Concentrations,
1999-2000 and 2003-2016
Year Range
Medium
Analyzed
95th
Percentile of
All Samples
(ng/L)
95%
Confidence
Interval (|jg/L)
Sample Size
1999-2000
Serum
75.7
58.1-97.5
1,562
2003-2004
Serum
54.6
44.0-66.5
2,094
2005-2006
Serum
47.5
42.7-56.8
2,120
2007-2008
Serum
40.5
35.4-47.4
2,100
2009-2010
Serum
32.0
22.6-48.5
2,233
2011-2012
Serum
21.7
19.3-23.9
1,904
2013-2014
Serum
18.5
15.4-22.0
2,165
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Year Range
Medium
Analyzed
95th
Percentile of
All Samples
(ng/L)
95%
Confidence
Interval (|jg/L)
Sample Size
2015-2016
Serum
18.3
15.5-22.7
1,993
Source: CDC, 2019
The limit of detection (LOD) for 1999-2000, 2006-2006, 2007-2008, 2009-2010, and
2011-2012 is 0.2 |jg/L; for 2003-2004 it is 0.4 pg/L. Starting in 2013-2014, CDC
measured linear/straight-chain PFOS and branched isomers of PFOS separately. The
results are reported both separately and as a sum, the latter of which is intended to be
comparable to data from earlier years. The sums are reported in this table. LODs are
not established for summed data.
3.4.4 Combined PFOS and PFOA and Other Co-Occurrence Analyses
This section presents occurrence analyses for summed PFOS and PFOA concentrations
from data sources that provide both PFOS and PFOA results for the same sample. UCMR 3 and
several state monitoring data sets were amenable to this type of analysis. In addition, this section
summarizes UCMR 3 results for PFAS published by non-EPA researchers, including co-
occurrence analyses involving PFOS and PFOA.
UCMR 3
An analysis of the sum of the PFOS and PFOA concentrations was conducted using the
UCMR 3 data. Concentrations of PFOS and PFOA from individual water samples were summed;
non-detections were set equal to zero for the purpose of this analysis. Samples with
PFOS+PFOA concentrations greater than zero were considered to be detections. Furthermore,
the sum of PFOS+PFOA concentrations were rounded to two decimal places in those cases
where a laboratory reported more digits. The two compounds' common HRL of 0.07 |ig/L was
applied in this analysis. Results are presented in Exhibit 3-16 through Exhibit 3-20.
A total of 36,971 finished water samples were included in the analysis. Of these samples,
1.37 percent had reported detections (at or above their respective MRL thresholds) of one or both
contaminants. The sum of reported PFOS and PFOA concentrations ranged from 0.02 |ig/L (the
MRL for PFOA) to 7.22 |ig/L. Of 4,920 systems, 162 (3.3 percent of systems, serving 5.9
percent of the PWS-served population) reported at least one detection. A total of 116 PWSs (2.4
percent of PWSs, serving 4.7 percent of the PWS-served population) reported at least one
detection greater than one-half the HRL of 0.035 |ig/L and 63 PWSs (1.3 percent of PWSs,
serving 2.3 percent of the PWS-served population) reported at least one detection greater than
the HRL of 0.07 |ig/L.
Extrapolating these findings suggests that an estimated 360 PWSs serving 11.8 million
people nationally would have at least one instance of a PFOS+PFOA concentration greater than
one-half the HRL in finished water and an estimated 202 PWSs serving 5.7 million people
nationally would have at least one instance of a PFOS+PFOA concentration greater than the
HRL in finished water. An explanation of the extrapolation methodology is presented in
Chapter 2.
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January 2021
Exhibit 3-16: PFOS+PFOA Occurrence Data from UCMR 3 Assessment Monitoring
- Summary of Concentrations
Source Water Type
Concentration Value (|jg/L)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Small Systems (serving < 10,000 people)
Groundwater
0.262
0.30
0.32
0.33
0.33
Surface Water
0.05
0.06
0.17
0.20
0.20605
All Small Systems
0.05
0.09
0.28
0.33
0.33
Large Systems (serving 10,001 -100,000 people) — CENSUS
Groundwater
0.02
0.05
0.19
0.71
0.773
Surface Water
0.02
0.06
0.22
1.42
7.22
All Large Systems
0.02
0.05
0.21
1.18
7.22
Very Large Systems (serving > 100,000 people) — CENSUS
Groundwater
0.032
0.07
0.33
0.50
0.53
Surface Water
0.02
0.04
0.10
1.08
1.94
All Very Large Systems
0.02
0.05
0.16
0.90
1.94
All Systems
All Water Systems
0.02
0.05
0.20
1.08
7.22
Source: USEPA, 2017b
Exhibit 3-17: PFOS+PFOA National Occurrence Measures Based on UCMR 3
Assessment Monitoring Data - Summary of Samples
Source Water Type
Total # of
Samples
Samples with
Detections
Samples with
Concentrations
> 1/2 HRL (0.035 |jg/L)
Samples with
Concentrations
> HRL (0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Small Systems
serving < 10,000 people)
Groundwater
1,853
2
0.11%
2
0.11%
2
0.11%
Surface Water
1,421
6
0.42%
6
0.42%
2
0.14%
All Small Systems
3,274
8
0.24%
8
0.24%
4
0.12%
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
11,707
136
1.16%
86
0.73%
41
0.35%
Surface Water
14,859
230
1.55%
158
1.06%
101
0.68%
All Large Systems
26,566
366
1.38%
244
0.92%
142
0.53%
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
2,020
32
1.58%
31
1.53%
16
0.79%
Surface Water
5,111
100
1.96%
64
1.25%
25
0.49%
All Very Large Systems
7,131
132
1.85%
95
1.33%
41
0.57%
All Systems
All Water Systems
36,971
506
1.37%
347
0.94%
187
0.51%
Source: USEPA, 2017b
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January 2021
Exhibit 3-18: PFOS+PFOA National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data -
Summary of System and Population Served Data - Detections
Source Water Type
UCMR 3 Sample
Number With At Least
One Detection
Percent With At Least
One Detection
National Inventory1
National Estimate
of Number With At Least
One Detection2
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Groundwater
527
1,498,845
1
536
0.19%
0.04%
55,700
38,730,597
106
13,900
Surface Water
272
1,250,215
4
30,686
1.47%
2.45%
9,728
20,007,917
143
491,000
All Small Systems
799
2,749,060
5
31,222
0.63%
1.14%
65,428
58,738,514
249
505,000
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
1,453
37,141,418
49
1,618,210
3.37%
4.36%
1,470
37,540,614
49
1,620,000
Surface Water
2,260
69,619,878
73
2,494,024
3.23%
3.58%
2,310
70,791,005
73
2,490,000
All Large Systems
3,713
106,761,296
122
4,112,234
3.29%
3.85%
3,780
108,331,619
122
4,110,000
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
68
16,355,951
11
4,969,185
16.18%
30.38%
68
16,355,951
11
4,970,000
Surface Water
340
115,158,260
24
5,155,984
7.06%
4.48%
343
120,785,622
24
5,160,000
All Very Large Systems
408
131,514,211
35
10,125,169
8.58%
7.70%
411
137,141,573
35
10,100,000
All Systems
All Water Systems
4,920
241,024,567
162
14,268,625
3.29%
5.92%
69,619
304,211,706
406
14,700,000
Source: USEPA, 2017b
1 The small system national inventory numbers for systems and population served by systems were derived from a freeze of the December 2010 SDWIS/Fed data.
These counts are based on all community and non-transient non-community water systems that served 10,000 people or fewer. All large and very large systems were
required to conduct UCMR 3 Assessment Monitoring; thus, the national inventory numbers for the large and very large systems are based on the number of systems
expected to complete UCMR 3 monitoring. SDWIS inventory data from 2010 were used for the UCMR 3 national extrapolations as these data were consistent with the
UCMR 3 inventory data at the timeframe of the UCMR 3 sample design.
2 National estimates for the small systems are generated by multiplying the UCMR 3 national statistical sample findings of system/population percentages and national
system/population inventory numbers for PWSs. National estimates for the large and very large systems are based directly on the UCMR 3 results, since this was a
census. Due to rounding, some calculations may appear to be slightly off.
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Exhibit 3-19: PFOS+PFOA National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data -
Summary of System and Population Served Data - Concentrations > 1/2 HRL (0.035 |jg/L)
Source Water Type
UCMR 3 Sample
Number With At Least
One Concentration
> 1/2 HRL (0.035 |jg/L)
Percent With At Least
One Concentration
> 1/2 HRL (0.035 |jg/L)
National Inventory1
National Estimate of
Number With At Least
One Concentration
> 1/2 HRL2
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Groundwater
527
1,498,845
1
536
0.19%
0.04%
55,700
38,730,597
106
13,900
Surface Water
272
1,250,215
4
30,686
1.47%
2.45%
9,728
20,007,917
143
491,000
All Small Systems
799
2,749,060
5
31,222
0.63%
1.14%
65,428
58,738,514
249
505,000
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
1,453
37,141,418
38
1,348,817
2.62%
3.63%
1,470
37,540,614
38
1,350,000
Surface Water
2,260
69,619,878
46
1,590,131
2.04%
2.28%
2,310
70,791,005
46
1,590,000
All Large Systems
3,713
106,761,296
84
2,938,948
2.26%
2.75%
3,780
108,331,619
84
2,940,000
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
68
16,355,951
10
4,849,185
14.71%
29.65%
68
16,355,951
10
4,850,000
Surface Water
340
115,158,260
17
3,510,417
5.00%
3.05%
343
120,785,622
17
3,510,000
All Very Large Systems
408
131,514,211
27
8,359,602
6.62%
6.36%
411
137,141,573
27
8,360,000
All Systems
All Water Systems
4,920
241,024,567
116
11,329,772
2.36%
4.70%
69,619
304,211,706
360
11,800,000
Source: USEPA, 2017b
1 The small system national inventory numbers for systems and population served by systems were derived from a freeze of the December 2010 SDWIS/Fed data.
These counts are based on all community and non-transient non-community water systems that served 10,000 people or fewer. All large and very large systems were
required to conduct UCMR 3 Assessment Monitoring; thus, the national inventory numbers for the large and very large systems are based on the number of systems
expected to complete UCMR 3 monitoring. SDWIS inventory data from 2010 were used for the UCMR 3 national extrapolations as these data were consistent with the
UCMR 3 inventory data at the timeframe of the UCMR 3 sample design.
2 National estimates for the small systems are generated by multiplying the UCMR 3 national statistical sample findings of system/population percentages and national
system/population inventory numbers for PWSs. National estimates for the large and very large systems are based directly on the UCMR 3 results, since this was a
census. Due to rounding, some calculations may appear to be slightly off.
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January 2021
Exhibit 3-20: PFOS+PFOA National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data -
Summary of System and Population Served Data -- Concentrations > HRL (0.07 |jg/L)
Source Water Type
UCMR 3 Sample
Number With At Least
One Concentration
> HRL (0.07 |jg/L)
Percent With At Least
One Concentration
> HRL (0.07 |jg/L)
National Inventory1
National Estimate of
Number With At Least One
Detected Concentration
> HRL2
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Groundwater
527
1,498,845
1
536
0.19%
0.04%
55,700
38,730,597
106
13,900
Surface Water
272
1,250,215
1
8,323
0.37%
0.67%
9,728
20,007,917
36
133,000
All Small Systems
799
2,749,060
2
8,859
0.25%
0.32%
65,428
58,738,514
141
147,000
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
1,453
37,141,418
17
482,992
1.17%
1.30%
1,470
37,540,614
17
483,000
Surface Water
2,260
69,619,878
30
848,125
1.33%
1.22%
2,310
70,791,005
30
848,000
All Large Systems
3,713
106,761,296
47
1,331,117
1.27%
1.25%
3,780
108,331,619
47
1,331,000
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
68
16,355,951
5
1,741,685
7.35%
10.65%
68
16,355,951
5
1,740,000
Surface Water
340
115,158,260
9
2,425,751
2.65%
2.11%
343
120,785,622
9
2,430,000
All Very Large Systems
408
131,514,211
14
4,167,436
3.43%
3.17%
411
137,141,573
14
4,170,000
All Systems
All Water Systems
4,920
241,024,567
63
5,507,412
1.28%
2.29%
69,619
304,211,706
202
5,646,000
Source: USEPA, 2017b
1 The small system national inventory numbers for systems and population served by systems were derived from a freeze of the December 2010 SDWIS/Fed data.
These counts are based on all community and non-transient non-community water systems that served 10,000 people or fewer. All large and very large systems were
required to conduct UCMR 3 Assessment Monitoring; thus, the national inventory numbers for the large and very large systems are based on the number of systems
expected to complete UCMR 3 monitoring. SDWIS inventory data from 2010 were used for the UCMR 3 national extrapolations as these data were consistent with the
UCMR 3 inventory data at the timeframe of the UCMR 3 sample design.
2 National estimates for the small systems are generated by multiplying the UCMR 3 national statistical sample findings of system/population percentages and national
system/population inventory numbers for PWSs. National estimates for the large and very large systems are based directly on the UCMR 3 results, since this was a
census. Due to rounding, some calculations may appear to be slightly off.
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January 2021
State Monitoring Data, 2013 - 2020
PFAS monitoring data sets from eleven states (Alabama, Colorado (2020), Georgia,
Kentucky, Missouri, New Hampshire, New Jersey, North Dakota, Ohio, and Vermont) permitted
combined PFOS+PFOA occurrence analysis. (To be included in the analysis, the underlying data
needed to allow for the PFOS and PFOA to be summed at the sample level.) The PFOS and
PFOA reported results for some states (e.g., California and Massachusetts) could not be included
in the summed analysis because the PFOS and PFOA concentrations could not be linked (and,
therefore, summed) at the individual sample level for these states. Five states (Arizona, Colorado
(2013-2017), Maine, and Rhode Island) directly reported PFOS+PFOA monitoring results. A
summary of PFOS+PFOA data from state monitoring data sets is presented in Exhibit 3-21
through Exhibit 3-23. Note that some states (e.g., Colorado, Michigan, and New Hampshire)
conducted multiple, unique sampling efforts over different time periods. A description of all
sampling efforts, including date range and a description of coverage and representativeness, is
included in Exhibit 3-9. Overall, detected concentrations ranged from 0.000229 |ig/L (Maine) to
2.5 |ig/L (Ohio). Eleven states included in the analysis had at least one detection of PFOS+PFOA
concentrations greater than the HRL of 0.07 |ig/L. Four states did not have any detections of
PFOS+PFOA concentrations greater than the HRL.
Exhibit 3-21: PFOS+PFOA State Drinking Water Occurrence Data - Summary of
Concentrations
State
Source Water Type1
(Sample Type)
Concentration Value (|jg/L)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Alabama
(2020)
Groundwater (Finished)
0.008
0.017
0.037
0.048
0.049
Surface Water (Finished)
0.003
0.020
0.037
0.059
0.062
Total3
0.003
0.018
0.040
0.060
0.062
Arizona
(2018)
Groundwater (Finished)
0.003
0.039
0.095
0.157
0.166
Surface Water (Finished)
0.015
0.023
0.048
0.055
0.056
Total3
0.003
0.031
0.088
0.154
0.166
Colorado
(2013-2017)
Distribution (Finished)
0.0028
0.09
0.14
0.28
0.3
Surface Water (Finished)
ND
ND
ND
ND
ND
Total3
0.0028
0.09
0.14
0.28
0.3
Colorado
(2020)
Groundwater (Raw)
0.00053
0.0054
0.0118
0.031226
0.039
Groundwater (Finished)
0.00045
0.0027
0.01208
0.022954
0.0273
Surface water (Raw)
0.00086
0.0156
0.04
0.814
1.006
Surface water (Finished)
0.00047
0.004
0.00953
0.015602
0.0172
Total3
0.00045
0.0046
0.01696
0.11912
1.006
Georgia
(2020)
Surface Water (Raw)
ND
ND
ND
ND
ND
Surface Water (Finished)
0.098
0.098
0.098
0.098
0.098
Surface Water (Not Provided)4
0.088
0.092
0.094
0.095
0.095
Total3
0.088
0.095
0.097
0.098
0.098
Kentucky
(2019)
Groundwater (Finished)
0.00109
0.00508
0.017439
0.0396339
0.0421
Surface Water (Finished)
0.00101
0.00242
0.007246
0.009294
0.00956
Total3
0.00101
0.00247
0.007342
0.0303856
0.0421
Maine
(2013-2020)
Not Provided5 (Raw)
0.000327
0.01164
0.09265
0.42055
0.47
Not Provided5 (Finished)
0.000229
0.0114
0.097632
0.2812
0.29
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State
Source Water Type1
(Sample Type)
Concentration Value (|jg/L)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Not Provided6
0.00206
0.0084
0.01136
0.011846
0.0119
Total3
0.000229
0.0112
0.09265
0.40825
0.47
Michigan
(2018-2019,
Phase I)2
Groundwater (Raw)
0.002
0.0045
0.0185
0.029
0.029
Groundwater (Finished)
0.002
0.006
0.966
1.4958
1.52
Groundwater (Not Provided)4
0.023
0.023
0.023
0.023
0.023
Surface water (Raw)
0.002
0.002
0.0061
0.01051
0.011
Surface water (Finished)
0.002
0.002
0.004
0.00736
0.008
Not Provided5 (Finished)
ND
ND
ND
ND
ND
Total3
0.002
0.004
0.0254
1.4298
1.52
Michigan
(2019, Phase II)2
Groundwater (Raw)
0.002
0.006
0.0631
0.16214
0.201
Groundwater (Finished)
0.005
0.042
0.0516
0.05376
0.054
Total3
0.002
0.007
0.0594
0.15544
0.201
Michigan
(2019 Monthly)2
Surface Water (Raw)
0.002
0.003
0.01049
0.839
1.629
Surface Water (Finished)
0.002
0.003
0.0122
0.02024
0.026
Total3
0.002
0.003
0.01141
0.04555
1.629
Michigan
(2019 Quarterly)2
Groundwater (Raw)
0.002
0.009
0.032
0.05352
0.066
Groundwater (Finished)
0.002
0.007
0.0302
0.06132
0.066
Groundwater (Not Provided)4
0.023
0.024
0.024
0.024
0.024
Surface water (Raw)
ND
ND
ND
ND
ND
Surface water (Finished)
ND
ND
ND
ND
ND
Surface Water (Not Provided)4
ND
ND
ND
ND
ND
Not Provided5 (Raw)
0.002
0.006
0.0096
0.01176
0.012
Not Provided5 (Finished)
0.005
0.006
0.007
0.007
0.007
Total3
0.002
0.007
0.03
0.06312
0.066
Missouri
(2016-2017)
Not Provided5 (Raw)
0.00024
0.00053
0.00172
0.001981
0.00201
Not Provided5 (Finished)
0.00024
0.00046
0.001222
0.0016514
0.00172
Total3
0.00024
0.000485
0.00153
0.0019375
0.00201
New Hampshire
(2013-2017)
Groundwater (Finished)
0.0004
0.006
0.019
0.08
0.242
Surface Water (Finished)
0.002
0.003
0.01
0.02
0.0216
Not Provided5 (Finished)
0.013
0.016
0.018
0.019
0.019
Total3
0.0004
0.006
0.019
0.076
0.242
New Hampshire
(2019)
Groundwater (Finished)
0.00178
0.00817
0.0251
0.10254
0.2901
Surface Water (Finished)
0.0014
0.005
0.007891
0.014626
0.01573
Not Provided5 (Finished)
0.00318
0.0064
0.008976
0.0095556
0.00962
Total3
0.0014
0.00764
0.023992
0.080674
0.2901
New Jersey
(2019-2020)
Groundwater (Finished)
0.00051
0.0104
0.034
0.128
0.646
Surface Water (Finished)
0.0007
0.012535
0.03348
0.045
0.074
Not Provided5 (Finished)
0.71
1.24
1.628
1.7198
1.73
Total3
0.00051
0.0108
0.034
0.12368
1.73
North Dakota
(2018)
Not Provided5 (Raw)
0.00061
0.00079
0.001564
0.0020104
0.00206
Not Provided5 (Finished)
0.00045
0.00117
0.001642
0.0018472
0.00187
Total3
0.00045
0.000855
0.001889
0.0020429
0.00206
Ohio
(2020)
Groundwater (Raw)
0.0052
0.01605
0.0532
1.8366
2.5
Groundwater (Finished)
0.0059
0.012
0.03926
0.06124
0.066
Surface Water (Raw)
0.005
0.0058
0.010235
0.0136235
0.014
Surface Water (Finished)
0.0054
0.0055
0.00676
0.006796
0.0068
3-42
-------
EPA - OGWDW
Final Regulatory Determination 4 Support Document - Ch 3, PFOS
January 2021
State
Source Water Type1
(Sample Type)
Concentration Value (|jg/L)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Total3
0.005
0.0117
0.04257
0.9806
2.5
Pennsylvania
(2019)
Groundwater (Finished)
0.0021
0.0064
0.0139
0.0955
0.1140
Surface Water (Finished)
0.002
0.00945
0.01452
0.023867
0.025
Total3
0.002
0.007
0.015
0.086
0.114
Rhode Island
(2017-2019)
Groundwater (Finished)
0.004
0.0115
0.0262
0.10178
0.114
Surface Water (Finished)
0.004
0.011
0.0274
0.04358
0.046
Not Provided5 (Finished)
0.003
0.008
0.0306
0.0418
0.043
Total3
0.003
0.011
0.0287
0.09242
0.114
Vermont
(2019-2020)
Groundwater (Finished)
0.002
0.007
0.028
0.083
0.187
Surface Water (Finished)
ND
ND
ND
ND
ND
Not Provided5 (Finished)
ND
ND
ND
ND
ND
Total3
0.002
0.007
0.028
0.083
0.187
ND = no detections in this category
1 Whenever possible, systems' source water type information was derived from a freeze of the December 2019
SDWIS/Fed data.
2 See Exhibit 3-9 for more information on Michigan monitoring data.
3 Total rows display the minimum, median, 90th percentile, 99th percentile, and maximum concentration values from
the entire state data set, regardless of water type or sample type.
4 The results were not identified in the state data set as having been collected from raw or finished water.
5 The results were not identified in the state data set as having been collected from groundwater or surface water.
6 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
Exhibit 3-22: PFOS+PFOA State Drinking Water Occurrence Data - Summary of
Samples
State
Source Water Type1
(Sample Type)
Total # of
Samples
All Detections
Concentrations
> 1/2 HRL (0.035 |jg/L)
Concentrations
> HRL (0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Alabama2
(2020)
Groundwater
(Finished)
-
7
-
1
-
0
-
Surface Water
(Finished)
-
10
-
1
-
0
-
Total
-
17
-
2
-
0
-
Arizona
(2018)
Groundwater
(Finished)
97
16
16.49%
8
8.25%
6
6.19%
Surface Water
(Finished)
12
4
33.33%
1
8.33%
0
0.00%
Total
109
20
18.35%
9
8.26%
6
5.50%
Colorado
(2013-2017)
Distribution (Finished)
96
38
39.58%
28
29.17%
20
20.83%
Surface Water
(Finished)
11
0
0.00%
0
0.00%
0
0.00%
Total
107
38
35.51%
28
26.17%
20
18.69%
Colorado
(2020)
Groundwater
(Raw)
87
47
54.02%
1
1.15%
0
0.00%
Groundwater
(Finished)
345
83
24.06%
0
0.00%
0
0.00%
Surface water
(Raw)
43
31
72.09%
6
13.95%
3
6.98%
3-43
-------
EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 3, PFOS January 2021
State
Source Water Type1
(Sample Type)
Total # of
Samples
All Detections
Concentrations
> 1/2 HRL (0.035 |jg/L)
Concentrations
> HRL (0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Surface water
(Finished)
238
48
20.17%
0
0.00%
0
0.00%
Total
713
209
29.31%
7
0.98%
3
0.42%
Surface Water
(Raw)
1
0
0.00%
0
0.00%
0
0.00%
Georgia
(2020)
Surface Water
(Finished)
2
1
50.00%
1
50.00%
1
50.00%
Surface Water
(Not Provided)4
2
2
100.00%
2
100.00%
2
100.00
%
Total
5
3
60.00%
3
60.00%
3
60.00%
Kentucky
(2019)
Groundwater
(Finished)
38
8
21.05%
1
2.63%
0
0.00%
Surface Water
(Finished)
43
29
67.44%
0
0.00%
0
0.00%
Total
81
37
45.68%
1
1.23%
0
0.00%
Not Provided5
(Raw)
240
146
60.83%
56
23.33%
21
8.75%
Maine
(2013-2020)
Not Provided5
(Finished)
86
23
26.74%
5
5.81%
3
3.49%
Not Provided6
21
7
33.33%
0
0.00%
0
0.00%
Total
347
176
50.72%
61
17.58%
24
6.92%
Groundwater
(Raw)
811
34
4.19%
0
0.00%
0
0.00%
Groundwater
(Finished)
785
23
2.93%
6
0.76%
6
0.76%
Michigan
(2018-2019,
Phase I)3
Groundwater (Not
Provided)4
2
1
50.00%
0
0.00%
0
0.00%
Surface water
(Raw)
72
8
11.11%
0
0.00%
0
0.00%
Surface water
(Finished)
150
17
11.33%
0
0.00%
0
0.00%
Not Provided5
(Finished)
4
0
0.00%
0
0.00%
0
0.00%
Total
1,824
83
4.55%
6
0.33%
6
0.33%
Michigan
(2019, Phase
II)3
Groundwater
(Raw)
716
30
4.19%
5
0.70%
1
0.14%
Groundwater
(Finished)
183
5
2.73%
3
1.64%
0
0.00%
Total3
899
35
3.89%
8
0.89%
1
0.11%
Michigan
(2019 Monthly)3
Surface Water
(Raw)
485
51
10.52%
2
0.41%
1
0.21%
Surface Water
(Finished)
583
65
11.15%
0
0.00%
0
0.00%
Total
1,068
116
10.86%
2
0.19%
1
0.09%
Groundwater
(Raw)
259
149
57.53%
9
3.47%
0
0.00%
Groundwater
(Finished)
170
79
46.47%
6
3.53%
0
0.00%
Michigan
(2019
Quarterly)3
Groundwater
(Not Provided)4
4
4
100.00%
0
0.00%
0
0.00%
Surface water
(Raw)
2
0
0.00%
0
0.00%
0
0.00%
Surface water
(Finished)
16
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)4
0
0
0.00%
0
0.00%
0
0.00%
3-44
-------
EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 3, PFOS January 2021
State
Source Water Type1
(Sample Type)
Total # of
Samples
All Detections
Concentrations
> 1/2 HRL (0.035 |jg/L)
Concentrations
> HRL (0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Not Provided5
(Raw)
9
9
100.00%
0
0.00%
0
0.00%
Not Provided5
(Finished)
15
8
53.33%
0
0.00%
0
0.00%
Total
475
249
52.42%
15
3.16%
0
0.00%
Missouri
(2016-2017)
Not Provided5
(Raw)
26
11
42.31%
0
0.00%
0
0.00%
Not Provided5
(Finished)
29
15
51.72%
0
0.00%
0
0.00%
Total
55
26
47.27%
0
0.00%
0
0.00%
New
Hampshire
(2013-2017)
Groundwater
(Finished)4
471
241
51.17%
9
1.91%
3
0.64%
Surface Water
(Finished)4
107
19
17.76%
0
0.00%
0
0.00%
Not Provided5
(Finished)
6
2
33.33%
0
0.00%
0
0.00%
Total
584
262
44.86%
9
1.54%
3
0.51%
New
Hampshire
(2019)
Groundwater
(Finished)4
866
261
30.14%
14
1.62%
3
0.35%
Surface Water
(Finished)4
74
24
32.43%
0
0.00%
0
0.00%
Not Provided5
(Finished)
5
2
40.00%
0
0.00%
0
0.00%
Total
945
287
30.37%
14
1.48%
3
0.32%
New Jersey
(2019-2020)
Groundwater
(Finished)
7,009
2948
42.06%
271
3.87%
56
0.80%
Surface Water
(Finished)
936
632
67.52%
44
4.70%
1
0.11%
Not Provided5
(Finished)
12
4
33.33%
4
33.33%
4
33.33%
Total
7,957
3584
45.04%
319
4.01%
61
0.77%
North Dakota
(2018)
Not Provided5
(Raw)
7
5
71.43%
0
0.00%
0
0.00%
Not Provided5
(Finished)
7
5
71.43%
0
0.00%
0
0.00%
Total
14
10
71.43%
0
0.00%
0
0.00%
Ohio
(2020)
Groundwater
(Raw)
587
32
5.45%
8
1.36%
2
0.34%
Groundwater
(Finished)
719
29
4.03%
4
0.56%
0
0.00%
Surface Water
(Raw)
38
6
15.79%
0
0.00%
0
0.00%
Surface Water
(Finished)
40
5
12.50%
0
0.00%
0
0.00%
Total
1,384
72
5.20%
12
0.87%
2
0.14%
Pennsylvania
(2019)
Groundwater
(Finished)
76
20
26.32%
1
1.32%
1
1.32%
Surface Water
(Finished)
20
12
60.00%
0
0.00%
0
0.00%
Total
96
32
33.33%
1
1.04%
1
1.04%
Rhode Island
(2017-2019)
Groundwater
(Finished)
153
48
31.37%
3
1.96%
2
1.31%
Surface Water
(Finished)
37
23
62.16%
1
2.70%
0
0.00%
3-45
-------
EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 3, PFOS January 2021
State
Source Water Type1
(Sample Type)
Total # of
Samples
All Detections
Concentrations
> 1/2 HRL (0.035 |jg/L)
Concentrations
> HRL (0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Not Provided5
(Finished)
31
13
41.94%
1
3.23%
0
0.00%
Total
221
84
38.01%
5
2.26%
2
0.90%
Groundwater
(Finished)
634
70
11.04%
4
0.63%
1
0.16%
Vermont
(2019-2020)
Surface Water
(Finished)
55
0
0.00%
0
0.00%
0
0.00%
Not Provided5
(Finished)
6
0
0.00%
0
0.00%
0
0.00%
Total
695
70
10.07%
4
0.58%
1
0.14%
1 Whenever possible, systems' source water type information was derived from a freeze of the December 2019
SDWIS/Fed data.
2 Only data for detections were available from Alabama.
3 See Exhibit 3-9 for more information on Michigan monitoring data.
4 The results were not identified in the state data set as having been collected from raw or finished water.
5 The results were not identified in the state data set as having been collected from groundwater or surface water.
6 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
Exhibit 3-23: PFOS+PFOA State Drinking Water Occurrence Data - Summary of
Systems
State
Source Water Type1
(Sample Type)
Total # of
Systems/Sites
Systems/Sites with
Detections
Systems/Sites with
Concentrations >
1/2 HRL (0.035 |jg/L)
Systems/Sites with
Concentrations
> HRL (0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Alabama2
(2020)
Groundwater
(Finished)
-
5
-
1
-
0
-
Surface Water
(Finished)
-
8
-
1
-
0
-
Total
-
13
-
2
-
0
-
Arizona
(2018)
Groundwater
(Finished)
61
13
21.31%
6
9.84%
4
6.56%
Surface Water
(Finished)
7
3
42.86%
1
14.29%
0
0.00%
Total
68
16
23.53%
7
10.29%
4
5.88%
Colorado3
(2013-2017)
Distribution (Finished)
23
12
52.17%
10
43.48%
7
30.43%
Surface Water
(Finished)
5
0
0.00%
0
0.00%
0
0.00%
Total
28
12
42.86%
10
35.71%
7
25.00%
Colorado
(2020)
Groundwater
(Raw)
24
14
58.33%
1
4.17%
0
0.00%
Groundwater
(Finished)
225
62
27.56%
0
0.00%
0
0.00%
Surface water
(Raw)
9
7
77.78%
3
33.33%
2
22.22%
Surface water
(Finished)
172
39
22.67%
0
0.00%
0
0.00%
Total
400
109
27.25%
4
1.00%
2
0.50%
Georgia
(2020)
Surface Water
(Raw)
1
0
0.00%
0
0.00%
0
0.00%
3-46
-------
EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 3, PFOS January 2021
State
Source Water Type1
(Sample Type)
Total # of
Systems/Sites
Systems/Sites with
Detections
Systems/Sites with
Concentrations >
1/2 HRL (0.035 |jg/L)
Systems/Sites with
Concentrations
> HRL (0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Surface Water
(Finished)
1
1
100.00%
1
100.00%
1
100.00%
Surface Water
(Not Provided)9
1
1
100.00%
1
100.00%
1
100.00%
Total
1
1
100.00%
1
100.00%
1
100.00%
Kentucky4
(2019)
Groundwater
(Finished)
38
8
21.05%
1
2.63%
0
0.00%
Surface Water
(Finished)
43
29
67.44%
0.00%
0
0.00%
Total
81
37
45.68%
1
1.23%
0
0.00%
Not Provided10
(Raw)
37
25
67.57%
11
29.73%
6
16.22%
Maine5
(2013-2020)
Not Provided10
(Finished)
23
9
39.13%
4
17.39%
2
8.70%
Not Provided11
9
6
66.67%
0
0.00%
0
0.00%
Total
60
33
55.00%
13
21.67%
7
11.67%
Groundwater
(Raw)
579
25
4.32%
0
0.00%
0
0.00%
Groundwater
(Finished)
505
15
2.97%
1
0.20%
1
0.20%
Michigan
(2018-2019,
Phase I)6
Groundwater (Not
Provided)4
2
1
50.00%
0
0.00%
0
0.00%
Surface water
(Raw)
65
8
12.31%
0
0.00%
0
0.00%
Surface water
(Finished)
73
14
19.18%
0
0.00%
0
0.00%
Not Provided5
(Finished)
4
0
0.00%
0
0.00%
0
0.00%
Total
1,122
58
5.17%
1
0.09%
1
0.09%
Michigan
(2019, Phase
II)6
Groundwater
(Raw)
540
22
4.07%
3
0.56%
1
0.19%
Groundwater
(Finished)
159
3
1.89%
2
1.26%
0
0.00%
Total3
690
25
3.62%
5
0.72%
1
0.14%
Surface Water
(Raw)
67
21
31.34%
2
2.99%
1
1.49%
Michigan
(2019 Monthly)6
Surface Water
(Finished)
67
19
28.36%
0
0.00%
0
0.00%
Total3
68
28
41.18%
2
2.94%
1
1.47%
Groundwater
(Raw)
57
41
71.93%
5
8.77%
0
0.00%
Groundwater
(Finished)
39
24
61.54%
3
7.69%
0
0.00%
Michigan
(2019
Quarterly)6
Groundwater
(Not Provided)9
1
1
100.00%
0
0.00%
0
0.00%
Surface water
(Raw)
2
0
0.00%
0
0.00%
0
0.00%
Surface water
(Finished)
4
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)9
0
0
0.00%
0
0.00%
0
0.00%
Not Provided10
(Raw)
4
4
100.00%
0
0.00%
0
0.00%
3-47
-------
EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 3, PFOS January 2021
State
Source Water Type1
(Sample Type)
Total # of
Systems/Sites
Systems/Sites with
Detections
Systems/Sites with
Concentrations >
1/2 HRL (0.035 |jg/L)
Systems/Sites with
Concentrations
> HRL (0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Not Provided10
(Finished)
4
2
50.00%
0
0.00%
0
0.00%
Total3
86
59
68.60%
7
8.14%
0
0.00%
Missouri7
(2016-2017)
Not Provided10
(Raw)
14
7
50.00%
0
0.00%
0
0.00%
Not Provided10
(Finished)
15
10
66.67%
0
0.00%
0
0.00%
Total
15
11
73.33%
0
0.00%
0
0.00%
New
Hampshire
(2013-2017)
Groundwater
(Finished)9
265
97
36.60%
7
2.64%
3
1.13%
Surface Water
(Finished)9
24
10
41.67%
0
0.00%
0
0.00%
Not Provided10
(Finished)
6
2
33.33%
0
0.00%
0
0.00%
Total
295
108
36.61%
7
2.37%
3
1.02%
New
Hampshire
(2019)
Groundwater
(Finished)
743
230
30.96%
14
1.88%
3
0.40%
Surface Water
(Finished)
37
12
32.43%
0
0.00%
0
0.00%
Not Provided10
(Finished)
5
2
40.00%
0
0.00%
0
0.00%
Total
785
244
31.08%
14
1.78%
3
0.38%
New Jersey
(2019-2020)
Groundwater
(Finished)
1,120
559
49.91%
68
6.07%
14
1.25%
Surface Water
(Finished)
98
77
78.57%
10
10.20%
1
1.02%
Not Provided10
(Finished)
4
1
25.00%
1
25.00%
1
25.00%
Total
1,222
637
52.13%
79
6.46%
16
1.31%
North Dakota8
(2018)
Not Provided10
(Raw)
7
5
71.43%
0
0.00%
0
0.00%
Not Provided10
(Finished)
7
5
71.43%
0
0.00%
0
0.00%
Total
7
5
71.43%
0
0.00%
0
0.00%
Ohio
(2020)
Groundwater
(Raw)
545
28
5.14%
6
1.10%
2
0.37%
Groundwater
(Finished)
663
26
3.92%
2
0.30%
0
0.00%
Surface Water
(Raw)
30
6
20.00%
0
0.00%
0
0.00%
Surface Water
(Finished)
30
5
16.67%
0
0.00%
0
0.00%
Total
694
40
5.76%
6
0.86%
2
0.29%
Pennsylvania
(2019)
Groundwater
(Finished)
72
18
25.00%
1
1.39%
1
1.39%
Surface Water
(Finished)
15
8
53.33%
0
0.00%
0
0.00%
Total
87
26
29.89%
1
1.15%
1
1.15%
Rhode Island
(2017-2019)
Groundwater
(Finished)
70
21
30.00%
1
1.43%
1
1.43%
Surface Water
(Finished)
6
5
83.33%
1
16.67%
0
0.00%
Not Provided10
(Finished)
11
7
63.64%
1
9.09%
0
0.00%
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State
Source Water Type1
(Sample Type)
Total # of
Systems/Sites
Systems/Sites with
Detections
Systems/Sites with
Concentrations >
1/2 HRL (0.035 |jg/L)
Systems/Sites with
Concentrations
> HRL (0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Total
87
33
37.93%
3
3.45%
1
1.15%
Vermont
(2019-2020)
Groundwater
(Finished)
547
52
9.51%
3
0.55%
1
0.18%
Surface Water
(Finished)
43
0
0.00%
0
0.00%
0
0.00%
Not Provided10
(Finished)
2
0
0.00%
0
0.00%
0
0.00%
Total
592
52
8.78%
3
0.51%
1
0.17%
1 Whenever possible, systems' source water type information was derived from a freeze of the December 2019
SDWIS/Fed data.
2 Only data for detections were available from Alabama.
3 For the Colorado distribution system samples collected between 2013 and 2017, "systems" were counted as unique
zones in which the sample was distributed.
4 For Kentucky, "systems" were counted as unique location names as PWSIDs from SDWIS/Fed could not always be
linked with the location names.
5 For Maine, "systems" were counted as unique site names as PWSIDs from SDWIS/Fed could not always be linked
with the site names.
6 See Exhibit 3-9 for more information on Michigan monitoring data.
7 For Missouri, "systems" were counted as unique facility numbers in which the sample was collected.
8 For North Dakota, "systems" were counted as unique sites in which the sample was collected.
9 The results were not identified in the state data set as having been collected from raw or finished water.
10 The results were not identified in the state data set as having been collected from groundwater or surface water.
11 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
In addition to the monitoring data available from public water systems, North Carolina
has made data from 17 private wells associated with the Chemours facility in Fayetteville
available (NCDEQ, 2018). The maximum combined PFOS and PFOA concentration was 0.0319
|ig/L, while the median was 0.004 |ig/L. Summed PFOS and PFOA concentrations did not
exceed the EPA HRL (0.07 |ig/L) at any of the sampling sites. Note that EPA does not regulate
private drinking water wells but may evaluate data from private wells where the data may be
indicative of contaminants in aquifers that are used as sources for public water system wells.
Additional UCMR 3 Analyses from Published Studies
Adamson et al. (2017) and Guelfo and Adamson (2018) conducted independent analyses
of UCMR 3 data for six PFASs (PFOA and PFOS, plus perfluoroheptanoate (PFHpA),
perfluorononanoate (PFNA), perfluorobutane sulfonate (PFBS), and perfluorohexane sulfonate
(PFHxS)) and other contaminants. Some care should be taken when comparing their UCMR 3
occurrence findings with results presented elsewhere in this document. Note, for example, that
these researchers appeared to have been working with a "near-final" data set of 36,139 samples
(Guelfo and Adamson, 2018), whereas the final UCMR 3 data set included 36,972 samples for
most PFAS.
Guelfo and Adamson (2018) examined PFAS results from UCMR 3 in detail, addressing
co-occurrence among the six PFAS compounds, relationships to sources, and temporal trends
over the UCMR 3 sampling period. They found that approximately 50 percent of samples with
reportable levels of one or more PFAS detections contained at least two PFAS and 72 percent of
detections occurred in groundwater. Large PWSs (>10,000 customers) were 5.6 times more
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likely than small PWSs (<10,000 customers) to exhibit PFAS detections; however, when
detected, median total PFAS concentrations were higher in small PWSs (0.12 (J,g/L) than in large
(0.053 (J,g/L). The authors performed pairwise co-occurrence analyses using both a categorical
(chi square) analysis based on sample detections and a calculation of odds ratios for co-occurring
pairs also based on sample detections. All of the pairwise categorical results showed statistically
significant co-occurrence, with the exception of PFBS and PFNA for which there was no
observed co-occurrence. The odds ratio results, presented in Exhibit 3-24, also showed a strong
likelihood of co-occurrence between all PFAS pairs other than PFNA and PFBS. (Odds ratios >
1 suggest co-occurrence greater than that expected by chance; odds ratios of 0 to <1 indicate co-
occurrence less than that expected by chance. While the magnitude of the values shown in
Exhibit 3-24 suggest the odds ratios are likely to be statistically significant given the sample size,
the authors did not specifically present p value results for these odds ratios.)
Exhibit 3-24: Co-Occurrence Matrix (Odds Ratios for Association Between PFAS
Pairs)
PFOS
PFOA
PFHxS
PFHpA
PFBS
PFNA
PFOS
-
216
876
295
371
46
PFOA
216
-
242
407
538
57
PFHxS
876
242
-
389
107
65
PFHpA
295
407
389
-
463
94
PFBS
371
538
107
463
-
0
PFNA
46
57
65
94
0
-
Source: Guelfo and Adamson, 2018
Note: All pairwise findings were statistically significant (p<0.05) for the categorical (chi square) analysis of observed
versus expected co-occurrence, except for the PFBS and PFNA pair where no co-occurrence was observed. The
authors did not provide p value results for the computed odds ratios presented here.
Guelfo and Adamson (2018) also conducted a cluster analysis for assessing co-
occurrence relationships between PFAS based on both detection and concentration. The authors
identified two notable clusters among co-occurring PFAS, one involving PFOA and PFHpA and
the other involving PFOS and PFHxS. The authors also noted that the lack of co-occurrence
between PFNA and PFBS could have been an artifact of low individual detection rates but also
could be attributed to factors related to use and environmental transport for these two
compounds.
With respect to sources, the authors observed that perfluoroalkyl sulfonates, PFSAs (i.e.,
PFOS, PFHxS, PFBS) tended to dominate over perfluoroalkyl carboxylates, or PFCAs (i.e.,
PFOA, PFHpA, PFNA) in groundwater, while PFCAs tended to dominate over PFSAs in surface
water. PFSAs tend to be associated with uses such as fire-fighting foam, mist suppressants, and
surface protection products, while PFCA releases tend to be associated with fluoropolymer
manufacturing, landfills, and water treatment plant effluent.
Guelfo and Adamson (2018) evaluated temporal trends using two different
methodologies: linear regression and a Mann-Kendall test. In an examination of quarterly
detection rates for all six PFAS together, both analyses showed an increasing trend over twelve
quarters; however, only the Mann-Kendall results were statistically significant (p = 0.03).
Further analysis (apparently using the Mann-Kendall test alone) showed increasing trends as well
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for PFOA alone (statistically significant; p = 0.01) and PFOS alone (not statistically significant;
P = 01).
In an earlier related study, Adamson et al. (2017) calculated odds ratios to examine co-
occurrence between 1,4-dioxane and other UCMR 3 contaminants, including PFOS and PFOA.
Statistically significant (at a 95 percent confidence level) co-occurrence was observed with both
PFOS and PFOA. Based on calculated odds ratios, samples with a 1,4-dioxane detection were
14.2 times more likely to occur with a PFOS detection than without a PFOS detection when
adjusted for system size. Similarly, samples with a 1,4-dioxane detection were 13.4 times more
likely to occur with a PFOA detection than without a PFOA detection when adjusted for system
size.
Hu et al. (2016) presented a spatial analysis of PFAS concentrations under UCMR 3 and
found that the number of industrial sites that manufacture or use these compounds, the number of
military fire training areas, and the number of wastewater treatment plants are all significant
predictors of PFAS detection frequencies and concentrations in public water supplies. The
authors found that for PFAS monitored under UCMR 3, the detection frequency in drinking
water sourced from groundwater was more than twice that from surface water. Additionally,
PFOA and PFOS were more frequently detected in groundwater whereas UCMR 3 PFAS
compounds with shorter chain lengths were detected more frequently in surface waters. Hu et al.
(2016) noted that this observation could be due to the original mode of environmental release
(aerosol, application to soil, and aqueous discharge).
3.5 Analytical Methods
EPA has published three analytical methods that are available for the analysis of PFOS
and other PFAS in drinking water:
• EPAMethod 537, Version 1.1, Determination of Selected Perfluorinated Alkyl Acids
in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tcindem
Mass Spectrometry (LC/MS/MS). The LCMRL generated by the laboratory that
developed the method is 6.5 ng/L. Mean recoveries in fortified reagent water,
chlorinated groundwater, and high-total organic carbon (TOC) chlorinated surface
water range from 100 to 116%, with Relative Standard Deviations (RSDs) of 2.2 to
4.1% (USEPA, 2009).
• EPA Method 537.1, Version 1.0, Determination of Selected Per- and Polyfluorinated
Alkyl Substances in Drinking Water by Solid Phase Extraction and Liquid
Chromatography/Tandem Mass Spectrometry (LC/MS/MS). The LCMRL generated
by the laboratory that developed the method is 2.7 ng/L. Mean recoveries in fortified
reagent water, tap water (from groundwater and surface water sources), and private
well water range from 93.5 to 111%, with RSDs of 1.9 to 5.9% (USEPA, 2018c).
• EPA Method 533, Determination of Per- and Polyfluoroalkyl Substances in Drinking
Water by Isotope Dilution Anion Exchange Solid Phase Extraction and Liquid
Chromatography / Tandem Mass Spectrometry (USEPA, 2019d).
Laboratories participating in UCMR 3 were required to use EPA Method 537 and, as
described in Section 0, were required to report PFOS values at or above the EPA-defined MRL
of 0.04 |ig/L (77 FR 26072; USEPA, 2012). The MRL was set based on the capability of
multiple laboratories at the time.
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3.6 Treatment Technologies
EPA evaluates whether suitable treatment technologies are available prior to
promulgating a final National Primary Drinking Water Regulation (NPDWR).
EPA's Drinking Water Treatability Database (USEPA, 2020b) summarizes available
technical literature on the efficacy of treatment technologies for a range of priority drinking
water contaminants. According to the Database, the following processes are considered effective
for the removal of PFOS: granular activated carbon, or GAC (up to > 99 percent removal),
membrane separation with high pressure membranes such as nanofiltration and reverse osmosis
(up to > 99 percent removal), anion exchange (up to > 99 percent removal), and powdered
activated carbon (up to 99 percent removal). The exact percentage removal a water system may
achieve with a given technology will be dependent upon a variety of factors, including source
water quality and water system characteristics. GAC and anion exchange are non-steady state
technologies where the adsorbent media will need to be periodically replaced or
reactivated/regenerated to prevent contaminant breakthrough.
Both GAC and anion exchange are more effective at removing long-chain PFAS than
short-chain PFAS (Dickenson and Higgins, 2016; Ross et al., 2018). GAC systems appear to
have a faster breakthrough for perfluoroalkyl carboxylates (such as PFOA) than for
perfluoroalkyl sulfonates (such as PFOS) of equivalent chain lengths (Ross et al., 2018). Anion
exchange resins, similarly, have been shown to have a greater affinity for perfluoroalkyl
sulfonates than for perfluoroalkyl carboxylates (Dickenson and Higgins, 2016). Thus, when
mixed PFAS are in the source water, short-chain perfluoroalkyl carboxylates are likely to break
through before other PFAS. Competition with natural organic matter can interfere with the
effectiveness of GAC for the removal of PFAS compounds (Ross et al., 2018; Dickenson and
Higgins, 2016).
Crone et al. (2019) and Speth et al. (2019) analyzed the advantages and disadvantages of
some of the more promising treatment technologies for the removal of PFAS substances. For
PFAS removal, GAC is one of the most commonly reported and evaluated treatment technology
in the literature. The treatment efficacy of GAC is strongly dependent upon the type of PFAS
present and physio-chemical properties of the solution matrix. The use of GAC for the removal
of PFAS will also remove other co-contaminants and help maintain disinfectant residuals and
control disinfection byproducts by removing disinfection byproduct precursors (Crone et al.,
2019; Crone et al., 2019). However, certain poorly adsorbed PFAS will break through the
adsorber quickly, and it is important to consider reactivation/removal frequency and the cost of
disposal or reactivation of spent carbon, and the potential for overshoot (i.e., higher
concentrations of a contaminant in the effluent than the influent, due to preferential adsorption of
other contaminants) if a GAC system is poorly designed or operated (Crone et al., 2019; Speth et
al., 2019).
Anion exchange resins have a high capacity for some PFAS, they can remove select co-
contaminants, and they require smaller beds than GAC. Additionally, they can pair well with
other technologies for removing a broad range of PFAS that may not be readily removed with a
single treatment technology (Crone et al., 2019). However, like GAC, they may have short run
times for select PFAS and be subject to competitive adsorption. They may also have resin
disposal issues, and like GAC, they may have a potential for overshoot if poorly designed or
operated (Speth et al. 2019).
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High pressure membranes like reverse osmosis and nanofiltration are effective for
removing a wide range of PFAS, will remove other co-contaminants, and will help maintain
disinfection residuals by removing disinfection byproduct precursors. However, they have high
capital and operations costs (Crone et al., 2019; Speth et al., 2019). Additionally, membrane
fouling, corrosion control, and the disposal or treatment of concentrate stream are issues that
need to be addressed (Crone et al., 2019; Speth et al., 2019).
According to EPA's Drinking Water Treatability Database, processes ineffective for the
removal of PFOS include aeration, biological treatment, chloramines, chlorine, chlorine dioxide,
conventional treatment (comprised of the unit processes coagulation, flocculation, clarification,
and filtration), hydrogen peroxide, ozone, ozone plus hydrogen peroxide, slow sand filtration,
ultraviolet (UV) photocatalysis using titanium dioxide, and UV irradiation plus ozone. Other
treatment processes with varying results include biological filtration, low-pressure membrane
filtration, such as microfiltration and ultrafiltration, and permanganate. Some of the percent
removal values reported in the Database (e.g., for conventional treatment and permanganate) are
higher than reasonably anticipated due to a variety of factors such as study conditions differing
from the conditions of typical drinking water facilities, outlier datapoints, or multiple treatment
processes being run simultaneously (USEPA, 2020b).
For more information about treatment technologies discussed here, see the Health
Advisory for PFOS (USEPA, 2016c) and the Drinking Water Treatability Database (USEPA
2020b).
3.7 References
Adamson, D.T., E.A. Pina, A.E. Cartwright, S.R. Rauch, R.H. Anderson, T. Mohr, and J.A.
Connor. 2017. 1,4-Dioxane drinking water occurrence data from the third unregulated
contaminant monitoring rule. Science of the Total Environment vol. 596, pp. 236-245.
Agency for Toxic Substances and Disease Registry (ATSDR). 2008. Public Health Assessment
for Perfluorochemical Contamination in Lake Elmo and Oakdale, Washington County,
Minnesota, EPA facility ID: MND 980704738, MND 980609515. Agency for Toxic
Substances and Disease Registry, Public Health Service, United States Department of
Health and Human Services, Atlanta, Georgia, May. Available on the Internet at:
https://www.atsdr.cdc.gov/HAC/pha/PFCsLakeElmo/PFCs in Lake Elmo PHA 8-29-
2008 508.pdf.
Alabama Department of Environmental Management (ADEM). 2020. Per- and Polyfluoroalkyl
Substances (PFAS) in Drinking Water. Quarter 1: January 1, 2020 - March 31, 2020
PFAS Detections.
Alaska Department of Environmental Conservation (Alaska DEC). 2020. Division of Spill
Prevention and Response. Per- and Polyfluoroalkyl Substances (PFAS). Drinking Water
Sample Results. Available on the Internet at: https://dec.alaska.gov/spar/csp/pfas/sample-
results/#above.
Arizona Department of Environmental Quality (ADEQ). 2018. Arizona's Public Water System
Screening for Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS)
Final Report. Available on the Internet at:
http://static.azdeq.gov/wqd/reports/pfoapfosepareport final.pdf.
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Agency for Toxic Substances and Disease Registry (ATSDR). 2008. Public Health Assessment
for Perfluorochemical Contamination in Lake Elmo and Oakdale, Washington County,
Minnesota. EPA Facility ID: MND9807047'38 AND MND980609515. Final Releases,
August 29, 2008. Available on the Internet at:
https://www.atsdr.cdc.gov/HAC/pha/PFCsLakeElmo/PFCs in Lake Elmo PHA 8-29-
2008 508.pdf.
ATSDR. 2018. Toxicological Profile for Perfluoroalkyls. Draft for Public Comment. Agency for
Toxic Substances and Disease Registry, Public Health Service, United States Department
of Health and Human Services, Atlanta, GA. Available on the Internet at:
http://www.atsdr.cdc.gov/ToxProfiles/tp200.pdf.
Boone, J.S., C. Vigo, T. Boone, C. Byrne, J. Ferrario, R. Benson, J. Donohue, J.E. Simmons,
D.W. Kolpin, E.T. Furlong, and S.T. Glassmeyer. 2019. Per- and polyfluoroalkyl
substances in source and treated drinking waters of the United States. Science of The
Total Environment Vol. 653 (February 25), pp. 359-369.
Boulanger, B., J. Vargo, J.L. Schnoor, and K.C. Hornbuckle. 2004. Detection of perfluorooctane
surfactants in Great Lakes water. Environmental Science and Technology 38(15):4064-
4070.
Buck, R.C., J. Franklin, U. Berger, J.M. Conder, I.T. Cousins, P. de Voogt, A.A. Jensen, K.
Kannan, S.A. Mabury and S.P.J, van Leeuwen. 2011. Perfluoroalkyl and polyfluoroalkyl
substances in the environment: Terminology, classification, and origins. Society of
Environmental Toxicology and Chemistry 7(4):513-541. Available on the Internet at:
https://setac.onlinelibrarv.wilev.com/doi/full/10.10Q2/ieam.258.
Butenhoff, J.L., G.L. Kennedy, Jr., S.-C. Chang, and G.W. Olsen. 2012. Chronic dietary toxicity
and carcinogenicity study with ammonium perfluorooctanoate in Sprague-Dawley rats.
Toxicol. 298:1- 13.
California Division of Drinking Water (CADDW). 2020. Perfluorooctanoic acid (PFOA) and
Perfluorooctanesulfonic acid (PFOS). Available on the Internet at:
https://www.waterboards.ca.gov/drinking water/certlic/drinkingwater/EDTlibrary.html.
Accessed July 2020.
Calafat, A.M., L-Y Wong, Z. Kuklenyik, J. A. Reidy, and L.L. Needham. 2007. Polyfluoroalkyl
Chemicals in the U.S. Population: Data from the National Health and Nutrition
Examination Survey (NHANES) 2003-2004 and Comparisons withNHANES 1999-
2000. Environ Health Perspect. 115(11): 1596-1602.
Calafat, A.M., K. Kato, K. Hubbard, et al. 2019. Legacy and alternative per and polyfluoroalkyl
substances in the U.S. general population: Paired serum-urine data from the 2013-2014
National Health and Nutrition Examination Survey, Environment International 131:
105048.
Centers for Disease Control and Prevention (CDC). 2009. Fourth National Report on Human
Exposure to Environmental Chemicals, Department of Health and Human Services,
Centers for Disease Control and Prevention. Available on the Internet at:
https://www.cdc.gov/exposurereport/pdf/fourthreport.pdf.
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CDC. 2019. Fourth National Report on Human Exposure to Environmental Chemicals, Updated
Tables, January 2019, Volume 1. Department of Health and Human Services, Centers for
Disease Control and Prevention. Available on the Internet at:
https://www.cdc.gov/exposurereport/pdf/FourthReport UpdatedTables Volumel Jan201
9-508.pdf.
ChemlDPlus. 2019. Profile for Perfluorooctane sulfonic acid. Available on the Internet at:
http://chem.sis.nlm.nih.gov/chemidplus/. Accessed March 18, 2019.
Colorado Department of Public Health and Environment (CDPHE). 2018. Perfluorinated
compound levels in environmental water samples. Updated August 7, 2018. Available on
the Internet at:
https://environmentalrecords.colorado.gov/HPRMWebDrawer/RecordView/1208017.
CDPHE. 2020. 2020 PFAS Sampling Project, Downloadable Data. Available on the Internet at:
https://cohealthviz.dphe.state.co.us/t/EnvironmentalEpidemiologyPublic/views/PFAS res
ults DRAFT/Download?%3AshowAppBanner=false&%3Adisplav count=n&%3Ashow
VizHome=n&%3Aorigin=viz share link&%3AisGuestRedirectFromVizportal=v&%3A
embed=v.
Crone, B.C., T.F. Speth, D.G. Wahman, S.J. Smith, G. Abulikemu, E.J. Kleiner and J.G. Pressman.
2019. Occurrence of per- and polyfluoroalkyl substances (PFAS) in source water and their
treatment in drinking water. Critical Reviews in Environmental Science and Technology
49:(24):23 59-2396.
Dickenson, E.R.V., and C. Higgins. 2016. Treatment Mitigation Strategies for Poly- and
Perfluoroalkyl Substances. Web Report #4322. Water Research Foundation. Denver, CO.
Georgia Environmental Protection Division (GA EPD). 2020. EPA Sampling Report for
Summerville. Available on the Internet at: https://epd.georgia.gov/pfoa-and-pfos-
information.
Glassmeyer, S.T., E.T. Furlong, D.W. Kolpin, A.L. Batt, R. Benson, J. S. Boone, O. Conerly,
M.J. Donohue, D.N. King, M.S. Kostich, H.E. Mash, S.L. Pfaller, K.M. Schenck, J.E.
Simmons, E.A. Varughese, S.J. Vesper, E.N. Villegas, and V.S. Wilson. 2017.
Nationwide Reconnaissance of Contaminants of Emerging Concern in Source and
Treated Drinking Waters of the United States. Science of the Total Environment (581-
582):909-922.
Goeden, H. and J. Kelly. 2006. Targeted Sampling 2004-2005. Perfluorochemicals in Minnesota,
MN DOH, February 27.
Guelfo, J.L. and D.T. Adamson. 2018. Evaluation of a national data set for insights into sources,
composition, and concentrations of per- and polyfluoroalkyl substances (PFASs) in U.S.
drinking water. Environmental Pollution vol. 236 (May), pp.505-513.
Hansen, K.J., H.O. Johnson, J.S. Elridge, J.L. Butenhoff, and L.A. Dick. 2002. Quantitative
characterization of trace levels of PFOS and PFOA in the Tennessee River.
Environmental Science and Technology 36(8): 1681-1685.
Hazardous Substances Data Bank (HSDB). 2016. Profile for Perfluorooctane sulfonic acid.
Available on the Internet at: http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen7HSDB. Last
revision date October 25, 2016.
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Hu X.C., D.Q. Andrews, A.B. Lindstrom, T.A. Bruton, L.A. Schaider, P. Grandjean, et al. 2016.
Detection of poly- and perfluoroalkyl substances (PFASs) in U.S. drinking water linked
to industrial sites, military fire training areas, and wastewater treatment plants. Environ
Sci TechnolLett 3(10):344-350.
Iowa Department of Natural Resources (Iowa DNR). 2020. PFAS Action Plan. Available on the
Internet at: https://www.iowadnr.gov/Environmental-Protection/PFAS.
Interstate Technology & Regulatory Council (ITRC). 2020a. Naming Conventions and Physical
and Chemical Properties of Per- and Polyfluoroalkyl Substances (PFAS). Available on
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USEPA. 2013. Perfluoroalkyl Sulfonates and LongChain Perfluoroalkyl Carboxylate Chemical
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05/documents/pfos health advisory final 508.pdf.
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Acid (PFOA). EPA 505-F-17-001. Available on the Internet at:
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12/documents/ffrrofactsheet contaminants pfos pfoa 11-20-17 508 O.pdf.
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USEPA. 2019b. Occurrence Data from the Third Unregulated Contaminant Monitoring Rule
(UCMR 3). EPA 815-R-19-007.
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Drinking Water by Isotope Dilution Anion Exchange Solid Phase Extraction and Liquid
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New Use Rule: Long-Chain Perfluoroalkyl Carboxylate andPerfluoroalkyl Sulfonate
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QPPT-2013-0225-0232.
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(PFCs) in Maryland Waterways."
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Sampling-Report-7.10.18-FINAL.pdf.
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https://dec.vermont.gov/water/drinking-water/water-qualitv-monitoring/pfas.
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Wilson, L.R. 2018. New York State Drinking Water Data: PFOA andPFOS. Bureau of Water
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http://www.nvsac.org/files/NYS%20Drinking%20Water%20Data%20PFQAs.pdf.
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Yoo, H., J.W. Washington, T.M. Jenkins, and J.J. Ellington. 2011. Quantitative Determination of
Perfluorochemicals and Fluorotelomer Alcohols in Plants from Biosolid-Amended Fields
using LC/MS/MS and GC/MS. Environ. Sci. Technol. 45(19):7985-7990.
Zareitalabad, P., J. Siemens, M. Hamer, and W. Amelung. 2013. Perfluorooctanoic Acid (PFOA)
and Perfluorooctanesulfonic Acid (PFOS) in Surface Waters, Sediments, Soils, and
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91:725-732.
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Chapter 4:
PFOA
A chapter from:
Final Regulatory Determination 4 Support Document
EPA Report 815-R-21-001
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Contents
Contents 4-2
Exhibits 4-3
Abbreviations 4-4
4.1 Contaminant Background, Chemical and Physical Properties 4-6
4.2 Sources and Environmental Fate 4-9
4.2.1 Production, Use, and Release 4-9
4.2.2 Environmental Fate 4-10
4.3 Health Effects 4-11
4.4 Occurrence 4-13
4.4.1 Occurrence in Ambient Water 4-13
4.4.2 Occurrence in Drinking Water 4-15
4.4.3 Other Data 4-37
4.5 Analytical Methods 4-38
4.6 Treatment Technologies 4-39
4.7 References 4-40
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Exhibits
Exhibit 4-1: Chemical Structure of PFOA 4-8
Exhibit 4-2: Physical and Chemical Properties of PFOA 4-8
Exhibit 4-3: IUR Reported Annual Manufacture and Importation of PFOA in the United
States, 1986-2006 (pounds) 4-10
Exhibit 4-4: CDR Reported Annual Manufacture and Importation of PFOA in the United
States, 2011-2015 (pounds) 4-10
Exhibit 4-5: PFOA STORET Data - Summary of Detected Concentrations 4-14
Exhibit 4-6: PFOA STORET Data - Summary of Samples and Sites 4-14
Exhibit 4-7: PFOA STORET Data - Summary of States 4-14
Exhibit 4-8: PFOA Occurrence Data from UCMR 3 Assessment Monitoring - Summary of
Detected Concentrations 4-17
Exhibit 4-9: PFOA National Occurrence Measures Based on UCMR 3 Assessment
Monitoring Data - Summary of Samples 4-18
Exhibit 4-10: PFOA National Occurrence Measures Based on UCMR 3 Assessment
Monitoring Data- Summary of System and Population Served Data — Detections 4-19
Exhibit 4-11: PFOA National Occurrence Measures Based on UCMR 3 Assessment
Monitoring Data- Summary of System and Population Served Data — Detections > '/2
HRL (0.035 Lig/I.) 4-20
Exhibit 4-12: PFOA National Occurrence Measures Based on UCMR 3 Assessment
Monitoring Data - Summary of System and Population Served Data - Detections >
HRL (0.07 Lig/I.) 4-21
Exhibit 4-13: Summary of Available Primary State Monitoring Data 4-22
Exhibit 4-14: PFOA Primary State Drinking Water Occurrence Data - Summary of Detected
Concentrations 4-25
Exhibit 4-15: PFOA Primary State Drinking Water Occurrence Data - Summary of Samples 4-27
Exhibit 4-16: PFOA Primary State Drinking Water Occurrence Data - Summary of Systems 4-30
Exhibit 4-17: Summary of New York State PFOA-PFOS Sampling Results 4-35
Exhibit 4-18: Drinking Water Treatment Plants - Summary of PFOA Samples (Glassmeyer et
al., 2017) 4-37
Exhibit 4-19: 95th Percentiles of Serum PFOA Concentrations, 1999-2000 and 2003-2016.... 4-38
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Abbreviations
ADEQ
Arizona Department of Environmental Quality
Alaska DEC
Alaska Department of Environmental Conservation
BW
Body Weight
CAS
Chemical Abstracts Service
CCL 4
Fourth Contaminant Candidate List
CDC
Centers for Disease Control and Prevention
CDPHE
Colorado Department of Public Health and Environment
CDR
Chemical Data Reporting
CSF
Cancer Slope Factor
DWI
Drinking Water Intake
EPA
Environmental Protection Agency
EPISuite™
Estimation Programs Interface Suite™
GAEPD
Georgia Environmental Protection Division
GAC
Granular Activated Carbon
GWUDI
Groundwater Under the Direct Influence of Surface Water
HA
Health Advisory
HESD
Health Effects Support Document
HRL
Health Reference Level
HSDB
Hazardous Substances Data Bank
I ARC
International Agency for Research on Cancer
Iowa ANG
Iowa Air National Guard
Iowa DNR
Iowa Department of Natural Resources
IUR
Inventory Update Reporting
Kh
Henry's Law Constant
Koc
Organic Carbon Partitioning Coefficient
Kow
Octanol-Water Partitioning Coefficient
LCMRL
Lowest Concentration Minimum Reporting Level
LC/MS/MS
Liquid Chromatography/Tandem Mass Spectrometry
LOD
Limit of Detection
MDH
Minnesota Department of Health
Michigan EGLE
Michigan Department of Environment, Great Lakes, and Energy
Missouri DNR
Missouri Department of Natural Resources
MP ART
Michigan PFAS Action Response Team
MPCA
Minnesota Pollution Control Agency
MRL
Minimum Reporting Level
NAWQA
National Water Quality Assessment
NCDEQ
North Carolina Department of Environmental Quality
ND
No Detection
NDEQ
Nebraska Department of Environmental Quality
Nebraska DHHS
Nebraska Department of Health and Human Services
NHANES
National Health and Nutrition Examination Survey
NHDES
New Hampshire Department of Environmental Services
NIRS
National Inorganics and Radionuclides Survey
NJDEP
New Jersey Department of Environmental Protection
NPDWR
National Primary Drinking Water Regulation
NYS
New York State
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NYSDOH
New York State Department of Health
PFAA
Perfluorinated Alkyl Acid
PFAS
Per- and Polyfluoroalkyl Substances
PFBA
Perfluorobutanoic Acid
PFOA
Perfluorooctanoic Acid
PFOS
Perfluorooctanesulfonic Acid
PFPeA
Per fluoropentanoic Acid
pKa
Acid Dissociation Constant
PWS
Public Water System
RfD
Reference Dose
RIDOH
Rhode Island Department of Health
RSC
Relative Source Contribution
RSD
Relative Standard Deviation
SDWIS/Fed
Safe Drinking Water Information System/Federal Version
SNUR
Significant New Use Rule
STORET
Storage and Retrieval Data System
TOC
Total Organic Carbon
TRI
Toxic Release Inventory
TSCA
Toxic Substances Control Act
UCM
Unregulated Contaminant Monitoring
UCMR
Unregulated Contaminant Monitoring Rule
UCMR 1
First Unregulated Contaminant Monitoring Rule
UCMR 2
Second Unregulated Contaminant Monitoring Rule
UCMR 3
Third Unregulated Contaminant Monitoring Rule
USGS
United States Geological Survey
UV
Ultraviolet
VT DEC
Vermont Department of Environmental Conservation
WQP
Water Quality Portal
WTP
Water Treatment Plant
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Chapter 4: PFOA
The Environmental Protection Agency (EPA) is evaluating perfluorooctanoic acid
(PFOA) as a candidate for regulation as a drinking water contaminant under the fourth
Contaminant Candidate List (CCL 4) Regulatory Determinations process. Information on the
CCL 4 process is found in Chapter 1. Background on data sources used to evaluate CCL 4
chemicals is found in Chapter 2.
This chapter presents information and analysis specific to PFOA, including background
information on the contaminant, information on contaminant sources and environmental fate, an
analysis of health effects, an analysis of occurrence in ambient and drinking water, and
information about the availability of analytical methods and treatment technologies.
4.1 Contaminant Background, Chemical and Physical Properties
Synonyms for PFOA include pentadecafluorooctanoic acid; perfluorocaprylic acid;
perfluoroctanoic acid; perfluoroheptanecarboxylic acid; and octanoic acid, pentadecafluoro-,
according to the Hazardous Substances Data Bank (HSDB, 2016). PFOA belongs to a group of
substances known as per- and polyfluoroalkyl substances (PFAS).
PFOA is a perfluorinated aliphatic carboxylic acid. It has been used as an emulsifier and
surfactant in fluoropolymers (such as in the manufacture of non-stick products like Teflon), fire-
fighting foams, cosmetics, greases and lubricants, paints, polishes, and adhesives (HSDB, 2016).
Through EPA's 2010/2015 PFOA Stewardship Program, a voluntary risk reduction program,
eight major chemical manufacturers agreed in 2006 to phase out the use of PFOA and PFOA-
related chemicals in their products and as emissions from their facilities by 2015. All
participating companies state that they met the PFOA Stewardship Program goals (USEPA,
2018a). PFOA may still be used by other companies not participating in the PFOA Stewardship
Program. In addition, PFOA can also be present in imported articles (USEPA, 2017a).
EPA amended a Significant New Use Rule (SNUR) for PFAS in 2013 to cover PFOA-
related long-chain perfluoroalkyl carboxylate substances (78 FR 62443, USEPA, 2013). The
2013 amendment required companies to provide notice to EPA if they intend to manufacture,
import, or process PFOA-related long-chain perfluoroalkyl carboxylates for use in carpet
manufacture or treatment, with limited exceptions (namely, for two long-chain perfluoroalkyl
carboxylates already in use as surfactants in carpet cleaning products). The 2013 amendment also
required reporting from those who intend to import carpets that already contain long-chain
perfluoroalkyl carboxylates. In 2015, EPA proposed a SNUR to require manufacturers (including
importers) and processors of perfluorooctanoic acid (PFOA) and related chemicals (including as
part of articles), to notify EPA at least 90 days before starting or resuming new uses of these
chemicals in any products (80 FR 2885, USEPA, 2015). The 2015 proposed amendment would
strengthen the requirements for the carpet industry and extended the SNUR for PFOA and
PFOA-related long-chain perfluoroalkyl carboxylates to all uses subject to the voluntary phase-
out. EPA finalized the 2015 SNUR amendments in 2020 (EPA-HQ-OPPT-2013-0225, USEPA,
2020a). The 2020 final SNUR gives EPA the authority to review an extensive list of products
containing PFAS before they are manufactured, sold, or imported in the United States. The final
rule requires notice and EPA review prior to the new use of long-chain PFAS that have been
nationally phased out, thus strengthening the regulation of PFAS. In addition, products that
contain particular long-chain PFAS as a surface coating and carpet containing perfluoroalkyl
sulfonate chemical substances must undergo EPA review to be imported into the United States
(USEPA, 2020b).
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PFOA has been detected in up to 98% of serum samples taken in biomonitoring studies
that are representative of the U.S. general population. Since PFOA production has been
voluntarily phased out by major manufacturers in the U.S., serum concentrations in the U.S.
population have been declining (CDC, 2019). National Health and Nutrition Examination Survey
(NHANES) biomonitoring data are discussed further in section 4.4.3.
PFOA may also be formed in the environment as a terminal degradation product of
commercial PFAS produced by fluorotelomerization and electrochemical fluorination.
Perfluorooctane sulfonyl fluoride, 8:2 fluorotelomer alcohols, 8:2 fluorotelomer acrylates, and N-
alkyl sulfonamido PFAS such as A'-methyl perfluorooctanesulfonamido ethanol and TV-ethyl
perfluorooctanesulfonamido ethanol are used to produce surfactants and polymers that may
degrade to PFOA (ITRC, 2020a; ITRC, 2020b; Buck et al., 2011).
The diagram in Exhibit 4-1 shows the straight-chain chemical structure of PFOA. PFOA
and related compounds can exist as either branched-chain or linear-chain isomers depending on
their method of manufacture (ATSDR, 2018). Physical and chemical properties and other
reference information are listed in Exhibit 4-2 (these properties typically represent mixtures of
branched and linear isomers rather than any particular isomer). There is uncertainty as to whether
values for certain physical/chemical properties of PFOA can be measured or estimated. For
example, HSDB (2016) reports a value for the log octanol/water partitioning coefficient (log
Kow) that is estimated using EPA's Estimation Programs Interface Suite™ (EPISuite™), while
ATSDR (2018) and Lange et al. (2006) indicate that log Kow cannot be measured since PFOA is
expected to form multiple layers in octanol and water mixtures. While uncharged and very long-
chain perfluoroalkyls form layers in water/hydrocarbon mixtures, forms that are charged/ionized
at typical environmental pH (such as PFOA) are fairly soluble in water (ATSDR, 2018). Another
example of apparent uncertainty is the Henry's Law Constant (Kh). HSDB (2016) presents a
value for Kh for PFOA that indicates a very low degree of partitioning from water to air, while
ATSDR (2018) presents a value that indicates a moderate to nearly high degree of partitioning
from water to air.
PFOA is a perfluorinated alkyl acid (PFAA) that exists as its carboxylate anion at typical
environmental pH values. Physical and chemical property data for various PFAS often
correspond to the protonated acid form of the compound in contrast to the deprotonated anion
(ITRC, 2020a). Thus, the available physical and chemical property data for PFOA may not be
representative of how PFOA partitions in the environment.
In cases where there are different conclusions in the literature, information describing
differences are presented to highlight the uncertainty in this area.
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Exhibit 4-1: Chemical Structure of PFOA
FFFFFFF 0
I I I I | | | <
FFFFFFF 0H
Source: USEPA, 2019a
Exhibit 4-2: Physical and Chemical Properties of PFOA
Property
Data
Chemical Abstracts Service (CAS)
Registry Number
335-67-1 (ChemlDPIus, 2019)
EPA Pesticide Chemical Code
Not Applicable
Chemical Formula
CsHF-isCh (ChemlDPIus, 2019)
Molecular Weight
414.09 g/mol (HSDB, 2016)
Color/Physical State
White to off-white powder (HSDB, 2016)
Boiling Point
192 deg C (HSDB, 2016)
Melting Point
54.3 deg C (HSDB, 2016)
Density
1.792 g/mL at 20 deg C (HSDB, 2016)
Freundlich Adsorption Coefficient
-
Vapor Pressure
0.0316 mm Hg at 19 deg C (HSDB, 2016)
0.017 mm Hg at 20 deg C (ATSDR, 2018; extrapolated)
Henry's Law Constant (Kh)
0.0908 atm-m3/mol at 25 deg C (est) (HSDB, 2016)
0.362 Pa-m3/mol (ATSDR, 2018; converts to 3.57E-06 atm-m3/mol)
log Kow
4.81 (est) (dimensionless) (HSDB, 2016)
Not applicable (ATSDR, 2018)
Koc
631 ±7.9 L/kg (mean ±1 standard deviation of selected values from
Zareitalabad et al., 2013; converted from log Koc to Koc)
pKa
1.30, 2.80, -0.5-4.2 (HSDB, 2016)
3.8 (ATSDR, 2018)
Solubility in Water
2,290 mg/L at 24 deg C (est); 3,300 mg/L at 25 deg C; 4,340 at 24.1 deg C
(HSDB, 2016)
9,500 mg/L at 25 deg C (ATSDR, 2018)
Other Solvents
-
Conversion Factors
(at 25 deg C, 1 atm)
-
Note:indicates that no information was found.
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4.2 Sources and Environmental Fate
4.2.1 Production, Use, and Release
Production data for PFOA are available from EPA's Inventory Update Reporting (IUR)
and Chemical Data Reporting (CDR) programs, described below.
No industrial release data are available from EPA's Toxics Release Inventory (TRI). (The
list of chemicals for which TRI reporting is required has never included PFOA (USEPA,
2016a).)
Inventory Update Reporting (IUR) / Chemical Data Reporting (CDR) Program
Under the authority of the Toxic Substances Control Act (TSCA), EPA gathers
information on production (including both manufacture and importation) of industrial chemicals.
Under the IUR, producers provided information once every four years from 1986 to 2006. Since
2012, producers have continued to provide information in accordance with the CDR Rule that
superseded the IUR in 2011. Under CDR, producers collect annual production data and report it
once every four years. Production of PFOA is subject to CDR reporting.
Until 2006, the IUR regulation required manufacturers and importers of organic chemical
substances included on the TSCA Chemical Substance Inventory to report site and
manufacturing information for chemicals produced (i.e., manufactured or imported) in amounts
of 10,000 pounds or more at a single site. In 2006, the minimum threshold for reporting was
increased to 25,000 pounds and reporting began for inorganic chemicals (USEPA, 2008). Among
changes made under CDR, a two-tier system of reporting thresholds was implemented, with
25,000 pounds as the threshold for some contaminants and 2,500 pounds as the threshold for
others (USEPA, 2014; USEPA, 2018b). As a compound with a TSCA section 5(a)(2) SNUR,
PFOA is among those to which the 2,500 pound threshold applies. As a result of program
modifications, the results from 2006 and later might not be directly comparable to results from
earlier years. Under CDR, every four years manufacturers and importers are required to report
annual data from each of the previous four years, provided that the thresholds of 2,500 or 25,000
pounds are met during at least one of the four years (USEPA, 2018b).
For the historical IUR data, EPA assigned one of eight production volume ranges for
each chemical included in the inventory. The ranges used for the 2006 reports differ slightly
from those used in the 1986 through 2002 reports, as described in Chapter 2. Exhibit 4-3 presents
the publicly available information on production of PFOA in the United States from 1986 to
2006 as reported under IUR. Production did not exceed 500,000 pounds in any year with
reported data. No data were reported in 1990 (the minimum threshold for reporting chemicals
produced was 10,000 pounds or more at a single site).
Exhibit 4-4 presents the publicly available production data for PFOA in the United States
from 2011 to 2015 as reported under CDR. No quantitative data for PFOA production are
available from the CDR dataset. Absence of recent reporting may indicate that production
(including import) of PFOA has halted or has been below the CDR reporting thresholds.
Although PFOA are not produced domestically or imported by the companies participating in the
2010/2015 PFOA Stewardship Program, PFOA may still be produced domestically or imported
below the CDR reporting thresholds by companies not participating in the PFOA Stewardship
Program.
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Exhibit 4-3: IUR Reported Annual Manufacture and Importation of PFOA in the
United States, 1986-2006 (pounds)
Reporting Cycle
1986
1990
1994
1998
2002
2006
Range of
Production
Volume
10,000-
500,000
No Reports
10,000-
500,000
10,000-
500,000
10,000-
500,000
< 500,000
Source: USEPA, 2008
Exhibit 4-4: CDR Reported Annual Manufacture and Importation of PFOA in the
United States, 2011-2015 (pounds)
Chemical Inventory Update Re
porting Cycle
2011
2012
2013
2014
2015
Range of Production /
Importation Volume
Withheld
Withheld
Withheld
Withheld
Withheld
"Withheld" = results not publicly available due to confidential business information.
Source: USEPA, 2018b
4.2.2 Environmental Fate
As discussed in Chapter 2, the primary measures used by EPA to assess mobility include
(where available) the organic carbon partitioning coefficient (Koc), log Kow, Kh, water solubility,
and vapor pressure. For PFOA, the log of the acid dissociation constant (pKa) is also important.
Based on its vapor pressure, if PFOA is released to the atmosphere it will be present as a
vapor. PFOA can react in the atmosphere with photochemically produced hydroxyl radicals. The
half-life for the degradation in air of PFOA by photochemically produced hydroxyl radicals is
estimated to be 31 days, based on a structure estimation method (HSDB, 2016). (Note that
radical reactions typically proceed more rapidly than chemically or microbially mediated
degradation reactions in other environmental media such as water, soil and/or sediment.) PFOA
is not expected to undergo direct photolysis (HSDB, 2016).
Based on findings from laboratory studies, Zareitalabad et al. (2013) calculate an average
log Koc of 2.8 ±0.9, equivalent to a Koc of 631 ±7.9 L/kg, which suggests a propensity for PFOA
to be mobilized to groundwater and surface water rather than to bind to suspended solids or
sediments. The authors note that field studies indicate a greater propensity for PFOA to bind to
soil and sediment than the lab-derived Koc values would predict.
With a pKa ranging from -0.5 to 4.2 (HSDB, 2016), PFOA will exist almost entirely in its
anionic form in the environment, which contributes to mobilization in water (HSDB, 2016;
Lange et al., 2006). A Henry's law constant of 0.0908 atm-m3/mol suggests that PFOA may
volatilize from moist soil, although the ionic nature of the compound at typical environmental
pH may lessen its volatilization. A vapor pressure of 0.0316 mm Hg suggests that PFOA may not
volatilize from dry soil (HSDB, 2016).
PFOA is resistant to hydrolysis, photolysis, and biodegradation (HSDB, 2016; Lange et
al., 2006). Washington et al. (2010) found that PFOA had a modeled disappearance half-life of
1.0 years in sludge-applied soils near Decatur, Alabama. Washington et al. (2010) noted that this
disappearance half-life is the time over which PFOA concentration in the surface soil was
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diminished by half due to all environmental processes: those processes could potentially include
uptake into plants (c.f. Yoo et al., 2011), erosion, leaching, ingrowth from precursors, and
degradation. Washington et al. (2014) posits that among these possible processes, leaching was
likely a leading mode of loss. However, the chemical stability of PFOA is much longer than this
disappearance half-life. Additionally, labile PFAS precursors commonly present in sludge may
degrade in soil settings, leading to ingrowth of recalcitrant PFAS such as perfluorooctanesulfonic
acid (PFOS), PFOA and related compounds (Wang et al., 2009; Martin et al., 2010; Washington
et al., 2014; Washington et al., 2015).
Chapter 2 presents scales used by EPA to informally rank chemical contaminants' likely
mobility (understood as their tendency to partition to water rather than other media) and
persistence as "high," "moderate," or "low" based on physical and chemical properties (see
Exhibit 2-2 and Exhibit 2-3). For PFOA, a Kh of 0.0908 atm-m3/mol and a log Kow of 4.81
predict a low likelihood of partitioning to water. A Koc value of 631 ±7.9 L/kg and a second Kh
value of 3.57E-06 atm-m3/mol predict a moderate likelihood of partitioning to water. A water
solubility of 2,290 mg/L at 24 degrees C to 9,500 mg/L at 25 degrees C predicts a high
likelihood of partitioning to water. A resistance to essentially all forms of degradation other than
atmospheric processes predicts high persistence.
4.3 Health Effects
In 2016, EPA published health assessments (health effects support documents or HESDs)
for PFOA and PFOS based on the Agency's evaluation of the latest peer reviewed science. For
more specific details on the potential for adverse health effects and approaches used to identify
and evaluate information on hazard and dose-response, please see USEPA (2016b) and USEPA
(2016c).
Human epidemiology data report associations between PFOA exposure and high
cholesterol, increased liver enzymes, decreased vaccination response, thyroid disorders,
pregnancy-induced hypertension and preeclampsia, and cancer (testicular and kidney). The
associations for most epidemiology endpoints are mixed. Although mean serum values are
presented in the human studies, actual estimates of PFOA exposure (i.e., doses/duration) are not
currently available. Thus, the serum level at which the effects were first manifest and whether
the serum had achieved steady state at the point the effect occurred cannot be determined. It is
likely that some of the human exposures that contribute to serum PFOA values come from PFOA
derivatives or precursors that break down metabolically to PFOA. These compounds could
originate from PFOA in diet and materials used in the home, which creates potential for
confounding. In addition, most of the subjects of the epidemiology studies have many PFASs
and/or other contaminants in their blood. Although the study designs adjust for other potential
toxicants as confounding factors, their presence constitutes a level of uncertainty that is usually
absent in the animal studies. Taken together, the weight of evidence for human studies supports
the conclusion that PFOA exposure is a human health hazard. At this time, EPA concludes that
the human studies are adequate for use qualitatively in the identification hazard and are
supportive of the findings in laboratory animals.
For PFOA, oral animal studies of short-term, subchronic, and chronic duration are
available in multiple species including monkeys, rats and mice. These animal studies report
developmental effects (survival, body weight changes, reduced ossification, delays in eye
opening, altered puberty, and retarded mammary gland development), liver toxicity
(hypertrophy, necrosis, and effects on the metabolism and deposition of dietary lipids), kidney
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toxicity (increased weight), immune effects, and cancer (liver, testicular, and pancreatic)
(USEPA 2016c). Overall, the animal toxicity studies available for PFOA demonstrate that the
developing fetus is particularly sensitive to PFOA-induced toxicity. Human epidemiology data
report associations between PFOA exposure and high cholesterol, increased liver enzymes,
decreased vaccination response, thyroid disorders, pregnancy-induced hypertension and
preeclampsia, and cancer (testicular and kidney). Overall, the developmental toxicity studies in
animals available for PFOA demonstrate that the developing rodent fetus and newborn rodent are
sensitive to PFOA-induced toxicity.
PFOA is known to be transmitted to the fetus via the placenta and to the newborn, infant,
and child via breast milk (USEPA, 2016c; NTP, 2020). Under EPA's Guidelines for Carcinogen
Risk Assessment (USEPA, 2005), there is "suggestive evidence of carcinogenic potential" for
PFOA. Similarly, the International Agency for Research on Cancer (IARC) classifies PFOA as
"possibly carcinogenic to humans" (IARC, 2017; IARC, 2019a; IARC, 2019b).
EPA calculated several candidate reference doses (RfDs) for PFOA in the 2016 HESD
(USEPA, 2016b) and selected the RfD of 0.00002 mg/kg/day based on reduced ossification in
proximal phalanges and accelerated puberty in male pups following exposure during gestation
and lactation in a developmental toxicity study in mice (Lau et al., 2006) for the derivation of a
lifetime health advisory (HA). The RfD for PFOA was calculated by applying uncertainty factors
to account for interspecies variability (3), intraspecies differences (10), and use of a LOAEL (3).
The Health Effects Support Document (USEPA, 2016b) describes these uncertainties in Section
4. Additionally, uncertainties and limitations (i.e., human epidemiological data, immunological
and mammary gland endpoints, and exposure) are discussed in detail in Section 8 of the Health
Advisory (USEPA, 2016c) document. The lifetime HA of 0.07 |ig/L was calculated using the
0.00002 mg/kg/day RfD for developmental effects, a drinking water intake (DWI) to bodyweight
(BW) ratio for the 90th percentile consumers only estimate of combined direct and indirect
community water ingestion for lactating women (0.054 L/kg-day) and a calculated 20 percent
relative source contribution (RSC) (USEPA, 2016c). This RfD is protective of effects other than
those occurring during development such as kidney and immune effects. Because of the potential
for increased susceptibility during the time period of pregnancy and lactation observed in this
study, EPA used DWI and BW parameters for lactating women in the calculation of a lifetime
HA for this target population during this potential critical time period. EPA also calculated a
cancer slope factor (CSF) of 0.07 (mg/kg/day)"1 based on testicular tumors in rats. The resultant
HA using this CSF is greater than the lifetime HA based on noncancer effects, indicating that the
HA derived based on the developmental endpoint is protective for the cancer endpoint (USEPA,
2016b). The lifetime HA of 0.07 |ig/L is used as the Health Reference Level (HRL) for
Regulatory Determination 4.
The RfDs for both PFOA and PFOS are based on similar developmental effects and are
numerically identical. Thus, when both chemicals co-occur at the same time and location, EPA
recommended a conservative and health-protective approach of 0.07 |ig/L for the PFOA/PFOS
total combined concentration (USEPA, 2016c).
EPA has initiated a systematic literature review of peer-reviewed scientific literature for
PFOA and PFOS published since 2013 with the goal of identifying any new studies that may be
relevant to human health assessment. An annotated bibliography of identified studies as well as
the protocol used to identify the relevant publications can be found in Appendix D.
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4.4 Occurrence
This section presents data on the occurrence of PFOA in ambient water and drinking
water in the United States. As described in section 4.3, an HRL of 0.07 |ig/L was calculated for
PFOA based on non-carcinogenic effects. HRLs are risk-derived concentrations against which to
evaluate the occurrence data to determine if contaminants occur at levels of potential public
health concern. Occurrence data from various sources presented below are analyzed with respect
to the HRL and one-half the HRL. When possible, estimates of the population exposed at
concentrations above the HRL and one-half the HRL are presented. Also, when possible, studies
that are meant to be representative and studies that are targeted at known or suspected sites of
contamination are identified as such.
For analysis of combined PFOS and PFOA concentrations against their common HRL of
0.07 |ig/L from the third Unregulated Contaminant Monitoring Rule (UCMR 3) and other
occurrence data sources, and summaries of UCMR 3 results for PFAS published by non-EPA
researchers, including co-occurrence analyses involving PFOS and PFOA, see section 3.4.4 in
the chapter on PFOS (Chapter 3).
For additional background information about data sources used to evaluate occurrence,
please refer to Chapter 2.
4.4.1 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the ambient sources of most drinking water. Contaminant
occurrence in ambient water provides information on the potential for contaminants to adversely
affect drinking water supplies. Occurrence data for PFOA in ambient water are not available
from the United States Geological Survey (USGS) National Water-Quality Assessment
(NAWQA). However, EPA's legacy Storage and Retrieval Data System (STORET) data
available through the Water Quality Portal (WQP) include PFOA data. Occurrence data for
PFOA in ambient water are also available from several published studies summarized below.
Storage and Retrieval (STORET) Data / Water Quality Portal (WQP)
From its launch in 1999 until it was decommissioned in June 2018, EPA's STORET Data
Warehouse was collaboratively populated with raw biological, chemical, and physical data from
surface water and groundwater sampling by federal, state and local agencies, Native American
tribes, volunteer groups, academics, and others. Legacy STORET data are accessible through the
Water Quality Portal (WQP): https://www.waterqualitvdata.us/portal/.
STORET data are from monitoring locations in all 50 states as well as multiple territories
and jurisdictions of the United States. Most data are from ambient waters, but in some cases
finished drinking water data are included as well. STORET's data quality limitations include
variations in the extent of national coverage and data completeness from parameter to parameter.
Data may have been collected as part of targeted, rather than randomized, monitoring.
This section presents analyses of STORET data, downloaded from the WQP in December
2017 (WQP, 2017). EPA reviewed STORET groundwater data from wells and surface water data
from lakes, rivers/streams, and reservoirs (WQP, 2017). The results of the STORET analysis for
PFOA are presented in Exhibit 4-5 through Exhibit 4-7. A total of eight PFOA samples from five
sites were available for analysis. These PFOA samples were collected in 2007. Of the five sites
sampled, all (100 percent) reported detections of PFOA. Detected concentrations ranged from
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0.03 |ig/L to 1.2 |ig/L. The minimum detected concentration may be indicative of the reporting
levels used.
Exhibit 4-5: PFOA STORET Data - Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
Maximum
Groundwater
0.3
1
1.2
1.2
Surface Water
N/A
N/A
N/A
N/A
Total
0.3
1
1.2
1.2
Source: WQP, 2017
N/A = not applicable (no data in this category).
Exhibit 4-6: PFOA STORET Data - Summary of Samples and Sites
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Total
Number
of Sites
Sites with Detections
Number
Percent
Number
Percent
Groundwater
8
8
100.00%
5
5
100.00%
Surface Water
0
0
0.00%
0
0
0.00%
Total
8
8
100.00%
5
5
100.00%
Source: WQP, 2017
Exhibit 4-7: PFOA STORET Data - Summary of States
Source Water
Type
Total
Number of
States
States with
Detections
Number
Percent
Groundwater
1
1
100.00%
Surface Water
0
0
0.00%
Total
1
1
100.00%
Source: WQP, 2017
Additional Ambient Water Studies
PFOA was detected in a number of additional ambient water studies conducted in
different parts of the United States and Canada. Hansen et al. (2002) conducted testing in
Decatur, Alabama, for the presence of fluorochemicals along an approximately 80-mile reach of
the Tennessee River located near and downstream of a manufacturing facility for perfluorinated
compounds and the Decatur Wastewater Treatment Plant. The reporting level used for PFOA in
this study was 0.025 |ig/L. PFOA was detected in 18 (45 percent) of the 40 samples collected at
this site. Concentrations of PFOA ranged from <0.025 |ig/L to 0.598 |ig/L, with a median
concentration of 0.379 |ig/L (Hansen et al., 2002).
Boulanger et al. (2004) analyzed samples from four locations in Lake Erie and four
locations in Lake Ontario. The locations were selected to represent urban-influenced and remote
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locations, as well as the geographical limits of each lake. The limit of quantification used for
PFOA in this study was 0.013 |ig/L. Samples were collected and analyzed in duplicate from each
location (total of 16 samples). PFOA was detected in all of the samples (100 percent).
Concentrations of PFOA ranged from 0.015 |ig/L to 0.070 |ig/L, with a median concentration of
0.0395 |ig/L (Boulanger et al., 2004).
A study conducted in 2008 by EPA in conjunction with several state agencies provides
information about the occurrence of 13 perfluorinated compounds in surface water from an
approximately 2,000 km reach of the Mississippi River and major tributaries. This study
involved the collection of 173 ambient water samples from 88 locations in and in close proximity
to the upper Mississippi River basin and Missouri River basin. The limit of detection for PFOA
was 0.00002 |ig/L. PFOA was detected in 168 (97.1 percent) of the samples, with 73 percent
having PFOA concentrations at or above the Level of Quantitation of 0.001 |ig/L. The median
concentration of PFOA was 0.00207 |ig/L, the 90th percentile concentration was 0.0119 |ig/L,
and the maximum concentration was 0.125 |ig/L (Nakayama et al., 2010).
Konwick et al. (2008) measured concentrations of PFOA in a river and a pond near a land
application site of wastewater sludge in Georgia near the site of North America's largest carpet
manufacturing site, along with concentrations in a stream located away from the land application
site. Concentrations of PFOA in the stream near the land application site ranged from 0.253 |ig/L
to 1.15 |ig/L. The concentrations in the pond near the land application site were lower with a
range of 0.0499 to 0.299 |ig/L. Concentrations away from the land application site were lower at
0.0030 to 0.0031 |ig/L.
USGS (2011) measured PFOA concentrations at outfall locations of 11 wastewater
treatment plants in Maryland and Washington D.C. from June to August 2010. PFOA was
detected in all 11 samples; concentrations ranged from 0.0054 |ig/L to 0.076 |ig/L.
4.4.2 Occurrence in Drinking Water
Data sources reviewed by the Agency for information on contaminant occurrence in
drinking water included: EPA's first, second, and third Unregulated Contaminant Monitoring
Rules (UCMR 1, UCMR 2, UCMR 3); Rounds 1 and 2 of the Agency's Unregulated
Contaminant Monitoring (UCM) program that preceded the Unregulated Contaminant
Monitoring Rule (UCMR); EPA's Information Collection Rule; EPA's National Inorganics and
Radionuclides Survey (NIRS); and a range of others as discussed in Chapter 2. Among the
sources reviewed, the following had data and information on PFOA occurrence in drinking
water. These data and information are discussed in this section.
• EPA's Third Unregulated Contaminant Monitoring Rule (UCMR 3).
State drinking water monitoring programs.
USGS source water and drinking water studies.
Additional studies from the literature.
Note that there may be some overlap, as sources with different purposes and audiences
may have reported the same underlying data. UCMR 3 is a nationally representative data source.
Other data sources profiled in this section are considered "supplemental" sources.
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Primary Data Sources
EPA's Third Unregulated Contaminant Monitoring Rule (UCMR 3)
UCMR 3 monitoring, designed to provide nationally representative contaminant
occurrence data, was conducted from 2013 through 2015. UCMR 3 List 1 Assessment
Monitoring occurrence data are available for PFOA. For UCMR 3, all large and very large public
water systems or PWSs (serving between 10,001 and 100,000 people and serving more than
100,000 people, respectively), plus a statistically representative national sample of 800 small
PWSs (serving 10,000 people or fewer), were required to conduct Assessment Monitoring during
a 12-month period between January 2013 and December 2015.1 Surface water (and groundwater
under the direct influence of surface water (GWUDI)) sampling points were monitored four
times during the applicable year of monitoring, and groundwater sample points were monitored
twice during the applicable year of monitoring. See USEPA (2012) and USEPA (2019b) for
more information on the UCMR 3 study design and data analysis.
The design of UCMR 3 permits estimation of national occurrence by multiplying the total
number of systems (or population served) in the nation in a system size category by the percent
of systems expected to exceed a specified threshold. An extrapolation methodology is applied to
small systems because not all small systems were required to participate in the UCMR 3
Assessment Monitoring. Because all large and very large systems were required to participate in
the UCMR 3 Assessment Monitoring, national estimates of occurrence in these size categories
can be done using survey census figures rather than extrapolation. Total national occurrence is
estimated by summing the extrapolated figures for small systems and the census figures for the
large and very large systems.
Exhibit 4-8 through Exhibit 4-12 provide an overview of PFOA occurrence results from
the UCMR 3 Assessment Monitoring. Laboratories participating in UCMR 3 were required to
report values at or above minimum reporting levels (MRLs) defined by EPA. The MRLs are
established to ensure reliable and consistent results from the array of laboratories needed for a
national monitoring program and are set based on the capability of multiple commercial
laboratories prior to the beginning each UCMR round. The MRL used for PFOA in the UCMR 3
survey was 0.02 |ig/L (77 FR 26072; USEPA, 2012). Exhibit 4-8 shows a statistical summary of
PFOA concentrations by system size and source water type (including the minimum, median,
90th percentile, 99th percentile, and maximum). Exhibit 4-9 presents a sample-level summary of
the results. Exhibit 4-10 through Exhibit 4-12 show system-level results, including national
extrapolations, at three thresholds: detections, one-half the HRL, and the HRL. Detections are
evaluated on a "greater than or equal to" basis (> the MRL), while health-based thresholds are
evaluated in terms of exceedances (> one-half HRL, and > HRL).
As noted above, UCMR 3 monitoring was required at a nationally representative sample
of small systems and at all large and very large systems. (Note that small systems selected to
monitor under UCMR 3 may not be representative of small systems located near potential PFOA
sources.) As a reminder that the figures from large and very large systems represent a census of
systems in those categories, results in those categories are labelled "CENSUS" in Exhibit 4-10
through Exhibit 4-12. No extrapolation was necessary in these categories, as it was for the small
systems, to derive national estimates of occurrence in these exhibits. National estimates of
1 A total of 799 small systems submitted Assessment Monitoring results.
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Final Regulatory Determination 4 Support Document - Ch 4, PFOA
January 2021
occurrence are reported separately in each system size and source water category, and also in
aggregate.
A total of 36,972 finished water samples for PFOA were collected from 4,920 PWSs.
PFOA was measured > MRL in 1.03 percent of UCMR 3 samples. Reported PFOA
concentrations for these "positive" results (detections) ranged from 0.02 |ig/L (the MRL) to
0.349 |ig/L. Of 4,920 PWSs, 53 (1.1 percent of PWSs, serving 1.5 percent of the PWS-served
population) reported at least one detection greater than one-half the HRL (0.035 |ig/L) and 13
(0.3 percent of systems, serving 0.2 percent of the PWS-served population) reported at least one
detection greater than the HRL of 0.07 |ig/L. Extrapolating these findings suggests that an
estimated 88 PWSs serving 3.8 million people nationally would have at least one PFOA
detection greater than one-half the HRL and an estimated 48 PWSs serving 615,000 people
nationally would have at least one PFOA detection greater than the HRL.
See section 3.4.4 in the PFOS chapter (Chapter 3) for a presentation of UCMR 3
monitoring results for summed PFOS and PFOA concentrations, plus a summary of PFAS
analyses conducted by non-EPA researchers using UCMR 3 data, including co-occurrence
analyses.
Exhibit 4-8: PFOA Occurrence Data from UCMR 3 Assessment Monitoring -
Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (in |jg/L)
> MRL of 0.02 |jg/L
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Small Systems (serving < 10,000 people)
Groundwater
0.03
0.03
0.03
0.03
0.032
Surface Water
0.13
0.17
0.20
0.21
0.20605
All Small Systems
0.03
0.08
0.18
0.20
0.20605
Large Systems (serving 10,001 -100,000 people) — CENSUS
Groundwater
0.02
0.03
0.07
0.32
0.338
Surface Water
0.02
0.03
0.07
0.29
0.349
All Large Systems
0.02
0.03
0.07
0.29
0.349
Very Large Systems (serving > 100,000 people) — CENSUS
Groundwater
0.021
0.04
0.05
0.06
0.065
Surface Water
0.02
0.03
0.05
0.14
0.14
All Very Large Systems
0.02
0.03
0.05
0.14
0.14
All Systems
All Water Systems
0.02
0.03
0.07
0.29
0.349
Source: USEPA, 2017b
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Final Regulatory Determination 4 Support Document - Ch 4, PFOA
January 2021
Exhibit 4-9: PFOA National Occurrence Measures Based on UCMR 3 Assessment
Monitoring Data - Summary of Samples
Source Water Type
Total #
of
Samples
Samples with
Detections
> MRL (0.02 |jg/L)
Samples with
Detections
> 1/2 HRL (0.035 |jg/L)
Samples with
Detections
> HRL (0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Small Systems (serving < 10,000 people)
Groundwater
1,853
2
0.11%
0
0.00%
0
0.00%
Surface Water
1,421
2
0.14%
2
0.14%
2
0.14%
All Small Systems
3,274
4
0.12%
2
0.06%
2
0.06%
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
11,707
94
0.80%
32
0.27%
9
0.08%
Surface Water
14,860
198
1.33%
80
0.54%
19
0.13%
All Large Systems
26,567
292
1.10%
112
0.42%
28
0.11%
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
2,020
7
0.35%
4
0.20%
0
0.00%
Surface Water
5,111
76
1.49%
24
0.47%
2
0.04%
All Very Large Systems
7,131
83
1.16%
28
0.39%
2
0.03%
All Systems
All Water Systems
36,972
379
1.03%
142
0.38%
32
0.09%
Source: USEPA, 2017b
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Final Regulatory Determination 4 Support Document - Ch 4, PFOA
January 2021
Exhibit 4-10: PFOA National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data- Summary of
System and Population Served Data - Detections
Source Water Type
UCMR 3 Sample
Number With At Least
One Detection
> MRL (0.02 ng/L)
Percent With At Least
One Detection
> MRL (0.02 ng/L)
National Inventory1
National Estimate
of Number With At Least
One Detection2
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Groundwater
527
1,498,845
1
536
0.19%
0.04%
55,700
38,730,597
106
13,900
Surface Water
272
1,250,215
1
8,323
0.37%
0.67%
9,728
20,007,917
36
133,000
All Small Systems
799
2,749,060
2
8,859
0.25%
0.32%
65,428
58,738,514
141
147,000
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
1,453
37,141,418
32
925,684
2.20%
2.49%
1,470
37,540,614
32
926,000
Surface Water
2,260
69,619,878
62
2,043,795
2.74%
2.94%
2,310
70,791,005
62
2,040,000
All Large Systems
3,713
106,761,296
94
2,969,479
2.53%
2.78%
3,780
108,331,619
94
2,970,000
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
68
16,355,951
4
603,800
5.88%
3.69%
68
16,355,951
4
604,000
Surface Water
340
115,158,260
17
4,051,738
5.00%
3.52%
343
120,785,622
17
4,050,000
All Very Large Systems
408
131,514,211
21
4,655,538
5.15%
3.54%
411
137,141,573
21
4,660,000
All Systems
All Water Systems
4,920
241,024,567
117
7,633,876
2.38%
3.17%
69,619
304,211,706
256
7,770,000
Source: USEPA, 2017b
1 The small system national inventory numbers for systems and population served by systems were derived from a freeze of the December 2010 Safe Drinking Water
Information System / Federal Version (SDWIS/Fed) data. These counts are based on all community and non-transient non-community water systems that served 10,000
people or fewer. All large and very large systems were required to conduct UCMR 3 Assessment Monitoring; thus, the national inventory numbers for the large and very
large systems are based on the number of systems expected to complete UCMR 3 monitoring. SDWIS/Fed inventory data from 2010 were used for the UCMR 3
national extrapolations as these data were consistent with the UCMR 3 inventory data at the timeframe of the UCMR 3 sample design.
2 National estimates for the small systems are generated by multiplying the UCMR 3 national statistical sample findings of system/population percentages and national
system/population inventory numbers for PWSs. National estimates for the large and very large systems are based directly on the UCMR 3 results, since this was a
census. Due to rounding, some calculations may appear to be slightly off.
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Final Regulatory Determination 4 Support Document - Ch 4, PFOA
January 2021
Exhibit 4-11: PFOA National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data- Summary of
System and Population Served Data -- Detections > 1/2 HRL (0.035 |jg/L)
Source Water Type
UCMR 3 Sample
Number With At Least
One Detection
> 1/2 HRL (0.035 |jg/L)
Percent With At Least
One Detection
> 1/2 HRL (0.035 |jg/L)
National Inventory1
National Estimate of
Number With At Least
One Detection > 1/2 HRL2
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Groundwater
527
1,498,845
0
0
0.00%
0.00%
55,700
38,730,597
0
0
Surface Water
272
1,250,215
1
8,323
0.37%
0.67%
9,728
20,007,917
36
133,000
All Small Systems
799
2,749,060
1
8,323
0.13%
0.30%
65,428
58,738,514
36
133,000
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
1,453
37,141,418
15
490,728
1.03%
1.32%
1,470
37,540,614
15
491,000
Surface Water
2,260
69,619,878
27
861,436
1.19%
1.24%
2,310
70,791,005
27
860,000
All Large Systems
3,713
106,761,296
42
1,352,164
1.13%
1.27%
3,780
108,331,619
42
1,350,000
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
68
16,355,951
2
371,800
2.94%
2.27%
68
16,355,951
2
372,000
Surface Water
340
115,158,260
8
1,920,708
2.35%
1.67%
343
120,785,622
8
1,920,000
All Very Large Systems
408
131,514,211
10
2,292,508
2.45%
1.74%
411
137,141,573
10
2,290,000
All Systems
All Water Systems
4,920
241,024,567
53
3,652,995
1.08%
1.52%
69,619
304,211,706
88
3,780,000
Source: USEPA, 2017b
1 The small system national inventory numbers for systems and population served by systems were derived from a freeze of the December 2010 SDWIS/Fed data.
These counts are based on all community and non-transient non-community water systems that served 10,000 people or fewer. All large and very large systems were
required to conduct UCMR 3 Assessment Monitoring; thus, the national inventory numbers for the large and very large systems are based on the number of systems
expected to complete UCMR 3 monitoring. SDWIS/Fed inventory data from 2010 were used for the UCMR 3 national extrapolations as these data were consistent with
the UCMR 3 inventory data at the timeframe of the UCMR 3 sample design.
2 National estimates for the small systems are generated by multiplying the UCMR 3 national statistical sample findings of system/population percentages and national
system/population inventory numbers for PWSs. National estimates for the large and very large systems are based directly on the UCMR 3 results, since this was a
census. Due to rounding, some calculations may appear to be slightly off.
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Final Regulatory Determination 4 Support Document - Ch 4, PFOA
January 2021
Exhibit 4-12: PFOA National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data - Summary of
System and Population Served Data - Detections > HRL (0.07 |jg/L)
Source Water Type
UCMR 3 Sample
Number With At Least
One Detection
> HRL (0.07 |jg/L)
Percent With At Least
One Detection
> HRL (0.07 |jg/L)
National Inventory1
National Estimate of
Number With At Least One
Detection > HRL 2
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Groundwater
527
1,498,845
0
0
0.00%
0.00%
55,700
38,730,597
0
0
Surface Water
272
1,250,215
1
8,323
0.37%
0.67%
9,728
20,007,917
36
133,000
All Small Systems
799
2,749,060
1
8,323
0.13%
0.30%
65,428
58,738,514
36
133,000
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
1,453
37,141,418
2
39,348
0.14%
0.11%
1,470
37,540,614
2
39,300
Surface Water
2,260
69,619,878
9
241,809
0.40%
0.35%
2,310
70,791,005
9
242,000
All Large Systems
3,713
106,761,296
11
281,157
0.30%
0.26%
3,780
108,331,619
11
281,000
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
68
16,355,951
0
0
0.00%
0.00%
68
16,355,951
0
0
Surface Water
340
115,158,260
1
201,000
0.29%
0.17%
343
120,785,622
1
201,000
All Very Large Systems
408
131,514,211
1
201,000
0.25%
0.15%
411
137,141,573
1
201,000
All Systems
All Water Systems
4,920
241,024,567
13
490,480
0.26%
0.20%
69,619
304,211,706
48
615,000
Source: USEPA, 2017b
1 The small system national inventory numbers for systems and population served by systems were derived from a freeze of the December 2010 SDWIS/Fed data.
These counts are based on all community and non-transient non-community water systems that served 10,000 people or fewer. All large and very large systems were
required to conduct UCMR 3 Assessment Monitoring; thus, the national inventory numbers for the large and very large systems are based on the number of systems
expected to complete UCMR 3 monitoring. SDWIS/Fed inventory data from 2010 were used for the UCMR 3 national extrapolations as these data were consistent with
the UCMR 3 inventory data at the timeframe of the UCMR 3 sample design.
2 National estimates for the small systems are generated by multiplying the UCMR 3 national statistical sample findings of system/population percentages and national
system/population inventory numbers for PWSs. National estimates for the large and very large systems are based directly on the UCMR 3 results, since this was a
census. Due to rounding, some calculations may appear to be slightly off.
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Final Regulatory Determination 4 Support Document - Ch 4, PFOA
January 2021
Supplemental Data Sources
Primary State PFOA Monitoring Data, 2013-2020
Consistent with the Agency's commitment in the PFAS Action Plan to highlight key
information gathered by the Agency and our partners, the Agency has supplemented its UCMR
data with data collected by states who have made their data publicly available. Subsequent to the
preliminary Regulatory Determination 4 Federal Register Notice, based on comments and
information received on the proposed determination, the Agency collected additional data from
additional states. Also, EPA updated data, where applicable, for those states for which EPA had
previously gathered and presented state data in the preliminary Regulatory Determination 4
documents. Some drinking water occurrence data from public water systems for PFOA are
available online from several states, including Alabama, California, Colorado, Kentucky, Maine,
Massachusetts, Missouri, New Hampshire, New Jersey, Ohio, Pennsylvania, and Vermont. Very
limited PFOA data were also available from Georgia and North Dakota. EPA downloaded
publicly available monitoring data from state websites. Note that some states (e.g., Colorado,
Michigan, and New Hampshire) conducted multiple, unique sampling efforts over different time
periods. The available state data are varied in terms of quantity and coverage. Exhibit 4-13
provides a summary of the available state monitoring data including date range and a description
of coverage and representativeness (including whether monitoring was targeted or non-targeted).
Note that Arizona, Michigan, and Rhode Island reported data for summed PFOS and PFOA
concentrations. A description of those studies is also included in Exhibit 4-13.
Exhibit 4-13: Summary of Available Primary State Monitoring Data
State
(Reference)
Date
Range
Type of
Water
Tested
Reporting
Limit
(M9/L)
Notes on Coverage
Survey
Type
Alabama
(ADEM,
2020)
2020-
ongoing
Groundwater
and Surface
Water -
Finished
Water
Not
reported
The Alabama Department of Public Health
instructed water systems to carry out PFAS
monitoring at all public water systems
(PWSs) not previously sampled during
UCMR 3. EPA reviewed the data available
online through March 2020. Only results that
are above the method reporting limit are
posted online.
Non-
Targeted
Arizona
(ADEQ,
2018)
2018
Groundwater
and Surface
Water -
Finished
Water
Not
reported
The Arizona Department of Environmental
Quality (ADEQ) sampled PWSs throughout
the state that were potentially impacted by
PFAS contamination. Finished drinking
water samples were collected between
January and May 2018 from 68 PWSs (109
drinking water wells). Results are only
reported for the sum of PFOA and PFOS
concentrations.
Targeted
California
(CADDW,
2020)
2013-
ongoing
Groundwater
and Surface
Water - Raw
and Finished
Water
Not
reported
EPA reviewed the data available online
through June 2020. Data were available
from approximately 300 PWSs. No
discussion is provided on the website
regarding the representativeness of the
sampling effort. For this analysis, EPA
excluded results from sites whose status
was listed as monitoring well, agriculture/
irrigation well, destroyed, abandoned, or
wastewater. Note that within state reported
Targeted
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Final Regulatory Determination 4 Support Document - Ch 4, PFOA
January 2021
State
(Reference)
Date
Range
Type of
Water
Tested
Reporting
Limit
(M9/L)
Notes on Coverage
Survey
Type
data, there may be overlap with UCMR 3
results from 2013 - 2015.
Colorado
(CDPHE,
2018;
CDPHE,
2020)
2013-
2017
Surface
Water
(Finished
Water) and
Drinking
Water
Distribution
Samples
Not
reported
Data available from 28 "drinking water
distribution zones" (one or more per PWS) in
targeted sampling efforts at a known
contaminated aquifer region. Data were
collected by El Paso County Public Health,
local water districts and utilities, and the
Colorado Department of Public Health and
Environment (CDPHE). Results represent
data collected in a targeted region.
Targeted
2020
Groundwater
and Surface
Water - Raw
and Finished
Water
0.0016 -
0.0024
The Colorado Department of Public Health
and the Environment offered free testing to
public drinking water systems serving
communities, schools, and workplaces and
also to fire districts with wells.
Approximately 50% of PWSs in Colorado
participated in the 2020 PFAS sampling
project. Data included in this report were
collected in March through May of 2020.
Non-
Targeted
Georgia (GA
EPD, 2020)
2020
Surface
Water - Raw
and Finished
Water
0.02
EPA and the Georgia Environmental
Protection Division (GA EPD) conducted
joint sampling of the City of Summerville's
drinking water sources and finished drinking
water on January 23, 2020.
Targeted
Kentucky
(KYDEP,
2019)
2019
Groundwater
and Surface
Water -
Finished
Water
<=0.005
Sampling of finished drinking water data
between June and October 2019. Under this
sampling effort, data are available from 81
community public drinking water treatment
plants (WTPs), representing 74 PWSs.
Non-
Targeted
Maine
(Maine DEP,
2020)
2013-
2020
Drinking
Water
0.001 -
0.020
pg/L.
In March 2019, the Maine PFAS Task Force
was created to review the extent of PFAS
contamination in Maine. Drinking water
results collected from 2013 through 2020
have been collected at 60 locations
throughout the state. Data include results
from public and private sources. Note that
with state reported data, there may be
overlap with UCMR 3 results from 2013 -
2015.
Targeted
Massachuse
tts (MA EE A,
2020)
2016-
ongoing
Groundwater
and Surface
Water - Raw
and Finished
Water
Not
reported
EPA reviewed the data available online
through March 2020. Data were available
from 67 PWSs. No discussion is provided on
the website regarding the
representativeness of the sampling effort.
Targeted
Michigan
(Michigan
EGLE,
2020a;
Michigan,
EGLE,
2020b;
2018-
2019
(Phase I)
Groundwater
and Surface
Water - Raw
and Finished
Water
0.002
Data available from 1,122 public water
systems. Results are from the Michigan
Department of Environment, Great Lakes,
and Energy (EGLE) statewide sampling for
PFAS in drinking water. Results are only
reported for the sum of PFOA and PFOS
concentrations.
Non-
Targeted
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Final Regulatory Determination 4 Support Document - Ch 4, PFOA
January 2021
State
(Reference)
Date
Range
Type of
Water
Tested
Reporting
Limit
(M9/L)
Notes on Coverage
Survey
Type
Michigan,
EGLE,
2020c;
Michigan,
EGLE,
2020d)
2019
(Phase
II)
Groundwater
- Raw and
Finished
Water
Not
Reported
Data available from 690 PWSs, including
community, non-transient non-community,
transient, and tribal water systems, as well
as child care and medical facilities. Results
are from Phase II of the Michigan PFAS
Action Response Team (MPART) initiative.
Results are only reported for the sum of
PFOA and PFOS concentrations.
Non-
Targeted
2019
(Monthly)
Surface
Water - Raw
and Finished
Water
Not
Reported
Data available from 68 water systems.
Michigan EGLE collected monthly samples
from PWSs sampled during Phase I of the
Statewide PFAS Sampling Survey which
utilized surface water as a source. Results
are only reported for the sum of PFOA and
PFOS concentrations.
Non-
Targeted
2019-
2020
(Quarterl
y)
Groundwater
and Surface
Water - Raw
and Finished
Water
Not
Reported
Data available from 86 water systems.
Michigan EGLE collected quarterly samples
from PWSs sampled during Phase I which
had Total Tested PFAS levels > 0.010 |jg/L
but did not exceed 0.070 |jg/L PFOS+PFOA.
Results are only reported for the sum of
PFOA and PFOS concentrations.
Targeted
Missouri
(Missouri
DNR, 2018)
2016-
2017
Groundwater
and Surface
Water - Raw
and Finished
Water
Not
reported
The Missouri Department of Natural
Resources (Missouri DNR) conducted
targeted sampling of finished drinking water
data between September 2016 and
February 2017. Under this sampling effort,
30 water samples were collected from 15
PWSs.
Targeted
New
Hampshire
(NHDES,
2017;
NHDES,
2020)
2013-
2017
Groundwater
and Surface
Water -
Finished
Water
Not
reported
Data available from 295 PWSs providing
results, including PWSs near contaminated
sites. Results represent all PFOA water
quality data reported to the New Hampshire
Department of Environmental Services
(NHDES) through May 3, 2017. Note that
within state reported data, there may be
overlap with UCMR 3 results from 2013 -
2015.
Targeted
2019
Groundwater
and Surface
Water -
Finished
Water
0.002-
0.005
Data available from 785 PWSs providing
results. Results represent all PFOA water
quality data reported to NHDES for 2019.
Non-
Targeted
New Jersey
(NJDEP,
2020)
2019-
ongoing
Groundwater
and Surface
Water -
Finished
Water
Not
reported
Statewide sampling of finished drinking
water data were available from 2019 and
2020. EPA reviewed data available online
through July 2020. In total, 7,957 water
samples from 1,222 PWS were analyzed for
PFOA and PFOS.
Non-
Targeted
North
Dakota
(NDDEQ,
2019)
2018
Groundwater
and Surface
Water - Raw
and Finished
Water
Not
reported.
In October 2018, the North Dakota
Department of Health collected samples
from a variety of sites where PFAS would
potentially be present. Sampling included
raw and finished water from 7 drinking water
treatment plants that were chosen based on
either the population served or proximity to
an industrial site
Targeted
4-24
-------
EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 4, PFOA January 2021
State
(Reference)
Date
Range
Type of
Water
Tested
Reporting
Limit
(M9/L)
Notes on Coverage
Survey
Type
Ohio (Ohio
DOH, 2020)
Feb
2020-
Ongoing
Groundwater
and Surface
Water - Raw
and Finished
Water
0.005
The Ohio EPA has coordinated sampling of
raw and finished drinking water from PWSs
throughout the state. EPA reviewed the data
available online through August 2020.
During this timeframe, data were available
from 694 PWSs. (Sampling is ongoing and
by the end of 2020, all 1,500 PWSs
anticipated to be sampled.)
Non-
Targeted
Pennsylvani
a (PADEP,
2020)
2019-
ongoing
Groundwater
and Surface
Water -
Finished
Water
0.002
A PFAS Sampling Plan was developed to
test PWSs across the state. A total of 493
PWSs were identified for inclusion in the
study as being at the highest risk for PFAS
contamination. EPA reviewed data available
through September 2019 from 87 PWSs.
Sampling is expected to take a year to
complete.
Targeted
Rhode
Island (Rl
DOH, 2020)
2017-
2019
Groundwater
and Surface
Water -
Finished
Water
0.004
The Rhode Island Department of Health (Rl
DOH) sampled all major drinking water
supplies in the state, as well as water in
schools with their own well(s), between 2017
and 2019. Under this sampling effort, PFOA
and PFOS data were collected by 87 PWSs.
Results are only reported for the sum of
PFOA and PFOS concentrations.
Non-
Targeted
Vermont
(VTDEC,
2020)
2019-
ongoing
Groundwater
and Surface
Water -
Finished
Water
0.002
The newly adopted Vermont Water Supply
Rule requires all community and non-
transient non-community water systems to
sample for PFAS in 2020. EPA reviewed
data available online through June 2020
from nearly 600 PWSs.
Non-
Targeted
A summary of primary state monitoring data from public water systems for PFOA is
presented in Exhibit 4-14 through Exhibit 4-16. As noted above, some of the monitoring data
from each state are limited and may not be representative of occurrence in the state. Overall,
detected concentrations ranged from 0.000229 |ig/L (Maine) to 2.5 |ig/L (Ohio). Seven states
included in the analysis had at least one detection of PFOA greater than the HRL of 0.07 |ig/L.
Six states included in the analysis did not have any detections of PFOA greater than the HRL.
See section 3.4.4 in the PFOS chapter (Chapter 3) for a presentation of state monitoring
results for summed PFOS and PFOA concentrations, including the reported results from Arizona,
Michigan, and Rhode Island.
Exhibit 4-14: PFOA Primary State Drinking Water Occurrence Data - Summary of
Detected Concentrations
State
Source Water Type1
(Sample Type)
Concentration Value of Detections (|jg/L)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Alabama
(2020)
Groundwater (Finished)
0.0036
0.0047
0.01628
0.025028
0.026
Surface Water (Finished)
0.001
0.0073
0.0113
0.01373
0.014
Total2
0.001
0.0064
0.0122
0.02408
0.026
4-25
-------
EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 4, PFOA January 2021
State
Source Water Type1
(Sample Type)
Concentration Value of Detections (|jg/L)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
California
(2013 -2020)
Groundwater (Raw)
0.00046
0.0099
0.025
0.09952
0.15
Groundwater (Finished)
0.00098
0.0039
0.0131
0.0415
0.047
Groundwater (Not Provided)3
0.00098
0.0033
0.00812
0.010712
0.011
Surface Water (Raw)
0.00082
0.012
0.02852
0.18
0.27
Surface Water (Finished)
0.0009
0.006
0.0228
0.0504
0.071
Surface Water (Not Provided)3
0.0021
0.0062
0.026
0.0325
0.033
Not Provided4
ND
ND
ND
ND
ND
Total2
0.00046
0.0098
0.02658
0.13
0.27
Colorado
(2013 -2017)
Distribution (Finished)
0.0024
0.03
0.07
0.09
0.09
Surface Water (Finished)
ND
ND
ND
ND
ND
Total2
0.0024
0.03
0.07
0.09
0.09
Colorado
(2020)
Groundwater (Raw)
0.00081
0.0025
0.00683
0.0183
0.022
Groundwater (Finished)
0.00045
0.0016
0.00742
0.011
0.011
Surface water (Raw)
0.00086
0.0071
0.0197
0.0733
0.076
Surface water (Finished)
0.00047
0.00235
0.0044
0.006722
0.0068
Total2
0.00045
0.0022
0.00892
0.0372
0.076
Georgia
(2020)
Surface Water (Raw)
ND
ND
ND
ND
ND
Surface Water (Finished)
0.049
0.049
0.049
0.049
0.049
Surface Water (Not Provided)3
0.047
0.0475
0.0479
0.04799
0.048
Total2
0.047
0.048
0.0488
0.04898
0.049
Kentucky
(2019)
Groundwater (Finished)
0.0011
0.0043
0.0123
0.0221
0.0232
Surface Water (Finished)
0.0011
0.0015
0.0049
0.0055
0.0056
Total2
0.0011
0.0020
0.0051
0.0192
0.0232
Maine
(2013-2020)
Not Provided4 (Raw)
0.0003
0.0080
0.0855
0.3791
0.4580
Not Provided4 (Finished)
0.000229
0.00397
0.01488
0.050632
0.0556
Not Provided5
0.00206
0.00612
0.01058
0.010958
0.011
Total2
0.000229
0.00612
0.0782
0.3448
0.458
Massachusetts
(2016-2020)
Groundwater (Raw)
0.00149
0.00856
0.03154
0.049904
0.0548
Groundwater (Finished)
0.00154
0.00842
0.021
0.033680
0.035
Surface Water (Raw)
0.00248
0.017
0.1018
0.445700
0.63
Surface Water (Finished)
0.00200
0.016
0.04
0.055150
0.059
Not Provided4 (Raw)
ND
ND
ND
ND
ND
Not Provided4 (Finished)
ND
ND
ND
ND
ND
Total2
0.00149
0.01
0.04127
0.237270
0.63
Missouri
(2016-2017)
Not Provided4 (Raw)
0.00024
0.00043
0.00067
0.00068
0.00068
Not Provided4 (Finished)
0.00024
0.00031
0.00054
0.00066
0.00067
Total2
0.00024
0.00035
0.00066
0.00068
0.00068
New
Hampshire
(2013 -2017)
Groundwater (Finished)
0.0004
0.005
0.016
0.077
0.092
Surface Water (Finished)
0.002
0.003
0.007
0.011
0.012
Not Provided5
0.004
0.007
0.009
0.009
0.009
Total2
0.0004
0.004
0.016
0.074
0.092
New
Hampshire
(2019)
Groundwater (Finished)
0.00178
0.00581
0.01644
0.063906
0.153
Surface Water (Finished)
0.0014
0.0037
0.006134
0.0103687
0.0109
Not Provided4 (Finished)
0.00318
0.005235
0.006879
0.0072489
0.00729
Total2
0.0014
0.00543
0.016
0.05337
0.153
4-26
-------
EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 4, PFOA January 2021
State
Source Water Type1
(Sample Type)
Concentration Value of Detections (|jg/L)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
New Jersey
(2019-2020)
Groundwater (Finished)
0.00051
0.0064
0.017
0.04367
0.15
Surface Water (Finished)
0.0015
0.0082
0.0237
0.03053
0.0379
Not Provided4 (Finished)
0.29
0.525
0.694
0.7264
0.73
Total2
0.00051
0.0066
0.019
0.04215
0.73
North Dakota
(2018)
Not Provided4 (Raw)
0.0006
0.0008
0.0008
0.0008
0.0008
Not Provided4 (Finished)
0.0005
0.0008
0.0009
0.0009
0.0009
Total2
0.0005
0.0008
0.0009
0.0009
0.0009
Ohio
(2020)
Groundwater (Raw)
0.0052
0.00985
0.0774
2.0934
2.5
Groundwater (Finished)
0.0059
0.0097
0.013
0.02028
0.021
Surface Water (Raw)
0.005
0.0055
0.00646
0.006676
0.0067
Surface Water (Finished)
0.0054
0.00545
0.00634
0.006664
0.0067
Total2
0.005
0.0093
0.0196
1.4942
2.5
Pennsylvania
(2019)
Groundwater (Finished)
0.0018
0.00315
0.00687
0.017875
0.02
Surface Water (Finished)
0.0021
0.0041
0.00768
0.011549
0.012
Total2
0.0018
0.00335
0.00754
0.01768
0.02
Vermont
(2019-2020)
Groundwater (Finished)
0.002
0.00405
0.01278
0.036
0.037
Surface Water (Finished)
ND
ND
ND
ND
ND
Not Provided4 (Finished)
ND
ND
ND
ND
ND
Total2
0.002
0.00405
0.01278
0.036
0.037
ND = no detections in this category
1 Whenever possible, systems' source water type information was derived from a freeze of the December 2019
SDWIS/Fed data.
2 Total rows display the minimum, median, 90th percentile, 99th percentile, and maximum concentration values from
the entire state data set, regardless of water type or sample type.
3 The results were not identified in the state data set as having been collected from raw or finished water.
4 The results were not identified in the state data set as having been collected from groundwater or surface water.
5 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
Exhibit 4-15: PFOA Primary State Drinking Water Occurrence Data - Summary of
Samples
State
Source Water Type1
(Sample Type)
Total # of
Samples
All Detections
Detections > Vi HRL
(0.035 |jg/L)
Detections > HRL
(0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Alabama2
(2020)
Groundwater
(Finished)
-
7
-
0
-
0
-
Surface Water
(Finished)
-
10
-
0
-
0
-
Total
-
17
-
0
-
0
-
California
(2013-2020)
Groundwater
(Raw)
1,698
625
36.81%
27
1.59%
16
0.94%
Groundwater
(Finished)
468
111
23.72%
2
0.43%
0
0.00%
Groundwater
(Not Provided)3
27
5
18.52%
0
0.00%
0
0.00%
Surface Water
2,373
979
41.26%
71
2.99%
39
1.64%
4-27
-------
EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 4, PFOA January 2021
State
Source Water Type1
(Sample Type)
Total # of
Samples
All Detections
Detections > Vi HRL
(0.035 |jg/L)
Detections > HRL
(0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
(Raw)
Surface Water
(Finished)
429
121
28.21%
4
0.93%
1
0.23%
Surface Water
(Not Provided)3
88
51
57.95%
0
0.00%
0
0.00%
Not Provided4
2
0
0.00%
0
0.00%
0
0.00%
Total
5,085
1,892
37.21%
104
2.05%
56
1.10%
Colorado
(2013 -2017)
Distribution (Finished)
96
33
34.38%
15
15.63%
4
4.17%
Surface Water
(Finished)
11
0
0.00%
0
0.00%
0
0.00%
Total
107
33
30.84%
15
14.02%
4
3.74%
Colorado
(2020)
Groundwater
(Raw)
87
38
43.68%
0
0.00%
0
0.00%
Groundwater
(Finished)
345
67
19.42%
0
0.00%
0
0.00%
Surface water
(Raw)
43
28
65.12%
2
4.65%
1
2.33%
Surface water
(Finished)
238
40
16.81%
0
0.00%
0
0.00%
Total
713
173
24.26%
2
0.28%
1
0.14%
Georgia
(2020)
Surface Water
(Raw)
1
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Finished)
2
1
50.00%
1
50.00%
0
0.00%
Surface Water
(Not Provided)3
2
2
100.00%
2
100.00%
0
0.00%
Total
5
3
60.00%
3
60.00%
0
0.00%
Kentucky
(2019)
Groundwater
(Finished)
38
7
18.42%
0
0.00%
0
0.00%
Surface Water
(Finished)
43
17
39.53%
0
0.00%
0
0.00%
Total
81
24
29.63%
0
0.00%
0
0.00%
Maine
(2013-2020)
Not Provided5
(Raw)
237
135
56.96%
43
18.14%
18
7.59%
Not Provided5
(Finished)
86
19
22.09%
1
1.16%
0
0.00%
Not Provided4
21
7
33.33%
0
0.00%
0
0.00%
Total
344
161
46.80%
44
12.79%
18
5.23%
Massachusetts
(2016-2020)
Groundwater
(Raw)
195
125
64.10%
10
5.13%
0
0.00%
Groundwater
(Finished)
219
133
60.73%
0
0.00%
0
0.00%
Surface Water
(Raw)
124
98
79.03%
1
0.81%
19
15.32%
Surface Water
(Finished)
63
36
57.14%
12
19.05%
0
0.00%
Not Provided5
(Raw)
1
0
0.00%
0
0.00%
0
0.00%
Not Provided5
(Finished)
1
0
0.00%
0
0.00%
0
0.00%
Total
603
392
65.01%
56
9.29%
19
3.15%
Missouri
(2016-2017)
Not Provided5
(Raw)
26
8
30.77%
0
0.00%
0
0.00%
Not Provided5
(Finished)
29
9
31.03%
0
0.00%
0
0.00%
4-28
-------
EPA - OGWDW
Final Regulatory Determination 4 Support Document - Ch 4, PFOA
January 2021
State
Source Water Type1
(Sample Type)
Total # of
Samples
All Detections
Detections > Vi HRL
(0.035 |jg/L)
Detections > HRL
(0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Total
55
17
30.91%
0
0.00%
0
0.00%
New
Hampshire
(2013 -2017)
Groundwater
(Finished)
472
240
50.85%
7
1.48%
3
0.64%
Surface Water
(Finished)
107
19
17.76%
0
0.00%
0
0.00%
Not Provided5
(Finished)
6
2
33.33%
0
0.00%
0
0.00%
Total
585
261
44.62%
7
1.20%
3
0.51%
New
Hampshire
(2019)
Groundwater
(Finished)
866
247
28.52%
5
0.58%
3
0.35%
Surface Water
(Finished)
74
22
29.73%
0
0.00%
0
0.00%
Not Provided5
(Finished)
5
2
40.00%
0
0.00%
0
0.00%
Total
945
271
28.68%
5
0.53%
3
0.32%
New Jersey
(2019-2020)
Groundwater
(Finished)
7,028
2,834
40.32%
47
0.67%
9
0.13%
Surface Water
(Finished)
966
648
67.08%
2
0.21%
0
0.00%
Not Provided5
(Finished)
12
4
33.33%
4
33.33%
4
33.33%
Total
8,006
3,486
43.54%
53
0.66%
13
0.16%
North Dakota
(2018)
Not Provided5
(Raw)
7
5
71.43%
0
0.00%
0
0.00%
Not Provided5
(Finished)
7
5
71.43%
0
0.00%
0
0.00%
Total
14
10
71.43%
0
0.00%
0
0.00%
Ohio
(2020)
Groundwater
(Raw)
587
20
3.41%
3
0.51%
2
0.34%
Groundwater
(Finished)
719
19
2.64%
0
0.00%
0
0.00%
Surface Water
(Raw)
38
5
13.16%
0
0.00%
0
0.00%
Surface Water
(Finished)
40
4
10.00%
0
0.00%
0
0.00%
Total
1,384
48
3.47%
3
0.22%
2
0.14%
Pennsylvania
(2019)
Groundwater
(Finished)
76
18
23.68%
0
0.00%
0
0.00%
Surface Water
(Finished)
20
12
60.00%
0
0.00%
0
0.00%
Total
96
30
31.25%
0
0.00%
0
0.00%
Vermont
(2019-2020)
Groundwater
(Finished)
634
64
10.09%
2
0.32%
0
0.00%
Surface Water
(Finished)
55
0
0.00%
0
0.00%
0
0.00%
Not Provided5
(Finished)
6
0
0.00%
0
0.00%
0
0.00%
Total
695
64
9.21%
2
0.29%
0
0.00%
1 Whenever possible, systems' source water type information was derived from a freeze of the December 2019
SDWIS/Fed data.
2 Only data for detections were available from Alabama.
3 The results were not identified in the state data set as having been collected from raw or finished water.
4 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
5 The results were not identified in the state data set as having been collected from groundwater or surface water.
4-29
-------
EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 4, PFOA January 2021
Exhibit 4-16: PFOA Primary State Drinking Water Occurrence Data - Summary of
Systems
State
Source Water Type1
(Sample Type)
Total # of
Systems/
Sites
Systems/Sites with
Detections
Systems/Sites with
Detections > Vi HRL
(0.035 |jg/L)
Systems/Sites with
Detections > HRL
(0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Alabama2
(2020)
Groundwater
(Finished)
-
5
-
0
-
0
-
Surface Water
(Finished)
-
8
-
0
-
0
-
Total
-
13
-
0
-
0
-
California
(2013 -2020)
Groundwater
(Raw)
166
69
41.57%
7
4.22%
3
1.81%
Groundwater
(Finished)
35
11
31.43%
2
5.71%
0
0.00%
Groundwater
(Not Provided)8
9
2
22.22%
0
0.00%
0
0.00%
Surface Water
(Raw)
125
57
45.60%
4
3.20%
1
0.80%
Surface Water
(Finished)
57
12
21.05%
1
1.75%
1
1.75%
Surface Water
(Not Provided)8
17
8
47.06%
0
0.00%
0
0.00%
Not Provided9
1
0
0.00%
0
0.00%
0
0.00%
Total
301
126
41.86%
11
3.65%
4
1.33%
Colorado3
(2013-2017)
Distribution (Finished)
23
12
52.17%
6
26.09%
1
4.35%
Surface Water
(Finished)
5
0
0.00%
0
0.00%
0
0.00%
Total
28
12
42.86%
6
21.43%
1
3.57%
Colorado
(2020)
Groundwater
(Raw)
24
11
45.83%
0
0.00%
0
0.00%
Groundwater
(Finished)
225
50
22.22%
0
0.00%
0
0.00%
Surface water
(Raw)
9
7
77.78%
1
11.11%
1
11.11%
Surface water
(Finished)
172
32
18.60%
0
0.00%
0
0.00%
Total
400
88
22.00%
1
0.25%
1
0.25%
Georgia
(2020)
Surface Water
(Raw)
1
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Finished)
1
1
100.00%
1
100.00%
0
0.00%
Surface Water
(Not Provided)8
1
1
100.00%
1
100.00%
0
0.00%
Total
1
1
100.00%
1
100.00%
0
0.00%
Kentucky4
(2019)
Groundwater
(Finished)
38
7
18.42%
0
0.00%
0
0.00%
Surface Water
(Finished)
43
17
39.53%
0
0.00%
0
0.00%
Total
81
24
29.63%
0
0.00%
0
0.00%
Maine5
(2013-2020)
Not Provided10
(Raw)
37
25
67.57%
8
21.62%
4
10.81%
Not Provided10
(Finished)
23
7
30.43%
1
4.35%
0
0.00%
Not Provided9
9
6
66.67%
0
0.00%
0
0.00%
Total
60
31
51.67%
8
13.33%
4
6.67%
Groundwater
24
15
62.50%
2
8.33%
0
0.00%
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State
Source Water Type1
(Sample Type)
Total # of
Systems/
Sites
Systems/Sites with
Detections
Systems/Sites with
Detections > Vi HRL
(0.035 |jg/L)
Systems/Sites with
Detections > HRL
(0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Massachusetts
(2016-2020)
(Raw)
Groundwater
(Finished)
46
27
58.70%
0
0.00%
0
0.00%
Surface Water
(Raw)
9
8
88.89%
1
11.11%
1
11.11%
Surface Water
(Finished)
12
9
75.00%
1
8.33%
0
0.00%
Not Provided10
(Raw)
1
0
0.00%
0
0.00%
0
0.00%
Not Provided10
(Finished)
1
0
0.00%
0
0.00%
0
0.00%
Total
67
40
59.70%
3
4.48%
1
1.49%
Missouri6
(2016-2017)
Not Provided10
(Raw)
14
6
42.86%
0
0.00%
0
0.00%
Not Provided10
(Finished)
15
7
46.67%
0
0.00%
0
0.00%
Total
15
8
53.33%
0
0.00%
0
0.00%
New
Hampshire
(2013-2017)
Groundwater
(Finished)8
266
97
36.47%
5
1.88%
3
1.13%
Surface Water
(Finished)8
24
9
37.50%
0
0.00%
0
0.00%
Not Provided10
(Finished)
6
2
33.33%
0
0.00%
0
0.00%
Total
296
108
36.49%
5
1.69%
3
1.01%
New
Hampshire
(2019)
Groundwater
(Finished)8
743
217
29.21%
5
0.67%
3
0.40%
Surface Water
(Finished)8
37
10
27.03%
0
0.00%
0
0.00%
Not Provided10
(Finished)
5
2
40.00%
0
0.00%
0
0.00%
Total
785
229
29.17%
5
0.64%
3
0.38%
New Jersey
(2019 -2020)
Groundwater
(Finished)
1,120
531
47.41%
13
1.16%
3
0.27%
Surface Water
(Finished)
98
75
76.53%
2
2.04%
0
0.00%
Not Provided10
(Finished)
4
1
25.00%
1
25.00%
1
25.00%
Total
1,222
607
49.67%
16
1.31%
4
0.33%
North Dakota7
(2018)
Not Provided10
(Raw)
7
5
71.43%
0
0.00%
0
0.00%
Not Provided10
(Finished)
7
5
71.43%
0
0.00%
0
0.00%
Total
7
5
71.43%
0
0.00%
0
0.00%
Ohio
(2020)
Groundwater
(Raw)
545
19
3.49%
3
0.55%
2
0.37%
Groundwater
(Finished)
663
18
2.71%
0
0.00%
0
0.00%
Surface Water
(Raw)
30
5
16.67%
0
0.00%
0
0.00%
Surface Water
(Finished)
30
4
13.33%
0
0.00%
0
0.00%
Total
694
30
4.32%
3
0.43%
2
0.29%
Pennsylvania
(2019)
Groundwater
(Finished)
72
16
22.22%
0
0.00%
0
0.00%
Surface Water
15
8
53.33%
0
0.00%
0
0.00%
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State
Source Water Type1
(Sample Type)
Total # of
Systems/
Sites
Systems/Sites with
Detections
Systems/Sites with
Detections > Vi HRL
(0.035 |jg/L)
Systems/Sites with
Detections > HRL
(0.07 |jg/L)
Number
Percent
Number
Percent
Number
Percent
(Finished)
Total
87
24
27.59%
0
0.00%
0
0.00%
Groundwater
(Finished)
547
46
8.41%
1
0.18%
0
0.00%
Vermont
(2019-2020)
Surface Water
(Finished)
43
0
0.00%
0
0.00%
0
0.00%
Not Provided10
(Finished)
2
0
0.00%
0
0.00%
0
0.00%
Total
592
46
7.77%
1
0.17%
0
0.00%
1 Whenever possible, systems' source water type information was derived from a freeze of the December 2019
SDWIS/Fed data.
2 Only data for detections were available from Alabama.
3 For the Colorado distribution system samples collected between 2013 and 2017, "systems" were counted as unique
zones in which the sample was distributed.
4 For Kentucky, "systems" were counted as unique location names as PWSIDs from SDWIS/Fed could not always be
linked with the location names.
5 For Maine, "systems" were counted as unique site names as PWSIDs from SDWIS/Fed could not always be linked
with the site names.
6 For Missouri, "systems" were counted as unique facility numbers in which the sample was collected.
7 For North Dakota, "systems" were counted as unique sites in which the sample was collected.
8 The results were not identified in the state data set as having been collected from raw or finished water.
9 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water
10 The results were not identified in the state data set as having been collected from groundwater or surface water.
In addition to the monitoring data available from public water systems, North Carolina
has made data from 17 private wells available associated with the Chemours facility in
Fayetteville (NCDEQ, 2018). The maximum PFOA concentration was 0.0124 |ig/L, while the
median was 0.004 |ig/L. PFOA concentrations did not exceed the EPA HRL (0.07 |ig/L) at any
of the sampling sites. Note that EPA does not regulate private drinking water wells but may
evaluate data from private wells where the data may be indicative of contaminants in aquifers
that are used as sources for public water system wells.
Due to the multitude of requests for public records for PFAS analytical results, the
Alaska Department of Environmental Conservation (Alaska DEC) has made PFAS drinking
water sample results available online from private wells and public water systems (Alaska DEC,
2020). In samples collected from February 2014 through July 2020, a total of six communities
are listed as having drinking water sample results above EPA's Health Advisory Level. Twenty-
three communities are identified as having all drinking water sample results below the EPA
Health Advisory Level.
Additional Secondary Source Water and Drinking Water Studies
The discussion presented in this section represent secondary analyses summarized from
published studies and/or publicly available presentations that did not contain downloadable
occurrence data for evaluation purposes. For selected states that had publicly available
occurrence data for evaluation, please see Exhibit 4-13 through Exhibit 4-16 above.
The Division of Water Supply of the New Jersey Department of Environmental
Protection (NJDEP) collected 29 water samples (22 raw water and 7 finished water) from 23
water systems in 2006. Sites selected included those near facilities where PFOA may have been
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used, handled, stored and/or manufactured, as well as facilities where previously collected data
indicated the presence of a large number of tentatively identified compounds. PFOA was
detected in 18 of the 22 raw water samples, with the detected concentrations ranging from
<0.004 |ig/L to 0.027 |ig/L. PFOA was detected in six of the seven finished water samples, with
the detected concentrations ranging from <0.004 |ig/L to 0.039 |ig/L. Note that there were four
detected concentrations (two in raw water and two in finished water) that were detected but not
quantified below the low calibration standard of 0.004 |ig/L (NJDEP, 2007). Additional
sampling was conducted in 2007 and 2008 at 18 NJ systems (12 of the original systems sampled
plus 6 new systems). Five of the 18 systems had at least one detection of PFOA greater than or
equal to 0.04 |ig/L. The highest concentration observed was 0.14 |ig/L (Post et al., 2009).
Additional sampling conducted by the NJDEP occurred between July 2009 and February
2010. A total of 33 raw water samples were collected from 31 PWSs in 20 of the 21 counties in
New Jersey. The main objective of sample site selection was to select sites throughout all of New
Jersey that serve as sources of drinking water. Therefore, at least one sampling location was
selected in each of 21 counties except Hudson County, as all water served to residents in that
county is purchased from sources outside the county (NJDEP, 2014). Since the objective of this
study was to determine the occurrence of PFAS in drinking water sources throughout New
Jersey, this study included only untreated water samples, in contrast to the 2006 study (described
above), which included samples from both raw (untreated) and treated water sources. PFOA was
detected in 18 (55 percent) of the 33 samples. Reported PFOA concentrations ranged from 0.006
|ig/L to 0.100 |ig/L (NJDEP, 2014).
In 2018, the Iowa Air National Guard (Iowa ANG) completed site investigations of bases
located at the Sioux City and Des Moines airports (Iowa DNR, 2020). Detections of PFAS
compounds were identified at both locations. At Sioux City, the Site Investigation Report
suggested that private wells might be impacted by off-site migration of PFAS contamination.
The Iowa Department of Natural Resources (Iowa DNR) required sampling of raw water by the
Iowa ANG from selected private wells and a public well prior to the next phase of work
(Remedial Investigation). This work was completed in 2019 and the results of this testing
indicated the raw water for all wells tested were either below detection or below the drinking
water health advisory (Iowa DNR, 2020).
In Minnesota, sampling was conducted in 2004-2005 at selected municipal, non-
community, and private drinking water wells in the vicinity of perfluorinated compound waste
sites (Goeden and Kelly, 2006). In this targeted sampling study, PFOA was detected in six (16.2
percent) of the 37 municipal wells sampled; the maximum detected concentration was 0.9 |ig/L.
PFOA was detected in one (3.8 percent) of the 26 private wells sampled; the detected
concentration was 0.67 |ig/L. PFOA was not detected in any of the 22 non-community wells
sampled. The aggregate results of this study showed that seven (8.9 percent) of the 85 wells
sampled had PFOA detections, with a maximum concentration of 0.9 |ig/L.
As a supplement to the data provided in Goeden and Kelly (2006), ATSDR has published
some additional details/updates regarding PFOA occurrence in six Oakdale, Minnesota,
municipal wells (ATSDR, 2008). These wells are a subset of the wells in the Goeden and Kelly
(2006) targeted sampling study, discussed above. PFOA has been detected consistently in four of
the six (66.7 percent) municipal wells reported by ATSDR. Detected concentrations ranged from
0.2 |ig/L to 1.02 |ig/L. ATSDR (2008) reports that "in September 2007, the Minnesota
Department of Health (MDH) Public Health Laboratory issued new formal reporting levels for
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the seven perfluorinated compounds of 0.3 micrograms per liter (|ig/L)." Presumably the
reported detections lower than 0.3 |ig/L were collected before that time.
In 2018, Kelly and Peterson (2018) presented the results of the sampling of perfluorinated
compounds in Minnesota in the East Metro area. This sampling began with drinking water
investigations near the 3M Cottage Grove plant and related legacy waste disposal sites in
Washington County (east of St. Paul) (MDH, 2019). The East Metro investigations have
identified an area of groundwater contamination covering over 150 square miles, affecting the
drinking water supplies of over 140,000 Minnesotans. Since 2003, about 2,500 private wells
have been sampled and more than 800 drinking water advisories have been issued (Kelly and
Peterson, 2018). Frequent and intensive monitoring was conducted at private wells near known
sources of contamination while less frequent monitoring was conducted at private wells with low
and stable PFAS concentrations.
The Minnesota Department of Health (MDH) is working with partner agencies to identify
and respond to PFAS contamination in Minnesota as needed. Ongoing efforts are described on
their website (MDH, 2020) and are summarized below.
• In the East Metro of the Twin Cities, PFAS concentrations in most city wells have
remained stable or decreased slightly over time. MDH reports that there are currently five
community public water supplies in the East Metro that have individual wells above the
MDH health-based guidance values: Oakdale, Lake Elmo, Woodbury, Cottage Grove,
and St. Paul Park. Over 3,000 private wells have also been sampled in the East Metro
area.
• Bemidji's community public water supply wells are above the updated MDH health-
based guidance values. Since 2009, the Minnesota Pollution Control Agency (MPCA)
and MDH have sampled 25 residential and other wells to the east, northeast, and
southeast of the airport. MDH reported that on one occasion trace level detections of
perfluorobutanoic acid (PFBA) were found in four of the wells, far below the Health Risk
Limit. Otherwise, PFAS have not been detected in the wells.
• In 2010-2011, the Air National Guard sampled 12 residential wells to the north,
northwest, and northeast of the Duluth Air National Guard Base. PFAS were detected in
three wells, at concentrations below the drinking water values in effect at that time. In
2016, when MDH lowered the guidance values for PFOS and PFOA, the state began
sampling wells around the airbase, including to the south. MDH (2020) reported that 57
wells have been sampled. Trace levels of PFAS have been detected in 22 wells, mainly
PFBA and perfluoropentanoic acid (PFPeA) at concentrations similar to shallow
groundwater samples statewide.
The Nebraska Department of Environmental Quality (NDEQ) formed a team to track
issue with the PFAS compounds. Initial sampling conducted at 25 PWSs between 2013 - 2015
by the Nebraska Department of Health and Human Services (Nebraska DHHS) Drinking Water
Program identified zero detections of PFAS. A statewide PFAS inventory was completed by
NDEQ in 2017 that identified 990 sites that potentially used or produced PFAS compounds
(NDEQ, 2020). Based on the inventory, NDEQ conducted initial PFAS sampling of nearby
private wells. NDEQ reported that while levels of concern have not been detected, they are early
in the investigation (NDEQ, 2020).
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In 2018, the New York State Department of Health (NYSDOH) published a summary
presentation (Wilson, 2018) that described the occurrence of PFOA and PFOS throughout the
state. Data from three sources were summarized: (1) UCMR 3; (2) follow-up sampling in PWSs
and private wells near known and potential sources of contamination; and (3) a source water
assessment sampling program.
The presentation indicated that 10 percent of the PWSs had PFOA and PFOS
concentrations at or above 0.030 |ig/L and 15 percent of PWSs had concentrations at or above
0.020 |ig/L. Approximately 20 percent of PWSs reported concentrations at or above 0.010 |ig/L.
It was noted that the majority of the New York State (NYS) PWS occurrence data was targeted
sampling. Furthermore, although the sample size of the study was large, it represented only a
small percentage of the PWSs throughout NYS. A summary of the NYS occurrence data is
presented in Exhibit 4-17 below.
Exhibit 4-17: Summary of New York State PFOA-PFOS Sampling Results
PFOA + PFOS Levels
Follow-Up Sampling near
Known/Suspected
Contamination: PWS
Occurrence
Source Water
Assessment
Sampling: PWS
Occurrence
Overall NYS
Occurrence
Data
Non-detect (< 0.002 pg/L)
45%
58%
50% (129)
0.002 to < 0.020 |jg/L
35%
36%
35% (91)
0.020 to < 0.070 |jg/L
12%
5%
9% (24)
Greater than 0.070 |jg/L (EPA
Health Advisory)
8%
1%
5% (13)
Source: Wilson, 2018
The presentation concluded that the NYS follow-up sampling and source water
assessment sampling findings were comparable to national occurrence findings from UCMR 3.
The lower reporting limit yielded more detections. (The detection limit in NYS sampling was
0.002 |ig/L for both PFOA and PFOS, while the minimum reporting level in UCMR 3 was 0.020
|ig/L for PFOA and 0.040 |ig/L for PFOS.) The presentation notes that reporting thresholds of
0.010 |ig/L and 0.030 |ig/L yield significantly different findings.
In 2018, the Vermont Department of Environmental Conservation (VT DEC) published a
report titled "Perfluoroalkyl Substances (PFAS) Contamination Status Report" that summarized
the findings of an investigation of PFAS contamination at and around a known contaminated site
in the Bennington area (VT DEC, 2018). Results were described for 10 different types of
sampling sites, including wire coating facilities, semi-conductor facilities, groundwater at
landfills, surface water, sediment and fish, public drinking water supply testing, wastewater
treatment facilities, and more. VT DEC tested over 600 private drinking water wells in
Bennington and the two municipal water systems for Bennington and North Bennington. The VT
DEC has also posted the results of 2016 PFAS sampling from private wells in the Bennington
area in PDF format.
Between January 2002 and May 2005, testing of the municipal water system of Little
Hocking, Ohio, for PFOA was conducted with a detection limit of 0.01 |ig/L. As of 2006, the
highest levels of PFOA reported in public water supplies in the United States were in the Little
Hocking water system, which had been in operation since 1968, drawing water from wells across
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the Ohio river from the facility (Emmett et al., 2006).The average concentration of PFOA in the
water distribution system ranged from 1.5 to 7.2 |ig/L, with a mean value of 3.55 |ig/L (Emmett
et al., 2006). (Based on data compiled for this report, it appears that no other PWS in the U.S.
has had a documented PFOA concentration as high as the levels detected in Little Hocking.)
Private wells in the area have exhibited concentrations of PFOA that ranged from <0.01 |ig/L to
14 |ig/L.
Quinones and Snyder (2009) reported monitoring results of perfluoroalkyl compounds,
including PFOA, from drinking water treatment facility samples collected across the United
States in 2008, and from associated surface, ground, and wastewater sources. Raw water and
finished water sampling was conducted at seven drinking water utilities across the United States.
These included two utilities in California, plus a single utility in each of the following five states:
Colorado, Arizona, Nevada, Minnesota, and Georgia. Raw waters at these facilities included
sources regarded as having no impact from treated wastewater. The method reporting limit for
PFOA was 0.005 |ig/L. Concentrations of PFOA were all below reporting limits at every surface
water site sampled. Wastewater treatment plant effluents and other highly impacted waters had
almost 100 percent detection frequency; PFOA averaged the highest overall concentration at any
site at 0.115 |ig/L.
Seven drinking water utilities with low, moderate, or high degrees of wastewater impact
exhibited varying concentrations and frequencies of detection of PFOA in their influents (raw
water) and effluents (finished water). Quinones and Snyder (2009) considered approximate
wastewater contributions above 50 percent to be "high" wastewater impacts at sites and facilities,
30-50 percent to be "medium," and 5 percent and less to be "low." (Note that the study did not
assign a category to the range of 5-30 percent.) Monitoring results include:
• Two utilities with low wastewater impact exhibited average detected concentrations
of PFOA that ranged from <0.005 |ig/L - 0.011 |ig/L with frequencies of detection
that ranged from 0 percent to 100 percent in influents, and average detected
concentrations of PFOA that ranged from <0.005 |ig/L - 0.011 |ig/L with frequencies
of detection that ranged from 0 percent to 100 percent in effluents.
• Three utilities with medium wastewater impact exhibited average detected
concentrations of PFOA that ranged from 0.0056 |ig/L - 0.031 |ig/L with frequencies
of detection that ranged from 3.3 percent to 100 percent in influents, and average
detected concentrations of PFOA that ranged from <0.005 |ig/L - 0.030 |ig/L with
frequencies of detection that ranged from 0 percent to 100 percent in effluents.
• Two utilities with high wastewater impact exhibited average detected concentrations
of PFOA that ranged from 0.015 |ig/L - 0.025 |ig/L with frequencies of detection of
100 percent in both influents, and average detected concentrations of PFOA that
ranged from <0.005 |ig/L - 0.018 |ig/L with frequencies of detection that ranged from
0 percent to 100 percent in effluents.
EPA / United States Geological Survey (USGS') Nationwide Reconnaissance of Contaminants
of Emerging Concern
As part of a joint study by EPA and USGS to assess human exposure to contaminants of
emerging concern, water samples were collected from 25 drinking water treatment plants in 24
states (Glassmeyer et al., 2017). Participation in the study was voluntary. Final sample locations
were chosen to represent a wide range of geography, diversity in disinfectant type used, and a
range of production volumes. Phase I of the study (2007) analyzed a subset of contaminants and
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sites to test experimental design; PFOA was not included in Phase 1. During Phase II of the
study (2010-2012), samples were collected from groundwater and surface water sources as well
as treated drinking water from 25 drinking water treatment plants and analyzed for PFOA
occurrence. The Lowest Concentration Minimum Reporting Level (LCMRL) was 0.00056 (J,g/L.
Results from Phase II are presented in Exhibit 4-18. Of the 25 source water samples, 76
percent exceeded the LCMRL. Similarly, 76 percent of treated water samples exceeded the
LCMRL. The maximum detected concentration in source water was 0.112 [j,g/L which is greater
than the HRL. The maximum detected concentration in treated water was 0.104 [j,g/L which is
also greater than the HRL.
Exhibit 4-18: Drinking Water Treatment Plants - Summary of PFOA Samples
(Glassmeyer et al., 2017)
Source Water Type
Number of
Samples
All Detections
Median
Concentration
(ng/L)
Maximum
Concentration
(ng/L)
Number
Percent
Source Water
25
19
76%
0.00632
0.112
Treated Drinking Water
25
19
76%
0.00415
0.104
Source: Glassmeyer et al., 2017
A second published study by the same research team (Boone et al., 2019) compared the
team's findings at 24 of the participating PWSs in 2010-2012 with UCMR results from the same
PWSs in 2013-2015. Detection frequencies were higher in the Boone et al. (2019) study than
under UCMR 3, which is not surprising given the difference in reporting levels. With an
LCMRL of 0.00056 (J,g/L, Boone et al. (2019) found quantifiable levels of PFOA at 18 (75
percent) of the 24 systems. (This information is in the supplemental tables that accompany the
study.) Under UCMR 3, with an MRL of 0.02 |ig/L, detections were reported in only one (4
percent) of the 24 systems. Although concentrations observed in the Boone et al. (2019) study
tended to be lower than concentrations observed under UCMR 3, the single system with
detections under both studies had higher concentrations under UCMR 3 monitoring than under
Boone et al. (2019) monitoring. Only one PFOA concentration observed by Boone et al. (2019),
0.104 |ig/L, exceeds the HRL.
4.4.3 Other Data
The Centers for Disease Control and Prevention (CDC) Fourth National Report on Human
Exposure to Environmental Chemicals and Updated Tables, 1999-2000 and 2003-2016
Since 1999, the National Health and Nutrition Examination Survey (NHANES) has
examined the U.S. population annually and released the data in 2-year cycles. The survey is
based on a representative sample of the U.S. population based on age, gender, and race/ethnicity
(CDC, 2019). Published studies of NHANES data indicate that in early cycles PFOA was
detected in over 99 percent of samples (Kato et al., 2011). The Fourth National Report on
Human Exposure to Environmental Chemicals was published in 2009 (CDC, 2009). The
exposure data tables have been updated several times since the original publication, most
recently in 2019 (CDC, 2019). The 2019 updated tables include the PFOA exposure data
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originally reported in the 2009 report as well as all of the subsequent updates. Exhibit 4-21
presents the 95th percentile values of PFOA analyzed in serum from years 1999 through 2016.
Overall, the concentrations in serum decreased over time. Please note that these 95th percentile
values cannot be directly compared to the HRL since the values represent human serum
concentrations, not drinking water concentrations. PFOA in human tissue can have its origin in
exposure via drinking water, food, or other routes.
Exhibit 4-19: 95th Percentiles of Serum PFOA Concentrations,
1999-2000 and 2003-2016
Year Range
Medium
Analyzed
95th
Percentile of
All Samples
(M9/L)
95%
Confidence
Interval (|jg/L)
Sample Size
1999-2000
Serum
11.9
10.9-13.5
1,562
2003-2004
Serum
9.80
7.40-14.1
2,094
2005-2006
Serum
11.3
8.80-14.5
2,120
2007-2008
Serum
9.60
8.90-10.1
2,100
2009-2010
Serum
7.50
6.20-9.70
2,233
2011-2012
Serum
5.68
5.02-6.49
1,904
2013-2014
Serum
5.57
4.60-6.27
2,165
2015-2016
Serum
4.17
3.87-4.67
1,993
Source: CDC, 2019
The limit of detection (LOD) for 1999-2000, 2005-2006, 2007-2008, 2009-2010, and
2011-2012 is 0.1 |jg/L; for 2003-2004 it is 0.2 pg/L. Starting in 2013-2014, CDC
measured linear/straight-chain PFOA and branched isomers of PFOA separately. The
results are reported both separately and as a sum, the latter of which is intended to be
comparable to data from earlier years. The sums are reported in this table. LODs are not
established for summed data.
4.5 Analytical Methods
EPA has published three analytical methods that are available for the analysis of PFOA
and other PFAS in drinking water:
• EPAMethod 537, Version 1.1, Determination of Selected Perfluorinated Alkyl Acids
in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tcindem
Mass Spectrometry (LC/MS/MS). The LCMRL generated by the laboratory that
developed the method is 5.1 ng/L. Mean recoveries in fortified reagent water,
chlorinated groundwater, and high-total organic carbon (TOC) chlorinated surface
water range from 104 to 110%, with Relative Standard Deviations (RSDs) of 2.2 to
6.5% (USEPA, 2009).
• EPA Method 537.1, Version 1.0, Determination of Selected Per- and Polyfluorinated
Alkyl Substances in Drinking Water by Solid Phase Extraction and Liquid
Chromatography/Tandem Mass Spectrometry (LC/MS/MS). The LCMRL generated
by the laboratory that developed the method is 0.82 ng/L. Mean recoveries in fortified
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reagent water, tap water (from groundwater and surface water sources), and private
well water range from 91.1 to 106%, with RSDs of 1.5 to 5.2% (USEPA, 2018c).
• EPA Method 533, Determination of Per- and Polyfluoroalkyl Substances in Drinking
Water by Isotope Dilution Anion Exchange Solid Phase Extraction and Liquid
Chromatography / Tandem Mass Spectrometry (USEPA, 2019c).
Laboratories participating in UCMR 3 were required to use EPA Method 537 and, as
described in Section 4.4.2, were required to report PFOA values at or above the EPA-defined
MRL of 0.02 |.ig/L (77 FR 26072; USEPA, 2012). The MRL was set based on the capability of
multiple laboratories at the time.
4.6 Treatment Technologies
EPA evaluates whether suitable treatment technologies are available prior to
promulgating a final National Primary Drinking Water Regulation (NPDWR).
EPA's Drinking Water Treatability Database (USEPA, 2020c) summarizes available
technical literature on the efficacy of treatment technologies for a range of priority drinking
water contaminants. According to the Database, the following processes are considered effective
for the removal of PFOA: granular activated carbon, or GAC (up to > 99 percent removal),
membrane separation with high pressure membranes such as nanofiltration and reverse osmosis
(up to > 99 percent removal), anion exchange (up to 99 percent removal), and powdered
activated carbon (up to 95 percent removal). The exact percentage removal a water system may
achieve with a given technology will be dependent upon a variety of factors, including source
water quality and water system characteristics. GAC and anion exchange are non-steady state
technologies where the adsorbent media will need to be periodically replaced or
reactivated/regenerated to prevent contaminant breakthrough.
Both GAC and anion exchange are more effective at removing long-chain PFAS than
short-chain PFAS (Dickenson and Higgins, 2016; Ross et al., 2018). GAC systems appear to
have a faster breakthrough for perfluoroalkyl carboxylates (such as PFOA) than for
perfluoroalkyl sulfonates (such as PFOS) of equivalent chain lengths (Ross et al., 2018). Anion
exchange resins, similarly, have been shown to have a greater affinity for perfluoroalkyl
sulfonates than for perfluoroalkyl carboxylates (Dickenson and Higgins, 2016). Thus, when
mixed PFAS are in the source water, short-chain perfluoroalkyl carboxylates are likely to break
through before other PFAS. Competition with natural organic matter can interfere with the
effectiveness of GAC for the removal of PFAS compounds (Ross et al., 2018; Dickenson and
Higgins, 2016).
Crone et al. (2019) and Speth et al. (2019) analyzed the advantages and disadvantages of
some of the more promising treatment technologies for the removal of PFAS substances. For
PFAS removal, GAC is one of the most commonly reported and evaluated treatment technology
in the literature. The treatment efficacy of GAC is strongly dependent upon the type of PFAS
present and physio-chemical properties of the solution matrix. The use of GAC for the removal
of PFAS will also remove other co-contaminants and help maintain disinfectant residuals and
control disinfection byproducts by removing disinfection byproduct precursors (Crone et al.,
2019; Speth et al., 2019). However, certain poorly adsorbed PFAS will break through the
adsorber quickly, and it is important to consider reactivation/removal frequency and the cost of
disposal or reactivation of spent carbon, and the potential for overshoot (i.e., higher
concentrations of a contaminant in the effluent than the influent, due to preferential adsorption of
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other contaminants) if a GAC system is poorly designed or operated (Crone et al., 2019; Speth et
al., 2019).
Anion exchange resins have a high capacity for some PFAS, they can remove select co-
contaminants, and they require smaller beds than GAC. Additionally, they can pair well with
other technologies for removing a broad range of PFAS that may not be readily removed with a
single treatment technology (Crone et al., 2019). However, like GAC they may have short run
times for select PFAS and be subject to competitive adsorption. They may also have resin
disposal issues, and like GAC they may have a potential for overshoot if poorly designed or
operated (Speth et al., 2019).
High pressure membranes like reverse osmosis and nanofiltration are effective for
removing a wide range of PFAS, will remove other co-contaminants, and will help maintain
disinfection residuals by removing disinfection byproduct precursors. However, they have high
capital and operations costs (Crone et al., 2019; Speth et al., 2019). Additionally, membrane
fouling, corrosion control, and the disposal or treatment of concentrate stream are issues that
need to be addressed (Crone et al., 2019; Speth et al., 2019).
According to EPA's Drinking Water Treatability Database, the following are not
considered effective for the removal of PFOA: conventional treatment (comprised of the unit
processes coagulation, flocculation, clarification, and filtration), and ultraviolet (UV) at
wavelengths below the 185-220 nm range. Conventional ozonation was also ineffective, but a
demonstration study of a patented ozofractionation process, which used ozone gas to separate
PFOA into a foam residual, found greater than 97 percent removal (USEPA, 2020c).
UV/hydrogen peroxide treatment was less effective in comparison to UV alone after 24 hours of
irradiation (USEPA, 2020c). Other treatment processes with varying results include UV
irradiation at wavelengths in the 185-220 nm range and/or at long irradiation times of up to 72
hours (USEPA, 2020c). UV bench scale studies at 220-460 nm wavelength with irradiation times
of 72 hours showed 89.5 percent removal (Hori et al., 2004). Low-pressure membrane filtration,
such as microfiltration or ultrafiltration, varied in effectiveness (USEPA, 2020c). Some of the
percent removal values reported in the Database (e.g., for UV and low-pressure membrane
filtration) are higher than reasonably anticipated due to a variety of factors such as study
conditions differing from the conditions of typical drinking water facilities, outlier datapoints, or
multiple treatment processes being run simultaneously (USEPA, 2020c).
For more information about treatment technologies discussed here, see the Health
Advisory for PFOA (USEPA, 2016c) and the Drinking Water Treatability Database (USEPA,
2020c).
4.7 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2008. Public Health Assessment
for Perfluorochemical Contamination in Lake Elmo and Oakdale, Washington County,
Minnesota, EPA facility ID: MND 980704738, MND 980609515. Agency for Toxic
Substances and Disease Registry, Public Health Service, United States Department of
Health and Human Services, Atlanta, Georgia. May. Available on the Internet at:
https://www.atsdr.cdc.gov/HAC/pha/PFCsLakeElmo/PFCs in Lake Elmo PHA 8-29-
2008 508.pdf.
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ATSDR. 2018. Toxicological Profile for Perfluoroalkyls. Draft for Public Comment. Agency for
Toxic Substances and Disease Registry, Public Health Service, United States Department
of Health and Human Services, Atlanta, GA. Available on the Internet at:
http://www.atsdr.cdc.gov/ToxProfiles/tp200.pdf
Alabama Department of Environmental Management (ADEM). 2020. Per- and Polyfluoroalkyl
Substances (PFAS) in Drinking Water. Quarter 1: January 1, 2020 - March 31, 2020
PFAS Detections.
Alaska Department of Environmental Conservation (Alaska DEC). 2020. Division of Spill
Prevention and Response. Per- and Polyfluoroalkyl Substances (PFAS). Drinking Water
Sample Results. Available on the Internet at: https://dec.alaska.gov/spar/csp/pfas/sample-
results/#above.
Arizona Department of Environmental Quality (ADEQ). 2018. Arizona's Public Water System
Screening for Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS)
Final Report. Available on the Internet at:
http://static.azdeq.gov/wqd/reports/pfoapfosepareport final.pdf.
Boone, J.S., C. Vigo, T. Boone, C. Byrne, J. Ferrario, R. Benson, J. Donohue, J.E. Simmons,
D.W. Kolpin, E.T. Furlong, and S.T. Glassmeyer. 2019. Per- and polyfluoroalkyl
substances in source and treated drinking waters of the United States. Science of The
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Boulanger, B., J. Vargo, J.L. Schnoor, and K.C. Hornbuckle. 2004. Detection of perfluorooctane
surfactants in Great Lakes water. Environmental Science and Technology 38(15):4064-
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Kannan, S.A. Mabury and S.P.J, van Leeuwen. 2011. Perfluoroalkyl and polyfluoroalkyl
substances in the environment: Terminology, classification, and origins. Society of
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Accessed July 2020.
Centers for Disease Control and Prevention (CDC). 2009. Fourth National Report on Human
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Disease Control and Prevention. Available on the Internet at:
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9-508.pdf.
ChemlDPlus. 2019. Profile for Perfluorooctanoic acid. Available on the Internet at:
http://chem.sis.nlm.nih.gov/chemidplus/. Accessed March 18, 2019.
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Colorado Department of Public Health and Environment (CDPHE). 2018. Perfluorinated
compound levels in environmental water samples. Updated August 7, 2018. Available on
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ults DRAFT/Download?%3AshowAppBanner=false&%3Adisplav count=n&%3Ashow
VizHome=n&%3Aorigin=viz share link&%3AisGuestRedirectFromVizportal=v&%3A
embed=v.
Crone, B.C., T.F. Speth, D.G. Wahman, S.J. Smith, G. Abulikemu, E.J. Kleiner, and J.G.
Pressman. 2019. Occurrence of per- and polyfluoroalkyl substances (PFAS) in source
water and their treatment in drinking water. Critical Reviews in Environmental Science and
Technology 49(24):2359-2396.
Dickenson, E.R.V., and C. Higgins. 2016. Treatment Mitigation Strategies for Poly- and
Perfluoroalkyl Substances. Web Report #4322. Water Research Foundation. Denver, CO.
Emmett, E.A., F.S. Shofer, H. Zhang, D. Freeman, C. Desai, and L.M. Shaw. 2006. Community
exposure to perfluorooctanoate: Relationships between serum concentrations and
exposure sources. Journal of Occupational and Environmental Medicine 48(8):759-770.
Georgia Environmental Protection Division (GA EPD). 2020. EPA Sampling Report for
Summerville. Available on the Internet at: https://epd.georgia.gov/pfoa-and-pfos-
information.
Glassmeyer, S.T., E.T. Furlong, D.W. Kolpin, A.L. Batt, R. Benson, J. S. Boone, O. Conerly,
M.J. Donohue, D.N. King, M.S. Kostich, H.E. Mash, S.L. Pfaller, K.M. Schenck, J.E.
Simmons, E.A. Varughese, S.J. Vesper, E.N. Villegas, and V.S. Wilson. 2017.
Nationwide Reconnaissance of Contaminants of Emerging Concern in Source and
Treated Drinking Waters of the United States. Science of the Total Environment (581-
582):909-922.
Goeden, H. and J. Kelly. 2006. Targeted Sampling 2004-2005. Perfluorochemicals in Minnesota,
MN DOH, 2/27/06.
Hansen, K.J., H.O. Johnson, J.S. Elridge, J.L. Butenhoff, and L.A. Dick. 2002. Quantitative
characterization of trace levels of PFOS and PFOA in the Tennessee River.
Environmental Science and Technology 36(8): 1681-1685.
Hansen, K.J., H.O. Johnson, J.S. Elridge, J.L. Butenhoff, and L.A. Dick. 2002. Quantitative
characterization of trace levels of PFOS and PFOA in the Tennessee River.
Environmental Science and Technology 36(8): 1681-1685.
Hazardous Substances Data Bank (HSDB). 2016. Profile for Perfluorooctanoic acid. Available
on the Internet at: http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen7HSDB. Last revision
date October 25, 2016.
Hori, H., E. Hayakawa, H. Einaga, S. Kutsuna, K. Koike, T. Ibusuki, H. Kiatagawa, and R.
Arakawa. 2004. Decomposition of environmentally persistent perfluorooctanoic acid in
water by photochemical approaches, Env. Sci & Tech. 38:6118-6124
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Iowa Department of Natural Resources (Iowa DNR). 2020. PFAS Action Plan. Available on the
Internet at: https://www.iowadnr.gov/Environmental-Protection/PFAS.
International Agency for Research on Cancer (IARC). 2017. "Perfluorooctanoic acid." In: Some
Chemicals Used as Solvents and in Polymer Manufacture IARC Monographs on the
Evaluation of Carcinogenic Risks to Humans, Volume 110. Available on the Internet at:
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Internet at: http://monographs.iarc.fr/ENG/Classification/index.php. Last updated
December 12, 2019.
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on the Internet at: https://monographs.iarc.fr/wp-content/uploads/2019/07/Preamble-
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Interstate Technology & Regulatory Council (ITRC). 2020a. Naming Conventions and Physical
and Chemical Properties of Per- and Polyfluoroalkyl Substances (PFAS). Available on
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1.itrcweb.org/fact sheets page/PFAS Fact Sheet Naming Conventions April2020.pdf.
ITRC. 2020b. References for Naming Conventions and Physical and Chemical Properties of Per-
and Polyfluoroalkyl Substances (PFAS). Available on the Internet at: https://pfas-
1 .itrcweb.org/references/. Last updated September 2020.
Kato, K., L.Y. Wong, L.T. Jia, Z. Kuklenvik, and A.M. Calafat. 2011. Trends in exposure to
polyfluoroalkyl chemicals in the U.S. Population: 1999-2008. Environmental Science and
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Kelly, J. and K. Peterson. 2018. Perfluorochemicals (PFCs) in the East Metro. Minnesota
Department of Health (MDH). Available on the Internet at:
https://3msettlement.state.mn.us/sites/default/files/PFCs%20in%20the%20East%20Metro
.pdf.
Kentucky Department for Environmental Protection (KYDEP). 2019. Evaluation of Kentucky
Community Drinking Water for Per- & Poly-Fluoroalkyl Substances. Available on the
Internet at:
https://eec.ky. gov/Documents%20for%20URLs/PFAS%20Drinking%20Water%20Repor
t%20Final.pdf.
Konwick B.J., G.T. Tomy, N. Ismail, J.T. Peterson, R.J. Fauver, D. Higginbotham, and A.T.
Fisk. 2008. Concentrations and patterns of perfluoroalkyl acids in Georgia, USA surface
waters near and distant to a major use source. Environmental Science and Technology
27(10):2011-2018.
Lange, F.T., C. Schmidt, and H.J. Brauch. 2006. Perfluoroalkyl carboxylates and sulfonates,
Rhine Water Works, The Netherlands, Association of River Waterworks - RIWA.
Lau, C., J.R. Thibodeaux, R.G. Hanson, M.G. Narotsky, J.M. Rogers, A.B. Lindstrom, and M.J.
Strynar. 2006. Effects of perfluorooctanoic acid exposure during pregnancy in the
mouse. ToxicolSci. 90(2):510-518.
Maine Department of Environmental Protection (Maine DEP). 2020. Maine PFAS Data (2007 -
2020). Available on the Internet at: https://www.maine.gov/dep/spills/topics/pfas/PFAS-
current-results-06022020.pdf.
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Martin, J.W., B.J. Asher, S. Beesoon, J.P. Benskin, and M.S. Ross. 2010. PFOS or PreFOS? Are
perfluorooctane sulfonate precursors (PreFOS) important determinants of human and
environmental perfluorooctane sulfonate (PFOS) exposure? J. Environ. Monit.
12(11): 1979-2004.
Massachusetts Department of Energy and Environmental Affairs (MA EEA). 2020. Energy and
Environmental Affairs Data Portal. Available on the Internet at:
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Michigan Department of Environment, Great Lakes and Energy (Michigan EGLE). 2020a.
Michigan PFAS Action Response Team: Phase I (2018). Available on the Internet at:
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Michigan EGLE. 2020b. Michigan PFAS Action Response Team: Phase II (2019). Available on
the Internet at: https://www.michigan.gOv/pfasresponse/0.9038,7-365-
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Michigan EGLE. 2020c. Michigan PFAS Action Response Team: Monthly Surface Water System
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Michigan EGLE. 2020d. Michigan PFAS Action Response Team: Quarterly Monitoring.
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Speth, T. 2019. Treatment for Contaminants of Emerging Concern (CECs): Per- and
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Water by Solid Phase Extraction and Liquid Chromatography/Tandem Mass
Spectrometry (LC/MS/MS). Version 1.1. National Exposure Research Laboratory, Office
of Research and Development. EPA 600-R-08-092. Available on the Internet at:
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Substances; Significant New Use Rule. Federal Register Vol 80. No. 13, p. 2885,
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USEPA. 2017b. Third Unregulated Contaminant Monitoring Rule Dataset. Available on the
Internet at: https://www.epa.gov/dwucmr/occurrence-data-unregulated-contaminant-
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at: https://www.epa.gov/assessing-and-managing-chemicals-under-tsca/fact-sheet-
20102015-pfoa-stewardship-program. Last updated August 9, 2018.
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https://www.epa.gov/chemical-data-reporting/how-report-under-chemical-data-reporting.
Accessed December 2018.
U SEP A. 2018c. Method 53 7.1. Determination of Selected Per- and Polyfluorinated Alkyl
Substances in Drinking Water by Solid Phase Extraction and Liquid
Chromatography/Tandem Mass Spectrometry (LC/MS/MS). Version 1.0. National
Exposure Research Laboratory, Office of Research and Development. EPA/600/R-
18/352. Available on the Internet at:
https://cfpub.epa.gov/si/si public record report.cfm?dirEntryId=343042&Lab=NERL&s
impleSearch=0&showCriteria=2&searchAll=Determination+of+Selected+Per-
+and+Polvfluorinated+Alkyl+Substances+&TIMSTvpe=&dateBeginPublishedPresented
=11 %2F 02%2F2016
USEPA. 2019a. CompTox Chemicals Dashboard, Searched by DSSTox Substance Id =
DTXSID8031865. Available on the Internet at:
https://comptox.epa.gov/dashboard/dsstoxdb/results?search=DTXSID8031865.
USEPA. 2019b. Occurrence Data from the Third Unregulated Contaminant Monitoring Rule
(UCMR 3). EPA 815-R-19-007.
USEPA. 2019c. EPA Method 533, Determination of Per- and Polyfluoroalkyl Substances in
Drinking Water by Isotope Dilution Anion Exchange Solid Phase Extraction and Liquid
Chromatography / Tandem Mass Spectrometry. December.
USEPA. 2020a. Significant New Use Rule: Long-Chain PerfluoroalkyI Carboxylate and
Perfluoroalkyl Sulfonate Chemical Substances. Office of Pollution Prevention and
Toxics. EPA-HQ-OPPT-2013-0225. Available on the Internet at:
https://beta.regulations.gov/document/EPA-HO-OPPT-2013-0225-Q232.
USEPA. 2020b. Risk Management for Per- and Polyfluoroalkyl Substances (PFAS) under
TSCA. Available on the Internet at: https://www.epa.gov/assessing-and-managing-
chemicals-under-tsca/risk-management-and-polyfluoroalkvl-substances-pfas. Last
updated August 10, 2020.
USEPA. 2020c. Drinking Water Treatability Database.
https://iaspub.epa.gov/tdb/pages/general/home.do. Last updated March 2020.
United States Geological Survey (USGS). 2011. Report as ofFY2011 for 2010MD207B:
"Source Characterization of Contamination by Poly- and Per-fluorinated Chemicals
(PFCs) in Maryland Waterways."
Vermont Department of Environmental Conservation (VT DEC). 2016. North Bennington and
Bennington Private Well Testing Results (POFA, PFOS, PFHpA). Available on the
Internet at: https://dec.vermont.gov/sites/dec/files/co/pfoa/documents/NBenn-Benn-
Sample-Results-CURRENT.pdf.
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VT DEC. 2018. Perfluoroalkyl Substances (PFAS) Contamination Status Report. Available on
the Internet at:
https://anrweb.vt.gov/PubDocs/DEC/PFOA/Updates.%20Summaries.%20Articles/PFAS-
Sampling-Report-7.10.18-FINAL.pdf.
VT DEC. 2020. Per and Polyfluoroalkyl Substances (PFAS). Available on the Internet at:
https://dec.vermont.gov/water/drinking-water/water-qualitv-monitoring/pfas.
Wang, Y., G. Arsenault, N. Riddell, R. McCrindle, A. McAlees, and J.W. Martin. 2009.
Perfluorooctane sulfonate (PFOS) precursors can be metabolized enantioselectively:
Principle for a new PFOS source tracking tool. Environmental Science and Technology
43 (21), 8283-8289.
Washington, J.W., H. Yoo, J.J. Jackson, T.M. Jenkins, and E.L. Libelo. 2010. Concentrations,
distribution and persistence of perfluoroalkylates in sludge-applied soils near Decatur,
Alabama, USA. Environmental Science and Technology 44(22):8390-8396.
Washington, J.W., T.M. Jenkins, K. Rankin, and J.E. Naile. 2014. Decades-Scale Degradation of
Commercial, Side-Chain, Fluorotelomer-Based Polymers in Soils and Water.
Environmental Science and Technology 49(2): 915-923.
Washington, J.W., T.M. Jenkins, and E.J. Weber. 2015. Identification of unsaturated and 2H
polyfluorocarboxylate homologous aeries and their detection in environmental samples
and as polymer degradation products. Environmental Science and Technology 49
(22): 13256-13263.
Water Quality Portal (WQP). 2017. Water Quality Portal Data Warehouse. Available on the
Internet at: https://www.waterqualitvdata.us/. Data Warehouse consulted December 2017.
Wilson, L.R. 2018. New York State Drinking Water Data: PFOA andPFOS. Bureau of Water
Supply Protection, Center for Environmental Health, New York State Department of
Health (NYSDOH). Available on the Internet at:
http://www.nvsac.org/files/NYS%20Drinking%20Water%20Data%20PF0As.pdf.
Yoo, H., J.W. Washington, T.M. Jenkins, and J.J. Ellington. 2011. Quantitative Determination of
Perfluorochemicals and Fluorotelomer Alcohols in Plants from Biosolid-Amended Fields
using LC/MS/MS and GC/MS. Environ. Sci. Technol. 45(19):7985-7990.
Zareitalabad, P., J. Siemens, M. Hamer, and W. Amelung. 2013. Perfluorooctanoic Acid (PFOA)
and Perfluorooctanesulfonic Acid (PFOS) in Surface Waters, Sediments, Soils, and
Wastewater - A Review on Concentrations and Distribution Coefficients. Chemosphere
91:725-732.
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Chapter 5:
1,1 -Dichloroethane
A chapter from:
Final Regulatory Determination 4 Support Document
EPA Report 815-R-21-001
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Contents
Contents 5-2
Exhibits 5-3
Abbreviations 5-4
5.1 Contaminant Background and Chemical and Physical Properties 5-6
5.2 Sources and Environmental Fate 5-7
5.2.1 Production, Use, and Release 5-7
5.2.2 Environmental Fate 5-10
5.3 Health Effects 5-11
5.3.1 Toxicokinetics 5-11
5.3.2 Available Health Effect Assessments 5-11
5.3.3 Health Effects 5-12
5.3.4 Basis of the HRL 5-15
5.3.5 Data Base Limitations 5-17
5.3.6 Health Effects Data Gaps 5-17
5.4 Occurrence 5-17
5.4.1 Occurrence in Ambient Water 5-17
5.4.2 Occurrence in Drinking Water 5-24
5.4.3 Other Data 5-45
5.5 Analytical Methods 5-46
5.6 Treatment Technologies 5-46
5.7 References 5-47
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Exhibits
Exhibit 5-1: Chemical Structure of 1,1-Dichloroethane 5-6
Exhibit 5-2: Physical and Chemical Properties of 1,1-Dichloroethane 5-6
Exhibit 5-3: IUR Reported Annual Manufacture and Importation of 1,1-Dichloroethane in
the United States, 1986-2006 (pounds) 5-8
Exhibit 5-4: CDR Reported Annual Manufacture and Importation of 1,1-Dichloroethane
Production in the United States, 2011-2015 (pounds) 5-8
Exhibit 5-5: Environmental Releases of 1,1-Dichloroethane in the United States, 1994-
2016 5-9
Exhibit 5-6: Summary and State Count of Total Releases and Total Surface Water
Discharges of 1,1-Dichloroethane, 1994-2016 5-10
Exhibit 5-7: Available Health Effects Peer Reviewed Assessments for 1,1-Dichloroethane.... 5-12
Exhibit 5-8: 1,1-Dichloroethane NAWQA Data - Summary of Detected Concentrations 5-19
Exhibit 5-9: 1,1-Dichloroethane NAWQA Data - Summary of Samples 5-19
Exhibit 5-10: 1,1-Dichloroethane NAWQA Data - Summary of Sites 5-20
Exhibit 5-11: 1,1-Dichloroethane NWIS Data, 1991 -2016 5-22
Exhibit 5-12: 1,1-Dichloroethane STORET Data - Summary of Detected Concentrations 5-23
Exhibit 5-13: 1,1-Dichloroethane STORET Data - Summary of Samples and Sites 5-23
Exhibit 5-14: 1,1-Dichloroethane STORET Data - Summary of States 5-24
Exhibit 5-15: 1,1-Dichloroethane Occurrence Data from UCMR 3 Assessment Monitoring
- Summary of Detected Concentrations 5-26
Exhibit 5-16: 1,1-Dichloroethane National Occurrence Measures Based on UCMR 3
Assessment Monitoring Data - Summary of Samples 5-27
Exhibit 5-17: 1,1-Dichloroethane National Occurrence Measures Based on UCMR 3
Assessment Monitoring Data - Summary of System and Population Served Data -
All Detections 5-28
Exhibit 5-18: 1,1-Dichloroethane Occurrence Data from UCM Rounds 1 and 2 - Summary
of Detected Concentrations 5-30
Exhibit 5-19: 1,1-Dichloroethane Occurrence Data from UCM Rounds 1 and 2 - Summary
of Samples 5-30
Exhibit 5-20: 1,1-Dichloroethane Occurrence Data from UCM Rounds 1 and 2 - Summary
of System and Population Served Data - All Detections 5-31
Exhibit 5-21: 1,1-Dichloroethane State Drinking Water Occurrence Data - Summary of
Detected Concentrations 5-33
Exhibit 5-22: 1,1-Dichloroethane State Drinking Water Occurrence Data - Summary of
Samples 5-36
Exhibit 5-23: 1,1-Dichloroethane State Drinking Water Occurrence Data - Summary of
Systems 5-39
Exhibit 5-24: 1,1-Dichloroethane Data from Public-Supply Wells (Toccalino et al., 2010) -
Summary of Detected Concentrations 5-43
Exhibit 5-25: 1,1-Dichloroethane Data from Public-Supply Wells (Toccalino et al., 2010) -
Summary of Samples 5-43
Exhibit 5-26: 1,1-Dichloroethane Data from Source Water (Hopple et al., 2009 and
Kingsbury et al., 2008) - Summary of Detections from Phase 1 5-44
Exhibit 5-27: 1,1-Dichloroethane Data from Source Water (Hopple et al., 2009) -
Summary of Detections from Phase 2 - Groundwater 5-44
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Abbreviations
ACGIH
American Conference of Governmental Industrial Hygienists
ATSDR
Agency for Toxic Substances and Disease Registry
AwwaRF
American Water Works Association Research Foundation
BW
Body Weight
CalEPA
California Environmental Protection Agency
CAS
Chemical Abstracts Service
CCL
Contaminant Candidate List
CCL4
Fourth Contaminant Candidate List
CCR
Consumer Confidence Report
CDC
Centers for Disease Control and Prevention
CDR
Chemical Data Reporting
CSF
Cancer Slope Factor
CUS
Chemical Update System
CWS
Community Water System
CWSS
Community Water System Survey
DNA
Deoxyribonucleic Acid
DWI
Drinking Water Intake
EPA
Environmental Protection Agency
EPCRA
Emergency Planning and Community Right-To-Know Act
GAC
Granular Activated Carbon
GGT
Gamma-Glutamyl Transpeptidase
GWUDI
Groundwater Under the Direct Influence of Surface Water
HRL
Health Reference Level
HSDB
Hazardous Substances Data Bank
ICR
Information Collection Request
IRIS
Integrated Risk Information System
IUR
Inventory Update Reporting
Kh
Henry's Law Constant
Koc
Organic Carbon Partitioning Coefficient
Kow
Octanol-Water Partitioning Coefficient
LCMRL
Lowest Concentration Minimum Reporting Level
LD
Lethal Dose
LOAEL
Lowest Observed Adverse Effect Level
LOD
Limit of Detection
MRL
Minimum Reporting Level
NAWQA
National Water Quality Assessment
NCI
National Cancer Institute
ND
No Detection
NHANES
National Health and Nutrition Examination Survey
NIRS
National Inorganics And Radionuclides Survey
NOAEL
No Observed Adverse Effect Level
NPDES
National Pollutant Discharge Elimination System
NPDWR
National Primary Drinking Water Regulation
NWIS
National Water Information System
OEHHA
Office of Environmental Health Hazard Assessment
ORD
Office of Research and Development
PA
Principal Aquifer
PHG
Public Health Goal
PPRTV
Provisional Peer-Reviewed Toxicity Value
PWS
Public Water System
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RfD
Reference Dose
RSC
Relative Source Contribution
RSD
Relative Standard Deviation
SDWIS
Safe Drinking Water Information System
SDWIS/Fed
Safe Drinking Water Information System/Federal Version
SIM
Selected Ion Monitoring
SOC
Synthetic Organic Compound
STORET
Storage and Retrieval Data System
SYR2
Six-Year Review 2
SYR3
Six-Year Review 3
TRI
Toxics Release Inventory
TSCA
Toxic Substances Control Act
UCM
Unregulated Contaminant Monitoring
UCMR
Unregulated Contaminant Monitoring Rule
UCMR 1
First Unregulated Contaminant Monitoring Rule
UCMR 2
Second Unregulated Contaminant Monitoring Rule
UCMR 3
Third Unregulated Contaminant Monitoring Rule
USGS
United States Geological Survey
VOC
Volatile Organic Compound
WHO
World Health Organization
WQP
Water Quality Portal
WRF
Water Research Foundation
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Chapter 5: 1,1-Dichloroethane
The Environmental Protection Agency (EPA) is evaluating 1,1-dichloroethane as a
candidate for regulation as a drinking water contaminant under the fourth Contaminant
Candidate List (CCL 4) Regulatory Determinations process. Information on the CCL 4 process is
found in Chapter 1. Background on data sources used to evaluate CCL 4 chemicals is found in
Chapter 2.
This chapter presents information and analyses specific to 1,1-dichloroethane, including
background information on the contaminant, information on contaminant sources and
environmental fate, an analysis of health effects, an analysis of occurrence in ambient and
drinking water, and information about the availability of analytical methods and treatment
technologies.
5.1 Contaminant Background and Chemical and Physical Properties
1,1-Dichloroethane is a semivolatile chlorinated alkane. As an industrial chemical, it is
present in degreasing agents and used as a solvent for paints and plastics. 1,1-Dichloroethane is
also an intermediate in the synthesis of other organochlorine alkanes, principally 1,1,1-
trichloroethane. Synonyms for 1,1-dichloroethane include ethylidene chloride, according to the
Hazardous Substances Data Bank (HSDB, 2018).
The diagram in Exhibit 5-1 shows the chemical structure of 1,1-dichloroethane:
Exhibit 5-1: Chemical Structure of 1,1-Dichloroethane
CH.
/ J
CI—
A
CI
Source: USEPA, 2019a
Physical and chemical properties that impact contaminant fate and transport are reported
in Exhibit 5-2.
Exhibit 5-2: Physical and Chemical Properties of 1,1-Dichloroethane
Property
Data
Chemical Abstracts Service (CAS)
Registry Number
75-34-3 (ChemlDPIus, 2018)
EPA Pesticide Chemical Code
Not applicable
Chemical Formula
C2H4CI2 (ChemlDPIus, 2018)
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Property
Data
Molecular Weight
98.959 g/mol (HSDB, 2018)
Color/Physical State
Colorless/oily liquid (HSDB, 2018)
Boiling Point
57.4 deg C (HSDB, 2018)
Melting Point
-96.93 deg C (HSDB, 2018)
Density
1.175 at 20 deg C relative to water at 4 deg C (specific gravity;
HSDB, 2018)
1.1680 at 25 deg C relative to water at 4 deg C (specific gravity;
HSDB, 2018)
Freundlich Adsorption Coefficient
65 (|ig/g)(L/|ig)1/n (Speth etal., 2001)
Vapor Pressure
227 mm Hg at 25 deg C (HSDB, 2018)
Henry's Law Constant (Kh)
0.00562 atm-m3/mol at 24 deg C (HSDB, 2018)
Log Kow
1.79 (dimensionless; HSDB, 2018)
Koc
9.2 and 30 L/kg (HSDB, 2018)
Solubility in Water
5,040 mg/L at 25 deg C (HSDB, 2018)
Other Solvents
Miscible with chlorinated and oxygenated solvents (HSDB, 2018)
Conversion Factors
(at 25 deg C, 1 atm)
1 ppm (v/v) = 0.247 mg/m3
1 mg/m3 = 4.04 ppm (v/v)
(calculated)
Note: Many of these properties are temperature dependent. Values are given for properties at 20-25 deg C unless
otherwise noted. Due to varying experimental conditions, and due to the variabilities associated with modeling, the
standard information sources may provide a range of values. Where more than one value was available from these
sources, one value was selected for this table based on best professional judgment.
5.2 Sources and Environmental Fate
5.2.1 Production, Use, and Release
Production data from the EPA Inventory Update Reporting (IUR) and Chemical Data
Reporting (CDR) programs, and industrial release data from EPA's Toxics Release Inventory
(TRI) are available for 1,1-dichloroethane. Additional information about these sources is
provided in Chapter 2.
Chemical Update System (CUS) — Inventory Update Reporting (IUR) Program
Under the authority of the Toxic Substances Control Act (TSCA), EPA gathers
information on production (including both manufacture and importation) of industrial chemicals.
Under the IUR, producers provided information once every four years from 1986 to 2006. Since
2012, producers have continued to provide information in accordance with the CDR Rule that
superseded the IUR in 2011. Under CDR, producers collect annual production data and report it
once every four years.
Until 2006, the IUR regulation required manufacturers and importers of organic chemical
substances included on the TSCA Chemical Substance Inventory to report site and
manufacturing information for chemicals produced (i.e., manufactured or imported) in amounts
of 10,000 pounds or more at a single site. In 2006, the minimum threshold for reporting was
increased to 25,000 pounds and reporting began for inorganic chemicals (USEPA, 2008a).
Among changes made under CDR, a two-tier system of reporting thresholds was implemented,
with 25,000 pounds as the threshold for some contaminants and 2,500 pounds as the threshold
for others (USEPA, 2014; USEPA, 2018). As a result of program modifications, the results from
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2006 and later might not be directly comparable to results from earlier years. Under CDR, every
four years manufacturers and importers are required to report annual data from each of the
previous four years, provided that the thresholds of 2,500 or 25,000 pounds are met during at
least one of the four years (USEPA, 2018).
For the historical IUR data, EPA assigned one of eight production volume ranges for
each chemical included in the inventory. The ranges used for the 2006 reports differ slightly
from those used in the 1986 through 2002 reports, as described in Chapter 2. Exhibit 5-3 presents
the publicly available information on production of 1,1-dichloroethane in the United States from
1986 to 2006 as reported under IUR. Production of 1,1-dichloroethane in the United States has
generally declined since reporting began in 1986.
Exhibit 5-4 presents the publicly available production data for 1,1-dichloroethane in the
United States from 2011 to 2015 as reported under CDR. Production in 2011 was in the range of
one to ten million pounds. No quantitative data are available for subsequent years.
Exhibit 5-3: IUR Reported Annual Manufacture and Importation of
1,1-Dichloroethane in the United States, 1986-2006 (pounds)
Chemical Inventory Update Reporting Cycle
1986
1990
1994
1998
2002
2006
Range of
Production
Volume
> 100 million -
500 million
> 100 million -
500 million
> 500,000-
1 million
> 1 million -
10 million
> 500,000-
1 million
500,000 to < 1
million
Source: USEPA, 2008a
Exhibit 5-4: CDR Reported Annual Manufacture and Importation of
1,1-Dichloroethane Production in the United States, 2011-2015 (pounds)
Chemical Inventory Update Re
porting Cycle
2011
2012
2013
2014
2015
Range of Production /
Importation Volume
1 million -10
million
Withheld
Withheld
Withheld
Withheld
"Withheld" = results not publicly available due to confidential business information.
Source: USEPA, 2018
Toxics Release Inventory (TRI)
EPA established TRI in 1987 in response to section 313 of the Emergency Planning and
Community Right-to-Know Act (EPCRA). EPCRA section 313 requires the reporting of annual
information on toxic chemical releases from facilities that meet specific criteria. This reported
information is maintained in a database accessible through TRI Explorer (USEPA, 2017a).
Although TRI can provide a general idea of release trends, it has limitations. Not all
facilities are required to report all releases. Facilities are required to report releases if they
manufacture or process more than 25,000 pounds of a chemical or use more than 10,000 pounds
per year. Reporting requirements have changed over time (e.g., reporting thresholds have
decreased), so conclusions about temporal trends should be drawn with caution. TRI data are
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meant to reflect releases and should not be used to estimate general public exposure to a
chemical (USEPA, 2019b).
TRI data for 1,1-dichloroethane from the years 1994-2016 are summarized in Exhibit 5-5
(USEPA, 2017a). The data show that on-site air emissions dominated total reported releases;
these releases peaked in 2002 at more than 100,000 pounds. There were two isolated reporting
years with reported underground injections in the thousands of pounds. Other on-site releases
were minimal, and total off-site releases were decreased after 2008.
Exhibit 5-5: Environmental Releases of 1,1-Dichloroethane in the United States,
1994-2016
Year
On-Site Releases (in pounds)
Total Off-
Site
Releases
(in pounds)
Total On-
and Off-Site
Releases
(in pounds)
Air
Emissions
Surface
Water
Discharges
Underground
Injection
Releases to
Land
1994
34,242
0
0
0
1
34,243
1995
40,484
16
0
0
0
40,500
1996
21,958
11
0
0
0
21,969
1997
18,119
3
0
0
0
18,122
1998
44,468
0
0
0
8
44,476
1999
82,398
1
0
3
9
82,411
2000
15,209
0
0
0
17
15,226
2001
17,530
26
0
0
1,011
18,567
2002
103,359
95
0
80
267
103,801
2003
8,458
9
0
0
255
8,722
2004
11,259
63
5,741
0
252
17,315
2005
10,145
65
0
0
258
10,468
2006
10,143
196
0
0
264
10,603
2007
7,440
11
0
0
502
7,953
2008
6,881
235
0
0
38
7,155
2009
7,683
4
0
0
37
7,723
2010
8,475
75
0
0
31
8,580
2011
9,026
5
0
415
30
9,476
2012
29,339
6
0
2
18
29,365
2013
20,972
82
2,200
0
21
23,275
2014
8,570
54
0
7
17
8,648
2015
9,361
2
0
1
5
9,369
2016
8,331
0
0
0
3
8,334
Source: USEPA, 2017a
Exhibit 5-6 presents a summary of total releases and total surface water discharges that
includes the count of states reporting releases for the years 1994 to 2016 (USEPA, 2017a). Total
annual releases spiked in 2002 with 103,801 pounds; since then they have remained in the range
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of about 7,000 to 30,000 pounds. The number of states with releases of 1,1 dichloroethane has
stayed steady at about 5 states since 2004. The number of states with surface water discharges
has ranged from 0 to 3. (For the purposes of TRI, "state" counts include the District of Columbia
and U.S. territories in addition to the 50 states.)
Exhibit 5-6: Summary and State Count of Total Releases and Total Surface Water
Discharges of 1,1-Dichloroethane, 1994-2016
Year
Total Release
(in pounds)
Count of States
with Releases
Total Surface
Water
Discharges
(in pounds)
Count of States
with Surface
Water
Discharges
1994
34,243
2
0
0
1995
40,500
1
16
1
1996
21,969
3
11
1
1997
18,122
2
3
1
1998
44,476
5
0
0
1999
82,411
4
1
1
2000
15,226
4
0
0
2001
18,567
2
26
1
2002
103,801
3
95
3
2003
8,722
3
9
3
2004
17,315
5
63
3
2005
10,468
6
65
2
2006
10,603
5
196
2
2007
7,953
5
11
2
2008
7,155
4
235
2
2009
7,723
5
4
2
2010
8,580
4
75
2
2011
9,476
5
5
2
2012
29,365
6
6
1
2013
23,275
6
82
2
2014
8,648
6
54
2
2015
9,369
6
2
2
2016
8,334
6
0
0
Source: USEPA, 2017a
5.2.2 Environmental Fate
As discussed in Chapter 2, the measures used by EPA to assess mobility include (where
available) the organic carbon partitioning coefficient (Koc), log octanol-water partitioning
coefficient (log Kow), Henry's Law Constant (Kh), water solubility, and vapor pressure. 1,1-
Dichloroethane's vapor pressure of 227 mm Hg at 25 degrees C indicates that if it is released to
air, the contaminant will exist in the vapor phase. Based on Koc values of 9.2 and 30 L/kg,
1,1-dichloroethane is not expected to adsorb to soil and is very mobile in the environment. A Kh
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of 0.00562 atm-m3/mol indicates that 1,1-dichloroethane is expected to volatilize from soil and
water. A biodegradation half-life of 115 days, determined in groundwater under sulfate-reducing
conditions, suggests that biodegradation will be slow in water and soil. An anaerobic
biodegradation half-life of >30-60 days has also been reported. Hydrolysis is not expected to be
an important removal mechanism (HSDB, 2018).
Chapter 2 presents scales used by EPA to informally rank chemical contaminants' likely
mobility (understood as their tendency to partition to water rather than other media) and
persistence as "high," "moderate," or "low" based on physical and chemical properties (see
Exhibit 2-2 and Exhibit 2-3). For 1,1-dichloroethane, Koc values of 9.2 and 30 L/kg and a water
solubility of 5,040 mg/L indicate a high likelihood of partitioning to water. The log Kow of 1.79
indicates a moderate likelihood of partitioning to water, while a Kh of 0.00562 atm-m3/mol
indicates a low likelihood of partitioning to water. The biodegradation half-life of 115 days
under sulfate-reducing conditions indicates high persistence while the anaerobic half-life of >30-
60 days indicates moderate to high persistence.
5.3 Health Effects
5.3.1 Toxicokinetics
1,1-Dichloroethane is rapidly absorbed following oral and inhalation exposures and
distributed to tissues (ATSDR, 2015). It is metabolized primarily to acetic acid, with smaller
amounts of 2,2-dichloroethanol, dichloroacetic acid and monochloroacetic acid as minor
metabolites. Mitoma et al. (1985) reported that in rats about 86 percent of a single oral dose
(-700 mg/kg) was excreted, mostly unchanged, in expired air. Five percent of the radiolabel was
exhaled as carbon dioxide. Less than 1 percent of the radiolabel was present in urine (ATSDR,
2015; CalEPA, 2003).
5.3.2 Available Health Effect Assessments
Exhibit 5-7 presents a summary of the available health effects assessments for 1,1-
dichloroethane. The most recent peer reviewed EPA assessment for 1,1-dichloroethane was
completed by the EPA Office of Research and Development (ORD) for the Superfund program
(USEPA, 2006). This assessment provides a chronic, oral Provisional Peer-Reviewed Toxicity
Value (PPRTV) Reference Dose (RfD) of 0.2 mg/kg/day based on a study by Muralidhara et al.
(2001). As indicated by the bolded row in Exhibit 5-7, this study was selected for use in the
calculation of the Health Reference Level (HRL) (see Section 5.3.4 below for details). In the
1990 assessment for the EPA Integrated Risk Information System (IRIS), 1,1-dichloroethane is
classified as a possible human carcinogen in Group C without a quantified cancer slope factor
(CSF) based on the findings from a 1978 National Cancer Institute (NCI) Bioassay.
A 2015 assessment by Agency for Toxic Substances and Disease Registry (ATSDR) did
not quantify a minimal risk level for any adverse non-cancer effects and included the EPA Group
C finding for cancer. The California Environmental Protection Agency (CalEPA), World Health
Organization (WHO) and American Conference of Governmental Industrial Hygienists
(ACGIH) have published cancer assessments of 1,1-dichloroethane. Among the agencies other
than EPA, only CalEPA has considered it to be carcinogenic. WHO and ACGIH cite database
limitations as the reason for not assigning a cancer descriptor.
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Exhibit 5-7: Available Health Effects Peer Reviewed Assessments for
1,1-Dichloroethane
Health Assessment
Assessment
Year
RfD
(mg/kg/day)
Principal
study for
RfD
CSF
(mg/kg/
day)1
Principal
study for
CSF
Cancer
Descriptor
EPA Office of
Group C
Research and
Development (ORD)
Provisional Peer-
Reviewed Toxicity
Value (PPRTV)
2006
0.2
Muralidhara
et al., 2001
References
1990 IRIS
assessment
NA
(suggestive
evidence of
carcinogenic
potential) as
per IRIS
EPA Integrated Risk
Information System
1990
No value
NA
No value
NA
Group C
(suggestive
evidence of
(IRIS)
carcinogenic
potential)
Agency for Toxic
Substances and
2015
No value
NA
No value
NA
Inconclusive
Disease Registry
Evidence
(ATSDR)
California
NCI
Environmental
Protection Agency
2003
No value
NA
0.0057
(1978)
Female
Carcinogenic
(CalEPA)
rats
Not classified
World Health
Organization (WHO)
2003
No value
NA
No value
NA
due to
database
limitations
5.3.3 Health Effects
Very high concentrations (26,000 ppm) of 1,1-dichloroethane were once used as an
anesthetic (ATSDR, 2015). Because of this use, it can be inferred that 1,1-dichloroethane causes
a depressed central nervous system response following acute, high-concentration exposures. The
anesthetic use was discontinued because cardiac arrhythmias were noted in humans treated with
1,1-dichloroethane (ATSDR, 2015). Reported median lethal dose (LD50) values in rats range
from 700-14,100 mg/kg (CalEPA, 2003; WHO, 2003).
Systemic Toxicity
In a 13-week study, rats were administered 1,1-dichloroethane in corn oil by gavage at
doses of 0.5, 1, 2, and 4 g/kg/day, 5 days per week. Normalized for a 7-day per week exposure,
the doses were 360, 714, 1,430, and 2,860 mg/kg/day (Muralidhara et al., 2001). No significant
effects were observed at 0.5 g/kg/day. There were transient increases in urinary acid phosphatase
and A-acetylglucosamine at the 1 g/kg/day dose although these increases did not persist and were
not accompanied by dose-related changes in kidney weight, number of nephrotic lesions, or
increases in blood urea nitrogen. The study authors concluded that the lowest observed adverse
effect level (LOAEL) was the 1 g/kg/day dose. However, the 1 g/kg/day dose was classified as a
no observed adverse effect level (NOAEL) in the USEPA (2006) assessment, because the
increases in urinary acid phosphatase and A-acetylglucosamine were transient. There was a
statistically significant decreased body weight gain at 2 g/kg/day, supporting its designation as
the LOAEL by USEPA (2006) with a NOAEL of 1 g/kg/day. There was high mortality for the 4
g/kg/day group. The body weight effects were attributed to decreased food and water intake
because of narcosis (stupor) in rats receiving the higher oral 1,1-dichloroethane intakes.
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An inhalation study in cats (Hofmann et al., 1971) identified effects on kidney function
(increased serum creatinine and urea) and histopathology (renal tubular crystalline deposits) as
critical effects after a 13-week exposure with 500 ppm followed by a 13-week exposure in the
same animals with 1,000 ppm, resulting in a NOAEL of 500 ppm and a LOAEL of 1,000 ppm.
Similar manifestations of kidney toxicity did not occur in the oral studies of 1,1-dichloroethane,
although renal effects were observed following inhalation exposures (300 ppm) in Sprague
Dawley rats as discussed above.
An inhalation study in cats (Hofmann et al., 1971) identified effects on kidney function
(increased serum creatinine and urea) and histopathology (renal tubular crystalline deposits) as
critical effects after a 13-week exposure with 500 ppm followed by a 13-week exposure in the
same animals with 1,000 ppm, resulting in a NOAEL of 500 ppm and a LOAEL of 1,000 ppm.
Similar manifestations of kidney toxicity did not occur in the oral studies of 1,1-dichloroethane,
although renal effects were observed following inhalation exposures (300 ppm) in Sprague
Dawley rats as discussed above.
Reproductive and Developmental Toxicity
The only available study of the reproductive or developmental toxicity of 1,1-
dichloroethane is an inhalation study where pregnant rats were exposed to 1,1-dichloroethane on
days 6 through 15 of gestation (Schwetz et al., 1974). No effects on the fetuses were noted at
3,800 ppm. Delayed ossification of the sternum without accompanying malformations was
reported at a concentration of 6,000 ppm in air.
Carcinogenicity
The National Cancer Institute (NCI, 1978) performed a bioassay in which rats (Osborn
Mendel) and mice (B6C3Fi) were exposed to 1,1-dichloroethane via gavage 5 days per week for
78 weeks at doses ranging from 273 to 679 mg/kg/day (as normalized to 7 days per week) for
rats, and 1,030 to 2,379 mg/kg/day (also normalized to 7 days per week) for mice. The chemical
tested was technical grade and dosing levels varied during the study and were adjusted either up
or down based on the clinical signs exhibited in the male and female rats for all doses as well as
for the male and female mice1 in the high dose groups.
Mortality was significant in all dose groups including the controls. For example, among
the male rats, only 5 percent of the corn oil controls, 4 percent of the low dose males, and 8
percent of the high dose males survived to study termination compared to 30 percent for the
untreated controls. Among the female rats, survival was somewhat better. Forty percent of the
untreated controls, 20 percent of the corn oil controls, 16 percent of the low dose, and 18 percent
of the high dose animals survived until study termination. The high mortality in rats appeared to
be caused by pneumonia, possibly reflecting some delivery to the lungs during the gavage
dosing. Treatment lasted 78 weeks with another 33 weeks post dosing prior to sacrifice. No
1 Because dosing was adjusted multiple times during the study, the NCI published time weighted average doses
calculated by summing the doses administered for each of the 5 days per week across the duration of the study and
dividing it by 78 weeks. There were cases where no dose was given on some days or groups of days because of
observations of toxicity in the animals. Thus, the doses reported by NCI as "time averaged" represent normalized
values for 5 days per week. The doses presented in this summary were further normalized to represent the NCI doses
spread over a 7 day per week exposure period. They differ from the time weighted average doses reported in the
NCI (1978) report.
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treatment-related non-tumor histological effects were identified in the rat organs examined post-
mortem (NCI, 1978).
Survival was much better among the B6C3Fi mice and ranged from 35 percent to 62
percent for the males and 50 percent to 80 percent for the females. There was no dose-related
pattern to the early deaths among the male mice. Among the females, the survival was 80 percent
for the untreated controls, treated controls and low dose group; terminal survival for the high
dose animals was 50 percent (NCI, 1978).
The NCI (1978) concluded that there were dose-related marginal increases in mammary
adenocarcinomas and in hemangiosarcomas among female rats. Significance for the tumors
varied by whether matched or pooled controls were evaluated. Among the mice there was an
increase in the incidence of endometrial stromal polyps for dosed females as compared to
controls. Using Fisher's exact test, the polyp data did not achieve statistical significance. The
same was true for the mammary adenocarcinomas evaluated using Fisher's exact test (NCI,
1978). The peer reviewers agreed with the NCI determination. One peer reviewer felt that
housing of the 1,1-dichloroethane animals with others simultaneously being studied in
toxicological evaluations of 17 other chemicals was a protocol weakness that strengthened his
confidence in the NCI (1978) conclusion that there was no conclusive evidence for
carcinogenicity in the rats or mice. The high mortality among the male and female rats
minimized statistical power of the study (USEPA, 1990).
In a second cancer study, groups of male mice were exposed to concentrations of 835 or
2,500 mg/L 1,1-dichloroethane in drinking water for 52 weeks, with or without
diethylnitrosamine (10 mg/L) as a tumor initiator for the first four weeks of the study (Klaunig et
al., 1986). No increases in tumors were found in either group when compared to controls.
Genotoxicity
ATSDR (2015), CalEPA (2003), and WHO (2003) concluded that the results from the
genotoxicity studies of 1,1-dichloroethane are inconsistent. For example, it was mutagenic in
some strains of Salmonella typhimurium, with and without metabolic activation, but not in other
strains. Additionally, 1,1-dichloroethane induced chromosome abnormalities in the fungus
Aspergillus nidulans but was nonmutagenic in yeast cells (CalEPA, 2003). It increased the
frequency of cell transformations in Syrian hamster embryo cells, but not in mouse BALB/C-3T3
embryo cells (CalEPA, 2003; WHO, 2003). Colacci et al. (1985) reported that 1,1-
dichloroethane metabolites bind covalently to nucleic acids and proteins from liver, lung, kidney,
and stomach of male rats and mice lung and hepatic deoxyribonucleic acid (DNA) (ATSDR,
2015). The authors classified 1,1-dichloroethane's mutagenic potential as weak and attributed the
DNA adducts to microsomal cytochrome P450 metabolites.
Carcinogenic Mode of Action
The carcinogenic mode of action of 1,1-dichloroethane has not been established. Studies
have shown that 1,1-dichloroethane can bind to nucleic acids and proteins in vivo and in vitro,
and that it gives rise to free radicals under hypoxic conditions (ATSDR, 2015). The USEPA
(1990) reported that genotoxicity tests on 1,1-dichloroethane showed mixed results but made no
conclusions regarding the compound's genotoxicity.
The CalEPA (1992) Proposition 65 slope factor was the basis for the inclusion of 1,1-
dichloroethane on the Contaminant Candidate List (CCL) and its classification by EPA as a
known or suspected carcinogenic volatile organic compound (VOC) (USEPA, 2011). Under
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current EPA Office of Water guidelines, 1,1-dichloroethane would not be regulated as a
carcinogen because it is classified by IRIS (USEPA, 1990) as a Group C carcinogen. The
multiple concerns about the results of the NCI (1978) rat bioassay discussed above, and the low
potency reflected in the California Office of Environmental Health Hazard Assessment
(OEHHA) slope factor support the Group C classification. Twenty percent or less of the corn-oil
controls and the dosed rats survived to the terminal sacrifice limiting the statistical power of the
data (USEPA, 2006). Although a time to tumor analysis was applied for the OEHHA
quantification, the slope factor derivation described in the CalEPA (1992) report is not consistent
with the approach described by the current EPA Cancer Guidelines (USEPA, 2005). Under the
2005 guidelines, 1,1-dichloroethane would likely be classified as Suggestive evidence of
carcinogenic potential and the response to dose would not be quantified due to the weaknesses
inherent in the 1978 NCI study.
Sensitive Populations
According to NIOSH (1978) as cited in ATSDR (2015), the following groups of
individuals may have an increased risk from exposure to 1,1-dichloroethane:
• Those with chronic respiratory disease,
• Those with liver diseases that impact hepatic microsomal cytochrome P-450
functions,
• Individuals with impaired renal function and vulnerable to kidney stones, and
• Individuals with skin disorders vulnerable to irritation by solvents like 1,1-
dichloroethane.
Other sensitive populations may include alcohol consumers or users of pharmaceuticals
(e.g., phenobarbital) that alter the activity of cytochrome P-450s (ATSDR, 2015).
5.3.4 Basis of the HRL
The Regulatory Determination HRL for 1,1-dichloroethane was calculated as 1,000 [j,g/L
and is based on EPA's peer reviewed provisional RfD of 0.2 mg/kg/day (USEPA, 2006). The
RfD was derived using a normalized NOAEL of 714.3 mg/kg/day from a 13-week gavage study
in male rats (Muralidhara et al., 2001). The observed critical effect was an increase in kidney
urinary enzymes. The total uncertainty factor applied was 3,000 (10 for extrapolation from a
subchronic study, 10 for interspecies extrapolation, 10 for human variability, and 3 for database
deficiencies) (USEPA, 2006). Muralidhara et al., (2001) considered 714 mg/kg/day as aLOAEL
based on increases in urinary acid phosphatase and A-acetyl glucosamine. However, these effects
were not considered to be adverse by the PPRTV assessors (USEPA, 2006) because they were
transient and not accompanied by other indications of kidney damage.
BW
HRL = RfD * * RSC
' DWI
mq/kq 80 kq
HRL = 0.2 , * * 20%
day 2 ^
day
mg ng
HRL = 1.28—— = 1,280 ^
L L
HRL = 1,000 (rounded)
L
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RfD = Reference Dose (mg/kg/day); toxicity value selected based on protocol hierarchy
BW = Body weight (kg); based on adult default value of 80 kg
DWI = Drinking Water Intake (L/day); based on adult default value of 2.5 L/day
RSC = Relative Source Contribution, or the level of exposure believed to result from
drinking water when compared to other sources (e.g., food, ambient air), is 20 percent
when used for HRL derivation.
The overall confidence in the provisional RfD was ranked as low by ORD based on
medium confidence in the principal study. Despite an appropriate array of doses, the study was
limited by the marginally adequate reporting of the observed effects (USEPA, 2006). The
database lacks human data and there is limited information on developmental/reproductive and
neurological effects following oral exposures. The principal study reported clinical signs of
acute, post dosing central nervous system depression at the normalized dose of 1,429 mg/kg/day
(Muralidhara et al., 2001).
CalEPA (1992) quantified the cancer risk for 1,1-dichloroethane with a slope factor of
0.0057 (mg/kg/day)"1 for their Proposition 65 determination using the mammary gland
adenocarcinomas observed in female rats, the most sensitive species/sex combination tested in
the NCI (1978) cancer study. OEHHA policies identify "No Significant Risk Levels" for
carcinogens based on data collected by Gold et al. between 1984 and 1990 (CalEPA, 1992) to
identify the point of departure for slope factor determination. Several aspects of this
methodology differ from those of EPA. CalEPA (1992) appears to be the only agency that
quantified a slope factor for the cancer risk (See Exhibit 5-7). The OEHHA slope factor was used
to quantify the CalEPA (2003) Public Health Goal (PHG) for drinking water in combination with
a 70-kg body weight and a 4 L/day tap water exposure. The 4 L/day water consumption rate
accounts for direct water ingestion and inhalation from air through showering and/or ambient air.
The adjustment to the water intake volume follows a California policy applied for exposure to
volatile chemicals. The CalEPA PHG for 1,1-dichloroethane is 3 |ig/L.
The EPA IRIS assessment classifies 1,1-dichloroethane in Group C (possible human
carcinogen), based on limited evidence of carcinogenicity in rats and mice (NCI, 1978). The
USEPA (1990) assessment did not quantify the dose response for the cancer because of the low
survival rates for the rats and mice. The chemical tested was technical grade, the dosing was
intermittent due (5 days per week) and adjusted (up and down) several times across the 78-week
dosing period (NCI, 1978). There was early mortality among the all rat dose groups, including
the corn oil controls, and for the high dose mice (NCI, 1978).
Other regulatory agencies have agreed with EPA that the weaknesses in data from the
NCI (1978) study limit its utility for quantification of risk. ACGIH (2010) classified 1,1-
dichloroethane as Category A4, not classifiable as a human carcinogen. ATSDR (2015)
concluded that there is inconclusive evidence that 1,1-dichloroethane may be a carcinogen in
rodents based on the NCI (1978) rat and mouse study. WHO (2003) determined that the NCI
(1978) oral carcinogenicity study in mice and rats provided no conclusive evidence of
carcinogenicity but noted that following long-term oral exposures there was some evidence for
an increased incidence of mammary adenocarcinomas and hemangiosarcomas. NIOSH (2018)
recommended that 1,1-dichloroethane be treated as a potential occupational carcinogen because
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of its structural similarity to four chloroethanes shown to be carcinogenic in animals (ethylene
dichloride; hexachloroethane; 1,1,2,2-tetrachloroethane; and 1,1,2-trichloroethane); thus, this
classification was not based solely on data from the NCI (1978) cancer study.
5.3.5 Data Base Limitations
No human data were identified for oral exposure to 1,1-dichloroethane. The animal study
database has a paucity of data on the acute, subchronic, and chronic effects of 1,1-
dichloroethane. There are no oral studies on the reproductive or developmental effects of the
compound, and the genotoxicity database is lacking many standard in vitro mammalian cell
assays (e.g., mutations in mouse lymphoma cells) and in vivo mammalian assays (e.g., rodent
bone marrow micronucleus assays or chromosomal aberration assays in peripheral blood cells).
Although there are data from the NCI (1978) bioassay, they are of limited value because of the
poor survival in both treated and control animals (ATSDR, 2015; CalEPA, 2003; USEPA, 1990).
5.3.6 Health Effects Data Gaps
Data on the tumor mode of action of 1,1-dichloroethane would be valuable. An expanded
array of genotoxicity studies focusing on mode of action parameters could be useful if they
enabled a comparison with the other chlorinated ethanes that have a more comprehensive
toxicological database. Toxicokinetic data that compare the metabolism of 1,1-dichloroethane
with 1,1-dichloroethene, 1,2-dichloroethane, and dichloroacetic acid might also help with mode
of action considerations and the possible need to consider the chlorinated ethanes as a group.
The crystal deposits seen in the kidneys of exposed cats (Hofmann et al., 1971) could
possibly be oxalic acid, a major byproduct of dichloroacetic acid metabolism in humans and
animals (USEPA, 2003a). Dichloroacetic acid is a metabolite of 1,1-dichloroethane. A dose
response study for this effect in felines might be justified if applicable to humans susceptible to
oxalate kidney stones.
5.4 Occurrence
This section presents data on the occurrence of 1,1-dichloroethane in ambient water and
drinking water in the United States. As described in Section 5.3, an HRL of 1,000 |ig/L was
calculated for 1,1-dichloroethane. HRLs are risk-derived concentrations against which EPA
evaluates the occurrence data to determine if contaminants occur at levels of potential public
health concern. Occurrence data from various sources presented below are analyzed with respect
to the HRL and one-half the HRL. When possible, estimates of the population exposed at
concentrations above the HRL and above one-half the HRL are presented.
For additional background information about data sources used to evaluate occurrence,
please refer to Chapter 2.
5.4.1 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. Contaminant
occurrence in ambient water provides information on the potential for contaminants to adversely
affect drinking water supplies. Occurrence data for 1,1-dichloroethane in ambient water are
available from the United States Geological Survey (USGS) National Water-Quality Assessment
(NAWQA) program, the USGS National Water Information System (NWIS) database, EPA's
legacy Storage and Retrieval Data System (STORET) data available through the Water Quality
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Portal (WQP), and several published USGS studies. Additional ambient water data collected in
connection with finished drinking water data are presented in Section 5.4.2.
United States Geological Survey (USGS) National Water-Quality Assessment (NAWQA)
Ambient Water Analyses
USGS instituted the NAWQA program in 1991 to examine ambient water quality status
and trends in the United States. The NAWQA program generates high quality contaminant
occurrence and other water quality parameter data for significant watersheds and aquifers across
the nation. The program collects data on surface water and groundwater chemistry, hydrology,
land use, stream habitat, and aquatic life in parts or all of nearly all 50 States. The program is
designed to apply nationally consistent methods to provide a uniform basis for contaminant
occurrence comparisons and assessments among study basins across the country and over time.
The occurrence assessments can also serve to facilitate interpretation of natural and
anthropogenic factors affecting national water quality. For more detailed information on the
NAWQA program design and implementation, refer to Leahy and Thompson (1994) and
Hamilton et al. (2004).
The process of sampling, analysis, and data synthesis is divided into cycles of
approximately ten years: Cycle 1 covered 1991-2001, Cycle 2 covered 2002-2012, and Cycle 3 is
ongoing and covers 2013-2023. Study units are sampled and analyzed on a staggered schedule
within each cycle. Each NAWQA cycle begins with a two-year startup phase for planning and
retroactive analysis, followed by a three-year intensive data collection phase, and finally a five-
year phase for analyzing the data, developing reports, and continuing a low level of monitoring
(NRC, 2012).
During Cycle 1 (1991-2001), 51 study units were sampled. Data were gathered from
6,307 wells from 272 groundwater networks or clusters and from 6,400 sampling points at 505
surface water monitoring sites, primarily rivers and streams but also some lakes and reservoirs
(NRC, 2002). In Cycle 2 (2002-2012), the number of study units was reduced from 51 to 42
(NRC, 2012). Long-term stream monitoring was established at 113 streams representing 8 major
river basins. Long-term groundwater monitoring was established at sites representing 20
principal aquifers with more than 10 to 15 years of consistent monitoring data available (Rowe et
al., 2013).
Sampling for Cycle 3 is currently underway (2013-2023). Surface water monitoring will
be conducted at 313 sites, increased from 113 sites in Cycle 2 (Rowe et al., 2013). Groundwater
assessments in Cycle 3 will be designed to evaluate status and trends at the principal aquifer
(PA) and national scales. Assessments are planned in 24 PAs that account for the majority of
current and future national groundwater use for drinking water. Data available through 2017 are
presented in this report. For more details on the Cycle 3 sampling design, refer to Rowe et al.,
(2010 and 2013).
EPA's analysis of the NAWQA data is a simple, non-parametric occurrence analysis that
provides summary statistics to characterize contaminant occurrence. EPA calculated detection
frequencies as the percentage of samples and the percentage of sites with at least one detection,
without any censoring or weighting. (A detection is an analytical result equal to or greater than
the reporting level.) EPA reported the minimum and maximum detected concentrations and
calculated other descriptive statistics including the median, 90th percentile, and 99th percentile
concentrations (based only on samples with detections). Reporting levels varied over time during
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the NAWQA program. In some cases, therefore, the minimum concentration reported as a
detection could be lower than the highest reporting level.
Exhibit 5-8 through Exhibit 5-10 present analyses of the 1,1-dichloroethane NAWQA
data, downloaded from the Water Quality Portal in September 2018 (WQP, 2018). In all three
cycles, 1,1-dichloroethane was detected in between 2 percent and 4 percent of samples from
between 2 percent and 4 percent of sites. (Some sites were sampled in more than one cycle.) No
detections were greater than the HRL. The median concentrations based on detections were
0.046 |ig/L, 0.056 |ig/L, and 0.022 |ig/L in Cycle 1, Cycle 2, and Cycle 3, respectively. As noted
above, NAWQA data are ambient water data, not finished drinking water data.
Note that there may be some overlap between the NAWQA data assessment presented
here and summaries of individual NAWQA studies presented below.
Exhibit 5-8: 1,1-Dichloroethane NAWQA Data - Summary of Detected
Concentrations
Site Type
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Cycle 1 (1991 -2001)
Groundwater
0.01
0.063
0.500
4.10
39
Surface Water
0.01
0.040
0.084
0.232
34
All Sites
0.01
0.046
0.294
3.84
39
Cycle 2 (2002-2012)
Groundwater
0.009
0.060
0.241
1.70
3.9
Surface Water
0.011
0.033
0.144
0.155
0.156
All Sites
0.009
0.056
0.209
1.58
3.9
Cycle 3 (2013-2017)
Groundwater
0.012
0.022
0.089
0.630
0.93
Surface Water
0.014
0.144
0.222
0.269
0.274
All Sites
0.012
0.022
0.096
0.661
0.93
Source: WQP, 2018
Exhibit 5-9: 1,1-Dichloroethane NAWQA Data - Summary of Samples
Site Type
No. of
Samples
Detection Frequency
(detections are results > reporting level)
No. of
Samples
with
Detections
%
Samples
with
Detections
No. of
Samples
with
Detections
> 1/2 HRL
%
Samples
with
Detections
> 1/2 HRL
No. of
Samples
with
Detections
> HRL
%
Samples
with
Detections
> HRL
Cycle 1 (1991 -2001)
Groundwater
4,966
152
3.06%
0
0.00%
0
0.00%
Surface Water
1,489
109
7.32%
0
0.00%
0
0.00%
All Sites
6,455
261
4.04%
0
0.00%
0
0.00%
Cycle 2 (2002-2012)
Groundwater
4,992
148
2.96%
0
0.00%
0
0.00%
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Site Type
No. of
Samples
Detection Frequency
(detections are results > reporting level)
No. of
Samples
with
Detections
%
Samples
with
Detections
No. of
Samples
with
Detections
> 1/2 HRL
%
Samples
with
Detections
> 1/2 HRL
No. of
Samples
with
Detections
> HRL
%
Samples
with
Detections
> HRL
Surface Water
551
21
3.81%
0
0.00%
0
0.00%
All Sites
5,543
169
3.05%
0
0.00%
0
0.00%
Cycle 3 (2013-2017)
Groundwater
1,559
39
2.50%
0
0.00%
0
0.00%
Surface Water
161
2
1.24%
0
0.00%
0
0.00%
All Sites
1,720
41
2.38%
0
0.00%
0
0.00%
Source: WQP, 2018
Exhibit 5-10: 1,1-Dichloroethane NAWQA Data-Summary of Sites
Site Type
No. of
Sites
Detection Frequency
(detections are results > reporting level)
No. of
Sites with
Detections
% Sites
with
Detections
No. of
Sites with
Detections
> 1/2 HRL
% Sites
with
Detections
> 1/2 HRL
No. of
Sites with
Detections
> HRL
% Sites
with
Detections
> HRL
Cycle 1 (1991 -2001)
Groundwater
4,460
145
3.25%
0
0.00%
0
0.00%
Surface Water
187
23
12.30%
0
0.00%
0
0.00%
All Sites
4,647
168
3.62%
0
0.00%
0
0.00%
Cycle 2 (2002-2012)
Groundwater
3,204
97
3.03%
0
0.00%
0
0.00%
Surface Water
56
3
5.36%
0
0.00%
0
0.00%
All Sites
3,260
100
3.07%
0
0.00%
0
0.00%
Cycle 3 (2013-2017)
Groundwater
1,486
35
2.36%
0
0.00%
0
0.00%
Surface Water
54
2
3.70%
0
0.00%
0
0.00%
All Sites
1,540
37
2.40%
0
0.00%
0
0.00%
Source: WQP, 2018
NA WQA VOC National Synthesis: Random and Focused VOC Surveys
Through a series of National Synthesis efforts, the USGS NAWQA program prepares
comprehensive analyses of data on topics of particular concern. These National Synthesis
assessments aggregate NAWQA contaminant occurrence and water quality parameter data from
individual study units and other sources to provide a national overview.
The Volatile Organic Compound (VOC) National Synthesis began in 1994. The most
comprehensive VOC National Synthesis reports to date are one random survey and one focused
survey funded by the Water Research Foundation (WRF) (formerly known as AwwaRF) and
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carried out by the USGS in collaboration with the Metropolitan Water District of Southern
California and Oregon Health & Science University. The random survey (Grady, 2002) targeted
surface waters and groundwaters used as source water by community water systems (CWSs).
Samples were taken from the source waters of 954 CWSs in 1999 and 2000. The random survey
was designed to be nationally representative of CWS source water. In the focused survey (Delzer
and Ivahnenko, 2003), 451 samples were taken from source waters serving 134 CWSs between
1999 and 2001. The focused survey was designed to provide insight into temporal variability and
anthropogenic factors associated with VOC occurrence. Both surveys reported the results of
multiple analytes, including 1,1-dichloroethane, at a common reporting level of 0.2 (J,g/L. Details
of the monitoring plan for these two studies, including detection limits, are provided by
Ivahnenko et al. (2001).
The random survey sampled groundwater and surface water sources used by 954
geographically representative CWSs in different size categories (Grady, 2002). At a reporting
level of 0.2 |ig/L, the national random survey of source waters (Grady, 2002) found
1,1-dichloroethane in 11 (1.2 percent of all samples, 1.9 percent of groundwater samples and 0
percent of surface water samples). Detections in groundwater ranged from 0.21 |ig/L to 10 |ig/L.
The focused survey investigated 134 CWS sources (56 surface water and 78
groundwater) between 1999 and 2001 (Delzer and Ivahnenko, 2003). These surface waters and
groundwaters were chosen because they were suspected or known to contain VOCs. At a
reporting level of 0.2 (J,g/L, the national focused survey (Delzer and Ivahnenko, 2003) found
1,1-dichloroethane in 5.3 percent of the CWS source waters sampled (9.2 percent of groundwater
sites and 0 percent of surface water sites). In addition, the focused survey provided results for
1,1-dichloroethane below the reporting level. At levels as low as the method detection limit
(0.036 (J,g/L), 1,1-dichloroethane was found in 15.9 percent of the CWS source waters sampled
(26.3 percent of groundwater sites and 1.8 percent of surface water sites). Detected
concentrations ranged from 0.04 [j,g/L to 3.85 [j,g/L (Delzer and Ivahnenko, 2003).
NA WQA VOC National Synthesis: Compilation of Historical VOC Monitoring Data
The VOC National Synthesis also includes a compilation of historical VOC monitoring
data from multiple studies (Squillace et al., 1999). These data were collected between 1985 and
1995 from 2,948 drinking water and non-drinking water wells in both rural and urban areas.
Sampling was done by local, state, and federal agencies, and data were reviewed by USGS to
ensure they met data quality criteria.
Multiple investigators collected samples of 1,1-dichloroethane from 405 urban wells and
2,539 rural wells. At a reporting level of 0.2 (J,g/L, the detection frequency for 1,1-dichloroethane
was 6.42 percent from urban wells and less than 1 percent from rural wells. Detections ranged
from the minimum reporting level (0.2 |ig/L) to 39 |ig/L. In urban wells, the median detected
concentration was 1.65 |ig/L; in rural wells, the median detected concentration was 2.3 |ig/L.
National Water Information System (NWIS) Data
The National Water Information System (NWIS) is the Nation's principal repository of
water resources data USGS collects from more than 1.5 million sites (USGS, 2016). NWIS-Web
is the general online interface to the USGS NWIS database. Discrete water-sample and time-
series data are available from sites in all 50 States, including 5 million water samples with 90
million water-quality results. All USGS water quality and flow data are stored in NWIS,
including site characteristics, streamflow, groundwater level, precipitation, and chemical
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analyses of water, sediment, and biological media, though not all parameters are available for
every site. NWIS houses the NAWQA data and includes other USGS data from unspecified
projects. NWIS contains many more samples at many more sites than the NAWQA Program.
Although NWIS is comprised of primarily ambient water data, some finished drinking water data
are included as well. This section presents analyses of non-NAWQA data in NWIS, downloaded
from the Water Quality Portal in December 2017 (WQP, 2017). These data do not overlap with
the results presented in Exhibit 5-8 through Exhibit 5-10.
The results of the non-NAWQA NWIS 1,1-dichloroethane analyses are presented in
Exhibit 5-11. 1,1-Dichloroethane was detected in approximately 5 percent of samples (1,152 out
of 24,560) and at approximately 5 percent of sites (620 out of 12,057). The median concentration
based on detections was equal to 0.380 |ig/L. (Note that the NWIS data are presented as
downloaded; potential outliers were not evaluated or excluded from the analysis.)
Exhibit 5-11: 1,1-Dichloroethane NWIS Data, 1991 -2016
Site Type
Detection Frequency
(detections are results > reporting level)
Concentration Values
(of detections, in |jg/L)
No. of
Samples
No. of
Samples
with
Detections
No. of
Sites
No. of
Sites with
Detections
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Groundwater
20,114
1,050
10,789
566
0.009
0.396
6.00
366
4,850
Surface Water
4,422
99
1,287
56
0.01
0.240
2.00
30.7
200
Finished Water
24
3
20
3
0.027
0.126
0.189
0.213
0.216
All Sites
24,560
1,152
12,057
620
0.009
0.380
5.48
283
4,850
Source: WQP, 2017
Storage and Retrieval (STORET) Data / Water Quality Portal (WQP)
From its launch in 1999 until it was decommissioned in June 2018, EPA's STORET Data
Warehouse was collaboratively populated with raw biological, chemical, and physical data from
surface water and groundwater sampling by federal, state and local agencies, Native American
tribes, volunteer groups, academics, and others. Legacy STORET data are accessible through the
Water Quality Portal (WQP): https://www.waterqualitvdata.us/portal/.
STORET data are from monitoring locations in all 50 states as well as multiple territories
and jurisdictions of the United States. Most data are from ambient waters, but in some cases
finished drinking water data are included as well. STORET's data quality limitations include
variations in the extent of national coverage and data completeness from parameter to parameter.
Data may have been collected as part of targeted, rather than randomized, monitoring.
STORET's data quality limitations include variations in the extent of national coverage and data
completeness from parameter to parameter. Data may have been collected as part of targeted,
rather than randomized, monitoring.
This section presents analyses of STORET data, downloaded from the WQP in December
2017 (WQP, 2017). EPA reviewed STORET groundwater data from wells and surface water data
from lakes, rivers/streams, and reservoirs (WQP, 2017). The WQP also included public water
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system (PWS) data from four states (Indiana, Missouri, Ohio, and Washington); EPA reviewed
these as well (WQP, 2017). It is unclear if the PWS data were collected prior to or subsequent to
treatment.
The results of the STORET analysis for 1,1-dichloroethane are presented in Exhibit 5-12
through Exhibit 5-14. These 1,1-dichloroethane samples were collected between 1984 and 2016.
Of the 5,735 sites sampled, 3,176 (55.4 percent) reported detections of 1,1-dichloroethane.
Detected concentrations ranged as high as 3,200 |ig/L. The 90th percentile concentration of
detections was equal to 5.0 |ig/L. The minimum detected concentration may be indicative of the
reporting levels used. (A minimum value of zero, on the other hand, could represent a detection
that was entered into the database as a non-numerical value (e.g., "Present").)
Exhibit 5-12: 1,1-Dichloroethane STORET Data - Summary of Detected
Concentrations
Source Water Type
Concentration Value of Detections (|jg/L)
Minimum1
Median
90th Percentile
Maximum
Groundwater
0
1.0
5.0
3,200
Surface Water
0
0.1
0.5
320
Total
0
1.0
5.0
3,200
PWS
0
0
0
2.02
Source: WQP, 2017
1A minimum value of zero may represent a detection that was entered into the database as a non-numerical value
(e.g., "Present").
Exhibit 5-13: 1,1-Dichloroethane STORET Data - Summary of Samples and Sites
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Total
Number
of Sites
Sites with Detections
Number
Percent
Number
Percent
Groundwater
35,064
19,745
56.31%
4,559
2,793
61.26%
Surface Water
14,949
1,060
7.09%
1,176
383
32.57%
Total
50,013
20,805
41.60%
5,735
3,176
55.38%
PWS
1,279
1,091
85.30%
187
186
99.47%
Source: WQP, 2017
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Exhibit 5-14: 1,1-Dichloroethane STORET Data - Summary of States
Source Water
Type
Total
Number of
States
States with Detections
Number
Percent
Groundwater
20
15
75.00%
Surface Water
32
12
37.50%
Total1
35
18
51.43%
PWS
2
2
100.00%
Source: WQP, 2017
1 The number of states with groundwater data plus the number of
states with surface water data may not equal the "Total" number of
states providing data because some states provided both
groundwater and surface water data.
Additional Ambient Water Studies
1,1-Dichloroethane data are available from a variety of USGS stormwater studies. For the
National Highway Runoff Data and Methodology Synthesis, USGS conducted a review of 44
highway and urban runoff studies conducted between the 1970s and the 1990s (Lopes and
Dionne, 1998). Three of these studies report results for 1,1-dichloroethane. Note that the data
from these studies might also be included in the NWIS results presented earlier.
The three studies with 1,1-dichloroethane results were stormwater studies conducted in
specific major metropolitan areas in connection with National Pollutant Discharge Elimination
System (NPDES) permitting. In metropolitan Phoenix (Maricopa County), USGS collected 35
samples from five drainage basins, and the City of Phoenix collected an additional 26 samples
from seven sites (Lopes et al., 1995). In Colorado Springs, USGS collected 35 samples from five
sites (von Guerard and Weiss, 1995). In Dallas-Fort Worth, 181 samples were collected from 26
stormwater drainage basins (Baldys et al., 1998). 1,1-Dichloroethane was detected in at least one
industrial sample in the Dallas-Fort Worth study; the maximum detected concentration was equal
to 8.3 (J,g/L. 1,1-Dichloroethane was not detected in the other studies.
5.4.2 Occurrence in Drinking Water
Data sources reviewed by the Agency for information on contaminant occurrence in
drinking water included: EPA's first, second, and third Unregulated Contaminant Monitoring
Rules (UCMR 1, UCMR 2, UCMR 3); Rounds 1 and 2 of the Agency's Unregulated
Contaminant Monitoring (UCM) program that preceded the Unregulated Contaminant
Monitoring Rule (UCMR); EPA's Information Collection Rule; EPA's National Inorganics and
Radionuclides Survey (NIRS); and a range of others as discussed in Chapter 2. Among the
sources reviewed, the following had data and information on 1,1-dichloroethane occurrence in
drinking water. These data and information are discussed in this section.
• EPA's Third Unregulated Contaminant Monitoring Rule (UCMR 3).
EPA's Unregulated Contaminant Monitoring (UCM) program, Rounds 1 and 2.
State drinking water monitoring programs.
EPA's Community Water System Survey (CWSS).
USGS source water and drinking water studies.
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Note that there may be some overlap, as sources with different purposes and audiences
may have reported the same underlying data. UCMR 3 and UCM Rounds 1 and 2 are national
data sources. Other data sources profiled in this section are considered "supplemental" sources.
Also note that the presentation of NWIS and STORET results in the ambient water section,
above, includes some miscellaneous finished water data and/or data from PWSs.
Primary Data Sources
EPA's Third Unregulated Contaminant Monitoring Rule (UCMR 3) 2013-2015
UCMR 3 monitoring, designed to provide nationally representative contaminant
occurrence data, was conducted from 2013 through 2015. UCMR 3 List 1 Assessment
Monitoring occurrence data are available for 1,1-dichloroethane. For UCMR 3, all large and very
large PWSs (serving between 10,001 and 100,000 people and serving more than 100,000 people,
respectively), plus a statistically representative national sample of 800 small PWSs (serving
10,000 people or fewer), were required to conduct Assessment Monitoring during a 12-month
period between January 2013 and December 2015. 2 Surface water (and groundwater under the
direct influence of surface water (GWUDI)) sampling points were monitored four times during
the applicable year of monitoring, and groundwater sampling points were monitored twice
during the applicable year of monitoring. See USEPA (2012) and USEPA (2019c) for more
information on the UCMR 3 study design and data analysis.
The design of UCMR 3 permits estimation of national occurrence by multiplying the total
number of systems (or population served) in the nation in a system size category by the percent
of systems expected to exceed a specified threshold. An extrapolation methodology is applied to
small systems because not all small systems were required to participate in the UCMR 3
Assessment Monitoring. Because all large and very large systems were required to participate in
the UCMR 3 Assessment Monitoring, national estimates of occurrence in these size categories
can be done using survey census figures rather than extrapolation. Total national occurrence is
estimated by summing the extrapolated figures for small systems and the census figures for the
large and very large systems.
Exhibit 5-15 through Exhibit 5-17 provide an overview of 1,1-dichloroethane occurrence
results from the UCMR 3 Assessment Monitoring. Laboratories participating in UCMR 3 were
required to report values at or above minimum reporting levels (MRLs) defined by EPA. The
MRLs are established to ensure reliable and consistent results from the array of laboratories
needed for a national monitoring program and are set based on the capability of multiple
commercial laboratories prior to the beginning each UCMR round. The MRL used for 1,1-
dichloroethane in the UCMR 3 survey was 0.03 |ig/L (77 FR 26072; USEPA, 2012). Exhibit
5-15 shows a statistical summary of 1,1-dichloroethane concentrations by system size and source
water type (including the minimum, median, 90th percentile, 99th percentile, and maximum).
Exhibit 5-16 presents a sample-level summary of the results. Exhibit 5-17 shows system-level
results, including national extrapolations, for detections greater than or equal to the MRL
threshold.
As noted above, UCMR 3 monitoring was required at a representative sample of small
systems and at all large and very large systems. As a reminder that the figures from large and
very large systems represent a census of systems in those categories, results in those categories
2 Only 799 small systems submitted Assessment Monitoring results.
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are labelled "CENSUS" in Exhibit 5-15 through Exhibit 5-17. No extrapolation was necessary in
these categories, as it was for the small systems, to derive national estimates of occurrence in
these exhibits. National estimates of occurrence are reported separately in each system size and
source water category, and also in aggregate.
A total of 36,848 finished water samples for 1,1-dichloroethane were collected from
4,916 systems. 1,1-Dichloroethane was measured > MRL in 2.27 percent of UCMR 3 samples.
Reported 1,1-dichloroethane concentrations for these "positive" results ranged from of 0.03 |ig/L
(the MRL) to 8.1 |ig/L. Of 4,916 systems, 244 (5.0 percent of systems, serving 8.7 percent of the
PWS-served population) reported at least one detection. Extrapolating these findings suggests
that an estimated 1,395 PWSs serving 22 million people nationally would have at least one 1,1-
dichloroethane detection. UCMR 3 Assessment Monitoring data showed no occurrence above
the one-half HRL or HRL thresholds.
Exhibit 5-15: 1,1-Dichloroethane Occurrence Data from UCMR 3 Assessment
Monitoring - Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections > MRL of 0.03 |jg/L
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Small Systems (serving < 10,000 people)
Groundwater
0.033
0.1
1.2
3.6
3.8
Surface Water
0.038
0.1
0.5
1.4
1.5
All Small Systems
0.033
0.1
0.6
3.4
3.8
Large Systems
serving 10,001 -100,000 people) — CENSUS
Groundwater
0.03
0.1
0.6
1.3
1.6
Surface Water
0.03
0.1
0.3
0.8
1.1
All Large Systems
0.03
0.1
0.5
1.2
1.6
Very Large Systems (serving > 100,000 people) — CENSUS
Groundwater
0.03
0.2
1.0
4.0
8.125
Surface Water
0.03
0.1
0.1
0.2
0.25
All Very Large
Systems
0.03
0.1
0.8
2.8
8.125
All Systems
All Water Systems
0.03
0.1
0.6
2.4
8.125
Source: USEPA, 2017b
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Exhibit 5-16: 1,1-Dichloroethane National Occurrence Measures Based on UCMR
3 Assessment Monitoring Data - Summary of Samples
Source Water Type
Total # of
Samples
Samples with
Detections
> MRL (0.03 |jg/L)
Samples with
Detections
> 1/2 HRL (500 |jg/L)
Samples with
Detections
> HRL (1,000 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Small Systems (serving < 10,000 people)
Groundwater
1,849
18
0.97%
0
0.00%
0
0.00%
Surface Water
1,417
17
1.20%
0
0.00%
0
0.00%
All Small Systems
3,266
35
1.07%
0
0.00%
0
0.00%
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
11,654
284
2.44%
0
0.00%
0
0.00%
Surface Water
14,808
218
1.47%
0
0.00%
0
0.00%
All Large Systems
26,462
502
1.90%
0
0.00%
0
0.00%
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
2,009
211
10.50%
0
0.00%
0
0.00%
Surface Water
5,111
87
1.70%
0
0.00%
0
0.00%
All Very Large Systems
7,120
298
4.19%
0
0.00%
0
0.00%
All Systems
All Water Systems
36,848
835
2.27%
0
0.00%
0
0.00%
Source: USEPA, 2017b
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Exhibit 5-17: 1,1-Dichloroethane National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data -
Summary of System and Population Served Data - All Detections
Source Water
Type
UCMR 3 Sample
Number With At Least One
Detection > MRL (0.03 ng/L)
Percent With At Least One
Detection > MRL (0.03 ng/L)
National Inventory1
National Estimate2
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Groundwater
527
1,498,845
9
26,294
1.71%
1.75%
55,700
38,730,597
951
679,000
Surface Water
272
1,250,215
6
34,695
2.21%
2.78%
9,728
20,007,917
215
555,000
All Small
Systems
799
2,749,060
15
60,989
1.88%
2.22%
65,428
58,738,514
1,170
1,230,000
Large Systems (serving 10,001 -100,000 people) — CENSUS
Groundwater
1,451
37,113,173
113
3,615,199
7.79%
9.74%
1,470
37,540,614
113
3,620,000
Surface Water
2,258
69,538,817
74
2,687,401
3.28%
3.86%
2,310
70,791,005
74
2,690,000
All Large
Systems
3,709
106,651,990
187
6,302,600
5.04%
5.91%
3,780
108,331,619
187
6,300,000
Very Large Systems (serving > 100,000 people) — CENSUS
Groundwater
68
16,355,951
15
3,897,374
22.06%
23.83%
68
16,355,951
15
3,900,000
Surface Water
340
115,158,260
27
10,806,045
7.94%
9.38%
343
120,785,622
27
10,800,000
All Very Large
Systems
408
131,514,211
42
14,703,419
10.29%
11.18%
411
137,141,573
42
14,700,000
All Systems
All Water
Systems
4,916
240,915,261
244
21,067,008
4.96%
8.74%
69,619
304,211,706
1,390
22,200,000
Source: USEPA, 2017b
1 The small system national inventory numbers for systems and population served by systems were derived from a freeze of the December 2010 Safe Drinking Water
Information System / Federal version (SDWIS/Fed) data. These counts are based on all community and non-transient non-community water systems that served 10,000
people or fewer. All large and very large systems were required to conduct UCMR 3 Assessment Monitoring; thus, the national inventory numbers for the large and very
large systems are based on the number of systems expected to complete UCMR 3 monitoring. SDWIS/Fed inventory data from 2010 were used for the UCMR 3 national
extrapolations as these data were consistent with the UCMR 3 inventory data at the timeframe of the UCMR 3 sample design.
2 National estimates for the small systems are generated by multiplying the UCMR 3 national statistical sample findings of system/population percentages and national
system/population inventory numbers for PWSs. National estimates for the large and very large systems are based directly on the UCMR 3 results, since this was a census.
Due to rounding, some calculations may appear to be slightly off.
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Adamson et al. (2017) conducted an independent analysis of UCMR 3 data. The study
focused on 1,4-dioxane, but also discussed other contaminants, including 1,1-dichloroethane
Some care should be taken when comparing the UCMR 3 occurrence findings from this study
with results presented elsewhere in this document. Note, for example, that Adamson et al. relied
on data from a May 2016 data pull, before all UCMR 3 results were reported and posted.
Adamson et al. (2017) calculated odds ratios to examine co-occurrence between 1,4-
dioxane and other UCMR 3 contaminants. The strongest relationship found was with 1,1-
dichloroethane. The study found that samples with 1,1-dichloroethane detections were 46 times
more likely to be associated with a 1,4-dioxane detection than samples without 1,1-
dichloroethane detections when adjusted for system size.
Unregulated Contaminant Monitoring (UCM) Data
In 1987, EPA initiated the UCM program, which collected contaminant occurrence data
from drinking water at PWSs. This program was implemented in two rounds. The first round of
UCM monitoring (UCM Round 1) generally extended from 1988 to 1992 and included
monitoring for 34 VOCs. The second round of UCM monitoring (UCM Round 2) generally
extended from 1993 to 1997 and included monitoring for 13 synthetic organic compounds
(SOCs) and sulfate in addition to the 34 VOCs from UCM Round 1 monitoring. All the
monitored contaminants were unregulated at the time of monitoring. A total of 38 states provided
contaminant occurrence data under UCM Round 1, and 34 states provided data under UCM
Round 2. Samples were analyzed for 1,1-dichloroethane under both UCM Round 1 and Round 2.
The contaminant occurrence data submitted under the UCM monitoring reflected neither
a census nor a statistically representative sample. Therefore, EPA assessed potential biases in the
data and developed a "national cross-section" separately from the UCM Round 1 and Round 2
data submitted by the states. The UCM Round 1 national cross-section of data from 24 states
consists of more than 3.3 million analytical results from approximately 22,000 systems. The
UCM Round 2 national cross-section of data from 20 states consists of more than 3.7 million
analytical results from approximately 27,000 systems. While EPA recognizes that some
limitations exist, the Agency believes that the national cross-sections are indicative of national
occurrence and provide a reasonable estimate of the overall distribution and the central tendency
of contaminant occurrence across the United States. For more details on the UCM Round 1 and 2
data and the occurrence estimation methodology, refer to USEPA (2001a), USEPA (2003b), and
USEPA (2008b).
Exhibit 5-18 through Exhibit 5-20 present a summary of the occurrence data from UCM
Rounds 1 and 2 for 1,1-dichloroethane. In the Round 1 cross-section states, 1,1-dichloroethane
was detected at 1.14 percent of PWSs, affecting 13.7 percent of the population served. Detected
concentrations ranged from 0.01 |ig/L to 500 |ig/L. In the Round 2 cross-section states,
1,1-dichloroethane was detected at 0.74 percent of PWSs, affecting 4.22 percent of the
population served. Detected concentrations ranged from 0.0013 |ig/L to 159 |ig/L. In both Round
1 and Round 2, more detections of 1,1-dichloroethane were found in groundwater systems than
surface water systems (though a larger proportion of surface water systems had detections). No
1,1-dichloroethane detections were greater than one-half the HRL or the HRL. Minimum
detected concentrations are reported in Exhibit 5-18; these minimum values may be indicative of
reporting levels used.
To calculate national extrapolations, the percent of systems (or population served)
estimated to exceed a specified threshold is multiplied by the total number of systems (or
5-29
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Final Regulatory Determination 4 Support Document - Ch 5, 1,1-Dichloroethane
January 2021
population served) in the nation. However, national extrapolations based on UCM data should be
interpreted with caution, because neither "all-states" data nor cross-section data constitute
statistically representative samples. See Chapter 2 for additional information on national
extrapolations. The results of national extrapolations are presented in Exhibit 5-20.
Because Round 1 and Round 2 involve different groups of states, conclusions about
temporal trends cannot necessarily be drawn from comparison of findings from the two Rounds.
(Temporal trends could, however, be inferred from state-level findings in the case of states with
findings from both Rounds.)
Exhibit 5-18: 1,1-Dichloroethane Occurrence Data from UCM Rounds 1 and 2 -
Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (|jg/L)
Minimum
Median
90th
99th Percentile
Maximum
UCM Round 1 - 24-State Cross-Section (1988-1992)
Groundwater
0.03
1.20
5.40
26.5
45.9
Surface Water
0.01
1.00
11.6
290
500
All Systems
0.01
1.20
5.60
27.0
500
UCM Round 1 - All States (1988-1992)
Groundwater
0.03
1.50
8.55
30.0
78
Surface Water
0.01
1.00
11.0
214
500
All Systems
0.01
1.49
8.78
30.4
500
UCM Round 2 - 20-State Cross-Section (1993-1997)
Groundwater
0.00126
1.10
3.79
24.7
159
Surface Water
0.1
0.65
3.90
13.5
17
All Systems
0.00126
1.00
3.80
19.5
159
UCM Round 2 - All States (1993-1997)
Groundwater
0.00126
1.10
3.72
23.3
159
Surface Water
0.0004
0.60
3.86
13.0
17
All Systems
0.0004
1.00
3.79
18.7
159
Source: USEPA, 2001b
Exhibit 5-19: 1,1-Dichloroethane Occurrence Data from UCM Rounds 1 and 2 -
Summary of Samples
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Samples with
Detections
> 1/2 HRL (500 |jg/L)
Samples with
Detections
> HRL (1,000 |jg/L)
Number
Percent
Number
Percent
Number
Percent
UCM Round 1 - 24-State Cross-Section (1988-1992)
Groundwater
59,699
656
1.10%
0
0.00%
0
0.00%
Surface Water
9,118
45
0.49%
0
0.00%
0
0.00%
All Samples
68,817
701
1.02%
0
0.00%
0
0.00%
5-30
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Final Regulatory Determination 4 Support Document - Ch 5, 1,1-Dichloroethane
January 2021
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Samples with
Detections
> 1/2 HRL (500 |jg/L)
Samples with
Detections
> HRL (1,000 |jg/L)
Number
Percent
Number
Percent
Number
Percent
UCM Round 1 - All States (1988-1992)
Groundwater
62,441
1126
1.80%
0
0.00%
0
0.00%
Surface Water
9,955
61
0.61%
0
0.00%
0
0.00%
All Samples
72,396
1,187
1.64%
0
0.00%
0
0.00%
UCM Round 2 - 20-State Cross-Section (1993-1997)
Groundwater
83,257
506
0.61%
0
0.00%
0
0.00%
Surface Water
15,802
86
0.54%
0
0.00%
0
0.00%
All Samples
99,059
592
0.60%
0
0.00%
0
0.00%
UCM Round 2 - All States (1993-1997)
Groundwater
93,735
529
0.56%
0
0.00%
0
0.00%
Surface Water
19,003
98
0.52%
0
0.00%
0
0.00%
All Samples
112,738
627
0.56%
0
0.00%
0
0.00%
Source: USEPA, 2001b
Exhibit 5-20: 1,1-Dichloroethane Occurrence Data from UCM Rounds 1 and 2 -
Summary of System and Population Served Data - All Detections
Source Water
Type
Total Number
Detections
Number
Percent
National
Extrapolation1
System
Population
System
Population
System
Population
System
Population
UCM Round 1 - 24-State Cross-Section, 1988-1992
Groundwater
18,758
57,587,562
204
9,713,217
1.09%
16.87%
646
16,600,000
Surface Water
1,876
43,760,057
29
3,490,759
1.55%
7.98%
85
13,500,000
All Systems2
20,483
96,338,790
233
13,203,976
1.14%
13.71%
738
36,600,000
UCM Round 1 - All States (1988-1992)
Groundwater
19,186
60,159,649
278
11,044,636
1.45%
18.36%
861
18,100,000
Surface Water
2,039
46,492,247
39
4,140,448
1.91%
8.91%
105
15,000,000
All Systems2
21,048
100,899,35
312
14,728,934
1.48%
14.60%
962
39,000,000
UCM Round 2 - 20-State Cross-Section, 1993-1997
Groundwater
22,114
25,979,938
148
945,578
0.67%
3.64%
398
3,590,000
Surface Water
2,694
45,312,483
36
2,062,662
1.34%
4.55%
74
7,690,000
All Systems2
24,808
71,292,421
184
3,008,240
0.74%
4.22%
481
11,300,000
5-31
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Final Regulatory Determination 4 Support Document - Ch 5, 1,1-Dichloroethane
January 2021
Source Water
Type
Total Number
Detections
Number
Percent
National
Extrapolation1
System
Population
System
Population
System
Population
System
Population
UCM Round 2 - All States (1993-1997)
Groundwater
25,207
31,431,369
162
1,382,069
0.64%
4.40%
382
4,330,000
Surface Water
3,062
53,767,694
40
2,219,895
1.31%
4.13%
72
6,970,000
All Systems2
28,269
85,199,063
202
3,601,964
0.71%
4.23%
464
11,300,000
Source: USEPA, 2001b
1 National extrapolations are generated by multiplying the UCM findings of system/population percentages and
national system/population inventory numbers for PWSs developed from EPA's Safe Drinking Water Information
System (SDWIS), the CWSS, and UCMR (see Chapter 2 for discussion). Because some water systems have more
than one source water type, extrapolations are generated separately for "Groundwater", "Surface Water", and "All
Systems"; thus, the number of extrapolated groundwater systems plus the number of extrapolated surface water
systems does not add up to the extrapolated "All Systems" numbers.
2 The number of groundwater systems plus the number of surface water systems is not equal to "All Systems"
because some water systems have more than one source water type.
Supplemental Data Sources
State Monitoring Data, 1999-2011
Because there is no available national database that receives and stores all relevant data
regarding the occurrence of regulated contaminants in public drinking water systems, EPA
conducts voluntary data requests from the states, territories, and tribes in support of national
occurrence assessments. These assessments are part of the Six-Year Review. Under the second
and third Six-Year Review (SYR2 and SYR3), a few states submitted PWS occurrence data for
unregulated contaminants along with the requested data on regulated contaminants. EPA was
able to supplement the data on unregulated contaminants by downloading additional publicly
available monitoring data from state websites. For SYR2, the result was a collection of
unregulated contaminant monitoring data from nine states and other entities, such as tribes,
territories, and EPA Regions. For SYR3, the dataset of unregulated contaminant monitoring data
included results from 14 states/entities. For both rounds of the Six-Year Review, these
unregulated data provide varying degrees of completeness in their coverage of the states/entities
and are not necessarily representative of occurrence in those states/entities. For more details on
the Six-Year Review Information Collection Request (ICR) Dataset for SYR2, refer to USEPA
(2009a). For more details on the SYR3 ICR Dataset, refer to EPA's SYR3 occurrence analysis
(USEPA, 2016).
Drinking water occurrence data for 1,1-dichloroethane were available from California,
Florida, Illinois, North Carolina, Ohio, EPA Region 9 Tribes, South Dakota, Texas, and
Wisconsin under SYR2 (1999-2005) and American Samoa, California, Florida, Michigan,
Navajo Nation, Pennsylvania, EPA Region 9 Tribes, Washington, and Wisconsin under SYR3
(2006-2011).3 Results are presented in Exhibit 5-21 through Exhibit 5-23. The exhibits do not
include estimates of population served because the 1,1-dichloroethane data submitted under
SYR2 and SYR3 represent only a small portion of all PWSs in each state. See USEPA (2009a)
and USEPA (2016) for the total number of systems that submitted SYR2 and SYR3 data,
3 Some states provided more than six years' worth of data to EPA in response to the SYR2 and SYR3 ICRs.
5-32
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Final Regulatory Determination 4 Support Document - Ch 5, 1,1-Dichloroethane
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respectively, from each state. Comprehensive information about methods used and reporting
levels is not available for this data set. Minimum detected concentrations are reported in Exhibit
5-21; these minimum values may be indicative of reporting levels used.
As noted above, the monitoring data from each state/entity are limited and not necessarily
representative of occurrence in the state/entity. The number of PWSs per state with 1,1-
dichloroethane data ranges from only 2 PWSs in Illinois SYR2 to 4,199 PWSs in the California
SYR2 data. Overall, detected concentrations ranged from 0.0001 |ig/L to 37 |ig/L. No states
reported detections of 1,1-dichloroethane greater than the HRL or one-half the HRL.
Exhibit 5-21: 1,1-Dichloroethane State Drinking Water Occurrence Data -
Summary of Detected Concentrations
State
Source Water
Type
(Sample Type)
Concentration Value of Detections (|jg/L)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Second Six-Year Review (SYR2)
California
(1995-2005)
Groundwater
(Raw)
0.5
0.7
1.5
4.9
5.2
Groundwater
(Finished)
0.5
0.9
1.4
3.2
3.5
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Raw)
0.5
0.8
1.9
3.7
20.4
Surface Water
(Finished)
0.58
0.58
0.58
0.58
0.58
Surface Water
(Not Provided)1
0.5
0.8
1.2
1.6
1.8
Not Provided2
(Raw)
ND
ND
ND
ND
ND
Not Provided3
ND
ND
ND
ND
ND
Total
0.5
0.80
1.6
3.62
20.4
Florida
(2004 - 2005)
Groundwater
(Not Provided)1
0.1
0.18
0.22
0.25
0.25
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
0.1
0.18
0.22
0.25
0.25
Illinois
(1998- 1999)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
N/A
N/A
N/A
N/A
N/A
Total
ND
ND
ND
ND
ND
North
Carolina
(1998-2005)
Groundwater
(Raw)
ND
ND
ND
ND
ND
Groundwater
(Finished)
0.5
1.55
4.58
8.17
8.8
Surface Water
(Finished)
0.5
0.60
1.40
1.58
1.6
Total
0.5
1.50
4.52
8.13
8.8
Ohio
(1998-2005)
Groundwater
(Not Provided)1
0.5
1.10
2.17
3.99
5.32
Surface Water
(Not Provided)1
1.3
1.70
1.86
1.90
1.9
5-33
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State
Source Water
Type
(Sample Type)
Concentration Value of Detections (|jg/L)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Total
0.5
1.20
2.14
3.91
5.32
EPA Region 9
Tribes
(1998-2005)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
South Dakota
(1990-2007)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
Texas
(1998-2005)
Groundwater
(Not Provided)1
1.2
2.10
3.28
4.47
4.6
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Not Provided3
ND
ND
ND
ND
ND
Total
1.2
2.10
3.28
4.47
4.6
Wisconsin
(1983-1999)
Groundwater
(Not Provided)1
0.061
0.59
2.30
12.0
15
Surface Water
(Not Provided)1
0.17
0.20
0.22
0.22
0.22
Total
0.061
0.58
2.26
12.0
15
Wisconsin
(2000-2005)
Groundwater
(Not Provided)1
0.19
0.80
11.0
16.3
17
Surface Water
(Not Provided)1
0.107
0.13
0.15
0.60
0.16
Total
0.107
0.80
11.0
16.3
17
Third Six-Year Review (SYR3)
American
Samoa
(2006-2011)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
N/A
N/A
N/A
N/A
N/A
Total
ND
ND
ND
ND
ND
California
(2006-2011)
Groundwater
(Raw)
0.09
0.70
1.3
2.4
5.6
Groundwater
(Finished)
0.1
0.81
1.4
2.1
5.8
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Raw)
0.5
0.95
2.1
4.6
6
Groundwater
(Finished)
0.55
1.2
2.1
2.4
2.4
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
0.09
0.78
1.5
3.0
6
Florida
(2006-2011)
Groundwater
(Raw)
1.2
1.2
1.2
1.2
1.2
Groundwater
(Not Provided)1
0.06
0.08
0.14
14.3
16.7
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
0.06
0.08
0.16
14.2
16.7
5-34
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January 2021
Source Water
Concentration Value of Detections (|jg/L)
State
Type
(Sample Type)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Groundwater
(Not Provided)1
0.5
0.7
1.7
3.6
3.8
Michigan
(2006-2011)
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Not Provided3
1.8
1.8
1.8
1.8
1.8
Total
0.5
0.7
1.8
3.6
3.8
Navajo Nation
(2007-2011)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
N/A
N/A
N/A
N/A
N/A
Total
ND
ND
ND
ND
ND
Groundwater
(Raw)
0.22
0.6
0.9
1.0
0.99
Pennsylvania
(2006-2011)
Groundwater
(Not Provided)1
0.1
0.9
4.4
8.3
11.5
Surface Water
(Raw)
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
0.1
0.8
4.3
7.8
11.5
EPA Region 9
Tribes
(2006-2011)
Groundwater
(Not Provided)1
0.08
0.08
0.08
0.08
0.08
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
0.08
0.08
0.08
0.08
0.08
Groundwater
(Raw)
0.6
0.6
0.6
0.6
0.6
Groundwater
(Finished)
0.5
0.8
1.2
1.2
1.2
Groundwater
(Not Provided)1
0.9
1.4
1.8
1.9
1.9
Surface Water
(Raw)
ND
ND
ND
ND
ND
Washington
(2006-2011)
Surface Water
(Finished)
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Not Provided2
(Raw)
ND
ND
ND
ND
ND
Not Provided2
(Finished)
ND
ND
ND
ND
ND
Not Provided3
ND
ND
ND
ND
ND
Total
0.5
0.9
1.2
1.2
1.2
5-35
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Final Regulatory Determination 4 Support Document - Ch 5, 1,1-Dichloroethane
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State
Source Water
Type
(Sample Type)
Concentration Value of Detections (|jg/L)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Wisconsin
(2006-2011)
Groundwater
(Not Provided)1
0.5
6.4
15.9
29.6
37
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Not Provided3
ND
ND
ND
ND
ND
Total
0.5
6.4
15.9
29.6
37
Source: Data provided to EPA by states and downloaded by EPA from state websites
ND = no detections in this category
N/A = not applicable (no data in this category)
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from groundwater or surface water.
3 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
Exhibit 5-22: 1,1-Dichloroethane State Drinking Water Occurrence Data -
Summary of Samples
State
Source Water
Type
(Sample Type)
Total # of
Samples
All Detections
Detec
> Vi
(500
tions
HRL
M9/L)
Detections
> HRL
(1,000 ua/L)
Number
Percent
Number
Percent
Number
Percent
Second Six-Year Review (SYR2)
California
(1995 -2005)
Groundwater
(Raw)
49,939
272
0.54%
0
0.00%
0
0.00%
Groundwater
(Finished)
6,189
83
1.34%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
106
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
35,963
643
1.79%
0
0.00%
0
0.00%
Surface Water
(Finished)
13,895
1
0.01%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
391
85
21.74%
0
0.00%
0
0.00%
Not Provided2
(Raw)
32
0
0.00%
0
0.00%
0
0.00%
Not Provided3
2
0
0.00%
0
0.00%
0
0.00%
Total
106,517
1,084
1.02%
0
0.00%
0
0.00%
Florida
(2004 -2005)
Groundwater
(Not Provided)1
753
21
2.79%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
3
0
0.00%
0
0.00%
0
0.00%
Total
756
21
2.78%
0
0.00%
0
0.00%
Illinois
(1998 - 1999)
Groundwater
(Not Provided)1
6
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Total
6
0
0.00%
0
0.00%
0
0.00%
North
Carolina
(1998 -2005)
Groundwater
(Raw)
163
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Finished)
17,564
112
0.64%
0
0.00%
0
0.00%
5-36
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State
Source Water
Type
(Sample Type)
Total # of
Samples
All Detections
Detec
> 1/>
(500
tions
HRL
M9/L)
Detections
> HRL
(1,000 ufl/L)
Number
Percent
Number
Percent
Number
Percent
Surface Water
(Finished)
2,110
3
0.14%
0
0.00%
0
0.00%
Total
19,837
115
0.58%
0
0.00%
0
0.00%
Ohio
(1998 -2005)
Groundwater
(Not Provided)1
8,324
54
0.65%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
1,026
3
0.29%
0
0.00%
0
0.00%
Total
9,350
57
0.61%
0
0.00%
0
0.00%
EPA Region
9 Tribes
(1998 -2005)
Groundwater
(Not Provided)1
1,097
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
87
0
0.00%
0
0.00%
0
0.00%
Total
1,184
0
0.00%
0
0.00%
0
0.00%
South
Dakota
(1990 -2007)
Groundwater
(Not Provided)1
1,057
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
53
0
0.00%
0
0.00%
0
0.00%
Total
1,110
0
0.00%
0
0.00%
0
0.00%
Texas
(1998 -2005)
Groundwater
(Not Provided)1
27,971
12
0.04%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
7,731
0
0.00%
0
0.00%
0
0.00%
Not Provided3
585
0
0.00%
0
0.00%
0
0.00%
Total
36,287
12
0.03%
0
0.00%
0
0.00%
Wisconsin
(1983-1999)
Groundwater
(Not Provided)1
14,618
226
1.55%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
435
2
0.46%
0
0.00%
0
0.00%
Total
15,053
228
1.51%
0
0.00%
0
0.00%
Wisconsin
(2000-2005)
Groundwater
(Not Provided)1
4,131
74
1.79%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
82
2
2.44%
0
0.00%
0
0.00%
Total
4,213
76
1.80%
0
0.00%
0
0.00%
Third Six-Year Review (SYR3)
American
Samoa
(2006-2011)
Groundwater
(Not Provided)1
67
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Total
67
0
0.00%
0
0.00%
0
0.00%
California
(2006-2011)
Groundwater
(Raw)
35,743
1,090
3.05%
0
0.00%
0
0.00%
Groundwater
(Finished)
31,457
1,744
5.54%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
152
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
15,206
404
2.66%
0
0.00%
0
0.00%
Surface Water
(Finished)
5,324
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
74
0
0.00%
0
0.00%
0
0.00%
Total
87,956
3,242
3.69%
0
0.00%
0
0.00%
5-37
-------
EPA - OGWDW Final Regulatory Determination 4 Support Document -Ch 5, 1,1 -Dichloroethane January 2021
State
Source Water
Type
(Sample Type)
Total # of
Samples
All Detections
Detec
> 1/>
(500
tions
HRL
M9/L)
Detections
> HRL
(1,000 ug/L)
Number
Percent
Number
Percent
Number
Percent
Florida
(2006-2011)
Groundwater
(Raw)
219
1
0.46%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
1,670
32
1.92%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
18
0
0.00%
0
0.00%
0
0.00%
Total
1,907
33
1.73%
0
0.00%
0
0.00%
Michigan
(2006-2011)
Groundwater
(Not Provided)1
8,166
61
0.98%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
665
0
0.00%
0
0.00%
0
0.00%
Not Provided3
39
2
0.00%
0
0.00%
0
0.00%
Total
8,870
63
0.90%
0
0.00%
0
0.00%
Navajo
Nation
(2007-2011)
Groundwater
(Not Provided)1
67
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Total
67
0
0.00%
0
0.00%
0
0.00%
Pennsylvania
(2006-2011)
Groundwater
(Raw)
44
11
25.00%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
1,354
81
5.98%
0
0.00%
0
0.00%
Surface Water
(Raw)
47
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
205
0
0.00%
0
0.00%
0
0.00%
Total
1,650
92
5.58%
0
0.00%
0
0.00%
EPA Region
9 Tribes
(2006-2011)
Groundwater
(Not Provided)1
396
1
0.25%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
27
0
0.00%
0
0.00%
0
0.00%
Total
423
1
0.24%
0
0.00%
0
0.00%
Washington
(2006-2011)
Groundwater
(Raw)
4,110
1
0.02%
0
0.00%
0
0.00%
Groundwater
(Finished)
2,954
8
0.27%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
1,016
2
0.20%
0
0.00%
0
0.00%
Surface Water
(Raw)
255
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Finished)
543
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
67
0
0.00%
0
0.00%
0
0.00%
Not Provided2
(Raw)
90
0
0.00%
0
0.00%
0
0.00%
Not Provided2
(Finished)
2
0
0.00%
0
0.00%
0
0.00%
Not Provided3
35
0
0.00%
0
0.00%
0
0.00%
Total
9,072
11
0.12%
0
0.00%
0
0.00%
5-38
-------
EPA - OGWDW
Final Regulatory Determination 4 Support Document - Ch 5, 1,1-Dichloroethane
January 2021
State
Source Water
Type
(Sample Type)
Total # of
Samples
All Detections
Detec
> 1/>
(500
tions
HRL
M9/L)
Detections
> HRL
(1,000 ua/L)
Number
Percent
Number
Percent
Number
Percent
Wisconsin
(2006-2011)
Groundwater
(Not Provided)1
790
5
0.63%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
29
0
0.00%
0
0.00%
0
0.00%
Not Provided3
6
0
0.00%
0
0.00%
0
0.00%
Total
825
5
0.61%
0
0.00%
0
0.00%
Source: Data provided to EPA by states and downloaded by EPA from state websites
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from groundwater or surface water.
3 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
Exhibit 5-23: 1,1-Dichloroethane State Drinking Water Occurrence Data -
Summary of Systems
State
Source Water
Type
(Sample Type)
Total # of
Systems
Systems with
Detections
Systems with
Detections
> 1/2 HRL (500 |jg/L)
Systems with
Detections
> HRL
(1,000 ua/L)
Number
Percent
Number
Percent
Number
Percent
Second Six-Year Review (SYR2)
Groundwater
(Raw)
3,253
19
0.58%
0
0.00%
0
0.00%
Groundwater
(Finished)
154
3
1.95%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
41
0
0.00%
0
0.00%
0
0.00%
California
(1995-2005)
Surface Water
(Raw)
511
12
2.35%
0
0.00%
0
0.00%
Surface Water
(Finished)
218
1
0.46%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
14
2
14.29%
0
0.00%
0
0.00%
Not Provided2
(Raw)
20
0
0.00%
0
0.00%
0
0.00%
Not Provided3
1
0
0.00%
0
0.00%
0
0.00%
Total
3,840
31
0.81%
0
0.00%
0
0.00%
Florida
(2004 - 2005)
Groundwater
(Not Provided)1
13
2
15.38%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
1
0
0.00%
0
0.00%
0
0.00%
Total
14
2
14.29%
0
0.00%
0
0.00%
Illinois
(1998- 1999)
Groundwater
(Not Provided)1
2
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Total
2
0
0.00%
0
0.00%
0
0.00%
North
Carolina
(1998-2005)
Groundwater
(Raw)
115
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Finished)
2,285
22
0.96%
0
0.00%
0
0.00%
Surface Water
(Finished)
202
2
0.99%
0
0.00%
0
0.00%
5-39
-------
EPA - OGWDW Final Regulatory Determination 4 Support Document -Ch 5, 1,1 -Dichloroethane January 2021
State
Source Water
Type
(Sample Type)
Total # of
Systems
Systems with
Detections
Systems with
Detections
> 1/2 HRL (500 |jg/L)
Systems with
Detections
> HRL
(1,000 ua/L)
Number
Percent
Number
Percent
Number
Percent
Total
2,493
24
0.96%
0
0.00%
0
0.00%
Ohio
(1998-2005)
Groundwater
(Not Provided)1
2,384
18
0.76%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
153
1
0.65%
0
0.00%
0
0.00%
Total
2,537
19
0.75%
0
0.00%
0
0.00%
EPA Region
9 Tribes
(1998-2005)
Groundwater
(Not Provided)1
270
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
16
0
0.00%
0
0.00%
0
0.00%
Total
286
0
0.00%
0
0.00%
0
0.00%
South
Dakota
(1990-2007)
Groundwater
(Not Provided)1
258
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
23
0
0.00%
0
0.00%
0
0.00%
Total
281
0
0.00%
0
0.00%
0
0.00%
Texas
(1998-2005)
Groundwater
(Not Provided)1
5,018
5
0.10%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
489
0
0.00%
0
0.00%
0
0.00%
Not Provided3
153
0
0.00%
0
0.00%
0
0.00%
Total
5,660
5
0.09%
0
0.00%
0
0.00%
Wisconsin
(1983-1999)
Groundwater
(Not Provided)1
1,898
39
2.05%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
32
1
3.13%
0
0.00%
0
0.00%
Total
1,930
40
2.07%
0
0.00%
0
0.00%
Wisconsin
(2000-2005)
Groundwater
(Not Provided)1
936
8
0.85%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
22
1
4.55%
0
0.00%
0
0.00%
Total
958
9
0.94%
0
0.00%
0
0.00%
Third Six-Year Review (SYR3)
American
Samoa
(2006-2011)
Groundwater
(Not Provided)1
11
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Total
11
0
0.00%
0
0.00%
0
0.00%
California
(2006-2011)
Groundwater
(Raw)
3,357
16
0.48%
0
0.00%
0
0.00%
Groundwater
(Finished)
149
9
6.04%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
60
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
467
5
1.07%
0
0.00%
0
0.00%
Surface Water
(Finished)
145
3
2.07%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
21
0
0.00%
0
0.00%
0
0.00%
Total
4,199
33
0.79%
0
0.00%
0
0.00%
5-40
-------
EPA - OGWDW Final Regulatory Determination 4 Support Document -Ch 5, 1,1 -Dichloroethane January 2021
State
Source Water
Type
(Sample Type)
Total # of
Systems
Systems with
Detections
Systems with
Detections
> 1/2 HRL (500 |jg/L)
Systems with
Detections
> HRL
(1,000 ug/L)
Number
Percent
Number
Percent
Number
Percent
Groundwater
(Raw)
3
1
33.33%
0
0.00%
0
0.00%
Florida
Groundwater
(Not Provided)1
53
2
3.77%
0
0.00%
0
0.00%
(2006-2011)
Surface Water
(Not Provided)1
1
0
0.00%
0
0.00%
0
0.00%
Total
57
3
5.26%
0
0.00%
0
0.00%
Michigan
(2006-2011)
Groundwater
(Not Provided)1
2,677
8
0.30%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
91
0
0.00%
0
0.00%
0
0.00%
Total
33
2
6.06%
0
0.00%
0
0.00%
Navajo
Nation
(2007-2011)
Groundwater
(Not Provided)1
46
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Total
46
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Raw)
10
2
20.00%
0
0.00%
0
0.00%
Pennsylvania
(2006-2011)
Groundwater
(Not Provided)1
209
13
6.22%
0
0.00%
0
0.00%
Surface Water
(Raw)
3
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
27
0
0.00%
0
0.00%
0
0.00%
Total
249
15
6.02%
0
0.00%
0
0.00%
EPA Region
9 Tribes
(2006-2011)
Groundwater
(Not Provided)1
189
1
0.54%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
14
0
0.00%
0
0.00%
0
0.00%
Total
203
1
0.51%
0
0.00%
0
0.00%
Groundwater
(Raw)
1,603
1
0.06%
0
0.00%
0
0.00%
Groundwater
(Finished)
1,071
3
0.28%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
579
2
0.35%
0
0.00%
0
0.00%
Washington
(2006-2011)
Surface Water
(Raw)
88
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Finished)
132
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
33
0
0.00%
0
0.00%
0
0.00%
Not Provided2
(Raw)
64
0
0.00%
0
0.00%
0
0.00%
Not Provided2
(Finished)
2
0
0.00%
0
0.00%
0
0.00%
Not Provided3
22
0
0.00%
0
0.00%
0
0.00%
5-41
-------
EPA - OGWDW
Final Regulatory Determination 4 Support Document - Ch 5, 1,1-Dichloroethane
January 2021
State
Source Water
Type
(Sample Type)
Total # of
Systems
Systems with
Detections
Systems with
Detections
> 1/2 HRL (500 |jg/L)
Systems with
Detections
> HRL
(1,000 ua/L)
Number
Percent
Number
Percent
Number
Percent
Total
3,594
6
0.17%
0
0.00%
0
0.00%
Wisconsin
(2006-2011)
Groundwater
(Not Provided)1
790
5
0.63%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
29
0
0.00%
0
0.00%
0
0.00%
Total
6
0
0.00%
0
0.00%
0
0.00%
Source: Data provided to EPA by states and downloaded by EPA from state websites
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from groundwater or surface water.
3 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
Community Water System Survey (CWSS)
The 2006 CWSS (USEPA, 2009b; USEPA, 2009c) gathered data on the financial and
operating characteristics of a random sample of CWSs nationwide, although all systems serving
more than 500,000 people (94 systems in 2006) received the survey. These 94 large systems
were asked questions about concentrations of unregulated contaminants in their raw and finished
water. Of these 94 systems, 58 systems (62 percent) responded to the survey, though not all of
these systems answered every question. EPA supplemented the data set by gathering additional
information about contaminant occurrence at the 94 systems from publicly available sources
(e.g., Consumer Confidence Reports (CCRs)).
In the 2006 CWSS, one of the 94 systems serving more than 500,000 people reported
monitoring data for 1,1-dichloroethane for a single sample. 1,1-Dichloroethane was not detected
in the single sample analyzed. Reporting levels were not specified in this survey.
United States Geological Survey (USGS') National Water Quality Assessment (NAWQA)
Source Water and Drinking Water Studies
Note that there may be some overlap between the NAWQA data assessment presented
earlier in the ambient water occurrence section and the summaries of NAWQA studies presented
below. The studies presented below include occurrence data from water sources for PWSs.
Water Quality in Public-Supply Wells (Toccalino et al., 2010), 1993-2007
To assess risks posed by contaminants in public-supply wells, water samples were
collected from source (untreated) groundwater from 932 public-supply wells located in parts of
40 NAWQA Study Units in 41 states (Toccalino et al., 2010). Each well was sampled once
between 1993 and 2007. Reporting levels were not specified in this study; however, the
minimum detected concentration (reported in Exhibit 5-24) may be indicative of reporting levels
used. Results from this study are presented in Exhibit 5-24 and Exhibit 5-25. 1,1-Dichloroethane
was detected in 64 (7.7 percent) of 832 samples. None of the 1,1-dichloroethane detections
exceeded the one-half HRL or HRL thresholds.
5-42
-------
EPA - OGWDW
Final Regulatory Determination 4 Support Document - Ch 5, 1,1-Dichloroethane
January 2021
Exhibit 5-24: 1,1-Dichloroethane Data from Public-Supply Wells (Toccalino et al.,
2010) - Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (|jg/L)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Groundwater Only
0.008
0.04
0.53
3.08
4.88
Source: Toccalino et al., 2010
Exhibit 5-25: 1,1-Dichloroethane Data from Public-Supply Wells (Toccalino et al.,
2010) - Summary of Samples
Source Water
Type
Number of
Samples
All Detections
Detections > Vi HRL
(500 |jg/L)
Detections > HRL
(1,000 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Groundwater Only
832
64
7.7%
0
0.00%
0
0.00%
Source: Toccalino et al., 2010
Organic Compounds in Source Water of Selected Community Water Systems (Hopple
et al., 2009 and Kingsbury et al., 2008), 2002-2005
As part of the NAWQA program, Hopple et al. (2009) and Kingsbury et al. (2008)
conducted studies to characterize anthropogenic organic compounds in waters of the United
States used as source waters for PWSs. Hopple et al. (2009) focused on groundwater and
Kingsbury et al. (2008) focused on surface water. In Phase 1 of the studies, geographically
diverse source water samples were collected between October 2002 and July 2005 from nine
CWSs served by streams and from 12 aquifers. In Phase 2, USGS collected source and finished
water samples at a subset of sites between June 2004 and September 2005. The reporting level
for 1,1-dichloroethane was 0.035 [j,g/L for groundwater and surface water samples in Phase 1 of
the studies but was not specified for Phase 2 of the studies. Results are presented in Exhibit 5-26
and Exhibit 5-27.
In Phase 1 of the studies, 1,1-dichloroethane was not detected in the 147 surface water
samples but was detected in 13 of the 221 (5.9 percent) groundwater samples with a maximum
detected concentration of 4.88 (J,g/L. In Phase 2 of the groundwater study, 1,1-dichloroethane
was detected in 9 of the 71 (13.0 percent) raw water samples and 6 of 71 (8.5 percent) finished
water samples. The maximum detected concentrations in raw and finished groundwater were
equal to 5.11 [j,g/L and 0.347 |ig/L, respectively. No surface water samples were analyzed for
1,1-dichloroethane in Phase 2. No results from Phase 1 or Phase 2 exceeded one-half the HRL or
the HRL.
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Exhibit 5-26: 1,1-Dichloroethane Data from Source Water (Hopple et al., 2009 and
Kingsbury et al., 2008) - Summary of Detections from Phase 1
Source Water Type
Number of
Samples
Percent of Detections
Maximum
Concentration
(ng/L)
All
> 0.1 |jg/L
Groundwater
221
5.9%
2.7%
4.88
Surface Water
147
0.0%
0.0%
ND
Source: Hopple et al., 2009 and Kingsbury et al., 2008
Exhibit 5-27: 1,1-Dichloroethane Data from Source Water (Hopple et al., 2009) -
Summary of Detections from Phase 2 - Groundwater
Source Water
Type
Number of Samples
Percent of Detections
Maximum Concentration
(ng/L)
Raw Water
Finished Water
Raw
Water
Finished Water
Raw Water
Finished Water
Groundwater
71
71
13.0%
8.5%
5.11
0.347
Source: Hopple et al., 2009 and Kingsbury et al., 2008
Volatile Organic Compounds in Drinking Water of Selected Community Water
Systems (Grady and Casey, 2001), 1993-1998
USGS compiled and analyzed occurrence data for VOCs in finished drinking water in 12
Northeast and Mid-Atlantic states (Connecticut, Delaware, Maine, Maryland, Massachusetts,
New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Virginia).
State agencies supplied USGS with VOC data collected during 1993 through 1998 for 20 percent
of the CWSs in the 12-state area, which were chosen to be representative in terms of geography,
water source, and system size. The 1,1-dichloroethane analysis included 1,666 CWSs in all 12
states. 1,1-Dichloroethane was detected in 440 of 12,786 samples (3.4 percent). Detected
concentrations ranged from 0.13 |ig/L to 24 |ig/L (Grady and Casey, 2001). All detected
concentrations were less than one-half the HRL and the HRL.
Water Quality in Domestic Wells (DeSimone, 2009), 1991-2004
Between 1991 and 2004, USGS assessed water quality from domestic wells across the
United States using NAWQA data (DeSimone, 2009). The program included the analysis of
major ions, trace elements, nutrients, radon, and organic compounds (pesticides and VOCs) at
approximately 2,100 domestic wells (private drinking water wells) across 48 states, covering 30
regional aquifers. In addition, USGS summarized data from wells sampled for NAWQA
agricultural land-use assessment studies to provide an indication of the potential effects of
agricultural land-use practices on the groundwater in the aquifers studied. Reporting thresholds
varied; the most common thresholds were between 0.033 [j,g/L and 0.2 (J,g/L. 1,1-Dichloroethane
was detected in 27 (1.19 percent) of the 2,269 samples from aquifer and agricultural land-use
studies.
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Volatile Organic Compounds (VOCs) in Domestic Wells (Moran et al., 2002; Rowe et
al., 2007), 1986-1999 and 1996-2002
As part of the NAWQA program, USGS studied the occurrence of VOCs in groundwater
from untreated rural self-supplied domestic wells between 1986 and 1999 (Moran et al., 2002).
These sources of drinking water are not subject to EPA drinking water regulations. Reporting
levels varied; results for most VOCs were reported at an assessment level of 0.2 (J,g/L. 1,1-
Dichloroethane was detected at that level in 5 of 1,926 samples (0.26 percent). Concentrations
ranged from 0.2 [j,g/L to 1.7 (J,g/L, with a median of 0.7 [j,g/L (Moran et al., 2002). All detected
concentrations were less than one-half the HRL and the HRL.
USGS also published the findings of a national assessment of VOCs in domestic wells
between 1996 and 2002 (Rowe et al., 2007). In this study, samples were analyzed for 55 VOCs.
1,1-Dichloroethane was detected in 27 of 1,207 well samples analyzed for this chemical (2.2
percent). The detected concentrations were not specified in this study.
Water Quality in Carbonate Aquifers (Lindsey et al., 2008), 1993-2005
As part of the NAWQA program, Lindsey et al. (2008) assessed the water quality in
carbonate aquifers, which account for 22 percent of the groundwater pumped by the country's
PWSs. From 1993 to 2005, the study analyzed 1,042 wells and springs across 12 aquifer systems
and 20 states for major ions, radon, nutrients, pesticides and VOCs. The study authors evaluated
occurrence of most VOCs at a uniform assessment level of 0.2 (J,g/L. 1,1-Dichloroethane was
detected in 16 of 793 samples (2.0 percent) with a maximum detected concentration of 0.58 |ag/L
which is less than one-half the HRL and the HRL.
Volatile Organic Compounds in the Nation's Groundwater andDrinking-Water Supply
Wells (Zogorski et al., 2006), 1985-2002
Zogorski et al. (2006) discuss the major findings and conclusions of the national
assessment of 55 VOCs in groundwater. VOC data from 2,401 domestic wells and 1,096 public
wells were available from aquifer studies, shallow groundwater studies, and a national source-
water survey to characterize the occurrence of VOCs. One VOC analysis per well was included
in the assessment.
In samples from aquifer studies, 1,1-dichloroethane was detected at levels > 0.2 [j,g/L in
30 (0.86 percent) of 3,496 samples, with a median detected concentration of 0.085 (J,g/L. In
samples from domestic wells, 1,1-dichloroethane was detected at levels > 0.2 [j,g/L in 7 (0.29
percent) of 2,400 samples, with a median detected concentration of 0.073 (J,g/L. In samples from
public wells, 1,1-dichloroethane was detected at levels > 0.2 [j,g/L in 22 (2.0 percent) of 1,096
samples, with a median detected concentration of 0.22 [j,g/L which is less than one-half the HRL
and the HRL.
5.4.3 Other Data
The Centers for Disease Control and Prevention (CDC) Fourth National Report on Human
Exposure to Environmental Chemicals, 2019 Updated Tables
Since 1999, the National Health and Nutrition Examination Survey (NHANES) has
examined the U.S. population annually and released the data in 2-year cycles. The survey is
based on a representative sample of the U.S. population based on age, gender, and race/ethnicity
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(CDC, 2019). The Fourth National Report on Human Exposure to Environmental Chemicals was
published in 2009 (CDC, 2009). The exposure data tables have been updated several times since
the original publication, most recently in 2019 (CDC, 2019). The 2019 updated tables include
data on whole blood concentrations (ng/mL) for 1,1-dichloroethane. The most recent data are
from the 2011-2012 reporting period. With a sample size of 2,736, the 95th percentile whole
blood concentration was below the limit of detection (LOD). The LOD was 0.01 ng/mL. Please
note that this value cannot be compared to the HRL because it represents a whole blood
concentration, not a drinking water concentration.
5.5 Analytical Methods
EPA has published four analytical methods that are available for the analysis of
1,1-dichloroethane in drinking water:
• EPA Method 502.2, Revision 2.1, Volatile Organic Compounds in Water by Purge
and Trap Capillary Column Gas Chromatography with Photoionization and
Electrolytic Conductivity Detectors in Series. Mean recoveries in reagent water range
from 97% to 100%, with Relative Standard Deviations (RSDs) of 2.3% to 5.7%
(USEPA, 1995a).
• EPA Method 524.2, Revision 4.1, Measurement of Purgeable Organic Compounds in
Water by Capillary Column Gas Chromatography/Mass Spectrometry. Mean
recoveries in reagent water range from 85% to 98%, with RSDs of 2.3% to 6.2%
(USEPA, 1995b).
• EPA Method 524.3, Version 1.0, Measurement of Purgeable Organic Compounds in
Water by Capillary Column Gas Chromatography/Mass Spectrometry. The Lowest
Concentration Minimum Reporting Level (LCMRL) generated by the laboratory that
developed the method is 0.064 |ig/L using Full Scan mode. Mean recoveries in
fortified reagent water and drinking water (from groundwater and surface water
sources) range from 95.2% to 103%, with RSDs of 2.5% to 8.7% using Full Scan
mode (USEPA, 2008c).
• EPA Method 524.4. Measurement of Purgeable Organic Compounds in Water by
Gas Chromatography/Mass Spectrometry Using Nitrogen Purge Gas. The LCMRL
generated by the laboratory that developed the method is 0.14 |ig/L using Full Scan
mode. The LCMRL generated by the laboratory that developed the method using
Selected Ion Monitoring (SIM) mode is 0.011 |ig/L. Mean recoveries in fortified
reagent water, groundwater, and surface water range from 86 to 102% with RSDs of
2.9 to 10%) using Full Scan mode (USEPA, 2013).
Laboratories participating in UCMR 3 were required to use EPA Method 524.3 in SIM
Mode and, as noted in Section 5.4.2, were required to report 1,1-dichloroethane values at or
above the EPA-defined MRL of 0.03 |ig/L (77 FR 26072; USEPA, 2012). The MRL was set
based on the capability of multiple laboratories at the time.
5.6 Treatment Technologies
EPA evaluates whether suitable treatment technologies are available prior to
promulgating a final National Primary Drinking Water Regulation (NPDWR).
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A preliminary review of the literature conducted in 2009 indicates that granular activated
carbon (GAC) may be effective for this contaminant. In addition, the following treatment
technologies have been investigated empirically for their applicability to this contaminant:
Conventional treatment
• Chlorine
Biological filtration (using granular activated carbon and microbes)
Powdered activated carbon
• Ozone
Air stripping/aeration
Air stripping/aeration (using steam)
Reverse osmosis
• Nanofiltration
• Ultrafiltration
Softening
• Ion Exchange
Ultraviolet irradiation
Ozone and ultraviolet irradiation
Hydrogen peroxide
Electrolysis with superoxide anode
The exact percentage removal a water system may achieve with a given technology will
be dependent upon a variety of factors, including source water quality and water system
characteristics.
5.7 References
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Hofmann, H.T., H. Birnstiel, and P. Jobst. 1971. On the inhalation toxicity of 1,1- and 1,2-
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Source Water of Nine Community Water Systems that Withdraw from Streams, 2002-05.
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Potential Human-Health Relevance of Volatile Organic Compounds in Drinking Water
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Rowe, G.L., K. Belitz, C.R. Demas, H.I. Essaid, R.J. Gilliom, P A. Hamilton, A.B. Hoos, C.J.
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Toccalino, P.L., J.E. Norman, and K.J. Hitt. 2010. Quality of Source Water from Public-Supply
Wells in the United States, 1993-2007. U.S. Geological Survey Scientific Investigations
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U.S. Environmental Protection Agency (USEPA). 1990. Integrated Risk Information System
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USEPA. 1995a. Method 502.2. Volatile Organic Compounds in Water by Purge and Trap
Capillary Column Gas Chromatography with Photoionization and Electrolytic
Conductivity Detectors in Series. Revision 2.1. EPA 600-R-95-131. National Exposure
Research Laboratory, Office of Research and Development.
USEPA. 1995b. Method 524.2. Measurement of Purgeable Organic Compounds in Water by
Capillary Column Gas Chromatography/Mass Spectrometry. Revision 4.1. National
Exposure Research Laboratory, Office of Research and Development. EPA 600-R-95-
131.
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Assessment. Office of Water. EPA 815-P-00-001.
USEPA. 2001b. UCM - State Rounds 1 and 2 (1988 - 1997) Occurrence Data. Available on the
Internet at: https://www.epa.gov/dwucmr/occurrence-data-unregulated-contaminant-
monitoring-rule# 12.
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Review of National Primary Drinking Water Regulations. Office of Water. EPA 815-R-
03-006.
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Protection Agency, Washington, DC. EPA-630-P-03-001F. Available on the Internet at:
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09/documents/cancer guidelines final 3-25-05.pdf. Accessed February 2015.
USEPA. 2006. Provisional Peer Reviewed Toxicity Values for 1,1-Dichloroethane (CASRN 75-
34-3). Superfund Health Risk Technical Support Center, National Center for
Environmental Assessment, Office of Research and Development, U.S. Environmental
Protection Agency, Cincinnati, OH. 9-27-2006. Available on the Internet at:
https://hhpprtv. ornl. gov/quickview/pprtv.php#pprtv ros.
USEPA. 2008a. Using the 2006 Inventory Update Reporting (IUR) Public Data: Background
Document. Office of Pollution Prevention and Toxics. December. Available on the
Internet at:
https://www.epa.gov/sites/production/files/documents/iurdbbackground O.pdf.
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USEPA. 2008b. The Analysis of Occurrence Data from the Unregulated Contaminant
Monitoring (UCM) Program and National Inorganics and Radionuclides Survey (NIRS)
in Support of Regulatory Determinations for the Second Drinking Water Contaminant
Candidate List. EPA 815-R-08-014.
USEPA. 2008c. Method 524.3. Measurement of Purgeable Organic Compounds in Water by
Capillary Column Gas Chromatography/Mass Spectrometry. Version 1.0. Technical
Support Center, Office of Ground Water and Drinking Water. EPA 815-B-09-009.
USEPA. 2009a. The Analysis of Regulated Contaminant Occurrence Data from Public Water
Systems in Support of the Second Six-Year Review of National Primary Drinking Water
Regulations. EPA-815-B-09-006. October 2009.
USEPA. 2009b. Community Water System Survey 2006 Volume I: Overview. EPA 815-R-09-
001. Available on the Internet at:
https://www.epa.gov/dwstandardsregulations/community-water-system-survey.
USEPA. 2009c. Community Water System Survey 2006 Volume II: Detailed Tables and Survey
Methodology. EPA 815-R-09-002. Available on the Internet at:
https://www.epa.gov/dwstandardsregulations/communitv-water-svstem-survev.
USEPA. 2011. Basic Questions and Answers for the Drinking Water Strategy Contaminant
Groups Effort. EPA 815-F-l 1-002. January 2011.
USEPA. 2012. Revisions to the Unregulated Contaminant Monitoring Regulation (UCMR 3) for
Public Water Systems. Federal Register 77(85): 26072, May 2, 2012.
USEPA. 2013. Method 524.4. Measurement of Purgeable Organic Compounds in Water by Gas
Chromatography/Mass Spectrometry Using Nitrogen Purge Gas. Technical Support
Center, Office of Ground Water and Drinking Water. EPA 815-R-13-002.
USEPA. 2014. Chemical Data Reporting. Fact Sheet: Basic Information. June. EPA 740-K-13-
001.
USEPA. 2016. The Analysis of Regulated Contaminant Occurrence Data from Public Water
Systems in Support of the Third Six-Year Review of National Primary Drinking Water
Regulations: Chemical Phase Rules and Radionuclides Rules. EPA 810-R-16-014.
December 2016.
USEPA. 2017a. TRI Explorer: Trends. Available on the Internet at:
https://enviro.epa.gov/triexplorer/tri release.trends. Accessed November 2017.
USEPA. 2017b. Third Unregulated Contaminant Monitoring Rule Dataset. Available on the
Internet at: https://www.epa.gov/dwucmr/occurrence-data-unregulated-contaminant-
monitoring-rule#3. Accessed January 2017.
USEPA. 2018. CDR Reporting Requirements. Available on the Internet at:
https://www.epa.gov/chemical-data-reporting/how-report-under-chemical-data-reporting.
Accessed December 2018.
USEPA. 2019a. CompTox Chemicals Dashboard, Searched by DSSTox Substance Id =
DTXSID1020437. Available on the Internet at:
https://comptox.epa. gov/dashboard/dsstoxdb/results?search=DTXSID1020437.
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January 2021
USEPA. 2019b. The Toxics Release Inventory (TRI) and Factors to Consider When Using TRI
Data. Available on the Internet at: https://www.epa.gov/toxics-release-inventory-tri-
program/factors-consider-when-using-toxics-release-inventory-data.
USEPA. 2019c. Occurrence Data from the Third Unregulated Contaminant Monitoring Rule
(UCMR 3). EPA 815-R-19-007.
United States Geological Survey (USGS). 2016. National Water Information System (NWIS)
Water-Quality Web Services, https://waterdata.usgs.gov/nwis. Last modified December
2016.
von Guerard, P. and W.B. Weiss. 1995 Water Quality of Storm Runoff and Comparison of
Procedures for Estimating Storm-Runoff Loads, Volume, Event-Mean Concentrations,
and the Mean Loadfor a Storm for Selected Properties and Constituents for Colorado
Springs, Southeastern Colorado, 1992. U.S. Geological Survey Water-Resources
Investigations Report 94-4194, 68 pp. Available on the Internet at:
http://pubs.usgs. gov/wri/1994/4194/report.pdf.
Water Quality Portal (WQP). 2017. Water Quality Portal Data Warehouse. Available on the
Internet at: https://www.waterqualitvdata.us/. Data Warehouse consulted December 2017.
WQP. 2018. Water Quality Portal Data Warehouse. Available on the Internet at:
https://www.waterqualitvdata.us/. Data Warehouse consulted September 2018.
World Health Organization (WHO). 2003. 1,1-Dichloroethane in Drinking Water. Background
Document for Development of WHO Guidelines for Drinking-Water Quality. Geneva,
Switzerland. Available on the Internet at:
http://www.who.int/water sanitation health/dwq/1. l-Dichloroethane.pdf.
Zogorski, J.S., J.M. Carter, T. Ivahnenko, W.W. Lapham, M.J. Moran, B.L. Rowe, P.J.
Squillace, and P.L. Toccalino. 2006. Volatile Organic Compounds in the Nation's
Ground Water and Drinking-Water Supply Wells. USGS Circular 1292. Available on the
Internet at: http://pubs.usgs.gov/circ/circl292/pdf/circularl292.pdf.
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Chapter 6:
Acetochlor
A chapter from:
Final Regulatory Determination 4 Support Document
EPA Report 815-R-21-001
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Contents
Contents 6-2
Exhibits 6-3
Abbreviations 6-4
6.1 Contaminant Background and Chemical and Physical Properties 6-6
6.2 Sources and Environmental Fate 6-7
6.2.1 Production, Use, and Release 6-7
6.2.2 Environmental Fate 6-9
6.3 Health Effects 6-11
6.3.1 Toxicokinetics 6-11
6.3.2 Available Health Effects Assessments 6-11
6.3.3 Health Effects 6-12
6.3.4 Basis of the HRL 6-14
6.3.5 Health Effects Data Gaps 6-15
6.4 Occurrence 6-15
6.4.1 Occurrence in Ambient Water 6-15
6.4.2 Occurrence in Drinking Water 6-23
6.4.3 Other Data 6-36
6.5 Analytical Methods 6-37
6.6 Treatment Technologies 6-37
6.7 References 6-38
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Exhibits
Exhibit 6-1: Chemical Structure of Acetochlor 6-6
Exhibit 6-2: Physical and Chemical Properties of Acetochlor 6-7
Exhibit 6-3: Estimated Annual Agricultural Use of Acetochlor, 2016 6-9
Exhibit 6-4: Health Effects Assessments for Acetochlor 6-12
Exhibit 6-5: Acetochlor NAWQA Data - Summary of Detected Concentrations 6-17
Exhibit 6-6: Acetochlor NAWQA Data - Summary of Samples 6-17
Exhibit 6-7: Acetochlor NAWQA Data - Summary of Sites 6-18
Exhibit 6-8: USGS National Synthesis Summary of NAWQA Monitoring of Acetochlor in
Streams, 1992-2001 6-20
Exhibit 6-9: USGS National Synthesis Summary of NAWQA Monitoring of Acetochlor in
Groundwater, 1992-2001 6-20
Exhibit 6-10: Acetochlor NWIS Data, 1991 - 2016 6-21
Exhibit 6-11: Acetochlor STORET Data - Summary of Detected Concentrations 6-22
Exhibit 6-12: Acetochlor STORET Data - Summary of Samples and Sites 6-22
Exhibit 6-13: Acetochlor STORET Data - Summary of States 6-23
Exhibit 6-14: Acetochlor Occurrence Data from UCMR 2 Screening Survey - Summary of
Samples, Sites, and Population Served 6-26
Exhibit 6-15: Acetochlor State Drinking Water Occurrence Data - Summary of Detected
Concentrations 6-27
Exhibit 6-16: Acetochlor State Drinking Water Occurrence - Summary of Samples 6-28
Exhibit 6-17: Acetochlor State Drinking Water Occurrence Data - Summary of Systems 6-29
Exhibit 6-18: Summary of Acetochlor PDP Data, 2001-2013 6-32
Exhibit 6-19: Acetochlor Data from Source Water (Hopple et al., 2009 and Kingsbury et al.,
2008) - Summary of Detections from Phase 1 6-34
Exhibit 6-20: Acetochlor Data from Source Water - Summary of Detections from Phase 2 -
Groundwater (Hopple et al., 2009) and Surface Water (Kingsbury et al., 2008) 6-34
Exhibit 6-21: Acetochlor Data from Public-Supply Wells (Toccalino et al., 2010) - Summary
of Detected Concentrations 6-34
Exhibit 6-22: Acetochlor Data from Public-Supply Wells (Toccalino et al., 2010) - Summary
of Samples 6-35
Exhibit 6-23: Wisconsin Groundwater Detections of Acetochlor 6-36
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Abbreviations
ALT
Alanine Aminotransferase
ARP
Acetochlor Registration Partnership
BW
Body Weight
CARC
Cancer Assessment Review Committee
CAS
Chemical Abstracts Service
CCL 4
Fourth Contaminant Candidate List
CCR
Consumer Confidence Report
CDC
Centers for Disease Control and Prevention
CDR
Chemical Data Reporting
cPAD
Chronic Population Adjusted Dose
CSF
Cancer Slope Factor
CWS
Community Water System
DWI
Drinking Water Intake
EPA
Environmental Protection Agency
ESA
Ethanesulfonic Acid
FQPA
Food Quality Protection Act
GC/MS
Gas Chromatography/Mass Spectrometry
HA
Health Advisory
HHRA
Human Health Risk Assessment
HRL
Health Reference Level
HSDB
Hazardous Substances Data Bank
ICR
Information Collection Request
IRIS
Integrated Risk Information System
IUR
Inventory Update Reporting
Kh
Henry's Law Constant
Koc
Octanol-Water Partitioning Coefficient
Kow
Organic Carbon Partitioning Coefficient
LCMRL
Lowest Concentration Minimum Reporting Level
LOAEL
Lowest Observed Adverse Effect Level
LOD
Limit of Detection
LOQ
Limit of Quantitation
LT-MDL
Long-Term Method Detection Level
MDL
Method Detection Limit
MRL
Minimum Reporting Level
NASQAN
National Stream Quality Accounting Network
NAWQA
National Water-Quality Assessment
NCFAP
National Center for Food and Agricultural Policy
ND
No Detection
NHANES
National Health and Nutrition Examination Survey
NIRS
National Inorganics and Radionuclides Survey
NOAEL
No Observed Adverse Effect Level
NPDWR
National Primary Drinking Water Regulation
NWIS
National Water Information System
OA
Oxanilic Acid
OPP
Office of Pesticide Programs
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OPPTS
Office of Prevention, Pesticide and Toxic Substances
OTC
Ornithine Carbamoyl Transferase
PA
Principal Aquifer
PDP
Pesticide Data Program
PMP
Pilot Monitoring Program
PWS
Public Water System
RfD
Reference Dose
RSC
Relative Source Contribution
RSD
Relative Standard Deviation
SIM
Selected Ion Monitoring
STORET
Storage and Retrieval Data System
SYR2
Second Six-Year Review
SYR3
Third Six-Year Review
TOC
Total Organic Carbon
TRED
Tolerance Reassessment Progress and Risk Management Decision
TRI
Toxics Release Inventory
TSH
Thyroid Stimulating Hormone
UCM
Unregulated Contaminant Monitoring
UC MR
Unregulated Contaminant Monitoring Rule
UC MR 1
First Unregulated Contaminant Monitoring Rule
UCMR2
Second Unregulated Contaminant Monitoring Rule
UCMR3
Third Unregulated Contaminant Monitoring Rule
USD A
United States Department of Agriculture
USGS
United States Geological Survey
UV
Ultraviolet
VOC
Volatile Organic Compound
WIDATCP
Wisconsin Department of Agriculture, Trade and Consumer Protection
WQP
Water Quality Portal
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Chapter 6: Acetochlor
The Environmental Protection Agency (EPA) is evaluating acetochlor as a candidate for
regulation as a drinking water contaminant under the fourth Contaminant Candidate List (CCL 4)
Regulatory Determinations process. Information on the CCL 4 process is found in Chapter 1.
Background on data sources used to evaluate CCL 4 chemicals is found in Chapter 2.
This chapter presents information and analyses specific to acetochlor, including
background information on the contaminant, information on contaminant sources and
environmental fate, an analysis of health effects, an analysis of occurrence in ambient and
drinking water, and information about the availability of analytical methods and treatment
technologies.
6.1 Contaminant Background and Chemical and Physical Properties
Acetochlor is a chloroacetanilide pesticide that is used as an herbicide for pre-emergence
control of weeds. It was first registered by EPA in 1994. It is registered for use on corn crops
(field corn and popcorn), but corn fields treated with acetochlor may later be rotated to grain
sorghum (milo), soybeans, wheat, and tobacco. There are no registered residential uses or
anticipated residential exposures to acetochlor (USEPA, 2018). In March of 2006, EPA's Office
of Prevention, Pesticide and Toxic Substances (OPPTS) released a Report of the Food Quality
Protection Act (FQPA) Tolerance Reassessment Progress and Risk Management Decision
(TRED) for acetochlor (USEPA, 2006a). Registration for acetochlor was expanded to include
sugar beets and peanuts (USEPA, 2006b; USEPA, 2013) and, in 2010, EPA approved the use of
acetochlor on cotton as a rotational crop (USEPA, 2010). Most recently, registration for
acetochlor was expanded to include alfalfa and related commodities (USEPA, 2018). Synonyms
for acetochlor include 2-chloro-2'-inethyl-6-ethyl-A'-ethoxyinethylacetanilide, according to the
Hazardous Substances Data Bank (HSDB, 2012).
Exhibit 6-1 presents the chemical structure of acetochlor. Physical and chemical
properties and other reference information are listed in Exhibit 6-2.
Exhibit 6-1: Chemical Structure of Acetochlor
Source: USEPA, 2019
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Exhibit 6-2: Physical and Chemical Properties of Acetochlor
Property
Data
Chemical Abstracts Service
(CAS) Registry Number
34256-82-1 (ChemlDPIus, 2018)
EPA Pesticide Chemical Code
121601 (HSDB, 2012)
Chemical Formula
C14H20CINO2 (ChemlDPIus, 2018)
Molecular Weight
269.77 g/mol (HSDB, 2012)
Color/Physical State
Thick, light amber to violet oily liquid (HSDB, 2012)
Boiling Point
378 deg C (RAIS, 2018)
Melting Point
10.6 deg C (HSDB, 2012)
Density
1.136 g/mL at 20 deg C (HSDB, 2012)
Freundlich Adsorption
Coefficient
4.339 L/kg (mean) (HSDB, 2012)
Vapor Pressure
1.67E-07 mm Hg at 20 deg C (HSDB, 2012)
Henry's Law Constant (Kh)
2.66E-10 atm-m3/mol at 25 deg C (HSDB, 2012)
Log Kow
4.14 (dimensionless) (HSDB, 2012)
Koc
98.5 - 335 L/kg (HSDB, 2012)
Solubility in Water
233 mg/L at 25 deg C (HSDB, 2012)
Other Solvents
Soluble in alcohol, acetone, toluene, carbon tetrachloride, ether, benzene,
chloroform and ethyl acetate (HSDB, 2012)
Conversion Factors
(at 25 deg C, 1 atm)
Not of sufficient volatility for conversion to be applicable
Note: Many of these properties are temperature dependent. Values are given for properties at 20-25 deg C unless
otherwise noted. Due to varying experimental conditions, and due to the variabilities associated with modeling, the
standard information sources may provide a range of values. Where more than one value was available from these
sources, one value was selected for this table based on best professional judgment.
6.2 Sources and Environmental Fate
6.2.1 Production, Use, and Release
Production data from EPA's Inventory Update Reporting (IUR) and Chemical Data
Reporting (CDR) programs are not available for acetochlor. No industrial release data for
acetochlor are available from EPA's Toxics Release Inventory (TRI). The list of chemicals for
which TRI reporting is required has never included acetochlor (USEPA, 2017a). Additional
information about these sources is provided in Chapter 2.
EPA Pesticide Industry Sales and Usage Report
EPA's Pesticide Industry Sales and Usage reports state that the amount of acetochlor
active ingredient used in the United States was between 31 and 36 million pounds in 1997;
between 30 and 35 million pounds in 1999, 2001 and 2003; between 26 and 31 million pounds in
2005; between 28 and 33 million pounds in 2007; between 23 and 33 million pounds in 2009;
and between 28 and 38 million pounds in 2012 (USEPA, 2004a; USEPA, 201 la; USEPA,
2017b).
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National Center for Food and Agricultural Policy (NCFAP) Pesticide Use Database
NCFAP maintains a national Pesticide Use Database, primarily for herbicides. Pesticide
use estimates are based on state-level commercial agriculture usage patterns and state-level crop
acreage. NCFAP lists uses of acetochlor on one crop (corn) totaling approximately 33 million
pounds of active ingredient per year in 35 states in 1997 (NCFAP, 2000).
United States Geological Survey (USGS) Pesticide Use Maps
USGS produces maps of annual pesticide use for over 200 compounds used in United
States crop production. The pesticide use maps show the average annual pesticide use intensity
expressed as average weight (in pounds) of a pesticide applied to each square mile of agricultural
land in a county. The USGS maps are created using data from NCFAP and county-level
information on harvested crop acreage from the Census of Agriculture.
Exhibit 6-3 shows the geographic distribution of estimated average annual acetochlor use
in the United States in 2016. A breakdown of use by crop from year to year is also included. The
breakdown of use shows that acetochlor is predominantly used on corn, but since 2011, there has
been an increase in use for cotton and soybeans. The map indicates that the greatest use of
acetochlor is in the Midwest.
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EPA - OGWDW Final Regulatory Determination 4 Support Document — Ch 6, Acetochlor January 2021
Exhibit 6-3: Estimated Annual Agricultural Use of Acetochlor, 2016
Estimated Agricultural Use lor Acetochlor, 2016 (Preliminary)
t I Ns estimated use
Use by Year and Crop
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20
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I-1-1— 1— 1— 1-i- i- (SI (M (SI (SI (SI (M (SI <\l (M (M (SI
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Final Regulatory Determination 4 Support Document - Ch 6, Acetochlor
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Enzymes involved in the initial step of glutathione conjugation include glutathione-S-
transferase and gamma-glutamyl transpeptidase (Thurman et al., 1996; Feng, 1991). Glutathione
conjugation of chloroacetanilides has been documented in soils, plants, and animals (Feng, 1991;
Rebich et al., 2004). In animals, an alternative metabolic pathway beginning with oxidation has
also been observed (Feng, 1991).
Microbial activity and herbicide degradation typically increase as temperature increases
(Aga and Thurman, 2001); empirical studies have confirmed this in the case of acetochlor
(Dictor et al., 2008; Dictor et al., 2003).
Moisture also affects glutathione conjugation and chloroacetanilide degradation rates
(Rebich et al., 2004; Aga and Thurman, 2001); empirical studies have confirmed that some
chloroacetanilides degrade faster in soils with higher moisture content (Aga and Thurman, 2001).
As discussed in Chapter 2, the measures used by EPA to assess mobility include (where
available) the organic carbon partitioning coefficient (Koc), log octanol-water partitioning
coefficient (log Kow), Henry's Law Constant (Kh), water solubility, and vapor pressure.
Acetochlor is directly released to the environment through its use as a pre-emergent or pre-plant
herbicide. The vapor pressure of acetochlor indicates that if it were released to the air, it would
be present in both the vapor and the particulate phases in the ambient atmosphere. Acetochlor
may be removed from the atmosphere physically, through wet and dry deposition (HSDB, 2012).
If released to soil, acetochlor is expected to have moderate to high mobility and marginal
leaching potential based on Koc values ranging from 98.5 to 335 L/kg. Volatilization of
acetochlor from moist soil surfaces or from water is not expected to be an important fate process
based on its Henry's Law Constant, nor is acetochlor expected to volatilize from dry soil surfaces
because of its vapor pressure (HSDB, 2012).
Estimated soil half-lives for acetochlor vary. Studies in several soil types (neoluvisols
and calcosols) indicate half-lives that range from 3.5 days to 14.9 days at 15-25 degrees C.
Another study indicated 6.7 percent and 23.9 percent mineralization (i.e., complete degradation
to carbon dioxide and water in contrast to simple conversion of the parent compound to
intermediate degradates) after 58 and 90 days in neoluvisols and calcosols (HSDB, 2012). Feng
(1991) measured an acetochlor half-life of seven days in soil. When incubated in anaerobic,
flooded soil, acetochlor had half-lives of 10 days under iron-reducing and sulfate-reducing
conditions, 15 days under iron-reducing conditions, and 16 days under methanogenic conditions.
Photolysis may be an important fate process in water: when acetochlor dissolved in a
water-methanol mixture was exposed to ultraviolet (UV) light, a half-life of 1.2 hours was
observed. The potential for acetochlor bioconcentration is high in aquatic organisms, provided
the compound is not metabolized by the organism (HSDB, 2012).
Chapter 2 presents scales used by EPA to informally rank chemical contaminants' likely
mobility (understood as their tendency to partition to water rather than other media) and
persistence as "high," "moderate," or "low" based on physical and chemical properties (see
Exhibit 2-2 and Exhibit 2-3). For acetochlor, a log Kow of 4.14 indicates a low likelihood of
partitioning to water, while a water solubility of 233 mg/L indicates a moderate likelihood of
partitioning to water. A Koc of 98.5 to 335 L/kg indicates a moderate to high likelihood of
partitioning to water and a Kh of 2.66E-10 atm-m3/mol indicates a high likelihood of partitioning
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to water. The aerobic biodegradation/biotransformation1 half-lives of 3.5 to 14.9 days indicate
low to moderate persistence under aerobic conditions, although other aerobic studies (half-lives
not available) suggest that aerobic degradation/transformation may occur more slowly. The
anaerobic half-lives under iron-reducing, sulfate-reducing and/or methanogenic conditions of 10
to 16 days indicate low to moderate persistence under anaerobic conditions.
6.3 Health Effects
6.3.1 Toxicokinetics
Acetochlor is readily absorbed (at least 70 percent) in rats after oral exposure and rapidly
eliminated (USEPA, 2006b; USEPA, 2018). Acetochlor is highly metabolized into many
metabolites and these metabolites are primarily excreted in the urine with additional significant
excretion through the feces and biliary system. Retention of acetochlor in tissues and carcasses is
negligible. Metabolism differs between rats and mice; glucuronidation and excretion of the
chloramide is the major metabolic route in mice. In rats, acetochlor is generally completely
metabolized, "with glutathione, mercapturic acid or glucuronide conjugation of //-dealkylated
acetochlor [representing] a major route of metabolism; sulphoxymethyl and cysteine conjugates
are also identified as excreted in feces" (USEPA, 2018). In rats, the major urine metabolite is a
mercapturic acid conjugate of A'-de-ethylated acetochlor and the major bile metabolite is the
glucuronide conjugate. Acetochlor is extensively biotransformed in rats and distributed
throughout the animal. Biotransformation in the rat includes glutathione conjugates and
enterohepatic recirculation leading to a cytotoxic benzoquinoneimine metabolite that binds to
cellular proteins and/or tissue macromolecules (USEPA, 2006b; USEPA, 2018). In rats, this
binding in nasal olfactory epithelium may be related to nasal tumor formation, as it does not
occur in mice where nasal tumors are absent (USEPA, 2006b; USEPA, 2018).
6.3.2 Available Health Effects Assessments
Exhibit 6-4 presents a summary of recent available health effects assessments for
acetochlor. As indicated by the bolded row, the 2018 Office of Pesticide Programs (OPP)
assessment (USEPA, 2018) was selected for use in the calculation of the Health Reference Level
(HRL). (See Section 6.3.4 below for details on that calculation and for information on additional
older EPA OPP health assessments.)
1 For the chloroacetanilides, formation of the ESA and OA derivatives is less a degradative process and more a
transformation process. Formation of the ESA and OA derivatives does not result in degradation of the parent
structure; rather, it creates a chemical derivative. Thus, the word "transformation" is more appropriate than the word
"degradation."
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Final Regulatory Determination 4 Support Document - Ch 6, Acetochlor
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Exhibit 6-4: Health Effects Assessments for Acetochlor
Health
Assessment
Assessment
Year
For the lifetime Health
Advisory (HA)
For the 10 s Cancer Risk
Concentration
Cancer
Descriptor
Reference
Dose(RfD)
(mg/kg/day)
Principal study
for RfD
Cancer
Slope Factor
(CSF)
(mg/kg/day)"1
Principal
study for
CSF
EPA OPP
Human
Health Risk
Assessment
(HHRA)
2018
0.02
ICI, Inc. 1988.
MRID No.
41565118; HED
Doc No. 008478
No Value
NA
Suggestive
Evidence of
Carcinogenic
Potential
EPA
Integrated
Risk
Information
System (IRIS)
1993
0.02
ICI, Inc. 1988.
MRID No.
41565118; HED
Doc No. 008478
No Value
NA
Not Assessed
6.3.3 Health Effects
Systemic (Non-cancer)
There are several subchronic studies (two in rats and two in dogs) and chronic studies
(three in rats which are combined chronic/carcinogenicity studies, two in dogs, and two in mice)
on the oral toxicity of acetochlor and a few subchronic studies on acetochlor ESA and OA
degradates in rats (one 4-week feeding study and one 90-day feeding study for each compound)
(USEPA, 2006b; USEPA, 2018). A description of the key results for the study on which the
reference dose (RfD) is based is provided below. Descriptions of non-cancer effects from
additional studies are also provided below.
The chronic RfD of 0.02 mg/kg/day for acetochlor is based on the no observed adverse
effect level (NOAEL) of 2 mg/kg/day observed in the 1-year oral study in beagle dogs (ICI, Inc.,
1988). The lowest observed adverse effect level (LOAEL) for this study was 10 mg/kg/day,
based on increased salivation, increased alanine aminotransferase (ALT), ornithine carbamyl
transferase and triglyceride levels; decreased blood glucose; and histopathological changes in the
kidneys, liver and testes of males (USEPA, 1993; USEPA, 2006b; USEPA, 2018).
Acetochlor has adverse effects on the liver, thyroid (secondary to the liver effects),
nervous system, kidney, lung, testes, and erythrocytes in rats and mice (USEPA, 2006b; USEPA,
2018). Effects on the nasal olfactory epithelium are observed only in rats. Acetochlor degradates
(ESA and OA) have thyroid effects, mainly in male rats (USEPA, 2006b). Acetochlor ESA and
OA in water are considered to be much less toxic than the parent compound (USEPA, 2006b).
In the 4-week range-finding study in rats, the NOAEL was approximately 370 mg/kg/day
for both acetochlor ESA (Lees, 2000a) and acetochlor OA (Williams, 2000a; USEPA, 2006b).
The LOAEL for both compounds was approximately 760 mg/kg/day (ranging from
approximately 740 to 770 mg/kg/day). The LOAEL for acetochlor ESA was based on decreased
body weights, decreased body weight gains, increased thyroid stimulating hormone (TSH), and
increased free T3 in males. The LOAEL for acetochlor OA was based on decreased TSH and
free T3 in both sexes and increased absolute and relative thyroid weights in males.
In the 90-day feeding studies in rats for acetochlor ESA (Lees, 2000b) and acetochlor OA
(Williams, 2000b), the NOAELs were 225.4 and 259.1 mg/kg/day for acetochlor ESA, and 230.2
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and 268 mg/kg/day for acetochlor OA, in males and females, respectively. The LOAEL for
acetochlor ESA was 919.4 and 1,073.2 mg/kg/day in males and females, respectively, based on
decreased body weights, decreased body weight gains, and decreased food consumption in both
sexes. The LOAEL for acetochlor OA was 955.2 and 1,082.7 mg/kg/day in males and females,
respectively, based on decreased body weights, decreased body weight gains and decreased
intake of food in both sexes.
Developmental/Reproductive
There are developmental studies in both rats and rabbits, and three two-generation
reproductive toxicity studies in rats for acetochlor. No teratogenicity was observed in these
studies, and it was concluded that rat offspring are not more susceptible to potential adverse
effects of acetochlor exposure than adults (USEPA, 2006a). However, acetochlor exposure was
associated with developmental toxicity in rats at maternally toxic doses (i.e., 400 to 600
mg/kg/day in rats) (USEPA, 2006b; USEPA, 2018). The following adverse effects were noted in
rat reproduction studies at maternally toxic doses: reduced fetal weights; increased early
resorptions and post-implantation loss; slightly reduced live litter size; and decreased
implantations. Rat reproductive studies also indicated a low incidence of nasal epithelial
hyperplasia in adult rats from the Fi generation (USEPA, 2006b; USEPA, 2018). There are no
reproductive or developmental studies for acetochlor ESA. In a single developmental study in
rats with acetochlor OA, there were no developmental toxicity effects observed except at the
maternal toxicity LOAEL of 1,000 mg/kg/day, which was based on mortality (USEPA, 2006b).
Cancer Data and Classification
Acetochlor is classified by the EPA Cancer Assessment Review Committee (CARC) as
having "Suggestive Evidence of Carcinogenic PotentiaF based on weak evidence for benign
lung tumors in male and female mice and histiocytic sarcomas in female mice, according to the
standards in EPA's final March 2005 Guideline for Carcinogen Risk Assessment (USEPA,
2005). In addition, nasal olfactory epithelial tumors and thyroid follicular cell tumors were
observed in rats (USEPA, 2006b; USEPA, 2018). According to a determination by EPA
(USEPA, 2013; USEPA, 2018), the chronic RfD of 0.02 mg/kg/day for acetochlor is protective
of both cancer and non-cancer effects; in this case, there is no requirement to also quantify
acetochlor cancer risk because the above-described chronic endpoint is anticipated to be
protective with respect to both potential non-cancer and cancer effects (USEPA, 2013; USEPA,
2018).
Acetochlor has been associated with an increase in nasal epithelial tumors in rat dietary
exposure studies (Ahmed and Seely, 1983; Ribelin, 1987; Naylor and Ribelin, 1986; and Virgo
and Broadmeadow, 1988). Two studies (Naylor and Ribelin, 1986; Virgo and Broadmeadow,
1988) have also observed increases in thyroid follicular cell adenomas in male rats. In
carcinogenicity studies in mice (Ahmed et al., 1983; Amyes, 1989), increases were observed in
lung tumors in both sexes and histiocytic sarcomas in females (Hardisty, 1997a; Hardisty, 1997b;
Hardisty, 1997c). Liver tumors have been noted in rats and mice at doses above the maximum
tolerated dose (USEPA, 2004b).
Although acetochlor has a threshold (non-mutagenic) mode of action for nasal and
thyroid tumors, no mode of action has been established for lung tumors or histiocytic sarcomas
in mice (USEPA, 2006b). Mutagenicity studies for acetochlor do not indicate significant
genotoxic potential. In bacterial mutagenicity studies, positive results have been observed only
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when cytotoxic doses were used. Acetochlor is clastogenic in in vitro assays, but not in in vivo
assays (USEPA, 2006b). Acetochlor ESA tested negative for mutagenicity in bacterial and
cultured mammalian cells and in an in vivo erythrocyte micronucleus test in mice (USEPA,
2006b). Acetochlor OA also tested negative in all the mutagenicity tests with the exception of a
single positive result in an in vitro mammalian cell (L5178Y mouse lymphoma cells) gene
mutation test (Clay, 2000). A significant increase in mutation frequency was noted at 2,000 and
2,650 |ig/mL in the presence of S9 in both trials. The results were significantly higher than the
historical control range and were predominantly small colony mutants.
Although there are no carcinogenicity studies on acetochlor ESA or acetochlor OA, EPA
(USEPA, 2006b) determined that neither acetochlor ESA or acetochlor OA is likely to be
carcinogenic, because they are "highly polar compounds showing poor to limited absorption, are
non-mutagenic, lack the reactive chlorine [of acetochlor], lack the capacity to form the
quinoneimine species that leads to nasal tumor formation, and do not demonstrate thyroid and
liver effects indicating potential to disrupt thyroid-pituitary homeostasis" (USEPA, 2006b).
Potentially Sensitive Groups/Lifestages
No biologically sensitive human subpopulations have been identified for acetochlor.
Developmental and reproductive toxicity studies do not indicate sensitivity to acetochlor toxicity
at early life stages.
6.3.4 Basis of the HRL
Exhibit 6-4 presents the most recent health assessments for acetochlor from EPA program
offices and other state, national, and international programs that have externally peer reviewed
and publicly available assessments. The most recent EPA assessment for acetochlor is the Office
of Pesticide Programs (OPP) Acetochlor Human Health Risk Assessment for Proposed New Use
on Alfalfa and Related Animal Commodities (U SEP A, 2018). The next most recent EPA OPP
assessment for acetochlor is the Human Health Benchmarks for Pesticides (USEPA, 2017c).
Also from OPP there is an Acetochlor Human Health Risk Assessment for Proposed New Uses of
Acetochlor on Sugar Beet and Peanut (USEPA, 2013) and a Tolerance Reassessment Progress
and Risk Management Decision (TRED) for Acetochlor (USEPA, 2006b). Finally, the only other
available health assessment for acetochlor is from the EPA IRIS program (USEPA, 1993). The
study used to derive the chronic oral RfD for each of these assessments is the one-year oral
chronic feeding study in beagle dogs (ICI, Inc., 1988). This study describes a NOAEL of 2
mg/kg/day and a LOAEL of 10 mg/kg/day, based on the critical effects of increased salivation;
increased alanine aminotransferase (ALT) and ornithine carbamoyl transferase (OTC) levels;
significant increases in triglyceride levels; decreased blood glucose levels; and histopathological
changes in the kidneys, liver and testes of male beagle dogs (USEPA, 2018; ICI, Inc., 1988). The
uncertainty factor applied was 100X (10X for intraspecies variation and 10X for interspecies
extrapolation) (USEPA, 1993). The EPA OPP RfD for acetochlor of 0.02 mg/kg/day (also
referred to as a chronic population adjusted dose, or cPAD), based on the NOAEL of 2.0
mg/kg/day from the chronic beagle dog study, is expected to be protective of both non-cancer
and cancer effects (USEPA, 2017c; USEPA, 2018).
The HRL for the non-cancer effects of acetochlor is 100 |ig/L, based on the EPA OPP
RfD for acetochlor of 0.02 mg/kg/day (USEPA, 2018). The HRL is generally calculated as
follows for chronic non-cancer risk and is finally rounded to one significant figure:
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BW
HRL = RfD* — *RSC
mq/kq 80 kq
HRL = 0.02 , * * 20%
day 2 ^
day
mg [ig
HRL = 0.128 -y-= 128 ^
L L
HRL = 100 — (rounded)
L
RfD = Reference Dose (mg/kg/day); toxicity value selected based on protocol hierarchy.
BW = Body weight (kg); based on adult default value of 80 kg (USEPA, 201 lb).
DWI = Drinking Water Intake (L/day); based on adult default value of 2.5 L/day
(USEPA, 2011b).
RSC = Relative Source Contribution, or the level of exposure believed to result from
drinking water when compared to other sources (e.g., food, ambient air), is 20 percent
when used for HRL derivation.
6.3.5 Health Effects Data Gaps
Further research in the area of adverse effects of acetochlor exposure in human
populations, including epidemiological studies and case studies, might be useful.
6.4 Occurrence
This section presents data on the occurrence of acetochlor in ambient water and drinking
water in the United States. As described in section 6.3, an HRL of 100 |ig/L was calculated for
acetochlor. HRLs are risk-derived concentrations against which EPA evaluates the occurrence
data to determine if contaminants occur at levels of potential public health concern. Occurrence
data from various sources presented below are analyzed with respect to the HRL and one-half the
HRL. When possible, estimates of the population exposed at concentrations above the HRL and
above one-half the HRL are presented.
For additional background information about data sources used to evaluate occurrence,
please refer to Chapter 2.
6.4.1 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the ambient sources of most drinking water. Contaminant
occurrence in ambient water provides information on the potential for contaminants to adversely
affect drinking water supplies. Occurrence data for acetochlor in ambient water are available
from the USGS National Water-Quality Assessment (NAWQA) program, the USGS National
Water Information System (NWIS) database, and EPA's legacy Storage and Retrieval Data
System (STORET) data available through the Water Quality Portal (WQP). Occurrence data for
acetochlor in ambient water are also available from several published studies summarized below.
Additional ambient water data collected in connection with finished drinking water data are
presented in Section 6.4.2.
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United States Geological Survey (USGS) National Water-Quality Assessment (NAWQA)
Ambient Water Analyses
USGS instituted the NAWQA program in 1991 to examine ambient water quality status
and trends in the United States. The NAWQA program generates high quality contaminant
occurrence and other water quality parameter data for significant watersheds and aquifers across
the nation. The program collects data on surface water and groundwater chemistry, hydrology,
land use, stream habitat, and aquatic life in parts or all of nearly all 50 States. The program is
designed to apply nationally consistent methods to provide a uniform basis for contaminant
occurrence comparisons and assessments among study basins across the country and over time.
The occurrence assessments can also serve to facilitate interpretation of natural and
anthropogenic factors affecting national water quality. For more detailed information on the
NAWQA program design and implementation, refer to Leahy and Thompson (1994) and
Hamilton et al. (2004).
The process of sampling, analysis, and data synthesis is divided into cycles of
approximately ten years: Cycle 1 covered 1991-2001, Cycle 2 covered 2002-2012, and Cycle 3 is
ongoing and covers 2013-2023. Study units are sampled and analyzed on a staggered schedule
within each cycle. Each NAWQA cycle begins with a two-year startup phase for planning and
retroactive analysis, followed by a three-year intensive data collection phase, and finally a five-
year phase for analyzing the data, developing reports, and continuing a low level of monitoring
(fa, 2012).
During Cycle 1 (1991-2001), 51 study units were sampled. Data were gathered from
6,307 wells from 272 groundwater networks or clusters and from 6,400 sampling points at 505
surface water monitoring sites, primarily rivers and streams but also some lakes and reservoirs
(NRC, 2002). In Cycle 2 (2002-2012), the number of study units was reduced from 51 to 42.
(NRC, 2012). Long-term stream monitoring was established at 113 streams representing 8 major
river basins. Long-term groundwater monitoring was established at sites representing 20
principal aquifers with more than 10 to 15 years of consistent monitoring data available (Rowe et
al., 2013).
Sampling for Cycle 3 is currently underway (2013-2023). Surface water monitoring will
be conducted at 313 sites, increased from 113 sites in Cycle 2 (Rowe et al., 2013). Groundwater
assessments in Cycle 3 will be designed to evaluate status and trends at the principal aquifer
(PA) and national scales. Assessments are planned in 24 PAs that account for the majority of
current and future national groundwater use for drinking water. Data available through 2017 are
presented in this report. For more details on the Cycle 3 sampling design, refer to Rowe et al.
(2010; 2013).
EPA's analysis of the NAWQA data is a simple, non-parametric occurrence analysis that
provides summary statistics to characterize contaminant occurrence. EPA calculated detection
frequencies as the percentage of samples and the percentage of sites with at least one detection,
without any censoring or weighting. (A detection is an analytical result equal to or greater than
the reporting level.) EPA reported the minimum and maximum detected concentrations and
calculated other descriptive statistics including the median, 90th percentile, and 99th percentile
concentrations (based only on samples with detections). Reporting levels varied over time during
the NAWQA program. In some cases, therefore, the minimum concentration reported as a
detection could be lower than the highest reporting level.
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Exhibit 6-5 through Exhibit 6-7 present analyses of the acetochlor NAWQA data,
downloaded from the Water Quality Portal in September 2018 (WQP, 2018). Acetochlor was
detected in all three cycles. Acetochlor was detected in approximately 13 percent of samples in
Cycle 1, 20 percent of samples in Cycle 2, and 23 percent of samples in Cycle 3. (Some sites
were sampled in more than one cycle.) Fewer than 10 percent of sites in all Cycles had detections
of acetochlor. In Cycle 2 and Cycle 3, just one detection of acetochlor was greater than the HRL.
No detections in Cycle 1 were greater than the HRL. The median concentrations based on
detections were 0.037 |ig/L, 0.024 |ig/L, and 0.041 |ig/L in Cycle 1, Cycle 2, and Cycle 3,
respectively. Although maximum acetochlor values in NAWQA Cycle 2 and Cycle 3 monitoring
exceeded the HRL (215 |ig/L in 2004 and 137 |ig/L in 2013), 90th percentile levels of acetochlor
were less than 1 |ig/L, well below the HRL. As noted above, NAWQA data are ambient water
data, not finished drinking water data.
Note that there may be some overlap between the NAWQA data assessment presented
here and summaries of individual NAWQA studies presented below.
Exhibit 6-5: Acetochlor NAWQA Data - Summary of Detected Concentrations
Site Type
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Cycle 1 (1991 -2001)
Groundwater
0.003
0.023
0.085
0.113
0.114
Surface Water
0.001
0.037
0.836
7.30
30.4
All Sites
0.001
0.037
0.827
7.29
30.4
Cycle 2 (2002-2012)
Groundwater
0.003
0.009
0.018
0.037
0.042
Surface Water
0.001
0.024
0.304
4.22
215
All Sites
0.001
0.024
0.302
4.21
215
Cycle 3 (2013-2017)
Groundwater
0.0008
0.007
0.017
0.203
0.224
Surface Water
0.00055
0.041
0.443
2.33
137
All Sites
0.00055
0.041
0.442
2.32
137
Source: WQP, 2018
Exhibit 6-6: Acetochlor NAWQA Data - Summary of Samples
Site Type
No. of
Samples
Detection Frequency
(detections are results > reporting level)
No. of
Samples
with
Detections
%
Samples
with
Detections
No. of
Samples
with
Detections
> 1/2 HRL
%
Samples
with
Detections
> 1/2 HRL
No. of
Samples
with
Detections
> HRL
%
Samples
with
Detections
> HRL
Cycle 1 (1991 -2001)
Groundwater
5,132
15
0.29%
0
0.00%
0
0.00%
Surface Water
13,445
2,432
18.09%
0
0.00%
0
0.00%
All Sites
18,577
2,447
13.17%
0
0.00%
0
0.00%
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Detection Frequency
(detections are results > reporting level)
Site Type
No. of
Samples
No. of
Samples
with
Detections
%
Samples
with
Detections
No. of
Samples
with
Detections
> 1/2 HRL
%
Samples
with
Detections
> 1/2 HRL
No. of
Samples
with
Detections
> HRL
%
Samples
with
Detections
> HRL
Cycle 2 (2002-2012)
Groundwater
6,648
25
0.38%
0
0.00%
0
0.00%
Surface Water
13,644
4,107
30.10%
4
0.03%
1
0.01%
All Sites
20,292
4,132
20.36%
4
0.02%
1
0.005%
Cycle 3 (2013-2017)
Groundwater
1,515
10
0.66%
0
0.00%
0
0.00%
Surface Water
8,948
2,400
26.82%
2
0.02%
1
0.01%
All Sites
10,463
2,410
23.03%
2
0.02%
1
0.01%
Source: WQP, 2018
Exhibit 6-7: Acetochlor NAWQA Data - Summary of Sites
Site Type
No. of
Sites
Detection Frequency
(detections are results > reporting level)
No. of
Sites with
Detections
% Sites
with
Detections
No. of
Sites with
Detections
> 1/2 HRL
% Sites
with
Detections
> 1/2 HRL
No. of
Sites with
Detections
> HRL
% Sites
with
Detections
> HRL
Cycle 1 (1991 -2001)
Groundwater
4,354
15
0.34%
0
0.00%
0
0.00%
Surface Water
1,500
298
19.87%
0
0.00%
0
0.00%
All Sites
5,854
313
5.35%
0
0.00%
0
0.00%
Cycle 2 (2002-2012)
Groundwater
4,096
23
0.56%
0
0.00%
0
0.00%
Surface Water
414
133
32.13%
2
0.48%
1
0.24%
All Sites
4,510
156
3.46%
2
0.04%
1
0.02%
Cycle 3 (2013-2017)
Groundwater
1,439
10
0.69%
0
0.00%
0
0.00%
Surface Water
316
160
50.63%
2
0.63%
1
0.32%
All Sites
1,755
170
9.69%
2
0.11%
1
0.06%
Source: WQP, 2018
NA WQA Pesticide National Synthesis Project, 1992-2001
Through a series of National Synthesis efforts, the USGS NAWQA prepares
comprehensive analyses of data on topics of particular concern. These National Synthesis
assessments aggregate NAWQA contaminant occurrence and water quality parameter data from
individual study units and other sources to provide a national overview. The NAWQA Pesticide
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National Synthesis Project is a national-scale assessment of the occurrence and behavior of
pesticides in streams and groundwater of the United States and the potential for pesticides to
adversely affect drinking water supplies or aquatic ecosystems.
Results from the Pesticide National Synthesis analysis (1992-2001), based on Cycle 1
data from NAWQA study units, are posted on the NAWQA Pesticide National Synthesis website
(Gilliom et al., 2007).2 Data for surface water and groundwater are presented separately, and
results in each category are subdivided by land use category. Land use categories include
agricultural, urban, mixed (deeper aquifers of regional extent in the case of groundwater), and
undeveloped. The Pesticide National Synthesis analysis is a first step toward the USGS goals of
describing the occurrence of pesticides in relation to different land use and land management
patterns and developing a deeper understanding of the relationship between spatial occurrence of
contaminants and their fate, transport, persistence, and mobility characteristics.
The surface water summary data presented in the Pesticide National Synthesis (Gilliom et
al., 2007) only includes stream data. Sampling data from a single one-year period, generally the
year with the most complete data, were used to represent each stream site. Sites with few data or
significant gaps were excluded from the analysis. NAWQA stream sites were sampled repeatedly
throughout the year to capture and characterize seasonal and hydrologic variability. Groundwater
data reported in the Pesticide National Synthesis only include samples from wells; data from
springs and agricultural tile drains were not included. In the National Synthesis analysis (Gilliom
et al., 2007), USGS uses a single sample to represent each well, generally the earliest sample
with complete data for the full suite of analytes.
Over the course of Cycle 1, some NAWQA analytical methods were improved or
changed. Hence, detection thresholds varied over time for some compounds. USGS used the
maximum Long-Term Method Detection Level (LT-MDL) for each analyte as a uniform
reporting threshold. The maximum LT-MDL for acetochlor was 0.003 |ig/L (Gilliom et al.,
2007). Acetochlor was an analyte in the Pesticide National Synthesis Project.
In NAWQA stream samples (Exhibit 6-8), acetochlor was found at frequencies ranging
from 0 percent of samples in undeveloped areas to 3.38 percent of samples in urban areas, 8.31
percent of samples in mixed land use settings, and 29.87 percent of samples in agricultural
settings. The 95th percentile concentrations were less than the maximum LT-MDL in
undeveloped and urban settings. In mixed and agricultural settings, the 95th percentile
concentrations were 0.020 |ig/L and 0.130 |ig/L, respectively. The highest surface water
concentration, 10.600 |ig/L, was detected at an agricultural site.
2 All the National-Synthesis Assessments (Pesticides, Nutrients, Volatile Organic Compounds (VOCs), Ecology,
and Trace Elements) were evaluated using Cycle 1 data. A major focus of NAWQA's Cycle 2 is on regional
assessments of groundwater quality conditions and trends. No companion Cycle 2 National Synthesis Assessment
reports were released.
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Exhibit 6-8: USGS National Synthesis Summary of NAWQA Monitoring of
Acetochlor in Streams, 1992-2001
Land Use Type
Number of
Sites
Number of
Samples
Detection
Frequency
(Samples)
Concentration Values (of detections, in |jg/L)
Median
95th Percentile
Maximum
Agricultural
54
1,113
29.87%
ND
0.130
10.600
Mixed
51
1,034
8.31%
ND
0.020
1.660
Undeveloped
7
121
0.00%
ND
ND
ND
Urban
23
549
3.38%
ND
ND
0.311
Source: Gilliom et al., 2007
ND = not detected (concentration is less than the maximum LT-MDL and is expected to be less than any higher
percentile concentration shown in the table)
In NAWQA groundwater samples (Exhibit 6-9), acetochlor was found at frequencies
ranging from no detections in any samples from undeveloped areas to 0.1 percent of samples in
mixed land use settings, 0.5 percent of samples in agricultural settings, and 0.6 percent of
samples in urban areas. The 95th percentile concentrations were less than the maximum LT-MDL
in all land use settings. The highest groundwater concentration, 0.122 |ig/L, was found at an
urban site.
Exhibit 6-9: USGS National Synthesis Summary of NAWQA Monitoring of
Acetochlor in Groundwater, 1992-2001
Land Use Type
Number of
Wells
Detection
Frequency
Concentration Values (of detections, in |jg/L)
Median
95th Percentile
Maximum
Agricultural
920
0.5%
ND
ND
0.0568
Mixed
2,266
0.1%
ND
ND
0.114
Undeveloped
23
0.0%
ND
ND
ND
Urban
667
0.6%
ND
ND
0.122
Source: Gilliom et al., 2007
ND = not detected (concentration is less than the maximum LT-MDL and is expected to be less than any higher
percentile concentration shown in the table)
National Water Information System (NWIS) Data
The National Water Information System (NWIS) is the Nation's principal repository of
water resources data USGS collects from more than 1.5 million sites (USGS, 2016). NWIS-Web
is the general online interface to the USGS NWIS database. Discrete water-sample and time-
series data are available from sites in all 50 States, including 5 million water samples with 90
million water-quality results. All USGS water quality and flow data are stored in NWIS,
including site characteristics, streamflow, groundwater level, precipitation, and chemical
analyses of water, sediment, and biological media, though not all parameters are available for
every site. NWIS houses the NAWQA data and includes other USGS data from unspecified
projects. NWIS contains many more samples at many more sites than the NAWQA Program.
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Although NWIS is comprised of primarily ambient water data, some finished drinking water data
are included as well. This section presents analyses of non-NAWQA data in NWIS, downloaded
from the Water Quality Portal in December 2017 (WQP, 2017). These data do not overlap with
the results presented in Exhibit 6-5 through Exhibit 6-7.
The results of the non-NAWQA NWIS acetochlor analyses are presented in Exhibit 6-10.
Acetochlor was detected in approximately 14 percent of samples (4,701 out of 32,957 samples)
and at approximately 8 percent of sites (845 out of 11,050 sites). The median concentration
based on detections was equal to 0.044 |ig/L. (Note that the NWIS data are presented as
downloaded; potential outliers were not evaluated or excluded from the analysis.)
Exhibit 6-10: Acetochlor NWIS Data, 1991 - 2016
Site Type
Detection Frequency
(detections are results > reporting level)
Concentration Values
(of detections, in |jg/L)
No. of
Samples
No. of
Samples
with
Detections
No. of
Sites
No. of
Sites with
Detections
Minimum1
Median
90th
Percentile
99th
Percentile
Maximum
Groundwater
15,407
367
8,118
169
0.001
0.050
0.223
0.826
3
Surface
Water
17,514
4,330
2,938
675
0
0.044
0.684
5.56
19.2
Finished
Water
36
4
22
1
0.005
0.009
0.010
0.010
0.01
All Sites2
32,957
4,701
11,050
845
0
0.044
0.620
5.27
19.2
Source: WQP, 2017
1A minimum value of zero may represent a detection that was entered into the database as a non-numerical value
(e.g., "Present").
2 The number of groundwater sites plus the number of surface water sites and finished water sites is not equal to "All
Sites" because some sites may have been listed with more than one source water type in the data.
Storage and Retrieval (STORE!) Data / Water Quality Portal (WQP)
From its launch in 1999 until it was decommissioned in June 2018, EPA's STORET Data
Warehouse was collaboratively populated with raw biological, chemical, and physical data from
surface water and groundwater sampling by federal, state and local agencies, Native American
tribes, volunteer groups, academics, and others. Legacy STORET data are accessible through the
Water Quality Portal (WQP): https://www.waterqualitvdata.us/portal/.
STORET data are from monitoring locations in all 50 states as well as multiple territories
and jurisdictions of the United States. Most data are from ambient waters, but in some cases
finished drinking water data are included as well. STORET's data quality limitations include
variations in the extent of national coverage and data completeness from parameter to parameter.
Data may have been collected as part of targeted, rather than randomized, monitoring.
This section presents analyses of STORET data, downloaded from the WQP in December
2017 (WQP, 2017). EPA reviewed STORET groundwater data from wells and surface water data
from lakes, rivers/streams, and reservoirs (WQP, 2017). The WQP also included public water
system (PWS) data from four states (Indiana, Missouri, Ohio, and Washington); EPA reviewed
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these as well (WQP, 2017). It is unclear if the PWS data were collected prior to or subsequent to
treatment.
The results of the STORET analysis for acetochlor are presented in Exhibit 6-11 through
Exhibit 6-13. These acetochlor samples were collected between 1994 and 2016. Of the 4,585
sites sampled, 2,287 (49.9 percent) reported detections of acetochlor. Detected concentrations
ranged as high as 243 |ig/L. The 90th percentile concentration of detections was equal to 1.00
|ig/L. The minimum detected concentration may be indicative of the reporting levels used. (A
minimum value of zero, on the other hand, could represent a detection that was entered into the
database as a non-numerical value (e.g., "Present").)
Exhibit 6-11: Acetochlor STORET Data - Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (|jg/L)
Minimum1
Median
90th Percentile
Maximum
Groundwater
0
0
0.06
243.335
Surface Water
0
0.10
1.01
117.8023709
Total
0
0.10
1.00
243.335
PWS
0
0.26
0.416
0.52
Source: WQP, 2017
1A minimum value of zero may represent a detection that was entered into the database as a non-numerical value
(e.g., "Present").
Exhibit 6-12: Acetochlor STORET Data - Summary of Samples and Sites
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Total
Number
of Sites
Sites with Detections
Number
Percent
Number
Percent
Groundwater
5,692
998
17.53%
1,021
301
29.48%
Surface Water
54,692
23,450
42.88%
3,564
1,986
55.72%
Total
60,384
24,448
40.49%
4,585
2,287
49.88%
PWS
2
2
100.00%
2
2
100.00%
Source: WQP, 2017
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Exhibit 6-13: Acetochlor STORET Data - Summary of States
Source Water
Type
Total
Number of
States
States with Detections
Number
Percent
Groundwater
9
5
55.56%
Surface Water
25
16
64.00%
Total1
25
16
64.00%
PWS
2
2
100.00%
Source: WQP, 2017
1 The number of states with groundwater data plus the number of
states with surface water data may not equal the "Total" number
of states providing data because some states provided both
groundwater and surface water data.
Acetochlor Registration Partnership (ARP), 1995-2001
As part of an agreement with EPA to maintain the registration of acetochlor and monitor
its environmental behavior, the ARP (an organization representing registrants Monsanto and
Dow AgroSciences) conducted an extensive monitoring program. From 1995-2001, ARP
compiled and analyzed water samples collected through the state groundwater and surface water
monitoring programs (de Guzman et al., 2005; Hackett et al., 2005). Some results from these
monitoring programs are reported in the Cumulative Risk from Chloroacetanilide Pesticides
(USEPA, 2006c). Samples were collected in seven states (Illinois, Indiana, Iowa, Kansas,
Minnesota, Nebraska, and Wisconsin) and were analyzed for acetochlor and other corn
herbicides.
At a limit of detection (LOD) of 0.03 |ig/L, acetochlor was detected in 25 (13.7 percent)
of 182 groundwater monitoring wells (de Guzman et al., 2005). The maximum detected
concentration of acetochlor in the groundwater monitoring wells was equal to 4.35 |ig/L. In
surface water, acetochlor was detected in 18.8 percent of the finished drinking water samples
collected from 175 surface water monitoring sites. The maximum detected concentration was
equal to 18.2 |ig/L and the maximum annualized mean concentration of acetochlor was equal to
1.43 |ig/L (Hackett et al., 2005).
Additional Ambient Water Studies
As part of the USGS NAWQA Program and/or the National Stream Quality Accounting
Network (NASQAN), trends in the concentrations of 11 commonly occurring pesticides in the
Corn Belt of the United States were assessed at up to 31 stream sites for two time periods: 1996
through 2002 and 2000 through 2006. The 31 stream sites analyzed in this study are a subset of
201 sites that were sampled (Sullivan et al., 2009). Trends for acetochlor concentrations were
mixed, as acetochlor use in the Corn Belt stayed relatively constant over the period of record.
Acetochlor detection rates were variable at a reporting limit of 0.003 |ig/L, ranging from 25
percent to 92 percent of the samples in the 1996-2002 time period and from 30 percent to 100
percent of samples in the 2000-2006 time period.
6.4.2 Occurrence in Drinking Water
Data sources reviewed by the Agency for information on contaminant occurrence in
drinking water included: EPA's first, second, and third Unregulated Contaminant Monitoring
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Rules (UCMR 1, UCMR 2, UCMR 3); Rounds 1 and 2 of the Agency's Unregulated
Contaminant Monitoring (UCM) program that preceded the Unregulated Contaminant
Monitoring Rule (UCMR); EPA's Information Collection Rule; EPA's National Inorganics and
Radionuclides Survey (NIRS); and a range of others as discussed in Chapter 2. Among the
sources reviewed, the following had data and information on acetochlor occurrence in drinking
water. These data and information are discussed in this section.
EPA's First Unregulated Contaminant Monitoring Rule (UCMR 1).
EPA's Second Unregulated Contaminant Monitoring Rule (UCMR 2).
State drinking water monitoring programs.
Consumer Confidence Reports (CCRs) from PWSs.
United States Department of Agriculture (USD A) Pesticide Data Program (PDP).
• USGS Pilot Monitoring Program (PMP).
USGS source water and drinking water studies.
Additional studies from the literature.
Note that there may be some overlap, as sources with different purposes and audiences
may have reported the same underlying data. UCMR 1 and UCMR 2 are national data sources.
Other data sources profiled in this section are considered "supplemental" sources. Also note that
the presentation of NWIS and STORET results in the ambient water section, above, includes
some miscellaneous finished water data and/or data from PWSs.
Primary Data Sources
First Unregulated Contaminant Monitoring Rule (UCMR 1), 2001-2003
UCMR 1 required the collection of data to support nationally representative estimates of
contaminant occurrence in PWSs. UCMR 1 monitoring occurred primarily from 2001 to 2003
and required surface water systems to monitor quarterly and groundwater systems to monitor
semi-annually. There were two tiers of monitoring: Assessment Monitoring for contaminants
with commonly used analytical method technologies, and Screening Survey monitoring for
contaminants that require specialized analytical method technologies not in wide or common use.
All large PWSs serving more than 10,000 people, plus a statistically representative
national sample of 800 small PWSs (serving 10,000 people or fewer) were required to conduct
UCMR 1 Assessment Monitoring. For the UCMR 1 Screening Survey, EPA required monitoring
by a representative sample of 120 large and 180 small PWSs. Monitoring by each PWS was
required during a 12-month period between January 2001 and December 2003. Due to the small
sample size, contaminant occurrence estimates based on data from UCMR 1 Screening Survey
are statistically less robust than those based on data from the UCMR 1 Assessment Monitoring.
(For more details on all aspects of UCMR 1, refer to USEPA, 1999; USEPA, 2001; USEPA,
2008.)
A total of 33,778 finished water acetochlor samples were collected under the UCMR 1
Assessment Monitoring (3,251 small system samples and 30,527 large system samples). There
were no detections of acetochlor from any of the small or large systems that sampled under
UCMR 1. The Minimum Reporting Level (MRL) for acetochlor was 2 |ig/L.
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The design of UCMR 1 permits estimation of national occurrence. However, since no
detections of acetochlor were observed among 33,778 samples from 3,869 systems serving 226
million people in the UCMR 1 Assessment Monitoring program, acetochlor occurrence in the
nation's small and large systems is likely to be negligible based on these results.
Second Unregulated Contaminant Monitoring Rule (UCMR 2), 2008-2010
UCMR 2 monitoring was conducted from 2008 to 2010 and was designed to provide
nationally representative contaminant occurrence data. UCMR 2 required surface water systems
to monitor quarterly and groundwater systems to monitor semi-annually. There were two tiers of
monitoring: Assessment Monitoring for contaminants with commonly used analytical method
technologies, and Screening Survey monitoring for contaminants that require specialized
analytical method technologies not in wide or common use at the time of the study.
All PWSs serving more than 10,000 people, plus a statistically representative national
sample of 800 PWSs serving 10,000 people or fewer, were required to conduct Assessment
Monitoring during a 12-month period between January 2008 and December 2010. For the
Screening Survey, monitoring was required by all very large PWSs, 320 representative large
PWSs, and 480 representative small PWSs, during a 12-month period between January 2008 and
December 2010. See USEPA (2007) and USEPA (2014) for more information on the UCMR 2
program, including study design and data analysis.
The design of UCMR 2 permits estimation of national occurrence. To calculate national
extrapolations, the percent of systems (or population served) estimated to exceed a specified
threshold in a given category can be multiplied by the total number of systems (or population
served) in the nation in that category. In the analysis of UCMR 2 Screening Survey data, the
extrapolation methodology is applied only to small and large systems, not very large systems.
Because all systems serving more than 100,000 people were required to participate in the UCMR
2 Screening Survey monitoring, national estimates of occurrence in this size category do not
require extrapolation. Rather, survey census figures are used. Total national occurrence is
estimated by summing the extrapolated or census figures from all three size categories. See
Chapter 2 for additional information on national extrapolations.
Acetochlor was monitored under the UCMR 2 Screening Survey; results are presented in
Exhibit 6-14. The MRL used for acetochlor was 2 (J,g/L (72 FR 367; USEPA, 2007). A total of
11,193 acetochlor samples were collected from 1,198 systems. There were no detections of
acetochlor from systems sampled under UCMR 2, suggesting that nationwide occurrence of
acetochlor is likely to be low or negligible. Since there were not any detections of acetochlor in
the systems sampled under UCMR 2, additional tables summarizing these results are not
presented.
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Exhibit 6-14: Acetochlor Occurrence Data from UCMR 2 Screening Survey -
Summary of Samples, Sites, and Population Served
Source Water Type
Total Number of
Samples
Total Number of
Systems
Population Served
by Systems
Small Systems (serving < 10,000 people)
Groundwater
788
240
548,364
Surface Water
1,040
240
660,557
All Small Systems
1,828
480
1,208,921
Large Systems (serving 10,001 -100,000 people)
Groundwater
1,392
151
6,584,184
Surface Water
1,178
169
7,444,830
All Large Systems
2,570
320
14,029,015
Very Large Systems (serving > 100,000 people) — CENSUS
Groundwater
2,010
63
17,269,919
Surface Water
4,785
335
124,711,765
All Very Large Systems
6,795
398
141,981,684
All Systems
All Water Systems
11,193
1,198
157,219,620
Source: USEPA, 2012a
Supplemental Data Sources
State Monitoring Data, 1999-2011
Because there is no available national database that receives and stores all relevant data
regarding the occurrence of regulated contaminants in public drinking water systems, EPA
conducts voluntary data requests from the states, territories, and tribes in support of national
occurrence assessments. These assessments are part of the Six-Year Review. Under the second
and third Six-Year Review (SYR2 and SYR3), a few states submitted PWS occurrence data for
unregulated contaminants along with the requested data on regulated contaminants. EPA was
able to supplement the data on unregulated contaminants by downloading additional publicly
available monitoring data from state websites. For SYR2, the result was a collection of
unregulated contaminant monitoring data from nine states and other entities, such as tribes,
territories, and EPA Regions. For SYR3, the dataset of unregulated contaminant monitoring data
included results from 14 states/entities. For both rounds of the Six-Year Review, these
unregulated data provide varying degrees of completeness in their coverage of the states/entities
and are not necessarily representative of occurrence in those states/entities. For more details on
the Six-Year Review Information Collection Request (ICR) Dataset for SYR2, refer to USEPA
(2009). For more details on the SYR3 ICR Dataset, refer to EPA's SYR3 occurrence analysis
(USEPA, 2016).
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Drinking water occurrence data for acetochlor were available from California, Illinois,
and Ohio3 under SYR2 (1999-2005) and California and Michigan under SYR3 (2006-2011).4
Results are presented in Exhibit 6-15 through Exhibit 6-17. The exhibits do not include estimates
of population served because the acetochlor data submitted under SYR2 and SYR3 represent
only a small portion of all PWSs in each state. See USEPA (2009) and USEPA (2016) for the
total number of systems that submitted SYR2 and SYR3 data, respectively, from each state.
Comprehensive information about methods used and reporting levels is not available for this data
set. Minimum detected concentrations are reported in Exhibit 6-15; these minimum values may
be indicative of reporting levels used.
As noted above, the monitoring data from each state/entity are limited and not necessarily
representative of occurrence in the state/entity. The number of PWSs per state with acetochlor
data ranges from only 26 PWSs in Ohio SYR2 to 2,482 PWSs in the Michigan SYR3 data.
Overall, detected concentrations ranged from 1.6 |ig/L to 1.8 |ig/L. Illinois was the only state
with detections of acetochlor in the SYR2 data (2 detections at 1 PWS, 0.11 percent of PWSs
with data). Neither of the detections from the Illinois SYR2 data were greater than the acetochlor
HRL or one-half the HRL.
Exhibit 6-15: Acetochlor State Drinking Water Occurrence Data - Summary of
Detected Concentrations
State
(Date Range)
Source Water
Type
(Sample Type)
Concentration Value of Detections (|jg/L)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Acetochlor - Second Six-Year Review (SYR2)
California
(2001-2005)
Groundwater
(Raw)
ND
ND
ND
ND
ND
Groundwater
(Finished)
ND
ND
ND
ND
ND
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Raw)
ND
ND
ND
ND
ND
Surface Water
(Finished)
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
Illinois
(1999-2005)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
1.6
1.7
1.8
1.8
1.8
Total
1.6
1.7
1.8
1.8
1.8
Ohio
(2000-2005)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
3 Additional PWS monitoring data from the State of Ohio are reported in STORET. See Section 6.4.1 for more
details.
4 Some states provided more than six years' worth of data to EPA in response to the SYR2 and SYR3 ICRs.
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State
(Date Range)
Source Water
Type
(Sample Type)
Concentration Value of Detections (|jg/L)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Acetochlor - Third Six-Year Review (SYR3)
California
(2006-2011)
Groundwater
(Raw)
ND
ND
ND
ND
ND
Groundwater
(Finished)
ND
ND
ND
ND
ND
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Raw)
ND
ND
ND
ND
ND
Surface Water
(Finished)
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
Michigan
(2006-2011)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Not Provided2
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
Source: Data provided to EPA by states and downloaded by EPA from state websites
ND = no detections in this category
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
Exhibit 6-16: Acetochlor State Drinking Water Occurrence - Summary of Samples
State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Samples
Samples with
Detections
Samples with
Detections
> 1/2 HRL (50 Mg/L)
Samplt
Detectio
(100
2S with
is > HRL
M9/L)
Number
Percent
Number
Percent
Number
Percent
Acetochlor - Second Six-Year Review (SYR2
California
(2001-2005)
Groundwater
(Raw)
2,064
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Finished)
68
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
6
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
946
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Finished)
204
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
1
0
0.00%
0
0.00%
0
0.00%
Total
3,289
0
0.00%
0
0.00%
0
0.00%
Illinois
(1999-2005)
Groundwater
(Not Provided)1
2,553
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
813
2
0.25%
0
0.00%
0
0.00%
Total
3,366
2
0.06%
0
0.00%
0
0.00%
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State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Samples
Samples with
Detections
Samples with
Detections
> 1/2 HRL (50 Mg/L)
Samplt
Detectio
(100
2S with
is > HRL
M9/L)
Number
Percent
Number
Percent
Number
Percent
Ohio
(2000-2005)
Groundwater
(Not Provided)1
73
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
107
0
0.00%
0
0.00%
0
0.00%
Total
180
0
0.00%
0
0.00%
0
0.00%
Acetochlor - Third Six-Year Review (SYR3)
California
(2006-2011)
Groundwater
(Raw)
378
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Finished)
114
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
11
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
325
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Finished)
54
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
2
0
0.00%
0
0.00%
0
0.00%
Total
884
0
0.00%
0
0.00%
0
0.00%
Michigan
(2006-2011)
Groundwater
(Not Provided)1
4,562
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
256
0
0.00%
0
0.00%
0
0.00%
Not Provided2
25
0
0.00%
0
0.00%
0
0.00%
Total
4,843
0
0.00%
0
0.00%
0
0.00%
Source: Data provided to EPA by states and downloaded by EPA from state websites
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
Exhibit 6-17: Acetochlor State Drinking Water Occurrence Data - Summary of
Systems
State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections
> 1/2 HRL (50 |jg/L)
Systen
Detectio
(100
is with
is > HRL
M9/L)
Number
Percent
Number
Percent
Number
Percent
Acetochlor - Second Six-Year Review (SYR2
California
(2001-2005)
Groundwater
(Raw)
162
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Finished)
19
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
5
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
82
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Finished)
48
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
1
0
0.00%
0
0.00%
0
0.00%
Total
268
0
0.00%
0
0.00%
0
0.00%
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State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections
> 1/2 HRL (50 Mg/L)
Systen
Detectio
(100
is with
is > HRL
M9/L)
Number
Percent
Number
Percent
Number
Percent
Illinois
(1999-2005)
Groundwater
(Not Provided)1
777
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
120
1
0.83%
0
0.00%
0
0.00%
Total
897
1
0.11%
0
0.00%
0
0.00%
Ohio
(2000-2005)
Groundwater
(Not Provided)1
21
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
5
0
0.00%
0
0.00%
0
0.00%
Total
26
0
0.00%
0
0.00%
0
0.00%
Acetochlor - Third Six-Year Review (SYR3)
California
(2006-2011)
Groundwater
(Raw)
82
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Finished)
8
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
3
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
49
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Finished)
16
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
2
0
0.00%
0
0.00%
0
0.00%
Total
141
0
0.00%
0
0.00%
0
0.00%
Michigan
(2006-2011)
Groundwater
(Not Provided)1
2,400
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
60
0
0.00%
0
0.00%
0
0.00%
Not Provided2
22
0
0.00%
0
0.00%
0
0.00%
Total
2,482
0
0.00%
0
0.00%
0
0.00%
Source: Data provided to EPA by states and downloaded by EPA from state websites
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
Water Systems' Consumer Confidence Reports (CCRs), 2010-2018
CCRs are annual water quality reports that community water systems (CWSs) are
required to provide to their customers. These reports summarize information on water sources,
detected contaminants, and system compliance with EPA drinking water standards; they may
also include general educational material. Under the CCR Rule (40 CFR Subpart O), CWSs with
15 or more connections or serving at least 25 year-round residents must prepare and distribute a
CCR to all billing units or service connections every year. Systems serving 100,000 or more
residents are also required to post their current CCRs on a publicly accessible Internet site. EPA
reviewed CCRs published by the 22 systems that serve over 1 million customers (as identified in
the UCMR 3 database) for unregulated contaminant occurrence information for the years 2010
through 2015. Data on acetochlor were available from CCRs prepared by three CWSs: two
systems from New York (Suffolk County and New York City) and one system in Pennsylvania
(the City of Philadelphia).
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Suffolk County, New York included data on acetochlor in its 2012 through 2018 CCRs.
Suffolk County is served by groundwater from four major aquifers beneath Long Island. Each of
the seven CCRs reported results from the previous year (e.g., the 2012 CCR reported results for
the year 2011). All seven CCRs (representing data collected between 2011 through 2017) stated
that acetochlor was not detected during the testing; the number of samples collected was not
reported.
New York City included data on acetochlor in seven CCRs covering 2010 through 2016.
New York City is served by a large system of surface water networks in New York State. In all
seven years, acetochlor was monitored for but was not detected. The number of samples
collected was not reported in any years. (Note: The 2010 monitoring data were collected as part
of the UCMR 2 program.)
The City of Philadelphia, Pennsylvania included data on acetochlor in its 2010 CCR.
(Monitoring was conducted as part of the UCMR 2 program.) Philadelphia is served by two
surface water sources, the Schuylkill and the Delaware Rivers. In 2010, acetochlor was not
detected during the testing. The number of samples collected and sampling locations were not
reported.
United States Department of Agriculture (USDA) Pesticide Data Program (PDP), 2001-2013
The USDA PDP maintains a national pesticide residue database. PDP was initiated in
1991 to collect data on pesticide residues in food with sampling conducted on a statistically
defensible representation of pesticide residuals in the United States food supply (USDA, 2018a).
Sampling and testing are conducted on fruits and vegetables, select grains, milk, and (as of 2001)
drinking water.
The PDP drinking water project was initiated at CWSs in New York and California in
2001. Since then the drinking water sampling program has expanded, though a somewhat
changing mix of states is sampled each year. At one time or another, CWSs in more than 29
states have contributed raw and/or finished water data to the program (USDA, 2018a). The
CWSs selected for sampling tend to be small and medium-sized systems (primarily CWSs
serving under 50,000), systems served by surface water, and systems located in regions of heavy
agriculture. Sampling of untreated water in addition to treated water began in 2004; sampling
continued until 2013 (USDA, 2018a). Note that temporal trends cannot be evaluated based on
these data since, with the exception of 2002 and 2003, samples were not collected from the same
sites and states in consecutive years.
Acetochlor was included in the USDA PDP (Exhibit 6-18) (USDA, 2018b). Acetochlor
was detected in 407 (6.11 percent) of 6,663 total samples collected between 2001 and 2013, with
MRLs ranging from 0.0092 to 0.0495 |ig/L. Within that dataset, acetochlor was detected in 219
(5.67 percent) of 3,862 finished samples collected. The highest detected concentration of
acetochlor in finished water (0.0824 |ig/L), in 2004, was less than one-half the acetochlor HRL.
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Exhibit 6-18: Summary of Acetochlor PDP Data, 2001-2013
Year
Finished/
Raw
Total Number
of Samples
Number of
Detections
Percent of
Detections
Minimum Value of
Detections (|jg/L)
Maximum Value of
Detections (|jg/L)
Acetochlor
2001
Finished
154
0
0.00%
ND
ND
2002
Finished
403
0
0.00%
ND
ND
2003
Finished
522
16
3.07%
0.017
0.145
2004
Finished
376
11
2.93%
0.052
0.357
Raw
376
25
6.65%
0.0153
0.543
2005
Finished
374
9
2.41%
0.0153
0.314
Raw
376
27
7.18%
0.0153
0.669
2006
Finished
363
3
0.83%
0.0153
0.0824
Raw
364
7
1.92%
0.0153
0.435
2007
Finished
369
2
0.54%
0.0824
0.193
Raw
364
12
3.30%
0.0153
0.346
2008
Finished
310
28
9.03%
0.0153
0.0824
Raw
309
38
12.30%
0.0153
0.660
2009
Finished
306
121
3.92%
0.0153
0.0153
Raw
306
34
11.11%
0.0153
0.210
2010
Finished
284
9
3.17%
0.0153
0.153
Raw
283
15
5.30%
0.0153
0.187
2011
Finished
119
4
3.36%
0.04995
0.299
Raw
120
5
4.17%
0.04995
0.167
2012
Finished
232
16
6.90%
0.0153
0.086
Raw
253
25
9.88%
0.0153
0.25
2013
Finished
50
0
0.00%
-
-
Raw
50
0
0.00%
-
-
Source: USDA, 2018b
ND = no detections in this category
1 Only one distinct detected concentration was reported.
United States Geological Survey (USGS) Pilot Monitoring Program (PMP), 1999
In 1999, a PMP was initiated by USGS and EPA to provide information on pesticide
concentrations in drinking water. This study focused on small drinking water supply reservoirs in
areas with high pesticide use in order to test the sampling approach in areas where pesticides are
probably present (Blomquist et al., 2001). Sampling sites represent a variety of geographic
regions as well as different cropping patterns. The ideal site candidates were mostly small
reservoirs located in high pesticide-use areas with a high runoff potential. Twelve water-supply
reservoirs, considered vulnerable to pesticide contamination, were selected from the list of
candidates. These 12 sites were located in California, Indiana, Louisiana, Missouri, New York,
North Carolina, Ohio, Oklahoma, Pennsylvania, South Carolina, South Dakota, and Texas.
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Samples were collected quarterly throughout the year and at weekly or biweekly intervals
following the primary pesticide-application periods. Water samples were collected from the raw-
water intake and from finished drinking water taps prior to entering the distribution system. At
some sites, samples were also collected at the reservoir outflow.
Acetochlor was an analyte in the PMP. At a method reporting level of 0.002 |ig/L,
acetochlor was detected in 115 (35.6 percent) of the 323 samples taken from raw water sites,
with a maximum concentration of 0.334 |ig/L and a 95th percentile concentration of 0.002 |ig/L.
Acetochlor was detected in 69 (30.3 percent) of the 228 samples taken from finished water sites,
with a maximum concentration of 0.395 |ig/L and a 95th percentile concentration of 0.061 |ig/L
(Blomquist et al., 2001). All raw water and finished water detections were less than one-half the
HRL and the HRL.
United States Geological Survey (USGS') National Water Quality Assessment (NAWQA)
Source Water and Drinking Water Studies
Note that there may be some overlap between the NAWQA data assessment presented
earlier in the ambient water occurrence section and the summaries of NAWQA studies presented
below. The studies presented below include occurrence data from water sources for PWSs.
Organic Compounds in Source Water of Selected Community Water Systems (Hopple
et al., 2009 and Kingsbury et al., 2008), 2002-2005
As part of the NAWQA program, Hopple et al. (2009) and Kingsbury et al. (2008)
conducted studies to characterize anthropogenic organic compounds in U.S. waters used as
source waters for PWSs. Hopple et al. (2009) focused on groundwater and Kingsbury et al.
(2008) focused on surface water. In Phase 1 of the studies (Exhibit 6-19), geographically diverse
source water samples were collected between October 2002 and July 2005 from nine CWSs
served by streams and from 221 CWS wells that withdraw from 12 aquifers. In Phase 2 of the
studies (Exhibit 6-20), USGS collected source and finished water samples at a subset of sites
between June 2004 and September 2005. The reporting level for acetochlor (0.006 (J,g/L) was the
same for both phases and for ground and surface water samples.
In Phase 1, acetochlor was detected in one (0.5 percent) of the 221 groundwater samples,
with a maximum concentration of 0.037 |ig/L, less than one-half the HRL and the HRL.
Acetochlor was detected in 18 (12.3 percent) of 146 surface water samples, with a maximum
concentration of 4.32 |ig/L which is less than one-half the HRL and the HRL (Hopple et al.,
2009; Kingsbury et al., 2008).
In Phase 2, 51 raw and 51 finished groundwater samples were analyzed for acetochlor.
No acetochlor was detected in any of these samples. A total of 90 raw and 87 finished surface
water samples were analyzed for acetochlor. Acetochlor was detected in 16 percent of the raw
surface water samples and in 11 percent of the finished surface water samples (Hopple et al.,
2009; Kingsbury et al., 2008). No detected concentrations exceeded one-half the HRL or the
HRL.
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Exhibit 6-19: Acetochlor Data from Source Water (Hopple et al., 2009 and
Kingsbury et al., 2008) - Summary of Detections from Phase 1
Source Water
Type
Groundwater
Number of
Samples
Percent of Detections
Maximum
Concentration
(ng/L)
All
> 0.1 |jg/L
Groundwater
221
0.5%
0.0%
0.037
Surface Water
146
12.3%
3.4%
4.32
Source: Hopple et al., 2009; Kingsbury et al., 2008
Exhibit 6-20: Acetochlor Data from Source Water - Summary of Detections from
Phase 2 - Groundwater (Hopple et al., 2009) and Surface Water (Kingsbury et al.,
2008)
Contaminant
Number of Samples
Percent of Detections
Maximum Concentration
(ng/L)
Raw Water
Finished
Water
Raw Water
Finished Water
Raw Water
Finished Water
Groundwater
51
51
0%
0%
ND
ND
Surface Water
90
87
16%
11%
0.24
0.14
Source: Hopple et al., 2009; Kingsbury et al., 2008
ND = no detections in this category
Water Quality in Public-Supply Wells (Toccalino et al., 2010), 1993-2007
To assess risks posed by contaminants in public-supply wells, water samples were
collected from source (untreated) groundwater from 932 public-supply wells located in parts of
40 NAWQA Study Units in 41 states (Toccalino et al., 2010). Each well was sampled once
between 1993 and 2007. The public wells sampled in this study represented 629 unique PWSs,
representing 0.5 percent of the approximately 140,000 groundwater-supplied PWSs, but nearly
25 percent of the population served by groundwater-PWSs in the United States. Acetochlor was
detected in two (0.25 percent) of a total of 800 samples. The maximum detected concentration
was equal to 0.114 ng/L; there were no detections greater than one-half the HRL or the HRL.
Reporting limits used for acetochlor in this study ranged from 0.002 to 0.003 |ig/L. Results from
this study are presented in Exhibit 6-21 and Exhibit 6-22.
Exhibit 6-21: Acetochlor Data from Public-Supply Wells (Toccalino et al., 2010) -
Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Groundwater Only
0.0365
0.0753
0.1063
0.1132
0.114
Source: Toccalino et al., 2010
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Exhibit 6-22: Acetochlor Data from Public-Supply Wells (Toccalino et al., 2010) -
Summary of Samples
Source Water
Type
Total
Number of
Samples
All Detections
Detections > Vi HRL
(50 |ig/L)
Detections > HRL
(100 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Groundwater Only
800
2
0.25%
0
0.00%
0
0.00%
Source: Toccalino et al., 2010
Water Quality in Domestic Wells (DeSimone, 2009), 1991-2004
Between 1991 and 2004, USGS assessed water quality from domestic wells across the
United States using NAWQA data (DeSimone, 2009). The program included the analysis of
major ions, trace elements, nutrients, radon, and organic compounds (pesticides and VOCs) at
approximately 2,100 domestic wells (private drinking water wells) across 48 states, covering 30
regional aquifers. In addition, USGS summarized data from wells sampled for NAWQA
agricultural land-use assessment studies to provide an indication of the potential effects of
agricultural land-use practices on the groundwater in the aquifers studied. Reporting thresholds
varied; thresholds of both 0.002 [j,g/L and 0.003 [j,g/L are listed. Acetochlor was detected in two
(0.1 percent) of 1,822 samples from domestic wells in the aquifer studies (DeSimone, 2009).
Detected concentrations of acetochlor did not exceed 0.1 |ig/L. Acetochlor was not detected in
224 samples from domestic wells in the agricultural land use studies (DeSimone, 2009).
Water Quality in Principal Aquifers of the United States (DeSimone et al., 2014), 1991-
2010
Another USGS report based on NAWQA Program ambient groundwater sampling
presents summaries of pesticide and other constituent occurrence, including those for acetochlor
in principal aquifers (DeSimone et al., 2014). Samples were collected between 1990 and 2010
across the U.S. from more than 60 principal aquifers that supply most of the groundwater
pumped across the Nation for drinking water, irrigation, and other uses. At concentrations above
0.1 |ig/L, detection frequencies for acetochlor were equal to 0.03 percent in parts of aquifers
used for drinking water and 0 percent in shallow groundwater beneath agricultural or urban land.
Typical laboratory reporting levels ranged from 0.002 to 0.01 |ig/L.
Water Quality in Carbonate Aquifers (Lindsey et al., 2008), 1993-2005
Also, as part of the NAWQA program, Lindsey et al. (2008) assessed the water quality in
carbonate aquifers, which account for 22 percent of the groundwater pumped by the country's
PWSs. From 1993 to 2005, the study analyzed 1,042 wells and springs across 12 aquifer systems
and 20 states for major ions, radon, nutrients, pesticides, and VOCs. Acetochlor was detected in
three (0.35 percent) of 853 samples. Reporting levels were not given. Detected concentrations of
acetochlor did not exceed 1 |ig/L and were, therefore, less than one-half the HRL and the HRL.
Additional Source Water and Drinking Water Studies
A statewide rural well water survey was conducted by the Iowa Department of Natural
Resources, the Geological Survey Bureau, and the University of Iowa Center for Health Effects
of Environmental Contamination. Phase 2 of the survey (2006 through 2008) involved the
sampling and analysis of groundwater from 473 private drinking water wells (University of
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Iowa, 2009). With a method detection limit (MDL) of 0.05 |ig/L, acetochlor was detected in one
(<1%) of the 469 samples from this study. This single detection was equal to 0.21 |ig/L.
In a study by the Wisconsin Department of Agriculture, Trade and Consumer Protection
(WIDATCP), Wisconsin groundwater was sampled from October 1999 to May 2000 for
multiple chloroacetanilides and their ESA and OA metabolites (WI DATCP, 2000). The 27
monitoring wells, 22 private drinking water wells, and 23 municipal wells sampled for the study
were chosen based on past detections of pesticides or proximity to agricultural fields to increase
the probability of detecting the pesticides. (These are not, therefore, representative of average
occurrence, but are wells of known high occurrence.) The primary use of these herbicides in
Wisconsin is for pre-emergence control of annual grasses in corn. Results for acetochlor are
presented in Exhibit 6-23. Acetochlor was detected in one well at a concentration of 1.2 |ig/L
which is less than one-half the HRL and the HRL. Acetochlor was not detected in the deeper
municipal water wells nor in private drinking water wells. In this study, the laboratory limit of
quantitation (LOQ) was 0.10 |ig/L for acetochlor.
Exhibit 6-23: Wisconsin Groundwater Detections of Acetochlor
Well Type
Wells with
Detects
Percent
Detections
Average Detect
(ng/L)
Highest Detect
(ng/L)
Acetochlor
Monitoring Wells
1
3.70%
1.2
1.2
Private Drinking Water Wells
0
0.00%
ND
ND
Municipal Wells
0
0.00%
ND
ND
Source: WI DATCP, 2000
ND = no detections in this category
6.4.3 Other Data
The Centers for Disease Control and Prevention (CDC) Fourth National Report on Human
Exposure to Environmental Chemicals, 2001-2002
Since 1999, the National Health and Nutrition Examination Survey (NHANES) has
examined the U.S. population annually and released the data in 2-year cycles. The survey is
based on a representative sample of the U.S. population based on age, gender, and race/ethnicity
(CDC, 2019). The Fourth National Report on Human Exposure to Environmental Chemicals was
published in 2009 (CDC, 2009). This report includes data on acetochlor mercapturate (an
acetochlor metabolite) in urine from monitoring conducted in 2001-2002. With a sample size of
2,501, the 95th percentile concentration of acetochlor mercapturate in urine was below the limit
of detection (LOD). The LOD was 0.1 |ig/L. Please note that this value cannot be compared to
the HRL since it represents a human urine concentration, not a drinking water concentration.
Acetochlor mercapturate in human tissue can have its origin in exposure via drinking water,
food, or other routes.
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6.5 Analytical Methods
EPA has published three analytical methods for the analysis of acetochlor in drinking
water:
• EPA Method 526, Revision 1.0, Determination of Selected Semivolatile Organic
Compounds in Drinking Water by Solid Phase Extraction and Capillary Column Gas
Chromatography/Mass Spectrometry (GC/MS). Mean recoveries in fortified reagent
water, groundwater, and surface water range from 89.2 to 132 percent, with Relative
Standard Deviation (RSDs) of 1.1 to 4.5 percent (USEPA, 2000).
• EPA Method 525.2, Revision 2.0, Determination of Organic Compounds by Liquid-
Solid Extraction and Capillary Column Gas Chromatography/Mass Spectrometry,
does not list acetochlor as an analyte; hence, performance details are not available.
However, EPA used Method 525.2 for the development of an MRL for acetochlor for
use in UCMR 2 so data for multiple chloroacetanilides could be generated from a
single analytical method (USEPA, 1995).
• EPA Method 525.3, Version 1.0, Determination of Semivolatile Organic Chemicals
in Drinking Water by Solid Phase Extraction and Capillary Column Gas
Chromatography/Mass Spectrometry (GC/MS). The Lowest Concentration Minimum
Reporting Levels (LCMRLs) generated by the laboratory that developed the method
range from 0.054 to 0.19 |ig/L in Full Scan mode and from 0.0091 to 0.011 |ig/L in
Selected Ion Monitoring (SIM) mode. Mean recoveries in fortified reagent water and
finished drinking water (from groundwater and surface water sources) in Full Scan
mode range from 90.0 to 128 percent, with RSDs of 0.47 percent to 7.6 percent. Mean
recoveries in fortified reagent water and finished drinking water (from groundwater
sources) in SIM mode range from 98.7 percent to 109 percent, with RSDs of 0.67
percent to 9.6 percent. Acetochlor was not analyzed in precision and accuracy studies
performed using two sources of drinking water from surface water (one with Total
Organic Carbon (TOC) of 2.0 mg/L and a second with TOC of 2.52 mg/L and a
hardness of 137 mg/L) and in one of two sources of drinking water from groundwater
(recovery was not observed in groundwater containing a TOC of 0.73 mg/L and a
hardness of 325 mg/L) (USEPA, 2012b).
Laboratories participating in UCMR 2 were required to use EPA Method 525.2 and, as noted in
Section 6.4.2, were required to report acetochlor values at or above the EPA-defined MRL of 2
|.ig/L (72 FR 367; USEPA, 2007). The MRL was set based on the capability of multiple
laboratories at the time.
6.6 Treatment Technologies
EPA evaluates whether suitable treatment technologies are available prior to
promulgating a final National Primary Drinking Water Regulation (NPDWR).
EPA's Drinking Water Treatability Database (USEPA, 2020) summarizes available
technical literature on the efficacy of treatment technologies for a range of priority drinking
water contaminants. The following processes were found to be effective for the removal of
acetochlor: granular activated carbon (59 to 63 percent removal), ozone (56 to 68 percent
removal), powdered activated carbon (43 to 99 percent removal), ultraviolet irradiation (44 to 97
percent removal), and ultraviolet irradiation plus hydrogen peroxide (70 percent removal).
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Processes ineffective for the removal of acetochlor included chlorine and conventional treatment.
The exact percentage removal a water system may achieve with a given technology will be
dependent upon a variety of factors, including source water quality and water system
characteristics. Other treatment processes that are not commonly used for drinking water
treatment but suggested for acetochlor removal include: adsorption using organoclay complexes,
biological treatment,5 and anodic Fenton treatment.6
6.7 References
Aga, D.S., and E.M. Thurman. 2001. Formation and Transport of the Sulfonic Acid Metabolites
of Alachlor and Metolachlor in Soil. Environmental Science and Technology 35:2455-
2460.
Ahmed, F.E. and J.C. Seely. 1983. Acetochlor: Chronic Feeding Toxicity and Oncogenicity
Study in the Rat. Pharmacopathics Research Laboratories, Inc., Laurel, MD. Study No.
PR-80-006. May 20, 1983. Unpublished report (as cited in USEPA, 2006b).
Ahmed, F.E., A.S. Tegeris, and J.C. Seely. 1983. MON 097: 24-Month Oncogenicity Study in
the Mouse. Pharmacopathics Research Laboratories, Inc., Laurel, MD. Report No. PR-
80-007. May 4, 1983. Unpublished report (as cited in USEPA, 2006b).
Amyes, S.J. 1989. SC-5676: 78 Week Feeding Study in CD-I Mice. Life Science Research Ltd.,
Suffolk, England. Study No. 87/SUC0012/0702. June 9, 1989. Unpublished report (as
cited in USEPA, 2006b).
Blomquist, J.D., J.M. Denis, J.L. Cowles, J.A. Hetrick, R.D. Jones, and N.B. Birchfield. 2001.
Pesticides in Selected Water-Supply Reservoirs and Finished Drinking Water, 1999-
2000: Summary of Results from a Pilot Monitoring Program. U.S. Geological Survey
Open-File Report 01-456. 65 pp. Available on the Internet at:
https://pubs.er.usgs.gov/publication/ofr01456.
Centers for Disease Control and Prevention (CDC). 2009. Fourth National Report on Human
Exposure to Environmental Chemicals. Department of Health and Human Services,
Centers for Disease Control and Prevention. Available on the Internet at:
https://www.cdc.gov/exposurereport/pdf/fourthreport.pdf.
CDC. 2019. Fourth National Report on Human Exposure to Environmental Chemicals, Updated
Tables, January 2019: Volume One. Department of Health and Human Services, Centers
for Disease Control and Prevention. Available on the Internet at:
http://www.cdc.gov/exposurereport/.
ChemlDPlus. 2018. Available on the Internet at: http://chem.sis.nlm.nih.gov/chemidplus/.
Accessed December 10, 2018.
5 Experiments involved mixing acetochlor containing water with one of four microbial cultures (Xu et al., 2008).
6 Anodic Fenton treatment involves using an electrochemical process to drive the Fenton reaction to produce
hydroxyl radicals, which are strong reactants. It differs from electrochemical Fenton's reaction by adding hydrogen
peroxide directly to the solution rather than generating it electrochemically and having the anode and cathode
separated by a membrane (Friedman et al., 2006).
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Clay, P. 2000. R290130: L5178Y TK+/- Mouse Lymphoma Mutation Assay. Central Toxicology
Laboratory, Cheshire, UK. Laboratory Study No. VV0231 (Report No. CTL/VV0231),
October 6, 2000. Unpublished report (as cited in USEPA, 2006b).
de Guzman, N.P., P. Hendley, D.I. Gustafson, I. van Wesenbeeck, A.J. Klein, J.D. Fuhrman, K.
Travis, N.D. Simmons, W.E. Teskey, and R.B. Durham. 2005. The Acetochlor
Registration Partnership State Ground Water Monitoring Program. Journal of
Environmental Quality 34:793-803.
DeSimone, L.A. 2009. Quality of Water from Domestic Wells in Principal Aquifers of the United
States, 1991-2004. U.S. Geological Survey Scientific Investigations Report 2008-5227.
139 pp. Available on the Internet at: http://pubs.usgs.gov/sir/2008/5227/.
DeSimone, L.A., P.B. McMahon, and M.R. Rosen. 2014. The Quality of Our Nation's Waters—
Water Quality in Principal Aquifers of the United States, 1991-2010. U.S. Geological
Survey Circular 1360, 151 p. Available on the Internet at: http://pubs.usgs.gov/circ/1360/.
Dictor, M.C., J. Beuve, and C. Mouvet. 2003. Degradation of Acetochlor and Formation of
Ethane sulfonic and Oxanilic Acid Degradates at Two Temperatures in a Neoluvisol. XII
Symposium Pesticide Chemistry, 4-6 June, 2003, Piacenza, Italy.
Dictor, M.C., N. Baran, A. Gautier, and C. Mouvet. 2008. Acetochlor Mineralization and Fate of
its Two Major Metabolites Under Laboratory Conditions. Chemosphere 71:663-670.
Feng, P.C.C. 1991. Soil Transformation of Acetochlor Via Glutathione Conjugation. Pesticide
Biochemistry and Physiology 40:136-142.
Friedman, C., A. Lemley, and A. Hay. 2006. Degradation of Chloroacetanilide Herbicides by
Anodic Fenton Treatment. Journal of Agricultural and Food Chemistry 54:2640.
Gilliom, R.J., J.E. Barbash, C.G. Crawford, P.A. Hamilton, J.D. Martin, N. Nakagaki, L.H.
Nowell, J.C. Scott, P.E. Stackelberg, G.P. Thelin, and D.M. Wolock. 2007. The Quality
of Our Nation's Waters - Pesticides in the Nation's Streams and Ground Water, 1992-
2001. Appendix 7. Statistical Summaries of Water-Quality Data. U.S. Geological Survey
Circular 1291. 172 pp. Available on the Internet at:
http://water.usgs.gov/nawqa/pnsp/pubs/circl291/appendix7/.
Hackett, A.G., D.I. Gustafson, S.J. Moran, P. Hendley, I. van Wesenbeeck, N.D. Simmons, A.J.
Klein, J.M. Kronenberg, J.D. Fuhrman, J.L. Honegger, J. Hanzas, D. Healy, and C.T.
Stone. 2005. The Acetochlor Registration Partnership Surface Water Monitoring Program
for Four Corn Herbicides. Journal of Environmental Quality 34:877-889.
Hamilton, P. A., T.L. Miller, and D.N. Myers. 2004. Water Quality in the Nation's Streams and
Aquifers: Overview of Selected Findings, 1991-2001. USGS Circular 1265. Available on
the Internet at: http://water.usgs.gov/pubs/circ/2004/1265/pdf/circularl265.pdf.
Hardisty, J.F. 1997a. Pathology Working Group Peer Review of Histiocytic Sarcoma in Female
Mice from Two Long-Term Studies with Acetochlor. Experimental Pathology
Laboratories, Inc., Research Triangle Park, NC. Laboratory Project ID CTL/C/3196,
February 11, 1997. Unpublished report (as cited in USEPA, 2006b).
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Hardisty, J.F. 1997b. Pathology Working Group Peer Review of Hepatocellular Neoplasms in
the Liver of Rats and Mice from Five Long-Term Studies with Acetochlor. Experimental
Pathology Laboratories, Inc., Research Triangle Park, NC. Laboratory Project ID
CTL/C/3197, February 11, 1997. Unpublished report (as cited in USEPA, 2006b).
Hardisty, J.F. 1997c. Pathology Working Group Peer Review of Neoplastic Lesions in the Lung
of Male and Female Mice from Two Long-Term Studies with Acetochlor. Experimental
Pathology Laboratories, Inc., Research Triangle Park, NC. Laboratory Project ID
CTL/C/3198, February 11, 1997. Unpublished report (as cited in USEPA, 2006b).
Hopple, J.A., G.C. Delzer, and J.A. Kingsbury. 2009. Anthropogenic Organic Compounds in
Source Water of Selected Community Water Systems that Use Groundwater, 2002-05.
U.S. Geological Survey Scientific Investigations Report 2009-5200. 74 pp. Available on
the Internet at: http://pubs.usgs.gov/sir/2009/5200/pdf/sir2009-5200.pdf.
Hazardous Substances Data Bank (HSDB). 2012. Profile for Acetochlor. Available on the
Internet at: http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen7HSDB. Last revision date:
October 12, 2012.
ICI, Inc. 1988. MRIDNo. 41565118; HEDDocNo. 008478. (or Broadmeadow, A., 1988). SC-
5676: Toxicity Study by Oral (Capsule) Administration to Beagle Dogs for 52 Weeks.
Life Science Research, Ltd., Suffolk, England. Study No.: LSR Report 88/SUC018/0136;
December 2, 1988 (as cited in USEPA, 2006b and USEPA, 2018).
Kingsbury, J.A., G.C. Delzer, and J.A. Hopple. 2008. Anthropogenic Organic Compounds in
Source Water of Nine Community Water Systems that Withdraw from Streams, 2002-05:
U.S. Geological Survey Scientific Investigations Report 2008-5208. 66 pp. Available on
the Internet at: http://pubs.usgs.gov/sir/2008/5208/pdf/sir2008-5208.pdf.
Leahy, P.P. and T.H. Thompson. 1994. Overview of the National Water-Quality Assessment
Program. U.S. Geological Survey Open-File Report 94-70. 4 pp. Available on the
Internet at: http://water.usgs.gov/nawqa/NAWOA.OFR94-7Q.html.
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National Research Council (NRC). 2002. Opportunities to Improve the U.S. Geological Survey
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Thurman, E.M., D.A. Goolsby, D.S. Aga, M.L. Pomes, and M.T. Meyer. 1996. Occurrence of
Alachlor and its Sulfonated Metabolite in Rivers and Reservoirs of the Midwestern
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Toccalino, P.L., J.E. Norman, and K.J. Hitt. 2010. Quality of Source Water from Public-supply
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University of Iowa. 2009. Iowa Statewide Rural Well Water Survey Phase 2 (SWRL2). Center for
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United States Department of Agriculture (USD A). 2018a. PDP Drinking Water Project (2001 -
2013). Available on the Internet at: https://www.ams.usda.gov/datasets/pdp/pdp-drinking-
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on February 28, 2019.
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Water Systems; Final Rule. Federal Register 64(180):50556, September 17, 1999.
USEPA. 2000. Method 526. Determination of Selected Semivolatile Organic Compounds in
Drinking Water by Solid Phase Extraction and Capillary Column Gas
Chromatography/Mass Spectrometry (GC/MS). Revision 1.0. National Exposure
Research Laboratory, Office of Research and Development. EPA 815-R-00-014.
USEPA. 2001. Unregulated Contaminant Monitoring Regulation for Public Water Systems;
Analytical Methods for List 2 Contaminants; Clarifications to the Unregulated
Contaminant Monitoring Regulation. Federal Register 66(8): 2273, January 11, 2001.
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Acetochlor (Fourth Evaluation). Final Report. Cancer Assessment Review Committee
(CARC), Health Effects Division Office of Pesticide Programs. EPA-HQ-OPP-2005-
0227-0016. Available on the Internet at:
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2004-08-31a.pdf.
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09/documents/cancer guidelines final 3-25-05.pdf. Accessed February 2015.
USEPA. 2006a. Report of the Food Quality Protection Act (FQPA) Tolerance Reassessment
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Decision (TRED) Document, EPA-HQ-OPPTS, PC Code: 121601, DP Barcode:
D292336. Available on the Internet at: https://www.regulations.gov/document?D=EPA-
HO-OPP-2005-0227-0024.
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USEPA. 2006c. Cumulative Risk Assessment for the Chloroacetanilides. Office of Prevention,
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Systems Revisions. Federal Register 72(2): 367, January 4, 2007.
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Monitoring Regulation (UCMR 1) in Support of Regulatory Determinations for the
Second Drinking Water Contaminant Candidate List. EPA 815-R-08-013.
USEPA. 2009. The Analysis of Regulated Contaminant Occurrence Data from Public Water
Systems in Support of the Second Six-Year Review of National Primary Drinking Water
Regulations. EPA-815-B-09-006. October 2009.
USEPA. 2010. Letter from James A. Tompkins, EPA Office of Prevention, Pesticides, and Toxic
Substances, to Dr. David I. Gustafason, Monsanto Company. May 12, 2010. Available on
the Internet at: https://www3.epa.gov/pesticides/chem search/ppls/000524-00473-
20100512.pdf.
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Biological and Economic Analysis Division, Office of Pesticide Programs. Available on
the Internet at: http://www.epa.gov/sites/production/files/2015-
10/documents/market estimates2007.pdf.
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September. Available at: https://cfpub.epa.gov/ncea/risk/recordisplav.cfm?deid=236252.
USEPA. 2012a. Second Unregulated Contaminant Monitoring Rule Dataset. Available on the
Internet at: https://www.epa.gov/dwucmr/occurrence-data-unregulated-contaminant-
monitoring-rule#2. Accessed January 2012.
USEPA. 2012b. Method 525.3. Determination of Semivolatile Organic Chemicals in Drinking
Water by Solid Phase Extraction and Capillary Column Gas Chromatography/Mass
Spectrometry (GC/MS). Version 1.0. National Exposure Research Laboratory, Office of
Research and Development. EPA 600-R-12-010.
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New Uses of Acetochlor on Sugar Beet and Peanut. PC Code: 121601, DP No. D413438.
Office of Chemical Safety and Pollution Prevention, OPP. EPA-HQ-OPP-2012-0829-
0009. Available on the Internet at: https://www.regulations.gov/document?D=EPA-HQ-
QPP-2012-0829-0009.
USEPA. 2014. Occurrence Data from the Second Unregulated Contaminant Monitoring
Regulation (UCMR 2). April 2014. EPA 815-R14-004.
USEPA. 2016. The Analysis of Regulated Contaminant Occurrence Data from Public Water
Systems in Support of the Third Six-Year Review of National Primary Drinking Water
Regulations: Chemical Phase Rules and Radionuclides Rules. EPA 810-R-16-014.
December 2016.
USEPA. 2017a. TRI Explorer: Trends. Available on the Internet at
https://enviro.epa.gov/triexplorer/tri release.trends. Accessed November 2017.
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USEPA. 2017b. Pesticide Industry Sales and Usage: 2008 to2012 Market Estimates. Biological
and Economic Analysis Division, Office of Pesticide Programs. Available on the Internet
at: https://www.epa.gov/sites/production/files/2017-01/documents/pesticides-industrv-
sales-usage-2016 O.pdf.
USEPA. 2017c. Human Health Benchmarks for Pesticides: Updated 2017 Technical Document.
Available on the Internet at: https://ofmpub.epa.gov/apex/pesticides/f?p=122:3. Accessed
on February 28, 2019.
USEPA. 2018. Acetochlor/121601, Acetochlor Human Health Risk Assessment for Proposed
New Use on Alfalfa and Related Animal Commodities. PC Code: 121601, DP No.
D438094. Office of Chemical Safety and Pollution Prevention, EPA-HQ-OPP-2017-
0235-0009. Available on the Internet at: https://www.regulations.gov/document?D=EPA-
HO-QPP-2017-023 5-0009.
USEPA. 2019. CompTox Chemicals Dashboard, Searched by DSSTox Substance Id =
DTXSID8023848. Available on the Internet at:
https://comptox.epa. gov/dashboard/dsstoxdb/results?search=DTXSID8023 848.
USEPA. 2020. Drinking Water Treatability Database.
https://iaspub.epa.gov/tdb/pages/general/home.do. Last updated March 2020.
United States Geological Survey (USGS). 2016. National Water Information System (NWIS)
Water-Quality Web Services. Available on the Internet at: https://waterdata.usgs.gov/nwis?.
Last modified December 2016.
USGS. 2018. Pesticide National Synthesis Project, Pesticide Use Maps. Available on the Internet
at: http://water.usgs.gov/nawqa/pnsp/usage/maps/compound listing.php?vear=02.
Accessed December 2018.
Virgo, D.M. and Broadmeadow, A. 1988. SC-5676: Combined Oncogenicity and Toxicity Study
in Dietary Administration to CD Rats for 104 Weeks. Life Science Research Ltd.,
Suffolk, England. Study No. 88/SUC017/0348. March 18, 1988. Unpublished report (as
cited in USEPA, 2006b).
Water Quality Portal (WQP). 2017. Water Quality Portal Data Warehouse. Available on the
Internet at: https://www.waterqualitvdata.us/. Data Warehouse consulted December 2017.
WQP. 2018. Water Quality Portal Data Warehouse. Available on the Internet at:
https://www.waterqualitydata.us/. Data Warehouse consulted September 2018.
Williams, J. 2000a. R290130: 28 Day Dietary Toxicity Study in Rats (Dose Range Finder for a
90 Day Study). Zeneca Central Toxicology Laboratory, Cheshire, UK. Laboratory
Document No. CTL/KR1352/REG/REPT, May 9, 2000. Unpublished report (as cited in
USEPA, 2006b).
Williams, J. 2000b. R290130: 90 Day Dietary Toxicity Study in Rats. Zeneca Central
Toxicology Laboratory, Cheshire, UK. Laboratory Document No.
CTL/PR1148/REG/REPT, June 27, 2000. Unpublished report (as cited in USEPA,
2006b).
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Wisconsin Department of Agriculture, Trade, and Consumer Protection (WIDATCP). 2000.
Chloroacetanilide Herbicide Metabolites in Wisconsin Groundwater. Final Report. ARM
Pub 82 (June 2000). Madison, WI: Groundwater Unit, ARM division, WI DATCP.
Xu, J., M. Yang, J. Dai, H. Cao, C. Pan, X. Qiu, and M. Xu. 2008. Degradation of Acetochlor by
Four Microbial Communities. Bioresource Technology 99:7797.
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Chapter 7:
Methyl Bromide
A chapter from:
Final Regulatory Determination 4 Support Document
EPA Report 815-R-21-001
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Contents
Contents 7-2
Exhibits 7-3
Abbreviations 7-4
7.1 Contaminant Background and Chemical and Physical Properties 7-6
7.2 Sources and Environmental Fate 7-7
7.2.1 Production, Use, and Rel ease 7-7
7.2.2 Environmental Fate 7-13
7.3 Health Effects 7-14
7.3.1 Toxicokinetics 7-14
7.3.2 Available Health Effects Assessments 7-14
7.3.3 Health Effects 7-15
7.3.4 Basis of the HRL 7-18
7.3.5 Health Effects Data Gaps 7-18
7.4 Occurrence 7-19
7.4.1 Occurrence in Ambient Water 7-19
7.4.2 Occurrence in Drinking Water 7-26
7.5 Analytical Methods 7-46
7.6 Treatment Technologies 7-46
7.7 References 7-47
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Exhibits
Exhibit 7-1: Chemical Structure of Methyl Bromide 7-7
Exhibit 7-2: Physical and Chemical Properties of Methyl Bromide 7-7
Exhibit 7-3: IUR Reported Annual Manufacture and Importation of Methyl Bromide in the
United States, 1986-2006 (pounds) 7-9
Exhibit 7-4: CDR Reported Annual Manufacture and Importation of Methyl Bromide in
the United States, 2011-2015 (pounds) 7-9
Exhibit 7-5: Estimated Annual Agricultural Use of Methyl Bromide (2016) 7-10
Exhibit 7-6: Environmental Releases of Methyl Bromide in the United States, 1988-2016 7-11
Exhibit 7-7: Summary and State Count of Total Releases and Total Surface Water
Discharges of Methyl Bromide, 1988-2016 7-12
Exhibit 7-8: Available Health Effects Assessments for Methyl Bromide 7-14
Exhibit 7-9: Methyl Bromide NAWQA Data - Summary of Detected Concentrations 7-20
Exhibit 7-10: Methyl Bromide NAWQA Data - Summary of Samples 7-21
Exhibit 7-11: Methyl Bromide NAWQA Data - Summary of Sites 7-21
Exhibit 7-12: Methyl Bromide NWIS Data, 1991 -2016 7-23
Exhibit 7-13: Methyl Bromide STORET Data - Summary of Detected Concentrations 7-25
Exhibit 7-14: Methyl Bromide STORET Data - Summary of Samples and Sites 7-25
Exhibit 7-15: Methyl Bromide STORET Data - Summary of States 7-25
Exhibit 7-16: Methyl Bromide Data from UCMR 3 Assessment Monitoring - Summary of
Detected Concentrations 7-27
Exhibit 7-17: Methyl Bromide National Occurrence Measures Based on UCMR 3
Assessment Monitoring Data - Summary of Samples 7-28
Exhibit 7-18: Methyl Bromide National Occurrence Measures Based on UCMR 3
Assessment Monitoring Data - Summary of System and Population Served Data -
Detections 7-29
Exhibit 7-19: Methyl Bromide Occurrence Data from UCM Rounds 1 and 2 - Summary of
Detected Concentrations 7-31
Exhibit 7-20: Methyl Bromide Occurrence Data from UCM Rounds 1 and 2 - Summary of
Samples 7-31
Exhibit 7-21: Methyl Bromide Occurrence Data from UCM Rounds 1 and 2 - Summary of
System and Population Served Data - All Detections 7-32
Exhibit 7-22: Methyl Bromide State Drinking Water Occurrence Data - Summary of
Detected Concentrations 7-34
Exhibit 7-23: Methyl Bromide State Drinking Water Occurrence Data - Summary of
Samples 7-38
Exhibit 7-24: Methyl Bromide State Drinking Water Occurrence Data - Summary of
Systems 7-41
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Abbreviations
ARB
Air Resources Board
AT SDR
Agency for Toxic Substances and Disease Registry
AwwaRF
American Water Works Association Research Foundation
BW
Body Weight
CAS
Chemical Abstracts Service
CCL 4
Fourth Contaminant Candidate List
CDC
Centers for Disease Control and Prevention
CDR
Chemical Data Reporting
CSF
Cancer Slope Factor
CWS
Community Water System
CWSS
Community Water System Survey
DNA
Deoxyribonucleic Acid
DWI
Drinking Water Intake
EPA
Environmental Protection Agency
EPCRA
Emergency Planning and Community Right-to-Know Act
GWUDI
Groundwater Under the Direct Influence of Surface Water
HA
Health Advisory
HHRA
Human Health Risk Assessment
HRL
Health Reference Level
HSDB
Hazardous Substances Data Bank
ICR
Information Collection Request
IRIS
Integrated Risk Information System
IUR
Inventory Update Reporting
Kh
Henry's Law Constant
Koc
Octanol-Water Partitioning Coefficient
Kow
Organic Carbon Partitioning Coefficient
LCMRL
Lowest Concentration Minimum Reporting Level
LOAEL
Lowest Observed Adverse Effect Level
MRID
Master Record Identification Number
MRL
Minimum Reporting Level
MTBE
Methyl Tertiary Butyl Ether
NAWQA
National Water-Quality Assessment
NCFAP
National Center for Food and Agricultural Policy
ND
No Detection
NIRS
National Inorganics and Radionuclides Survey
NL
Not Likely to be Carcinogenic in Humans
NOAEL
No Observed Adverse Effect Level
NPDES
National Pollutant Discharge Elimination System
NPDWR
National Primary Drinking Water Regulation
NPL
National Priority List
NTP
National Toxicology Program
NWIS
National Water Information System
OPP
Office of Pesticide Programs
OPPTS
Office of Prevention, Pesticide and Toxic Substances
OW
Office of Water
PA
Principal Aquifer
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POD
Point of Departure
PPRTV
Provisional Peer-Reviewed Toxicity Value
PWS
Public Water System
RED
Reregi strati on Eligibility Decision
RfD
Reference Dose
RSC
Relative Source Contribution
RSD
Relative Standard Deviation
SDWIS/Fed
Safe Drinking Water Information System/Federal Version
SIM
Selected Ion Monitoring
SOC
Synthetic Organic Compound
STORET
Storage and Retrieval Data System
SYR2
Second Six-Year Review
SYR3
Third Six-Year Review
TRED
Tolerance Reassessment Progress and Risk Management Decision
TRI
Toxics Release Inventory
TSCA
Toxic Substances Control Act
UCM
Unregulated Contaminant Monitoring
UCMR
Unregulated Contaminant Monitoring Rule
UCMR 1
First Unregulated Contaminant Monitoring Rule
UCMR 2
Second Unregulated Contaminant Monitoring Rule
UCMR 3
Third Unregulated Contaminant Monitoring Rule
UF
Uncertainty Factor
UNEP
United Nations Environment Programme
USGS
United States Geological Survey
VOC
Volatile Organic Compound
WQP
Water Quality Portal
WRF
Water Research Foundation
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Chapter 7: Methyl Bromide
The Environmental Protection Agency (EPA) is evaluating methyl bromide as a
candidate for regulation as a drinking water contaminant under the fourth Contaminant
Candidate List (CCL 4) Regulatory Determinations process. Information on the CCL 4 process is
found in Chapter 1. Background on data sources used to evaluate CCL 4 chemicals is found in
Chapter 2.
This chapter presents information and analyses specific to methyl bromide, including
background information on the contaminant, information on contaminant sources and
environmental fate, an analysis of health effects, an analysis of occurrence in ambient and
drinking water, and information about the availability of analytical methods and treatment
technologies.
7.1 Contaminant Background and Chemical and Physical Properties
Methyl bromide (also commonly known as bromomethane) is a halogenated alkane and
occurs as a gas. Methyl bromide has been used as a soil fumigant and pesticide (USEPA, 2006a).
Uses have included application to soil before planting, to crops after harvest, to vehicles and
buildings, and other specialized purposes. It is currently registered as a pesticide by EPA and is
in the registration review process (USEPA, 2018a.) Methyl bromide has been found at multiple
sites on EPA's National Priority List (NPL) (ATSDR, 1992).
Methyl bromide is an ozone-depleting chemical regulated under the Montreal Protocol.
Use of the chemical in the United States was phased out in 2005, except for specific critical use
exemptions and quarantine and pre-shipment exemptions. Critical use exemptions have included
strawberry cultivation and production of dry cured pork. Additional information on the methyl
bromide phase-out and exemptions in the United States can be found on EPA's web site:
https://www.epa.gov/ods-phaseout/methyl-bromide (USEPA, 2014a).
In August of 2006, EPA's Office of Prevention, Pesticide and Toxic Substances (OPPTS)
released a Tolerance Reassessment Progress and Risk Management Decision (TRED) for methyl
bromide and a Reregi strati on Eligibility Decision (RED) for commodity uses (USEPA, 2006a).
A RED for soil fumigant uses was released in July 2008 and amended in May 2009 (USEPA,
2009a). In 2011, EPA issued a cancellation order for certain soil-related uses of methyl bromide,
but this order did not affect its use as a post-harvest fumigant (76 FR 29238; USEPA, 201 la).
Synonyms for methyl bromide include bromomethane, monobromomethane, curafume,
Meth-O-Gas, and Brom-O-Sol, according to the Hazardous Substances Data Bank (HSDB,
2013).
Exhibit 7-1 presents the structural formula for methyl bromide. Physical and chemical
properties and other reference information are listed in Exhibit 7-2.
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Exhibit 7-1: Chemical Structure of Methyl Bromide
H3C Br
Source: USEPA, 2019a
Exhibit 7-2: Physical and Chemical Properties of Methyl Bromide
Property
Data
Chemical Abstracts Service (CAS)
Registry Number
74-83-9 (ChemlDPIus, 2018)
EPA Pesticide Chemical Code
053201 (ChemlDPIus, 2018)
Chemical Formula
CHsBr (ChemlDPIus, 2018)
Molecular Weight
94.94 g/mol (HSDB, 2013)
Color/Physical State
Colorless, transparent gas or volatile liquid (HSDB, 2013)
Boiling Point
3.5 deg C (HSDB, 2013)
Melting Point
-93.7 deg C (HSDB, 2013)
Density
1.730 at 0 deg C relative to water at 4 deg C (specific gravity; liquid), 3.974
g/L at 20 deg C (gas) (HSDB, 2013)
Freundlich Adsorption Coefficient
3 (|ig/g)(L/|ig)1/n (Speth et al., 2001 - predicted)
Vapor Pressure
1,620 mm Hg at 25 deg C (HSDB, 2013)
Henry's Law Constant (Kh)
0.00734 atm-m3/mol at 25 deg C (HSDB, 2013)
Log Kow
1.19 (dimensionless) (HSDB, 2013)
Koc
9-22 L/kg (HSDB, 2013)
Solubility in Water
13,400 and 15,200 mg/L at 25 deg C (HSDB, 2013)
Other Solvents
Lower alcohols, ethers, esters, ketones, aromatic hydrocarbons,
halogenated hydrocarbons, carbon disulfide (HSDB, 2013)
Conversion Factors
(at 25 deg C, 1 atm)
1 ppm (v/v) = 0.258 mg/m3
1 mg/m3= 3.88 ppm (v/v)
(calculated)
Note: Many of these properties are temperature dependent. Values are given for properties at 20-25 deg C unless
otherwise noted. Due to varying experimental conditions, and due to the variabilities associated with modeling, the
standard information sources may provide a range of values. Where more than one value was available from these
sources, one value was selected for this table based on best professional judgment.
7.2 Sources and Environmental Fate
7.2.1 Production, Use, and Release
As noted above, use of methyl bromide since 2005 has been limited to specific critical
use exemptions and quarantine and pre-shipment exemptions. A report by the United Nations
Environment Programme (UNEP, 2018) indicates that critical use exemptions in the United
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States declined steadily from 9,553 metric tons of methyl bromide in 2005 to 235 metric tons in
2016, and stood at zero in 2017 and 2018. A total of 50 metric tons were "on hand" in the U.S. at
the end of 2016 (UNEP, 2018).
Production data for methyl bromide are available from EPA's Inventory Update
Reporting (IUR) and Chemical Data Reporting (CDR) programs, and industrial release data are
available from EPA's Toxics Release Inventory (TRI), as described below. Additional
information about these sources is provided in Chapter 2.
Inventory Update Reporting (IUR) / Chemical Data Reporting (CDR) Program
Under the authority of the Toxic Substances Control Act (TSCA), EPA gathers
information on production (including both manufacture and importation) of industrial chemicals.
Under the IUR, producers provided information once every four years from 1986 to 2006. Since
2012, producers have continued to provide information in accordance with the CDR Rule that
superseded the IUR in 2011. Under CDR, producers collect annual production data and report it
once every four years.
Until 2006, the IUR regulation required manufacturers and importers of organic chemical
substances included on the TSCA Chemical Substance Inventory to report site and
manufacturing information for chemicals produced (i.e., manufactured or imported) in amounts
of 10,000 pounds or more at a single site. In 2006, the minimum threshold for reporting was
increased to 25,000 pounds and reporting began for inorganic chemicals (USEPA, 2008a).
Among changes made under CDR, a two-tier system of reporting thresholds was implemented,
with 25,000 pounds as the threshold for some contaminants and 2,500 pounds as the threshold
for others (USEPA, 2014b; USEPA, 2018b). As a result of program modifications, the results
from 2006 and later might not be directly comparable to results from earlier years. Under CDR,
every four years manufacturers and importers are required to report annual data from each of the
previous four years, provided that the thresholds of 2,500 or 25,000 pounds are met during at
least one of the four years (USEPA, 2018b).
For the historical IUR data, EPA assigned one of eight production volume ranges for
each chemical included in the inventory. The ranges used for the 2006 reports differ slightly
from those used in the 1986 through 2002 reports, as described in Chapter 2. Exhibit 7-3 presents
the publicly available information on production of methyl bromide in the United States from
1986 to 2006 as reported under IUR. Production of methyl bromide in the United States peaked
in 1994, decreased over the next two cycles, and then increased again in 2006.
Exhibit 7-4 presents the publicly available production data for methyl bromide in the
United States from 2011 to 2015 as reported under CDR. No quantitative data for methyl
bromide production are available from the CDR dataset.
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Exhibit 7-3: IUR Reported Annual Manufacture and Importation of Methyl Bromide
in the United States, 1986-2006 (pounds)
Chemical Inventory Update Reporting Cycle
1986
1990
1994
1998
2002
2006
Range of
Production/Importation
Volume
> 10 million
50 million
> 10 million
50 million
> 50 million
100 million
> 10 million
50 million
> 1 million -
10 million
10 to < 50
million
Source: USEPA, 2008a
Exhibit 7-4: CDR Reported Annual Manufacture and Importation of Methyl
Bromide in the United States, 2011-2015 (pounds)
Chemical Inventory Update Re
porting Cycle
2011
2012
2013
2014
2015
Range of Production /
Importation Volume
Withheld
Withheld
Withheld
Withheld
Withheld
"Withheld" = results not publicly available due to confidential business information.
Source: USEPA, 2018b
EPA Office of Pesticide Programs (OPP) Amended Reregistration Eligibility Decision (RED)
In accordance with the Montreal Protocol, most methyl bromide usage in the United
States was phased out between 1999 and 2005. Remaining uses in the United States fall under
the Montreal Protocol's critical use exemption and quarantine and pre-shipment exemption. In
2007, methyl bromide applied under the critical use exemption amounted to 5,482 metric tons, or
approximately 12 million pounds. Quarantine and pre-shipment usage is not tracked by EPA. As
of January 1, 2008, pre-2005 methyl bromide stocks stood at 6,458 metric tons, or approximately
14 million pounds (USEPA, 2009a).
EPA Pesticide Industry Sales and Usage Report
EPA's Pesticide Industry Sales and Usage reports state that the amount of methyl
bromide active ingredient used in the United States was between 38 and 45 million pounds in
1997; between 28 and 33 million pounds in 1999; between 20 and 25 million pounds in 2001;
between 13 and 17 million pounds in 2003; between 12 and 16 million pounds in 2005; between
11 and 15 million pounds in 2007; between 5 and 9 million pounds in 2009; and between 2 and 6
million pounds in 2012 (USEPA, 2004; USEPA, 2011b; USEPA, 2017a).
National Center for Food and Agricultural Policy (NCFAP) Pesticide Use Database
NCFAP maintains a national Pesticide Use Database, primarily for herbicides. Pesticide
use estimates are based on state-level commercial agriculture usage patterns and state-level crop
acreage. NCFAP lists uses of methyl bromide on 24 crops totaling approximately 44 million
pounds of active ingredient per year in 33 states in 1992, and lists uses on 20 crops totaling 33
million pounds of active ingredient per year in 29 states in 1997 (NCFAP, 2000).
United States Geological Survey (USGS') Pesticide Use Maps
USGS has produced maps of pesticide use for 244 compounds used in United States crop
production. The pesticide use maps show the average annual pesticide use intensity expressed as
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Final Regulatory Determination 4 Support Document —. Ch 7, Methyl Bromide
January 2021
average weight (in pounds) of a pesticide applied to each square mile of agricultural land in a
county. The maps represent pesticide use from 2016. The USGS maps were created using data
from NCFAP and county-level information on harvested crop acreage from the Census of
Agriculture. Exhibit 7-5 (USGS, 2018) shows the geographic distribution of estimated average
annual methyl bromide use in the United States circa 2016. A breakdown of use by crop is also
included. The map indicates that methyl bromide use is heaviest in North Carolina and
California.
Exhibit 7-5: Estimated Annual Agricultural Use of Methyl Bromide (2016)
Estimated Agricultural Use for Methyl Bromide , 2016 (Preliminary)
I I No esllmaled use
100-
80-
60-
40
% 20-
Use by Year and Crop
B
M
!
~n
UPnn
1 =
im co ^ into co ot o t—(m co into r~~ co cd o i—(m co ^ in to
cnoicn cncDcrjcn cnoo oooo oooo i—i—i—i—i—i—
CT> CD Ol C7) OT CD CD CD O O O O O O O O O O O O O O O O O
I— 1-1— i-1— T-1-1- CM CM CM 35.10
I I No estimated use
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Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide
January 2021
information on toxic chemical releases from facilities that meet specific criteria. This reported
information is maintained in a database accessible through TRI Explorer (USEPA, 2017b).
Although TRI can provide a general idea of release trends, it has limitations. Not all
facilities are required to report all releases. Facilities are required to report releases if they
manufacture or process more than 25,000 pounds of a chemical or use more than 10,000 pounds
per year. Reporting requirements have changed over time (e.g., reporting thresholds have
decreased), so conclusions about temporal trends should be drawn with caution. TRI data are
meant to reflect releases and should not be used to estimate general public exposure to a
chemical (USEPA, 2019b).
TRI data for methyl bromide from the years 1988 through 2016 are summarized in
Exhibit 7-6 (USEPA, 2017b). TRI data show a general long-term declining trend in industrial
releases of methyl bromide, from over a million pounds per year in the 1990s to under 500,000
pounds most years since 2010. Air emissions have tended to dominate releases, with the
exception of 2015, when an anomalously large quantity (350,000 pounds) was reported released
by underground injection from a single facility.
Exhibit 7-6: Environmental Releases of Methyl Bromide in the United States, 1988-
2016
Year
On-Site Releases (in pounds)
Total Off-
Site
Releases
(in pounds)
Total On-
and Off-Site
Releases
(in pounds)
Air
Emissions
Surface
Water
Discharges
Underground
Injection
Releases to
Land
1988
2,784,795
0
1,546
0
0
2,786,341
1989
3,013,942
0
66,525
0
0
3,080,467
1990
3,030,044
0
28,000
0
0
3,058,044
1991
3,121,693
0
1,000
0
15
3,122,708
1992
3,062,397
390
1,000
0
250
3,064,037
1993
3,233,544
760
1,100
0
5
3,235,409
1994
2,680,975
13
0
0
0
2,680,988
1995
2,601,734
14
3,817
0
0
2,605,565
1996
2,310,012
14
303
6
0
2,310,335
1997
1,876,553
30
244
6
0
1,876,833
1998
1,556,612
30
230
11
0
1,556,883
1999
1,431,753
29
0
4
1,603
1,433,389
2000
969,971
37
5
9
5
970,027
2001
764,070
139
29,653
6,048
3,441
803,351
2002
535,175
112
3,984
4
280
539,555
2003
523,113
140
2,392
3
284
525,932
2004
535,258
200
16,687
2
61
552,208
2005
421,125
44
11,936
9
440
433,555
2006
398,226
361
9,015
0
650
408,252
2007
379,394
133
8,028
0
1,266
388,821
2008
545,054
71
6,289
0
1,089
552,503
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January 2021
Year
On-Site Releases (in pounds)
Total Off-
Site
Releases
(in pounds)
Total On-
and Off-Site
Releases
(in pounds)
Air
Emissions
Surface
Water
Discharges
Underground
Injection
Releases to
Land
2009
547,171
1,446
7,466
0
760
556,843
2010
542,269
1,254
1,892
0
22
545,437
2011
394,222
1,094
4,700
0
23
400,039
2012
280,339
47
2,000
1
11
282,398
2013
232,655
44
750
0
10
233,459
2014
212,295
44
14,000
129
17
226,485
2015
171,738
45
350,000
57
0
521,840
2016
255,456
8
0
37
0
255,501
Source: USEPA, 2017b
Exhibit 7-7 presents a summary of total releases and total surface water discharges that
includes the count of states reporting releases for the years 1988 through 2016 (USEPA, 2017b).
The number of states reporting any releases of methyl bromide ranged from 11 to 24 over the
years 1988-2016. The number of states reporting surface water discharges of methyl bromide
ranged from zero to four for the years 1988-2016. (For the purposes of TRI, "state" counts
include the District of Columbia and United States territories in addition to the 50 states.)
Exhibit 7-7: Summary and State Count of Total Releases and Total Surface Water
Discharges of Methyl Bromide, 1988-2016
Year
Total Release
(in pounds)
Count of States
with Releases
Total Surface
Water
Discharges
(in pounds)
Count of States
with Surface
Water
Discharges
1988
2,786,341
19
0
0
1989
3,080,467
21
0
0
1990
3,058,044
21
0
0
1991
3,122,708
24
0
0
1992
3,064,037
23
390
2
1993
3,235,409
22
760
2
1994
2,680,988
21
13
2
1995
2,605,565
22
14
2
1996
2,310,335
22
14
1
1997
1,876,833
21
30
1
1998
1,556,883
20
30
1
1999
1,433,389
23
29
1
2000
970,027
24
37
2
2001
803,351
23
139
2
2002
539,555
20
112
4
2003
525,932
18
140
4
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Year
Total Release
(in pounds)
Count of States
with Releases
Total Surface
Water
Discharges
(in pounds)
Count of States
with Surface
Water
Discharges
2004
552,208
17
200
3
2005
433,555
17
44
2
2006
408,252
16
361
2
2007
388,821
14
133
2
2008
552,503
15
71
3
2009
556,843
15
1,446
3
2010
545,437
16
1,254
3
2011
400,039
15
1,094
4
2012
282,398
14
47
3
2013
233,459
15
44
2
2014
226,485
13
44
1
2015
521,840
13
45
1
2016
255,501
11
8
2
Source: USEPA, 2017b
7.2.2 Environmental Fate
As discussed in Chapter 2, the measures used by EPA to assess mobility include (where
available) the organic carbon partitioning coefficient (Koc), log octanol-water partitioning
coefficient (log Kow), Henry's Law Constant (Kh), water solubility, and vapor pressure. Methyl
bromide's vapor pressure of 1,620 mmHg at 25 degrees C indicates that if it is released to the
atmosphere, the contaminant will exist entirely in the vapor phase. Based on a Koc of 9 to 22
L/kg, methyl bromide is expected to be mobile in soil and sediment. Its vapor pressure also
suggests that volatilization from dry soil is likely. A Kh of 0.00734 atm-m3/mol suggests that
volatilization from moist soil and water is also likely (HSDB, 2013). Modeled river and lake
half-lives for volatilization are 3.0 hours and 3.9 days, respectively. A half-life of 20 days has
been determined for methyl bromide based on hydrolysis at pH 7 and 25 degrees C. A second
hydrolysis half-life of 26.7 days at 25 degrees C is also reported (pH not indicated). While
hydrolysis is identified as the primary degradation process in water, a half-life of 2.9 days was
observed for reaction of methyl bromide with aniline at 24 degrees C, a compound used to
simulate soil organic matter (HSDB, 2013). Due to methyl bromide's high volatility, it is
expected to volatilize from soil and surface water, resulting in low concentrations of methyl
bromide in drinking water (USEPA, 2006a).
Chapter 2 presents scales used by EPA to informally rank chemical contaminants' likely
mobility (understood as their tendency to partition to water rather than other media) and
persistence as "high," "moderate," or "low" based on physical and chemical properties (see
Exhibit 2-2 and Exhibit 2-3). For methyl bromide, a Koc of 9 to 22 L/kg and water solubility
values of 13,400 and 15,200 mg/L indicate a high likelihood of partitioning to water. The log
Kow of 1.19 indicates a moderate likelihood of partitioning to water, while a Kh of 0.00734 atm-
m3/mol indicates a low likelihood of partitioning to water. The hydrolysis half-lives of 20 and
26.7 days indicate moderate persistence. The modeled soil degradation half-life of 2.9 days
suggests low persistence in soil; however, this was demonstrated via simulated reaction with
aniline and not in field studies.
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7.3 Health Effects
7.3.1 Toxicokinetics
Absorption of methyl bromide following oral exposure is not well understood. No studies
relating to methyl bromide absorption in humans were located (ATSDR, 1992). However, in one
rat study, only 3 percent of the administered radiolabeled methyl bromide was found in the feces
(Medinsky et al., 1984). The authors of this study suggest that the majority (> 97 percent) of
methyl bromide is absorbed from the gastrointestinal tract. This study also finds that after
absorption, methyl bromide appears to distribute widely throughout the body, with the highest
levels of methyl bromide appearing in the liver and kidney.
Absorption via the inhalation route of exposure is expected to be lower than that via the
oral route. In inhalation studies in rats with radiolabeled methyl bromide, levels are highest in the
lung, adrenal, liver and kidney (Bond et al., 1985; Jaskot et al., 1988).
Overall, methyl bromide is metabolized readily and the majority of methyl bromide and
its metabolites are excreted within hours (ATSDR, 1992). Increased levels of methanol and
bromide after methyl bromide exposure in animals supports the conclusion that methyl bromide
is primarily metabolized via a nucleophilic elimination of bromide (HOH + CTbBr -> CH3OH +
H+ + Br" (Gargas and Andersen, 1982; Honma et al., 1985). Honma et al. (1985) found that while
peak levels of methyl bromide occurred after 1 hour of exposure in rats, concentrations of
bromine peaked 4-8 hours after exposure. Another mechanism for metabolism of methyl
bromide occurs via reaction with organic thiols (R-SH) to yield S-methyl derivatives (R-SH +
CH3Br -> R-SCH3 + H+ + Br") (ATSDR, 1992). S-methyl derivatives are metabolized to
methanethiol, which is, in turn, further metabolized to carbon dioxide and other unidentified
nonvolatile metabolites (ATSDR, 1992). The available data indicate that the rate and pattern of
excretion following oral exposure is similar to that following inhalation exposure (Medinsky et
al., 1984). Honma et al. (1985) measured the rate of methyl bromide elimination from the body
after inhalation exposure and found that half of the absorbed dose in adipose tissue and blood
was eliminated 30 minutes after exposure, while elimination from the brain and liver was slower.
7.3.2 Available Health Effects Assessments
Exhibit 7-8 presents a summary of the available health effects assessments for methyl
bromide. As indicated by the bolded row, the 2006 OPP Human Health Risk Assessment
(HHRA) (USEPA, 2006b) was selected for use in the calculation of the Health Reference Level
(HRL) (see Section 7.3.4 below for details on that calculation).
Exhibit 7-8: Available Health Effects Assessments for Methyl Bromide
Health
Assessment
Assessment
Year
Reference
Dose(RfD)
(mg/kg/
day)
Principal
study for
RfD
Cancer
Slope
Factor
(CSF)
(mg/kg/day)
-1
Principal
study for
CSF
Cancer
Descriptor
EPA Provisional
Peer-Reviewed
Toxicity Value
(PPRTV)
2007
No value
NA
No value
NA
I (inadequate
information to
assess
carcinogenic
potential)
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Health
Assessment
Assessment
Year
Reference
Dose(RfD)
(mg/kg/
day)
Principal
study for
RfD
Cancer
Slope
Factor
(CSF)
(mg/kg/day)
-1
Principal
study for
CSF
Cancer
Descriptor
EPA OPP Human
Health Risk
Assessment
(HHRA)
2006
2.2x10-2
MRID
44462501
(Mertens,
1997)
No value
NA
NL (not likely
to be
carcinogenic
in humans)
EPA Office of
Water (OW)
Health Advisory
(HA)
1989
1.4 x 10"3
Danse et al.,
1984
No value
NA
Group D (not
classifiable as
to human
carcinogenicity)
EPA Integrated
Risk Information
System (IRIS)
1988 for oral
RfD; 1989 for
carcinogenicity
assessment
1.4 x 10"3
Danse et al.,
1984
No value
NA
Group D (not
classifiable as
to human
carcinogenicity)
Agency for Toxic
Substances and
Disease Registry
(ATSDR)
1992
No value
NA
No value
NA
No value
7.3.3 Health Effects
Systemic (Non-cancer)
The limited number of studies investigating the oral toxicity of methyl bromide indicate
that the route of administration influences the toxic effects observed (USEPA, 2006b). The
forestomach of rats (the forestomach is an organ that is not present in humans) appears to be the
most sensitive target of methyl bromide when it is orally gavaged (ATSDR, 1992). Acute and
subchronic oral gavage studies in rats identified stomach lesions (Kaneda et al., 1998),
hyperemia (excess blood) (Danse et al., 1984), and ulceration (Boorman et al., 1986; Danse et
al., 1984) of the forestomach. However, forestomach effects were not observed in rats and
stomach effects were not observed in dogs that were chronically exposed to methyl bromide in
the diet, potentially because methyl bromide degrades to other bromide compounds in the food
(Mertens, 1997). Decreases in food consumption, body weight, and body weight gain were noted
in the chronic rat study when methyl bromide was administered in capsules (Mertens, 1997).
Previous EPA assessments (USEPA, 1988; USEPA, 1989a) selected the subchronic (13
week) rat study, Danse et al. (1984), as the critical study. These assessments were completed
before the publication of the chronic study (Mertens, 1997), which was chosen as a critical study
in later EPA assessments. In the Mertens 1997 study, male and female rats were dosed with
microencapsulated methyl bromide in the food for two years. The lowest observed adverse effect
levels (LOAELs) in the Mertens 1997 study were 11.1 mg/kg/day in male rats and 15.1
mg/kg/day in female rats, based on decreased body weight, body weight gain, and food
consumption. The no observed adverse effect levels (NOAELs) in the Mertens 1997 study were
2.2 mg/kg/day in male rats and 2.9 mg/kg/day in female rats. The NOAEL from Danse et al.
(1984) of 1.4 mg/kg/day (a time weighted average, 5/7 days, of the 2 mg/kg/day dose group) in
rats is based on severe hyperplasia of the stratified squamous epithelium in the forestomach in
the next highest dose group of 7.1 mg/kg/day (USEPA, 1989b). In ATSDR's 1992 Toxicological
Profile, a lower dose of 0.4 mg/kg/day is selected as the NOAEL because "mild focal
hyperemia" was observed at the 1.4 mg/kg/day dose level (ASTDR, 1992). It is worth noting that
authors of this study reported neoplastic changes in the forestomaches. However, EPA and others
(USEPA, 1985; Schatzow, 1984) re-evaluated the histological results, concluding that the lesions
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were hyperplasia and inflammation, not neoplasms. ATSDR notes that histological diagnosis of
epithelial carcinomas in the presence of marked hyperplasia is difficult (Wester and Kroes 1988;
ATSDR 1992). Additionally, the hyperplasia of the forestomach observed after 13 weeks of
exposure to bromomethane regressed when exposure ended (Boorman et al. 1986; ATSDR
1992). EPA IRIS applied a composite uncertainty factor (UF) of 1,000 to the NOAEL of 1.4
mg/kg/day from the Danse et al. (1984) study to account for intrahuman variability (10),
interspecies variability (10), and subchronic to chronic extrapolation (10) (USEPA, 1988). Danse
et al. (1984) has a lower NOAEL than the critical study selected by EPA's Office of Pesticides
for its Human Health Risk Assessment and is a subchronic study, rather than a chronic study.
Other assessments of methyl bromide from the Centers for Disease Control and
Prevention's (CDC's) ATSDR program and EPA's PPRTV program focus on toxicity from
inhalation exposure, not oral exposure. Additionally, USEPA (1988) states that "the neurological
effects reported after inhalation exposures have not been reported after oral exposures,"
indicating that route of exposure may influence the most sensitive adverse health endpoint.
Developmental/Reproductive
Limited data are available regarding the developmental or reproductive toxicity of methyl
bromide, especially via the oral route of exposure. ATSDR (1992) found no information on
developmental effects in humans with methyl bromide exposure. An oral developmental toxicity
study of methyl bromide in rats (doses of 3, 10, or 30 mg/kg/day) and rabbits (doses of 1, 3, or
10 mg/kg/day) found that there were no treatment-related adverse effects in fetuses of the treated
groups of either species (Kaneda et al., 1998). ATSDR's 1992 Toxicological Profile also did not
identify any LOAELs for rats or rabbits in this study. In rats exposed to 30 mg/kg/day, there was
an increase in fetuses having 25 presacral vertebrae; however, ATSDR notes that there were no
significant differences in the number of litters with this variation and the effect was not
exposure-related (ATSDR, 1992). No significant alterations in resorptions or fetal deaths,
number of live fetuses, sex ratio, or fetal body weights were observed in rats and no alterations in
the occurrence of external, visceral, or skeletal malformations or variations were observed in the
rabbits.
Some inhalation studies reported no effects on development or reproduction, but other
inhalation studies show adverse effects. For example, Hardin et al. (1981) and Sikov et al.
(1980)'s studies of rats and rabbits found no developmental effects, even when maternal toxicity
was severe (ATSDR, 1992). However, other developmental inhalation studies found increased
incidence of gallbladder agenesis, fused vertebrae, and decreased fetal body weights in offspring
(Breslin et al., 1990). Decreased pup weights were noted in a multigeneration study in rats
exposed to 30 ppm (Enloe et al., 1986). Reproductive effects were noted in intermediate-duration
inhalation studies in rats and mice (Eustis et al., 1988; Kato et al., 1986), which indicated that the
testes may undergo degeneration and atrophy at high exposure levels.
Cancer Data and Classification
The cancer classifications for methyl bromide have evolved over time. In EPA's 1989
IRIS Report, the Agency concluded that methyl bromide was Group D, "not classifiable as to
human carcinogenicity" from exposure via the oral route (USEPA, 1986; USEPA, 1989b).
Several years later, the 1992 National Toxicology Program (NTP) assessment and the 1992
ATSDR assessment both conclude that methyl bromide "has genotoxic potential," but NTP did
not find evidence of carcinogenicity in an inhalation mouse bioassay. NTP (1992) summarizes
the results of several genotoxicity tests, including the conclusions that methyl bromide has
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positive results, with and without S9 metabolic activation, in tests for the induction of gene
mutations in bacteria and plants. NTP (1992) also reports that "results from in vitro mammalian
cell assays with methyl bromide were negative for the induction of unscheduled
deoxyribonucleic acid (DNA) synthesis (McGregor, 1981; Kramers et al., 1985) and positive for
the induction of sister chromatid exchanges (Tucker et al., 1986)." ATSDR does not perform a
cancer risk assessment in their 1992 report.
In 2006, EPA's Office of Pesticides published a Human Health Risk Assessment
(HHRA) for methyl bromide, in which methyl bromide is classified as "not likely to be
carcinogenic to humans" (USEPA, 2006b). However, the assessment also states that EPA will
consider revisiting the cancer classification of methyl bromide when the results of new studies
are finalized, including an epidemiological study of pesticide applicators called the Agricultural
Health Study (discussed below).
One year after EPA's Office of Pesticides classified methyl bromide as "not likely" to be
a human carcinogen, an EPA PPRTV report stated that there is "inadequate information to assess
the carcinogenic potential" of methyl bromide in humans (USEPA, 2007). The PPRTV
assessment agrees with earlier NTP conclusions that the available data indicate that methyl
bromide can induce genotoxic and/or mutagenic changes. The PPRTV (USEPA, 2007)
assessment states that "methyl bromide is a very reactive methylating agent and readily
methylates thiols, thioether sulfurs, nitrogen in amino groups and rings, and oxygen atoms in
carboxylate ions and hydroxy groups (Vogel and Nivard, 1994)." The results of Gansewendt et
al. (1991) further support this conclusion, where male and female F344 rats exposed to radio-
labeled methyl bromide by inhalation or oral administration exhibited DNA adducts in the liver,
lung, stomach, and forestomach, with the highest activity in the stomach and forestomach.
Gansewendt et al. (1991) also isolated methylated bases from the hydrolyzed DNA. The PPRTV
assessment states that these results "clearly indicate methyl bromide is distributed throughout the
body and is capable of methylating DNA in vivo" (USEPA, 2007). However, the PPRTV
assessment summarizes the results of several studies in mice and rats that provide no evidence of
methyl bromide-induced carcinogenic changes (USEPA, 2007; NTP, 1992; Reuzel et al, 1987;
ATSDR, 1992).
In the time since EPA's last assessment (USEPA, 2007), the Agricultural Health Study
referenced in the EPA OPP's 2006 Human Health Risk Assessment for methyl bromide was
published (Barry et al., 2012). This epidemiology study found that there was a significant
monotonic exposure-dependent increase in stomach cancer risk among 7,814 applicators of
methyl bromide (Barry et al., 2012). In OPP's 2018 Draft Human Health Risk Assessment for
Methyl Bromide (USEPA, 2018c), OPP reviews all of the epidemiological studies for methyl
bromide, including the Barry et al., 2012 Agricultural Health Study. OPP concludes that "based
on the review of these studies, there is insufficient evidence to suggest a clear associative or
causal relationship between exposure to methyl bromide and carcinogenic or non-carcinogenic
health outcomes."
Potentially Sensitive Groups/Lifestages
According to OPP's 2006 HHRA (USEPA, 2006b), methyl bromide has not yet been
tested for endocrine disrupting effects. There are limited data on the toxicity of methyl bromide
in children, and no availability of data regarding toxicity of methyl bromide in children via the
oral route of exposure. According to ATSDR (1992) and the EPA OPP assessment (USEPA,
2006b), no studies suggest that a specific subpopulation may be more susceptible to methyl
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bromide, though there is little information about susceptible lifestages or subpopulations when
exposed via the oral route.
7.3.4 Basis of the HRL
For the HRL, EPA selected a Reference Dose (RfD) of 0.022 mg/kg/day for methyl
bromide, based on a 2006 EPA Office of Pesticide Programs (OPP) HHRA (USEPA, 2006b).
The assessment identified Mertens (1997), assigned Master Record Identification Number
(MRID) 44462501, as the critical study. This is an unpublished study. Based on descriptions of
the study in OPP documents, the study was of chronic duration (2 years) with 4 groups of male
rats and 4 groups of female rats treated orally via encapsulated methyl bromide. Mertens (1997)
identified decreased bodyweight (BW), decreased rate of BW gain, and decreased food
consumption as the critical effects in rats orally exposed to methyl bromide (USEPA, 2006b).
The NOAEL was 2.2 mg/kg/day and the LOAEL was 11.1 mg/kg/day.
The RfD derived in 2006 OPP Human Health Assessment is 0.022 mg/kg/day, based on
the point of departure (POD) of 2.2 mg/kg/day (the NOAEL) and a combined UF of 100 for
interspecies variability (10) and intraspecies variability (10). No benchmark dose modeling was
performed. The final RfD used to derive the HRL is 0.022 mg/kg/day. Because the critical
effects of decreased body weight, decreased rate of body weight gain, and decreased food
consumption in this study are not specific to a sensitive subpopulation or life stage, the target
population of the general adult population was selected in deriving the HRL for regulatory
determination. The OPP assessment conducted additional exposure assessments for lifestages
that may increase exposure to methyl bromide and concluded that no lifestages have expected
exposure greater than 10% of the cPAD, including children.
BW
HRL = RfD* — *RSC
mq/kq 80 kq
HRL = 0.022 , * * 20%
day 2 ^
day
mg [ig
HRL = 0.1408 -j- = 140.8 ^
L L
HRL = 100 — (rounded)
L
RfD = Reference Dose (mg/kg/day); toxicity value selected based on protocol hierarchy
BW = Body weight (kg); based on adult default value of 80 kg
DWI = Drinking Water Intake (L/day); based on adult default value of 2.5 L/day
RSC = Relative Source Contribution, or the level of exposure believed to result from
drinking water when compared to other sources (e.g., food, ambient air), is 20 percent
when used for HRL derivation.
7.3.5 Health Effects Data Gaps
Though there are data gaps regarding methyl bromide's oral toxicity, the volatility of
methyl bromide under environmental conditions indicates that inhalation is likely to be the main
route of environmental exposure. More research is needed to assess the carcinogenic potential of
methyl bromide via the inhalation and oral routes of exposure.
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7.4 Occurrence
This section presents data on the occurrence of methyl bromide in ambient water and
drinking water in the United States. As described in Section 7.3, an HRL of 100 |ig/L was
calculated for methyl bromide based on non-carcinogenic effects. HRLs are risk-derived
concentrations against which EPA evaluates the occurrence data to determine if contaminants
occur at levels of potential public health concern. Occurrence data from various sources
presented below are analyzed with respect to the HRL and one-half the HRL. When possible,
estimates of the population exposed at concentrations above the HRL and above one-half the
HRL are presented.
For additional background information about data sources used to evaluate occurrence,
please refer to Chapter 2.
7.4.1 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. Contaminant
occurrence in ambient water provides information on the potential for contaminants to adversely
affect drinking water supplies. Occurrence data for methyl bromide in ambient water are
available from the USGS National Water-Quality Assessment (NAWQA) program, the USGS
National Water Information System (NWIS) database, EPA's legacy Storage and Retrieval Data
System (STORET) data available through the Water Quality Portal (WQP), and several
published USGS studies. Additional ambient water data collected in connection with finished
drinking water data are presented in Section 7.4.2.
United States Geological Survey (USGS) National Water-Quality Assessment (NAWQA)
Ambient Water Analyses
USGS instituted the NAWQA program in 1991 to examine ambient water quality status
and trends in the United States. The NAWQA program generates high quality contaminant
occurrence and other water quality parameter data for significant watersheds and aquifers across
the nation. The program collects data on surface water and groundwater chemistry, hydrology,
land use, stream habitat, and aquatic life in parts or all of nearly all 50 States. The program is
designed to apply nationally consistent methods to provide a uniform basis for contaminant
occurrence comparisons and assessments among study basins across the country and over time.
The occurrence assessments can also serve to facilitate interpretation of natural and
anthropogenic factors affecting national water quality. For more detailed information on the
NAWQA program design and implementation, refer to Leahy and Thompson (1994) and
Hamilton et al. (2004).
The process of sampling, analysis, and data synthesis is divided into cycles of
approximately ten years: Cycle 1 covered 1991-2001, Cycle 2 covered 2002-2012, and Cycle 3 is
ongoing and covers 2013-2023. Study units are sampled and analyzed on a staggered schedule
within each cycle. Each NAWQA cycle begins with a two-year startup phase for planning and
retroactive analysis, followed by a three-year intensive data collection phase, and finally a five-
year phase for analyzing the data, developing reports, and continuing a low level of monitoring
(NRC, 2012).
During Cycle 1 (1991-2001), 51 study units were sampled. Data were gathered from
6,307 wells from 272 groundwater networks or clusters and from 6,400 sampling points at 505
surface water monitoring sites, primarily rivers and streams but also some lakes and reservoirs
(NRC, 2002). In Cycle 2 (2002-2012), the number of study units was reduced from 51 to 42
(NRC, 2012). Long-term stream monitoring was established at 113 streams, representing 8 major
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river basins. Long-term groundwater monitoring was established at sites representing 20
principal aquifers with more than 10 to 15 years of consistent monitoring data available (Rowe et
al., 2013).
Sampling for Cycle 3 is currently underway (2013-2023). Surface water monitoring will
be conducted at 313 sites, increased from 113 sites in Cycle 2 (Rowe et al., 2013). Groundwater
assessments in Cycle 3 will be designed to evaluate status and trends at the principal aquifer
(PA) and national scales. Assessments are planned in 24 PAs that account for the majority of
current and future national groundwater use for drinking water. Data available through 2017 are
presented in this report. For more details on the Cycle 3 sampling design, refer to Rowe et al.,
(2010 and 2013).
EPA's analysis of the NAWQA data is a simple, non-parametric occurrence analysis that
provides summary statistics to characterize contaminant occurrence. EPA calculated detection
frequencies as the percentage of samples and the percentage of sites with at least one detection,
without any censoring or weighting. (A detection is an analytical result equal to or greater than
the reporting level.) EPA reported the minimum and maximum detected concentrations and
calculated other descriptive statistics including the median, 90th percentile, and 99th percentile
concentrations (based only on samples with detections). Reporting levels varied over time during
the NAWQA program. In some cases, therefore, the minimum concentration reported as a
detection could be lower than the highest reporting level.
Exhibit 7-9 through Exhibit 7-11 present analyses of the methyl bromide NAWQA data,
downloaded from the Water Quality Portal in September 2018 (WQP, 2018). In all three cycles,
methyl bromide was detected in fewer than 1 percent of samples from fewer than 2 percent of
sites. (Some sites were sampled in more than one cycle.) No detections were greater than the
HRL in any of the three cycles. The median concentrations based on detections were 0.5 |ig/L
and 0.8 |ig/L in Cycle 1 and Cycle 3, respectively. There were no detections in Cycle 2. As noted
above, NAWQA data are ambient water data, not finished drinking water data.
Note that there may be some overlap between the NAWQA data assessment presented
here and summaries of individual NAWQA studies presented below.
Exhibit 7-9: Methyl Bromide NAWQA Data - Summary of Detected Concentrations
Site Type
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Cycle 1 (1991 -2001)
Groundwater
0.1
0.30
0.42
0.49
0.5
Surface Water
34
34
34
34
34
All Sites
0.1
0.50
24
33
34
Cycle 2 (2002-2012)
Groundwater
ND
ND
ND
ND
ND
Surface Water
ND
ND
ND
ND
ND
All Sites
ND
ND
ND
ND
ND
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Site Type
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Cycle 3 (2013-2017)
Groundwater
0.2
0.2
0.2
0.2
0.2
Surface Water
1.4
1.4
1.4
1.4
1.4
All Sites
0.2
0.8
1.2
1.4
1.4
Source: WQP, 2018
Exhibit 7-10: Methyl Bromide NAWQA Data - Summary of Samples
Site Type
No. of
Samples
Detection Frequency
(detections are results > reporting level)
No. of
Samples
with
Detections
%
Samples
with
Detections
No. of
Samples
with
Detections
> 1/2 HRL
%
Samples
with
Detections
> 1/2 HRL
No. of
Samples
with
Detections
> HRL
%
Samples
with
Detections
> HRL
Cycle 1 (1991 -2001)
Groundwater
4,846
2
0.04%
0
0.00%
0
0.00%
Surface Water
1,483
1
0.07%
0
0.00%
0
0.00%
All Sites
6,329
3
0.05%
0
0.00%
0
0.00%
Cycle 2 (2002-2012)
Groundwater
4,989
0
0.00%
0
0.00%
0
0.00%
Surface Water
532
0
0.00%
0
0.00%
0
0.00%
All Sites
5,521
0
0.00%
0
0.00%
0
0.00%
Cycle 3 (2013-2017)
Groundwater
1,554
1
0.06%
0
0.00%
0
0.00%
Surface Water
161
1
0.62%
0
0.00%
0
0.00%
All Sites
1,715
2
0.12%
0
0.00%
0
0.00%
Source: WQP, 2018
Exhibit 7-11: Methyl Bromide NAWQA Data - Summary of Sites
Site Type
No. of
Sites
Detection Frequency
(detections are results > reporting level)
No. of
Sites with
Detections
% Sites
with
Detections
No. of
Sites with
Detections
> 1/2 HRL
% Sites
with
Detections
> 1/2 HRL
No. of
Sites with
Detections
> HRL
% Sites
with
Detections
> HRL
Cycle 1 (1991 -2001)
Groundwater
4,425
2
0.05%
0
0.00%
0
0.00%
Surface Water
187
1
0.53%
0
0.00%
0
0.00%
All Sites
4,612
3
0.07%
0
0.00%
0
0.00%
Cycle 2 (2002-2012)
Groundwater
3,200
0
0.00%
0
0.00%
0
0.00%
Surface Water
56
0
0.00%
0
0.00%
0
0.00%
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Detection Frequency
(detections are results > reporting level)
Site Type
No. of
Sites
No. of
Sites with
Detections
% Sites
with
Detections
No. of
Sites with
Detections
> 1/2 HRL
% Sites
with
Detections
> 1/2 HRL
No. of
Sites with
Detections
> HRL
% Sites
with
Detections
> HRL
All Sites
3,256
0
0.00%
0
0.00%
0
0.00%
Cycle 3 (2013-2017)
Groundwater
1,481
1
0.07%
0
0.00%
0
0.00%
Surface Water
54
1
1.85%
0
0.00%
0
0.00%
All Sites
1,535
2
0.13%
0
0.00%
0
0.00%
Source: WQP, 2018
NAWQA Volatile Organic Compound (VOC) National Synthesis: Random and
Focused VOC Surveys, 1999-2001
Through a series of National Synthesis efforts, the USGS NAWQA program prepares
comprehensive analyses of data on topics of particular concern. These National Synthesis
assessments aggregate NAWQA contaminant occurrence and water quality parameter data from
individual study units and other sources to provide a national overview.
The Volatile Organic Compound (VOC) National Synthesis began in 1994. The most
comprehensive VOC National Synthesis reports to date are one random survey and one focused
survey funded by the Water Research Foundation (WRF) (formerly known as AwwaRF) and
carried out by the USGS in collaboration with the Metropolitan Water District of Southern
California and Oregon Health & Science University. The random survey (Grady, 2002) targeted
surface waters and groundwaters used as source water by community water systems (CWSs).
Samples were taken from the source waters of 954 CWSs in 1999 and 2000. The random survey
was designed to be nationally representative of CWS source waters. In the focused survey
(Delzer and Ivahnenko, 2003), 451 samples were taken from source waters serving 134 CWSs
between 1999 and 2001. The focused survey was designed to provide insight into temporal
variability and anthropogenic factors associated with VOC occurrence. Both surveys reported the
results of multiple analytes, including methyl bromide, at a common reporting level of 0.2 (J,g/L.
Details of the monitoring plan for these two studies, including detection limits are provided by
Ivahnenko et al. (2001).
The random survey sampled groundwater and surface water sources used by 954
geographically representative CWSs in different size categories (Grady, 2002). At a reporting
level of 0.2 (J,g/L, the national random survey of source waters (Grady, 2002) found methyl
bromide in 2 (0.21 percent of all samples, 0.17 percent of groundwater samples, and 0.28 percent
of surface water samples). The groundwater detection was 6.4 |ig/L and the surface water
detection was 0.22 |ig/L.
The focused survey investigated 134 CWS sources (56 surface water and 78
groundwater) between 1999 and 2001 (Delzer and Ivahnenko, 2003). These surface waters and
groundwaters were chosen because they were suspected or known to contain methyl tertiary
butyl ether (MTBE). At a reporting level of 0.2 (J,g/L, the national focused survey (Delzer and
Ivahnenko, 2003) found methyl bromide in 0% of the CWS source waters sampled. In addition,
the focused survey provided results for methyl bromide below the reporting level. At levels as
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low as the method detection limit (0.084 (J,g/L), methyl bromide was found in 3.0 percent of the
CWSs source waters sampled (3.8 percent of groundwater sites and 1.8 percent of surface water
sites). Detected concentrations ranged from 0.09 [j,g/L to 0.11 |ig/L (Delzer and Ivahnenko,
2003).
NA WQA Volatile Organic Compounds (VOC) National Synthesis: Compilation of
Historical VOC Monitoring Data, 1985-1995
The VOC National Synthesis also includes a compilation of historical VOC monitoring
data from multiple studies (Squillace et al., 1999). These data were collected between 1985 and
1995 from 2,948 drinking water and non-drinking water wells in both rural and urban areas.
Sampling was done by local, state, and federal agencies, and data were reviewed by USGS to
ensure they met data quality criteria.
Multiple investigators collected methyl bromide samples from 335 urban wells and 1,186
rural wells. At a reporting level of 0.2 (J,g/L, the detection frequency for methyl bromide was 0
percent in urban areas and 0.05 percent in rural areas. The single detection in a rural area was 0.5
Hg/L-
National Water Information System (NWIS) Data
The National Water Information System (NWIS) is the Nation's principal repository of
water resources data USGS collects from more than 1.5 million sites (USGS, 2016). NWIS-Web
is the general online interface to the USGS NWIS database. Discrete water-sample and time-
series data are available from sites in all 50 states, including 5 million water samples with 90
million water-quality results. All USGS water quality and flow data are stored in NWIS,
including site characteristics, streamflow, groundwater level, precipitation, and chemical
analyses of water, sediment, and biological media, though not all parameters are available for
every site. NWIS houses the NAWQA data and includes other USGS data from unspecified
projects. NWIS contains many more samples at many more sites than the NAWQA Program.
Although NWIS is comprised of primarily ambient water data, some finished drinking water data
are included as well. This section presents analyses of non-NAWQA data in NWIS, downloaded
from the Water Quality Portal in December 2017 (WQP, 2017). These data do not overlap with
the results presented in Exhibit 7-9 through Exhibit 7-11.
The results of the non-NAWQA NWIS methyl bromide analyses are presented in Exhibit
7-12. Methyl bromide was detected in approximately 0.1 percent of samples (15 out of 19,227
samples) and at approximately 0.1 percent of sites (13 out of 8,997 sites). The median
concentration based on detections was equal to 0.600 |ig/L. (Note that the NWIS data are
presented as downloaded; potential outliers were not evaluated or excluded from the analysis.)
Exhibit 7-12: Methyl Bromide NWIS Data, 1991 - 2016
Site Type
Detection Frequency
(detections are results > reporting level)
Concentration Values
(of detections, in |jg/L)
No. of
Samples
No. of
Samples
with
Detections
No.
of
Sites
No. of
Sites with
Detections
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Groundwater
15,883
8
8,122
7
0.25
0.55
240,000
1,100,000
1,200,000
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Site Type
Detection Frequency
(detections are results > reporting level)
Concentration Values
(of detections, in |jg/L)
No. of
Samples
No. of
Samples
with
Detections
No.
of
Sites
No. of
Sites with
Detections
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Surface
Water
3,320
7
889
6
0.2
0.80
2.22
4.81
5.1
Finished
Water
24
0
20
0
ND
ND
ND
ND
ND
All Sites
19,227
15
8,997
13
0.2
0.60
3.55
1,020,000
1,200,000
Source: WQP, 2017
Storage and Retrieval (STORET) Data / Water Quality Portal (WQP)
From its launch in 1999 until it was decommissioned in June 2018, EPA's STORET Data
Warehouse was collaboratively populated with raw biological, chemical, and physical data from
surface water and groundwater sampling by federal, state and local agencies, Native American
tribes, volunteer groups, academics, and others. Legacy STORET data are accessible through the
Water Quality Portal (WQP): https://www.waterqualitvdata.us/portal/.
STORET data are from monitoring locations in all 50 states as well as multiple territories
and jurisdictions of the United States. Most data are from ambient waters, but in some cases
finished drinking water data are included as well. STORET's data quality limitations include
variations in the extent of national coverage and data completeness from parameter to parameter.
Data may have been collected as part of targeted, rather than randomized, monitoring.
This section presents analyses of STORET data, downloaded from the WQP in December
2017 (WQP, 2017). EPA reviewed STORET groundwater data from wells and surface water data
from lakes, rivers/streams, and reservoirs (WQP, 2017). The WQP also included public water
system (PWS) data from four states (Indiana, Missouri, Ohio, and Washington); EPA reviewed
these as well (WQP, 2017). It is unclear if the PWS data were collected prior to or subsequent to
treatment.
The results of the STORET analysis for methyl bromide are presented in Exhibit 7-13
through Exhibit 7-15. These methyl bromide samples were collected between 1985 and 2016. Of
the 5,202 sites sampled, 2,523 (48.5 percent) reported detections of methyl bromide. Detected
concentrations ranged as high as 5,000 |ig/L. The 90th percentile concentration of detections was
equal to 5.0 |ig/L. The minimum detected concentration may be indicative of the reporting levels
used. (A minimum value of zero, on the other hand, could represent a detection that was entered
into the database as a non-numerical value (e.g., "Present").)
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Exhibit 7-13: Methyl Bromide STORET Data - Summary of Detected
Concentrations
Source Water Type
Concentration Value of Detections (|jg/L)
Minimum1
Median
90th Percentile
Maximum
Groundwater
0
5.0
5.0
5,000
Surface Water
0
0.5
0.5
110
Total
0
5.0
5.0
5,000
PWS
0
0
0
2
Source: WQP, 2017
1A minimum value of zero may represent a detection that was entered into the database as a non-numerical value
(e.g., "Present").
Exhibit 7-14: Methyl Bromide STORET Data - Summary of Samples and Sites
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Total
Number
of Sites
Sites with Detections
Number
Percent
Number
Percent
Groundwater
31,039
15,559
50.13%
3,910
2,111
53.99%
Surface Water
18,128
1,363
7.52%
1,292
412
31.89%
Total
49,167
16,922
34.42%
5,202
2,523
48.50%
PWS
1,279
1,090
85.22%
187
186
99.47%
Source: WQP, 2017
Exhibit 7-15: Methyl Bromide STORET Data - Summary of States
Source Water
Type
Total
Number of
States
States with Detections
Number
Percent
Groundwater
14
9
64.29%
Surface Water
32
12
37.50%
Total1
33
15
45.45%
PWS
2
2
100.00%
Source: WQP, 2018
1 The number of states with groundwater data plus the number of
states with surface water data may not equal the "Total" number of
states providing data because some states provided both
groundwater and surface water data.
Additional Ambient Water Studies
Methyl bromide data are available from a variety of USGS stormwater studies. For the
National Highway Runoff Data and Methodology Synthesis, USGS conducted a review of 44
highway and urban runoff studies conducted between the 1970s and the 1990s (Lopes and
Dionne, 1998). Three of these studies report results for methyl bromide. Note that the data from
these studies might also be included in the NWIS results presented earlier.
The three studies with methyl bromide results were stormwater studies conducted in
specific major metropolitan areas in connection with National Pollutant Discharge Elimination
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System (NPDES) permitting. In metropolitan Phoenix (Maricopa County), USGS collected 35
samples from five drainage basins, and the City of Phoenix collected an additional 26 samples
from seven sites (Lopes et al., 1995). In Colorado Springs, USGS collected 35 samples from five
sites (von Guerard and Weiss, 1995). In Dallas-Fort Worth, 181 samples were collected from 26
stormwater drainage basins (Baldys et al., 1998). Methyl bromide was not detected in any
samples collected in Phoenix, Colorado Springs or Dallas-Fort Worth.
7.4.2 Occurrence in Drinking Water
Data sources reviewed by the Agency for information on contaminant occurrence in
drinking water included: EPA's first, second, and third Unregulated Contaminant Monitoring
Rules (UCMR 1, UCMR 2, UCMR 3); Rounds 1 and 2 of the Agency's Unregulated
Contaminant Monitoring (UCM) program that preceded the Unregulated Contaminant
Monitoring Rule (UCMR); EPA's Information Collection Rule; EPA's National Inorganics and
Radionuclides Survey (NIRS); and a range of others as discussed in Chapter 2. Among the
sources reviewed, the following had data and information on methyl bromide occurrence in
drinking water. These data and information are discussed in this section.
• EPA's Third Unregulated Contaminant Monitoring Rule (UCMR 3).
EPA's Unregulated Contaminant Monitoring (UCM) program, Rounds 1 and 2.
State drinking water monitoring programs.
USGS source water and drinking water studies.
Additional studies from the literature.
Note that there may be some overlap, as sources with different purposes and audiences
may have reported the same underlying data. UCMR 3 and UCM Rounds 1 and 2 are national
data sources. Other data sources profiled in this section are considered "supplemental" sources.
Also note that the presentation of NWIS and STORET results in the ambient water section,
above, includes some finished water data and/or miscellaneous data from PWSs.
Primary Data Sources
EPA's Third Unregulated Contaminant Monitoring Rule (UCMR 3)
UCMR 3 monitoring, designed to provide nationally representative contaminant
occurrence data, was conducted from 2013 through 2015. UCMR 3 List 1 Assessment
Monitoring occurrence data are available for methyl bromide. For UCMR 3, all large and very
large PWSs (serving between 10,001 and 100,000 people and serving more than 100,000 people,
respectively), plus a statistically representative national sample of 800 small PWSs (serving
10,000 people or fewer), were required to conduct Assessment Monitoring during a 12-month
period between January 2013 and December 2015.1 Surface water (and groundwater under the
direct influence of surface water (GWUDI)) sampling points were monitored four times during
the applicable year of monitoring, and groundwater sampling points were monitored twice
during the applicable year of monitoring. See USEPA (2012) and USEPA (2019c) for more
information on the UCMR 3 study design and data analysis.
The design of UCMR 3 permits estimation of national occurrence by multiplying the total
number of systems (or population served) in the nation in a system size category by the percent
of systems expected to exceed a specified threshold. An extrapolation methodology is applied to
1 Only 799 small systems submitted Assessment Monitoring results.
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small systems because not all small systems were required to participate in the UCMR 3
Assessment Monitoring. Because all large and very large systems were required to participate in
the UCMR 3 Assessment Monitoring, national estimates of occurrence in these size categories
can be done using survey census figures rather than extrapolation. Total national occurrence is
estimated by summing the extrapolated figures for small systems and the census figures for the
large and very large systems.
Exhibit 7-16 through Exhibit 7-18 provide an overview of methyl bromide occurrence
results from UCMR 3 Assessment Monitoring. Laboratories participating in UCMR 3 were
required to report values at or above minimum reporting levels (MRLs) defined by EPA. The
MRLs are established to ensure reliable and consistent results from the array of laboratories
needed for a national monitoring program and are set based on the capability of multiple
commercial laboratories prior to the beginning each UCMR round. The MRL used for methyl
bromide in the UCMR 3 survey was 0.2 |ig/L (77 FR 26072; USEPA, 2012). Exhibit 7-16 shows
a statistical summary of methyl bromide concentrations by system size and source water type
(including the minimum, median, 90th percentile, 99th percentile, and maximum).
Exhibit 7-17 presents a sample-level summary of the results. Exhibit 7-18 shows system-
level results, including national extrapolations, for detections greater than or equal to the MRL
threshold.
As noted above, UCMR 3 monitoring was required at a representative sample of small
systems and at all large and very large systems. As a reminder that the figures from large and
very large systems represent a census of systems in those categories, results in those categories
are labelled "CENSUS" in Exhibit 7-16 through Exhibit 7-18. No extrapolation was necessary in
these categories, as it was for the small systems, to derive national estimates of occurrence in
these exhibits. National estimates of occurrence are reported separately in each system size and
source water category, and also in aggregate.
A total of 36,848 finished water samples for methyl bromide were collected from 4,916
systems. Methyl bromide was measured > MRL in 0.31 percent of UCMR 3 samples. Reported
methyl bromide concentrations for these "positive" results ranged from 0.2 |ig/L (the MRL) to
6.93 |ig/L. Of 4,916 systems, 49 (1.0 percent of systems, serving 0.8 percent of the PWS-served
population) reported at least one detection. Extrapolating these findings suggests that an
estimated 1,200 PWSs serving 2.6 million people nationally would have at least one methyl
bromide detection. UCMR 3 Assessment Monitoring data showed no occurrence above the one-
half HRL or HRL thresholds.
Exhibit 7-16: Methyl Bromide Data from UCMR 3 Assessment Monitoring -
Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (in |Jg/L) > MRL of 0.2 |jg/L
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Small Systems (serving < 10,000 people)
Groundwater
0.2
0.9
4.7
6.6
6.93
Surface Water
ND
ND
ND
ND
ND
All Small Systems
0.2
0.9
4.7
6.6
6.93
7-27
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Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide
January 2021
Source Water Type
Concentration Value of Detections (in |Jg/L) > MRL of 0.2 |jg/L
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
0.2
0.6
2.0
5.1
6.18
Surface Water
0.2
0.4
0.7
0.9
0.92
All Large Systems
0.2
0.5
1.4
4.7
6.18
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
0.2
0.3
0.4
0.4
0.4
Surface Water
0.2
0.3
1.5
2.2
2.2
All Very Large Systems
0.2
0.3
1.2
2.2
2.2
All Systems
All Water Systems
0.2
0.5
3.2
6.1
6.93
Source: USEPA, 2017c
Exhibit 7-17: Methyl Bromide National Occurrence Measures Based on UCMR 3
Assessment Monitoring Data - Summary of Samples
Source Water Type
Total # of
Samples
Samples with Detections
> MRL (0.2 |jg/L)
Samples with Detections
> 1/2 HRL (50 |jg/L)
Samples with Detections
> HRL (100 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Small Systems (serving < 10,000 people)
Groundwater
1,849
28
1.51%
0
0.00%
0
0.00%
Surface Water
1,417
0
0.00%
0
0.00%
0
0.00%
All Small Systems
3,266
28
0.86%
0
0.00%
0
0.00%
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
11,654
49
0.42%
0
0.00%
0
0.00%
Surface Water
14,808
21
0.14%
0
0.00%
0
0.00%
All Large Systems
26,462
70
0.26%
0
0.00%
0
0.00%
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
2,009
2
0.10%
0
0.00%
0
0.00%
Surface Water
5,111
15
0.29%
0
0.00%
0
0.00%
All Very Large
Systems
7,120
17
0.24%
0
0.00%
0
0.00%
All Systems
All Water Systems
36,848
115
0.31%
0
0.00%
0
0.00%
Source: USEPA, 2017c
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Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide
January 2021
Exhibit 7-18: Methyl Bromide National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data -
Summary of System and Population Served Data - Detections
Source Water Type
UCMR 3 Sample
Number With At Least One
Detection > MRL (0.2 ng/L)
Percent With At Least One Detection
> MRL (0.2 pig/L)
National Inventory1
National Estimate2
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems
serving < 10,000 people)
Groundwater
527
1,498,845
11
28,199
2.09%
1.88%
55,700
38,730,597
1,160
729,000
Surface Water
272
1,250,215
0
0
0.00%
0.00%
9,728
20,007,917
0
0
All Small Systems
799
2,749,060
11
28,199
1.38%
1.03%
65,428
58,738,514
1,160
729,000
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
1,451
37,113,173
19
403,382
1.31 %
1.09%
1,470
37,540,614
19
403,000
Surface Water
2,258
69,538,817
12
353,687
0.53%
0.51%
2,310
70,791,005
12
354,000
All Large Systems
3,709
106,651,990
31
757,069
0.84%
0.71%
3,780
108,331,619
31
757,000
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
68
16,355,951
2
388,285
2.94%
2.37%
68
16,355,951
2
388,000
Surface Water
340
115,158,260
5
714,956
1.47%
0.62%
343
120,785,622
5
715,000
All Very Large Systems
408
131,514,211
7
1,103,241
1.72%
0.84%
411
137,141,573
7
1,100,000
All Systems
All Water Systems
4,916
240,915,261
49
1,888,509
1.00%
0.78%
69,619
304,211,706
1,200
2,590,000
Source: USEPA, 2017c
1 The small system national inventory numbers for systems and population served by systems were derived from a freeze of the December 2010 Safe Drinking Water
Information System / Federal version (SDWIS/Fed) data. These counts are based on all community and non-transient non-community water systems that served 10,000
people or fewer. All large and very large systems were required to conduct UCMR 3 Assessment Monitoring; thus, the national inventory numbers for the large and very
large systems are based on the number of systems expected to complete UCMR 3 monitoring. SDWIS/Fed inventory data from 2010 were used for the UCMR 3
national extrapolations as these data were consistent with the UCMR 3 inventory data at the timeframe of the UCMR 3 sample design.
2 National estimates for the small systems are generated by multiplying the UCMR 3 national statistical sample findings of system/population percentages and national
system/population inventory numbers for PWSs. National estimates for the large and very large systems are based directly on the UCMR 3 results, since this was a
census. Due to rounding, some calculations may appear to be slightly off.
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Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide
January 2021
Unregulated Contaminant Monitoring (UCM) Data
In 1987, EPA initiated the UCM program, which collected contaminant occurrence data
from drinking water at PWSs. This program was implemented in two rounds. The first round of
UCM monitoring (UCM Round 1) generally extended from 1988 to 1992 and included
monitoring for 34 VOCs. The second round of UCM monitoring (UCM Round 2) generally
extended from 1993 to 1997 and included monitoring for 13 synthetic organic compounds
(SOCs) and sulfate in addition to the 34 VOCs from UCM Round 1 monitoring. All the
monitored contaminants were unregulated at the time of monitoring. A total of 38 states provided
contaminant occurrence data under UCM Round 1, and 34 states provided data under UCM
Round 2. Samples were analyzed for methyl bromide under both UCM Round 1 and Round 2.
The contaminant occurrence data submitted under the UCM monitoring reflected neither
a census nor a statistically representative sample. Therefore, EPA assessed potential biases in the
data and developed a "national cross-section" separately from the UCM Round 1 and Round 2
data submitted by the states. The UCM Round 1 national cross-section of data from 24 states
consists of more than 3.3 million analytical results from approximately 22,000 systems. The
UCM Round 2 national cross-section of data from 20 states consists of more than 3.7 million
analytical results from approximately 27,000 systems. While EPA recognizes that some
limitations exist, the Agency believes that the national cross-sections are indicative of national
occurrence and provide a reasonable estimate of the overall distribution and the central tendency
of contaminant occurrence across the United States. For more details on the UCM Round 1 and 2
data and the occurrence estimation methodology, refer to USEPA (2001a), USEPA (2003), and
USEPA (2008b).
Exhibit 7-19 through Exhibit 7-21 present a summary of the occurrence data from UCM
Rounds 1 and 2 for methyl bromide. In Round 1, methyl bromide was detected at 0.77 percent of
PWSs, affecting 8.51 percent of the population served in the cross-section analysis, and in 0.80
percent of PWSs, affecting 8.36 percent of the population in the all-states analysis. The
minimum detection in UCM Round 1 was 0.07 |ig/L in both the all-states and the cross-section
states analyses. In Round 2, methyl bromide was detected at 0.75 percent of PWSs, affecting
7.72 percent of the population served in the cross-section analysis, and in 0.68 percent of PWSs,
affecting 6.48 percent of the population in the all-states analysis. In Round 2, the minimum
detection was 0.09 |ig/L in both the all-states and the cross-section analysis. More detections of
methyl bromide were found in groundwater systems than surface water systems (though a larger
proportion of surface water systems had detections). No methyl bromide detections were greater
than one-half the HRL or the HRL. Minimum detected concentrations are reported in Exhibit
7-19; these minimum values may be indicative of reporting levels used.
To calculate national extrapolations, the percent of systems (or population served)
estimated to exceed a specified threshold is multiplied by the total number of systems (or
population served) in the nation. However, national extrapolations based on UCM data should be
interpreted with caution, because neither "all-states" data nor cross-section data constitute
statistically representative samples. See Chapter 2 for additional information on national
extrapolations. The results of national extrapolations are presented in Exhibit 7-21.
Because Round 1 and Round 2 involve different groups of states, conclusions about
temporal trends cannot necessarily be drawn from comparison of findings from the two Rounds.
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Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide
January 2021
(Temporal trends could, however, be inferred from state-level findings in the case of states with
findings from both Rounds.)
Exhibit 7-19: Methyl Bromide Occurrence Data from UCM Rounds 1 and 2 -
Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (|jg/L)
Minimum
Median
90th
99th Percentile
Maximum
UCM Round 1 - 24-State Cross-Section (1988-1992)
Groundwater
0.07
1.00
9.00
33.4
43
Surface Water
0.1
1.10
10.7
14.2
15.2
All Systems
0.07
1.00
10.6
32.9
43
UCM Round 1 - All States (1988-1992)
Groundwater
0.07
1.00
8.40
33.2
43
Surface Water
0.1
1.10
11.0
40.5
49.9
All Systems
0.07
1.00
10.2
36.6
49.9
UCM Round 2 - 20-State Cross-Section (1993-1997)
Groundwater
0.09
1.60
7.90
20.9
31.2
Surface Water
0.1
1.51
10.0
31.7
38.1
All Systems
0.09
1.60
8.06
25.1
38.1
UCM Round 2 - All States (1993-1997)
Groundwater
0.09
1.60
7.75
20.8
31.2
Surface Water
0.1
1.57
9.78
31.2
38.1
All Systems
0.09
1.60
7.96
24.6
38.1
Source: USEPA, 2001b
Exhibit 7-20: Methyl Bromide Occurrence Data from UCM Rounds 1 and 2 -
Summary of Samples
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Samples with
Detections
> 1/2 HRL (50 |jg/L)
Samples with
Detections
> HRL (100 |jg/L)
Number
Percent
Number
Percent
Number
Percent
UCM Round 1 - 24-State Cross-Section (1988-1992)
Groundwater
59,612
231
0.39%
0
0.00%
0
0.00%
Surface Water
8,812
24
0.27%
0
0.00%
0
0.00%
All Samples
68,424
255
0.37%
0
0.00%
0
0.00%
UCM Round 1 - All States (1988-1992)
Groundwater
61,814
241
0.39%
0
0.00%
0
0.00%
Surface Water
9,624
28
0.29%
0
0.00%
0
0.00%
All Samples
71,438
269
0.38%
0
0.00%
0
0.00%
7-31
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Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide
January 2021
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Samples with
Detections
> 1/2 HRL (50 |jg/L)
Samples with
Detections
> HRL (100 |jg/L)
Number
Percent
Number
Percent
Number
Percent
UCM Round 2 - 20-State Cross-Section (1993-1997)
Groundwater
76,588
205
0.27%
0
0.00%
0
0.00%
Surface Water
14,143
30
0.21%
0
0.00%
0
0.00%
All Samples
90,731
235
0.26%
0
0.00%
0
0.00%
UCM Round 2 - All States (1993-1997)
Groundwater
86,765
211
0.24%
0
0.00%
0
0.00%
Surface Water
17,311
32
0.18%
0
0.00%
0
0.00%
All Samples
104,076
243
0.23%
0
0.00%
0
0.00%
Source: USEPA, 2001b
Exhibit 7-21: Methyl Bromide Occurrence Data from UCM Rounds 1 and 2 -
Summary of System and Population Served Data - All Detections
Source Water
Type
Total Number
Detections
Number
Percent
National
Extrapolation1
System
Population
System
Population
System
Population
System
Population
UCM Round 1 - 24-State Cross-Section, 1988-1992
Groundwater
18,472
54,727,934
132
4,467,434
0.71%
8.16%
425
8,040,000
Surface Water
1,886
49,827,646
23
3,574,150
1.22%
7.17%
67
12,100,000
All Systems2
20,198
94,535,081
155
8,041,584
0.77%
8.51%
498
22,700,000
UCM Round 1 - All States (1988-1992)
Groundwater
18,821
56,246,523
140
4,505,072
0.74%
8.01%
442
7,890,000
Surface Water
2,038
51,842,063
27
3,678,650
1.32%
7.10%
73
12,000,000
All Systems2
20,677
97,769,027
166
8,172,222
0.80%
8.36%
521
22,300,000
UCM Round 2 - 20-State Cross-Section, 1993-1997
Groundwater
20,872
25,043,027
154
243,905
0.74%
0.97%
438
959,000
Surface Water
2,456
41,426,449
21
4,890,715
0.86%
11.81%
47
19,900,000
All Systems2
23,328
66,469,476
175
5,134,620
0.75%
7.72%
487
20,700,000
7-32
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Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide
January 2021
Source Water
Type
Total Number
Detections
Number
Percent
National
Extrapolation1
System
Population
System
Population
System
Population
System
Population
UCM Round 2 - All States (1993-1997)
Groundwater
23,888
30,137,407
158
250,357
0.66%
0.83%
393
818,000
Surface Water
2,815
49,422,716
23
4,903,816
0.82%
9.92%
45
16,800,000
All Systems2
26,703
79,560,123
181
5,154,173
0.68%
6.48%
440
17,300,000
Source: USEPA, 2001b
1 National extrapolations are generated by multiplying the UCM findings of system/population percentages and
national system/population inventory numbers for PWSs developed from EPA's Safe Drinking Water Information
System (SDWIS), the Community Water System Survey (CWSS), and UCMR (see Chapter 2 for discussion).
Because some water systems have more than one source water type, extrapolations are generated separately for
"Groundwater", "Surface Water", and "All Systems"; thus, the number of extrapolated groundwater systems plus the
number of extrapolated surface water systems does not add up to the extrapolated "All Systems" numbers.
2 The number of groundwater systems plus the number of surface water systems is not equal to "All Systems"
because some water systems have more than one source water type.
Supplemental Data Sources
State Monitoring Data, 1995-2011
Because there is no available national database that receives and stores all relevant data
regarding the occurrence of regulated contaminants in public drinking water systems, EPA
conducts voluntary data requests from the states, territories, and tribes in support of national
occurrence assessments. These assessments are part of the Six-Year Review. Under the second
and third Six-Year Review (SYR2 and SYR3), a few states submitted PWS occurrence data for
unregulated contaminants along with the requested data on regulated contaminants. EPA was
able to supplement the data on unregulated contaminants by downloading additional publicly
available monitoring data from state websites. For SYR2, the result was a collection of
unregulated contaminant monitoring data from nine states and other entities, such as tribes,
territories, and EPA Regions. For SYR3, the dataset of unregulated contaminant monitoring data
included results from 14 states/entities. For both rounds of the Six-Year Review, these
unregulated data provide varying degrees of completeness in their coverage of the states/entities
and are not necessarily representative of occurrence in those states/entities. For more details on
the Six-Year Review Information Collection Request (ICR) Dataset for SYR2, refer to USEPA
(2009b). For more details on the SYR3 ICR Dataset, refer to EPA's SYR3 occurrence analysis
(USEPA, 2016).
Drinking water occurrence data for methyl bromide were available from California,
Florida, Illinois, North Carolina, Ohio, Region 9 Tribes, South Dakota, and Wisconsin under
SYR2 (1999-2005) and American Samoa, California, Florida, Michigan, Navajo Nation,
Pennsylvania, Region 9 Tribes, Washington, and Wisconsin under SYR3 (2006-2011).2 Results
are presented in Exhibit 7-22 through Exhibit 7-24. The exhibits do not include estimates of
population served because the methyl bromide data submitted under SYR2 and SYR3 represent
only a small portion of all PWSs in each state. See USEPA (2009b) and USEPA (2016) for the
total number of systems that submitted SYR2 and SYR3 data, respectively, from each state.
2 Some states provided more than six years' worth of data to EPA in response to the SYR2 and SYR3 ICRs.
7-33
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Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide
January 2021
Comprehensive information about methods used and reporting levels is not available for this data
set. Minimum detected concentrations are reported in Exhibit 7-22; these minimum values may
be indicative of reporting levels used.
As noted above, the monitoring data from each state/entity are limited and not necessarily
representative of occurrence in the state/entity. The number of PWSs per state with methyl
bromide data ranges from only 6 PWSs in the Illinois SYR2 data to 3,806 PWSs in the California
SYR2 data. Overall, detected concentrations ranged from 0.06 |ig/L to 24 |ig/L. Methyl bromide
was detected at least once in all of the states/entities with the exception of Illinois (SYR2), South
Dakota (SYR2), and American Samoa (SYR3). In the other states/entities, the percentage of
systems with detections ranged from 0.14 percent (Michigan SYR3) to 6.38 percent (Navajo
Nation SYR3). No systems in any state had detections of methyl bromide greater than the HRL
or one-half the HRL.
Exhibit 7-22: Methyl Bromide State Drinking Water Occurrence Data - Summary
of Detected Concentrations
State
(Date Range)
Source Water
Type
(Sample Type)
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Second Six-Year Review (SYR2)
California
(1995-2005)
Groundwater
0.2
1.6
15.6
21
21
Groundwater
(Finished
0.58
2.3
11.3
22.7
24
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
0.5
0.6
3.0
10.3
11.1
Surface Water
(Finished)
0.5
1.0
1.8
2.5
2.6
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Not Provided2
(Raw)
ND
ND
ND
ND
ND
Not Provided3
ND
ND
ND
ND
ND
Total
0.2
1.35
10.0
22.2
24
Florida
(2004-2007)
Groundwater
(Not Provided)1
0.3
0.30
0.30
0.30
0.3
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
0.3
0.30
0.30
0.30
0.3
Illinois
(1998-2005)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
N/A
N/A
N/A
N/A
N/A
Total
ND
ND
ND
ND
ND
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EPA-OGWDW Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide January 2021
State
(Date Range)
Source Water
Type
(Sample Type)
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
99th Percentile
Maximum
North
Carolina
(1999-2005)
Groundwater
(Raw)
ND
ND
ND
ND
ND
Groundwater
(Finished)
0.5
0.80
2.02
19.2
23
Surface Water
(Finished)
ND
ND
ND
ND
ND
Total
0.5
0.80
2.02
19.2
23
Ohio
(1999-2005)
Groundwater
(Not Provided)1
0.5
1.18
5.22
19.4
24
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
0.5
1.18
5.22
19.4
24
Region 9
Tribes
(1999-2005)
Groundwater
(Not Provided)1
0.5
0.50
0.50
0.50
0.5
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
0.5
0.50
0.50
0.50
0.5
South Dakota
(1998-2005)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
Wisconsin
(1983-1999)
Groundwater
(Not Provided)1
0.06
0.42
2.20
3.50
3.5
Surface Water
(Not Provided)1
1.9
1.90
1.90
1.90
1.9
Total
0.06
0.43
2.20
3.50
3.5
Wisconsin
(2000-2005)
Groundwater
(Not Provided)1
0.24
0.71
0.94
0.99
0.99
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
0.24
0.71
0.94
0.99
0.99
Third Six-Year Review (SYR3)
American
Samoa
(2006-2011)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
N/A
N/A
N/A
N/A
N/A
Total
ND
ND
ND
ND
ND
7-35
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Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide
January 2021
State
(Date Range)
Source Water
Type
(Sample Type)
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
99th Percentile
Maximum
California
(2006-2011)
Groundwater
(Raw)
0.39
0.8
5.0
9.3
9.3
Groundwater
(Finished)
1.6
1.7
1.9
2.0
2
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Raw)
4.89
4.89
4.89
4.89
4.89
Surface Water
(Finished)
0.9
0.9
0.9
0.9
0.9
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
0.39
0.89
4.95
9.3
9.3
Florida
(2006-2011)
Groundwater
(Raw)
0.3
0.3
0.3
0.3
0.3
Groundwater
(Not Provided)1
8.2
8.2
8.2
8.2
8.2
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
0.3
4.25
7.41
8.12
8.2
Michigan
(2006-2011)
Groundwater
(Not Provided)1
1
1.35
1.63
1.69
1.7
Surface Water
(Not Provided)1
0.6
0.65
0.69
0.70
0.7
Not Provided3
ND
ND
ND
ND
ND
Total
0.6
0.85
1.49
1.68
1.7
Navajo Nation
(2007-2010)
Groundwater
(Not Provided)1
1.2
2.60
5.38
6.00
6.07
Surface Water
(Not Provided)1
N/A
N/A
N/A
N/A
N/A
Total
1.2
2.60
5.38
6.00
6.07
Pennsylvania
(2006-2011)
Groundwater
ND
ND
ND
ND
ND
Groundwater
(Not Provided)1
0.6
0.95
1.23
1.29
1.3
Surface Water
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
0.6
0.95
1.23
1.29
1.3
7-36
-------
EPA - OGWDW
Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide
January 2021
State
(Date Range)
Source Water
Type
(Sample Type)
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Region 9
Tribes
(2006-2011)
Groundwater
(Not Provided)1
0.16
0.84
1.29
1.39
1.4
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
0.16
0.84
1.29
1.39
1.4
Washington
(2006-2011)
Groundwater
(Raw)
4
4
4
4
4
Groundwater
(Finished)
0.5
1.2
2.7
4.4
4.7
Groundwater
(Not Provided)1
0.75
2.7
4.7
5.6
5.7
Surface Water
(Raw)
0.56
1.1
1.2
1.2
1.2
Surface Water
(Finished)
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Not Provided2
(Raw)
ND
ND
ND
ND
ND
Not Provided2
(Finished)
ND
ND
ND
ND
ND
Not Provided3
ND
ND
ND
ND
ND
Total
0.5
1.20
3.99
5.40
5.7
Wisconsin
(2006-2011)
Groundwater
(Not Provided)1
0.19
1.40
1.81
1.89
1.9
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Not Provided3
ND
ND
ND
ND
ND
Total
0.19
1.40
1.81
1.89
1.9
Source: Data provided to EPA by states and downloaded by EPA from state websites
ND = no detections in this category
N/A = no data in this category
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from groundwater or surface water.
3 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
7-37
-------
EPA - OGWDW
Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide
January 2021
Exhibit 7-23: Methyl Bromide State Drinking Water Occurrence Data - Summary
of Samples
State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Samples
All Detections
Samples with
Detections > Vi HRL
(50 jig/L)
Samples with
Detections > HRL
(100 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Second Six-Year Review (SYR2)
California
(1995-2005)
Groundwater
(Raw)
47,272
29
0.06%
0
0.00%
0
0.00%
Groundwater
(Finished)
5,532
10
0.18%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
93
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
33,612
11
0.03%
0
0.00%
0
0.00%
Surface Water
(Finished)
12,733
10
0.08%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
264
0
0.00%
0
0.00%
0
0.00%
Not Provided2
(Raw)
32
0
0.00%
0
0.00%
0
0.00%
Not Provided3
2
0
0.00%
0
0.00%
0
0.00%
Total
99,540
60
0.06%
0
0.00%
0
0.00%
Florida
(2004-2007)
Groundwater
(Not Provided)1
1,756
1
0.06%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
11
0
0.00%
0
0.00%
0
0.00%
Total
1,767
1
0.06%
0
0.00%
0
0.00%
Illinois
(1998-2005)
Groundwater
(Not Provided)1
6
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Total
6
0
0.00%
0
0.00%
0
0.00%
North
Carolina
(1999-2005)
Groundwater
(Raw)
163
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Finished)
17,580
23
0.13%
0
0.00%
0
0.00%
Surface Water
(Finished
2,112
0
0.00%
0
0.00%
0
0.00%
Total
19,855
23
0.12%
0
0.00%
0
0.00%
Ohio
(1999-2005)
Groundwater
(Not Provided)1
8,276
52
0.63%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
993
0
0.00%
0
0.00%
0
0.00%
Total
9,269
52
0.56%
0
0.00%
0
0.00%
Region 9
Tribes
(1999-2005)
Groundwater
(Not Provided)1
1,076
1
0.09%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
87
0
0.00%
0
0.00%
0
0.00%
Total
1,163
1
0.09%
0
0.00%
0
0.00%
7-38
-------
EPA-OGWDW Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide January 2021
State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Samples
All Detections
Samples with
Detections > Vi HRL
(50 jig/L)
Samples with
Detections > HRL
(100 |jg/L)
Number
Percent
Number
Percent
Number
Percent
South Dakota
(1998-2005)
Groundwater
(Not Provided)1
1,057
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
53
0
0.00%
0
0.00%
0
0.00%
Total
1,110
0
0.00%
0
0.00%
0
0.00%
Wisconsin
(1983-1999)
Groundwater
(Not Provided)1
14,583
31
0.21%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
435
1
0.23%
0
0.00%
0
0.00%
Total
15,018
32
0.21%
0
0.00%
0
0.00%
Wisconsin
(2000-2005)
Groundwater
(Not Provided)1
4,130
4
0.10%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
82
0
0.00%
0
0.00%
0
0.00%
Total
4,212
4
0.09%
0
0.00%
0
0.00%
Third Six-Year Review (SYR3)
American
Samoa
(2006-2011)
Groundwater
(Not Provided)1
66
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Total
66
0
0.00%
0
0.00%
0
0.00%
California
(2006-2011)
Groundwater
(Raw)
24,104
33
0.14%
0
0.00%
0
0.00%
Groundwater
(Finished)
18,319
3
0.02%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
122
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
12,320
1
0.01%
0
0.00%
0
0.00%
Surface Water
(Finished)
4,649
1
0.02%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
55
0
0.00%
0
0.00%
0
0.00%
Total
59,569
38
0.06%
0
0.00%
0
0.00%
Florida
(2006-2011)
Groundwater
(Raw)
219
1
0.46%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
1,653
1
0.06%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
18
0
0.00%
0
0.00%
0
0.00%
Total
1,890
2
0.11%
0
0.00%
0
0.00%
Michigan
(2006-2011)
Groundwater
(Not Provided)1
8,166
2
0.02%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
665
2
0.30%
0
0.00%
0
0.00%
Not Provided3
39
0
0.00%
0
0.00%
0
0.00%
Total
8,870
4
0.05%
0
0.00%
0
0.00%
7-39
-------
EPA - OGWDW
Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide
January 2021
State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
All Detections
Samples with
Detections > Vi HRL
(50 jig/L)
Samples with
Detections > HRL
(100 |jg/L)
Samples
Number
Percent
Number
Percent
Number
Percent
Navajo Nation
(2007-2010)
Groundwater
(Not Provided)1
65
3
4.62%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Total
65
3
4.62%
0
0.00%
0
0.00%
Groundwater
(Raw)
44
0
0.00%
0
0.00%
0
0.00%
Pennsylvania
(2006-2011)
Groundwater
(Not Provided)1
1,327
2
0.15%
0
0.00%
0
0.00%
Surface Water
(Raw)
47
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
204
0
0.00%
0
0.00%
0
0.00%
Total
1,622
2
0.12%
0
0.00%
0
0.00%
Region 9
Tribes
(2006-2011)
Groundwater
(Not Provided)1
353
3
0.85%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
27
0
0.00%
0
0.00%
0
0.00%
Total
380
3
0.79%
0
0.00%
0
0.00%
Groundwater
(Raw)
4,110
1
0.02%
0
0.00%
0
0.00%
Groundwater
(Finished)
2,954
20
0.68%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
1,017
7
0.69%
0
0.00%
0
0.00%
Surface Water
(Raw)
255
3
1.18%
0
0.00%
0
0.00%
Washington
(2006-2011)
Surface Water
(Finished)
541
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
67
0
0.00%
0
0.00%
0
0.00%
Not Provided2
(Raw)
90
0
0.00%
0
0.00%
0
0.00%
Not Provided2
(Finished)
2
0
0.00%
0
0.00%
0
0.00%
Not Provided3
35
0
0.00%
0
0.00%
0
0.00%
Total
9,071
31
0.34%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
4,273
4
0.09%
0
0.00%
0
0.00%
Wisconsin
(2006-2011)
Surface Water
(Not Provided)1
224
0
0.00%
0
0.00%
0
0.00%
Not Provided3
7
0
0.00%
0
0.00%
0
0.00%
Total
4,504
4
0.09%
0
0.00%
0
0.00%
Source: Data provided to EPA by states and downloaded by EPA from state websites
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from groundwater or surface water.
3 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
7-40
-------
EPA - OGWDW
Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide
January 2021
Exhibit 7-24: Methyl Bromide State Drinking Water Occurrence Data - Summary
of Systems
State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > Vi HRL
(50 |ig/L)
Systems with
Detections > HRL
(100 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Second Six-Year Review (SYR2)
California
(1995-2005)
Groundwater
(Raw)
3,225
23
0.71%
0
0.00%
0
0.00%
Groundwater
(Finished
147
6
4.08%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
39
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
506
10
1.98%
0
0.00%
0
0.00%
Surface Water
(Finished
213
6
2.82%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
14
0
0.00%
0
0.00%
0
0.00%
Not Provided2
(Raw)
20
0
0.00%
0
0.00%
0
0.00%
Not Provided3
1
0
0.00%
0
0.00%
0
0.00%
Total
3,806
41
1.08%
0
0.00%
0
0.00%
Florida
(2004-2007)
Groundwater
(Not Provided)1
26
1
3.85%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
1
0
0.00%
0
0.00%
0
0.00%
Total
27
1
3.70%
0
0.00%
0
0.00%
Illinois
(1998-2005)
Groundwater
(Not Provided)1
6
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Total
6
0
0.00%
0
0.00%
0
0.00%
North
Carolina
(1999-2005)
Groundwater
(Raw)
115
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Finished)
2,285
22
0.96%
0
0.00%
0
0.00%
Surface Water
(Finished)
202
0
0.00%
0
0.00%
0
0.00%
Total
2,493
22
0.88%
0
0.00%
0
0.00%
Ohio
(1999-2005)
Groundwater
(Not Provided)1
2,378
41
1.72%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
153
0
0.00%
0
0.00%
0
0.00%
Total
2,531
41
1.62%
0
0.00%
0
0.00%
Region 9
Tribes
(1999-2005)
Groundwater
(Not Provided)1
270
1
0.37%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
16
0
0.00%
0
0.00%
0
0.00%
Total
286
1
0.35%
0
0.00%
0
0.00%
7-41
-------
EPA-OGWDW Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide January 2021
State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > Vi HRL
(50 |ig/L)
Systems with
Detections > HRL
(100 |jg/L)
Number
Percent
Number
Percent
Number
Percent
South Dakota
(1998-2005)
Groundwater
(Not Provided)1
258
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
23
0
0.00%
0
0.00%
0
0.00%
Total
281
0
0.00%
0
0.00%
0
0.00%
Wisconsin
(1983-1999)
Groundwater
(Not Provided)1
1,897
28
1.48%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
32
1
3.13%
0
0.00%
0
0.00%
Total
1,929
29
1.50%
0
0.00%
0
0.00%
Wisconsin
(2000-2005)
Groundwater
(Not Provided)1
936
4
0.43%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
22
0
0.00%
0
0.00%
0
0.00%
Total
958
4
0.42%
0
0.00%
0
0.00%
Third Six-Year Review (SYR3)
American
Samoa
(2006-2011)
Groundwater
(Not Provided)1
11
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Total
11
0
0.00%
0
0.00%
0
0.00%
California
(2006-2011)
Groundwater
(Raw)
3,039
29
0.95%
0
0.00%
0
0.00%
Groundwater
(Finished)
129
3
2.33%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
53
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
433
1
0.23%
0
0.00%
0
0.00%
Surface Water
(Finished)
127
1
0.79%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
19
0
0.00%
0
0.00%
0
0.00%
Total
3,520
34
0.97%
0
0.00%
0
0.00%
Florida
(2006-2011)
Groundwater
(Raw)
3
1
33.33%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
40
1
2.50%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
1
0
0.00%
0
0.00%
0
0.00%
Total
42
2
4.76%
0
0.00%
0
0.00%
Michigan
(2006-2011)
Groundwater
(Not Provided)1
2,677
2
0.07%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
91
2
2.20%
0
0.00%
0
0.00%
Not Provided3
33
0
0.00%
0
0.00%
0
0.00%
Total
2,801
4
0.14%
0
0.00%
0
0.00%
7-42
-------
EPA - OGWDW
Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide
January 2021
State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > Vi HRL
(50 |ig/L)
Systems with
Detections > HRL
(100 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Navajo
Nation
(2007-2010)
Groundwater
(Not Provided)1
47
3
6.38%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Total
47
3
6.38%
0
0.00%
0
0.00%
Pennsylvania
(2006-2011)
Groundwater
(Raw)
10
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
207
2
0.97%
0
0.00%
0
0.00%
Surface Water
(Raw)
3
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
26
0
0.00%
0
0.00%
0
0.00%
Total
233
2
0.86%
0
0.00%
0
0.00%
Region 9
Tribes
(2006-2011)
Groundwater
(Not Provided)1
177
3
1.69%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
14
0
0.00%
0
0.00%
0
0.00%
Total
191
3
1.57%
0
0.00%
0
0.00%
Washington
(2006-2011)
Groundwater
(Raw)
1,603
1
0.60%
0
0.00%
0
0.00%
Groundwater
(Finished)
1,071
8
0.75%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
579
6
1.04%
0
0.00%
0
0.00%
Surface Water
(Raw)
88
1
1.14%
0
0.00%
0
0.00%
Surface Water
(Finished)
132
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
33
0
0.00%
0
0.00%
0
0.00%
Not Provided2
(Raw)
64
0
0.00%
0
0.00%
0
0.00%
Not Provided2
(Finished)
2
0
0.00%
0
0.00%
0
0.00%
Not Provided3
22
0
0.00%
0
0.00%
0
0.00%
Total
2,768
15
0.54%
0
0.00%
0
0.00%
Wisconsin
(2006-2011)
Groundwater
(Not Provided)1
778
2
0.26%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
29
0
0.00%
0
0.00%
0
0.00%
Not Provided3
6
0
0.00%
0
0.00%
0
0.00%
Total
813
2
0.25%
0
0.00%
0
0.00%
Source: Data provided to EPA by states and downloaded by EPA from state websites
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from groundwater or surface water.
3 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
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United States Geological Survey (USGS) National Water Quality Assessment (NAWQA)
Source Water and Drinking Water Studies
Note that there may be some overlap between the NAWQA data assessment presented
earlier in the ambient water occurrence section and the summaries of NAWQA studies presented
below. The studies presented below include occurrence data from water sources for PWSs.
Organic Compounds in Source Water of Selected Community Water Systems (Hopple
et al., 2009 and Kingsbury et al., 2008), 2002-2005
As part of the NAWQA program, Hopple et al. (2009) and Kingsbury et al. (2008)
conducted studies to characterize anthropogenic organic compounds in waters of the United
States used as source waters for PWSs. Hopple et al. (2009) focused on groundwater and
Kingsbury et al. (2008) focused on surface water. In Phase 1 of the studies, geographically
diverse source water samples were collected between October 2002 and July 2005 from nine
CWSs served by streams and from 221 CWSs that withdraw from 12 aquifers. In Phase 2 of the
studies, USGS collected source and finished water samples at a subset of sites between June
2004 and September 2005. Methyl bromide was not included in the Phase 2 analysis of surface
water. The reporting level for methyl bromide was 0.33 [j,g/L for groundwater and surface water
samples in Phase 1 of the studies but was not specified for Phase 2 of the studies.
Methyl bromide was not detected in any of the 221 groundwater samples or 147 surface
water samples collected during Phase 1 of the studies. Methyl bromide was not detected in any
of the 71 raw or 71 finished water samples collected in Phase 2 of the groundwater study. No
surface water samples were analyzed for methyl bromide in Phase 2.
Volatile Organic Compounds in Drinking Water of Selected Community Water
Systems (Grady and Casey, 2001), 1993-1998
USGS compiled and analyzed occurrence data for VOCs in finished drinking water in 12
Northeast and Mid-Atlantic states (Connecticut, Delaware, Maine, Maryland, Massachusetts,
New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Virginia).
State agencies supplied USGS with VOC data collected during 1993 through 1998 for 20 percent
of the CWSs in the 12-state area, which were chosen to be representative in terms of geography,
water source, and system size. The methyl bromide analysis included 1,667 CWSs in all 12
states. Methyl bromide was detected in 10 of 12,733 samples (0.08 percent). Detected
concentrations ranged from 0.39 to 5.0 |ig/L (Grady and Casey, 2001). No detected
concentrations were greater than one-half the HRL or the HRL.
Water Quality in Public-Supply Wells (Toccalino et al., 2010), 1993-2007
To assess risks posed by contaminants in public-supply wells, water samples were
collected from source (untreated) groundwater from 932 public-supply wells located in parts of
40 NAWQA Study Units in 41 states (Toccalino et al., 2010). Each well was sampled once
between 1993 and 2007. The public wells sampled in this study represented 629 unique PWSs,
representing 0.5 percent of the approximately 140,000 groundwater-supplied PWSs, but nearly
25 percent of the population served by groundwater-PWSs in the United States. Methyl bromide
was not detected in any of the 832 samples.
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Water Quality in Domestic Wells (DeSimone, 2009), 1991-2004
Between 1991 and 2004, USGS assessed water quality from domestic wells across the
United States using NAWQA data (DeSimone, 2009). The program included the analysis of
major ions, trace elements, nutrients, radon, and organic compounds (pesticides and VOCs) at
approximately 2,100 domestic wells (private drinking water wells) across 48 states, covering 30
regional aquifers. In addition, USGS summarized data from wells sampled for NAWQA
agricultural land-use assessment studies to provide an indication of the potential effects of
agricultural land-use practices on the groundwater in the aquifers studied. Reporting thresholds
varied; the most common thresholds were between 0.074 [j,g/L and 0.2 (J,g/L. Methyl bromide
was not detected in the study.
Volatile Organic Compounds (VOCs) in Domestic Wells (Moran et al., 2002; Rowe et
al., 2007), 1986-1999 and 1996-2002
As part of the NAWQA program, USGS studied the occurrence of VOCs in groundwater
from untreated rural self-supplied domestic wells between 1986 and 1999 (Moran et al., 2002).
Drinking water at such domestic wells are not subject to EPA drinking water regulations.
Reporting levels varied; results for most VOCs were reported at an assessment level of 0.2 |ig/L
to allow for comparison of detection frequencies between different groups of analytes. A total of
1,677 samples were analyzed for methyl bromide; it was not detected in any sample at any
assessment level.
USGS also published the findings of a national assessment of VOCs in domestic wells
between 1996 and 2002 (Rowe et al., 2007). In this study, samples were analyzed for 55 VOCs.
Methyl bromide, analyzed at reporting levels ranging from 0.148 |ig/L to 0.4 |ig/L, was not
detected in any of the 1,208 domestic well samples.
Water Quality in Carbonate Aquifers (Lindsey et al., 2008), 1993-2005
As part of the NAWQA program, Lindsey et al. (2008) assessed the water quality in
carbonate aquifers, which account for 22 percent of the groundwater pumped by the country's
PWSs. From 1993 to 2005, the study analyzed 1,042 wells and springs across 12 aquifer systems
and 20 states for major ions, radon, nutrients, pesticides, and VOCs. The study authors evaluated
occurrence of most VOCs at a uniform assessment level of 0.2 (J,g/L. Methyl bromide was not
detected in any of the 793 samples analyzed for the contaminant.
Volatile Organic Compounds in the Nation's Groundwater andDrinking-Water Supply
Wells (Zogorski et al., 2006), 1985-2002
Zogorski et al. (2006) discuss the major findings and conclusions of the national
assessment of 55 VOCs in groundwater. VOC data from 2,401 domestic wells and 1,096 public
wells were available from aquifer studies, shallow groundwater studies, and a national source-
water survey to characterize the occurrence of VOCs. One VOC analysis per well was included
in the assessment.
In samples from aquifer studies, methyl bromide was detected at levels > 0.2 [j,g/L in 1
(0.03 percent) of 3,119 samples at a concentration of 0.5 (J,g/L. In samples from domestic wells,
methyl bromide was not detected at levels > 0.2 [j,g/L in 2,156 samples. In samples from public
wells, methyl bromide was detected at levels > 0.2 [j,g/L in 1 (0.09 percent) of 1,078 samples at a
concentration of 6.4 |ig/L which is less than one-half the HRL and the HRL.
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7.5 Analytical Methods
EPA has published four analytical methods that are available for the analysis of methyl
bromide in drinking water:
• EPA Method 502.2, Revision 2.1, Volatile Organic Compounds in Water by Purge
and Trap Capillary Column Gas Chromatography with Photoionization and
Electrolytic Conductivity Detectors in Series. Mean recovery in reagent water is 97%,
with Relative Standard Deviations (RSDs) of 2.4 to 3.8 percent (USEPA, 1995a).
• EPA Method 524.2, Revision 4.1, Measurement of Purgeable Organic Compounds in
Water by Capillary Column Gas Chromatography/Mass Spectrometry. Mean
recoveries in reagent water range from 52 to 99 percent, with RSDs of 6.7 to 27
percent (USEPA, 1995b).
• EPA Method 524.3, Version 1.0, Measurement of Purgeable Organic Compounds in
Water by Capillary Column Gas Chromatography/Mass Spectrometry. The Lowest
Concentration Minimum Reporting Level (LCMRL) generated by the laboratory that
developed the method is 0.072 |ig/L using Full Scan mode. Mean recoveries in
fortified reagent water and drinking water (from groundwater and surface water
sources) range from 97.9 to 112%, with RSDs of 2.1 to 10 percent using Full Scan
mode (USEPA, 2008c).
• EPA Method 524.4, Measurement of Purgeable Organic Compounds in Water by
Gas Chromatography/Mass Spectrometry Using Nitrogen Purge Gas. The LCMRL
generated by the laboratory that developed the method is 0.28 |ig/L using Full Scan
mode. The LCMRL could not be determined using Selected Ion Monitoring (SIM)
mode due to background interference. Mean recoveries in fortified reagent water,
groundwater, and surface water range from 104 to 127 percent with RSDs of 5.3 to 10
percent using Full Scan mode (USEPA, 2013).
Laboratories participating in UCMR 3 were required to use EPA Method 524.3 in SIM
Mode and, as noted in Section 7.4.2, were required to report methyl bromide values at or above
the EPA-defined MRL of 0.2 |ig/L (77 FR 26072; USEPA, 2012). The MRL was set based on
the capability of multiple laboratories at the time.
7.6 Treatment Technologies
EPA evaluates whether suitable treatment technologies are available prior to
promulgating a final National Primary Drinking Water Regulation (NPDWR).
A preliminary review of the literature conducted in 2009 suggests that superoxide ion
degradation and steam air stripping might be effective technologies for removal of this
contaminant. Other treatment technologies that have been investigated empirically for their
applicability to this contaminant include zeolite adsorption from air and cryogenic condensation
and biological filtration (using granular activated carbon and microbes). The exact percentage
removal a water system may achieve with a given technology will be dependent upon a variety
of factors, including source water quality and water system characteristics.
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7.7 References
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Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide
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Gansewendt, B., U. Foest, D. Xu et al. 1991. Formation of DNA adducts in F-344 rats after oral
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Kingsbury, J.A., G.C. Delzer, and J.A. Hopple. 2008. Anthropogenic Organic Compounds in
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NRC. 2012. Preparing for the Third Decade of the National Water-Quality Assessment
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assessment verification date May 26, 1988. U.S. Environmental Protection Agency,
Office of Research and Development, Washington, DC. Available on the Internet at:
https://cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm7substance nmbr=15. Accessed
December 2018.
USEPA. 1989a. Bromomethane: Drinking Water Health Advisory. U.S. Environmental
Protection Agency, Office of Water.
USEPA. 1989b. Bromomethane (CASRN 74-83-9). Integrated Risk Information System.
Carcinogenicity assessment verification date March 1, 1989. U.S. Environmental
Protection Agency, Office of Research and Development, Washington, DC. Available on
the Internet at:
https://cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm7substance nmbr=15. Accessed
March 2015.
USEPA. 1995a. Method 502.2. Volatile Organic Compounds in Water by Purge and Trap
Capillary Column Gas Chromatography with Photoionization and Electrolytic
Conductivity Detectors in Series. Revision 2.1. National Exposure Research Laboratory,
Office of Research and Development. EPA 600-R-95-131.
USEPA. 1995b. Method 524.2. Measurement of Purgeable Organic Compounds in Water by
Capillary Column Gas Chromatography/Mass Spectrometry. Revision 4.1. National
Exposure Research Laboratory, Office of Research and Development. EPA 600-R-95-
131.
USEPA. 2001a. Occurrence of Unregulated Contaminants in Public Water Systems: An Initial
Assessment. Office of Water. EPA 815-P-00-001.
USEPA. 2001b. UCM - State Rounds 1 and 2 (1988 - 1997) Occurrence Data. Available on the
Internet at: https://www.epa.gov/dwucmr/occurrence-data-unregulated-contaminant-
monitoring-rule# 12
USEPA. 2003. Occurrence Estimation Methodology and Occurrence Findings for Six-Year
Review of National Primary Drinking Water Regulations. Office of Water. EPA 815-R-
03-006.
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EPA-OGWDW Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide January 2021
USEPA. 2004. Pesticide Industry Sales and Usage: 2000 and 2001 Market Estimates. Biological
and Economic Analysis Division, Office of Pesticide Programs. May 2004.
USEPA. 2006a. Report of Food Quality Protection Act (FQPA) Tolerance Reassessment and
Risk Management Decision (TRED) for Methyl Bromide, and Reregistration Eligibility
Decision (RED) for Methyl Bromide's Commodity Uses. EPA 738-R-06-026. Office of
Prevention, Pesticides and Toxic Substances. Available on the Internet at:
https://archive.epa.gov/pesticides/reregistration/web/pdf/methyl bromide tred.pdf.
USEPA. 2006b. Methyl Bromide: Phase 5 Health Effects Division (HED) Human Health Risk
Assessment for Commodity Uses. PC Code 053201, DP Barcode D304623. U.S.
Environmental Protection Agency, Office of Prevention, Pesticides and Toxic
Substances, Washington, DC. Accessed February 2015.
USEPA. 2007. Provisional Peer Reviewed Toxicity Values for Bromomethane (CASRN 74-83-
9). Superfund Health Risk Technical Support Center, National Center for Environmental
Assessment, Office of Research and Development, U.S. Environmental Protection
Agency, Cincinnati, OH. https://hhpprtv.ornl.gov/issue papers/Bromomethane.pdf
USEPA. 2008a. Using the 2006 Inventory Update Reporting (IUR) Public Data: Background
Document. Office of Pollution Prevention and Toxics. December. Available on the
Internet at:
https://www.epa.gov/sites/production/files/documents/iurdbbackground O.pdf.
USEPA. 2008b. The Analysis of Occurrence Data from the Unregulated Contaminant
Monitoring (UCM) Program and National Inorganics and Radionuclides Survey (NIRS)
in Support of Regulatory Determinations for the Second Drinking Water Contaminant
Candidate List. Office of Water. EPA 815-R-08-014.
USEPA. 2008c. Method 524.3. Measurement of Purgeable Organic Compounds in Water by
Capillary Column Gas Chromatography/Mass Spectrometry. Version 1.0. Technical
Support Center, Office of Ground Water and Drinking Water. EPA 815-B-09-009.
USEPA. 2009a. Amended Reregistration Eligibility Decision for Methyl Bromide (soil and non-
food structural uses). Office of Prevention, Pesticides and Toxic Substances. EPA 738-R-
09-311. https://archive.epa.gov/pesticides/reregistration/web/pdf/methylbromide-red-
amended.pdf.
USEPA. 2009b. The Analysis of Regulated Contaminant Occurrence Data from Public Water
Systems in Support of the Second Six-Year Review of National Primary Drinking Water
Regulations. EPA 815-B-09-006. October 2009.
USEPA. 201 la. Cancellation Order for Registration Amendments to Terminate Certain Soil
Uses: Methyl Bromide. Federal Register 76(98): 29238, May 20, 2011.
USEPA. 201 lb. Pesticide Industry Sales and Usage: 2006 and 2007Market Estimates.
Biological and Economic Analysis Division, Office of Pesticide Programs. Available on
the Internet at: https://www.epa.gov/pesticides/pesticides-industry-sales-and-usage-2006-
and-2007-market-estimates.
USEPA. 2012. Revisions to the Unregulated Contaminant Monitoring Regulation (UCMR 3) for
Public Water Systems. Federal Register 7(85): 26072, May 2, 2012.
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EPA-OGWDW Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide January 2021
USEPA. 2013. Method 524.4. Measurement of Purgeable Organic Compounds in Water by Gas
Chromatography/Mass Spectrometry Using Nitrogen Purge Gas. Technical Support
Center, Office of Ground Water and Drinking Water. EPA 815-R-13-002.
USEPA. 2014a. The Phaseout of Methyl Bromide. U.S. Environmental Protection Agency,
Office of Atmospheric Programs, Washington, DC. Accessed December 2018. Available
on the Internet at: https://www.epa.gov/ods-phaseout/methyl-bromide.
USEPA. 2014b. Chemical Data Reporting. Fact Sheet: Basic Information. June 2014. EPA
Publication 740-K-13-001.
USEPA. 2016. The Analysis of Regulated Contaminant Occurrence Data from Public Water
Systems in Support of the Third Six-Year Review of National Primary Drinking Water
Regulations: Chemical Phase Rules and Radionuclides Rules. EPA 810-R-16-014.
December 2016.
USEPA. 2017a. Pesticide Industry Sales and Usage: 2008 to 2012 Market Estimates. Biological
and Economic Analysis Division, Office of Pesticide Programs. Available on the Internet
at: https://www.epa.gov/pesticides/pesticides-industrv-sales-and-usage-2008-2Q12-
market-estimates.
USEPA. 2017b. TRI Explorer: Trends. Available on the Internet at:
https://enviro.epa.gov/triexplorer/tri release.trends. Accessed November 2017.
USEPA. 2017c. Third Unregulated Contaminant Monitoring Rule Dataset. Available on the
Internet at: https://www.epa.gov/dwucmr/occurrence-data-unregulated-contaminant-
monitoring-rule#3. Accessed January 2017.
USEPA. 2018a. Pesticide Chemical Search. U.S. Environmental Protection Agency, Office of
Pesticide Programs, Washington, DC. Accessed December 2018.
http://iaspub.epa.gov/apex/pesticides/f?p=chemicalsearch: 1.
USEPA. 2018b. CDR Reporting Requirements, https://www.epa.gov/chemical-data-
reporting/how-report-under-chemical-data-reporting. Accessed December 2018.
USEPA. 2018c. Methyl Bromide. Draft Human Health Risk Assessment for Registration Review.
PC Code 05320. DP Barcode D449330. U.S. Environmental Protection Agency, Office of
Prevention, Pesticides and Toxic Substances, Washington DC.
USEPA. 2019a. CompTox Chemicals Dashboard, Searched by DSSTox Substance Id =
DTXSID8020832. Available on the Internet at:
https://comptox.epa. gov/dashboard/dsstoxdb/results?search=DTXSID8020832.
USEPA. 2019b. The Toxics Release Inventory (TRI) and Factors to Consider When Using TRI
Data. Available on the Internet at: https://www.epa.gov/toxics-release-inventory-tri-
program/factors-consider-when-using-toxics-release-inventory-data.
USEPA. 2019c. Occurrence Data from the Third Unregulated Contaminant Monitoring Rule
(UCMR 3). EPA 815-R-19-007.
United States Geological Survey (USGS). 2016. National Water Information System (NWIS)
Water-Quality Web Services. Available on the Internet at:
https://waterdata.usgs.gov/nwis. Last modified December 2016.
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EPA-OGWDW Final Regulatory Determination 4 Support Document - Ch 7, Methyl Bromide January 2021
USGS. 2018. Pesticide National Synthesis Project, 2016 Pesticide Use Maps. Available on the
Internet at:
http://water.usgs.gov/nawqa/pnsp/usage/maps/compound listing.php?year=02. Accessed
December 2018.
Vogel, E.W. and M.J.M. Nivard. 1994. The subtlety of alkylating agents in reactions with
biological macromolecules. Mutat. Res. 305: 13-32 (as cited in USESPA, 2007).
von Guerard, P. and W.B. Weiss. 1995 Water Quality of Storm Runoff and Comparison of
Procedures for Estimating Storm-Runoff Loads, Volume, Event-Mean Concentrations,
and the Mean Loadfor a Storm for Selected Properties and Constituents for Colorado
Springs, Southeastern Colorado, 1992. U.S. Geological Survey Water-Resources
Investigations Report 94-4194, 68 pp. Available on the Internet at:
http://pubs.usgs. gov/wri/1994/4194/report.pdf.
Water Quality Portal (WQP). 2017. Water Quality Portal Data Warehouse. Available on the
Internet at: https://www.waterqualitvdata.us/. Data Warehouse consulted December 2017.
Wester, P.W. and R. Kroes, 1988. Forestomach carcinogens: pathology and relevance to man.
Toxicologic Pathology 16(2): 165-71.
WQP. 2018. Water Quality Portal Data Warehouse. Available on the Internet at:
https://www.waterqualitvdata.us/. Data Warehouse consulted September 2018.
Zogorski, J.S., J.M. Carter, T. Ivahnenko, W.W. Lapham, M.J. Moran, B.L. Rowe, P.J.
Squillace, and P.L. Toccalino. 2006. Volatile Organic Compounds in the Nation's
Ground Water andDrinking-Water Supply Wells. USGS Circular 1292. Available on the
Internet at: http://pubs.usgs.gov/circ/circl292/pdf/circularl292.pdf.
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Final Regulatory Determination 4 Support Document - Ch 8, Metolachlor
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Chapter 8:
Metolachlor
A chapter from:
Final Regulatory Determination 4 Support Document
EPA Report 815-R-21-001
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Contents
Contents 8-2
Exhibits 8-3
Abbreviations 8-4
Chapter 8: Metolachlor 8-6
8.1 Contaminant Background and Chemical and Physical Properties 8-6
8.2 Sources and Environmental Fate 8-8
8.2.1 Production, Use, and Release 8-8
8.2.2 Environmental Fate 8-10
8.3 Health Effects 8-12
8.3.1 Toxicokinetics 8-12
8.3.2 Available Health Effects Assessments 8-12
8.3.3 Health Effects 8-13
8.3.4 Basis of the HRL 8-15
8.3.5 Health Effects Data Gaps 8-16
8.4 Occurrence 8-16
8.4.1 Occurrence in Ambient Water 8-16
8.4.2 Occurrence in Drinking Water 8-25
8.4.3 Other Data 8-52
8.5 Analytical Methods 8-52
8.6 Treatment Technologies 8-53
8.7 References 8-54
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Exhibits
Exhibit 8-1: Chemical Structure of Metolachlor 8-7
Exhibit 8-2: Physical and Chemical Properties of Metolachlor 8-7
Exhibit 8-3: Estimated Annual Agricultural Use of Metolachlor, 2016 8-9
Exhibit 8-4: Estimated Annual Agricultural Use of S-Metolachlor, 2016 8-10
Exhibit 8-5: Available Health Effects Assessments for Metolachlor 8-12
Exhibit 8-6: Metolachlor NAWQA Data - Summary of Detected Concentrations 8-18
Exhibit 8-7: Metolachlor NAWQA Data - Summary of Samples 8-19
Exhibit 8-8: Metolachlor NAWQA Data - Summary of Sites 8-19
Exhibit 8-9: USGS National Synthesis Summary of NAWQA Monitoring of Metolachlor in
Streams, 1992-2001 8-21
Exhibit 8-10: USGS National Synthesis Summary of NAWQA Monitoring of Metolachlor in
Groundwater, 1992-2001 8-21
Exhibit 8-11: Metolachlor NWIS Data, 1991 -2016 8-22
Exhibit 8-12: Metolachlor STORET Data - Summary of Detected Concentrations 8-23
Exhibit 8-13: Metolachlor STORET Data - Summary of Samples and Sites 8-23
Exhibit 8-14: Metolachlor STORET Data - Summary of States 8-23
Exhibit 8-15: Metolachlor Occurrence Data from UCMR 2 Screening Survey - Summary of
Detected Concentrations 8-26
Exhibit 8-16: Metolachlor National Occurrence Measures Based on UCMR 2 Screening
Survey Data - Summary of Samples 8-27
Exhibit 8-17: Metolachlor National Occurrence Measures Based on UCMR 2 Screening
Survey Data - Summary of System and Population Served Data - All Detections 8-28
Exhibit 8-18: Metolachlor Occurrence Data from UCM Round 2 - Summary of Detected
Concentrations 8-30
Exhibit 8-19: Metolachlor Occurrence Data from UCM Round 2 - Summary of Samples 8-30
Exhibit 8-20: Metolachlor Occurrence Data from UCM Round 2 - Summary of System and
Population Served Data - All Detections 8-31
Exhibit 8-21: Metolachlor State Drinking Water Occurrence Data - Summary of Detected
Concentrations 8-32
Exhibit 8-22: Metolachlor State Drinking Water Occurrence Data - Summary of Samples.... 8-36
Exhibit 8-23: Metolachlor State Drinking Water Occurrence Data - Summary of Systems .... 8-39
Exhibit 8-24: Summary of Metolachlor PDP Data, 2001-2013 8-45
Exhibit 8-25: Drinking Water Treatment Plants - Summary of Metolachlor Samples
(Glassmeyer et al., 2017) 8-46
Exhibit 8-26: Metolachlor Data from Source Water (Hopple et al., 2009 and Kingsbury et al.,
2008) - Summary of Detections from Phase 1 8-47
Exhibit 8-27: Metolachlor Data from Source Water - Summary of Detections from Phase 2 -
Groundwater (Hopple et al., 2009) and Surface Water (Kingsbury et al., 2008) 8-47
Exhibit 8-28: Metolachlor Data from Public-Supply Wells (Toccalino et al., 2010) -
Summary of Detected Concentrations 8-48
Exhibit 8-29: Metolachlor Data from Public-Supply Wells (Toccalino et al., 2010) -
Summary of Samples 8-48
Exhibit 8-30: Wisconsin Groundwater Detections of Metolachlor 8-50
Exhibit 8-31: Metolachlor Occurrence Data from the PGWDB, 1971-1991 8-50
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Abbreviations
ARP
Acetochlor Registration Partnership
BW
Body Weight
CAR
Constitutive Androstane Receptor
CARC
Cancer Assessment Review Committee
CAS
Chemical Abstracts Service
CCL 3
Third Contaminant Candidate List
CCL 4
Fourth Contaminant Candidate List
CCR
Consumer Confidence Report
CDC
Centers for Disease Control and Prevention
CDR
Chemical Data Reporting
CSF
Cancer Slope Factor
CWS
Community Water System
CWSS
Community Water System Survey
DL
Detection Limit
DWI
Drinking Water Intake
DWTP
Drinking Water Treatment Plant
EPA
Environmental Protection Agency
ESA
Ethanesulfonic Acid
FQPA
Food Quality Protection Act
GAC
Granular Activated Carbon
GC/MS
Gas Chromatography/Mass Spectrometry
HA
Health Advisory
HHRA
Human Health Risk Assessment
HRL
Health Reference Level
HSDB
Hazardous Substances Data Bank
ICR
Information Collection Request
IRIS
Integrated Risk Information System
IUR
Inventory Update Reporting
Kh
Henry's Law Constant
Koc
Organic Carbon Partitioning Coefficient
Kow
Octanol-Water Partitioning Coefficient
LCMRL
Lowest Concentration Minimum Reporting Level
LEL
Lowest Effect Level
LOAEL
Lowest Observed Adverse Effect Level
LOD
Limit of Detection
LOQ
Limit of Quantitation
LT-MDL
Long-Term Method Detection Level
MDL
Method Detection Limit
MOA
Mode of Action
MOE
Margin of Exposure
MRL
Minimum Reporting Level
MTBE
Methyl Tert-Butyl Ether
NASQAN
National Stream Quality Accounting Network
NAWQA
National Water-Quality Assessment
NCFAP
National Center for Food and Agricultural Policy
ND
Not Detected
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NDI
Negligible Daily Intake
NHANES
National Health and Nutrition Examination Survey
NIRS
National Inorganics and Radionuclides Survey
NOAEL
No Observed Adverse Effect Level
NOEL
No Observed Effect Level
NPDWR
National Primary Drinking Water Regulation
NPS
National Pesticide Survey
NREC
National Reconnaissance for Emerging Contaminants
NWIS
National Water Information System
OA
Oxanilic Acid
OPP
Office of Pesticide Programs
OPPTS
Office of Prevention, Pesticide and Toxic Substances
PA
Principal Aquifer
PDP
Pesticide Data Program
PGWDB
Pesticides in Ground Water Database
PMP
Pilot Monitoring Program
PMRA
Pest Management Regulator Agency
PWS
Public Water System
RED
Reregi strati on Eligibility Decision
RfD
Reference Dose
RSC
Relative Source Contribution
RSD
Relative Standard Deviation
SDWA
Safe Drinking Water Act
SDWIS
Safe Drinking Water Information System
SDWIS/Fed
Safe Drinking Water Information System/Federal Version
SIM
Selected Ion Monitoring
SOC
Synthetic Organic Compound
STORET
Storage and Retrieval Data System
SYR2
Second Six-Year Review
SYR3
Third Six-Year Review
TDI
Tolerable Daily Intake
TOC
Total Organic Carbon
TRED
Tolerance Reassessment Progress and Risk Management Decision
TRI
Toxics Release Inventory
UCM
Unregulated Contaminant Monitoring
UCMR
Unregulated Contaminant Monitoring Rule
UCMR 1
First Unregulated Contaminant Monitoring Rule
UCMR 2
Second Unregulated Contaminant Monitoring Rule
UCMR 3
Third Unregulated Contaminant Monitoring Rule
UF
Uncertainty Factor
USD A
United States Department of Agriculture
USGS
United States Geological Survey
VOC
Volatile Organic Compound
WHO
World Health Organization
WI DATCP
Wisconsin Department of Agriculture, Trade and Consumer Protection
WQP
Water Quality Portal
WRD
Water Resources Discipline
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Chapter 8: Metolachlor
The Environmental Protection Agency (EPA) is evaluating metolachlor as a candidate for
regulation as drinking water contaminants under the fourth Contaminant Candidate List (CCL 4)
Regulatory Determinations process. Information on the CCL 4 process is found in Chapter 1.
Background on data sources used to evaluate CCL 4 chemicals is found in Chapter 2.
This chapter presents information and analyses specific to metolachlor, including
background information on the contaminants, information on contaminant sources and
environmental fate, an analysis of health effects, an analysis of occurrence in ambient and
drinking water, and information about the availability of analytical methods and treatment
technologies.
8.1 Contaminant Background and Chemical and Physical Properties
Metolachlor (2-chl oro-A-(2-ethyl-6-methyl phenyl )-A-(2-methoxy-l -methylethyl) is a
chloroacetanilide pesticide that is used as an herbicide for weed control. Initially registered in
1976 for use on turf, metolachlor has more recently been used on corn, cotton, peanuts, pod
crops, potatoes, safflower, sorghum, soybeans, stone fruits, tree nuts, non-bearing citrus, non-
bearing grapes, cabbage, certain peppers, buffalograss, guymon bermudagrass for seed
production, nurseries, hedgerows/fencerows, and landscape plantings. In April of 1995, EPA's
Office of Prevention, Pesticide and Toxic Substances (OPPTS) released a Reregi strati on
Eligibility Decision (RED) for metolachlor (USEPA, 1995a) and a Tolerance Reassessment
Progress and Risk Management Decision (TRED) was released in June of 2002 (USEPA,
2002a). A pesticide tolerance for S-metolachlor was issued in 2005 (USEPA, 2005a).
Metolachlor and S-metolachlor are under registration review (USEPA, 2014a). In 2012, EPA
reinstated tolerances for metolachlor on popcorn to rectify an omission of these tolerances in
previous documentation (USEPA, 2012a). Synonyms for metolachlor include dual and bicep,
according to the Hazardous Substances Data Bank (HSDB, 2012).
As a compound containing one chiral carbon atom, metolachlor can exist in right- and
left-handed versions (enantiomers), designated R- and S-. Unless otherwise specified,
information about metolachlor in the literature, as summarized in this chapter, is presumed to
pertain to the racemic mixture (in which both enantiomers are present in equal proportions). S-
metolachlor is a form of metolachlor comprised of 88 percent S-enantiomer and 12 percent R-
enantiomer (HSDB, 2012). When manufacturers found a way of producing metolachlor that was
predominantly the "S-" enantiomer in the late 1990s, they began marketing that as "S-
metolachlor," while the more evenly balanced mixture continues to be sold as "metolachlor"
(Hartzler, 2004).
Metolachlor is included in EPA's Office of Prevention, Pesticides and Toxic Substances
(OPPTS) June 2007 list of Pesticide Active Ingredients and Pesticide Inerts initially selected for
Tier I screening for potential endocrine disruption. This list of 67 chemicals, published in the
Federal Register (USEPA, 2009a), identified the first candidates for study and should not be
construed as a list of known or likely endocrine disruptors.
Exhibit 8-1 presents the chemical structure of metolachlor. Physical and chemical
properties and other reference information are listed in Exhibit 8-2.
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Final Regulatory Determination 4 Support Document - Ch 8, Metolachlor
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Exhibit 8-1: Chemical Structure of Metolachlor
ch3 o
Source: USEPA, 2019a
Exhibit 8-2: Physical and Chemical Properties of Metolachlor
Property
Information
Chemical Abstracts
Service (CAS) Registry
Number
51218-45-2 (ChemlDPIus, 2018)
EPA Pesticide Chemical
Code
108801 (USEPA, 2014a)
Chemical Formula
C15H22CINO2 (ChemlDPIus, 2018)
Molecular Weight
283.79 g/mol (HSDB, 2012)
Color/Physical State
Clear liquid; colorless to tan liquid (HSDB, 2012)
Boiling Point
282 deg C (RAIS, 2018)
Melting Point
-62.1 deg C (HSDB, 2012)
Density
1.12 g/mL at 20 deg C (HSDB, 2012)
Freundlich Adsorption
Coefficient
98,200 (|ig/g)(L/|ig)1/n (Speth et al., 2001)
Vapor Pressure
3.14E-05 mm Hg at 25 deg C (HSDB, 2012)
Henry's Law Constant
9.0E-09 atm-m3/mol at 20 deg C (HSDB, 2012)
Log Kow
3.13 (dimensionless) (HSDB, 2012)
Koc
22-2,320 L/kg (HSDB, 2012)
488 L/kg (RAIS, 2018)
Solubility in Water
530 mg/L at 20 deg C (HSDB, 2012)
Other Solvents
Soluble in many organic solvents (HSDB, 2012)
Conversion Factors
(at 25 deg C, 1 atm)
Not of sufficient volatility for conversion to be applicable
Note: Many of these properties are temperature dependent. Values are given for properties at 20-25 deg C unless
otherwise noted. Due to varying experimental conditions, and due to the variabilities associated with modeling, the
standard information sources may provide a range of values. Where more than one value was available from these
sources, one value was selected for this table based on best professional judgment.
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8.2 Sources and Environmental Fate
8.2.1 Production, Use, and Release
Production data from EPA's Inventory Update Reporting (IUR) and Chemical Data
Reporting (CDR) programs are not available for metolachlor. No industrial release data for
metolachlor are available from EPA's Toxics Release Inventory (TRI). (The list of chemicals for
which TRI reporting is required has never included metolachlor (USEPA, 2016a).) Additional
information about these sources is provided in Chapter 2.
EPA Office of Pesticide Programs (OPP) Pesticide Registration Documentation
Based on private market usage data, EPA has estimated that approximately 9 million
pounds of metolachlor active ingredient and 28 million pounds of S-metolachlor active
ingredient were applied annually between 1998 and 2012, both of them mostly on corn (USEPA,
2014a).
EPA Pesticide Industry Sales and Usage Report
EPA's Pesticide Industry Sales and Usage reports state that the amount of metolachlor
active ingredient, used in the United States was between 45 and 50 million pounds in 1987;
between 63 and 69 million pounds in 1997; between 26 and 30 million pounds in 1999; between
15 and 22 million pounds in 2001; between 1 and 5 million pounds on 2009; and between 4 and
8 million pounds in 2012. Furthermore, the amount of S-metolachlor used was between 16 and
19 million pounds in 1999; between 20 and 24 million pounds in 2001; between 28 and 33
million pounds in 2003; between 27 and 32 million pounds in 2005; between 30 and 35 million
pounds in 2007; between 24 and 34 million pounds in 2009; and between 34 and 44 million
pounds in 2012 (USEPA, 2004a; USEPA, 2011a; USEPA, 2017).
National Center for Food and Agricultural Policy (NCFAP) Pesticide Use Database
NCFAP maintains a national Pesticide Use Database, primarily for herbicides. Pesticide
use estimates are based on state-level commercial agriculture usage patterns and state-level crop
acreage. NCFAP lists uses of metolachlor on 16 crops totaling approximately 59 million pounds
of active ingredient per year in 48 states in 1992, and lists uses on 21 crops totaling 67 million
pounds of active ingredient per year in 48 states in 1997 (NCFAP, 2000).
United States Geological Survey (USGS) Pesticide Use Maps
USGS has produced maps of pesticide use for over 200 compounds used in United States
crop production. The pesticide use maps show the average annual pesticide use intensity
expressed as average weight (in pounds) of a pesticide applied to each square mile of agricultural
land in a county. The USGS maps were created using data from NCFAP and county-level
information on harvested crop acreage from the Census of Agriculture.
Exhibit 8-3 and Exhibit 8-4 (USGS, 2018) show the geographic distribution of estimated
average annual metolachlor and S-metolachlor use in the United States in 2016. A breakdown of
use by crop from year to year is also included with each map. The maps indicate that metolachlor
and S-metolachlor use is fairly common throughout much of the United States, and heaviest in
the Midwest. The breakdown of use shows a sharp decline in metolachlor use between 1997 and
2002 followed by slow growth, and a sharp increase in S-metolachlor use in the same 1997-2002
timeframe, followed by steady growth since 2008.
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Final Regulatory Determination 4 Support Document — Ch 8, Metolachlor
January 2021
Exhibit 8-3: Estimated Annual Agricultural Use of Metolachlor, 2016
Estimated Agricultural Use for Metolachlor, 2016 (Preliminary)
EPest-Low
Estimated Agricultural Use for Metolachlor, 2016 (Preliminary)
Estimated use on
agricultural land. In
pounds per square mile
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Cotton
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Soybeans
Com
csico^mtor^cooioi-csicoTincor^coOTOi-csicoTmco
01010)010)0)010100000000001-1-1-1-1-1-1-
0)0)010)0)01010)00000000000000000
¦ I— I— I— I— 1— i— (\l (SI (SI (M (SI (SI CM <\1 (SI
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EPA - OGWDW Final Regulatory Determination 4 Support Document — Ch 8, Metolachlor January 2021
Exhibit 8-4: Estimated Annual Agricultural Use of S-Metolachlor, 2016
Estimated Agricultural use for Metolachlor-S , 2016 (Preliminary)
EPest-Low
4g1Uullur.1l h
0 >66
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I INo estimated jse
Use by Year and Crop
nl
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(si co m to r~-co er> o t—
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Final Regulatory Determination 4 Support Document - Ch 8, Metolachlor
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documented in soils, plants, and animals (Feng, 1991; Rebich et al., 2004). An alternative
metabolic pathway beginning with oxidation has also been observed in animals (Feng, 1991).
Microbial activity and herbicide degradation typically increase as temperature increases
(Aga and Thurman, 2001); empirical studies have confirmed this in the case of acetochlor
(Dictor et al., 2008; Dictor et al., 2003).
Moisture also affects glutathione conjugation and chloroacetanilide degradation rates
(Rebich et al., 2004; Aga and Thurman, 2001); empirical studies have confirmed that some
chloroacetanilides degrade faster in soils with higher moisture content (Aga and Thurman, 2001).
As discussed in Chapter 2, the measures used by EPA to assess mobility include (where
available) the organic carbon partitioning coefficient (Koc), log octanol-water partitioning
coefficient (log Kow), Henry's Law Constant (Kh), water solubility, and vapor pressure.
Metolachlor is directly released to the environment through its use as an herbicide. The vapor
pressure of metolachlor indicates that if it were released to the air, it would be present in both the
vapor and the particulate phases in the ambient atmosphere. Metolachlor may be removed from
the atmosphere physically through wet and dry deposition (HSDB, 2012).
Due to the relatively low soil/water partitioning coefficients for metolachlor, the
compound is expected to be moderately to highly mobile in soil. EPA's Reregi strati on Eligibility
Decision document indicates that substantial leaching of metolachlor from soil by run-off is
expected to occur. The mobility of metolachlor in soil varies depending on the characteristics of
the soil where it is applied: high organic content may increase sorption (USEPA, 1995a).
Volatilization is expected to be a minor environmental pathway from moist soils and water based
on its Henry's Law Constant, and from dry soil surfaces based on its vapor pressure.
During a 10-day field study in moist soil, broadcast treatment resulted in a 22 percent loss
and banded treatment resulted in a 6 percent loss (HSDB, 2012). Metolachlor may also degrade
due to photolysis on the soil surface (HSDB, 2012). A photolysis half-life of 8-22 days has been
observed for metolachlor in soil exposed to natural sunlight (USEPA, 1995a; HSDB, 2012). A
photolysis half-life of 11 days was reported for a lake in summer conditions and humic
substances were reported to retard photolysis. Hydrolysis is not expected to be important with a
half-life estimated at 210 days for metolachlor (HSDB, 2012). Half-lives under aerobic and
anaerobic conditions in a sandy loam soil are reported as 67 days and 81 days, respectively
(USEPA, 1995a; HSDB, 2012). An aerobic, aquatic biodegradation half-life of 47 days and an
anaerobic, aquatic biodegradation half-life of 78 days have also been reported (HSDB, 2012).
Chapter 2 presents scales used by EPA to informally rank chemical contaminants' likely
mobility (understood as their tendency to partition to water rather than other media) and
persistence as "high," "moderate," or "low" based on physical and chemical properties (see
Exhibit 2-2 and Exhibit 2-3). For metolachlor, a log Kow of 3.13, a Koc of 488 L/kg and a water
solubility of 530 mg/L indicate a moderate likelihood of partitioning to water (however, a wide
range of values for Koc are presented in various sources, indicating low to high likelihoods of
partitioning to water). A Kh of 9.0E-09 atm-m3/mol indicates a high likelihood of partitioning to
water. The aerobic biodegradation/biotransformation1 half-lives of 67 and 47 days in soil and
1 For the chloroacetanilides, formation of the ESA and OA derivatives is less a degradative process and more a
transformation process. Formation of the ESA and OA derivatives does not result in degradation of the parent
structure; rather, it creates a chemical derivative. Thus, the word "transformation" is more appropriate than the word
"degradation."
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water, respectively, indicate moderate to high persistence under aerobic conditions. The
anaerobic half-lives of 81 and 78 days in soil and water, respectively, indicate high persistence
under anaerobic conditions.
8.3 Health Effects
8.3.1 Toxicokinetics
Metolachlor is absorbed and metabolized following oral administration. Between 70
percent and 93 percent of the administered dose was absorbed in rats. Residual levels of
metolachlor were detected in the carcass and red blood cell of rats at seven days post-dose and
no apparent bioaccumulation was detected. A significant portion of metolachlor is excreted
through urine and feces in rats following oral administration (USEPA, 2018). Potential sex
differences in excretion of metolachlor have been observed in low dose groups, with higher rates
of excretion in urine in female rats and higher fecal excretion in males. No sex-related
differences in excretion were observed in high dose groups. Up to 32 metolachlor metabolites
were detected in urine and/or feces (USEPA, 2018). Metabolites found in urine and feces
indicate that metolachlor is transformed via cleavage of its ether bond, followed by oxidation of
its carboxylate functional group and hydrolytic removal of its chlorine atom (USEPA, 1995a;
USEPA, 2018).
Available studies indicate that S-metolachlor is absorbed and metabolized following oral
administration (USEPA, 2018). The predominant elimination route is through urine and feces. S-
metolachlor was predominantly excreted through the fecal route versus urine regardless of dose,
sex, or repeated exposure (USEPA, 2018). Between 35 percent and 39 percent of S-metolachlor
was absorbed in males, whereas 43 to 49 percent was absorbed in females. The majority (-85
percent) of the dose was recovered in urine, bile fluid, and tissues within 48 hours of dosing
(USEPA, 2018). Dermal absorption of up to 62.8 percent of the administered dose was observed
in rats at 24 hours. About 30 percent of the dose was found to accumulate in the carcass
(USEPA, 1995a). Metolachlor has an estimated dermal absorption factor of 58 percent based on
a dermal absorption study in rats (USEPA, 2018).
8.3.2 Available Health Effects Assessments
Exhibit 8-5 presents a summary of the available health effects assessments for
metolachlor. As indicated by the bolded row, the 2018 OPP assessment (USEPA, 2018) was
selected for use in the calculation of the Health Reference Level (HRL) (see Section 8.3.4 below
for details on that calculation).
Exhibit 8-5: Available Health Effects Assessments for Metolachlor
Health
Assessment
Assessment
Year
Reference
Dose
(RfD)
(mg/kg/
day)
Principal Study
for RfD
Cancer
Slope
Factor
(CSF)
(mg/kg/
day)1
Principal
Study for
CSF
Cancer Descriptor
EPA OPP
Human
Health Risk
Assessment
(HHRA)
2018
0.26
Page (1981);
MRID 00080897
No Value
NA
"Not Likely to be
Carcinogenic to
Humans"
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Health
Assessment
Assessment
Year
Reference
Dose
(RfD)
(mg/kg/
day)
Principal Study
for RfD
Cancer
Slope
Factor
(CSF)
(mg/kg/
day)1
Principal
Study for
CSF
Cancer Descriptor
EPA
Integrated
Risk
Information
System (IRIS)
1990
0.15
Tisdel (1983);
MRID 00129377
No Value
NA
Group C (suggestive
evidence of
carcinogenic
potential)
EPA Health
Advisory (HA)
1988
0.15
Tisdel (1983);
MRID 00129377
No Value
NA
Group C (suggestive
evidence of
carcinogenic
potential)
World Health
Organization
(WHO)
Drinking
Water
Guideline
2003
0.0035
Hazelette, J.
(1989); MRID
40980701
No Value
NA
No Value
Health
Canada
1990
0.005
Tisdel (1983);
MRID 00129377
No Value
NA
No Value
8.3.3 Health Effects
Systemic (Non-cancer)
Metolachlor is slightly toxic through oral, dermal, and inhalation routes (USEPA, 1995a).
In subchronic (metolachlor and S-metolachlor) (USEPA, 1995a; USEPA, 2018) and chronic
(metolachlor) (Hazelette, 1989; Tisdel, 1983; Page, 1981; USEPA, 2018) toxicity studies in dogs
and rats, decreased body weight was the most commonly observed effect. Chronic exposure to
metolachlor in rats also resulted in increased liver weight and microscopic liver lesions in both
sexes (USEPA, 2018). No systemic toxicity was observed in rabbits when metolachlor was
administered dermally, though dermal irritation was observed at lower doses (USEPA, 2018).
Portal of entry effects (e.g., hyperplasia of the squamous epithelium and mucous cell) occurred
in the nasal cavity at lower doses in a 28-day inhalation study in rats (USEPA, 2018). Systemic
toxicity effects were not observed in this study. Immunotoxicity effects were not observed in
mice exposed to S-metolachlor (USEPA, 2018).
The Integrated Risk Information System (IRIS) identified an oral reference dose (RfD)
for metolachlor of 0.15 mg/kg/day based on a two-year rat feeding study in which decreased
body weight gain was identified as the critical effect (Tisdel, 1983). Dietary concentrations of
metolachlor were approximately 0, 1.5, 15, or 150 mg/kg/day. The No Observed Adverse Effect
Level (NOAEL) of 15 mg/kg/day was based on decreased body weight gain in rats fed 150
mg/kg/day of metolachlor (the highest dose tested). An uncertainty factor (UF) of 100 was used
in the extrapolation of the dose levels for interspecies extrapolation (10) and intraspecies
variation (10). An increase in testicular atrophy was detected in male rats at the same Lowest
Observed Adverse Effect Level (LOAEL) (USEPA, 1988). In 2004, EPA announced that
pesticides will not be re-assessed by the IRIS program (USEPA, 2004b).
The testicular atrophy observed in Tisdel (1983) was previously considered the critical
effect, resulting in an RfD of 0.15 mg/kg/day based on a NOAEL of 15 mg/kg/day (USEPA,
1988) with a UF of 100. It was later determined that this effect was not considered to be of
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toxicological significance due to its occurrence in historical controls (USEPA, 1990a). This
chronic toxicity study also served as the critical study for Health Canada's determination of the
negligible daily intake (NDI) of 0.005 mg/kg/day for metolachlor. This value was derived by
applying an uncertainty factor of 300 to the NOAEL of 1.5 mg/kg/day for decreased body weight
(Health Canada, 1990). Nasal tumors were observed in the male rats of this study according to
WHO (2003). Health Canada's Pest Management Regulator Agency (PMRA) announced a plan
for re-evaluation of Metolachlor in June 2018, which will include updates to its human health
risk assessment. As part of this re-evaluation plan, new assessments for metolachlor toxicology
and exposure are projected to be published for comment by March 2020 (Health Canada, 2018).
The World Health Organization (WHO) determined a tolerable daily intake (TDI) for
metolachlor of 3.5 |ig/kg-day based on a one-year study in dogs (Hazelette, 1989). The TDI was
derived from a NOAEL of 3.5 mg/kg/day for decreased body weight. Decreased kidney weight
was also detected. An uncertainty factor of 1000 was applied to the NOAEL to account for inter-
and intraspecies variation (100) and some concern for carcinogenicity (10) (WHO, 2003).
In 2014, the EPA Office of Pesticide Programs (OPP) determined a chronic RfD for
metolachlor of 0.097 mg/kg/day based on a chronic toxicity study in dogs (Hazelette, 1989) in
which decreased weight gain was observed in females. The RfD was derived from a NOAEL of
9.7 mg/kg/day with a UF of 100 applied to account for interspecies (10) and intraspecies
variability (10), and a Food Quality Protection Act (FQPA) Safety Factor of 1 (USEPA, 2014a).
OPP re-evaluated Hazelette (1989) data and determined that observed changes in body
weight gain were not adverse as they were less than 10 percent throughout the study (USEPA,
2018).
Developmental/Reproductive
In a two-generation reproduction study in albino rats (Page, 1981), metolachlor showed
some evidence of developmental and reproductive toxicity. Another developmental toxicity
study in Sprague-Dawley rats demonstrated decreases in mean fetal body weight and in the
number of implantations (with resulting decreases in litter size) at doses of 1,000 mg/kg/day
(Lochry, 1985). Increases in resorption per dam and post-implantation loss were also detected
(USEPA, 1995a). EPA's 2018 HHRA does not describe a developmental LOAEL in this two-
generation study due to small effect sizes and other considerations (a less than 5% decrease in
bodyweight, dosing occurring after implementation, resorption rates within the range observed in
the test facility). Decreases in pup body weight in the Page (1981) study were considered
significant and adverse (USEPA, 2018). Decreased pup body weight was observed in male and
female pups of the F1 and F2 litters, while no effects were observed in the dams (USEPA, 2018).
Reductions in pup weights at the highest dose tested (1,000 ppm or 75.8-85.7 mg/kg/day) were
also observed in this study (Page, 1981).
Developmental and reproductive effects were also examined by Tisdel (1983). Mice
received concentrations of 0, 300, 1,000, or 3,000 ppm (0, 1.5, 15, or 150 mg/kg/day)
metolachlor in the food. The authors identified the No Observed Effect Level (NOEL) and the
Lowest Effect Level (LEL) for reproductive toxicity to be 300 and 1000 ppm (15 and 50
mg/kg/day), respectively, based on significant reductions in pup weight and decreased parental
food consumption.
A recent OPP human health risk assessment (USEPA, 2018) identified a two-generation
reproduction study in rats (Page, 1981) as the critical study (USEPA, 2018). OPP proposed an
RfD for metolachlor of 0.26 mg/kg/day, derived from a NOAEL of 26 mg/kg/day for decreased
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pup body weight with a UF of 100, applied to account for interspecies extrapolation (10) and
intraspecies variation (10), and an FQPA Safety Factor of 1. This RfD is considered protective of
carcinogenic effects as well as effects observed in chronic toxicity studies (USEPA, 2018).
Cancer Data and Classification
Metolachlor was classified in IRIS (USEPA, 1990a) as a Group C possible human
carcinogen based on the appearance of proliferative liver lesions in female rats observed by
Tisdel et al. (1983), in accordance with the 1986 Guidelines for Carcinogen Risk Assessment
(USEPA, 1986). WHO applied an uncertainty factor of 10 in its derivation of the metolachlor
TDI due to carcinogenicity concerns (WHO, 2003).
Although treatment with metolachlor did not result in an increase in treatment-related
tumors in male rats or in mice (both sexes), metolachlor caused an increase in liver tumors in
female rats (USEPA, 2018). There was no evidence of mutagenic or cytogenetic effects in vivo
or in vitro (USEPA, 2018). In 1994 (USEPA, 1995a), EPA classified metolachlor as a Group C
possible human carcinogen, in accordance with the 1986 Guidelines for Carcinogen Risk
Assessment (USEPA, 1986). In 2017 (USEPA, 2018), EPA re-assessed the cancer classification
for metolachlor in accordance with EPA's final Guidelines for Carcinogen Risk Assessment
(USEPA, 2005b), and reclassified metolachlor/S-metolachlor as "Not Likely to be Carcinogenic
to Humans" at doses that do not induce cellular proliferation in the liver. This classification was
based on convincing evidence of a constitutive androstane receptor (CAR)-mediated mitogenic
MOA for liver tumors in female rats that supports a nonlinear approach when deriving a
guideline that is protective for the tumor endpoint (USEPA, 2018).
Potentially Sensitive Groups/Lifestages
The two-generation reproduction study Page (1981) demonstrated decreases in pup body
weight in the absence of maternal effects, indicating reproductive toxicity (USEPA, 2018).
Therefore, sensitive lifestages to consider include infants, pregnant women and their fetuses, and
lactating women.
8.3.4 Basis of the HRL
The most recent EPA metolachlor assessment is a human health risk assessment for S-
metolachlor by the EPA OPP, which is based on a chronic study evaluating metolachlor
exposure in rats (Page, 1981; USEPA, 2018). EPA has concluded that it is appropriate to
combine the metolachlor toxicology database with that of S-metolachlor and that any studies in
the database could be used to assess toxicity for metolachlor or S-metolachlor (USEPA, 2018).
The risk assessment identified an oral RfD for metolachlor of 0.26 mg/kg/day based on a
two-generation reproduction study in rats. The RfD was derived from a NOAEL of 26
mg/kg/day based on decreased pup body weight in the F1 and F2 litters with a UF of 100 applied
to account for interspecies extrapolation (10) and intraspecies variation (10), and an FQPA
Safety Factor of 1. OPP determined that this RfD is considered protective of carcinogenic effects
as well as effects observed in chronic toxicity studies (USEPA, 2018).
Decreased F1 and F2 litter pup body weights in a two-generation reproduction study in
rats indicated increased susceptibility to the pups. Therefore, a drinking water intake rate of 0.15
L/kg/day was selected from the Exposure Factors Handbook (USEPA, 201 lb) to represent the
consumers-only estimate of combined direct and indirect community water ingestion at the 90th
percentile for bottle-fed infants. This intake estimate is more protective than the estimate for
pregnant women (0.033 mL/kg/day) or lactating women (0.054 L/kg/day). Drinking water intake
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and body weight parameters are further outlined in the Exposure Factors Handbook (USEPA,
2011b; USEPA, 2019b).
The EPA Office of Water derived a regulatory determination Health Reference Level
(HRL) for metolachlor of 300 |ig/L, based on the oral RfD of 0.26 mg/kg/day for bottle-fed
infants ingesting 0.15 L/kg/day water, with the application of a 20 percent relative source
contribution, as follows:
BW
HRL = RfD, — ,RSC
HRL = 0.26 , 20% = 0.347 mg/L
day
HRL =0.3 mg/L (rounded)
HRL = 300 \ig/L (rounded)
RfD = Reference Dose (mg/kg/day); toxicity value selected based on protocol hierarchy
BW / DWI = Body weight / Drinking Water Intake, from the reciprocal of intake per
body weight per day for bottle fed infants of 0.15 L/kg/day
RSC = Relative Source Contribution, or the level of exposure believed to result from
drinking water when compared to other sources (e.g., food, ambient air), is 20 percent
when used for HRL derivation.
8.3.5 Health Effects Data Gaps
The existing toxicological database comprises studies evaluating both metolachlor and S-
metolachlor. EPA has determined that the metolachlor toxicology database can be used to assess
S-metolachlor toxicity and vice versa. When combined with the toxicology database for
metolachlor, the toxicology database for S-metolachlor is considered complete for risk
assessment purposes (USEPA, 2018).
8.4 Occurrence
This section presents data on the occurrence of metolachlor in ambient water and
drinking water in the United States. As described in Section 8.3, a health reference level (HRL)
of 300 |ig/L was calculated for metolachlor based on non-carcinogenic effects. HRLs are risk-
derived concentrations against which EPA evaluates the occurrence data to determine if
contaminants occur at levels of potential public health concern. Occurrence data from various
sources presented below are analyzed with respect to the HRL and one-half the HRL. When
possible, estimates of the population exposed at concentrations above the HRL and above one-
half the HRL are presented.
For additional background information about data sources used to evaluate occurrence,
please refer to Chapter 2.
8.4.1 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the ambient sources of most drinking water. Contaminant
occurrence in ambient water provides information on the potential for contaminants to adversely
affect drinking water supplies. Occurrence data for metolachlor in ambient water are available
from the USGS National Water-Quality Assessment (NAWQA) program, the USGS National
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Water Information System (NWIS) database, EPA's legacy Storage and Retrieval Data System
(STORET) data available through the Water Quality Portal (WQP), and USGS's National
Reconnaissance for Emerging Contaminants (NREC). Occurrence data for metolachlor in
ambient water are also available from several published studies summarized below. Additional
ambient water data collected in connection with finished drinking water data are presented in
Section 8.4.2.
United States Geological Survey (USGS') National Water-Quality Assessment (NAWQA)
Ambient Water Analyses
The USGS instituted the NAWQA program in 1991 to examine ambient water quality
status and trends in the United States. The NAWQA program generates high quality contaminant
occurrence and other water quality parameter data for significant watersheds and aquifers across
the nation. The program collects data on surface water and groundwater chemistry, hydrology,
land use, stream habitat, and aquatic life in parts or all of nearly all 50 States. The program is
designed to apply nationally consistent methods to provide a uniform basis for contaminant
occurrence comparisons and assessments among study basins across the country and over time.
The occurrence assessments can also serve to facilitate interpretation of natural and
anthropogenic factors affecting national water quality. For more detailed information on the
NAWQA program design and implementation, refer to Leahy and Thompson (1994) and
Hamilton et al. (2004).
The process of sampling, analysis, and data synthesis is divided into cycles of
approximately ten years: Cycle 1 covered 1991-2001, Cycle 2 covered 2002-2012, and Cycle 3 is
ongoing and covers 2013-2023. Study units are sampled and analyzed on a staggered schedule
within each cycle. Each NAWQA cycle begins with a two-year startup phase for planning and
retroactive analysis, followed by a three-year intensive data collection phase, and finally a five-
year phase for analyzing the data, developing reports, and continuing a low level of monitoring
(NRC, 2012).
During Cycle 1 (1991-2001), 51 study units were sampled. Data were gathered from
6,307 wells from 272 groundwater networks or clusters and from 6,400 sampling points at 505
surface water monitoring sites, primarily rivers and streams but also some lakes and reservoirs
(NRC, 2002). In Cycle 2 (2002-2012), the number of study units was reduced from 51 to 42
(NRC, 2012). Long-term stream monitoring was established at 113 streams representing 8 major
river basins. Long-term groundwater monitoring was established at sites representing 20
principal aquifers with more than 10 to 15 years of consistent monitoring data available (Rowe et
al., 2013).
Sampling for Cycle 3 is currently underway (2013-2023). Surface water monitoring will
be conducted at 313 sites, increased from 113 sites in Cycle 2 (Rowe et al., 2013). Groundwater
assessments in Cycle 3 will be designed to evaluate status and trends at the principal aquifer
(PA) and national scales. Assessments are planned in 24 PAs that account for the majority of
current and future national groundwater use for drinking water. Data available through 2017 are
presented in this report. For more details on the Cycle 3 sampling design, refer to Rowe et al.
(2010 and 2013).
EPA's analysis of the NAWQA data is a simple, non-parametric occurrence analysis that
provides summary statistics to characterize contaminant occurrence. EPA calculated detection
frequencies as the percentage of samples and the percentage of sites with at least one detection,
without any censoring or weighting. (A detection is an analytical result equal to or greater than
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the reporting level.) EPA reported the minimum and maximum detected concentrations and
calculated other descriptive statistics including the median, 90th percentile, and 99th percentile
concentrations (based only on samples with detections). Reporting levels varied over time during
the NAWQA program. In some cases, therefore, the minimum concentration reported as a
detection could be lower than the highest reporting level.
Exhibit 8-6 through Exhibit 8-8 present analyses of the metolachlor NAWQA data,
downloaded from the WQP in September 2018 (WQP, 2018). In Cycle 1, metolachlor was
detected in approximately 53 percent of samples (12,745 out of 24,043) and at approximately 25
percent of sites (1,857 out of 7,562). The median concentration based on detections was 0.033
|ig/L. In Cycle 2, metolachlor was detected in 51 percent of samples (10,334 out of 20,396) and
at 17 percent of sites (759 out of 4,536). The median concentration based on detections in Cycle
2 was 0.024 |ig/L. In Cycle 3 (through 2017), metolachlor was detected in 57 percent of samples
(5,954 out of 10,523) and at 20 percent of sites (350 out of 1,756). The median concentration
based on detections in Cycle 3 was 0.037 |ig/L. (Some sites were sampled in more than one
cycle.) There were no exceedances of one-half the HRL or the HRL in any of the three cycles of
NAWQA data. As noted above, NAWQA data are ambient water data, not finished drinking
water data.
Note that there may be some overlap between the NAWQA data assessment presented
here and summaries of individual NAWQA studies presented below.
Exhibit 8-6: Metolachlor NAWQA Data - Summary of Detected Concentrations
Site Type
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Cycle 1 (1991 -2001)
Groundwater
0.001
0.010
0.164
2.31
32.8
Surface Water
0.001
0.036
0.743
7.75
77.6
All Sites
0.001
0.033
0.690
7.30
77.6
Cycle 2 (2002-2012)
Groundwater
0.001
0.009
0.106
2.37
16.1
Surface Water
0.0005
0.027
0.368
2.41
15.1
All Sites
0.0005
0.024
0.347
2.41
16.1
Cycle 3 (2013-2017)
Groundwater
0.0005
0.004
0.104
0.50
1.42
Surface Water
0.0004
0.038
0.802
7.45
91
All Sites
0.0004
0.037
0.784
7.32
91
Source: WQP, 2018
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Exhibit 8-7: Metolachlor NAWQA Data - Summary of Samples
Site Type
No. of
Samples
Detection Frequency
(detections are results > reporting level)
No. of
Samples
with
Detections
%
Samples
with
Detections
No. of
Samples
with
Detections
> 1/2 HRL
%
Samples
with
Detections
> 1/2 HRL
No. of
Samples
with
Detections
> HRL
%
Samples
with
Detections
> HRL
Cycle 1 (1991 -2001)
Groundwater
7,106
913
12.85%
0
0.00%
0
0.00%
Surface Water
16,937
11,832
69.86%
0
0.00%
0
0.00%
All Sites
24,043
12,745
53.01%
0
0.00%
0
0.00%
Cycle 2 (2002-2012)
Groundwater
6,707
695
10.36%
0
0.00%
0
0.00%
Surface Water
13,689
9,639
70.41%
0
0.00%
0
0.00%
All Sites
20,396
10,334
50.67%
0
0.00%
0
0.00%
Cycle 3 (2013-2017)
Groundwater
1,516
93
6.13%
0
0.00%
0
0.00%
Surface Water
9,007
5,861
65.07%
0
0.00%
0
0.00%
All Sites
10,523
5,954
56.58%
0
0.00%
0
0.00%
Source: WQP, 2018
Exhibit 8-8: Metolachlor NAWQA Data - Summary of Sites
Site Type
No. of
Sites
Detection Frequency
(detections are results > reporting level)
No. of
Sites with
Detections
% Sites
with
Detections
No. of
Sites with
Detections
> 1/2 HRL
% Sites
with
Detections
> 1/2 HRL
No. of
Sites with
Detections
> HRL
% Sites
with
Detections
> HRL
Cycle 1 (1991 -2001)
Groundwater
5,659
652
11.52%
0
0.00%
0
0.00%
Surface Water
1,904
1,205
63.29%
0
0.00%
0
0.00%
All Sites
7,562
1,857
24.56%
0
0.00%
0
0.00%
Cycle 2 (2002-2012)
Groundwater
4,112
469
11.41%
0
0.00%
0
0.00%
Surface Water
424
290
68.40%
0
0.00%
0
0.00%
All Sites
4,536
759
16.73%
0
0.00%
0
0.00%
Cycle 3 (2013-2017)
Groundwater
1,440
90
6.25%
0
0.00%
0
0.00%
Surface Water
316
260
82.28%
0
0.00%
0
0.00%
All Sites
1,756
350
19.93%
0
0.00%
0
0.00%
Source: WQP, 2018
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NA WQA Pesticide National Synthesis Project, 1992-2001
Through a series of National Synthesis efforts, the USGS NAWQA prepares
comprehensive analyses of data on topics of particular concern. These National Synthesis
assessments aggregate NAWQA contaminant occurrence and water quality parameter data from
individual study units and other sources to provide a national overview. The NAWQA Pesticide
National Synthesis Project is a national-scale assessment of the occurrence and behavior of
pesticides in streams and groundwater of the United States and the potential for pesticides to
adversely affect drinking water supplies or aquatic ecosystems.
Results from the Pesticide National Synthesis analysis, based on complete Cycle 1 (1992-
2001) data from NAWQA study units, are posted on the NAWQA Pesticide National Synthesis
website (Gilliom et al., 2007).2 Data for surface water and groundwater are presented separately,
and results in each category are subdivided by land use category. Land use categories include
agricultural, urban, mixed (deeper aquifers of regional extent in the case of groundwater), and
undeveloped. The Pesticide National Synthesis analysis is a first step toward the USGS goals of
describing the occurrence of pesticides in relation to different land use and land management
patterns, and developing a deeper understanding of the relationship between spatial occurrence
of contaminants and their fate, transport, persistence, and mobility characteristics.
The surface water summary data presented in the Pesticide National Synthesis (Gilliom et
al., 2007) only includes stream data. Sampling data from a single one-year period, generally the
year with the most complete data, were used to represent each stream site. Sites with few data or
significant gaps were excluded from the analysis. NAWQA stream sites were sampled repeatedly
throughout the year to capture and characterize seasonal and hydrologic variability. Groundwater
data reported in the Pesticide National Synthesis only include samples from wells; data from
springs and agricultural tile drains were not included. In the National Synthesis analysis (Gilliom
et al., 2007), USGS uses a single sample to represent each well, generally the earliest sample
with complete data for the full suite of analytes.
Over the course of Cycle 1 (1992-2001), some NAWQA analytical methods were
improved or changed. Hence, detection thresholds varied over time for some compounds. USGS
used the maximum Long-Term Method Detection Level (LT-MDL) for each analyte as a
uniform reporting threshold. The maximum LT-MDL for metolachlor was 0.006 |ig/L (Gilliom
et al., 2007). Metolachlor was an analyte in the Pesticide National Synthesis Project.
In NAWQA stream samples (Exhibit 8-9), metolachlor was found at frequencies ranging
from 40.05 percent of samples in undeveloped areas to 46.09 percent of samples in urban areas,
68.13 percent of samples in mixed land use settings, and 81.72 percent of samples in agricultural
settings. The 95th percentile concentration was 0.019 |ig/L in undeveloped areas, 0.046 |ig/L in
urban areas, 0.240 |ig/L mixed land use settings, and 1.200 |ig/L in agricultural settings. The
highest surface water concentration, 77.600 |ig/L.
2 All the National-Synthesis Assessments (Pesticides, Nutrients, Volatile Organic Compounds (VOCs), Ecology,
and Trace Elements) were evaluated using Cycle 1 data. A major focus of NAWQA's Cycle 2 is on regional
assessments of groundwater quality conditions and trends. No companion Cycle 2 National Synthesis Assessment
reports were released.
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Exhibit 8-9: USGS National Synthesis Summary of NAWQA Monitoring of
Metolachlor in Streams, 1992-2001
Land Use
Type
Number of
Sites
Number of
Samples
Detection
Frequency
(Samples)
Concentration Values (of detections, in |jg/L)
Median
95th Percentile
Maximum
Agricultural
83
2,007
81.72%
0.029
1.200
77.600
Mixed
65
1,386
68.13%
0.008
0.240
16.400
Undeveloped
8
144
40.05%
ND
0.019
0.500
Urban
30
814
46.09%
ND
0.046
2.420
Source: Gilliom et al., 2007
ND = not detected (concentration is less than the maximum LT-MDL and is expected to be less than any higher
percentile concentration shown in the table).
In NAWQA groundwater samples (Exhibit 8-10), metolachlor was found at frequencies
ranging from 2.94 percent of samples in undeveloped areas to 4.87 percent of samples in mixed
land use settings, 8.87 percent of samples in urban areas, and 17.51 percent of samples in
agricultural settings. The 95th percentile concentrations were less than the maximum LT-MDL in
mixed and undeveloped settings. In urban and agricultural settings, the 95th percentile
concentrations were 0.005 |ig/L and 0.0231 |ig/L, respectively. The highest groundwater
concentration was 32.8 |ig/L.
Exhibit 8-10: USGS National Synthesis Summary of NAWQA Monitoring of
Metolachlor in Groundwater, 1992-2001
Land Use Type
Number of
Wells
Detection
Frequency
Concentration Values (of detections, in |jg/L)
Median
95th Percentile
Maximum
Agricultural
1,405
17.51%
ND
0.0231
32.8
Mixed
2,729
4.87%
ND
ND
2.62
Undeveloped
34
2.94%
ND
ND
0.0045
Urban
857
8.87%
ND
0.005
2.09
Source: Gilliom et al., 2007
ND = not detected (concentration is less than the maximum LT-MDL and is expected to be less than any higher
percentile concentration shown in the table).
National Water Information System (NWIS) Data
The National Water Information System (NWIS) is the Nation's principal repository of
water resources data USGS collects from more than 1.5 million sites (USGS, 2016). NWIS-Web
is the general online interface to the USGS NWIS database. Discrete water-sample and time-
series data are available from sites in all 50 States, including 5 million water samples with 90
million water-quality results. All USGS water quality and flow data are stored in NWIS,
including site characteristics, streamflow, groundwater level, precipitation, and chemical
analyses of water, sediment, and biological media, though not all parameters are available for
every site. NWIS houses the NAWQA data and includes other USGS data from unspecified
projects. NWIS contains many more samples at many more sites than the NAWQA Program.
Although NWIS is comprised of primarily ambient water data, some finished drinking water data
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are included as well. This section presents analyses of non-NAWQA data in NWIS, downloaded
from the WQP in December 2017 (WQP, 2017). These data do not overlap with the results
presented in Exhibit 8-6 through Exhibit 8-8.
The results of the non-NAWQA NWIS metolachlor analyses are presented in Exhibit
8-11. Metolachlor was detected in approximately 37 percent of samples (18,265 out of 49,092
samples) and at approximately 25 percent of sites (3,871 out of 15,603 sites). The median
concentration based on detections was equal to 0.050 |ig/L. (Note that the NWIS data are
presented as downloaded; potential outliers were not evaluated or excluded from the analysis.)
Exhibit 8-11: Metolachlor NWIS Data, 1991 - 2016
Site Type
Detection Frequency
(detections are results > reporting level)
Concentration Values
(of detections, in |jg/L)
No. of
Samples
No. of
Samples
with
Detections
No. of
Sites
No. of
Sites with
Detections
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Groundwater
21,150
3,029
11,095
1,232
0
0.040
0.620
42.7
210
Surface
Water
27,893
15,223
4,530
2,647
0
0.056
1.21
11.3
376
Finished
Water
49
13
26
3
0.002
0.008
0.12
0.23
0.24
All Sites1
49,092
18,265
15,603
3,871
0
0.050
1.14
13.3
376
Source: WQP, 2017
1 The number of groundwater sites plus the number of surface water sites and finished water sites is not equal to "All
Sites" because some sites may have been listed with more than one source water type in the data.
Storage and Retrieval (STORET) Data / Water Quality Portal (WQP)
From its launch in 1999 until it was decommissioned in June 2018, EPA's STORET Data
Warehouse was collaboratively populated with raw biological, chemical, and physical data from
surface water and groundwater sampling by federal, state and local agencies, Native American
tribes, volunteer groups, academics, and others. Legacy STORET data are accessible through the
WQP: https://www.waterqualitvdata.us/portal/.
STORET data are from monitoring locations in all 50 states as well as multiple territories
and jurisdictions of the United States. Most data are from ambient waters, but in some cases
finished drinking water data are included as well. STORET's data quality limitations include
variations in the extent of national coverage and data completeness from parameter to parameter.
Data may have been collected as part of targeted, rather than randomized, monitoring.
This section presents analyses of STORET data, downloaded from the WQP in December
2017 (WQP, 2017). EPA reviewed STORET groundwater data from wells and surface water data
from lakes, rivers/streams, and reservoirs (WQP, 2017). The WQP also included public water
system (PWS) data from four states (Indiana, Missouri, Ohio, and Washington); EPA reviewed
these as well (WQP, 2017). It is unclear if the PWS data were collected prior to or subsequent to
treatment.
The results of the STORET analysis for metolachlor are presented in Exhibit 8-12
through Exhibit 8-14. These metolachlor samples were collected between 1980 and 2016. Of the
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6,201 sites sampled, 3,667 (59.1 percent) reported detections of metolachlor. Detected
concentrations ranged as high as 594 |ig/L. The 90th percentile concentration of detections was
equal to 1.3 |ig/L. The minimum detected concentration may be indicative of the reporting levels
used. (A minimum value of zero, on the other hand, could represent a detection that was entered
into the database as a non-numerical value (e.g., "Present").)
Exhibit 8-12: Metolachlor STORET Data - Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (|jg/L)
Minimum1
Median
90th Percentile
Maximum
Groundwater
0
0
0.14
594.325
Surface Water
0
0.13
1.3
133.2051
Total
0
0.11
1.3
594.325
PWS
0
0
0
0.68
Source: WQP, 2017
1A minimum value of zero may represent a detection that was entered into the database as a non-numerical value
(e.g., "Present").
Exhibit 8-13: Metolachlor STORET Data - Summary of Samples and Sites
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Total
Number
of Sites
Sites with Detections
Number
Percent
Number
Percent
Groundwater
6,924
2,537
36.64%
1,445
735
50.87%
Surface Water
68,778
34,647
50.38%
4,756
2,932
61.65%
Total
75,702
37,184
49.12%
6,201
3,667
59.14%
PWS
425
425
100.00%
180
180
100.00%
Source: WQP, 2017
Exhibit 8-14: Metolachlor STORET Data - Summary of States
Source Water
Type
Total
Number of
States
States with Detections
Number
Percent
Groundwater
16
9
56.25%
Surface Water
27
24
88.89%
Total1
29
26
89.66%
PWS
3
3
100.00%
Source: WQP, 2017
1 The number of states with groundwater data plus the number of
states with surface water data may not equal the "Total" number of
states providing data because some states provided both
groundwater and surface water data.
National Reconnaissance for Emerging Contaminants (NREC), 1999-2004
The USGS Water Resources Discipline (USGS WRD) prepared and provided various
water quality data to EPA for the deliberations and analyses used to develop the third
Contaminant Candidate List (CCL 3). One of the data sources, referred to as NREC (USEPA,
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2008a), includes water quality occurrence data collected by the USGS WRD Toxic Substances
Hydrology Program from 1999 to 2004. Data are included on approximately 100 chemicals,
including various pharmaceuticals (human and veterinary antibiotics, prescription and
nonprescription drugs), various industrial and household wastewater products (e.g., personal care
products), some pesticides and their degradates, and other wastewater-related compounds. There
are two components to the NREC data: the national reconnaissance data and the national
aggregate data. The national reconnaissance data came from nationally designed reconnaissance
surveys that collected samples from streams, wells, and other selected effluent sites from 30
states across the United States (and some of the data published in Kolpin et al., 2002; Focazio et
al., 2008; and Barnes et al., 2008). The national aggregate data include data from additional
sample collection and studies conducted by the WRD Science Centers from 36 states across the
country.
According to the national aggregate data from NREC, metolachlor occurred in 8.76
percent of the ambient surface water samples at a median concentration of 0.12 |ig/L, and in 1.23
percent of ambient groundwater samples at a median concentration of 0.125 |ig/L.
Acetochlor Registration Partnership (ARP), 1995-2001
As part of an agreement with EPA to maintain the registration of acetochlor and monitor
its environmental behavior, the ARP (an organization representing registrants Monsanto and
Dow AgroSciences) conducted an extensive monitoring program. From 1995-2001, ARP
compiled and analyzed water samples collected through the state groundwater and surface water
monitoring programs (de Guzman et al., 2005; Hackett et al., 2005). Samples were collected in
seven states (Illinois, Indiana, Iowa, Kansas, Minnesota, Nebraska, and Wisconsin) and were
analyzed for acetochlor and three other corn herbicides, including metolachlor. The limit of
detection (LOD) was 0.03 |ig/L for metolachlor.
Metolachlor was detected at 30 (16.5 percent) of 182 groundwater monitoring wells (de
Guzman et al., 2005). Maximum concentration values of metolachlor were not provided in the
groundwater study. Metolachlor was detected in 53 percent of samples in the surface water
study; however, maximum concentration values and annualized mean concentrations of
metolachlor were not provided in the surface water study (Hackett et al., 2005).
Additional Ambient Water Studies
As part of the USGS NAWQA Program and/or the National Stream Quality Accounting
Network (NASQAN), trends in the concentrations of 11 commonly occurring pesticides in the
Corn Belt of the United States were assessed at up to 31 stream sites for two time periods: 1996
through 2002 and 2000 through 2006. The 31 stream sites analyzed in this study are a subset of
201 sites that were sampled (Sullivan et al., 2009). Metolachlor concentrations showed a steeper
downtrend during the 1996 through 2002 time period and a less pronounced downward trend in
the 2000 through 2006 time period. The overall downward trend generally corresponded to
regional downtrends in the use of these herbicides in the Corn Belt from 1996 through 2006
(Sullivan et al., 2009). Although metolachlor concentrations declined, metolachlor prevalence
remained high in the Corn Belt streams. Detection rates of metolachlor at the 31 sites ranged
from 53 percent to 100 percent of samples in the 1996 through 2002 time period and from 56
percent to 100 percent of samples in the 2000 through 2006 time period, at a reporting level of
0.006 |ig/L. The majority of sites had greater than 85 percent detections of metolachlor. Note
that there may be some overlap between these data and the NAWQA data presented above.
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EPA's OPP released a RED document for metolachlor (USEPA, 1995a). The RED cites
data indicating that when ten lakes and reservoirs were monitored in or around 1993, the highest
metolachlor concentration found was 6.8 |ig/L.
8.4.2 Occurrence in Drinking Water
Data sources reviewed by the Agency for information on contaminant occurrence in
drinking water included: EPA's first, second, and third Unregulated Contaminant Monitoring
Rules (UCMR 1, UCMR 2, UCMR 3); Rounds 1 and 2 of the Agency's Unregulated
Contaminant Monitoring (UCM) program that preceded the Unregulated Contaminant
Monitoring Rule (UCMR); EPA's Information Collection Rule; EPA's National Inorganics and
Radionuclides Survey (NIRS); and a range of others as discussed in Chapter 2. Among the
sources reviewed, the following had data and information on metolachlor occurrence in drinking
water. These data and information are discussed in this section.
EPA's Second Unregulated Contaminant Monitoring Rule (UCMR 2).
EPA's Unregulated Contaminant Monitoring (UCM) program, Round 2.
State drinking water monitoring programs.
EPA's Community Water System Survey (CWSS).
Consumer Confidence Reports (CCRs) from PWSs.
USDA Pesticide Data Program (PDP).
• USGS Pilot Monitoring Program (PMP).
USGS source water and drinking water studies.
• National Pesticide Survey (NPS).
Additional studies from the literature.
Note that there may be some overlap, as sources with different purposes and audiences
may have reported the same underlying data. UCMR 2 and UCM Round 2 are national data
sources. Other data sources profiled in this section are considered "supplemental" sources. Also
note that the presentation of NWIS and STORET results in the ambient water section, above,
includes some finished water data and/or miscellaneous data from PWSs.
Primary Data Sources
Second Unregulated Contaminant Monitoring Rule (UCMR 2), 2008-2010
UCMR 2 monitoring was conducted from 2008 to 2010 and was designed to provide
nationally representative contaminant occurrence data. UCMR 2 required surface water systems
to monitor quarterly and groundwater systems to monitor semi-annually. There were two tiers of
monitoring: Assessment Monitoring for contaminants with commonly used analytical method
technologies and Screening Survey monitoring for contaminants that require specialized
analytical method technologies not in wide or common use at the time of the study.
All PWSs serving more than 10,000 people, plus a statistically representative national
sample of 800 PWSs serving 10,000 people or fewer, were required to conduct Assessment
Monitoring during a 12-month period between January 2008 and December 2010. For the
Screening Survey, monitoring was required by all very large PWSs, 320 representative large
PWSs, and 480 representative small PWSs, during a 12-month period between January 2008 and
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December 2010. See USEPA (2007) and USEPA (2014b) for more information on the UCMR 2
program, including study design and data analysis.
The design of UCMR 2 permits estimation of national occurrence. To calculate national
extrapolations, the percent of systems (or population served) estimated to exceed a specified
threshold in a given category can be multiplied by the total number of systems (or population
served) in the nation in that category. In the analysis of UCMR 2 Screening Survey data, the
extrapolation methodology is applied only to small and large systems, not very large systems.
Because all systems serving more than 100,000 people were required to participate in the UCMR
2 Screening Survey monitoring, national estimates of occurrence in this size category do not
require extrapolation. Rather, survey census figures are used. Total national occurrence is
estimated by summing the extrapolated or census figures from all three size categories. See
Chapter 2 for additional information on national extrapolations.
Metolachlor was monitored under the UCMR 2 Screening Survey. Monitoring results are
presented in Exhibit 8-15 through Exhibit 8-17. The minimum reporting level (MRL) was 1 (J,g/L
(72 FR 367; USEPA, 2007). A total of 11,192 finished water metolachlor samples were collected
from 1,198 systems. Of these systems, 3 (0.25 percent) had metolachlor detections and none of
the detections were greater than one-half the HRL or the HRL.
Exhibit 8-15: Metolachlor Occurrence Data from UCMR 2 Screening Survey -
Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (in |jg/L) > MRL of 1 |jg/L
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Small Systems (serving < 10,000 people)
Groundwater
ND
ND
ND
ND
ND
Surface Water
1.152
1.94
2.57
2.72
2.73235
All Small Systems
1.152
1.94
2.57
2.72
2.73235
Large Systems (serving 10,001 -100,000 people)
Groundwater
ND
ND
ND
ND
ND
Surface Water
ND
ND
ND
ND
ND
All Large Systems
ND
ND
ND
ND
ND
Very Large Systems (serving > 100,000 people) — CENSUS
Groundwater
ND
ND
ND
ND
ND
Surface Water
1.4
1.4
1.4
1.4
1.4
All Very Large
Systems
1.4
1.4
1.4
1.4
1.4
All Systems
All Water Systems
1.152
1.4
2.47
2.71
2.73235
Source: USEPA, 2012b
ND = no detections in this category
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Exhibit 8-16: Metolachlor National Occurrence Measures Based on UCMR 2
Screening Survey Data - Summary of Samples
Source Water
Type
Total
Number of
Samples
Samples with
Detections
> MRL (1 |jg/L)
Samples with Detections
> 1/2 HRL (150 |jg/L)
Samples with Detections
> HRL (300 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Small Systems (serving < 10,000 people)
Groundwater
788
0
0.00%
0
0.00%
0
0.00%
Surface Water
1,040
2
0.19%
0
0.00%
0
0.00%
All Small
Systems
1,828
2
0.11%
0
0.00%
0
0.00%
Large Systems (serving 10,001 -100,000 people)
Groundwater
1,392
0
0.00%
0
0.00%
0
0.00%
Surface Water
1,178
0
0.00%
0
0.00%
0
0.00%
All Large
Systems
2,570
0
0.00%
0
0.00%
0
0.00%
Very Large Systems (serving > 100,000 people) — CENSUS
Groundwater
2,010
0
0.00%
0
0.00%
0
0.00%
Surface Water
4,784
1
0.02%
0
0.00%
0
0.00%
All Very Large
Systems
6,794
1
0.01%
0
0.00%
0
0.00%
All Systems
All Water
Systems
11,192
3
0.03%
0
0.00%
0
0.00%
Source: USEPA, 2012b
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Exhibit 8-17: Metolachlor National Occurrence Measures Based on UCMR 2 Screening Survey Data - Summary of
System and Population Served Data - All Detections
Source
Water Type
UCMR 2 Sample
Number With At Least One
Detection > MRL (1 |jg/L)
Percent With At Least One
Detection > MRL (1 |jg/L)
National Inventory
National Estimate1
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Groundwater
240
548,364
0
0
0.00%
0.00%
57,818
37,685,557
0
0
Surface
Water
240
660,557
2
2,240
0.83%
0.34%
3,866
8,928,745
32
30,300
All Small
Systems
480
1,208,921
2
2,240
0.42%
0.19%
61,684
46,614,302
32
30,300
Large Systems (serving 10,001 -100,000 people)
Groundwater
151
6,584,184
0
0
0.00%
0.00%
1,506
38,870,272
0
0
Surface
Water
169
7,444,830
0
0
0.00%
0.00%
1,366
44,536,172
0
0
All Large
Systems
320
14,029,015
0
0
0.00%
0.00%
2,872
83,406,444
0
0
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
63
17,269,919
0
0
0.00%
0.00%
63
17,269,919
0
0
Surface
Water
335
124,711,765
1
105,270
0.30%
0.08%
335
124,711,765
1
106,000
All Very
Large
Systems
398
141,981,684
1
105,270
0.25%
0.07%
398
141,981,684
1
106,000
All Systems
All Water
Systems
1,198
157,219,620
3
107,510
0.25%
0.07%
64,954
272,002,430
33
136,000
Source: USEPA, 2012b
1 National estimates for the small and large systems are extrapolations, generated by multiplying the UCMR 2 national statistical sample findings of system/population
percentages and national system/population inventory numbers for PWSs developed from EPA's Safe Drinking Water Information System (SDWIS), the Community
Water System Survey (CWSS), and UCMR (see Chapter 2 for discussion). National estimates for the very large systems are based directly on the UCMR 2 results,
since this was a census, i.e., all very large systems were required to conduct UCMR 2 Screening Survey Monitoring. Due to rounding, some calculations may appear to
be slightly off.
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Unregulated Contaminant Monitoring (UCM) Program Round 2,1993-1997
In 1987, EPA initiated the UCM program, which collected contaminant occurrence data
from drinking water at PWSs. This program was implemented in two rounds. The first round of
UCM monitoring (UCM Round 1) generally extended from 1988 to 1992 and included
monitoring for 34 VOCs. The second round of UCM monitoring (UCM Round 2) generally
extended from 1993 to 1997 and included monitoring for 13 synthetic organic compounds
(SOCs) and sulfate in addition to the 34 volatile organic compounds (VOCs) from UCM Round
1 monitoring. All the monitored contaminants were unregulated at the time of monitoring. A
total of 38 states provided contaminant occurrence data under UCM Round 1, and 34 states
provided data under UCM Round 2. Samples were analyzed for metolachlor under UCM Round
2.
The contaminant occurrence data submitted under the UCM monitoring reflected neither
a census nor a statistically representative sample. Therefore, EPA assessed potential biases in the
data and developed a "national cross-section" separately from the UCM Round 1 and Round 2
data submitted by the states. The UCM Round 2 national cross-section of data from 20 states
consists of more than 3.7 million analytical results from approximately 27,000 systems. While
EPA recognizes that some limitations exist, the Agency believes that the national cross-sections
are indicative of national occurrence and provide a reasonable estimate of the overall distribution
and the central tendency of contaminant occurrence across the United States. For more details on
the UCM Round 1 and 2 data and the occurrence estimation methodology, refer to USEPA
(2001a), USEPA (2003), and USEPA (2008b). Note that for metolachlor, a 19-state cross-section
of states was used rather than a 20-state cross-section. Massachusetts reported UCM Round 2
sample results for SOCs, including metolachlor, from only 56 PWSs. These Massachusetts SOC
data also contained an atypically high percentage of systems with analytical detections compared
to all other states. Through communications with Massachusetts data management staff, it was
determined that the Safe Drinking Water Information System/Federal version (SDWIS/Fed)
(Round 2) Massachusetts SOC data were incomplete. Thus, Massachusetts data were omitted
from the metolachlor occurrence analyses.
Exhibit 8-18 through Exhibit 8-20 present a summary of the occurrence data from UCM
Round 2 for metolachlor. In the 19-state Round 2 cross-section, metolachlor was detected at 0.83
percent of PWSs, affecting 11.58 percent of the population served. Detected concentrations
ranged from 0.01 |ig/L to 13.8 |ig/L; none of these detections exceeded the HRL or one-half the
HRL. More detections of metolachlor were found in surface water systems than in groundwater
systems. In the 20-state Round 2 cross-section, metolachlor was detected at 0.89 percent of
PWSs, affecting 11.61 percent of the population served. Detected concentrations ranged from
0.01 |ig/L to 13.8 |ig/L; none of these detections exceeded the HRL or one-half the HRL. More
detections of metolachlor were found in surface water systems than in groundwater systems. No
detections exceeded the HRL or one-half the HRL. In Round 2, the minimum detect was 0.01
|ig/L in the all-states analysis and the cross-section states analysis. Minimum detected
concentrations are reported in Exhibit 8-18; these minimum values may be indicative of
reporting levels used.
To calculate national extrapolations, the percent of systems (or population served)
estimated to exceed a specified threshold is multiplied by the total number of systems (or
population served) in the nation. However, national extrapolations based on UCM data should be
interpreted with caution, because neither "all-states" data nor cross-section data constitute
8-29
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January 2021
statistically representative samples. See Chapter 2 for additional information on national
extrapolations. The results of national extrapolations are presented in Exhibit 8-20.
Exhibit 8-18: Metolachlor Occurrence Data from UCM Round 2 - Summary of
Detected Concentrations
Source Water Type
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
99th Percentile
Maximum
UCM Round 2 - 19-State Cross-Section (excluding MA data) - 1993-1997
Groundwater
0.12
0.70
1.36
1.97
2
Surface Water
0.01
0.59
2.69
8.33
13.8
All Systems
0.01
0.61
2.20
7.28
13.8
UCM Round 2 - 20-State Cross-Section (1993-1997)
Groundwater
0.12
0.55
1.20
1.96
2
Surface Water
0.01
0.57
2.65
8.18
13.8
All Systems
0.01
0.57
2.18
7.09
13.8
UCM Round 2 - All States (1993-1997)
Groundwater
0.1
1.00
3.00
24.11
40
Surface Water
0.01
0.87
3.00
7.06
13.8
All Systems
0.01
1.00
3.00
8.30
40
Source: USEPA, 2001b
Exhibit 8-19: Metolachlor Occurrence Data from UCM Round 2 - Summary of
Samples
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Samplt
Detection
(150
2S with
s > 1/2 HRL
M9/L)
Samplt
Detectio
(300
2S with
is > HRL
M9/L)
Number
Percent
Number
Percent
Number
Percent
UCM Round 2 - 19-State Cross-Section (excluding MA data) - 1993-1997
Groundwater
27,651
35
0.13%
0
0.00%
0
0.00%
Surface Water
6,279
160
2.55%
0
0.00%
0
0.00%
All Samples
33,930
195
0.57%
0
0.00%
0
0.00%
UCM Round 2 - 20-State Cross-Section (1993-1997)
Groundwater
27,723
46
0.17%
0
0.00%
0
0.00%
Surface Water
6,389
165
2.58%
0
0.00%
0
0.00%
All Samples
34,112
211
0.62%
0
0.00%
0
0.00%
UCM Round 2 - All States (1993-1997)
Groundwater
34,196
124
0.36%
0
0.00%
0
0.00%
Surface Water
8,598
237
2.76%
0
0.00%
0
0.00%
All Samples
42,794
361
0.84%
0
0.00%
0
0.00%
Source: USEPA, 2001b
8-30
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EPA - OGWDW
Final Regulatory Determination 4 Support Document - Ch 8, Metolachlor
January 2021
Exhibit 8-20: Metolachlor Occurrence Data from UCM Round 2 - Summary of
System and Population Served Data - All Detections
Source Water
Type
Total Number
Detections
Number
Percent
National
Extrapolation1
Systems
Populatio
n
Systems
Population
Systems
Population
Systems
Population
UCM Round 2 - 19-State Cross-Section (excluding MA data) - 1993-1997
Groundwater
11,503
14,279,627
13
99,372
0.11%
0.70%
67
686,000
Surface Water
1,450
32,818,946
95
5,353,244
6.55%
16.31%
361
27,500,000
All Systems 2
12,953
47,098,573
108
5,452,616
0.83%
11.58%
541
30,900,000
UCM Round 2 - 20-State Cross-Section (1993-1997)
Groundwater
11,530
14,387,312
17
116,597
0.15%
0.81%
88
798,000
Surface Water
1,477
33,597,041
99
5,455,297
6.70%
16.24%
369
27,400,000
All Systems 2
13,007
47,984,353
116
5,571,894
0.89%
11.61%
579
31,000,000
UCM Round 2 - All States (1993-1997)
Groundwater
13,062
15,749,200
46
172,749
0.35%
1.10%
209
1,080,000
Surface Water
1,816
43,352,288
127
8,318,145
6.99%
19.19%
385
32,400,000
All Systems 2
14,878
59,101,488
173
8,490,894
1.16%
14.37%
755
38,400,000
Source: USEPA, 2001b
1 National extrapolations are generated by multiplying the UCM findings of system/population percentages and
national system/population inventory numbers for PWSs developed from EPA's SDWIS, the CWSS, and UCMR (see
Chapter 2 for discussion). Because some water systems have more than one source water type, extrapolations are
generated separately for "Groundwater", "Surface Water", and "All Systems"; thus, the number of extrapolated
groundwater systems plus the number of extrapolated surface water systems does not add up to the extrapolated "All
Systems" numbers.
2 The number of groundwater systems plus the number of surface water systems is not equal to "All Systems"
because some water systems have more than one source water type.
Supplemental Data Sources
State Monitoring Data, 1984-2011
Because there is no available national database that receives and stores all relevant data
regarding the occurrence of regulated contaminants in public drinking water systems, EPA
conducts voluntary data requests from the states, territories, and tribes in support of national
occurrence assessments. These assessments are part of the Six-Year Review. Under the second
and third Six-Year Review (SYR2 and SYR3), a few states submitted PWS occurrence data for
unregulated contaminants along with the requested data on regulated contaminants. EPA was
able to supplement the data on unregulated contaminants by downloading additional publicly
available monitoring data from state websites. For SYR2, the result was a collection of
unregulated contaminant monitoring data from nine states and other entities, such as tribes,
territories, and EPA Regions. For SYR3, the dataset of unregulated contaminant monitoring data
included results from 14 states/entities. For both rounds of the Six-Year Review, these
unregulated data provide varying degrees of completeness in their coverage of the states/entities
and are not necessarily representative of occurrence in those states/entities. For more details on
the Six-Year Review Information Collection Request (ICR) Dataset for SYR2, refer to USEPA
8-31
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EPA - OGWDW
Final Regulatory Determination 4 Support Document - Ch 8, Metolachlor
January 2021
(2009b). For more details on the SYR3 ICR Dataset, refer to EPA's SYR3 occurrence analysis
(USEPA, 2016b).
Drinking water occurrence data for metolachlor were available from California, Florida,
Illinois, North Carolina, Ohio, Region 9 Tribes, South Dakota, Texas, and Wisconsin under
SYR2 (1999-2005). For SYR3 (2006-2011), metolachlor data were available from American
Samoa, California, Florida, Michigan, Navajo Nation, Pennsylvania, Region 1 Tribes, Region 9
Tribes, Washington, and Wisconsin.3 Results are presented in Exhibit 8-21 through Exhibit 8-23.
The exhibits do not include estimates of population served because the metolachlor data
submitted under SYR2 and SYR3 represent only a small portion of all PWSs in each state. See
USEPA (2009b) and USEPA (2016b) for the total number of systems that submitted SYR2 and
SYR3 data, respectively, from each state. Comprehensive information about methods used and
reporting levels is not available for this data set. Minimum detected concentrations are reported
in Exhibit 8-21; these minimum values may be indicative of reporting levels used.
As noted above, the monitoring data from each state/entity are limited and not necessarily
representative of occurrence in the state/entity. The number of PWSs per state with metolachlor
data ranges from only 1 PWS in the Region 1 Tribes data to 2,482 PWSs in the Michigan SYR3
data. Overall, detected concentrations ranged from 0.05 |ig/L to 14 |ig/L. Metolachlor was not
detected in any of the systems in Florida, Region 9 Tribes or South Dakota (SYR2) or in the
SYR3 data from American Samoa, Michigan, Region 1 Tribes or Washington. In the other
states/entities, the percentage of systems with detections ranged from 0.08 percent (North
Carolina SYR2) to 25 percent (Florida SYR3). No systems in any state had detections of
metolachlor greater than the HRL.
Exhibit 8-21: Metolachlor State Drinking Water Occurrence Data - Summary of
Detected Concentrations
State
Source Water
Type
(Sample Type)
Concentration Value of Detections (|jg/L)
(Date Range)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Metolachlor - Second Six-Year Review (SYR2)
Groundwater
(Raw)
0.5
0.6
0.9
1.0
1
Groundwater
(Finished)
ND
ND
ND
ND
ND
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
California
(1995-2005)
Surface Water
(Raw)
0.05
0.1
0.1
0.1
0.1
Surface Water
(Finished)
0.06
0.1
0.1
0.1
0.1
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Not Provided2
(Raw)
ND
ND
ND
ND
ND
Not Provided3
ND
ND
ND
ND
ND
Total
0.05
0.10
0.6
0.95
1
3 Some states provided more than six years' worth of data to EPA in response to the SYR2 and SYR3 ICRs.
8-32
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EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 8, Metolachlor January 2021
State
(Date Range)
Source Water
Type
(Sample Type)
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Florida
(2004-2007)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
Illinois
(1999-2005)
Groundwater
(Not Provided)1
0.25
0.25
0.25
0.25
0.25
Surface Water
(Not Provided)1
0.25
0.50
1.20
3.60
3.7
Total
0.25
0.50
1.20
3.60
3.7
North
Carolina
(1998-2005)
Groundwater
(Raw)
ND
ND
ND
ND
ND
Groundwater
(Finished)
ND
ND
ND
ND
ND
Surface Water
(Finished)
0.46
0.50
0.90
1.02
1.03
Total
0.46
0.50
0.90
1.02
1.03
Ohio
(1999-2005)
Groundwater
(Not Provided)1
0.1
0.10
0.10
0.10
0.1
Surface Water
(Not Provided)1
0.119
0.50
1.80
2.60
2.7
Total
0.1
0.50
1.80
2.60
2.7
Region 9
Tribes
(1998-2005)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
South
Dakota
(1993-2007)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
Texas
(1998-2007)
Groundwater
(Not Provided)1
0.1
0.30
0.50
0.50
0.54
Surface Water
(Not Provided)1
0.1
0.30
1.10
2.10
5.3
Not Provided3
0.21
0.21
0.21
0.21
0.21
Total
0.1
0.30
0.90
2.00
5.3
Wisconsin
(1984-1999)
Groundwater
(Not Provided)1
0.1
0.50
3.20
12.2
14
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
0.1
0.50
3.20
12.2
14
Wisconsin
(2000-2009)
Groundwater
(Not Provided)1
0.1
0.30
1.90
2.40
2.5
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
0.1
0.30
1.90
2.40
2.5
Metolachlor - Third Six-Year Review (SYR3)
American
Samoa
(2006-2011)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
N/A
N/A
N/A
N/A
N/A
Total
ND
ND
ND
ND
ND
8-33
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EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 8, Metolachlor January 2021
State
(Date Range)
Source Water
Type
(Sample Type)
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
99th Percentile
Maximum
California
(2006-2011)0
Groundwater
(Raw)
ND
ND
ND
ND
ND
Groundwater
(Finished)
ND
ND
ND
ND
ND
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Raw)
0.07
0.20
0.20
0.24
0.25
Surface Water
(Finished)
0.06
0.10
0.20
0.20
0.20
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
0.06
0.19
0.20
0.24
0.25
Florida
(2006-2010)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
0.068
0.068
0.068
0.068
0.068
Total
0.068
0.068
0.068
0.068
0.068
Michigan
(2006-2011)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Not Provided3
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
Navajo
Nation
(2006-2011)
Groundwater
(Not Provided)1
0.1
0.1
0.1
0.1
0.1
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
0.1
0.1
0.1
0.1
0.1
Pennsylvania
(2006-2011)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
0.31
0.31
0.31
0.31
0.31
Total
0.31
0.31
0.31
0.31
0.31
Region 1
Tribes
(2007)
Groundwater
(Not Provided)1
N/A
N/A
N/A
N/A
N/A
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
8-34
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Final Regulatory Determination 4 Support Document - Ch 8, Metolachlor
January 2021
State
Source Water
Type
(Sample Type)
Concentration Value of Detections (|jg/L)
(Date Range)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Region 9
Tribes
(2006-2011)
Groundwater
(Not Provided)1
0.1
0.1
0.1
0.1
0.1
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
0.1
0.1
0.1
0.1
0.1
Groundwater
(Raw)
ND
ND
ND
ND
ND
Groundwater
(Finished)
ND
ND
ND
ND
ND
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Washington
(2006-2011)
Surface Water
(Raw)
ND
ND
ND
ND
ND
Surface Water
(Finished)
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Not Provided2
(Raw)
ND
ND
ND
ND
ND
Not Provided3
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
Groundwater
(Not Provided)1
0.1
0.12
0.34
0.38
0.39
Wisconsin
(2006-2011)
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Not Provided3
ND
ND
ND
ND
ND
Total
0.1
0.12
0.34
0.38
0.39
Source: Data provided to EPA by states and downloaded by EPA from state websites
ND = no detections in this category
N/A = not applicable (no data in this category)
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from groundwater or surface water.
3 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
8-35
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Final Regulatory Determination 4 Support Document - Ch 8, Metolachlor
January 2021
Exhibit 8-22: Metolachlor State Drinking Water Occurrence Data - Summary of
Samples
State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Samples
All Detections
Samplt
Detec
> 1/2 HRL
2S with
:tions
150 ug/L)
Samples with
Detections > HRL
(300 ug/L)
Number
Percent
Number
Percent
Number | Percent
Metolachlor - Second Six-Year Review (SYR2)
California
(1995-2005)
Groundwater
(Raw)
13,056
4
0.03%
0
0.00%
0
0.00%
Groundwater
(Finished)
205
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
57
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
7,205
11
0.15%
0
0.00%
0
0.00%
Surface Water
(Finished)
896
3
0.33%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
18
0
0.00%
0
0.00%
0
0.00%
Not Provided2
(Raw)
6
0
0.00%
0
0.00%
0
0.00%
Not Provided3
2
0
0.00%
0
0.00%
0
0.00%
Total
21,445
18
0.08%
0
0.00%
0
0.00%
Florida
(2004-2007)
Groundwater
(Not Provided)1
17
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
11
0
0.00%
0
0.00%
0
0.00%
Total
28
0
0.00%
0
0.00%
0
0.00%
Illinois
(1999-2005)
Groundwater
(Not Provided)1
2,531
1
0.04%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
718
33
4.60%
0
0.00%
0
0.00%
Total
3,249
34
1.05%
0
0.00%
0
0.00%
North
Carolina
(1998-2005)
Groundwater
(Raw)
122
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Finished)
12,117
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Finished)
1,537
4
0.26%
0
0.00%
0
0.00%
Total
13,776
4
0.03%
0
0.00%
0
0.00%
Ohio
(1999-2005)
Groundwater
(Not Provided)1
1,017
1
0.10%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
942
22
2.34%
0
0.00%
0
0.00%
Total
1,959
23
1.17%
0
0.00%
0
0.00%
Region 9
Tribes
(1998-2005)
Groundwater
(Not Provided)1
700
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
34
0
0.00%
0
0.00%
0
0.00%
Total
734
0
0.00%
0
0.00%
0
0.00%
South Dakota
(1993-2007)
Groundwater
(Not Provided)1
1,520
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
264
0
0.00%
0
0.00%
0
0.00%
Total
1,784
0
0.00%
0
0.00%
0
0.00%
8-36
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EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 8, Metolachlor January 2021
State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Samples
All Detections
Samplt
Detec
> 1/2 HRL
2S with
:tions
150 ug/L)
Samples with
Detections > HRL
(300 ug/L)
Number
Percent
Number
Percent
Number
Percent
Texas
(1998-2007)
Groundwater
(Not Provided)1
5,537
9
0.16%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
6,093
101
1.66%
0
0.00%
0
0.00%
Not Provided3
183
1
0.55%
0
0.00%
0
0.00%
Total
11,813
111
0.94%
0
0.00%
0
0.00%
Wisconsin
(1984-1999)
Groundwater
(Not Provided)1
2,460
18
0.73%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
108
0
0.00%
0
0.00%
0
0.00%
Total
2,568
18
0.70%
0
0.00%
0
0.00%
Wisconsin
(2000-2009)
Groundwater
(Not Provided)1
1,525
25
1.64%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
15
0
0.00%
0
0.00%
0
0.00%
Total
1,540
25
1.62%
0
0.00%
0
0.00%
Metolachlor - Third Six-Year Review (SYR3)
American
Samoa
(2006-2011)
Groundwater
(Not Provided)1
46
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Total
46
0
0.00%
0
0.00%
0
0.00%
California
(2006-2011)
Groundwater
(Raw)
6,048
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Finished)
269
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
77
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
2,910
12
0.41%
0
0.00%
0
0.00%
Surface Water
(Finished)
395
2
0.51%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
30
0
0.00%
0
0.00%
0
0.00%
Total
9,729
14
0.14%
0
0.00%
0
0.00%
Florida
(2006-2010)
Groundwater
(Not Provided)1
3
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
19
1
5.26%
0
0.00%
0
0.00%
Total
22
1
4.55%
0
0.00%
0
0.00%
Michigan
(2006-2011)
Groundwater
(Not Provided)1
4,562
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
256
0
0.00%
0
0.00%
0
0.00%
Not Provided3
25
0
0.00%
0
0.00%
0
0.00%
Total
4,843
0
0.00%
0
0.00%
0
0.00%
Navajo Nation
(2006-2011)
Groundwater
(Not Provided)1
63
1
1.59%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
2
0
0.00%
0
0.00%
0
0.00%
Total
65
1
1.54%
0
0.00%
0
0.00%
8-37
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EPA - OGWDW
Final Regulatory Determination 4 Support Document - Ch 8, Metolachlor
January 2021
State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Samples
All Detections
Sampk
Detec
> 1/2 HRL
ss with
tions
150 ug/L)
Samples with
Detections > HRL
(300 ug/L)
Number
Percent
Number
Percent
Number
Percent
Pennsylvania
(2006-2011)
Groundwater
(Not Provided)1
545
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
130
1
0.77%
0
0.00%
0
0.00%
Total
675
1
0.15%
0
0.00%
0
0.00%
Region 1
Tribes
(2007)
Groundwater
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
1
0
0.00%
0
0.00%
0
0.00%
Total
1
0
0.00%
0
0.00%
0
0.00%
Region 9
Tribes
(2006-2011)
Groundwater
(Not Provided)1
231
1
0.43%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
15
0
0.00%
0
0.00%
0
0.00%
Total
246
1
0.41%
0
0.00%
0
0.00%
Washington
(2006-2011)
Groundwater
(Raw)
1,713
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Finished)
1,208
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
689
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
151
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Finished)
214
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
45
0
0.00%
0
0.00%
0
0.00%
Not Provided2
(Raw)
14
0
0.00%
0
0.00%
0
0.00%
Not Provided3
7
0
0.00%
0
0.00%
0
0.00%
Total
4,041
0
0.00%
0
0.00%
0
0.00%
Wisconsin
(2006-2011)
Groundwater
(Not Provided)1
649
7
1.08%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
157
0
0.00%
0
0.00%
0
0.00%
Not Provided3
7
0
0.00%
0
0.00%
0
0.00%
Total
813
7
0.86%
0
0.00%
0
0.00%
Source: Data provided to EPA by states and downloaded by EPA from state websites
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from groundwater or surface water.
3 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
8-38
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EPA - OGWDW
Final Regulatory Determination 4 Support Document - Ch 8, Metolachlor
January 2021
Exhibit 8-23: Metolachlor State Drinking Water Occurrence Data - Summary of
Systems
State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > Vi HRL
(150 |jg/L)
Systems with
Detections > HRL
(300 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Metolachlor - Second Six-Year Review (SYR2
California
(1995-2005)
Groundwater
(Raw)
1,635
3
0.18%
0
0.00%
0
0.00%
Groundwater
(Finished)
75
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
30
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
322
11
3.42%
0
0.00%
0
0.00%
Surface Water
(Finished)
118
3
2.54%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
9
0
0.00%
0
0.00%
0
0.00%
Not Provided2
(Raw)
5
0
0.00%
0
0.00%
0
0.00%
Not Provided3
1
0
0.00%
0
0.00%
0
0.00%
Total
2,002
15
0.69%
0
0.00%
0
0.00%
Florida
(2004-2007)
Groundwater
(Not Provided)1
5
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
1
0
0.00%
0
0.00%
0
0.00%
Total
6
0
0.00%
0
0.00%
0
0.00%
Illinois
(1999-2005)
Groundwater
(Not Provided)1
775
1
0.13%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
100
16
16.00%
0
0.00%
0
0.00%
Total
875
17
1.94%
0
0.00%
0
0.00%
North Carolina
(1998-2005)
Groundwater
(Raw)
99
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Finished)
2,282
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Finished)
192
2
1.04%
0
0.00%
0
0.00%
Total
2,477
2
0.08%
0
0.00%
0
0.00%
Ohio
(1999-2005)
Groundwater
(Not Provided)1
680
1
0.15%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
141
5
3.55%
0
0.00%
0
0.00%
Total
821
6
0.73%
0
0.00%
0
0.00%
Region 9
Tribes
(1998-2005)
Groundwater
(Not Provided)1
212
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
13
0
0.00%
0
0.00%
0
0.00%
Total
225
0
0.00%
0
0.00%
0
0.00%
South Dakota
(1993-2007)
Groundwater
(Not Provided)1
234
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
21
0
0.00%
0
0.00%
0
0.00%
Total
255
0
0.00%
0
0.00%
0
0.00%
8-39
-------
EPA - OGWDW Final Regulatory Determination 4 Support Document - Ch 8, Metolachlor January 2021
State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > Vi HRL
(150 |jg/L)
Systems with
Detections > HRL
(300 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Texas
(1998-2007)
Groundwater
(Not Provided)1
1,801
5
0.28%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
392
34
8.67%
0
0.00%
0
0.00%
Not Provided3
59
1
1.69%
0
0.00%
0
0.00%
Total
2,252
40
1.78%
0
0.00%
0
0.00%
Wisconsin
(1984-1999)
Groundwater
(Not Provided)1
1,154
9
0.78%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
21
0
0.00%
0
0.00%
0
0.00%
Total
1,175
9
0.77%
0
0.00%
0
0.00%
Wisconsin
(2000-2009)
Groundwater
(Not Provided)1
891
7
0.79%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
24
0
0.00%
0
0.00%
0
0.00%
Total
915
7
0.77%
0
0.00%
0
0.00%
Metolachlor - Third Six-Year Review (SYR3)
American
Samoa
(2006-2011)
Groundwater
(Not Provided)1
11
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Total
11
0
0.00%
0
0.00%
0
0.00%
California
(2006-2011)
Groundwater
(Raw)
1,299
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Finished)
41
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
31
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
285
10
3.51%
0
0.00%
0
0.00%
Surface Water
(Finished)
77
2
2.60%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
14
0
0.00%
0
0.00%
0
0.00%
Total
1,613
10
0.62%
0
0.00%
0
0.00%
Florida
(2006-2010)
Groundwater
(Not Provided)1
3
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
1
1
100%
0
0.00%
0
0.00%
Total
4
1
25.00%
0
0.00%
0
0.00%
Michigan
(2006-2011)
Groundwater
(Not Provided)1
2,400
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
60
0
0.00%
0
0.00%
0
0.00%
Not Provided3
22
0
0.00%
0
0.00%
0
0.00%
Total
2,482
0
0.00%
0
0.00%
0
0.00%
8-40
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EPA - OGWDW
Final Regulatory Determination 4 Support Document - Ch 8, Metolachlor
January 2021
State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > Vi HRL
(150 |jg/L)
Systems with
Detections > HRL
(300 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Navajo Nation
(2006-2011)
Groundwater
(Not Provided)1
37
1
2.70%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
1
0
0.00%
0
0.00%
0
0.00%
Total
38
1
2.63%
0
0.00%
0
0.00%
Pennsylvania
(2006-2011)
Groundwater
(Not Provided)1
141
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
37
1
2.70%
0
0.00%
0
0.00%
Total
178
1
0.56%
0
0.00%
0
0.00%
Region 1
Tribes
(2007)
Groundwater
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
1
0
0.00%
0
0.00%
0
0.00%
Total
1
0
0.00%
0
0.00%
0
0.00%
Region 9
Tribes
(2006-2011)
Groundwater
(Not Provided)1
127
1
0.79%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
10
0
0.00%
0
0.00%
0
0.00%
Total
137
1
0.73%
0
0.00%
0
0.00%
Washington
(2006-2011)
Groundwater
(Raw)
955
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Finished)
738
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
461
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
50
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Finished)
87
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
21
0
0.00%
0
0.00%
0
0.00%
Not Provided2
(Raw)
7
0
0.00%
0
0.00%
0
0.00%
Not Provided3
5
0
0.00%
0
0.00%
0
0.00%
Total
2,077
0
0.00%
0
0.00%
0
0.00%
Wisconsin
(2006-2011)
Groundwater
(Not Provided)1
295
5
1.69%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
28
0
0.00%
0
0.00%
0
0.00%
Not Provided3
6
0
0.00%
0
0.00%
0
0.00%
Total
329
5
1.52%
0
0.00%
0
0.00%
Source: Data provided to EPA by states and downloaded by EPA from state websites
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from groundwater or surface water.
3 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
8-41
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Final Regulatory Determination 4 Support Document - Ch 8, Metolachlor
January 2021
Community Water System Survey (CWSS), 2000 and 2006
The 2000 CWSS (USEPA, 2002b; USEPA, 2002c) gathered data on the financial and
operating characteristics of a random sample of CWSs nationwide. In addition, the Survey asked
all community water systems (CWSs) serving more than 500,000 people (a total of 83 systems)
to provide monitoring results for five regulated compounds (arsenic, atrazine, 2,4-D, simazine,
and glyphosate) and four unregulated compounds (radon, methyl tert-butyl ether or MTBE,
metolachlor, and boron), including results from raw water at each intake and from finished water
at each treatment plant. EPA received responses from 58 systems, although not all of these
systems answered every question.
Results of raw water monitoring are aggregated by type of intake. In raw groundwater,
four wells reported detections of metolachlor. The median concentration at the wells reporting
detections was 1 |ig/L and the 90th percentile concentration was 210 |ig/L. Non-detections were
reported at 44.9 percent of groundwater intakes. In raw surface water, 12 surface water intakes
reported detections of metolachlor. Among detects, the median concentration was 1 |ig/L and the
90th percentile concentration was 5 |ig/L. Non-detections were reported at 36.7 percent of surface
water intakes (USEPA, 2002c).
Results of finished water monitoring are aggregated by system type. At systems primarily
served by groundwater, two wells reported metolachlor detections. The median concentration at
the wells reporting detections was 205 |ig/L and the 90th percentile concentration was 210 |ig/L.
Non-detections were reported at 9.1 percent of groundwater wells. Twenty surface water intakes
reported detections of metolachlor. The median concentration at surface water intakes reporting
detections was 0 |ig/L and the 90th percentile concentration was 4 |ig/L. Non-detections were
reported at 49.5 percent of surface water intakes. No systems primarily served by purchased
water reported any detections of metolachlor (USEPA, 2002c).
The 2006 CWSS (USEPA, 2009c; USEPA, 2009d) gathered data on the financial and
operating characteristics of a random sample of CWSs nationwide. All systems serving more
than 500,000 people (94 systems in 2006) received the survey, and systems in that size category
were asked questions about concentrations of unregulated contaminants in their raw and finished
water. Of the 94 systems asked about unregulated contaminants, 58 systems (62 percent)
responded to the survey, though not all of these systems answered every question. EPA
supplemented the data set by gathering additional information about contaminant occurrence at
the 94 systems from publicly available sources (e.g., CCRs).
In the 2006 CWSS, three of the 94 systems serving more than 500,000 people reported
monitoring data for metolachlor. These three systems reported results from a total of seven
samples. Metolachlor was detected in two of the seven samples, or approximately 29 percent of
the samples. The 90th percentile of detected concentrations was equal to 1.4 |ig/L which is less
than one-half the HRL and the HRL.
Reporting levels were not specified in either the 2000 or the 2006 survey. The minimum
detected concentration may be indicative of reporting levels used.
Water Systems' Consumer Confidence Reports (CCRs), 2010-2018
CCRs are annual water quality reports that CWSs are required to provide to their
customers. These reports summarize information on water sources, detected contaminants, and
system compliance with EPA drinking water standards; they may also include general
educational material. Under the CCR Rule (40 CFR Subpart O), CWSs with 15 or more
connections or serving at least 25 year-round residents must prepare and distribute a CCR to all
8-42
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Final Regulatory Determination 4 Support Document - Ch 8, Metolachlor
January 2021
billing units or service connections every year. Systems serving 100,000 or more residents are
also required to post their current CCRs on a publicly accessible Internet site. EPA reviewed
CCRs published by the 22 systems that serve over 1 million customers (as identified in the
UCMR 3 database) for unregulated contaminant occurrence information for the years 2010
through 2018. Data on metolachlor were available from CCRs prepared by five CWSs: one
system in Maryland (Washington Suburban Sanitary Commission), two systems in New York
(Suffolk County and New York City), one system in Ohio (City of Columbus), and one system in
Pennsylvania (City of Philadelphia).
Washington Suburban Sanitary Commission included data on metolachlor in its 2012
CCR. Samples were collected from two surface water sources, the Potomac and Patuxent Rivers.
The number of samples collected was not reported. At the Patuxent site, metolachlor was not
detected. At the Potomac site, concentrations ranged from not detected to <1 |ig/L.
Suffolk County, New York included data on metolachlor in its 2012 through 2018 CCRs.
Suffolk County is served by groundwater from four major aquifers beneath Long Island. Each of
the seven CCRs reported results from the previous year (e.g., the 2012 CCR reported results for
the year 2011).
• The 2012 CCR reported that in 2011 the Rocky Point Rd. #4 well in East Marion was
placed on filtration to remove metolachlor. The 2012 CCR reported that 286 water
samples were collected for metolachlor from Distribution Area 1; metolachlor was
not detected in any sample.
• The 2013 CCR presented results for 26 distribution areas. The number of samples
varied from 4 to 280 depending on the distribution area. Metolachlor concentrations
ranged from non-detected to 0.8 |ig/L.
• The 2014 CCR presented results for 26 distribution areas. The number of metolachlor
samples varied from 4 to 271 depending on the distribution area; metolachlor
concentrations ranged from non-detected to 1.1 |ig/L.
• The 2015 CCR presented results for 27 distribution areas. The number of metolachlor
samples varied from 4 to 269 depending on the distribution area; metolachlor
concentrations ranged from non-detected to 0.3 |ig/L.
• The 2016 CCR presented results for 27 distribution areas. The number of metolachlor
samples varied from 4 to 278 depending on the distribution area; metolachlor
concentrations ranged from non-detected to 0.3 |ig/L.
• The 2017 CCR presented results for 27 distribution areas. The number of metolachlor
samples varied from 4 to 280 depending on the distribution area; metolachlor
concentrations ranged from non-detected to 0.4 |ig/L.
• The 2018 CCR presented results for 27 distribution areas. The number of metolachlor
samples varied from 4 to 272 depending on the distribution area; metolachlor
concentrations ranged from non-detected to 0.23 |ig/L.
New York City included data on metolachlor in eight CCRs covering 2010 through 2017.
New York City is served by a large system of surface water networks in New York State. In all
eight years, metolachlor was monitored for but was not detected. The number of samples
collected was not reported in any years.
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The City of Columbus, Ohio included data on metolachlor in its CCRs for 2010 through
2017. The City of Columbus water system uses surface water from the Scioto River and Big
Walnut Creek, as well as groundwater sources. Data from 2010 were reported for two locations;
the number of samples collected was not reported. Metolachlor concentrations ranged from non-
detected to 0.28 |ig/L. In 2011, data were reported for two locations; the number of samples
collected was not reported. Metolachlor was not detected at either location. In the CCRs from
2012 through 2017, metolachlor data were reported for three locations; the number of samples
collected was not reported in any year. In 2012, metolachlor concentrations ranged from non-
detected to 0.24 |ig/L. In 2013, metolachlor concentrations ranged from non-detected to 0.25
|ig/L. The 2014 and 2015 CCRs both reported metolachlor concentrations ranging from non-
detected to 0.72 |ig/L. The 2016 and 2017 CCRs both reported metolachlor concentrations
ranging from non-detected to 0.33 |ig/L.
The City of Philadelphia, Pennsylvania included data on metolachlor in its 2010 CCR.
(Monitoring was conducted as part of the UCMR 2 program.) Philadelphia is served by two
surface water sources, the Schuylkill and the Delaware Rivers. In 2010, metolachlor was not
detected during the testing. The number of samples collected was not reported. Sampling
locations were also not reported.
United States Department of Agriculture (USDA) Pesticide Data Program (PDP), 2001-2013
The USDA PDP maintains a national pesticide residue database. PDP was initiated in
1991 to collect data on pesticide residues in food with sampling conducted on a statistically
defensible representation of pesticide residuals in the United States food supply (USDA, 2018a).
Sampling and testing are conducted on fruits and vegetables, select grains, milk, and (as of 2001)
drinking water.
The PDP drinking water project was initiated at CWSs in New York and California in
2001. Since then, the drinking water sampling program has expanded, though a somewhat
changing mix of states is sampled each year. At one time or another, CWSs in more than 29
states have contributed raw and/or finished water data to the program (USDA, 2018a). The
CWSs selected for sampling tend to be small and medium-sized systems (primarily CWSs
serving under 50,000), systems served by surface water, and systems located in regions of heavy
agriculture. Sampling of untreated water in addition to treated water began in 2004; sampling
continued until 2013 (USDA, 2018a). Note that temporal trends cannot be evaluated based on
these data since, with the exception of 2002 and 2003, samples were not collected from the same
sites and states in consecutive years.
Metolachlor was included in the USDA PDP (see Exhibit 8-24; USDA, 2018b). Limits of
detection for metolachlor ranged from 0.0015 to 0.045 |ig/L. Metolachlor was detected in 3,323
(46.40 percent) of 7,161 total samples collected between 2001 and 2013. Within that set,
metolachlor was detected in 1,900 (43.6 percent) of 4,355 finished samples collected. The
maximum detection concentrations in finished water and raw water were equal to 2.031 ng/L and
2 ng/L, respectively; thus, none of the detected concentrations of metolachlor exceeded one-half
the metolachlor HRL or the metolachlor HRL.
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Exhibit 8-24: Summary of Metolachlor PDP Data, 2001-2013
Year
Finished/
Raw
Total Number
of Samples
Number of
Detections
Percent of
Detections
Minimum
Value of
Detections
(M9/L)
Maximum Value of
Detections (|jg/L)
Metolachlor
2001
Finished
203
102
50.25%
0.010
0.079
2002
Finished
582
233
40.03%
0.005
0.226
2003
Finished
782
322
41.18%
0.005
0.276
2004
Finished
381
153
40.16%
0.0025
0.661
Raw
381
179
46.98%
0.0025
0.729
2005
Finished
374
161
43.05%
0.0025
0.290
Raw
376
184
48.94%
0.0025
0.430
2006
Finished
363
113
31.13%
0.0025
0.463
Raw
364
136
37.36%
0.0025
0.522
2007
Finished
369
85
23.04%
0.0025
1.056
Raw
364
102
28.02%
0.0025
2.000
2008
Finished
310
127
40.97%
0.0025
2.031
Raw
309
161
52.10%
0.0025
0.990
2009
Finished
306
175
57.19%
0.0025
0.295
Raw
306
200
65.36%
0.0025
0.603
2010
Finished
284
168
59.15%
0.0025
0.899
Raw
283
171
60.42%
0.0025
1.437
2011
Finished
119
66
55.46%
0.004995
0.588
Raw
120
73
60.83%
0.004995
0.464
2012
Finished
232
165
71.12%
0.0025
0.21
Raw
253
187
73.91%
0.0025
1.5
2013
Finished
50
30
60.00%
0.0025
0.073
Raw
50
30
60.00%
0.0025
0.17
Source: USDA, 2018b
USEPA / United States Geological Survey (USGS) Nationwide Reconnaissance of
Contaminants of Emerging Concern
As part of a joint study by EPA and the USGS to assess human exposure to contaminants
of emerging concern, water samples were collected from 25 drinking water treatment plants
(DWTPs) in 24 states (Glassmeyer et al., 2017). Participation in the study was voluntary. Final
sample locations were chosen to represent a wide range of geography, diversity in disinfectant
type used, and a range of production volumes. Phase I of the study (2007) analyzed a subset of
contaminants and sites to test experimental design; metolachlor was not included in Phase 1.
During Phase II of the study (2010-2012), samples were collected from groundwater and surface
water sources and treated drinking water from 25 drinking water treatment plants and analyzed
for metolachlor occurrence. The Lowest Concentration Minimum Reporting Level (LCMRL)
was 0.049 (J,g/L.
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Results from Phase II are presented in Exhibit 8-25. Of the 25 source water samples, 12
percent exceeded the LCMRL. Similarly, 12 percent of treated water samples exceeded the
LCMRL. The maximum detected concentration in source water was 0.130 (J,g/L. The maximum
detected concentration in treated water was 0.100 (J,g/L. No detected concentrations exceeded
one-half the HRL or the HRL.
Exhibit 8-25: Drinking Water Treatment Plants - Summary of Metolachlor Samples
(Glassmeyer et al., 2017)
Source Water Type
Number of
Samples
All Detections
Median
Concentration
(ng/L)
Maximum
Concentration
(ng/L)
Number
Percent
Source Water
25
3
12.00%
0.130
0.130
Treated Drinking Water
25
3
12.00%
0.095
0.100
Source: Glassmeyer et al., 2017
United States Geological Survey (USGS) Pilot Monitoring Program (PMP), 1999
In 1999, a PMP was initiated by the USGS and EPA to provide information on pesticide
concentrations in drinking water. This study focused on small drinking water supply reservoirs in
areas with high pesticide use in order to test the sampling approach in areas where pesticides are
probably present (Blomquist et al., 2001). Sampling sites represent a variety of geographic
regions as well as different cropping patterns. The ideal site candidates were mostly small
reservoirs located in high pesticide-use areas with a high runoff potential. Twelve water-supply
reservoirs, considered vulnerable to pesticide contamination, were selected from the list of
candidates. These 12 sites were located in California, Indiana, Louisiana, Missouri, New York,
North Carolina, Ohio, Oklahoma, Pennsylvania, South Carolina, South Dakota, and Texas.
Samples were collected quarterly throughout the year and at weekly or biweekly intervals
following the primary pesticide-application periods. Water samples were collected from the raw-
water intake and from finished drinking water taps prior to entering the distribution system. At
some sites, samples were also collected at the reservoir outflow.
Metolachlor was an analyte in the PMP. At a method reporting level of 0.002 |ig/L,
metolachlor was detected in 288 (89.2 percent) of the 323 samples from raw water sites, with a
maximum concentration of 3.320 |ig/L and a 95th percentile concentration of 0.033 |ig/L.
Metolachlor was detected in 198 (86.8 percent) of the 228 samples from finished water sites,
with a maximum concentration of 0.661 |ig/L and a 95th percentile concentration of 0.336 |ig/L
(Blomquist et al., 2001). No detected concentrations exceeded one-half the HRL or the HRL.
United States Geological Survey (USGS) National Water Quality Assessment (NAWQA)
Source Water and Drinking Water Studies
Note that there may be some overlap between the NAWQA data assessment presented
earlier in the ambient water occurrence section and the summaries of NAWQA studies presented
below. The studies presented below include occurrence data from water sources for PWSs.
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Organic Compounds in Source Water of Selected Community Water Systems (Hopple
et al., 2009 and Kingsbury et al., 2008), 2002-2005
As part of the NAWQA program, Hopple et al. (2009) and Kingsbury et al. (2008)
conducted studies to characterize anthropogenic organic compounds in waters of the United
States used as source waters for PWSs. Hopple et al. (2009) focused on groundwater and
Kingsbury et al. (2008) focused on surface water. In Phase 1 of the studies (Exhibit 8-26),
geographically diverse source water samples were collected between October 2002 and July
2005 from nine CWSs served by streams and from 221 CWS wells that withdraw from 12
aquifers. In Phase 2 of the studies (Exhibit 8-27), USGS collected source and finished water
samples at a subset of sites between June 2004 and September 2005. The reporting level for
metolachlor (0.006 (J,g/L) was the same for both phases and for ground and surface water
samples.
In Phase 1, metolachlor was detected in 10.9 percent of the 221 groundwater samples,
with a maximum detected concentration of 3.58 |ig/L. Metolachlor was detected in 51.4 percent
of 146 surface water samples, with a maximum concentration of 2.93 |ig/L. In Phase 2, a total of
64 raw groundwater and 65 finished groundwater samples were analyzed for metolachlor; it was
detected in 13 percent and 11 percent of raw and finished groundwater samples, respectively. A
total of 90 raw surface water and 87 finished surface water samples were analyzed for
metolachlor; it was detected in 59 percent of the raw surface water samples and in 54 percent of
the finished surface water samples (Hopple et al., 2009; Kingsbury et al., 2008). No detected
concentrations in Phase 1 or Phase 2 exceeded one-half the HRL or the HRL.
Exhibit 8-26: Metolachlor Data from Source Water (Hopple et al., 2009 and
Kingsbury et al., 2008) - Summary of Detections from Phase 1
Source Water Type
Number of
Samples
Percent of Detections
Maximum
Concentration
(ng/L)
All
> 0.1 |jg/L
Groundwater
221
10.9%
0.9%
3.58
Surface Water
146
51.4%
8.8%
2.93
Source: Hopple et al., 2009 and Kingsbury et al., 2008
Exhibit 8-27: Metolachlor Data from Source Water - Summary of Detections from
Phase 2 - Groundwater (Hopple et al., 2009) and Surface Water (Kingsbury et al.,
2008)
Source Water
Type
Number of Samples
Percent of Detections
Maximum Concentration
(ng/L)
Raw Water
Finished Water
Raw
Water
Finished Water
Raw Water
Finished Water
Groundwater
64
65
13%
11%
0.04
0.021
Surface Water
90
87
59%
54%
0.80
0.47
Source: Hopple et al., 2009 and Kingsbury et al., 2008
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Water Quality in Public-Supply Wells (Toccalino et al., 2010), 1993-2007
To assess risks posed by contaminants in public-supply wells, water samples were
collected from source (untreated) groundwater from 932 public-supply wells located in parts of
40 NAWQA Study Units in 41 states (Toccalino et al., 2010). Each well was sampled once
between 1993 and 2007. The public wells sampled in this study represented 629 unique PWSs,
representing 0.5 percent of the approximately 140,000 groundwater-supplied PWSs, but nearly
25 percent of the population served by groundwater-PWSs in the United States. Of a total of 870
metolachlor samples, the maximum detected concentration was equal to 3.58 ng/L. Metolachlor
was detected in 8.62 percent of samples; no detections were greater than one-half the HRL or the
HRL. Reporting levels used for metolachlor in this study ranged from 0.002 |ig/L to 0.006 |ig/L.
Results from this study are presented in Exhibit 8-28 and Exhibit 8-29.
Exhibit 8-28: Metolachlor Data from Public-Supply Wells (Toccalino et al., 2010) -
Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Groundwater Only
0.000673
0.006
0.08
2.10
3.58
Source: Toccalino et al., 2010
Exhibit 8-29: Metolachlor Data from Public-Supply Wells (Toccalino et al., 2010) -
Summary of Samples
Source Water
Type
Total
Number of
Samples
All Detections
Detections > Vi HRL
(150 |jg/L)
Detections > HRL
(300 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Groundwater
Only
870
75
8.62%
0
0.00%
0
0.00%
Source: Toccalino et al., 2010
Water Quality in Domestic Wells (DeSimone, 2009), 1991-2004
Between 1991 and 2004, USGS conducted an assessment of water quality from domestic
wells across the United States using NAWQA data (DeSimone, 2009). The program included the
analysis of major ions, trace elements, nutrients, radon, and organic compounds (pesticides and
VOCs) at approximately 2,100 domestic wells (private drinking water wells) across 48 states,
covering 30 regional aquifers. In addition, USGS summarized data from wells sampled for
NAWQA agricultural land-use assessment studies to provide an indication of the potential
effects of agricultural land-use practices on the groundwater in the aquifers studied. Reporting
thresholds varied; thresholds of both 0.002 [j,g/L and 0.006 [j,g/L are listed. Metolachlor was
detected in 174 (6.85 percent) of the 2,540 samples from aquifer and agricultural land-use
studies. Concentrations of metolachlor in these samples did not exceed 3 [j,g/L and were,
therefore, less than one-half the HRL and the HRL (DeSimone, 2009).
Water Quality in Principal Aquifers of the United States (DeSimone et al., 2014), 1991-
2010
Another USGS report based on NAWQA Program ambient groundwater sampling
presents summaries of pesticide and other constituent occurrence, including those for
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metolachlor in principal aquifers (DeSimone et al., 2014). Samples were collected between 1990
and 2010 across the US from more than 60 principal aquifers that supply most of the
groundwater pumped across the Nation for drinking water, irrigation, and other uses. At
concentrations above 0.1 |ig/L, detection frequencies for metolachlor were equal to 0.42 percent
in parts of aquifers used for drinking water, 2.51 percent in shallow groundwater beneath
agricultural land, and 0.35 percent in shallow groundwater beneath urban land. Typical
laboratory reporting levels ranged from 0.002 to 0.014 |ig/L.
Water Quality in Carbonate Aquifers (Lindsey et al, 2008), 1993-2005
As part of the NAWQA program, Lindsey et al. (2008) conducted an assessment of the
water quality in carbonate aquifers, which account for 22 percent of the groundwater pumped by
the country's PWSs. From 1993 to 2005, the study analyzed 1,042 wells and springs across 12
aquifer systems and 20 states for major ions, radon, nutrients, pesticides, and VOCs. Metolachlor
was detected in 153 (14.9 percent) of 1,027 samples. Reporting levels varied; the maximum (LT-
MDL) for metolachlor was given as 0.006 [j,g/L and the maximum common laboratory reporting
limit was 0.013 (J,g/L. No metolachlor detections exceeded 700 ng/L, the health-based screening
level used in the study.
National Pesticide Survey (NPS), 1988-1990
In 1990, EPA completed a national survey of pesticides in drinking water wells. The
purpose of the NPS was to determine the national occurrence frequencies and concentrations of
select pesticides in the nation's drinking water wells, and to improve EPA's understanding of
how pesticide occurrence in groundwater correlates with patterns of pesticide usage and
groundwater vulnerability. The survey included 566 CWS wells and 783 rural domestic wells.
Sampling was conducted between 1988 and 1990. The survey targeted areas representing a
variety of pesticide usage levels and groundwater vulnerability. The survey was designed to
provide a statistically reliable estimate of pesticide occurrence in the nation's drinking water
wells. It was not designed to provide statistically valid results at the state or local level. Wells
were sampled for 101 pesticides, 25 pesticide degradates, and nitrate (USEPA, 1990b). At a
reporting level of 0.75 |ig/L, metolachlor was not detected in the survey (USEPA, 1990b).
Additional Source Water and Drinking Water Studies
In a study by the Wisconsin Department of Agriculture, Trade and Consumer Protection
(WIDATCP), Wisconsin groundwater was sampled from October 1999 to May 2000 for
multiple chloroacetanilides and their ESA and OA metabolites (WI DATCP, 2000). The 27
monitoring wells, 22 private drinking water wells, and 23 municipal wells sampled for the study
were chosen based on past detections of pesticides or proximity to agricultural fields to increase
the probability of detecting the pesticides. (These are not, therefore, representative of average
occurrence, but are wells of known high occurrence.) The primary use of these herbicides in
Wisconsin is for pre-emergence control of annual grasses in corn. Results for metolachlor are
presented in Exhibit 8-30. The private drinking water wells showed the highest detection
frequencies and concentrations as compared to the other two well types. In this study, the
laboratory limit of quantitation (LOQ) was 0.25 |ig/L for metolachlor. No detected
concentrations exceeded one-half the HRL or the HRL.
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Exhibit 8-30: Wisconsin Groundwater Detections of Metolachlor
Well Type
Wells with
Detects
Percent
Detections
Average Detect
(ng/L)
Highest Detect
(ng/L)
Monitoring Wells
4
15%
1.7
2.1
Private Drinking Water Wells
8
36%
1.4
5.9
Municipal Wells
0
0%
ND
ND
Source: Wl DATCP, 2000
ND = no detections in this category
Metolachlor data were also available from the Pesticides in Ground Water Database
(PGWDB). The PGWDB is a compilation of data from groundwater studies conducted by
federal, state, and local governments, the pesticide industry, and other institutions between 1971
and 1991 (USEPA, 1992). Data from 68,824 wells in 45 states are included. The vast majority of
the wells (65,865) were drinking water wells. Monitoring was conducted for 258 pesticides and
45 degradates. Not all studies tested for every compound.
Because PGWDB data come from multiple sources, they should be interpreted with
caution. Different studies were conducted for different reasons and used different sampling
techniques and analytical methods. Detection limits (DLs) were not uniform. The data are not
geographically representative: results might be biased high because areas with suspected
contamination are likely to have been sampled more frequently than pristine areas.
According to the data compiled in the PGWDB, metolachlor was detected in 213 (0.96
percent) of 22,255 wells. Metolachlor was found in 20 out of 29 states where monitoring was
conducted. Exhibit 8-31 shows the range of concentrations by state (USEPA, 1992). Minimum
detected concentrations are reported in Exhibit 8-31; these minimum values may be indicative of
reporting levels used. No detected concentrations exceeded the HRL. The maximum detection of
metolachlor in Wisconsin (159 |ig/L) exceeded one-half the HRL.
Exhibit 8-31: Metolachlor Occurrence Data from the PGWDB, 1971-1991
State
Number of Wells with Metolachlor
Detections
Range of Detected Concentrations
(ng/L)
Arizona
1
6.9
California
0
-
Connecticut
5
0.2-26.0
Delaware
9
0.1 - 12.0
Florida
4
0.15-0.52
Georgia
0
-
Iowa
28
0.04-22.0
Illinois
7
0.09-12.0
Indiana
3
0.3-7.9
Kansas
0
-
Louisiana
0
-
Massachusetts
1
0.24
Minnesota
15
0.10-2.4
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State
Number of Wells with Metolachlor
Detections
Range of Detected Concentrations
(ng/L)
Maryland
1
120.0
Mississippi
0
-
North Dakota
0
-
Nebraska
6
trace - 2.32
New Jersey
3
0
1
New York
7
0.13-112
Ohio
71
0.001 -6.03
Oklahoma
0
-
Oregon
0
-
Pennsylvania
15
trace - 48
South Dakota
4
0.09-0.12
Texas
2
5.3-5.7
Virginia
11
0.02-2.86
Vermont
6
1.10-7.20
Washington
0
-
Wisconsin
14
0.08- 157.0
Source: USEPA, 1992
National metolachlor occurrence data can be augmented by reviewing metolachlor
occurrence data collected in the Corn Belt States, where metolachlor use is highest. Data from
Iowa, Illinois, Indiana, and Ohio are available (Hallberg et al., 1996; USEPA, 1999; Kross et al.,
1990; Kolpin et al., 1997; University of Iowa, 2009).
A statewide rural well water survey was conducted by the Iowa Department of Natural
Resources, the Geological Survey Bureau, and the University of Iowa Center for Health Effects
of Environmental Contamination. Phase 2 of the survey (2006-2008) involved the sampling and
analysis of groundwater from 473 private drinking water wells in 83 counties in Iowa (University
of Iowa, 2009). Metolachlor was an analyte in the Phase 2 study and was detected in 9 of the 469
samples from this study with a method detection limit (MDL) of 0.05 |ig/L.
In Iowa, Safe Drinking Water Act (SDWA) compliance monitoring data from surface
water and groundwater PWSs for the years 1988 through 1995 reveal that approximately 16
percent of samples analyzed for metolachlor had detections of the compound, with a maximum
concentration of 9.4 |ig/L, which is less than one-half the HRL and the HRL. The 99th percentile
concentration of all samples was 2.4 |ig/L, also less than one-half the HRL and the HRL
(Hallberg et al., 1996). In a comparison of compliance monitoring data from Illinois, Indiana,
and Ohio, mostly collected between 1993 and 1997, the percentage of samples with detections
ranged between 0.5 percent for Ohio and 5.2 percent for Illinois. Illinois also had the highest
percentage (7.3 percent) of PWSs with detections (USEPA, 1999).
Phase I of the Iowa State-Wide Rural Well-Water Survey, conducted in 1988 through
1989 to assess pesticide occurrence in rural private wells, established a statistically significant
correlation between increasing well depth and decreasing pesticide contamination, as evidenced
by the lower detection frequency of metolachlor in drinking water wells 50 or more feet deep
(Kross et al., 1990). This finding is corroborated by the analysis of Illinois compliance
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monitoring data described above. Although only 7.3 percent of all PWSs in Illinois had
metolachlor detections at an MRL of 0.04 |ig/L, the rate was approximately 65 percent for
surface water PWSs (USEPA, 1999). Nevertheless, data compiled by the Iowa Groundwater
Monitoring Program indicate a significant increase in median metolachlor concentration in Iowa
groundwater from 1982 to 1995. The increase in groundwater detections appears to follow the
trend of increasing statewide metolachlor use (Kolpin et al., 1997).
In 1998, USGS, the New York State Department of Environmental Conservation, and
Suffolk County Department of Health Services sampled wells in Suffolk County with known or
suspected pesticide residues. Samples were collected from 50 wells that tap the surficial sand-
and-gravel water-table aquifer in Suffolk County between May and August. Phillips et al. (1999)
reported occurrence values for metolachlor and its degradates using a common threshold of 0.05
|ig/L. Metolachlor was detected in more than 35 percent of samples in agricultural areas. In
residential and mixed land use areas, metolachlor was detected in approximately 10 percent of
samples (Phillips et al., 1999). The maximum detected concentration of metolachlor was less
than 5 ng/L which is less than one-half the HRL and the HRL.
8.4.3 Other Data
The Centers for Disease Control and Prevention (CDC) Fourth National Report on Human
Exposure to Environmental Chemicals, 2001-2002
Since 1999, the National Health and Nutrition Examination Survey (NHANES) has
examined the U.S. population annually and released the data in 2-year cycles. The survey is
based on a representative sample of the U.S. population based on age, gender, and race/ethnicity
(CDC, 2019). The Fourth National Report on Human Exposure to Environmental Chemicals was
published in 2009 (CDC, 2009). This report includes data on metolachlor mercapturate (a
metolachlor metabolite) in urine from monitoring conducted in 2001-2002. With a sample size of
2,538, the 95th percentile concentration of metolachlor mercapturate in urine was below the limit
of detection (LOD). The LOD was 0.2 |ig/L. Please note that this value cannot be compared to
the HRL since it represents a human urine concentration, not a drinking water concentration.
Metolachlor mercapturate in human tissue can have its origin in exposure via drinking water,
food, or other routes.
8.5 Analytical Methods
EPA has published five analytical methods for the analysis of metolachlor in drinking
water:
• EPA Method 507, Revision 2.1, Determination of Nitrogen- and Phosphorus-
Containing Pesticides in Water by Gas Chromatography with a Nitrogen-Phosphorus
Detector. Mean recoveries in fortified reagent water and synthetic groundwaters
range from 84 to 94%, with Relative Standard Deviations (RSD) of 4 to 10%
(USEPA, 1995b).
• EPA Method 508.1, Revision 2.0, Determination of Chlorinated Pesticides,
Herbicides, and Organohalides by Liquid-Solid Extraction and Electron Capture Gas
Chromatography. Mean recoveries in fortified reagent water range from 113 to
130%, with RSDs of 3.6 to 37.7 % (USEPA, 1995c).
• EPA Method 525.2, Revision 2.0, Determination of Organic Compounds in Drinking
Water by Liquid-Solid Extraction and Capillary Column Gas Chromatography/Mass
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Spectrometry. Mean recoveries in in fortified reagent water and tap water range from
75 to 117%, with RSDs of 3.2 to 8% (USEPA, 1995d).
• EPA Method 525.3, Version 1.0, Determination of Semivolatile Organic Chemicals
in Drinking Water by Solid Phase Extraction and Capillary Column Gas
Chromatography/Mass Spectrometry (GC/MS). The Lowest Concentration Minimum
Reporting Levels (LCMRLs) generated by the laboratory that developed the method
range from 0.11 to 0.14 |ig/L in Full Scan mode and from 0.004 to 0.019 |ig/L in
Selected Ion Monitoring (SIM) mode. Mean recoveries in fortified reagent water and
finished drinking water (from groundwater and surface water sources) in Full Scan
mode range from 90.3% to 120%, with RSDs of 0.42% to 7.9%. Mean recoveries in
fortified reagent water and finished drinking water (from groundwater sources) in
SIM mode range from 101% to 115%>, with RSDs of 1.0 to 6.3%. Metolachlor was
not analyzed in precision and accuracy studies performed using two sources of
drinking water from surface water (one with Total Organic Carbon (TOC) of 2.0
mg/L and a second with TOC of 2.52 mg/L and a hardness of 137 mg/L) and in one
of two sources of drinking water from groundwater (recovery was not observed in
groundwater containing a TOC of 0.73 mg/L and a hardness of 325 mg/L) (USEPA,
2012c).
• EPA Method 551.1, Revision 1.0, Determination of Chlorinated Disinfection By-
products, Chlorinated Solvents, and Halogenated Pesticides/Herbicides in Drinking
Water by Liquid/Liquid Extraction and Gas Chromatography with Electron Capture
Detection. Mean recoveries in preserved fortified reagent water, preserved fortified
fulvic acid enriched reagent water, and preserved fortified groundwater range from
101 to 120%, with RSDs of 0.87 to 10.35% (USEPA, 1995e).
Laboratories participating in UCMR 2 were required to use EPA Method 525.2 and, as noted in
Section 8.4.2, were required to report metolachlor values at or above the EPA-defined MRL of 1
|.ig/L (72 FR 367; USEPA, 2007). The MRL was set based on the capability of multiple
laboratories at the time.
8.6 Treatment Technologies
EPA evaluates whether suitable treatment technologies are available prior to
promulgating a final National Primary Drinking Water Regulation (NPDWR).
EPA's Drinking Water Treatability Database (USEPA, 2020) summarizes available
technical literature on the efficacy of treatment technologies for a range of priority drinking
water contaminants. Information on metolachlor in the Database is based on a literature search
conducted in December 2009. The following processes were found to be effective for the control
of metolachlor: membrane separation using reverse osmosis (greater than 99 percent removal),
powdered activated carbon (43 to greater than 99 percent removal), ozone (approximately 60
percent removal) and ozone coupled with hydrogen peroxide (96 percent removal). Isotherm
studies showed granular activated carbon (GAC) capacities to be high for metolachlor, and in
full-scale plants removals ranged from 31 to 56 percent at the time of monitoring. Chlorine,
chlorine dioxide, and conventional treatments were found to be ineffective. The exact percentage
removal a water system may achieve with a given technology will be dependent upon a variety
of factors, including source water quality and water system characteristics. Using conditions not
typical of drinking water treatment such as a pH of 3, ultraviolet irradiation alone and ultraviolet
irradiation plus hydrogen peroxide were suggestive of being effective.
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USEPA. 2018. S-metolachlor: Human Health Risk Assessment for (1) Establishment of
Tolerances for New Uses on Chicory, Stevia and Swiss Chard; (2) Tolerance Translations
from Table Beet Tops, Turnip Greens, and Radish Tops to Crop Group 2 (Leaves of Root
and Tuber Vegetables), except Sugar Beets; (3) Tolerance Conversions (i) from Crop
Subgroup 4B to Crop Subgroup 22B (Leaf Petiole Vegetable), (ii) from Crop Subgroup
5 A to Crop Group 5-16 (Brassica, Head and Stem Vegetable) and (iii) from Crop
Subgroup 5B to Crop Subgroup 4-16B (Brassica Leafy Greens); and (4) Tolerance
Expansions of Representative Commodities to (i) Cottonseed Subgroup 20C, and (ii)
Stalk and Stem Vegetable Subgroup 22A, except Kohlrabi. Human Health Risk
Assessment. EPA-HQ-OPP-2017- 0465. September.
USEPA. 2019a. CompTox Chemicals Dashboard, Searched by DSSTox Substance Id =
DTXSID4022448. Available on the Internet at:
https://comptox.epa. gov/dashboard/dsstoxdb/results?search=DTXSID4022448.
USEPA. 2019b. Exposure Factors Handbook Chapter 3 (Update): Ingestion of Water and Other
Select Liquids. USEPA Office of Research and Development, Washington, DC.
EPA/600/R-18/259F.
USEPA. 2020. Drinking Water Treatability Database.
https://iaspub.epa.gov/tdb/pages/general/home.do. Last updated March 2020.
United States Geological Survey (USGS). 2016. National Water Information System (NWIS)
Water-Quality Web Services. Available on the Internet at:
https://waterdata.usgs.gov/nwis. Last modified December 2016.
USGS. 2018. Pesticide National Synthesis Project, Pesticide Use Maps. Available on the Internet
at: http://water.usgs.gov/nawqa/pnsp/usage/maps/compound listing.php?vear=02.
Accessed December 2018.
Water Quality Portal (WQP). 2017. Water Quality Portal Data Warehouse. Available on the
Internet at: https://www.waterqualitvdata.us/. Data Warehouse consulted December 2017.
WQP. 2018. Water Quality Portal Data Warehouse. Available on the Internet at:
https://www.waterqualitvdata.us/. Data Warehouse consulted September 2018.
Wisconsin Department of Agriculture, Trade, and Consumer Protection (WIDATCP). 2000.
Chloroacetanilide Herbicide Metabolites in Wisconsin Groundwater. Final Report. ARM
Pub 82 (June 2000). Madison, WI: Groundwater Unit, ARM division, WI DATCP.
World Health Organization (WHO). 2003. Metolachlor in Drinking-Water. Background
document for development of WHO Guidelines for Drinking-Water Quality. Originally
published in Guidelines for Drinking-Water Quality, 2nd ed., Vol. 2., Health Criteria and
Other Supporting Information (World Health Organization, Geneva, 1996).
WHO/SDE/WSH/03.04/39. Copyright WHO 2003. Available on the Internet at:
https://www.who.int/water sanitation health/dwq/chemicals/metolachlor.pdf.
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Chapter 9:
Nitrobenzene
A chapter from:
Final Regulatory Determination 4 Support Document
EPA Report 815-R-21-001
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Contents
Contents 9-2
Exhibits 9-3
Abbreviations 9-4
9.1 Contaminant Background and Chemical and Physical Properties 9-6
9.2 Sources and Environmental Fate 9-7
9.2.1 Production, Use, and Release 9-7
9.2.2 Environmental Fate 9-11
9.3 Health Effects 9-12
9.3.1 Toxicokinetics 9-12
9.3.2 Available Health Effects Assessments 9-12
9.3.3 Health Effects 9-13
9.3.4 Basis of the HRL 9-14
9.3.5 Health Effects Data Gaps 9-15
9.4 Occurrence 9-15
9.4.1 Occurrence in Ambient Water 9-15
9.4.2 Occurrence in Drinking Water 9-20
9.4.3 Other Data 9-29
9.5 Analytical Methods 9-30
9.6 Treatment Technologies 9-30
9.7 References 9-31
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Exhibits
Exhibit 9-1: Chemical Structure of Nitrobenzene 9-6
Exhibit 9-2: Physical and Chemical Properties of Nitrobenzene 9-6
Exhibit 9-3: IUR Reported Annual Manufacture and Importation of Nitrobenzene in the
United States, 1986-2006 (pounds) 9-8
Exhibit 9-4: CDR Reported Annual Manufacture and Importation of Nitrobenzene in the
United States, 2011-2015 (pounds) 9-8
Exhibit 9-5: Environmental Releases (in pounds) of Nitrobenzene in the United States,
1988-2016 9-9
Exhibit 9-6: Summary and State Count of Total Releases and Total Surface Water
Discharges of Nitrobenzene, 1988-2016 9-10
Exhibit 9-7: Available Health Effects Assessments for Nitrobenzene 9-13
Exhibit 9-8: Nitrobenzene NAWQA Data - Summary of Samples and Sites 9-17
Exhibit 9-9: Nitrobenzene NWIS Data, 1991 -2016 9-18
Exhibit 9-10: Nitrobenzene STORET Data - Summary of Detected Concentrations 9-19
Exhibit 9-11: Nitrobenzene STORET Data - Summary of Samples and Sites 9-19
Exhibit 9-12: Nitrobenzene STORET Data - Summary of States 9-19
Exhibit 9-13: Nitrobenzene Occurrence Data from UCMR 1 Assessment Monitoring -
Summary of Detected Concentrations 9-21
Exhibit 9-14: Nitrobenzene Occurrence Data from UCMR 1 Assessment Monitoring -
Summary of Samples 9-21
Exhibit 9-15: Nitrobenzene Occurrence Data from UCMR 1 Assessment Monitoring -
Summary of System and Population Served Data - All Detections 9-22
Exhibit 9-16: Nitrobenzene Occurrence Data from UCMR 1 Assessment Monitoring -
Summary of System and Population Served Data - Detections > V2 the HRL 9-23
Exhibit 9-17: Nitrobenzene Occurrence Data from UCMR 1 Assessment Monitoring -
Summary of System and Population Served Data - Detections > HRL 9-24
Exhibit 9-18: Nitrobenzene State Drinking Water Occurrence Data - Summary of Detected
Concentrations 9-25
Exhibit 9-19: Nitrobenzene State Drinking Water Occurrence Data - Summary of Samples.. 9-27
Exhibit 9-20: Nitrobenzene State Drinking Water Occurrence Data - Summary of Systems .. 9-28
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Abbreviations
AT SDR
Agency for Toxic Substances and Disease Registry
BMDL
Benchmark Dose Level
BMDS
Benchmark Dose Software
BMR
Benchmark Response
BW
Body Weight
CAS
Chemical Abstracts Service
CCL 4
Fourth Contaminant Candidate List
CCR
Consumer Confidence Report
CDC
Centers for Disease Control and Prevention
CDR
Chemical Data Reporting
CSF
Cancer Slope Factor
CWS
Community Water System
DWI
Drinking Water Intake
EPA
Environmental Protection Agency
EPCRA
Emergency Planning and Community Right-to-Know Act
G6PD
Glucose-6-Phosphate Dehydrogenase
GC/MS
Gas Chromatography/Mass Spectrometry
HRL
Health Reference Level
HSDB
Hazardous Substances Data Bank
ICR
Information Collection Request
IRIS
Integrated Risk Information System
IUR
Inventory Update Reporting
Kh
Henry's Law Constant
Koc
Organic Carbon Partitioning Coefficient
Kow
Octanol-Water Partitioning Coefficient
LOAEL
Lowest Observed Adverse Effect Level
LOD
Limit of Detection
MDL
Method Detection Limit
metHb
Methemoglobin
MRL
Minimum Reporting Level
NAWQA
National Water-Quality Assessment
ND
No Detection
NHANES
National Health and Nutrition Examination Survey
NIRS
National Inorganics and Radionuclides Survey
NPDWR
National Primary Drinking Water Regulation
NTP
National Toxicology Program
NWIS
National Water Information System
PA
Principal Aquifer
PBPK
Physiologically Based Pharmacokinetic
POD
Point of Departure
PWS
Public Water System
RfD
Reference Dose
RSC
Relative Source Contribution
RSD
Relative Standard Deviation
SD
Standard Deviation
STORET
Storage and Retrieval Data System
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SYR2
Second Six-Year Review
SYR3
Third Six-Year Review
TRI
Toxics Release Inventory
TSCA
Toxic Substances Control Act
UCM
Unregulated Contaminant Monitoring
UCMR
Unregulated Contaminant Monitoring Rule
UCMR 1
First Unregulated Contaminant Monitoring Rule
UCMR 2
Second Unregulated Contaminant Monitoring Rule
UCMR 3
Third Unregulated Contaminant Monitoring Rule
USGS
United States Geological Survey
VOC
Volatile Organic Compound
WHO
World Health Organization
WQP
Water Quality Portal
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Chapter 9: Nitrobenzene
The Environmental Protection Agency (EPA) is evaluating nitrobenzene as a candidate
for regulation as a drinking water contaminant under the fourth Contaminant Candidate List
(CCL 4) Regulatory Determinations process. Information on the CCL 4 process is found in
Chapter 1. Background on data sources used to evaluate CCL 4 chemicals is found in Chapter 2.
This chapter presents information and analyses specific to nitrobenzene, including
background information on the contaminant, information on contaminant sources and
environmental fate, an analysis of health effects, an analysis of occurrence in ambient and
drinking water, and information about the availability of analytical methods and treatment
technologies.
9.1 Contaminant Background and Chemical and Physical Properties
Nitrobenzene, also known as nitrobenzol, is a synthetic aromatic nitro compound and
occurs as an oily, flammable liquid at room temperature and as greenish-yellow crystals below
42 degrees F. As described below, it has several industrial uses.
Exhibit 9-1 presents the structural formula for nitrobenzene. Physical and chemical
properties and other reference information are listed in Exhibit 9-2.
Exhibit 9-1: Chemical Structure of Nitrobenzene
yo
Source: USEPA, 2019a
Exhibit 9-2: Physical and Chemical Properties of Nitrobenzene
Property
Data
Chemical Abstracts Service (CAS)
Registry Number
98-95-3 (ChemlDPIus, 2018)
EPA Pesticide Chemical Code
056501 (not currently registered in the U.S.; HSDB, 2010)
Chemical Formula
CeHsNCh (ChemlDPIus, 2018)
Molecular Weight
123.11 g/mol (HSDB, 2010)
Color/Physical State
Greenish-yellow crystals or yellow liquid (HSDB, 2010)
Boiling Point
210.8 deg C (HSDB, 2010)
Melting Point
5.7 deg C (HSDB, 2010)
Density
1.2037 g/mL (HSDB, 2010)
Freundlich Adsorption Coefficient
3,490 (|ig/g)(L/|ig)1/n (Speth et al., 2001)
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Property
Data
Vapor Pressure
0.245 mm Hg at 25 deg C (HSDB, 2010)
Henry's Law Constant (Kh)
2.4E-05 atm-m3/mol at 25 deg C (HSDB, 2010)
Log Kow
1.85 (dimensionless) (HSDB, 2010)
Koc
30.6-370 L/kg in soil
89 L/kg in river sediment (HSDB, 2010)
Solubility in Water
2,090 mg/L at 25 deg C (HSDB, 2010)
Other Solvents
Soluble in many organic solvents and miscible with ethanol, diethyl ether,
and benzene (HSDB, 2010)
Conversion Factors
(at 25 deg C, 1 atm)
1 ppm (v/v) = 0.199 mg/m3
1 mg/m3 = 5.03 ppm (v/v)
(calculated)
Note: Many of these properties are temperature dependent. Values are given for properties at 20-25 deg C unless
otherwise noted. Due to varying experimental conditions, and due to the variabilities associated with modeling, the
standard information sources may provide a range of values. Where more than one value was available from these
sources, one value was selected for this table based on best professional judgment.
9.2 Sources and Environmental Fate
9.2.1 Production, Use, and Release
Nitrobenzene is commonly used as a chemical intermediate in the production of aniline
and drugs such as acetaminophen. Nitrobenzene is also used in the manufacturing of shoe
polishes, metal polishes, lubricating oils, synthetic rubber, polyurethanes, dyes, and pesticides
(ATSDR, 1990). Nitrobenzene was formerly registered by EPA as a pesticide (EPA Pesticide
code 056501), although it is not currently registered in the U.S., according to the Hazardous
Substances Data Bank (HSDB, 2010). Production data for nitrobenzene are available from
EPA's Inventory Update Reporting (IUR) program, and industrial release data are available from
EPA's Toxics Release Inventory (TRI), as described below. Additional information about these
sources is provided in Chapter 2.
Inventory Update Reporting (IUR) / Chemical Data Reporting (CDR) Program
Under the authority of the Toxic Substances Control Act (TSCA), EPA gathers
information on production (including both manufacture and importation) of industrial chemicals.
Under the IUR, producers provided information once every four years from 1986 to 2006. Since
2012, producers have continued to provide information in accordance with the CDR Rule that
superseded the IUR in 2011. Under CDR, producers collect annual production data and report it
once every four years.
Until 2006, the IUR regulation required manufacturers and importers of organic chemical
substances included on the TSCA Chemical Substance Inventory to report site and
manufacturing information for chemicals produced (i.e., manufactured or imported) in amounts
of 10,000 pounds or more at a single site. In 2006, the minimum threshold for reporting was
increased to 25,000 pounds and reporting began for inorganic chemicals (USEPA, 2008a).
Among changes made under CDR, a two-tier system of reporting thresholds was implemented,
with 25,000 pounds as the threshold for some contaminants and 2,500 pounds as the threshold
for others (USEPA, 2014; USEPA, 2018). As a result of program modifications, the results from
2006 and later might not be directly comparable to results from earlier years. Under CDR, every
four years manufacturers and importers are required to report annual data from each of the
previous four years, provided that the thresholds of 2,500 or 25,000 pounds are met during at
least one of the four years (USEPA, 2018).
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For the historical IUR data, EPA assigned one of eight production volume ranges for
each chemical included in the inventory. The ranges used for the 2006 reports differ slightly
from those used in the 1986 through 2002 reports, as described in Chapter 2. Exhibit 9-3 presents
the publicly available information on production of nitrobenzene in the United States from 1986
to 2006 as reported under IUR. These data indicate that production of nitrobenzene in the United
States increased between 1986 and 1990 and has remained at over 1 billion pounds per year since
1990.
Exhibit 9-4 presents the production data for nitrobenzene in the United States from 2011
to 2015 as reported under CDR. Production of nitrobenzene was reported as approximately 2.6
billion pounds in 2011, and remained within the range of one to five billion pounds annually
from 2012 to 2015.
Exhibit 9-3: IUR Reported Annual Manufacture and Importation of Nitrobenzene in
the United States, 1986-2006 (Pounds)
Chemical Inventory Update Reporting Cycle
1986
1990
1994
1998
2002
2006
Range of
Production /
Importation Volume
> 500 million
- 1 billion
Over 1 billion
Over 1 billion
Over 1 billion
Over 1 billion
1 billion and
greater
Source: USEPA, 2008a
Exhibit 9-4: CDR Reported Annual Manufacture and Importation of Nitrobenzene
in the United States, 2011-2015 (Pounds)
Chemical Inventory Update Re
porting Cycle
2011
2012
2013
2014
2015
Range of Production /
Importation Volume
2,620,500,426
1 billion - 5
billion
1 billion - 5
billion
1 billion - 5
billion
1 billion - 5
billion
Source: USEPA, 2018
Note: 2011 results are reported not as a range, but as an exact value.
Toxics Release Inventory (TRI)
EPA established TRI in 1987 in response to section 313 of the Emergency Planning and
Community Right-to-Know Act (EPCRA). EPCRA section 313 requires the reporting of annual
information on toxic chemical releases from facilities that meet specific criteria. This reported
information is maintained in a database accessible through TRI Explorer (USEPA, 2017).
Although TRI can provide a general indication of release trends, it has limitations. Not all
facilities are required to report all releases. Facilities are required to report releases if they
manufacture or process more than 25,000 pounds of a chemical or use more than 10,000 pounds
per year. Reporting requirements have changed over time (e.g., reporting thresholds have
decreased) so conclusions about temporal trends should be drawn with caution. TRI data are
meant to reflect releases and should not be used to estimate general public exposure to a
chemical (USEPA, 2019b).
TRI data for nitrobenzene from the years 1988 through 2016 are summarized in Exhibit
9-5 (USEPA, 2017). Beginning in the year 1988, underground injection dominated total reported
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releases, fluctuating between approximately 191,000 pounds (in 2003) and over 860,000 pounds
(in 1992). On-site air emissions were reported in the range of tens of thousands of pounds
annually over the 23-year period of record. Other on-site releases were generally low, although
in 2003 over 50,000 pounds of nitrobenzene were reported as released to land. Off-site reported
releases were variable, ranging from 148 pounds (in 2013) to almost 70,000 pounds (in 1988).
Total reported releases remained in the hundreds of thousands of pounds per year between 1988
and 2016.
Exhibit 9-5: Environmental Releases (in Pounds) of Nitrobenzene in the United
States, 1988-2016
Year
On-Site Releases (in pounds)
Total Off-
Site
Releases
(in pounds)
Total On-
and Off-Site
Releases
(in pounds)
Air
Emissions
Surface
Water
Discharges
Underground
Injection
Releases to
Land
1988
41,279
7,283
819,000
3,538
69,570
940,670
1989
39,870
2,913
554,000
3,597
24,287
624,667
1990
67,344
2,624
608,000
3,255
3,319
684,542
1991
53,548
2,032
468,404
935
8,403
533,322
1992
52,610
524
864,949
427
14,370
932,880
1993
72,681
309
309,441
328
370
383,129
1994
41,009
1,999
815,285
226
2,290
860,809
1995
25,529
874
330,344
43
961
357,751
1996
37,653
951
193,527
46
3,825
236,002
1997
64,784
299
638,059
7
240
703,389
1998
81,297
1,152
422,619
62
12,383
517,513
1999
77,544
372
211,347
65
63,908
353,236
2000
41,934
120
297,084
18
6,721
345,877
2001
40,466
238
302,988
6,644
19,235
369,571
2002
68,798
53
240,425
93
11,467
320,836
2003
54,062
30
191,062
52,766
1,009
298,930
2004
55,796
60
271,046
640
1,113
328,655
2005
35,574
20
551,667
61
1,049
588,371
2006
25,642
42
532,504
142
20,687
579,017
2007
24,318
411
571,298
995
4,104
601,126
2008
27,974
189
458,495
34
935
487,627
2009
69,463
77
300,867
642
516
371,566
2010
74,800
175
246,009
74
1,420
322,477
2011
54,081
45
249,049
112
757
304,043
2012
41,173
52
198,600
227
227
240,279
2013
27,070
60
402,400
144
148
429,822
2014
25,114
46
274,174
235
359
299,929
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Year
On-Site Releases (in pounds)
Total Off-
Site
Releases
(in pounds)
Total On-
and Off-Site
Releases
(in pounds)
Air
Emissions
Surface
Water
Discharges
Underground
Injection
Releases to
Land
2015
23,968
37
432,294
87
356
456,743
2016
22,455
37
507,916
8
189
530,605
Source: USEPA, 2017
Exhibit 9-6 presents a summary of total releases and total surface water discharges that
includes the count of states reporting releases for the years 1988 through 2016 (USEPA, 2017).
The number of states reporting releases of nitrobenzene each year ranged from 10 to 18 over the
years 1988-2016. The number of states reporting surface water discharges of nitrobenzene each
year ranged from one to six for the years 1988-2016. (For the purposes of TRI, "state" counts
include the District of Columbia and United States territories in addition to the 50 states.)
Exhibit 9-6: Summary and State Count of Total Releases and Total Surface Water
Discharges of Nitrobenzene, 1988-2016
Year
Total Release
(in pounds)
Count of States
with Releases
Total Surface
Water
Discharges
(in pounds)
Count of States
with Surface
Water
Discharges
1988
940,670
13
7,283
6
1989
624,667
12
2,913
6
1990
684,542
12
2,624
5
1991
533,322
14
2,032
4
1992
932,880
13
524
5
1993
383,129
12
309
3
1994
860,809
12
1,999
3
1995
357,751
14
874
3
1996
236,002
10
951
3
1997
703,389
12
299
3
1998
517,513
13
1,152
3
1999
353,236
18
372
3
2000
345,877
17
120
3
2001
369,571
18
238
4
2002
320,836
16
53
3
2003
298,930
17
30
2
2004
328,655
14
60
1
2005
588,371
15
20
2
2006
579,017
15
42
2
2007
601,126
14
411
2
2008
487,627
14
189
2
2009
371,566
15
77
1
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Year
Total Release
(in pounds)
Count of States
with Releases
Total Surface
Water
Discharges
(in pounds)
Count of States
with Surface
Water
Discharges
2010
322,477
16
175
2
2011
304,043
15
45
2
2012
240,279
13
52
1
2013
429,822
15
60
1
2014
299,929
14
46
1
2015
456,743
13
37
1
2016
530,605
12
37
1
Source: USEPA, 2017
9.2.2 Environmental Fate
Exposure to nitrobenzene occurs in workplace environments where the chemical is used
or produced; however, it is metabolized into other chemicals (e.g., p-nitrophenol and p-
aminophenol) (ATSDR, 1990; USEPA, 2009a). EPA lists nitrobenzene as a hazardous air
pollutant (USEPA, 2013). Based on nitrobenzene's physical properties and prevalence, air is a
potentially significant source of exposure to the chemical. The principal source of nitrobenzene
released to water is effluent discharge from the manufacture of nitrobenzene (ATSDR, 1990).
As discussed in Chapter 2, the measures used by EPA to assess mobility include (where
available) the organic carbon partitioning coefficient (Koc), log octanol-water partitioning
coefficient (log Kow), Henry's Law Constant (Kh), water solubility, and vapor pressure.
Nitrobenzene's vapor pressure of 0.245 mm Hg indicates that when released to air, the
contaminant will be present in the vapor phase. Koc values of 30.6-370 L/kg and 89 L/kg in river
sediment suggest that nitrobenzene will be moderately to highly mobile in soil but may sorb to
sediment. Based on the vapor pressure and a Kh of 2.4E-05 atm-m3/mol, volatilization from
moist soils and water will be an important loss process for nitrobenzene, while volatilization
from dry soils will not. Nitrobenzene is readily biodegradable and was found to have a half-life
of 56 days in aerobic, pH-neutral sandy loam. Half-lives for volatilization from water have been
estimated to be 44 hours for a model river and 17 days for a model lake Another study found a
half-life for overall loss from Rhine river water to be one day. Nitrobenzene can degrade in water
through several mechanisms. Nitrobenzene has been found to have a half-life of 133 days via
photolysis. Reaction of nitrobenzene with nitrate and sunlight has been found to have a half-life
of 11 hours. Nitrobenzene can also undergo rapid biodegradation in anaerobic sediments.
Biodegradation occurs more slowly or not at all under aerobic conditions in groundwater and/or
sediment tests, with degradation rates ranging from no degradation to rapid degradation after a
lag time of 70-85 days. A half-life of 56 days in an aerobic column of sandy loam was observed,
although nitrobenzene may be toxic to microorganisms at high concentrations (HSDB, 2010).
Chapter 2 presents scales used by EPA to informally rank chemical contaminants' likely
mobility (understood as their tendency to partition to water rather than other media) and
persistence as "high," "moderate," or "low" based on physical and chemical properties (see
Exhibit 2-2 and Exhibit 2-3). For nitrobenzene, a log Kow of 1.85 and a Kh of 2.4E-05 atm-
m3/mol indicate a moderate likelihood of partitioning to water. A Koc of 30.6-370 L/kg (which
includes the value of 89 L/kg) indicates a moderate to high likelihood of partitioning to water.
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The water solubility of 2,090 mg/L indicates a high likelihood of partitioning to water. The
aerobic biodegradation half-life of 56 days indicates moderate persistence.
9.3 Health Effects
9.3.1 Toxicokinetics
There are limited data in humans on the toxicokinetics of nitrobenzene after oral
exposure. Two human studies demonstrated that the nitrobenzene metabolites, p-aminophenol
and p-nitrophenol are excreted in the urine (Myslak et al., 1971; Von Oettingen, 1941).
Animal studies have demonstrated extensive intestinal absorption of nitrobenzene (Parke,
1956; Albrecht and Neumann, 1985; Reddy et al., 1976; Rickert et al., 1983). Animal studies
have also demonstrated that metabolism of nitrobenzene consists of both oxidation and reduction
reactions by intestinal microflora, hepatic microsomes and erythrocytes (USEPA, 2009a).
Metabolites resulting from the oxidation reactions include o-, m-, and p-nitrophenol and the
reduction metabolites include nitrosobenzene, phenylhydroxylamine, and aniline (USEPA,
2009a). Some of the toxicological effects of nitrobenzene may be due to one or more of these
metabolites. For example, Reddy et al. (1976), reported that germ-free rats do not develop
methemoglobinemia after oral exposure to nitrobenzene, supporting the hypothesis that intestinal
microbes might play a role in metabolite formation and that these metabolites play a role in the
toxicity of nitrobenzene. These findings led to the hypothesis that a nitrobenzene metabolite,
such as aniline (which is formed by a bacterial reduction of nitrobenzene in the gut) might be
responsible for the methemoglobin (metHb) formation (Reddy et al., 1976; Rickert et al., 1983).
Radiolabeled nitrobenzene was identified in the blood, liver, kidney and lung of rodents,
indicating a wide distribution of nitrobenzene and/or its metabolites (USEPA, 2009a). Similar to
human studies, nitrobenzene is primarily excreted through the urine in rats (Rickert et al. 1983;
Albrecht and Neumann, 1985). It appears that the elimination of nitrobenzene is on the order of
days in both rodents and humans (USEPA, 2009a).
There are no available physiologically based pharmacokinetic (PBPK) models for
nitrobenzene (USEPA, 2009a).
9.3.2 Available Health Effects Assessments
Exhibit 9-7 presents a summary of the three available health effects assessments for
nitrobenzene. These health effects assessments include: a 1990 Agency for Toxic Substances and
Disease Registry (ATSDR) Toxicological Profile (ATSDR, 1990), a 2009 World Health
Organization (WHO) Drinking Water Guideline (WHO, 2009) and a 2009 Integrated Risk
Information System (IRIS) Toxicological Review (USEPA, 2009a). The ATSDR and WHO
assessments do not provide a reference dose (RfD) or cancer slope factor (CSF) for nitrobenzene.
As indicated by the bolded row, the 2009 IRIS review (USEPA, 2009a) was selected for use in
the calculation of the health reference level (HRL) (see Section 9.3.4 below for details on that
calculation).
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Exhibit 9-7: Available Health Effects Assessments for Nitrobenzene
Health
Assessment
Assessment
Year
RfD
(mg/kg/day)
Principal
study for
RfD
CSF
(mg/kg/day)"1
Principal
study for CSF
Cancer
Descriptor
EPA IRIS
2009
0.002
NTP, 1983
No value
NA
(L) Likely to be
carcinogenic
WHO
2009
No value
NA
No value
NA
NA
ATSDR
1990
No value
NA
No value
NA
NA
9.3.3 Health Effects
Systemic
Methemoglobin formation is the primary effect noted following oral exposure to
nitrobenzene in humans and animals. Methemoglobin formation is observed at the lowest doses
tested (9.38 mg/kg/day) and is associated with other blood effects (e.g., changes in red blood cell
count, hemoglobin and hematocrit) and histopathological responses such as splenic congestion in
rodents (USEPA, 2009a). Nitrobenzene exposure at higher doses resulted in changes to relative
organ weights and histopathological lesions in the liver, kidney, thyroid, and brain and mortality
(100 - 300 mg/kg/day) in rodent species (USEPA, 2009a).
Ingestion of nitrobenzene in humans is reported to result in neurological effects,
including headache, nausea, vertigo, confusion, unconsciousness, apnea, and coma (ATSDR,
1990).
Reproductive and Developmental Effects
The testis, epididymis, and seminiferous tubules of the male reproductive system are
targets of nitrobenzene toxicity in rodents. Nitrobenzene exposure via the oral and inhalation
routes results in histopathologic lesions of the testis and seminiferous tubules, testicular atrophy,
a large decrease in sperm count, and a reduction of sperm motility and/or viability, which
ultimately contribute to a loss of fertility in male rats and mice (NTP, 1983; Bond et al., 1981;
Koida et al., 1995; Matsuura et al., 1995; Kawashima et al., 1995). These data suggest that
nitrobenzene is a male-specific reproductive toxicant (USEPA, 2009a).
Cancer Data and Classification
Under the Guidelines for Carcinogen Risk Assessment (USEPA, 2005a), nitrobenzene is
classified as "likely to be carcinogenic to humans" by any route of exposure (USEPA, 2009a). A
two-year inhalation cancer bioassay in rats and mice (Cattley et al., 1994; CUT, 1993) reported
an increase in several tumor types in both species. However, the lack of available data, including
a PBPK model that might predict the impact of the intestinal metabolism on serum levels of
nitrobenzene and its metabolites following oral exposures, precluded EPA's IRIS program from
deriving an oral CSF (USEPA, 2009a). Additionally, a metabolite of nitrobenzene, aniline, is
classified as a probable human carcinogen (B2) (USEPA, 1988).
Nitrobenzene has been shown to be non-genotoxic in most studies and was classified as,
at most, weakly genotoxic in the 2009 USEPA IRIS assessment (ATSDR, 1990; USEPA,
2009a).
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Potentially Sensitive Lifestages/Groups
The 2009 IRIS toxicological review identifies susceptible populations and lifestages.
Infants and children are potentially more susceptible to the effects of nitrobenzene exposure at
multiple timepoints in development. Additionally, those with genetic diseases that affect metHb
formation, including genetic deficiencies in NADH-cytochrome b5 reductase (also known as
methemoglobin reductase), or glucose-6-phosphate dehydrogenase (G6PD, which plays a critical
role in red blood cells) could be more susceptible to the effects of nitrobenzene exposure
(USEPA, 2009a).
9.3.4 Basis of the HRL
EPA selected an RfD of 0.002 mg/kg/day based on the 2009 IRIS assessment (USEPA,
2009a). The critical study was a 1983 National Toxicology Program (NTP) 90-day oral study in
male and female rats and mice (NTP, 1983, as cited in USEPA, 2009a). Since this NTP study is
unpublished, the study details are summarized from the 2009 IRIS assessment (USEPA, 2009a).
In the 90-day NTP study (NTP, 1983), rats (10/sex/group) and mice (10/sex/group) were
exposed to 5 doses of nitrobenzene (0, 9.38, 18.75, 37.5, 75, or 150 mg/kg/day for F344 rats and
0, 18.75, 37.5, 75, 150, or 300 mg/kg/day for B6C3F1 mice). The rats were more sensitive to the
effects of nitrobenzene exposure than the mice, and changes in absolute and relative organ
weights, hematologic parameters, splenic congestion, and histopathologic lesions in the spleen,
testis and brain were reported. Specifically, subchronic nitrobenzene exposure induced increased
liver and kidney weights in both sexes, and decreased testis weight in male rats. However, the
statistically significant increases in liver and kidney weights were generally not supported by
histopathology. Statistically significant changes were also observed in hematologic effects in
rats, including decreased hematocrit, hemoglobin, and red blood cell counts and increases in
reticulocyte counts and methemoglobin. These changes were statistically significant in males at
9.38 mg/kg/day for increased hemoglobin and methemoglobin and at 18.75 mg/kg/day for the
other hematologic parameters. Based on statistically significant changes in absolute and relative
organ weights, splenic congestion, and increases in reticulocyte count and metHb concentration,
a lowest observed adverse effect level (LOAEL) of 9.38 mg/kg/day was identified for the
subchronic oral effects of nitrobenzene in F344 male rats (USEPA, 2009a).
Benchmark dose software (BMDS) (version 1.4.1c; USEPA, 2007) was applied to
estimate candidate points-of-departure (PODs) for deriving an RfD for nitrobenzene. Data for
splenic congestion and increases in reticulocyte count and metHb concentration were modeled.
The POD derived from the male rat increased metHb data with a benchmark response (BMR) of
1 standard deviation (SD) was selected as the basis of the RfD (see USEPA, 2009a for additional
detail). Therefore, the benchmark dose level (BMDL) used as the POD is a BMDLisd of 1.8
mg/kg/day.
In deriving the RfD, EPA's IRIS program applied a composite uncertainty factor of 1,000
to account for interspecies extrapolation (10), intraspecies variation (10), subchronic-to-chronic
study extrapolation (3), and database deficiency (3) (USEPA, 2009a). Thus, the RfD calculated
in the 2009 IRIS assessment is 0.002 mg/kg/day. The overall confidence in the RfD was medium
because the critical effect is supported by the overall database and is thought to be protective of
reproductive and immunological effects observed higher doses; however, there are no chronic or
multigenerational reproductive/developmental oral studies available for nitrobenzene. Because
the critical effect in this study (increased metHb in the adult rat) is not specific to a sensitive
subpopulation or lifestage, the general adult population was selected in deriving the HRL.
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BW
HRL = RfD* — * RSC
mq/kq 80 kq
HRL = 0.002 ' * f- * 20%
day 2 ^
day
ma ng
HRL = 0.0128—— = 12.8^
Lj Lj
HRL = 10 — (rounded)
Lj
RfD = Reference Dose (mg/kg/day); toxicity value selected based on protocol hierarchy
BW = Body weight (kg); based on adult default value of 80 kg
DWI = Drinking Water Intake (L/day); based on adult default value of 2.5 L/day
RSC = Relative Source Contribution, or the level of exposure believed to result from
drinking water when compared to other sources (e.g., food, ambient air), is 20 percent
when used for HRL derivation.
9.3.5 Health Effects Data Gaps
Health data gaps for nitrobenzene relate primarily to the limited data for the oral exposure
route. Studies on chronic oral exposure to nitrobenzene do not exist. Indeed, the 1983 NTP study
is the only oral exposure study over an extended time (90 days) for nitrobenzene. Developmental
and reproductive studies are also needed, especially considering that the male reproductive
system appears to be a target of nitrobenzene toxicity in rodents. Additionally, data to support
PBPK modeling would facilitate development of an oral cancer slope factor based on the
inhalation data. In support of developing a PBPK model, research aimed at identifying the mode
of action of nitrobenzene would be helpful to determine if toxicokinetic differences exist based
on the route of exposure.
9.4 Occurrence
This section presents data on the occurrence of nitrobenzene in ambient water and
drinking water in the United States. As described in section 9.3, an HRL of 10 |ig/L was
calculated for nitrobenzene based on non-carcinogenic effects. HRLs are risk-derived
concentrations against which EPA evaluates the occurrence data to determine if contaminants
occur at levels of potential public health concern. Occurrence data from various sources
presented below are analyzed with respect to the HRL and one-half the HRL. When possible,
estimates of the population exposed at concentrations above the HRL and above one-half the
HRL are presented.
For additional background information about data sources used to evaluate occurrence,
please refer to Chapter 2.
9.4.1 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. Contaminant
occurrence in ambient water provides information on the potential for contaminants to adversely
affect drinking water supplies. Occurrence data for nitrobenzene in ambient water are available
from the United States Geological Survey (USGS) National Water-Quality Assessment
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(NAWQA) program, the USGS National Water Information System (NWIS) database, EPA's
legacy Storage and Retrieval Data System (STORET) data available through the Water Quality
Portal (WQP), and several published USGS studies.
United States Geological Survey (USGS) National Water-Quality Assessment (NAWQA)
Ambient Water Analyses
USGS instituted the NAWQA program in 1991 to examine ambient water quality status
and trends in the United States. The NAWQA program generates high quality contaminant
occurrence and other water quality parameter data for significant watersheds and aquifers across
the nation. The program collects data on surface water and groundwater chemistry, hydrology,
land use, stream habitat, and aquatic life in parts or all of nearly all 50 States. The program is
designed to apply nationally consistent methods to provide a uniform basis for contaminant
occurrence comparisons and assessments among study basins across the country and over time.
The occurrence assessments can also serve to facilitate interpretation of natural and
anthropogenic factors affecting national water quality. For more detailed information on the
NAWQA program design and implementation, refer to Leahy and Thompson (1994) and
Hamilton et al. (2004).
The process of sampling, analysis, and data synthesis is divided into cycles of
approximately ten years: Cycle 1 covered 1991-2001, Cycle 2 covered 2002-2012, and Cycle 3 is
ongoing and covers 2013-2023. Study units are sampled and analyzed on a staggered schedule
within each cycle. Each NAWQA cycle begins with a two-year startup phase for planning and
retroactive analysis, followed by a three-year intensive data collection phase, and finally a five-
year phase for analyzing the data, developing reports, and continuing a low level of monitoring
(NRC, 2012).
During Cycle 1 (1991-2001), 51 study units were sampled. Data were gathered from
6,307 wells from 272 groundwater networks or clusters and from 6,400 sampling points at 505
surface water monitoring sites, primarily rivers and streams but also some lakes and reservoirs
(NRC, 2002). In Cycle 2 (2002-2012), the number of study units was reduced from 51 to 42
(NRC, 2012). Long-term stream monitoring was established at 113 streams representing 8 major
river basins. Long-term groundwater monitoring was established at sites representing 20
principal aquifers with more than 10 to 15 years of consistent monitoring data available (Rowe et
al., 2013).
Sampling for Cycle 3 is currently underway (2013-2023). Surface water monitoring will
be conducted at 313 sites, increased from 113 sites in Cycle 2 (Rowe et al., 2013). Groundwater
assessments in Cycle 3 will be designed to evaluate status and trends at the principal aquifer
(PA) and national scales. Assessments are planned in 24 PAs that account for the majority of
current and future national groundwater use for drinking water. Data available through 2017 are
presented in this report. For more details on the Cycle 3 sampling design, refer to Rowe et al.,
(2010 and 2013).
EPA's analysis of the NAWQA data is a simple, non-parametric occurrence analysis that
provides summary statistics to characterize contaminant occurrence. EPA calculated detection
frequencies as the percentage of samples and the percentage of sites with at least one detection,
without any censoring or weighting. (A detection is an analytical result equal to or greater than
the reporting level.) EPA reported the minimum and maximum detected concentrations and
calculated other descriptive statistics including the median, 90th percentile, and 99th percentile
concentrations (based only on samples with detections). Reporting levels varied over time during
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the NAWQA program. In some cases, therefore, the minimum concentration reported as a
detection could be lower than the highest reporting level.
Exhibit 9-8 presents analyses of the nitrobenzene NAWQA data, downloaded from the
WQP in September 2018 (WQP, 2018). Nitrobenzene was not detected in samples collected
under any of the three cycles. As noted above, NAWQA data are ambient water data, not
finished drinking water data.
Exhibit 9-8: Nitrobenzene NAWQA Data - Summary of Samples and Sites
Site Type
Detection Frequency
(detections are results > reporting level)
Concentration Values
(of detections, in |jg/L)
No. of
Samples
No. of
Samples
with
Detections
No. of
Sites
No. of
Sites with
Detections
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Cycle 1 (1991 -2001)
Groundwater
9
0
9
0
ND
ND
ND
ND
ND
Surface Water
17
0
12
0
ND
ND
ND
ND
ND
All Sites
26
0
21
0
ND
ND
ND
ND
ND
Cycle 2 (2002-2012)
Groundwater
0
0
0
0
ND
ND
ND
ND
ND
Surface Water
3
0
1
0
ND
ND
ND
ND
ND
All Sites
3
0
1
0
ND
ND
ND
ND
ND
Cycle 3 (2013-2017)
Groundwater
1,428
0
1,355
0
ND
ND
ND
ND
ND
Surface Water
151
0
51
0
ND
ND
ND
ND
ND
All Sites
1,579
0
1,406
0
ND
ND
ND
ND
ND
Source: WQP, 2018
National Water Information System (NWIS) Data
The National Water Information System (NWIS) is the Nation's principal repository of
water resources data USGS collects from more than 1.5 million sites (USGS, 2016). NWIS-Web
is the general online interface to the USGS NWIS database. Discrete water-sample and time-
series data are available from sites in all 50 States, including 5 million water samples with 90
million water-quality results. All USGS water quality and flow data are stored in NWIS,
including site characteristics, streamflow, groundwater level, precipitation, and chemical
analyses of water, sediment, and biological media, though not all parameters are available for
every site. NWIS houses the NAWQA data and includes other USGS data from unspecified
projects. NWIS contains many more samples at many more sites than the NAWQA Program and,
although NWIS is comprised of primarily ambient water data, some finished drinking water data
are included, as well. This section presents analyses of non-NAWQA data in NWIS, downloaded
from the WQP in December 2017 (WQP, 2017). These data do not overlap with the results
presented in Exhibit 9-8.
The results of the non-NAWQA NWIS nitrobenzene analyses are presented in Exhibit
9-9. Nitrobenzene was detected in approximately 1 percent of samples (60 out of 7,265) and at
approximately 1 percent of sites (25 out of 2,747). The median concentration based on detections
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was equal to 83.0 |ig/L. (Note that the NWIS data are presented as downloaded; potential outliers
were not evaluated or excluded from the analysis.)
Exhibit 9-9: Nitrobenzene NWIS Data, 1991 - 2016
Site Type
Detection Frequency
(detections are results > reporting level)
Concentration Values
(of detections, in |jg/L)
No. of
Samples
No. of
Samples
with
Detections
No.
of
Sites
No. of
Sites with
Detections
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Groundwater
4,842
7
2,128
7
0.13
0.310
0.692
0.969
1
Surface Water
2,423
53
628
18
15
85.0
100
174
240
All Sites1
7,265
60
2,747
25
0.13
83.0
99.0
165
240
Source: WQP, 2017
1 The number of groundwater sites plus the number of surface water sites and finished water sites is not equal to "All
Sites" because some sites may have been listed with more than one source water type in the data.
Storage and Retrieval (STORET) Data / Water Quality Portal (WQP)
From its launch in 1999 until it was decommissioned in June 2018, EPA's STORET Data
Warehouse was collaboratively populated with raw biological, chemical, and physical data from
surface water and groundwater sampling by federal, state and local agencies, Native American
tribes, volunteer groups, academics, and others. Legacy STORET data are accessible through the
WQP: https://www.waterqualitydata.us/portal/.
STORET data are from monitoring locations in all 50 states as well as multiple territories
and jurisdictions of the United States. Most data are from ambient waters, but in some cases
finished drinking water data are included as well. STORET's data quality limitations include
variations in the extent of national coverage and data completeness from parameter to parameter.
Data may have been collected as part of targeted, rather than randomized, monitoring.
This section presents analyses of STORET data, downloaded from the WQP in December
2017 (WQP, 2017). EPA reviewed STORET groundwater data from wells and surface water data
from lakes, rivers/streams, and reservoirs (WQP, 2017). The WQP also included public water
system (PWS) data from four states (Indiana, Missouri, Ohio, and Washington); EPA reviewed
these as well (WQP, 2017). It is unclear if the PWS data were collected prior to or subsequent to
treatment.
The results of the STORET analysis for nitrobenzene are presented in Exhibit 9-10
through Exhibit 9-12. These nitrobenzene samples were collected between 1980 and 2016. Of
the 1,573 sites sampled, 574 (36.5 percent) reported detections of nitrobenzene. Detected
concentrations ranged as high as 10,000 |ig/L. The 90th percentile concentration of detections
was equal to 10 |ig/L. The minimum detected concentration may be indicative of the reporting
levels used. (A minimum value of zero, on the other hand, could represent a detection that was
entered into the database as a non-numerical value (e.g., "Present").)
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Exhibit 9-10: Nitrobenzene STORET Data - Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (|jg/L)
Minimum1
Median
90th Percentile
Maximum
Groundwater
0
5.0
10
10,000
Surface Water
0
0.03
7.2
20
Total
0
0.44
10
10,000
PWS
0
0
0
0
Source: WQP, 2017
1A minimum value of zero may represent a detection that was entered into the database as a non-numerical value
(e.g., "Present").
Exhibit 9-11: Nitrobenzene STORET Data - Summary of Samples and Sites
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Total
Number of
Sites
Sites with Detections
Number
Percent
Number
Percent
Groundwater
3,098
610
19.69%
1,025
373
36.39%
Surface Water
1,878
586
31.20%
548
201
36.68%
Total
4,976
1,196
24.04%
1,573
574
36.49%
PWS
366
366
100.00%
176
176
100.00%
Source: WQP, 2017
Exhibit 9-12: Nitrobenzene STORET Data - Summary of States
Source Water
Type
Total
Number of
States
States with Detections
Number
Percent
Groundwater
10
7
70.00%
Surface Water
22
7
31.82%
Total1
25
11
44.00%
PWS
1
1
100.00%
Source: WQP, 2017
1 The number of states with groundwater data plus the number of
states with surface water data may not equal the "Total" number of
states providing data because some states provided both
groundwater and surface water data.
Additional Ambient Water Studies
For the National Highway Runoff Data and Methodology Synthesis, USGS conducted a
review of 44 highway and urban runoff studies implemented since 1970 (Lopes and Dionne,
1998). Nitrobenzene was an analyte in three stormwater studies at a reporting level of 5 |ig/L: in
Maricopa County, Arizona, in Colorado Springs, Colorado, and in Dallas/Fort Worth, Texas.
Nitrobenzene was not detected in any of the three studies. Note that the data from these studies
might also be included in the NWIS results presented earlier.
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9.4.2 Occurrence in Drinking Water
Data sources reviewed by the Agency for information on contaminant occurrence in
drinking water included: EPA's first, second, and third Unregulated Contaminant Monitoring
Rules (UCMR 1, UCMR 2, UCMR 3); Rounds 1 and 2 of the Agency's Unregulated
Contaminant Monitoring (UCM) program that preceded the Unregulated Contaminant
Monitoring Rule (UCMR); EPA's Information Collection Rule; EPA's National Inorganics and
Radionuclides Survey (NIRS); and a range of others as discussed in Chapter 2. Among the
sources reviewed, the following had data and information on nitrobenzene occurrence in
drinking water. These data and information are discussed in this section.
EPA's First Unregulated Contaminant Monitoring Rule (UCMR 1).
State drinking water monitoring programs.
Consumer Confidence Reports (CCRs) from PWSs.
USGS source water and drinking water studies
Note that there may be some overlap, as sources with different purposes and audiences
may have reported the same underlying data. UCMR 1 is a national data source. Other data
sources profiled in this section are considered "supplemental" sources. Also note that the
presentation of NWIS and STORET results in the ambient water section, above, includes some
finished water data and/or miscellaneous data from PWSs.
Primary Data Sources
First Unregulated Contaminant Monitoring Rule (UCMR 1), 2001-2003
UCMR 1 required the collection of data to support nationally representative estimates of
contaminant occurrence in PWSs. UCMR 1 monitoring occurred primarily from 2001 to 2003
and required surface water systems to monitor quarterly and groundwater systems to monitor
twice yearly. There were two tiers of monitoring: Assessment Monitoring for contaminants with
commonly used analytical method technologies, and Screening Survey monitoring for
contaminants that require specialized analytical method technologies not in wide or common use.
All large PWSs serving more than 10,000 people, plus a statistically representative
national sample of 800 small PWSs (serving 10,000 people or fewer) were required to conduct
UCMR 1 Assessment Monitoring. For the UCMR 1 Screening Survey, EPA required monitoring
by a representative sample of 120 large and 180 small PWSs. Monitoring by each PWS was
required during a 12-month period between January 2001 and December 2003. Due to the small
sample size, contaminant occurrence estimates based on data from UCMR 1 Screening Survey
are statistically less robust than those based on data from the UCMR 1 Assessment Monitoring.
(For more details on all aspects of UCMR 1, refer to USEPA, 1999; USEPA, 2001; USEPA,
2008b.)
Exhibit 9-13 through Exhibit 9-17 present UCMR 1 summary data for nitrobenzene. A
total of 33,576 finished water nitrobenzene samples were collected under the UCMR 1
Assessment Monitoring (3,268 small system samples and 30,308 large system samples). The
Minimum Reporting Level (MRL) for nitrobenzene was 10 |ig/L, which is equal to the HRL. For
small systems, there were no detections of nitrobenzene. The only two detections of nitrobenzene
were found in large community water systems (CWSs) in Florida, one served by groundwater
and the other by surface water. The groundwater system (serving approximately 17,000 people)
had a detection equal to 21.6 |ig/L; the surface water system (serving approximately 238,000
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people) had a detection equal to 100 |ig/L. Both of these detections exceeded the HRL. Note that
because the UCMR MRL was equal to 10 |ig/L (the same as the HRL), the estimates for
occurrence greater than one-half the HRL are constrained to only include those that are also
greater than the HRL.
The design of UCMR 1 permits estimation of national occurrence. To calculate national
extrapolations, the percent of systems (or population served) estimated to exceed a specified
threshold in a given category can be multiplied by the total number of systems (or population
served) in the nation in that category. In UCMR 1 analysis, the extrapolation methodology is
applied only to small systems. Because all large systems were required to participate in the
UCMR 1 Assessment Monitoring, national estimates of occurrence in this size category do not
require extrapolation. Rather, survey census figures are used. Total national occurrence is
estimated by summing the extrapolated or census figures from the two size categories. See
Chapter 2 for additional information on national extrapolations. The results of this national
extrapolation are presented in Exhibit 9-15 through Exhibit 9-17.
Exhibit 9-13: Nitrobenzene Occurrence Data from UCMR 1 Assessment
Monitoring - Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (in |jg/L) > MRL of 10 |jg/L
Minimum
Median
90th Percentile
99th Percentile
Maximum
Small Systems (serving < 10,000 people)
Groundwater
ND
ND
ND
ND
ND
Surface Water
ND
ND
ND
ND
ND
All Small Systems
ND
ND
ND
ND
ND
Large Systems (serving > 10,000 people) — CENSUS
Groundwater
21.6
21.6
21.6
21.6
21.6
Surface Water
100
100
100
100
100
All Large Systems
21.6
60.8
100
100
100
All Systems
All Water Systems
21.6
60.8
100
100
100
Source: USEPA, 2005b
ND = no detections in this category
Exhibit 9-14: Nitrobenzene Occurrence Data from UCMR 1 Assessment
Monitoring - Summary of Samples
Source Water
Type
Total
Number
of
Samples
Samples with
Detections
>MRL(10|jg/L)
Samples with
Detections > Vi HRL
(5 mq/l)
Sample:
Detection:
(10 mc
> with
s > HRL
/L)
Number
Percent
Number
Percent
Number
Percent
Small Systems (serving < 10,000 people)
Groundwater
2,341
0
0.00%
0
0.00%
0
0.00%
Surface Water
927
0
0.00%
0
0.00%
0
0.00%
All Small Systems
3,268
0
0.00%
0
0.00%
0
0.00%
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Source Water
Type
Total
Number
of
Samples
Samples with
Detections
>MRL(10|jg/L)
Samples with
Detections > Vi HRL
(5 mq/l)
Sample:
Detection:
(10 mc
> with
s > HRL
/L)
Number
Percent
Number
Percent
Number
Percent
Large Systems (serving > 10,000 people) — CENSUS
Groundwater
15,852
1
0.01%
1
0.01%
1
0.01%
Surface Water
14,456
1
0.01%
1
0.01%
1
0.01%
All Large Systems
30,308
2
0.01%
2
0.01%
2
0.01%
All Systems
All Water Systems
33,576
2
0.01%
2
0.01%
2
0.01%
Source: USEPA, 2005b
Exhibit 9-15: Nitrobenzene Occurrence Data from UCMR 1 Assessment
Monitoring - Summary of System and Population Served Data - All Detections
Source Water
Type
UCMR 1 Sample
Number (and Percent)
of Detections
> MRL (10 |jg/L) in the
UCMR 1 Sample
National Inventory
National Estimate1 of
the Number (and
Percent) of Detections
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Groundwater
589
1,937,327
0
(0.00%)
0
(0.00%)
56,072
36,224,336
0
(0.00%)
0
(0.00%)
Surface Water
207
820,755
0
(0.00%)
0
(0.00%)
4,342
9,190,254
0
(0.00%)
0
(0.00%)
All Small
Systems
796
2,758,082
0
(0.00%)
0
(0.00%)
60,414
45,414,590
0
(0.00%)
0
(0.00%)
Large Systems (serving > 10,000 people) - CENSUS
Groundwater
1,375
53,157,635
1
(0.07%)
16,990
(0.03%)
1,375
53,157,635
1
(0.07%)
17,000
(0.03%)
Surface Water
1,690
169,817,060
1
(0.06%)
238,368
(0.14%)
1,690
169,817,060
1
(0.06%)
238,000
(0.14%)
All Large
Systems
3,065
222,974,695
2
(0.07%)
255,358
(0.11%)
3,065
222,974,695
2
(0.07%)
255,000
(0.11%)
All Systems
All Water
Systems
3,861
225,732,777
2
(0.05%)
255,358
(0.11%)
63,479
268,389,285
2
(0.003%)
255,000
(0.10%)
Source: USEPA, 2005b
1 National estimates for the small systems are extrapolations, generated separately for each population-served size
stratum by multiplying the UCMR 1 national statistical sample findings of system/population percentages and national
system/population inventory numbers for PWSs developed from EPA's 4th Edition of the Baseline Handbook (see
Chapter 2 for discussion). The individual size stratum extrapolations (not shown) are then added to yield the national
estimate of groundwater PWSs with detections (and population served) and surface water PWSs with detections (and
population served). All nationally estimated population values for the small systems are rounded to the nearest
thousand. National estimates for the large systems are based directly on the UCMR 1 results, since this was a
census, i.e., all large systems were required to conduct UCMR 1 Assessment Monitoring. Due to rounding, some
calculations may appear to be slightly off.
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Exhibit 9-16: Nitrobenzene Occurrence Data from UCMR 1 Assessment
Monitoring - Summary of System and Population Served Data - Detections >
1/2 the HRL
Source Water
Type
UCMR 1 Sample
Number (and Percent)
of Detections > 1/2 HRL
(5 |jg/L) in the UCMR 1
Sample
National Inventory
National Estimate1 of
the Number (and
Percent) of Detections
> 1/2 HRL (5 |jg/L)
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Groundwater
589
1,937,327
0
(0.00%)
0
(0.00%)
56,072
36,224,336
0
(0.00%)
0
(0.00%)
Surface Water
207
820,755
0
(0.00%)
0
(0.00%)
4,342
9,190,254
0
(0.00%)
0
(0.00%)
All Small
Systems
796
2,758,082
0
(0.00%)
0
(0.00%)
60,414
45,414,590
0
(0.00%)
0
(0.00%)
Large Systems (serving > 10,000 people) - CENSUS
Groundwater
1,375
53,157,635
1
(0.07%)
16,990
(0.03%)
1,375
53,157,635
1
(0.07%)
17,000
(0.03%)
Surface Water
1,690
169,817,060
1
(0.06%)
238,368
(0.14%)
1,690
169,817,060
1
(0.06%)
238,000
(0.14%)
All Large
Systems
3,065
222,974,695
2
(0.07%)
255,358
(0.11%)
3,065
222,974,695
2
(0.07%)
255,000
(0.11%)
All Systems
All Water
Systems
3,861
225,732,777
2
(0.05%)
255,358
(0.11%)
63,479
268,389,285
2
(0.003%)
255,000
(0.10%)
Source: USEPA, 2005b
1 National estimates for the small systems are extrapolations, generated separately for each population-served size
stratum by multiplying the UCMR 1 national statistical sample findings of system/population percentages and national
system/population inventory numbers for PWSs developed from EPA's 4th Edition of the Baseline Handbook (see
Chapter 2 for discussion). The individual size stratum extrapolations (not shown) are then added to yield the national
estimate of groundwater PWSs with detections (and population served) and surface water PWSs with detections (and
population served). All nationally estimated population values for the small systems are rounded to the nearest
thousand. National estimates for the large systems are based directly on the UCMR 1 results, since this was a
census, i.e., all large systems were required to conduct UCMR 1 Assessment Monitoring. Due to rounding, some
calculations may appear to be slightly off.
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Exhibit 9-17: Nitrobenzene Occurrence Data from UCMR 1 Assessment
Monitoring - Summary of System and Population Served Data - Detections > HRL
Source Water
Type
UCMR 1 Sample
Number (and Percent)
of Detections > HRL (10
|jg/L) in the UCMR 1
Sample
National Inventory
National Estimate1 of
the Number (and
Percent) of Detections
> HRL (10 |jg/L)
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Groundwater
589
1,937,327
0
(0.00%)
0
(0.00%)
56,072
36,224,336
0
(0.00%)
0
(0.00%)
Surface Water
207
820,755
0
(0.00%)
0
(0.00%)
4,342
9,190,254
0
(0.00%)
0
(0.00%)
All Small
Systems
796
2,758,082
0
(0.00%)
0
(0.00%)
60,414
45,414,590
0
(0.00%)
0
(0.00%)
Large Systems (serving > 10,000 people) - CENSUS
Groundwater
1,375
53,157,635
1
(0.07%)
16,990
(0.03%)
1,375
53,157,635
1
(0.07%)
17,000
(0.03%)
Surface Water
1,690
169,817,060
1
(0.06%)
238,368
(0.14%)
1,690
169,817,060
1
(0.06%)
238,000
(0.14%)
All Large
Systems
3,065
222,974,695
2
(0.07%)
255,358
(0.11%)
3,065
222,974,695
2
(0.07%)
255,000
(0.11%)
All Systems
All Water
Systems
3,861
225,732,777
2
(0.05%)
255,358
(0.11%)
63,479
268,389,285
2
(0.003%)
255,000
(0.10%)
Source: USEPA, 2005b
1 National estimates for the small systems are extrapolations, generated separately for each population-served size
stratum by multiplying the UCMR 1 national statistical sample findings of system/population percentages and national
system/population inventory numbers for PWSs developed from EPA's 4th Edition of the Baseline Handbook (see
Chapter 2 for discussion). The individual size stratum extrapolations (not shown) are then added to yield the national
estimate of ground water PWSs with detections (and population served) and surface water PWSs with detections
(and population served). All nationally estimated population values for the small systems are rounded to the nearest
thousand. National estimates for the large systems are based directly on the UCMR 1 results, since this was a
census, i.e., all large systems were required to conduct UCMR 1 Assessment Monitoring. Due to rounding, some
calculations may appear to be slightly off.
In addition to Assessment Monitoring, described above, nitrobenzene was included in the
UCMR 1 Screening Survey with a different analytical method. With an MRL of 0.5 |ig/L,
nitrobenzene was not detected in any of the 2,306 samples taken.
Supplemental Data Sources
State Monitoring Data, 1995-2011
Because there is no available national database that receives and stores all relevant data
regarding the occurrence of regulated contaminants in public drinking water systems, EPA
conducts voluntary data requests from the states, territories, and tribes in support of national
occurrence assessments. These assessments are part of the Six-Year Review. Under the second
and third Six-Year Review (SYR2 and SYR3), a few states submitted PWS occurrence data for
unregulated contaminants along with the requested data on regulated contaminants. EPA was
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able to supplement the data on unregulated contaminants by downloading additional publicly
available monitoring data from state websites. For SYR2, the result was a collection of
unregulated contaminant monitoring data from nine states and other entities, such as tribes,
territories, and EPA Regions. For SYR3, the dataset of unregulated contaminant monitoring data
included results from 14 states/entities. For both rounds of the Six-Year Review, these
unregulated data provide varying degrees of completeness in their coverage of the states/entities
and are not necessarily representative of occurrence in those states/entities. For more details on
the Six-Year Review Information Collection Request (ICR) Dataset for SYR2, refer to USEPA
(2009b). For more details on the SYR3 ICR Dataset, refer to EPA's SYR3 occurrence analysis
(USEPA, 2016).
Drinking water occurrence data for nitrobenzene were available from California, Illinois,
and Ohio under SYR2 (1995-2005) and California and Michigan under SYR3 (2006-2011).1
Results are presented in Exhibit 9-18 through Exhibit 9-20. The exhibits do not include estimates
of population served because the nitrobenzene submitted under SYR2 and SYR3 represent only a
small portion of all PWSs in each state. See USEPA (2009b) and USEPA (2016) for the total
number of systems that submitted SYR2 and SYR3 data, respectively, from each state.
Comprehensive information about methods used and reporting levels is not available for this data
set. Minimum detected concentrations are reported in Exhibit 9-18; these minimum values may
be indicative of reporting levels used.
As noted above, the monitoring data from each state/entity are limited and not necessarily
representative of occurrence in the state/entity. The number of PWSs per state with nitrobenzene
data ranges from 85 PWSs in the Illinois SYR2 data to 2,801 PWSs in the Michigan SYR3 data.
Overall, detected concentrations ranged from 2 |ig/L to 5 |ig/L; nitrobenzene was only detected
in the California SYR3 data in 2 PWSs. No detections were greater than one-half the HRL or the
HRL (though one detection in California was equal to one-half the HRL).
Exhibit 9-18: Nitrobenzene State Drinking Water Occurrence Data - Summary of
Detected Concentrations
State
(Date Range)
Source Water
Type
(Sample Type)
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
99th
Percentile
Maximum
Second Six-Year Review (SYR2)
California
(1995-2005)
Groundwater
(Raw)
ND
ND
ND
ND
ND
Groundwater
(Finished)
ND
ND
ND
ND
ND
Surface Water
(Raw)
ND
ND
ND
ND
ND
Surface Water
(Finished)
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
1 Some states provided more than six years' worth of data to EPA in response to the SYR2 and SYR3 ICRs.
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State
(Date Range)
Source Water
Type
(Sample Type)
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
99th
Percentile
Maximum
Illinois
(1999-2005)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
Ohio
(2000-2005)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
Third Six-Year Review (SYR3)
California
(2006-2011)
Groundwater
(Raw)
2
3.5
4.7
5.0
5
Groundwater
(Finished)
ND
ND
ND
ND
ND
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Raw)
ND
ND
ND
ND
ND
Surface Water
(Finished)
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
2
3.5
4.7
5.0
5
Michigan
(2006-2011)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Not Provided2
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
Source: Data provided to EPA by states and downloaded by EPA from state websites
ND = no detections in this category
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
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Exhibit 9-19: Nitrobenzene State Drinking Water Occurrence Data - Summary of
Samples
State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Samples
Samples with
Detections
Samples with
Detections > V*
HRL (5 Mg/L)
Samples with
Detections > HRL
dOug/L)
Number
Percent
Number
Percent
Number
Percent
Second Six-Year Review (SYR2)
California
(1995-2005)
Groundwater
(Raw)
6,890
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Finished)
313
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
9
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
2,472
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Finished)
458
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
5
0
0.00%
0
0.00%
0
0.00%
Total
10,147
0
0.00%
0
0.00%
0
0.00%
Illinois
(1999-2005)
Groundwater
(Not Provided)1
188
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
148
0
0.00%
0
0.00%
0
0.00%
Total
336
0
0.00%
0
0.00%
0
0.00%
Ohio
(2000-2005)
Groundwater
(Not Provided)1
2,598
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
302
0
0.00%
0
0.00%
0
0.00%
Total
2,900
0
0.00%
0
0.00%
0
0.00%
Third Six-Year Review (SYR3)
California
(2006-2011)
Groundwater
(Raw)
2,992
2
0.07%
0
0.00%
0
0.00%
Groundwater
(Finished)
37
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
9
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
1,247
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Finished)
264
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
5
0
0.00%
0
0.00%
0
0.00%
Total
4,554
2
0.04%
0
0.00%
0
0.00%
Michigan
(2006-2011)
Groundwater
(Not Provided)1
8,166
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
665
0
0.00%
0
0.00%
0
0.00%
Not Provided2
39
0
0.00%
0
0.00%
0
0.00%
Total
8,870
0
0.00%
0
0.00%
0
0.00%
Source: Data provided to EPA by states and downloaded by EPA from state websites
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
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Exhibit 9-20: Nitrobenzene State Drinking Water Occurrence Data - Summary of
Systems
State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > Vi HRL
(5 ng/L)
Systems with
Detections > HRL
(10 ua/L)
Number
Percent
Number
Percent
Number
Percent
California
(1995-2005)
Groundwater
(Raw)
352
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Finished)
34
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
5
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
112
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Finished)
61
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
4
0
0.00%
0
0.00%
0
0.00%
Total
494
0
0.00%
0
0.00%
0
0.00%
Illinois
(1999-2005)
Groundwater
(Not Provided)1
49
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
36
0
0.00%
0
0.00%
0
0.00%
Total
85
0
0.00%
0
0.00%
0
0.00%
Ohio
(2000-2005)
Groundwater
(Not Provided)1
1,052
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
82
0
0.00%
0
0.00%
0
0.00%
Total
1,134
0
0.00%
0
0.00%
0
0.00%
Third Six-Year Review (SYR3)
California
(2006-2011)
Groundwater
(Raw)
137
2
1.46%
0
0.00%
0
0.00%
Groundwater
(Finished)
6
0
0.00%
0
0.00%
0
0.00%
Groundwater
(Not Provided)1
5
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
44
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Finished)
13
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
5
0
0.00%
0
0.00%
0
0.00%
Total
184
2
1.09%
0
0.00%
0
0.00%
Michigan
(2006-2011)
Groundwater
(Not Provided)1
2,677
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
91
0
0.00%
0
0.00%
0
0.00%
Not Provided2
33
0
0.00%
0
0.00%
0
0.00%
Total
2,801
0
0.00%
0
0.00%
0
0.00%
Source: Data provided to EPA by states and downloaded by EPA from state websites
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
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Water Systems' Consumer Confidence Reports (CCRs), 2010-2017
CCRs are annual water quality reports that CWSs are required to provide to their
customers. These reports summarize information on water sources, detected contaminants, and
system compliance with EPA drinking water standards; they may also include general
educational material. Under the CCR Rule (40 CFR Subpart O), CWSs with 15 or more
connections or serving at least 25 year-round residents must prepare and distribute a CCR to all
billing units or service connections every year. Systems serving 100,000 or more residents are
also required to post their current CCRs on a publicly accessible Internet site. EPA reviewed
CCRs published by the 22 systems that serve over one million customers (as identified in the
UCMR 3 database) for unregulated contaminant occurrence information for the years 2010
through 2017. Data on nitrobenzene were available from CCRs prepared by one CWS: Suffolk
County, New York. Reporting levels were not specified in any of the CCRs.
Suffolk County, New York included data on nitrobenzene in its CCRs from 2012 through
2017 CCRs. Suffolk County is served by groundwater from four major aquifers beneath Long
Island. Each of the six CCRs reported results from the previous year (e.g., the 2012 CCR
reported results for the year 2011). In all six years (2012 through 2017), nitrobenzene was
monitored for but was not detected. The number of samples collected was not reported in any
year.
United States Geological Survey (USGS') National Water Quality Assessment (NAWQA)
Source Water and Drinking Water Studies
Note that there may be some overlap between the NAWQA data assessments presented
earlier in the ambient water occurrence section and the summaries of NAWQA studies presented
below. The studies presented below include occurrence data from water sources for PWSs.
Volatile Organic Compounds (VOCs) in Drinking Water of Selected Community Water
Systems (Grady and Casey, 2001), 1993-1998
USGS compiled and analyzed occurrence data for VOCs in finished drinking water in 12
Northeast and Mid-Atlantic states (Connecticut, Delaware, Maine, Maryland, Massachusetts,
New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Virginia).
State agencies supplied USGS with VOC data collected during 1993 through 1998 for 20 percent
of the CWSs in the 12-state area, which were chosen to be representative in terms of geography,
water source, and system size. The reporting levels for the data ranged from 0.39 to 5.0 |ig/L. A
total of 24 samples from 4 CWSs were analyzed for nitrobenzene; nitrobenzene was not detected
in any sample (Grady and Casey, 2001).
9.4.3 Other Data
The Centers for Disease Control and Prevention (CDC) Fourth National Report on Human
Exposure to Environmental Chemicals, 2019 Updated Tables
Since 1999, the National Health and Nutrition Examination Survey (NHANES) has
examined the U.S. population annually and released the data in 2-year cycles. The survey is
based on a representative sample of the U.S. population based on age, gender, and race/ethnicity
(CDC, 2019). The Fourth National Report on Human Exposure to Environmental Chemicals was
published in 2009 (CDC, 2009). The exposure data tables have been updated several times since
the original publication, most recently in 2019 (CDC, 2019). The 2019 updated tables include
data on whole blood concentrations (ng/mL) for nitrobenzene. The most recent data are from the
2015-2016 reporting period. With a sample size of 3,037, the 95th percentile whole blood
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concentration was below the limit of detection (LOD). The LOD was 0.32 ng/mL. Please note
that this value cannot be compared to the HRL because it represents whole blood concentrations,
not drinking water concentrations.
9.5 Analytical Methods
EPA has published three analytical methods for the analysis of nitrobenzene in drinking
water:
• EPA Method 524.2, Revision 4.1, Measurement of Purgeable Organic Compounds in
Water by Capillary Column Gas Chromatography/Mass Spectrometry. Mean
recoveries in fortified reagent water, raw water, and tap water range from 100 to
110%, with Relative Standard Deviations (RSDs) of 2.4 to 18% (USEPA, 1995).
• EPA Method 526, Revision 1.0, Determination of Selected Semivolatile Organic
Compounds in Drinking Water by Solid Phase Extraction and Capillary Column Gas
Chromatography/Mass Spectrometry (GC/MS). Mean recoveries in fortified reagent
water, groundwater and surface water range from 72.4 to 114%, with RSDs of 1.9 to
6.9% (USEPA, 2000).
• EPA Method 529, Revision 1.0, Determination of Explosives and Related
Compounds in Drinking Water by Solid Phase Extraction and Capillary Column Gas
Chromatography/Mass Spectrometry (GC/MS). Mean recoveries in fortified reagent
water, chlorinated tap water (from a surface water source), and chlorinated tap water
(from a groundwater source with high hardness level) range from 68.5 to 107%), with
RSDs of 1.7 to 18% (USEPA, 2002).
Laboratories participating in UCMR 1 were required to use EPA Method 524.2 (for
Assessment Monitoring (List 1)) or 526 (for Screening Survey (List 2)) and, as noted in Section
9.4.2, were required to report nitrobenzene values at or above the EPA-defined MRL of 10 |ig/L
(using EPA Method 524.2) or 0.5 |ig/L (using EPA Method 526) (64 FR 50556; USEPA, 1999;
66 FR 2273; USEPA, 2001). The MRL of 10 |ig/L for use of EPA Method 524.2 was obtained
by multiplying the method detection limit (MDL) of 1.2 |ig/L from EPA Method 524.2 by a
factor of ten (and rounding). The MRL of 0.5 |ig/L for use of EPA Method 526 was obtained
from precision and accuracy measurements made during method development. The MRL of 0.5
|ig/L was also verified by second laboratory validation (USEPA, 1999; USEPA, 2001).
9.6 Treatment Technologies
EPA evaluates whether suitable treatment technologies are available prior to
promulgating a final National Primary Drinking Water Regulation (NPDWR).
EPA's Drinking Water Treatability Database (USEPA, 2020) summarizes available
technical literature on the efficacy of treatment technologies for a range of priority drinking
water contaminants. The following treatment technologies were found to be effective for the
removal of nitrobenzene: adsorptive media using MCM-41 (up to 72 percent removal),
biological filtration using Shewanellaputrefaciens CN32, Comoamonas sp. Strain JS765 (up to
100 percent removal), ozone in combination with copper and Fe(III) (95 percent removal),
ultraviolet irradiation (up to 90 percent removal), ultraviolet irradiation plus hydrogen peroxide
(up to 100 percent removal) and ultraviolet irradiation plus ozone (up to 100 percent removal).
The exact percentage removal a water system may achieve with a given technology will be
dependent upon a variety of factors, including source water quality and water system
characteristics.
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9.7 References
Agency for Toxic Substances and Disease Registry (ATSDR). 1990. Toxicological Profile for
Nitrobenzene. U.S. Department of Health and Human Services, U.S. Public Health
Service, Agency for Toxic Substances and Disease Registry, Atlanta, GA. Available on
the Internet at: http://www.atsdr.cdc.gov/toxprofiles/tp 140.pdf. Accessed February 2019.
Albrecht, W. and H.G. Neumann. 1985. Biomonitoring of aniline and nitrobenzene. Hemoglobin
binding in rats and analysis of adducts. Arch Toxicol 57:1-5 (as cited in USEPA, 2009a).
Bond, J.A., J.P. Chism, D.E. Rickert, et al. 1981. Induction of hepatic and testicular lesions in
Fischer 344 rats by single oral doses of nitrobenzene. Fundam Appl Toxicol 1:389-394
(as cited in USEPA, 2009a).
Cattley, R.C., J.I. Everitt, E.A. Gross, et al. 1994. Carcinogenicity and toxicity of inhaled
nitrobenzene in B6C3F1 mice and F344 and CD rats. Fundam Appl Toxicol 22:328-340
(as cited in USEPA, 2009a).
Centers for Disease Control and Prevention (CDC). 2009. Fourth National Report on Human
Exposure to Environmental Chemicals, Department of Health and Human Services,
Centers for Disease Control and Prevention. Available on the Internet at:
https://www.cdc.gov/exposurereport/pdf/fourthreport.pdf.
CDC. 2019. Fourth National Report on Human Exposure to Environmental Chemicals, Updated
Tables, January 2019: Volume One. Department of Health and Human Services, Centers
for Disease Control and Prevention. Available on the Internet at:
http://www.cdc.gov/exposurereport/.
Chemical Industry Institute of Toxicology (CUT). 1993. Initial submission: a chronic inhalation
toxicity study of nitrobenzene in B6C3F1 mice, Fischer 344 rats and Sprague-Dawley
(CD) rats. Chemical Industry Institute of Toxicology. Research Triangle Park, NC. EPA
Document No. FYI-OTS-0794-0970; NTIS No. OTS0000970 (as cited in USEPA,
2009a).
ChemlDPlus. 2018. Available on the Internet at: http://chem.sis.nlm.nih.gov/chemidplus/.
Accessed December 6, 2018.
Grady, S.J. and G.D. Casey. 2001. Occurrence and Distribution of Methyl tert-Butyl Ether and
Other Volatile Organic Compounds in Drinking Water in the Northeast and Mid-Atlantic
Regions of the United States, 1993-98. U.S. Geological Survey Water-Resources
Investigations Report 00-4228. 128 pp. Available on the Internet at:
https://pubs.er.usgs.gov/publication/wri004228.
Hamilton, P. A., T.L. Miller, and D.N. Myers. 2004. Water Quality in the Nation's Streams and
Aquifers: Overview of Selected Findings, 1991-2001. USGS Circular 1265. Available on
the Internet at: http://water.usgs.gov/pubs/circ/2004/1265/pdf/circularl265.pdf.
Hazardous Substances Data Bank (HSDB). 2010. Profile for Nitrobenzene. Available on the
Internet at: http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen7HSDB. Last updated April 30,
2010.
Kawashima, K., M. Usami, K. Sakemi, et al. 1995. Studies on the establishment of appropriate
spermatogenic endpoints for male fertility disturbance in rodent induced by drugs and
chemicals. I. Nitrobenzene. J Toxicol Sci 20:15-22 (as cited in USEPA, 2009a).
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Koida, M., T. Nakagawa, K. Irimura, et al. 1995. Effects on the sperm and testis of rats treated
with nitrobenzene: age and administration period differences. Teratology 52:39B (as
cited in USEPA, 2009a).
Leahy, P.P. and T.H. Thompson. 1994. Overview of the National Water-Quality Assessment
Program. U.S. Geological Survey Open-File Report 94-70. 4 pp. Available on the
Internet at: http://water.usgs.gov/nawqa/NAWQA.OFR94-7Q.html.
Lopes, T.J. and S.G. Dionne. 1998. A Review of Semivolatile and Volatile Organic Compounds
in Highway Runoff and Urban Stormwater. U.S. Geological Survey Open-File Report 98-
409. 67 pp.
Matsuura, I., N. Hoshino, Y. Wako, et al. 1995. Sperm parameter studies on three testicular
toxicants in rats. Teratology 52:39B (as cited in USEPA, 2009a).
Myslak, Z., J.K. Piotrowski, and E. Musialowicz. 1971. Acute nitrobenzene poisoning. A case
report with data on urinary excretion of p-nitrophenol and p-aminophenol. Arch Toxikol
28:208-213 (as cited in USEPA, 2009a).
National Research Council (NRC). 2002. Opportunities to Improve the U.S. Geological Survey
National Water Quality Assessment Program. Washington, D.C.: National Academy
Press. Available on the Internet at: https://www.nap.edu/read/10267/chapter/l.
NRC. 2012. Preparing for the Third Decade of the National Water-Quality Assessment
Program. Washington, D.C.: National Academies Press.
National Toxicology Program (NTP). 1983. Report on the subchronic toxicity via gavage of
nitrobenzene (C60082) in Fischer 344 rats and B6C3F1 mice [unpublished]. National
Toxicology Program, Prepared by the EG&G Mason Research Institute, Worcester, MA,
for the National Toxicology Program, National Institute of Environmental Health
Services, Public Health Service, U.S. Department of Health and Human Services,
Research Triangle Park, NC; MRI-NTP 08-83-19 (as cited in USEPA, 2009a).
Parke, D.V. 1956. Studies in detoxication. 68. The metabolism of [14C]nitrobenzene in the
rabbit and guinea pig. Biochem J62:339-346 (as cited in USEPA, 2009).
Reddy, B.G., L.R. Pohl, and G. Krishna. 1976. The requirement of the gut flora in nitrobenzene-
induced methemoglobinemia in rats. Biochem Pharmacol 25:1119-1122 (as cited in
USEPA, 2009a).
Rickert, D.E., J.A. Bond, R.M. Long, et al. 1983. Metabolism and excretion of nitrobenzene by
rats and mice. Toxicol ApplPharmacol 67:206-214 (as cited in USEPA, 2009a).
Rowe, G.L., K. Belitz, H.I. Essaid, R.J. Gilliom, P A. Hamilton, A.B. Hoos, D.D. Lynch, M.D.
Munn, and D.W. Wolock. 2010. Design of Cycle 3 of the National Water-Quality
Assessment Program, 2013-2023: Part 1: Framework of Water-Quality Issues and
Potential Approaches. U.S. Geological Survey Open-File Report 2009-1296.
https://pubs.usgs.gov/of/2009/1296/.
Rowe, G.L., K. Belitz, C.R. Demas, H.I. Essaid, R.J. Gilliom, P A. Hamilton, A.B. Hoos, C.J.
Lee, M.D. Munn, and D.W. Wolock. 2013. Design of Cycle 3 of the National Water-
Quality Assessment Program, 2013-23: Part 2: Science Plan for Improved Water-Quality
Information and Management. U.S. Geological Survey. Open-File Report 2013-1160.
https://pubs.er.usgs.gov/publication/ofr20131160.
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Speth, T.F., M.L. Magnuson, C.A. Kelty, and C.J. Parrett. 2001. Treatment Studies ofCCL
Contaminants. In: Proceedings, AWWA Water Quality Technology Conference,
November 11-15, Nashville, TN.
United States Environmental Protection Agency (USEPA). 1988. Chemical assessment summary
information for aniline (CAS No. 62-53-3) on the Integrated Risk Information System
(IRIS). National Center for Environmental Assessment, Washington, DC.
USEPA. 1995. Method 524.2. Measurement of Purgeable Organic Compounds in Water by
Capillary Column Gas Chromatography/Mass Spectrometry. Revision 4.1. National
Exposure Research Laboratory, Office of Research and Development. EPA 600-R-95-
131.
USEPA. 1999. Revisions to the Unregulated Contaminant Monitoring Regulation for Public
Water Systems; Final Rule. Federal Register 64(180): 50556, September 17, 1999.
USEPA. 2000. Method 526. Determination of Selected Semivolatile Organic Compounds in
Drinking Water by Solid Phase Extraction and Capillary Column Gas
Chromatography/Mass Spectrometry (GC/MS). Revision 1.0. National Exposure
Research Laboratory, Office of Research and Development. EPA 815-R-00-014.
USEPA. 2001. Unregulated Contaminant Monitoring Regulation for Public Water Systems;
Analytical Methods for List 2 Contaminants; Clarifications to the Unregulated
Contaminant Monitoring Regulation. Federal Register 66(8): 2273, January 11, 2001.
USEPA. 2002. Method 529. Determination of Explosives and Related Compounds in Drinking
Water by Solid Phase Extraction and Capillary Column Gas Chromatography/Mass
Spectrometry (GC/MS). Revision 1.0. National Exposure Research Laboratory, Office of
Research and Development. EPA 600-R-05-052.
USEPA. 2005a. Guidelines for Carcinogen Risk Assessment. United States Environmental
Protection Agency, Washington, DC. EPA-630-P-03-001F. Available on the Internet at:
http://www2.epa.gov/sites/production/files/2Q13-
09/documents/cancer guidelines final 3-25-05.pdf. Accessed February 2015.
USEPA. 2005b. First Unregulated Contaminant Monitoring Rule Dataset. Available on the
Internet at: https://www.epa.gov/dwucmr/occurrence-data-unregulated-contaminant-
monitoring-rule#l.
USEPA. 2007. Benchmark dose software (BMDS) version 1.4.1c (last modified November 9,
2007). Available on the Internet at
https://19ianuarv2017snapshot.epa.gov/bmds/benchmark-dose-software-bmds-
announcements ,html#05.
USEPA. 2008a. Using the 2006 Inventory Update Reporting (IUR) Public Data: Background
Document. Office of Pollution Prevention and Toxics. December. Available on the
Internet at:
https://www.epa.gov/sites/production/files/documents/iurdbbackground O.pdf.
USEPA. 2008b. The Analysis of Occurrence Data from the First Unregulated Contaminant
Monitoring Regulation (UCMR 1) in Support of Regulatory Determinations for the
Second Drinking Water Contaminant Candidate List. EPA 815-R-08-013.
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USEPA. 2009a. Toxicological review of nitrobenzene (CAS No. 98-95-3) in support of summary
information on the Integrated Risk Information System (IRIS). National Center for
Environmental Assessment, Washington, DC.
USEPA. 2009b. The Analysis of Regulated Contaminant Occurrence Data from Public Water
Systems in Support of the Second Six-Year Review of National Primary Drinking Water
Regulations. EPA 815-B-09-006. October 2009.
USEPA. 2013. The Clean Air Act Amendments of 1990 List of Hazardous Air Pollutants. Air
toxics web site. United States Environmental Protection Agency, Office of Air and
Radiation, Office of Air Quality Planning and Standards, Washington, DC. Available on
the Internet at: http://www.epa.gov/airtoxics/origl89.html. Accessed January 2015.
USEPA. 2014. Chemical Data Reporting. Fact Sheet: Basic Information. June. EPA Publication
740-K-13-001.
USEPA. 2016. The Analysis of Regulated Contaminant Occurrence Data from Public Water
Systems in Support of the Third Six-Year Review of National Primary Drinking Water
Regulations: Chemical Phase Rules and Radionuclides Rules. EPA 810-R-16-014.
December 2016.
USEPA. 2017. TRI Explorer: Trends. Available on the Internet at:
https://enviro.epa.gov/triexplorer/tri release.trends. Accessed November 2017.
USEPA. 2018a. CDR Reporting Requirements, https://www.epa.gov/chemical-data-
reporting/how-report-under-chemical-data-reporting. Accessed December 2018.
USEPA. 2018b. Drinking Water Treatability Database.
https://iaspub.epa.gov/tdb/pages/general/home.do. Accessed December 4, 2018.
USEPA. 2019a. CompTox Chemicals Dashboard, Searched by DSSTox Substance Id =
DTXSID3020964. Available on the Internet at:
https://comptox.epa. gov/dashboard/dsstoxdb/results?search=DTXSID3020964.
USEPA. 2019b. The Toxics Release Inventory (TRI) and Factors to Consider When Using TRI
Data. Available on the Internet at: https://www.epa.gov/toxics-release-inventory-tri-
program/factors-consider-when-using-toxics-release-inventory-data.
United States Geological Survey (USGS). 2016. National Water Information System (NWIS)
Water-Quality Web Services. Available on the Internet at:
https://waterdata.usgs.gov/nwis. Last modified December 2016.
Von Oettingen, W.F. 1941. The aromatic amino and nitro compounds, their toxicity and potential
dangers: A review of the literature. Washington, DC: U.S. Public Health Service. Public
Health Bulletin No. 271 (as cited in ATSDR, 1990).
Water Quality Portal (WQP). 2017. Water Quality Portal Data Warehouse. Available on the
Internet at: https://www.waterqualitvdata.us/. Data Warehouse consulted December 2017.
World Health Organization (WHO). 2009. Nitrobenzene in Drinking-water: Background
document for development of WHO Guidelines for Drinking-water Quality. World
Health Organization, Geneva, 2009. Available on the Internet at:
https://www.who.int/water sanitation health/water-
quality/guidelines/chemicals/ni trobenzene-background.pdf.
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WQP. 2018. Water Quality Portal Data Warehouse. Available on the Internet at:
https://www.waterqualitvdata.us/. Data Warehouse consulted September 2018.
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Chapter 10:
RDX
A chapter from:
Final Regulatory Determination 4 Support Document
EPA Report 815-R-21-001
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Contents
Contents 10-2
Exhibits 10-3
Abbreviations 10-4
10.1 Contaminant Background and Chemical and Physical Properties 10-6
10.2 Sources and Environmental Fate 10-7
10.2.1 Production, Use, Release 10-7
10.2.2 Environmental Fate 10-8
10.3 Health Effects 10-9
10.3.1 Toxicokinetics 10-9
10.3.2 Available Health Effect Assessments 10-10
10.3.3 Basis of the HRL 10-14
10.3.4 Data Base Limitations 10-15
10.3.5 Health Effects Data Gaps 10-15
10.4 Occurrence 10-15
10.4.1 Occurrence in Ambient Water 10-16
10.4.2 Occurrence in Drinking Water 10-18
10.5 Analytical Methods 10-22
10.6 Treatment Technologies 10-23
10.7 References 10-23
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Exhibits
Exhibit 10-1: Chemical Structure of RDX 10-6
Exhibit 10-2: Physical and Chemical Properties of RDX 10-6
Exhibit 10-3: IUR Reported Annual Manufacture and Importation of RDX in the United
States, 1986-2006 (pounds) 10-8
Exhibit 10-4: CDR Reported Annual Manufacture and Importation of RDX in the United
States, 2011-2015 (pounds) 10-8
Exhibit 10-5. Available Health Effects Assessments for RDX 10-10
Exhibit 10-6: RDXNWIS Data, 1991 -2016 10-17
Exhibit 10-7: RDX STORET Data - Summary of Detected Concentrations 10-17
Exhibit 10-8: RDX STORET Data - Summary of Samples and Sites 10-18
Exhibit 10-9: RDX STORET Data - Summary of States 10-18
Exhibit 10-10: RDX Occurrence Data from UCMR 2 Assessment Monitoring - Summary
of Detected Concentrations 10-19
Exhibit 10-11: RDX National Occurrence Measures Based on UCMR 2 Assessment
Monitoring Data - Summary of Samples 10-20
Exhibit 10-12: RDX National Occurrence Measures Based on UCMR 2 Assessment
Monitoring Data - Summary of System and Population Served Data - All
Detections 10-21
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Abbreviations
AT SDR
Agency for Toxic Substances and Disease Registry
BMDL
Benchmark Dose Level
BW
Body Weight
CAS
Chemical Abstracts Service
CCL
Contaminant Candidate List
CCL 4
Fourth Contaminant Candidate List
CDR
Chemical Data Reporting
CNS
Central Nervous System
CSF
Cancer Slope Factor
CWSS
Community Water System Survey
DNA
Deoxyribonucleic Acid
DWI
Drinking Water Intake
EPA
Environmental Protection Agency
EPISuite™
Estimation Programs Interface Suite™
GABA
y-Amino Butyric Amino Acid
GAC
Granular Activated Carbon
GC/MS
Gas Chromatography/Mass Spectrometry
HA
Health Advisory
HED
Human Equivalent Dose
HMX
Octahy dro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine
HRL
Health Reference Level
ICR
Information Collection Request
IRIS
Integrated Risk Information System
IUR
Inventory Update Reporting
Kh
Henry's Law Constant
Koc
Organic Carbon Partitioning Coefficient
Kow
Octanol-Water Partitioning Coefficient
LCMRL
Lowest Concentration Minimum Reporting Level
LD50
Median Lethal Dose
LOAEL
Lowest Observed Adverse Effect Level
MOA
Mode of Action
MRL
Minimum Reporting Level
NAWQA
National Water-Quality Assessment
ND
No Detection
NIRS
National Inorganics and Radionuclides Survey
NOAEL
No Observed Adverse Effect Level
NPDWR
National Primary Drinking Water Regulation
NWIS
National Water Information System
OW
Office of Water
PBPK
Physiologically Based Pharmacokinetic
POD
Point of Departure
PTV
Program Temperature Vaporizing
PWS
Public Water System
RDX
Royal Demolition eXplosive
RfD
Reference Dose
RSC
Relative Source Contribution
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RSD
Relative Standard Deviation
SDWIS
Safe Drinking Water Information System
SIM
Selected Ion Monitoring
STORET
Storage and Retrieval Data System
SYR2
Second Six-Year Review
SYR3
Third Six-Year Review
TRI
Toxics Release Inventory
TSCA
Toxic Substances Control Act
UCM
Unregulated Contaminant Monitoring
UCMR
Unregulated Contaminant Monitoring Rule
UCMR 1
First Unregulated Contaminant Monitoring Rule
UCMR 2
Second Unregulated Contaminant Monitoring Rule
UCMR 3
Third Unregulated Contaminant Monitoring Rule
USGS
United States Geological Survey
UV
Ultraviolet
WQP
Water Quality Portal
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Chapter 10: RDX
The Environmental Protection Agency (EPA) is evaluating RDX as a candidate for
regulation as a drinking water contaminant under the fourth Contaminant Candidate List (CCL 4)
Regulatory Determinations process. Information on the CCL 4 process is found in Chapter 1.
Background on data sources used to evaluate CCL 4 chemicals is found in Chapter 2.
This chapter presents information and analyses specific to RDX, including background
information on the contaminant, information on contaminant sources and environmental fate, an
analysis of health effects, an analysis of occurrence in ambient and drinking water, and
information about the availability of analytical methods and treatment technologies.
10.1 Contaminant Background and Chemical and Physical Properties
RDX is a nitrated triazine. The name RDX is an abbreviation of Royal Demolition
eXplosive. The formal chemical name is hexahydro-l,3,5-trinitro-l,3,5-triazine. Synonyms for
RDX include cyclonite, cyclotrimethylenenitramine, hexogen, hexolite, and
trimethylenetrinitramine (HSDB, 2012).
Exhibit 10-1 presents the structural formula for RDX. Physical and chemical properties
and other reference information are listed in Exhibit 10-2.
Exhibit 10-1: Chemical Structure of RDX
Ov
1
°\
N
II
o
V
/
11
O
0
Source: USEPA, 2019
Exhibit 10-2: Physical and Chemical Properties of RDX
Property
Data
Chemical Abstracts Service (CAS)
Registry Number
121-82-4 (ChemlDPIud, 2018)
EPA Pesticide Chemical Code
Not applicable (ChemlDPIud, 2018)
Chemical Formula
CsHeNeOe (ChemlDPIud, 2018)
Molecular Weight
222.116 g/mol (HSDB, 2012)
Color/Physical State
White crystalline solid (HSDB, 2012; ATSDR, 2012)
Boiling Point
276-280 deg C (HSDB, 2012)
Melting Point
205.5 deg C (HSDB, 2012)
Density
1.82 g/mL at 20 deg C (HSDB, 2012; ATSDR, 2012)
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Property
Data
Freundlich Adsorption Coefficient
13,000 (|ig/g)(L/|ig)1/n (Speth et al., 2001)
Vapor Pressure
4.1E-09 mm Hg at 20 deg C (Extrapolated, HSDB, 2012)
Henry's Law Constant (Kh)
2.0E-11 atm-m3/mol at 25 deg C (Estimated, HSDB, 2012; ATSDR, 2012)
Log Kow
0.87 (dimensionless) (HSDB, 2012; ATSDR, 2012)
Koc
42-167 L/kg (HSDB, 2012)
Solubility in Water
59.7 mg/L at 25 deg C (HSDB, 2012)
Other Solvents
Soluble in hot aniline, phenol, warm nitric acid, slightly soluble in ethyl
acetate, methanol, glacial acetic acid, ether and acetone (HSDB, 2012)
Conversion Factors
(at 25 deg C, 1 atm)
Not sufficiently volatile for conversion to be applicable
Note: Many of these properties are temperature dependent. Values are given for properties at 20-25 deg C unless
otherwise noted. Due to varying experimental conditions, and due to the variabilities associated with modeling, the
standard information sources may provide a range of values. Where more than one value was available from these
sources, one value was selected for this table based on best professional judgment.
10.2 Sources and Environmental Fate
10,2.1 Production, Use, Release
RDX is found in C-4 plastic explosives and used as a base charge for detonators when
making high explosive munitions (ATSDR, 2012). Non-military uses include demolition (e.g.,
buildings, bridges) (ATSDR, 2012). RDX was once an ingredient in some rat poisons (USEPA,
1992), but current use as a pesticide could not be confirmed.
Production data for RDX are available from EPA's Inventory Update Reporting (IUR)
and Chemical Data Reporting (CDR) programs, described below.
No industrial release data are available from EPA's Toxics Release Inventory (TRI). (The
list of chemicals for which TRI reporting is required has never included RDX (USEPA, 2017).)
Additional information about these sources is provided in Chapter 2.
Inventory Update Reporting (IUR) / Chemical Data Reporting (CDR) Program
Under the authority of the Toxic Substances Control Act (TSCA), EPA gathers
information on production (including both manufacture and importation) of industrial chemicals.
Under the IUR, producers provided information once every four years from 1986 to 2006. Since
2012, producers have continued to provide information in accordance with the CDR Rule that
superseded the IUR in 2011. Under CDR, producers collect annual production data and report it
once every four years.
Until 2006, the IUR regulation required manufacturers and importers of organic chemical
substances included on the TSCA Chemical Substance Inventory to report site and
manufacturing information for chemicals produced (i.e., manufactured or imported) in amounts
of 10,000 pounds or more at a single site. In 2006, the minimum threshold for reporting was
increased to 25,000 pounds and reporting began for inorganic chemicals (USEPA, 2008). Among
changes made under CDR, a two-tier system of reporting thresholds was implemented, with
25,000 pounds as the threshold for some contaminants and 2,500 pounds as the threshold for
others (USEPA, 2014a; USEPA, 2018a). As a result of program modifications, the results from
2006 and later might not be directly comparable to results from earlier years. Under CDR, every
four years manufacturers and importers are required to report annual data from each of the
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previous four years, provided that the thresholds of 2,500 or 25,000 pounds are met during at
least one of the four years (USEPA, 2018a).
For the historical IUR data, EPA assigned one of eight production volume ranges for
each chemical included in the inventory. The ranges used for the 2006 reports differ slightly
from those used in the 1986 through 2002 reports, as described in Chapter 2. Exhibit 10-3
presents the publicly available information on production of RDX in the United States from 1986
to 2006 as reported under IUR. Production of RDX decreased between 1994 and 1996 but
increased slightly in 2002 and 2006.
Exhibit 10-4 presents the production data for RDX in the United States from 2011 to
2015 as reported in CDR. Production of RDX was reported as approximately 6.3 million pounds
in 2011, and remained within the range of one to ten million from 2012 to 2015.
Exhibit 10-3: IUR Reported Annual Manufacture and Importation of RDX in the
United States, 1986-2006 (pounds)
Chemical Inventory Update Reporting Cycle
1986
1990
1994
1998
2002
2006
Range of
Production /
Importation
Volume
> 10 million -
50 million
pounds
> 10 million -
50 million
pounds
> 10 million -
50 million
pounds
> 500,000-
1 million
pounds
> 1 million -
10 million
pounds
1 million -
< 10 million
pounds
Source: USEPA, 2008
Exhibit 10-4: CDR Reported Annual Manufacture and Importation of RDX in the
United States, 2011-2015 (pounds)
Chemical Inventory Update Re
porting Cycle
2011
2012
2013
2014
2015
Range of Production /
Importation Volume
6,252,419
1 million -10
million
1 million -10
million
1 million -10
million
1 million -10
million
Source: USEPA, 2018a
Note: 2011 results are reported not as a range, but as an exact value.
10.2.2 Environmental Fate
As discussed in Chapter 2, the measures used by EPA to assess mobility include (where
available) the organic carbon partitioning coefficient (Koc), log octanol-water partitioning
coefficient (log Kow), Henry's Law Constant (Kh), water solubility, and vapor pressure. RDX
released to the atmosphere is likely to exist in the particulate phase, where dry and wet
deposition will remove the particulates from the atmosphere. The Henry's Law Constant of 2.0E-
11 atm-m3/mol for RDX and its water solubility of 59.7 mg/L indicate that volatilization from
moist soil or water surfaces is not likely (ATSDR, 2012; HSDB, 2012). Studies have shown that
RDX is mobile in soil and therefore likely to leach into the groundwater (ATSDR, 2012). The
Koc values of 42 to 167 L/kg also indicate that RDX may adsorb to sediment and is likely to be
highly to moderately mobile in soil (ATSDR, 2012; HSDB, 2012).
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RDX biodegradation is unlikely to occur in aerobic soils (ATSDR, 2012; HSDB, 2012).
However, under anaerobic conditions with supplemental carbon, biodegradation has been
observed (ATSDR, 2012). Hydrolysis is not likely to be an important removal mechanism in
natural waters at a typical environmental pH range (ATSDR, 2012; HSDB, 2012), although
hydrolysis can occur under alkaline conditions. At pH 10, hydrolysis to several degradation
products was observed over 17 days; however, a half-life was not specified (HSDB, 2012).
Photolysis can occur in surface water, with experimental half-lives in distilled water, pond water
and river water samples ranging from 9 to 14 days (HSDB, 2012). The half-life of an aqueous
solution of RDX in natural sunlight is 9 to 13 hrs. A study of dark tea-colored waters showed a
decrease in photolysis, with a half-life of 456 to 2,100 days, due to sunlight not penetrating past
the upper layers of the water column. The half-life in summer was 456 days while that in winter
was 2,100 days (ATSDR, 2012).
Chapter 2 presents scales used by EPA to informally rank chemical contaminants' likely
mobility (understood as their tendency to partition to water rather than other media) and
persistence as "high," "moderate," or "low" based on physical and chemical properties (see
Exhibit 2-2 and Exhibit 2-3). For RDX, a water solubility of 59.7 mg/L indicates a moderate
likelihood of partitioning to water, while a Koc of 42 to 167 L/kg indicates a moderate to high
likelihood of partitioning to water. A logKow of 0.87, and a Kh of 02.0E-11 atm-m3/mol indicate
a high likelihood of partitioning to water.
The BIOWIN (v4.10) module of EPA's Estimation Program Interface (EPI Suite™;
USEPA, 2012a) uses several models to predict biodegradation, including complete degradation
to a primary metabolite and complete degradation to carbon dioxide and water. The predictions
are not half-lives and therefore cannot be directly compared to the Contaminant Candidate List
(CCL) Persistence ranking protocol, although BIOWIN uses the same time frames as the CCL
Persistence protocol. BIOWIN predicts complete degradation of RDX to a primary metabolite in
days-weeks and complete degradation to carbon dioxide and water in weeks-months. Other
models used in BIOWIN indicate that RDX does not degrade fast, suggesting low to moderate
persistence.
10,3 Health Effects
10.3.1 Toxicokinetics
There are data supporting intestinal absorption by humans from accidental ingestion by a
child (ATSDR, 2012). RDX was identified in plasma and cerebrospinal fluid 24 hours after
exposure to an unknown amount of the compound. Urinary excretion peaked at 48 hours and
feces excretion at 96 hours post-exposure (ATSDR, 2012).
Oral absorption in experimental animals ranges from 50 to 90 percent (USEPA, 2018b)
and is influenced by the dosing conditions (form and exposure medium). Absorption is expected
to be greater in rodents than in humans based on data from a study in miniature swine (mini pigs)
and rats (USEPA, 1992; ATSDR, 2012). In experimental animals, post-absorption concentrations
have been detected in the brain, heart, liver, and fat (USEPA, 2018b). Excretion of 14C-RDX-
derived radioactivity in rats following acute-or intermediate-duration exposure is primarily via
exhaled air and urine with small amounts in the feces (ATSDR, 2012).
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10.3.2 Available Health Effect Assessments
Exhibit 10-5 presents a summary of the available health effects assessments for RDX,
The most recent is a 2018 Integrated Risk Information System (IRIS) Toxicological Review.
Older assessments include an Agency for Toxic Substances and Disease Registry (ATSDR)
toxicological profile (ATSDR, 2012) and an Office of Water (OW) assessment published within
the 1992 Drinking Water Health Advisory: Munitions (USEPA, 1992). These assessments are
described below in Exhibit 10-5. As indicated by the bolded row, the 2018 IRIS review (USEPA,
2018b) was selected for use in the calculation of a Health Reference Level (HRL) (see Section
10.3.3 below for details on that calculation).
Exhibit 10-5. Available Health Effects Assessments for RDX
Health
Assessment
Asses
sment
Year
Reference
Dose
(RfD)
(mg/kg/
day)
Principal
study for RfD
Cancer
Slope
Factor
(CSF)
(mg/kg/
day)"1
Principal study
for CSF
Cancer Descriptor
EPA IRIS
2018b
0.004
Crouse et al.
(2006)
0.08
Lish et al. (1984)
Suggestive evidence of
carcinogenic potential
EPAOW
Health
Advisory
(HA)
1992
0.003
Levine et al.
(1983)
0.11
Lish et al. (1984)
Group C (suggestive
evidence of carcinogenic
potential)
ATSDR
2012
0.1
Levine et al.
(1983)/U.S.
Army (1983)
NA
Lish et al. (1984)
Group C (suggestive
evidence of carcinogenic
potential) (cites EPA IRIS)
The USEPA (2018b) IRIS assessment presents a Reference Dose (RfD) of 0.004
mg/kg/day based on convulsions as the critical effect observed in a subchronic study in F-344
rats by Crouse et al. (2006). The benchmark dose level (BMDL) used as the point of departure
(POD) for the calculation was a BMDLo.os of 1.3 mg/kg/day derived using a pharmacokinetic
model that identified the human equivalent dose (HED) using arterial blood concentrations in the
rats as the dose metric. A 300-fold uncertainty factor (3 for extrapolation from animals to
humans, 10 for interindividual differences in human susceptibility, and 10 for uncertainty in the
database) was applied in determination of the RfD.
Additionally, USEPA (2018b) classified data from the Lish et al. (1984) chronic study in
B6C3Fi mice as providing suggestive evidence of carcinogenic potential following the USEPA
(2005) guidelines. The slope factor was derived from the lung and liver tumors' dose-response in
the Lish et al. (1984) study. The POD for the slope factor was the BMDLio allometrically scaled
to a HED yielding a slope factor of 0.08 (mg/kg/day)"1.
USEPA (1992) provides an RfD of 0.003 mg/kg/day based on inflammation of the
prostate in male F344 rats at concentrations of 1.5 mg/kg/day as the critical effect from a 2-year
study by Levine et al. (1983). The no observed adverse effect level (NOAEL) of 0.3 mg/kg/day
was divided by an uncertainty factor of 100 (10 for interspecies extrapolation and 10 for
protection of sensitive human subpopulations) to obtain the RfD. In the more recent EPA
(2018b) IRIS assessment the NOAEL for the prostate effects is given as a BMDLio of 0.23
mg/kg/day but was not used for RfD derivation because of low confidence in the observation
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based the lack of comparable effects in the Lish et al. (1984) mouse study and uncertainties
about the histological prostatitis diagnosis in the rats.
The most recent non-EPA assessment for RDX was conducted by ATSDR (2012).
ATSDR calculated an acute-duration (14 days or less) oral exposure Minimal Risk Level for
RDX of 0.2 mg/kg/day, based on a 14-day study showing impaired neurological function in male
and female Sprague-Dawley rats (Crouse et al., 2006). The Minimum Risk Level was derived by
dividing aNOAELHED of 6.45 mg/kg/day (associated with the pharmacokinetically-modeled,
peak RDX brain concentration associated with the observed tremors and convulsions in the
animals at 14 days) by an uncertainty factor of 30 (3 for the extrapolation of data from animals to
humans, and 10 for human population variability).
ATSDR (2012) also calculated an oral intermediate-duration (15 to 364 days) minimum
risk level based on a 90-day study showing seizures/convulsions in rats from the same
publication (Crouse et al., 2006). The POD for the intermediate duration value was 4.1308
mg/kg/day from the mouse BMDLio peak brain RDX concentration (3.9627 mg/L). The ATSDR
intermediate-duration oral minimum risk level of 0.1 mg/kg/day includes an uncertainty factor of
30 (3 for extrapolation of data from animals to humans, and 10 for human population
variability).
The ATSDR (2012) chronic duration minimum risk level is 0.1 mg/kg/day based on the
2-year study in rats by Levine et al. (1983) with a NOAEL of 8 mg/kg/day and a lowest observed
adverse effect level (LOAEL) of 40 mg/kg/day for tremors and convulsions. Using a
physiologically based pharmacokinetic (PBPK) model, an HED of 4.223 mg/kg/day for tremors
and convulsions was derived.
Health Effects
Case reports identify the central nervous system (CNS) as a target organ in humans after
acute exposure to RDX. Seizures, disorientation, nausea, restlessness, muscle twitching, memory
loss, and lethargy were reported (USEPA, 1992; USEPA, 2018b; USEPA, 2018c). Acute
occupational effects in humans include tremors, and convulsions, plus signs of hepatic and renal
toxicity (USEPA, 1992; USEPA, 2018b). Effects on the nervous system, kidney, bladder, and
prostate were observed in animal studies (USEPA, 2018b). Cancer studies were completed in
both rats and mice. Data on developmental and reproductive effects are somewhat limited. Most
of the early research was completed by the military in the U.S. and other countries (USEPA,
2018b).
Systemic
The median lethal dose (LD50) values (gavage) in rats ranged from 59 to 97 mg/kg, and in
mice they ranged from 71 to 300 mg/kg (USEPA, 1992). Seizures were induced in acute gavage
studies when rats were dosed with 25 or 50 mg/kg/day RDX (ATSDR, 2012), and in miniature
swine dosed with 100 mg/kg (ATSDR, 2012).
Crouse et al. (2006), the critical study selected as the basis for the RfD in EPA's IRIS
assessment (2018b), was conducted in F-344 rats exposed to 0, 4, 8, 10, 12, or 15 mg/kg/day of
RDX in distilled water containing 1 percent methylcellulose and 0.2 percent Tween 80 for 13
weeks. The 4 mg/kg/day was identified as the NOAEL. Multiple adverse effects were observed
at the 8 mg/kg/day LOAEL including early mortality, hepatic, kidney and testicular effects as
had been reported in earlier studies. Hypercholesteremia was also observed.
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In a study by Levine et al. (1983) evaluating the chronic effects of RDX, rats were fed
doses of 0, 0.3, 1.5, 8.0, or 40.0 mg/kg/day for 24 months (ATSDR, 2012). Tremors and
convulsions were frequently observed prior to death in the high-dose males and females
beginning at week 25 (ATSDR, 2012). Histological evaluations did not detect any significant
treatment-related CNS lesions. Hepatoxicity, consisting of hepatomegaly, hypocholesteremia,
hypotriglyceridemia, and reduced serum albumin/total protein levels, were present at the high
dose. There was increased pigment in the spleen and suppurative inflammation of the prostate of
the males at doses of >1.5 mg/kg/day (ATSDR, 2012).
Reproductive and Developmental Toxicity
No information is currently available on the reproductive or developmental toxicity of
RDX in humans (USEPA, 2018b). Increased incidence of testicular degeneration was observed
in a study performed by Lish et al. (1984) in which B6C3Fi mice were fed doses of 0, 1.5, 7.0,
35.0, or 175/1001 mg/kg/day in their diets for 24 months (USEPA, 2018b). However, evidence
of male reproductive toxicity was generally not supported by findings from other studies.
Therefore, USEPA (2018b) concluded that insufficient information was available to evaluate
male reproductive toxicity from experimental animals exposed to RDX.
Developmental effects in rats, including survival, growth, and morphological
development, have only been observed at doses that resulted in severe maternal toxicity and
mortality (USEPA, 2018b). In addition, dose-dependent developmental effects in rabbits have
not been observed. Per EPA's Guidelines for Developmental Toxicity Risk Assessment (USEPA,
1991), "information on developmental effects may be difficult to interpret and of limited value"
when they are observed at doses causing excessive maternal toxicity. USEPA (2018b) therefore
concluded that inadequate information was available to assess developmental effects from
experimental animals exposed to RDX.
Carcinogenicity
No information is currently available on the carcinogenicity of RDX in humans (USEPA,
2018b). There are several studies of the carcinogenic potential of RDX in animals (Hart, 1976,
Levine et al., 1983, Lish et al., 1984) described in USEPA (1992) and USEPA (2018b). The
results were judged to be negative for rats in the Hart (1976) study, but positive for the incidence
of hepatocellular carcinomas in male rats in the Levine et al. (1983) study and positive for the
incidence of hepatocellular adenomas or carcinomas, as well as alveolar/bronchiolar adenomas
or carcinomas in male and female mice in the Lish et al. (1984) study.
In mice fed RDX at doses of 0 to 35 mg/kg/day for 24 months in the Lish et al. (1984)
study, there were dose-dependent increases in adenomas or carcinomas of the lungs and liver in
males and females (USEPA, 1992; USEPA, 2018b). In addition, the formulation of RDX used
contained 3 to 10 percent of octahydro-l,3,5,7-tetranitro-l,3,5,7-tetrazocine (HMX), another
munition ingredient. EPA assessed the toxicity of HMX (USEPA, 1988). No chronic-duration
studies were available to evaluate the carcinogenicity of HMX (USEPA, 1988). HMX is
classified as Group D, or not classifiable as to human carcinogenicity (USEPA, 1992; USEPA,
1988). A reanalysis of the female mouse liver lesion slides by a Pathology Working Group
(Parker et al., 2006; Parker, 2001) downgraded some RDX malignant tumors from the original
analysis to benign status and some adenomas from the original analysis to nonneoplastic lesions
1 The high dose was lowered from 175 to 100 mg/kg/day during week 11 due to high mortality in both sexes.
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(USEPA, 2018b). In the Levine et al. (1983) dietary exposure study with Fischer 344 rats, a
statistically significant increase in the incidence of hepatocellular carcinomas was observed in
males but not in females (USEPA, 2018b). Although evidence of carcinogenicity included dose-
dependent increases in two experimental animal species, two sexes, and two systems (liver and
lungs), evidence supporting carcinogenicity in addition to the B6C3Fi mouse study was not
robust; this factor contributed to the suggestive evidence of carcinogenic potential classification.
EPA considered both the Lish et al. (1984) and Levine et al. (1983) studies to be suitable for
dose-response analysis because they were well conducted, using similar study designs with large
numbers of animals at multiple dose levels (USEPA, 2018b). EPA concluded that insufficient
information was available to evaluate male reproductive toxicity from experimental animals
exposed to RDX (USEPA, 2018b). In addition, EPA concluded that inadequate information was
available to assess developmental effects from experimental animals exposed to RDX (USEPA,
2018b).
Genotoxicity
RDX was evaluated for mutagenicity in Salmonella typhimurium and Saccharomyces
cerevisiae, for deoxyribonucleic acid (DNA) damage in human fibroblasts, and for dominant
lethal mutations in mice and rats. In all cases, it appeared to be nongenotoxic (USEPA, 1992;
USEPA, 2018b). Several minor RDX metabolites of intestinal origin have tested positive in
some genotoxicity assays. However, the USEPA (2018b) assessment did not consider them
strong enough to support a mutagenic mode of action (MOA) for the tumors found in (Lish,
1984).
Carcinogenic Mode of Action (MOA)
The available genotoxicity data are mostly negative, suggesting that RDX does not act
through a mutagenic MOA.
Sensitive Populations
Because the carcinogenic MOA in experimental animals is unknown and the
toxicokinetics and toxicodynamics of RDX are variable between rodents (rats, mice) and
mammals (mini pigs) in the available animal literature, little information is available to
determine whether some subpopulations might be more sensitive to the potential carcinogenic
effects of RDX (USEPA, 2018b).
Limited data are available to evaluate subconvulsive neurological effects and
developmental neurotoxicity (USEPA, 2018b). In particular, the childhood life stage has not
been well-studied in human or animal RDX studies. As described above, developmental effects
in rats were only observed at doses associated with severe maternal toxicity and mortality;
however, maternal transfer of RDX to the fetus and to pups from milk of dams treated with RDX
during gestation has been reported (USEPA, 2018b). Developmental neurotoxicological effects
are a concern because y-amino butyric amino acid (GABA) receptor antagonism is implicated as
the primary MOA for nervous system effects and GABAergic signaling plays a major role in
nervous system development (USEPA, 2018b).
Available data indicate that male rats are more sensitive to RDX-related urinary system
toxicity than female rats and there is suggestive evidence of prostate effects in male rats
following chronic exposure (USEPA, 2018b). Males also appeared to be more sensitive to the
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neurotoxicity endpoints than the females (USEPA, 2018b). Rats were found to be more sensitive
to RDX-related urinary system toxicity than mice (USEPA, 2018b).
10 3,3 Basis of the HRL
EPA selected the 2018 EPA IRIS assessment to derive two HRLs for RDX: the RfD-
derived HRL (based on Crouse et al., 2006) and the oral-slope-factor-derived HRL (based on
Lish et al., 1984). EPA has generally derived HRLs for "possible" or Group C carcinogens using
the RfD approach in past Regulatory Determinations. However, for RDX, EPA decided to show
both an RfD-derived and oral cancer slope factor-derived HRL since the MOA for liver tumors is
unknown and the 1 x 10"6 cancer risk level provides a more health protective HRL to evaluate the
occurrence information.
The RfD-derived HRL for RDX was calculated using the RfD of 0.004 mg/kg/day based
on a subchronic study in F-344 rats by Crouse et al. (2006) with convulsions as the critical effect
(USEPA, 2018b). The POD for the RfD calculation was a human equivalent BMDLo.os of 1.3
mg/kg/day. The HED was derived using a pharmacokinetic model based on arterial blood
concentrations in the rats as the dose metric. A 300-fold uncertainty factor (3 for extrapolation
from animals to humans, 10 for inter-individual differences in human susceptibility, and 10 for
uncertainty in the database) was applied in determination of the RfD.
BW
HRL = RfD* — *RSC
mq/kq 80 kq
RfD-derived HRL = 0.004 * * 20%
day 2 ^
day
RfD-derived HRL = 0.0256 mg/L
RfD-derived HRL = 0.03 mg/L (rounded)
RfD-derived HRL = 30 ug/L
RfD = Reference Dose (mg/kg/day); toxicity value selected based on protocol hierarchy
BW = Body weight (kg); based on adult default value of 80 kg
DWI = Drinking Water Intake (L/day); based on adult default value of 2.5 L/day
RSC = Relative Source Contribution, or the level of exposure believed to result from
drinking water when compared to other sources (e.g., food, ambient air), is 20 percent
when used for HRL derivation.
The oral-cancer-slope-factor-derived HRL for RDX was also based on values presented
in the 2018 EPA IRIS assessment. The slope factor is derived from the dose-response for lung
and liver tumors in the Lish et al. (1984) study, with elimination of the data for the high dose
group due to high mortality. The POD for the slope factor of 0.08 (mg/kg/day)"1 was the
BMDLio, which was allometrically scaled to an HED.
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0.000001 80 kg
Oral cancer slope factor-derived HRL = 7 * — = 0.0004 mq/L
- z-5^
Oral cancer slope factor-derived HRL = 0.4 ug/L
EPA's (USEPA, 2018b) derivation of an oral slope factor for cancer for RDX is in
accordance with the Guidelines for Carcinogen Risk Assessment (USEPA, 2005) as they apply to
contaminants with "suggestive evidence of carcinogenic potential." Specifically, the guidelines
state "when the evidence includes a well-conducted study, quantitative analyses may be useful
for some purposes, for example, providing a sense of the magnitude and uncertainty of potential
risks, ranking potential hazards, or setting research priorities" (USEPA, 2005). The EPA IRIS
assessment concluded that the database for RDX contains well-conducted carcinogenicity studies
(Lish et al., 1984; Levine et al., 1983) suitable for dose response and that the quantitative
analysis may be useful for providing a sense of the magnitude and uncertainty of potential
carcinogenic risk (USEPA, 2018b). Therefore, EPA evaluated the occurrence information
against both the RfD-derived HRL and the oral cancer slope factor-derived HRL (assuming the
MOA for the tumors is linear) to provide the most information on the potential risk of exposure
to RDX in drinking water.
10.3.4 Data Base Limitations
The core data base for RDX includes studies of acute, subchronic and chronic studies as
well as considerable occupational data for humans. The available data are limited as they relate
to reproductive, developmental, neurotoxic, and subconvulsive neurological effects, as well as to
the MOA for the neurotoxicity observed in humans and animals, and the tumors in rats and mice
(USEPA, 2018b). In addition, limited data are available on how differences in formulation and
particle size might affect RDX absorption and subsequent toxicity, as well as on how the oral
dosing method used in a study might influence the results (USEPA, 2018b).
10.3.5 Health Effects Data Gaps
Data on developmental neurotoxicity, on subconvulsive neurological effects, and on the
effects of cumulative exposures on incidence of neurotoxic effects would help to further
characterize the neurotoxicity hazard (USEPA, 2018b). Studies evaluating how differences in
formulation and particle size might affect RDX absorption and subsequent toxicity, as well as on
how the oral dosing method used in a study might influence the results would also be valuable in
increasing confidence in the RDX data base (USEPA, 2018b).
MOA studies for the neurological convulsions and tremors as well as for the tumors
would be valuable contributions to the RDX database. USEPA (2018b) suggests that GAB A may
play a role in the MOA for the neurological symptoms reported for humans but mechanistic data
to support the hypothesis appear to be minimal.
10.4 Occurrence
This section presents data on the occurrence of RDX in ambient water and drinking water
in the United States. As described in section 10.3, two HRLs were calculated for RDX: an HRL
of 30 |ig/L based on non-carcinogenic effects and an HRL of 0.4 |ig/L based on carcinogenicity.
HRLs are risk-derived concentrations against which EPA evaluates the occurrence data to
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determine if contaminants occur at levels of potential public health concern. Occurrence data
from various sources presented below are analyzed with respect to each of the HRLs and one-
half the HRLs. When possible, estimates of the population exposed at concentrations above the
HRLs and above one-half the HRLs are presented.
For additional background information about data sources used to evaluate occurrence,
please refer to Chapter 2.
10.4.1 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the ambient sources of most drinking water. Contaminant
occurrence in ambient water provides information on the potential for contaminants to adversely
affect drinking water supplies. Occurrence data for RDX in ambient water are not available from
the United States Geological Survey (USGS) National Water-Quality Assessment (NAWQA);
however, non-NAWQA data are available from the USGS National Water Information System
(NWIS) database. EPA's legacy Storage and Retrieval Data System (STORET) data available
through the Water Quality Portal (WQP) also include ambient water occurrence data for RDX.
National Water Information System (NWIS) Data
NWIS is the Nation's principal repository of water resources data USGS collects from
more than 1.5 million sites (USGS, 2016). NWIS-Web is the general online interface to the
USGS NWIS database. Discrete water-sample and time-series data are available from sites in all
50 States, including 5 million water samples with 90 million water-quality results. All USGS
water quality and flow data are stored in NWIS, including site characteristics, streamflow,
groundwater level, precipitation, and chemical analyses of water, sediment, and biological
media, though not all parameters are available for every site. NWIS houses the NAWQA data
and includes other USGS data from unspecified projects. NWIS contains many more samples at
many more sites than the NAWQA Program and, although NWIS is comprised of primarily
ambient water data, some finished drinking water data are included, as well. This section
presents analyses of non-NAWQA data in NWIS, downloaded from the WQP in December 2017
(WQP, 2017).
The results of the non-NAWQA NWIS RDX analyses are presented in Exhibit 10-6.
RDX was detected in approximately 46 percent of samples (517 out of 1,115 samples) and at
approximately 29 percent of sites (43 out of 147 sites). The median concentration based on
detections was 26.0 |ig/L. (Note that the NWIS data are presented as downloaded; potential
outliers were not evaluated or excluded from the analysis.)
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Exhibit 10-6: RDX NWIS Data, 1991 - 2016
System Type
Detection Frequency
(detections are results > reporting level)
Concentration Values
(of detections, in |jg/L)
No. of
Samples
No. of
Samples
with
Detections
No.
of
Sites1
No. of
Sites with
Detections
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Groundwater
1,063
509
132
41
0
27.0
61.1
119
310
Surface Water
52
8
22
4
0
0.230
116
138
140
All Sites
1,115
517
147
43
0
26.0
62.0
120
310
Source: WQP, 2017
1 The number of groundwater sites plus the number of surface water sites and finished water sites is not equal to "All
Sites" because some sites may have been listed with more than one source water type in the data.
Storage and Retrieval Data System (STORET) / Water Quality Portal (WQP)
From its launch in 1999 until it was decommissioned in June 2018, EPA's STORET Data
Warehouse was collaboratively populated with raw biological, chemical, and physical data from
surface water and groundwater sampling by federal, state and local agencies, Native American
tribes, volunteer groups, academics, and others. Legacy STORET data are accessible through the
WQP: https://www.waterqualitvdata.us/portal/.
STORET data are from monitoring locations in all 50 states as well as multiple territories
and jurisdictions of the United States. Most data are from ambient waters, but in some cases
finished drinking water data are included as well. STORET's data quality limitations include
variations in the extent of national coverage and data completeness from parameter to parameter.
Data may have been collected as part of targeted, rather than randomized, monitoring.
This section presents analyses of STORET data, downloaded from the WQP in December
2017 (WQP, 2017). EPA reviewed STORET groundwater data from wells and surface water data
from lakes, rivers/streams, and reservoirs (WQP, 2017). The results of the STORET analysis for
RDX are presented in Exhibit 10-7 through Exhibit 10-9. These RDX samples were collected
between 1982 and 2016. Of the 78 sites sampled, 44 (56.40 percent) reported detections of RDX.
Detected concentrations ranged from 0.2 |ig/L to 270 |ig/L. The 90th percentile concentration of
detections was equal to 220 |ig/L. The minimum detected concentration may be indicative of the
reporting levels used.
Exhibit 10-7: RDX STORET Data - Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
Maximum
Groundwater
0.2
38
160
210
Surface Water
0.487
140
225
270
Total
0.2
140
220
270
Source: WQP, 2017
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Exhibit 10-8: RDX STORET Data - Summary of Samples and Sites
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Total
Number
of Sites
Sites with Detections
Number
Percent
Number
Percent
Groundwater
173
83
47.98%
24
13
54.17%
Surface Water
1,265
1,200
94.86%
54
31
57.41%
Total
1,438
1,283
89.20%
78
44
56.40%
Source: WQP, 2017
Exhibit 10-9: RDX STORET Data - Summary of States
Source Water
Type
Total
Number of
States
States with Detections
Number
Percent
Groundwater
2
2
100.00%
Surface Water
3
3
100.00%
Total1
4
4
100.00%
Source: WQP, 2017
1 The number of states with groundwater data plus the number of
states with surface water data may not equal the "Total" number of
states providing data because some states provided both groundwater
and surface water data.
10.4.2 Occurrence in Drinking Water
Data sources reviewed by the Agency for information on contaminant occurrence in
drinking water included: EPA's first, second, and third Unregulated Contaminant Monitoring
Rules (UCMR 1, UCMR 2, UCMR 3); Rounds 1 and 2 of the Agency's Unregulated
Contaminant Monitoring (UCM) program that preceded the Unregulated Contaminant
Monitoring Rule (UCMR); EPA's Information Collection Rule; EPA's National Inorganics and
Radionuclides Survey (NIRS); and a range of others as discussed in Chapter 2. Among the
sources reviewed, the following had data and information on RDX occurrence in drinking water.
These data and information are discussed in this section.
EPA's Second Unregulated Contaminant Monitoring Rule (UCMR 2).
State drinking water monitoring programs.
Note that there may be some overlap, as sources with different purposes and audiences
may have reported the same underlying data. UCMR 2 is a national data source. Other data
sources profiled in this section are considered "supplemental" sources.
Primary Data Sources
Second Unregulated Contaminant Monitoring Rule (UCMR 2), 2008-2010
UCMR 2 monitoring was conducted from 2008 to 2010 and was designed to provide
nationally representative contaminant occurrence data. UCMR 2 required surface water systems
to monitor quarterly and groundwater systems to monitor semi-annually. There were two tiers of
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monitoring: Assessment Monitoring for contaminants with commonly used analytical method
technologies, and Screening Survey monitoring for contaminants that require specialized
analytical method technologies not in wide or common use at the time of the study.
All public water systems (PWSs) serving more than 10,000 people, plus a statistically
representative national sample of 800 PWSs serving 10,000 people or fewer, were required to
conduct Assessment Monitoring during a 12-month period between January 2008 and December
2010. For the Screening Survey, monitoring was required by all very large PWSs, and small
PWSs, during a 12-month period between January 2008 and December 2010. For RDX 320
systems are representative of large PWSs, and 480 are representative of small PWSs. See
USEPA (2007) and USEPA (2014b) for more information on the UCMR 2 program, including
study design and data analysis.
The design of UCMR 2 permits estimation of national occurrence. To calculate national
extrapolations, the percent of systems (or population served) estimated to exceed a specified
threshold in a given category can be multiplied by the total number of systems (or population
served) in the nation in that category. In UCMR 2 analysis, the extrapolation methodology is
applied only to small systems. Because all systems serving more than 10,000 people were
required to participate in the UCMR 2 Assessment Monitoring, national estimates of occurrence
in this size category do not require extrapolation. Rather, survey census figures are used. Total
national occurrence is estimated by summing the extrapolated or census figures from all three
size categories. See Chapter 2 for additional information on national extrapolations.
RDX was monitored under the UCMR 2 Assessment Monitoring. Monitoring results are
presented in Exhibit 10-10 through Exhibit 10-12. The minimum reporting level (MRL) used for
RDX was 1 |ig/L (72 FR 367; USEPA, 2007). A total of 32,150 finished water RDX samples
were collected from 4,139 systems. There were no detections greater than the non-cancer HRL
(30 |ig/L) or the one-half the non-cancer HRL (15 |ig/L). Four samples (0.01 percent) had
detections of RDX at or above the MRL of 1 |ig/L. The detections occurred in three large surface
water systems. The highest detected concentration of RDX was 1.1 |ig/L and the median value
was also 1.1 |ig/L. Nationally, RDX would be expected to exceed the MRL at an estimated 3
PWSs serving approximately 96,000 people. Because the MRL of 1 |ig/L is higher than the
cancer HRL of 0.4 |ig/L, occurrence relative to the cancer HRL and '/2 the cancer HRL is not
presented in these tables.
Exhibit 10-10: RDX Occurrence Data from UCMR 2 Assessment Monitoring -
Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (in |jg/L) > MRL of 1 (jg/L
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Small Systems (serving < 10,000 people)
Groundwater
ND
ND
ND
ND
ND
Surface Water
ND
ND
ND
ND
ND
All Small Systems
ND
ND
ND
ND
ND
Large Systems (serving 10,001 -100,000 people) — CENSUS
Groundwater
ND
ND
ND
ND
ND
Surface Water
1
1.07
1.1
1.1
1.1
All Large Systems
1
1.07
1.1
1.1
1.1
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Source Water Type
Concentration Value of Detections (in |jg/L) > MRL of 1 (jg/L
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Very Large Systems (serving > 100,000 people) — CENSUS
Groundwater
ND
ND
ND
ND
ND
Surface Water
ND
ND
ND
ND
ND
All Very Large
Systems
ND
ND
ND
ND
ND
All Systems
All Water Systems
1
1.07
1.1
1.1
1.1
Source: USEPA, 2012b
ND = no detections in this category
Exhibit 10-11: RDX National Occurrence Measures Based on UCMR 2 Assessment
Monitoring Data - Summary of Samples
Source Water Type
Total
Number of
Samples
Samples with
Detections
> MRL (1 |jg/L)
Number
Percent
Small Systems (serving < 10,000 people)
Groundwater
2,332
0
0.00%
Surface Water
919
0
0.00%
All Small Systems
3,251
0
0.00%
Large Systems (serving 10,001 -100,000 people) — CENSUS
Groundwater
11,760
0
0.00%
Surface Water
10,327
4
0.04%
All Large Systems
22,087
4
0.02%
Very Large Systems (serving > 100,000 people) — CENSUS
Groundwater
2,012
0
0.00%
Surface Water
4,800
0
0.00%
All Very Large Systems
6,812
0
0.00%
All Systems
All Water Systems
32,150
4
0.01%
Source: USEPA, 2012b
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Exhibit 10-12: RDX National Occurrence Measures Based on UCMR 2 Assessment Monitoring Data - Summary of
System and Population Served Data - All Detections
Source Water
Type
UCMR 2 Sample
Number With At Least One
Detection > MRL (1 |jg/L)
Percent With At Least One
Detection > MRL (1 |jg/L)
National Inventory
National Estimate1
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Groundwater
618
1,790,743
0
0
0.00%
0.00%
57,818
37,685,557
0
0
Surface Water
182
878,262
0
0
0.00%
0.00%
3,866
8,928,745
0
0
All Small
Systems
800
2,669,004
0
0
0.00%
0.00%
61,684
46,614,302
0
0
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
1,373
34,816,693
0
0
0.00%
0.00%
1,373
34,816,693
0
0
Surface Water
1,568
49,758,358
3
96,033
0.19%
0.19%
1,566
49,758,358
3
96,000
All Large
Systems
2,941
84,575,051
3
96,033
0.10%
0.11%
2,941
84,575,051
3
96,000
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
63
17,269,919
0
0
0.00%
0.00%
63
17,269,919
0
0
Surface Water
335
124,711,765
0
0
0.00%
0.00%
335
124,711,765
0
0
All Very Large
Systems
398
141,981,684
0
0
0.00%
0.00%
398
141,981,684
0
0
All Systems
All Water
Systems
4,139
229,225,740
3
96,033
0.07%
0.04%
65,023
273,171,037
3
96,000
Source: USEPA, 2012b
1 National estimates for the small systems are extrapolations, generated by multiplying the UCMR 2 national statistical sample findings of system/population
percentages and national system/population inventory numbers for PWSs developed from EPA's Safe Drinking Water Information System (SDWIS), the Community
Water System Survey (CWSS), and UCMR (see Chapter 2 for discussion). National estimates for the large and very large systems are based directly on the UCMR 2
results, since this was a census, i.e., all large and very large systems were required to conduct UCMR 2 Assessment Monitoring. Due to rounding, some calculations
may appear to be slightly off.
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Supplemental Data Sources
State Monitoring Data, 2006-2011
Because there is no available national database that receives and stores all relevant data
regarding the occurrence of regulated contaminants in public drinking water systems, EPA
conducts voluntary data requests from the states, territories, and tribes in support of national
occurrence assessments. These assessments are part of the Six-Year Review. Under the second
and third Six-Year Review (SYR2 and SYR3), a few states submitted PWS occurrence data for
unregulated contaminants along with the requested data on regulated contaminants. EPA was
able to supplement the data on unregulated contaminants by downloading additional publicly
available monitoring data from state websites. For SYR2, the result was a collection of
unregulated contaminant monitoring data from nine states and other entities, such as tribes,
territories, and EPA Regions. For SYR3, the dataset of unregulated contaminant monitoring data
included results from 14 states/entities. For both rounds of the Six-Year Review, these
unregulated data provide varying degrees of completeness in their coverage of the states/entities
and are not necessarily representative of occurrence in those states/entities. For more details on
the Six-Year Review Information Collection Request (ICR) Dataset for SYR2, refer to USEPA
(2009). For more details on the SYR3 ICR Dataset, refer to EPA's SYR3 occurrence analysis
(USEPA, 2016).
Drinking water occurrence data for RDX were available from California under the SYR3
(2006-2011). (No RDX data were submitted under SYR2.) As noted above, the monitoring data
are limited and not necessarily representative of occurrence in California. A total of 363 samples
(198 finished water samples and 165 raw water samples) from 45 systems were included for
RDX. RDX was not detected in any of the water samples. Additional drinking water occurrence
data for RDX were available online from California for the years 2014 through 2018. A total of 9
samples (8 raw water samples and 1 finished water sample) from 3 systems were included for
RDX. RDX was not detected in any of the water samples. Comprehensive information about
methods used and reporting levels is not available for this data set.
10.5 Analytical Methods
EPA has published one analytical method for the analysis of RDX in drinking water:
• EPA Method 529, Revision 1.0, Determination of Explosives and Related
Compounds in Drinking Water by Solid Phase Extraction and Capillary Column Gas
Chromatography/Mass Spectrometry (GC/MS). The Lowest Concentration Minimum
Reporting Levels (LCMRLs), although not included in EPA Method 529, range from
0.16 to 1.34 |ig/L. Recoveries in reagent water, chlorinated tap water from a surface
water source and chlorinated tap water from a groundwater source with high hardness
range from 93.1 to 131%, with Relative Standard Deviations (RSDs) of 2.5 to 11%
using Program Temperature Vaporizing (PTV) splitless injection and Full Scan mode.
Recoveries in reagent water, chlorinated tap water from a surface water source and
chlorinated tap water from a groundwater source with high hardness range from 85.2
to 133%, with RSDs of 1.3-8.9%) using PTV splitless injection and Selected Ion
Monitoring (SIM) mode. Recoveries in reagent water, chlorinated tap water from a
surface water source and chlorinated tap water from a groundwater source with high
hardness range from 99.3 to 150%), with RSDs of 1.6 to 13%> using on-column PTV
injection and Full Scan mode (USEPA, 2002).
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Laboratories participating in UCMR 2 were required to use EPA Method 529 and, as
noted in Section 10.4.2, were required to report RDX values at or above the EPA-defined MRL
of 1 |.ig/L (72 FR 367; USEPA, 2007). The MRL was set based on the capability of multiple
laboratories at the time.
10.6 Treatment Technologies
EPA evaluates whether suitable treatment technologies are available prior to
promulgating a final National Primary Drinking Water Regulation (NPDWR).
EPA's Drinking Water Treatability Database (USEPA, 2020) summarizes available
technical literature on the efficacy of treatment technologies for a range of priority drinking
water contaminants. The database states that granular activated carbon (GAC) is the most
commonly used technology for removal of RDX from contaminated groundwater, and that
additional technologies that are considered effective include chemical oxidation, alkaline
hydrolysis, electrochemical reduction, and ultraviolet (UV) irradiation. Ozonation and hydrogen
peroxide oxidation are not generally considered effective. The exact percentage removal a water
system may achieve with a given technology will be dependent upon a variety of factors,
including source water quality and water system characteristics.
10.7 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2012. Toxicological Profile for
RDX. U.S. Department of Health and Human Services, Public Health Service. Available
on the Internet at: http://www.atsdr.cdc.gov/ToxProfiles/tp.asp?id=412&tid=72.
ChemlDPlus. 2018. Available on the Internet at: http://chem.sis.nlm.nih.gov/chemidplus/.
Accessed December 7, 2018.
Crouse, L.C.B., M.W. Michie, M. Major, M.S. Johnson, R.B. Lee, and H.I. Paulus. 2006.
Subchronic oral toxicity of RDX in rats. (Toxicology Study No. 85-XC-5131-03).
Aberdeen Proving Ground, MD: U.S. Army Center for Health Promotion and Preventive
Medicine.
Hart, E.R. 1976. Two-year feeding study in rats. Litton Bionetics, Inc., Kensington, MD. Office
of Naval Research, Contract No. N00014-73-C-0162. (As cited in USEPA, 2018a.)
Hazardous Substances Data Bank (HSDB). 2012. Profile for Cyclonite. Available on the Internet
at: http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen7HSDB. Last revision date: April 26,
2012.
Levine, B.S., P.M. Lish, E.M. Furedi, V.S. Rac, and J.M. Sagartz. 1983. Determination of the
chronic mammalian toxicological effects of RDX (twenty-four-month, chronic
toxicity/carcinogenicity study of hexahydro-l,3,5-trinitro-l,3,5-triazine (RDX) in the
Fischer 344 rat): Final report—phase V. Chicago, IL: IIT Research Institute. (As cited in
ATSDR, 2012; USEPA, 2018a; USEPA, 1992.)
Lish, P.M., B.S. Levine, E.M. Furedi, J.M. Sagartz, and V.S. Rac. 1984. Determination of the
chronic mammalian toxicological effects of RDX: twenty-four-month, chronic
toxicity/carcinogenicity study of hexahydro-l,3,5-trinitro-l,3,5-triazine (RDX) in the
B6C3F1 hybrid mouse (Volumesl-3). (ADA181766. DAMD17-79-C-9161). Fort
Detrick. (As cited in ATSDR, 2012; USEPA, 2018a; USEPA, 1992.)
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Parker, G. 2001. Attachment 1: Pathology Working Group. Chairperson's report. Reevaluation:
twenty-four-month chronic toxicity/carcinogenicity study of hexahydro-1,3,5-trinitro-
1,3.5-triazine (RDX) in the B6C3F1 hybrid mouse. (As cited in USEPA, 2018a.)
Parker, G.A., G. Reddy, and M.A. Major. 2006. Reevaluation of a twenty-four-month chronic
toxicity/carcinogenicity study of hexahydro-l,3,5-trinitro-l,3,5-triazine (RDX) in the
B6C3F1 hybrid mouse. Int J Toxicol 25: 373-378. (As cited in USEPA, 2018a.
Speth, T.F., M.L. Magnuson, C.A. Kelty, and C.J. Parrett. 2001. Treatment Studies ofCCL
Contaminants. In: Proceedings, AWWA Water Quality Technology Conference,
November 11-15, Nashville, TN.
U.S. Army. 1983. Determination of the chronic mammalian toxicological effects of RDX:
Twenty-four month chronic toxicity/carcinogenicity study of hexahydro-1,3,5-trinitro-
1,3,5-triazine (RDX) in the Fischer 344 rat: Phase V. Vol. 1. Frederick, MD: U.S. Army
Medical Research and Development Command. ADA160774. (author: Levine, B.S. et
al.) (As cited in AT SDR, 2012.)
United States Environmental Protection Agency (USEPA). 1988. Chemical Assessment
Summary Information for Octahydro-l,3,5,7-tetranitro-l,3,5,7-tetrazocine (HMX) on the
Integrated Risk Information System (IRIS). National Center for Environmental
Assessment, Washington, DC. Available on the Internet at:
https://cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm7substance nmbr=311.
USEPA. 1991. Guidelines for Developmental Toxicity Risk Assessment. (EPA/600/FR-91/001).
U.S. Environmental Protection Agency Risk Assessment Forum. Available on the
Internet at: https://www.epa.gov/sites/production/files/2014-ll/documents/dev tox.pdf.
Accessed August 1, 2019.
USEPA. 1992. Health Advisory for Hexahydro-l,3,5-trinitro-l,3,5-triazine (RDX). In Roberts,
WC and WR Hartley eds. Drinking Water Health Advisory Munitions. Lewis Publishers.
Boca Raton FL. pp 133-180.
USEPA. 2002. Method 529. Determination of Explosives and Related Compounds in Drinking
Water by Solid Phase Extraction and Capillary Column Gas Chromatography/Mass
Spectrometry (GC/MS). Revision 1.0. National Exposure Research Laboratory, Office of
Research and Development. EPA 600-R-05-052.
USEPA. 2005. Guidelines for carcinogen risk assessment [EPA Report] (pp. 1-166).
(EPA/630/P-03/001F). Washington, DC: U.S. Environmental Protection Agency, Risk
Assessment Forum. Available on the Internet at: http://www2.epa.gov/osa/guidelines-
carcinogen-ri sk-assessment.
USEPA. 2007. Unregulated Contaminant Monitoring Regulation (UCMR) for Public Water
Systems Revisions. Federal Register 72(2): 367, January 4, 2007.
USEPA. 2008. Using the 2006 Inventory Update Reporting (IUR) Public Data: Background
Document. Office of Pollution Prevention and Toxics. December. Available on the
Internet at:
https://www.epa.gov/sites/production/files/documents/iurdbbackground O.pdf.
USEPA. 2009. The Analysis of Regulated Contaminant Occurrence Data from Public Water
Systems in Support of the Second Six-Year Review of National Primary Drinking Water
Regulations. EPA-815-B-09-006. October 2009.
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USEPA. 2012a. Estimation Program Interface (EPI Suite™) Program Modification & New
Features in v4.11 (November 2012). Available at:
https://19ianuarv2017snapshot.epa.gov/tsca-screening-tools/estimation-program-
interface-epi-suite-tm-program-modifications-new-features .html.
USEPA. 2012b. Second Unregulated Contaminant Monitoring Rule Dataset. Available on the
Internet at: https://www.epa.gov/dwucmr/occurrence-data-unregulated-contaminant-
monitoring-rule#2. Accessed January 2012.
USEPA. 2014a. Chemical Data Reporting. Fact Sheet: Basic Information. June. EPA
Publication 740-K-13-001.
USEPA. 2014b. Occurrence Data from the Second Unregulated Contaminant Monitoring
Regulation (UCMR 2). EPA 815-R14-004. April 2014.
USEPA. 2016. The Analysis of Regulated Contaminant Occurrence Data from Public Water
Systems in Support of the Third Six-Year Review of National Primary Drinking Water
Regulations: Chemical Phase Rules and Radionuclides Rules. EPA 810-R-16-014.
December 2016.
USEPA. 2017. TRI Explorer: Trends. Available on the Internet at:
https://enviro.epa.gov/triexplorer/tri release.trends. Accessed November 2017.
USEPA. 2018a. CDR Reporting Requirements. Available on the Internet at:
https://www.epa.gov/chemical-data-reporting/how-report-under-chemical-data-reporting.
Accessed December 2018.
USEPA. 2018b. Integrated Risk Information System (IRIS). Toxicological Review of
Hexahydro-l,3,5-trinitro-l,3,5-triazine (RDX). Toxicological Review. Available on the
Internet at:
https://cfpub.epa.gov/ncea/iris/iris documents/documents/toxreviews/0313tr.pdf.
Accessed August 1, 2019.
USEPA. 2018c. Integrated Risk Information System (IRIS). Toxicological Review of
Hexahydro-l,3,5-trinitro-l,3,5-triazine (RDX). Supplemental Information. Available on
the Internet at: http://ofmpub.epa.gov/eims/eimscomm.getfile7p download id=536868.
Accessed August 1, 2019.
USEPA. 2019. CompTox Chemicals Dashboard, Searched by DSSTox Substance Id =
DTXSID9024142. Available on the Internet at:
https://comptox.epa. gov/dashboard/dsstoxdb/results?search=DTXSID9024142.
USEPA. 2020. Drinking Water Treatability Database.
https://iaspub.epa.gov/tdb/pages/general/home.do. Last updated March 2020.
United States Geological Survey (USGS). 2016. National Water Information System (NWIS)
Water-Quality Web Services. Available on the Internet at:
https://waterdata.usgs.gov/nwis. Last modified December 2016.
Water Quality Portal (WQP). 2017. Water Quality Portal Data Warehouse. Available on the
Internet at: https://www.waterqualitvdata.us/. Data Warehouse consulted December 2017.
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Appendix A:
Additional Information on Contaminants on the
CCL Not Receiving a Regulatory Determination as
Part of Regulatory Determination 4
An appendix from:
Final Regulatory Determination 4 Support Document
EPA Report 815-R-21-001
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Contaminant
Background
Release and Production Data
Health Effect Findings
1,1,1,2-T etrachloroethane
• CASRN = 630-20-6
• Substance Key = 9105
• HRL = 1 (j.g/L
Background
• A halogenated alkane
• Used as a solvent and chemical intermediate [HSDB, 2008a]
TRI-Release 2016 [USEPA, 2017a]
• Surface water = 66 lbs/yr (1 state)
• Total = 5,255 lbs/yr (5 states)
TRI-Release 2012 [USEPA, 2017a]
• Surface water = 5 lbs/yr (1 state)
• Total = 5,808 lbs/yr (6 states)
TRI-Release 2008 [USEPA, 2017a]
• Surface water = 0 lbs/yr (0 state)
• Total = 2,904 lbs/yr (4 states)
TRI-Release 2004 [USEPA, 2017a]
• Surface water = 36 lbs/yr (2 state)
• Total = 12,088 lbs/yr (7 states)
CDR Production Data (2012 - 2014) [USEPA,
2018a]
• None
Critical Health Endpoint
• Hepatocellular adenoma or carcinoma [NTP, 1983]
• CSF = 0.026 (mg/kg/day)-l
• Cancer HRL = 1.23 (jg/L (1 jig/L rounded to one
sig. fig.)
Health Assessment Status
•USEPA (1989)
• Possible human carcinogen, group C (1986 cancer
guidelines)
Fate / Transport
• Expected to volatilize from water [HSDB, 2008a]
• Expected to have low to high mobility, depending on the
parameter used to estimate mobility [HSDB, 2008a; RD4SD
chapter 2]
• Data for 1,1,2,2-tetrachloroethane suggest that 1,1,1,2-
tetrachloroethane may be of moderate to high persistence in the
environment [HSDB, 2008a; RD4SD chapter 2]
Sensitive Populations/Lifestages
• None identified
Acephate
•CASRN = 30560-19-1
• Substance Key = 31325
• HRL = 0.4 ng/L
Background
• An organophosphate pesticide
• Used as an insecticide [HSDB, 2007]
TRI-Release 2016 [USEPA, 2017a]
• Surface water = 0 lbs/yr (0 state)
• Total = 27,210 lbs/yr (3 states)
TRI-Release 2012 [USEPA, 2017a]
• Surface water = 0 lbs/yr (0 state)
• Total = 4,359 lbs/yr (1 states)
TRI-Release 2008 [USEPA, 2017a]
• Surface water = 0 lbs/yr (0 state)
• Total = 1,919 lbs/yr (3 states)
TRI-Release 2004 [USEPA, 2017a]
• Surface water = 0 lbs/yr (0 state)
• Total = 20,789 lbs/yr (5 states)
CDR Production Data (2012 - 2014) [USEPA,
2018a]
• <25K lbs/yr (2012)
• 100K- 500K lbs/yr (2013, 2014)
Critical Health Endpoint
• Brain Cholinesterase inhibition in male pups
[Hoberman, 2003]
• RfD = 0.0003 mg/kg/day
• Non-cancer HRL = 0.4 jig/L
Health Assessment Status
•USEPA (2018b)
• Possible human carcinogen, group C (1986 cancer
guidelines)
Fate / Transport
• Not expected to volatilize from water [HSDB, 2007]
• Expected to have high mobility [HSDB, 2007; RD4SD chapter 2]
• Expected to be of low persistence in the environment [HSDB,
2007; RD4SD chapter 2]
Sensitive Populations/Lifestages
•Bottle-fed infants
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Contaminant
Background
Release and Production Data
Health Effect Findings
alpha-
Hexachlorocyclohexane
•CASRN = 319-84-6
• Substance Key = 6535
• HRL = 0.005 ng/L
Background
• A halogenated cycloalkane
• A component of benzenehexachloride (BHC), a former pesticide
[HSDB, 2017a], Note: BHC is not synonymous with
hexachlorobenzene. BHC refers to a group of hexachlorinated
cyclohexanes; alpha-l,2,3,4,5,6-hexachlorcyclohexane is a
conformational isomer of BHC
TRI-Release 2006
• Surface water = 0 lbs/yr (0 states)
• Total = 11 lbs/yr (1 state)
CDR Production Data (2012 - 2014) [USEPA,
2018a]
• None
Critical Health Endpoint
• Hepatic nodules and hepatocellular carcinomas [Ito
etal, 1973]
• CSF = 6.3 (mg/kg/day)-l
• Cancer HRL = 0.00508 (jg/L (0.005 jig/L rounded
to one sig. fig.)
Health Assessment Status
•USEPA (1987)
• Probable human carcinogen, group B2 (1986 cancer
guidelines)
Fate / Transport
• Expected to volatilize from water [HSDB, 2017a]
• Expected to have low to moderate mobility [HSDB, 2017a;
ATSDR, 2005; RD4SD chapter 2]
• Expected to be of high persistence in the environment; however,
at pH >9, hydrolysis may result in low to moderate persistence
[HSDB, 2017a; ATSDR, 2005; RD4SD chapter 21
Sensitive Populations/Lifestages
• None identified
Aniline
• CASRN = 62-53-3
• Substance Key = 2438
• HRL = 6 ng/L
Background
• An aromatic amine
• Used as an industrial chemical, as a solvent, in the synthesis of
explosives and pharmaceuticals, in rubber products, and in dyes,
resins, varnishes and perfumes [HSDB, 2018]
TRI-Release 2016 [USEPA, 2017a]
• Surface water = 813 lbs/yr (4 state)
• Total = 2,090,647 lbs/yr (19 states)
TRI-Release 2012 [USEPA, 2017a]
• Surface water = 4,733 lbs/yr (6 state)
• Total = 1,731,280 lbs/yr (17 states)
TRI-Release 2008 [USEPA, 2017a]
• Surface water = 6,525 lbs/yr (7 state)
• Total = 1,034,534 lbs/yr (15 states)
TRI-Release 2004 [USEPA, 2017a]
• Surface water = 1,903 lbs/yr (7 state)
• Total = 958,298 lbs/yr (20 states)
CDR Production Data (2012 - 2014) [USEPA,
2018a]
• IB - 5B lbs/yr (2012, 2013, 2014)
Critical Health Endpoint
• Spleen, combined fibrosarcoma, stromal sarcoma,
capsular sarcoma and hemangiosarcoma [CUT, 1982]
• CSF = 0.0057 (mg/kg/day)-l
• Cancer HRL = 5.6 jig/L (6 (jg/L rounded to one sig.
fig-)
Non-Cancer Health Effect
• Hematological and splenic effects [CUT, 1982]
• RfD = 0.007 mg/kg/day
Health Assessment Status
• USEPA (1988) (cancer)
• Probable human carcinogen, group B2 (1986 cancer
guidelines)
• USEPA (2007) (non-cancer)
Fate / Transport
• Neutral species is expected to volatilize from water; however, it
will exist partially in cationic form at typical environmental pH and
ionic species are not volatile [HSDB, 2018]
• Expected to have moderate to high mobility [HSDB, 2018;
RD4SD chapter 2]
• Expected to be of low persistence in the environment [HSDB,
2018; RD4SD chapter 2]
Sensitive Populations/Lifestages
• None identified
A-l
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EPA - OGWDW
Final Regulatory Determination 4 Support Document - Appendix A. Additional Information, Part 1: Chemical Contaminants
January 2021
Contaminant
Background
Release and Production Data
Health Effect Findings
Cobalt
• CASRN = 7440-48-4
• Substance Key = 18870
• HRL = 2 ng/L
Background
• A naturally-occurring element
• Elemental cobalt is commonly used in alloys and superalloys, as a
catalyst in the petrochemical industry, and in the manufacture of
plastics [HSDB, 2017b]
• Cobalt compounds are commonly used as pigments in paints,
enamels, and glazes, in glass and pottery manufacture, and in the
manufacture of carbon nanotubes [HSDB, 2017c]
TRI-Release 2016 [USEPA, 2017a]
• Surface water = 967 lbs/yr (19 state)
• Total = 240,283 lbs/yr (39 states)
TRI-Release 2012 [USEPA, 2017a]
• Surface water = 5,110 lbs/yr (21 state)
• Total = 570,605 lbs/yr (39 states)
TRI-Release 2008 [USEPA, 2017a]
• Surface water = 2,453 lbs/yr (18 state)
• Total = 648,041 lbs/yr (38 states)
TRI-Release 2004 [USEPA, 2017a]
• Surface water = 1,276 lbs/yr (17 state)
• Total = 752,369 lbs/yr (38 states)
CDR Production Data (2012 - 2014) [USEPA,
2018a]
• 10M - 50M lbs/yr (2012, 2013, 2014)
Critical Health Endpoint
• Decreased iodine uptake [Roche and Layrisse,
1956]
• RfD = 0.0003 mg/kg/day
• Non-cancer HRL = 1.92 jig/L (2 jig/L rounded to
one sig. fig.)
Health Assessment Status
• USEPA (2008)
Fate / Transport
• Not expected to volatilize from water [HSDB, 2017c; ATSDR,
2004]
• Speciation and environmental fate and transport in water are
influenced by the presence of organic ligands, concentration of
anions, pH, and redox potential. These factors also affect mobility
[HSDB, 2017c; ATSDR, 2004]
• Exists primarily as Co(II) and Co(III), with Co(II) compounds
tending to be more soluble than Co(III) compounds [HSDB, 2017c]
• As an element, non-radioactive forms are considered to be
persistent in the environment
Sensitive Populations/Lifestages
• None identified
Manganese
• CASRN = 7439-96-5
• Substance Key = 18823
• HRL = 300 ng/L
Background
• A naturally-occurring element
• Manganese compounds are used in the manufacture of steel
alloys; in dry-cell batteries, electrical coils, ceramics, matches,
glass, dyes, fertilizers, and welding rods; as oxidizing agents; and as
animal food additives [HSDB, 2008b]
TRI-Release 2016 [USEPA, 2017a]
• Surface water = 63,245 lbs/yr (30 state)
• Total = 31,497,723 lbs/yr (49 states)
TRI-Release 2012 [USEPA, 2017a]
• Surface water = 108,967 lbs/yr (33 state)
• Total = 15,525,164 lbs/yr (49 states)
TRI-Release 2008 [USEPA, 2017a]
• Surface water = 117,457 lbs/yr (31 state)
• Total = 22,680,171 lbs/yr (47 states)
TRI-Release 2004 [USEPA, 2017a]
• Surface water = 126,910 lbs/yr (32 state)
• Total = 19,702,318 lbs/yr (48 states)
CDR Production Data (2012 - 2014) [USEPA,
2018a]
• 100M - 250M lbs/yr (2012, 2013)
• 250M- 500M lbs/yr (2014)
Critical Health Endpoint
• Human chronic ingestion data [WHO, 1973;
Schroeder et al, 1966; NRC, 1989]
• RfD = 0.14 mg/kg/day
• Non-cancer HRL = 320 jig/L (300 jig/L rounded to
one sig. fig.)
Health Assessment Status
• USEPA (2004)
Fate / Transport
• Not expected to volatilize from water [HSDB, 2008c; ATSDR,
2012]
• Mobility in water is influenced by pH, redox potential, and the
types of anions present [ATSDR, 2012]
• Common manganese compounds range from insoluble to
moderately soluble in water, with Mn(II) being the most common at
typical environmental pH. Mn(II) are typically moderately soluble
in water [ATSDR, 2012]
• As an element, non-radioactive forms are considered to be
persistent in the environment
Sensitive Populations/Lifestages
• Very young
• Elderly
• People with liver disease
A-2
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EPA - OGWDW
Final Regulatory Determination 4 Support Document - Appendix A. Additional Information, Part 1: Chemical Contaminants
January 2021
Contaminant
Background
Release and Production Data
Health Effect Findings
Molybdenum
• CASRN = 7439-98-7
• Substance Key = 18825
• HRL = 30 ng/L
Background
• A naturally-occurring element
• Elemental molybdenum is commonly used in alloys, in
superalloys for missile and aircraft parts, and as a catalyst in the
petrochemical industry [HSDB, 2008d]
• Molybdenum compounds are commonly used in pigments,
fertilizers and a variety of other commercial applications [HSDB,
2008e]
TRI-Release 2016 [USEPA, 2017a]
• None
TRI-Release 2012 [USEPA, 2017a]
• None
TRI-Release 2008 [USEPA, 2017a]
• None
TRI-Release 2004 [USEPA, 2017a]
• None
CDR Production Data (2012 - 2014) [USEPA,
2018a]
• 10M - 50M lbs/yr (2012, 2013, 2014)
Critical Health Endpoint
• Increased serum uric acid [Kovalsky et al., 1961 ]
• RfD = 0.005 mg/kg/day
• Non-cancer HRL = 32 jig/L (30 jig/L rounded to
one sig. fig.)
Health Assessment Status
• USEPA (1992)
Fate / Transport
• Although some organometallic compounds of molybdenum are
volatile, molybdenum typically occurs as molybdate anion in water
which is not expected to volatilize [HSDB, 2008e]
• Oxyanions such as molybdate are expected to be mobile [HSDB,
2008e] although at lower pH, molybdenum may accumulate in
sediment [ATSDR, 2017]
• As an element, non-radioactive forms are considered to be
persistent in the environment
Sensitive Populations/Lifestages
• None identified
Vanadium
• CASRN = 7440-62-2
• Substance Key = 18882
• HRL = 0.4 ng/L
Background
• A naturally-occurring element
• Used in producing rust-resistant, spring, and high-speed tool
steels. It is an important carbide stabilizer in making steels
[ATSDR, 2012]
• Commonly used as vanadium pentoxide which is a chemical
intermediate and a catalyst [ATSDR, 2012]
Fate / Transport
• In water, it is commonly found as vanadyl ion (4+) under reducing
conditions or vanadate ion (5+) under oxidizing conditions;
vanadate is the more mobile [HSDB, 2016b]
• Vanadyl and vanadate ions strongly bind to mineral and biogenic
particulates in water; only 13% of vanadium in water is in solution
[ATSDR, 2012]
• As an element, it is considered to be persistent in the environment
TRI-Release 2016 [USEPA, 2017a]
• Surface water = 7,379 lbs/yr (3 state)
• Total = 692,638 lbs/yr (13 states)
TRI-Release 2012 [USEPA, 2017a]
• Surface water = 9,415 lbs/yr (4 state)
• Total = 630,723 lbs/yr (14 states)
TRI-Release 2008 [USEPA, 2017a]
• Surface water = 7,790 lbs/yr (5 state)
• Total = 2,541,027 lbs/yr (19 states)
TRI-Release 2004 [USEPA, 2017a]
• Surface water = 1,170 lbs/yr (6 state)
• Total = 1,577,957 lbs/yr (23 states)
CDR Production Data (2012 - 2014) [USEPA,
2018a]
• 1M - 10M lbs/yr (2012, 2013, 2014)
Critical Health Endpoint
• Kidney toxicity [Boscolo et al., 1994]
• RfD = 0.00007 mg/kg/day
• Non-cancer HRL = 0.448 jig/L (0.4 jig/L rounded to
one sig. fig.)
Health Assessment Status
• USEPA (2009b)
Sensitive Populations/Lifestages
• None identified
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EPA - OGWDW Final Regulatory Determination 4 Support Document-Appendix A. Additional Information, Part 1: Chemical Contaminants January 2021
Contaminant
Initial Occurrence Findings -
National Drinking Water Data
Initial Occurrence Findings -
Non-National Drinking Water Data / State Data
1,1,1,2-T etrachloroethane
• CASRN = 630-20-6
• Substance Key = 9105
• HRL = 1 (j.g/L
NCOD/UCM Round 1, 24-State Cross-Section (1988-1992) [USEPA, 2001]
• MRL unavailable (min detect = 0.06 |ig/L)
• Samples w/ detects = 0.08% (43 of 56,734); 0.04% >1/2HRL; 0.02% >HRL
• Systems w/ detects = 0.18% (31 of 16,956); 0.12% >1/2HRL; 0.05% >HRL
• Detected Cone: Median = 0.59 jig/L 99%ile = 8.28 (jg/L Max = 9.2 (jg/L
NCOD/UCM Round 2, 20-State Cross-Section (1993-1997) [USEPA, 2001]
• MRL unavailable (min detect = 0.2 |ig/L)
• Samples w/ detects = 0.07% (70 of 97,950); 0.03% >1/2HRL; 0.01% >HRL
• Systems w/ detects = 0.21% (51 of 24,127); 0.08%>1/2HRL; 0.03% >HRL
• Detected Cone: Median = 0.5 (jg/L 99%ile = 7.58 jig/L Max = 18.0 jig/L
Second Six-Year Review (SYR2) State Drinking Water Data (1983-2005) [Data
provided to EPA by states and/or downloaded by EPA from state websites; raw and
finished water results presented separately whenever possible; "not provided" indicates
that the state did not explicitly identify results as representing raw or finished water]
• Systems w/ detects =
o CA (raw): 0.16% (6 of 3,747); 0.11% >1/2HRL; 0% >HRL
o CA (finished): Not detected in 362 systems
o CA (not provided): Not detected in 56 systems
o FL (not provided): 7.69% (1 of 13); 0% >1/2HRL; 0% >HRL
o IL (not provided): Not detected in 2 systems
o NC (raw): Not detected in 115 systems
o NC (finished): 0.52% (13 of 2,487); 0.44% >1/2HRL; 0.20% >HRL
o OH (not provided): 0.04% (1 of 2,533); 0.04% >1/2HRL; 0% >HRL
o Region 9 Tribes (not provided): Not detected in 285 systems
o SD (not provided): Not detected in 219 systems
o TX (not provided): Not detected in 5,660 systems
o WI '83-'99 (not provided): Not detected in 1,929 systems
o WI '00-'05 (not provided): Not detected in 956 systems
Third Six-Year Review (SYR3) State Drinking Water Data (2006-2011) [Data provided
to EPA by states and/or downloaded by EPA from state websites; raw and finished water
results presented separately whenever possible; "not provided" indicates that the state
did not explicitly identify results as representing raw or finished water]
• Systems w/ detects =
o AS (not provided): Not detected in 11 systems
o CA (raw): Not detected in 3,496 systems
o CA (finished): Not detected in 264 systems
o CA (not provided): Not detected in 72 systems
o FL (raw): Not detected in 3 systems
o FL (not provided): 2.44% (1 of 41); 0% >1/2HRL; 0% >HRL
o MI (not provided): Not detected in 2,801 systems
o Navajo Nation (not provided): Not detected in 46 systems
o PA (raw): Not detected in 13 systems
o PA (not provided): Not detected in 243 systems
o Region 9 Tribes (not provided): 0.52% (1 of 192); 0% >1/2HRL; 0% >HRL
o WA (raw): Not detected in 1,746 systems
o WA (finished): Not detected in 1,202 systems
o WA (not provided): Not detected in 617 systems
o WI (not provided): Not detected in 814 systems
Additional State Drinking Water Data (2012-2017) [obtained by EPA from state
websites; raw and finished water results presented separately whenever possible; "not
provided" indicates that the state did not explicitly identify results as representing raw or
finished water]
• Systems w/ detects =
o CA (raw): Not detected in 3,092 systems
o CA (finished): Not detected in 227 systems
o CA (not provided): Not detected in 122 systems
o WI (not provided): Not detected in 676 systems
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EPA - OGWDW Final Regulatory Determination 4 Support Document-Appendix A. Additional Information, Part 1: Chemical Contaminants January 2021
Contaminant
Initial Occurrence Findings -
National Drinking Water Data
Initial Occurrence Findings -
Non-National Drinking Water Data / State Data
Acephate
•CASRN = 30560-19-1
• Substance Key = 31325
• HRL = 0.4 ng/L
None.
Second Six-Year Review (SYR2) State Drinking Water Data (1998-2004) [Data
provided to EPA by states and/or downloaded by EPA from state websites; raw and
finished water results presented separately whenever possible; "not provided" indicates
that the state did not explicitly identify results as representing raw or finished water]
• Systems w/ detects =
o CA (raw): 50.0% (2 of 4); 25.0% > 1/2HRL; 0% >HRL
Third Six-Year Review (SYR3) State Drinking Water Data (2006-2011) [Data provided
to EPA by states and/or downloaded by EPA from state websites; raw and finished water
results presented separately whenever possible; "not provided" indicates that the state
did not explicitly identify results as representing raw or finished water]
• Systems w/ detects =
o CA (raw): Not detected in 3 systems
alpha-Hexachlorocyclohexane
•CASRN = 319-84-6
• Substance Key = 6535
• HRL = 0.005 ng/L
UCMR 4 Assessment Monitoring (2018 - 2020) results forthcoming.
Second Six-Year Review (SYR2) State Drinking Water Data (1995-2005) [Data
provided to EPA by states and/or downloaded by EPA from state websites; raw and
finished water results presented separately whenever possible; "not provided" indicates
that the state did not explicitly identify results as representing raw or finished water]
• Systems w/ detects =
o CA (raw): Not detected in 105 systems
o CA (finished): Not detected in 7 systems
o CA (not provided): Not detected in 2 systems
Third Six-Year Review (SYR3) State Drinking Water Data (2006-2011) [Data provided
to EPA by states and/or downloaded by EPA from state websites; raw and finished water
results presented separately whenever possible; "not provided" indicates that the state
did not explicitly identify results as representing raw or finished water]
• Systems w/ detects =
o CA (raw): 0.70% (1 of 142); 0.70% >1/2HRL; 0.70% > HRL
o CA (finished): 6.67% (1 of 15); 6.67% >1/2HRL; 6.67% > HRL
o CA (not provided): Not detected in 9 systems
o MI (not provided): Not detected in 2,482 systems
o WA (not provided): Not detected in 1 system
Additional State Drinking Water Data (2012-2017) [obtained by EPA from state
websites; raw and finished water results presented separately whenever possible; "not
provided" indicates that the state did not explicitly identify results as representing raw or
finished water]
• Systems w/ detects =
o CA (raw): Not detected in 139 systems
o CA (finished): Not detected in 18 systems
o CA (not provided): Not detected in 14 systems
Aniline
• CASRN = 62-53-3
• Substance Key = 2438
• HRL = 6 ng/L
None.
Second Six-Year Review (SYR2) State Drinking Water Data (1998) [Data provided to
EPA by states and/or downloaded by EPA from state websites; raw and finished water
results presented separately whenever possible; "not provided" indicates that the state
did not explicitly identify results as representing raw or finished water]
• Systems w/ detects =
o TX (not provided): 100% (2 of 2); 100% >1/2HRL; 100% > HRL
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Contaminant
Initial Occurrence Findings -
National Drinking Water Data
Initial Occurrence Findings -
Non-National Drinking Water Data / State Data
Cobalt
• CASRN = 7440-48-4
• Substance Key = 18870
• HRL = 2 ng/L
UCMR3 Assessment Monitoring (2013-2015) [USEPA, 2017b]
• MRL = 1 ng/L
• Occurrence in both GW and SW systems.
• Samples w/ detects = 1.32% (833 of 62,982); 1.27% > 1/2HRL; 0.56% > HRL
• Systems w/ detects = 5.02% (247 of 4,922); 4.88% > 1/2HRL; 2.58% > HRL
• Detected Cone: Median = 1.8 jig/L 99%ile = 25.4 jig/L Max= 1,097.099 jig/L
NIRS (1984-1986) [unpublished EPA data]
• MRL = 6 ng/L
• One sample per system, GW only
• Systems w/ detects = 0.30% (3 of 989); 0.30% > 1/2HRL; 0.30% >HRL
• Detected Cone: Median = 9.68 jig/L 99%ile = 10.63 jig/L Max = 10.65 jig/L
Second Six-Year Review (SYR2) State Drinking Water Data (1998-2005) [Data
provided to EPA by states and/or downloaded by EPA from state websites; raw and
finished water results presented separately whenever possible; "not provided" indicates
that the state did not explicitly identify results as representing raw or finished water]
• Systems w/ detects =
o CA (raw): 14.52% (9 of 62); 6.45% > 1/2HRL; 6.45% >HRL
o CA (finished): Not detected in 21 systems
o CA (not provided): Not detected in 4 systems
o IL (not provided): 4.55% (1 of 22); 4.55% > 1/2HRL; 4.55% >HRL
o OH (not provided): 12.00% (3 of 25); 12.00% > 1/2HRL; 12.00% >HRL
Third Six-Year Review (SYR3) State Drinking Water Data (2006-2011) [Data provided
to EPA by states and/or downloaded by EPA from state websites; raw and finished water
results presented separately whenever possible; "not provided" indicates that the state
did not explicitly identify results as representing raw or finished water]
• Systems w/ detects =
o CA (raw): 10.53% (6 of57); 5.26% >1/2HRL; 3.51%>HRL
o CA (finished): 2.86% (1 of 35); 0.00% >1/2HRL; 0.00% >HRL
o CA (not provided): Not detected in 2 systems
o MI (not provided): Not detected in 2 systems
o Navajo Nation (not provided): Not detected in 4 systems
o WI (not provided): Not detected in 9 systems
Additional State Drinking Water Data (2012-2017) [obtained by EPA from state
websites; raw and finished water results presented separately whenever possible; "not
provided" indicates that the state did not explicitly identify results as representing raw or
finished water]
• Systems w/ detects =
o CA (raw): 46.25% (37 of 80); 15.00% >1/2HRL; 7.50% >HRL
o CA (finished): 70.73% (29 of 41); 2.44% >1/2HRL; 0.00% >HRL
o CA (not provided): 50.00% (5 of 10); 0.00% >1/2HRL; 0.00% >HRL
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EPA - OGWDW Final Regulatory Determination 4 Support Document-Appendix A. Additional Information, Part 1: Chemical Contaminants January 2021
Contaminant
Initial Occurrence Findings -
National Drinking Water Data
Initial Occurrence Findings -
Non-National Drinking Water Data / State Data
Manganese
• CASRN = 7439-96-5
• Substance Key = 18823
• HRL = 300 ng/L
NIRS (1984-1986) [unpublished EPA data]
• MRL = 1 ng/L
• One sample per system, GW only
• Systems w/ detects = 67.95% (672 of 989); 6.07% > 1/2HRL; 3.24% >HRL
• Detected Cone: Median = 3.62 jig/L 99%ile = 584.0 jig/L Max = 1,341 jig/L
UCMR 4 Assessment Monitoring (2018 - 2020) results forthcoming.
Second Six-Year Review (SYR2) State Drinking Water Data (1980-2005) [Data
provided to EPA by states and/or downloaded by EPA from state websites; raw and
finished water results presented separately whenever possible; "not provided" indicates
that the state did not explicitly identify results as representing raw or finished water]
• Systems w/ detects =
o CA (raw): 43.45% (2,007 of 4,619); 17.75% > 1/2HRL; 10.87% >HRL
o CA (finished): 49.82% (278 of 558); 14.87% > 1/2HRL; 9.32% >HRL
o CA (not provided): 59.30% (51 of86); 19.77% > 1/2HRL; 9.30% >HRL
o NC (raw): 20.78% (16 of 77); 5.19% >1/2HRL; 5.19% >HRL
o NC (finished): 53.20% (1,263 of2,374); 9.18%>1/2HRL; 4.00%>HRL
o Region 9 Tribes (not provided): 40.91% (63 of 154); 16.23% >1/2HRL; 9.09%
>HRL
o WI '80-99 (not provided): 66.93% (595 of 889); 13.84%>1/2HRL; 6.30%>HRL
o WI '00-05 (not provided): 69.74% (816 of 1,170); 6.92%>1/2HRL; 3.76%>HRL
Third Six-Year Review (SYR3) State Drinking Water Data (2006-2011) [Data provided
to EPA by states and/or downloaded by EPA from state websites; raw and finished water
results presented separately whenever possible; "not provided" indicates that the state
did not explicitly identify results as representing raw or finished water]
• Systems w/ detects =
o CA (raw): 47.65% (1,938 of 4,067); 20.14% >1/2HRL; 12.27% >HRL
o CA (finished): 54.43% (313 of 575); 20.35% >1/2HRL; 11.83%>HRL
o CA (not provided): 49.56% (56 of 113); 18.58% >1/2HRL; 14.16% >HRL
o FL (raw): 82.86% (29 of 35); 0.00% >1/2HRL; 0.00% >HRL
o FL (not provided): 63.87% (1,052 of 1,647); 0.24% >1/2HRL; 0.06% >HRL
o MI (not provided): 65.45% (324 of 495); 7.27% >1/2HRL; 4.44% >HRL
o Navajo Nation (not provided): 48.21% (54 of 112); 0% >1/2HRL; 0% >HRL
o PA (raw): 86.54% (45 of 52); 30.77% >1/2HRL; 23.08% >HRL
o PA (not provided): 67.42% (89 of 132); 22.73% >1/2HRL; 15.15% >HRL
o Region 1 Tribes (not provided): 80% (4 of 5); 0% >1/2HRL; 0% >HRL
o Region 9 Tribes (not provided): 50% (48 of 96); 16.67% >1/2HRL; 0% >HRL
o TN (not provided): 19.17% (46 of 240); 0% >1/2HRL; 0% >HRL
o WA(raw): 54.66% (1,091 of 1,996); 12.12% >1/2HRL; 5.56% >HRL
o WA (finished): 53.46% (579 of 1,083); 10.90% >1/2HRL; 3.97% >HRL
o WA (not provided): 58.64% (499 of 851); 6.35% >1/2HRL; 2.35% >HRL
o WI (not provided): 70.9% (1,362 of 1,921); 7.76% >1/2HRL; 3.85% >HRL
Additional State Drinking Water Data (2012-2017) [obtained by EPA from state
websites; raw and finished water results presented separately whenever possible; "not
provided" indicates that the state did not explicitly identify results as representing raw or
finished water]
• Systems w/ detects =
o CA (raw): 48.95% (1,934 of 3,951); 20.50% >1/2HRL; 13.39% >HRL
o CA (finished): 55.19% (372 of 674); 20.03% >1/2HRL; 12.02% >HRL
o CA (not provided): 42.78% (83 of 194); 16.49% >1/2HRL; 8.76% >HRL
o FL (not provided): 80.69% (1,337 of 1,657); 0.72% > 'AHRL; 0.30% >HRL
o WI (not provided): 87.76% (552 of 629); 10.17% > 1/2HRL; 4.45% >HRL
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EPA - OGWDW Final Regulatory Determination 4 Support Document-Appendix A. Additional Information, Part 1: Chemical Contaminants January 2021
Contaminant
Initial Occurrence Findings -
National Drinking Water Data
Initial Occurrence Findings -
Non-National Drinking Water Data / State Data
Molybdenum
• CASRN = 7439-98-7
• Substance Key = 18825
• HRL = 30 ng/L
UCMR3 Assessment Monitoring (2013-2015) [USEPA, 2017b]
• MRL = 1 ng/L
• Occurrence in both GW and SW systems.
• Samples w/ detects = 40.29% (25,377 of 62,986); 1.28% > 1/2HRL; 0.37% > HRL
• Systems w/ detects = 51.73% (2,546 of 4,922); 3.49% > 1/2HRL; 1.28% > HRL
• Detected Cone: Median = 2.4 |rg/L 99%ile = 29 |rg/L Max =196 (jg/L
NIRS (1984-1986) [unpublished EPA data]
• MRL = 6 ng/L
• One sample per system, GW only
• Systems w/ detects = 7.79% (77 of 989); 3.03% > 1/2HRL; 0.91% >HRL
• Detected Cone: Median = 10 jig/L 99%ile = 106 jig/L Max =181 (jg/L
Second Six-Year Review (SYR2) State Drinking Water Data (1995-2005) [Data
provided to EPA by states and/or downloaded by EPA from state websites; raw and
finished water results presented separately whenever possible; "not provided" indicates
that the state did not explicitly identify results as representing raw or finished water]
• Systems w/ detects =
o CA (raw): 65.79% (100 of 152); 12.50% > 1/2HRL; 5.92% >HRL
o CA (finished): 65.52% (19 of 29); 17.24% > 1/2HRL; 3.45% >HRL
o CA (not provided): 100.00% (4 of 4); 0.00% > 1/2HRL; 0.00% >HRL
o IL (not provided): 17.23% (149 of 865); 14.22% > 1/2HRL; 4.86% >HRL
o OH (not provided): 50.00% (13 of 26); 11.54% > 1/2HRL; 7.69% >HRL
o WI (not provided): Not detected in 1 system
Third Six-Year Review (SYR3) State Drinking Water Data (2006-2011) [Data provided
to EPA by states and/or downloaded by EPA from state websites; raw and finished water
results presented separately whenever possible; "not provided" indicates that the state
did not explicitly identify results as representing raw or finished water]
• Systems w/ detects =
o CA (raw): 73.26% (63 of 86); 15.12% >1/2HRL; 9.30% >HRL
o CA (finished): 63.04% (29 of 46); 13.04% >1/2HRL; 8.70% >HRL
o CA (not provided): 60.00% (3 of 5); 20.00% >1/2HRL; 0.00% >HRL
o WI (not provided): Not detected in 1 system
Additional State Drinking Water Data (2012-2017) [obtained by EPA from state
websites; raw and finished water results presented separately whenever possible; "not
provided" indicates that the state did not explicitly identify results as representing raw or
finished water]
• Systems w/ detects =
o CA (raw): 72.16% (70 of 97); 9.28% > 1/2HRL; 4.12% >HRL
o CA (finished): 76.09% (35 of 46); 4.35% > 1/2HRL; 0.00% >HRL
o CA (not provided): 77.78% (7 of 9); 22.22% > 1/2HRL; 0.00% >HRL
o WI (not provided): 50.00% (1 of 2); 50.00% >1/2HRL; 50.00% >HRL
A-8
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EPA - OGWDW Final Regulatory Determination 4 Support Document-Appendix A. Additional Information, Part 1: Chemical Contaminants January 2021
Contaminant
Initial Occurrence Findings -
National Drinking Water Data
Initial Occurrence Findings -
Non-National Drinking Water Data / State Data
Vanadium
• CASRN = 7440-62-2
• Substance Key = 18882
• HRL = 0.4 ng/L
UCMR3 Assessment Monitoring (2013-2015) [USEPA, 2017b]
• MRL = 0.2 ng/L
• Occurrence in both GW and SW systems.
• Samples w/ detects = 60.26% (37,954 of 62,981); 58.33% > 1/2HRL; 45.2% > HRL
• Systems w/ detects = 73.65% (3,625 of 4,922); 72.04% > 1/2HRL; 53.8% > HRL
• Detected Cone: Median = 1.3 jig/L 99%ile = 38 jig/L Max =193 (jg/L
NIRS (1984-1986) [unpublished EPA data]
• MRL = 3 ng/L
• One sample per system, GW only
• Systems w/ detects = 14.76% (146 of 989); 14.76% >1/2HRL; 14.76% >HRL
• Detected Cone: Median = 7.3 jig/L 99%ile = 45.1 jig/L Max = 70.4 jig/L
Second Six-Year Review (SYR2) State Drinking Water Data (1996-2005) [Data
provided to EPA by states and/or downloaded by EPA from state websites; raw and
finished water results presented separately whenever possible; "not provided" indicates
that the state did not explicitly identify results as representing raw or finished water]
• Systems w/ detects =
o CA (raw): 67.34% (1,709 of 2,538); 67.10% > 1/2HRL; 67.06% >HRL
o CA (finished): 54.32% (132 of 243); 54.32% > 1/2HRL; 54.32% >HRL
o CA (not provided): 52.78% (19 of 36); 52.78% > 1/2HRL; 52.78% >HRL
o IL (not provided): Not detected in 17 systems
o OH (not provided): Not detected in 23 systems
Third Six-Year Review (SYR3) State Drinking Water Data (2006-2011) [Data provided
to EPA by states and/or downloaded by EPA from state websites; raw and finished water
results presented separately whenever possible; "not provided" indicates that the state
did not explicitly identify results as representing raw or finished water]
• Systems w/ detects =
o CA (raw): 71.31% (875 of 1,227); 71.31% >1/2HRL; 71.31% >HRL
o CA (finished): 47.11% (57 of 121); 47.11%>1/2HRL; 47.11%>HRL
o CA (not provided): 59.38% (19 of 32); 59.38% >1/2HRL; 59.38% >HRL
o MI (not provided): 8.33% (1 of 12); 8.33% >1/2HRL; 8.33% >HRL
o Navajo Nation (not provided): 50% (1 of 2); 50% >1/2HRL; 50% >HRL
o Region 9 Tribes (not provided): Not detected in 1 system
o WI (not provided): Not detected in 10 systems
Additional State Drinking Water Data (2012-2017) [obtained by EPA from state
websites; raw and finished water results presented separately whenever possible; "not
provided" indicates that the state did not explicitly identify results as representing raw or
finished water]
• Systems w/ detects =
o CA (raw): 76.62% (803 of 1,048); 76.62% >1/2HRL; 76.62% >HRL
o CA (finished): 64.55% (71 of 110); 64.55% >1/2HRL; 64.55% >HRL
o CA (not provided): 71.93% (41 of 57); 71.93% >1/2HRL; 71.93% >HRL
A-9
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EPA - OGWDW Final Regulatory Determination 4 Support Document-Appendix A. Additional Information, Part 1: Chemical Contaminants January 2021
Contaminant
Initial Occurrence Findings -
Non-National Drinking Water Data / Supplemental
Initial Occurrence Findings -
Ambient Water / NAWQA-NWIS
1,1,1,2-T etrachloroethane
• CASRN = 630-20-6
• Substance Key = 9105
• HRL = 1 (j.g/L
Recent CCRs from 22 CWSs that serve >1M (2010-2017) [obtained by EPA
from PWS websites]
• Not detected in the 2 CWSs with data from NY
NAWQA Ambient Water [WQP, 2018]
• MRLs unavailable (min detect = 0.009 ug/L)
• Data for Cycle 1 and 3 only
Cycle 1 (1992-2001)
o Samples w/ detects = 0.09% (6 of 6,319); 0% > 1/2HRL; 0% >HRL
o Sites w/ detects = 0.13% (6 of 4,606); 0% > 1/2HRL; 0% >HRL
o Detected Cone: Median = 0.018 ug/L 99%ile = 0.1 ug/L Max = 0.064 ug/L
Cycle 3 (2013-2016)
o Samples w/ detects = 0.06% (1 of 1,720); 0% > 1/2HRL; 0% >HRL
o Sites w/ detects = 0.06% (1 of 1,540); 0% > 1/2HRL; 0% >HRL
o Detected Cone: Median = 0.269 jig/L 99%ile = 0.269 jig/L Max = 0.269 jig/L
NWIS Ambient Water (1991-2016) [WQP, 2017]
• Samples w/ detects = 0.11% (19 of 17,180)
• Sites w/ detects = 0.16% (13 of 8,363)
• Detected Cone: Median = 0.047 ug/L 99%ile = 250 ug/L Max = 290 ug/L
Acephate
•CASRN = 30560-19-1
• Substance Key = 31325
• HRL = 0.4 ug/L
OPP Estimated Environmental Concentration (EEC) [USEPA, 2006]
• Chronic exposure: in SW, EEC = 7.2 ug/L; in GW, EEC = 0.02 ug/L
NAWQA Ambient Water [WQP, 2018]
• MRLs unavailable (min detect = 0.00055 ug/L)
• Data for Cycle 2 and 3 only
Cycle 2 (2002-2012)
o Samples w/ detects = 28.42% (106 of 373); 0% > 1/2HRL; 0% >HRL
o Sites w/ detects = 38.2% (34 of 89); 0% > 1/2HRL; 0% >HRL
o Detected Cone: Median = 0.018 ug/L 99%ile = 1.74 ug/L Max = 2.28 ug/L
Cycle 3 (2013-2016)
o Samples w/ detects = 12.98% (1,346 of 10,370); 0.04% > 1/2HRL; 0.01% >HRL
o Sites w/ detects = 7.42% (130 of 1,751); 0.11% > 1/2HRL; 0.06% >HRL
o Detected Cone: Median = 0.021 jig/L 99%ile = 2.12 (jg/L Max = 10.4 (jg/L
NWIS Ambient Water (1991-2016) [WQP, 2017]
• Samples w/ detects = 5.1% (82 of 1,607)
• Sites w/ detects = 3.98% (27 of 679)
• Detected Cone: Median = 0.055 ug/L 99%ile = 11 ug/L Max= 19 ug/L
alpha-
Hexachlorocyclohexane
•CASRN = 319-84-6
• Substance Key = 6535
• HRL = 0.005 ug/L
PDP Finished and Raw Water (2002-2007) [USDA, 2018]
• % Samples w/ detects (finished water) = 0% (0 of 752)
• % Samples w/ detects (raw water) = 0% (0 of 400)
National Pesticide Survey (1988-1990) [USEPA, 1990]
• MRL = 0.060 ug/L
• Not detected in samples from 566 CWS wells or 783 rural domestic wells
NAWQA Ambient Water [WQP, 2018]
• MRLs unavailable (min detect = 0.0004 ug/L)
• Data for Cycle 1 and 2 only
Cycle 1 (1992-2001)
o Samples w/ detects = 0.29% (62 of 21,723); 0.24% > 1/2HRL; 0.19% >HRL
o Sites w/ detects = 0.3% (22 of 7,411); 0.27% > 1/2HRL; 0.23% >HRL
o Detected Cone: Median = 0.012 jig/L 99%ile = 0.2 jig/L Max = 0.21 jig/L
Cycle 2 (2002-2012)
o Samples w/ detects = 0.01% (1 of 6,842); 0.01% > 1/2HRL; 0.01% >HRL
o Sites w/ detects = 0.06% (1 of 1,604); 0.06% > 1/2HRL; 0.06% >HRL
o Detected Cone: Median = 0.016 jig/L 99%ile = 0.0162 jig/L Max = 0.0162 jig/L
NWIS Ambient Water (1991-2016) [WQP, 2017]
• Samples w/ detects = 0.32% (66 of 20,464)
• Sites w/ detects = 0.55% (39 of 7,146)
• Detected Cone: Median = 0.093 ug/L 99%ile = 1.6 ug/L Max = 2.7 ug/L
A-10
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EPA - OGWDW
Final Regulatory Determination 4 Support Document - Appendix A. Additional Information, Part 1: Chemical Contaminants
January 2021
Contaminant
Initial Occurrence Findings -
Non-National Drinking Water Data / Supplemental
Initial Occurrence Findings -
Ambient Water / NAWQA-NWIS
Aniline
• CASRN = 62-53-3
• Substance Key = 2438
• HRL = 6 ug/L
None.
None.
Cobalt
• CASRN = 7440-48-4
• Substance Key = 18870
• HRL = 2 ng/L
2006 Community Water System Survey [USEPA, 2009a]
• Data from 1 system
• Not detected in the single finished water sample
NAWQA Ambient Water [WQP, 2018]
• MRLs unavailable (min detect = 0.007 |ig/L)
• Occurrence in SW and GW
Cycle 1 (1992-2001)
o Samples w/ detects = 20.22% (1,456 of 7,202); 7.32% > 1/2HRL; 4.51% >HRL
o Sites w/ detects = 26.81% (969 of 3614); 11.73% > 1/2HRL; 7.66% >HRL
o Detected Cone: Median = 0.205 jig/L 99%ile = 45.9 (jg/L Max = 684 (jg/L
Cycle 2 (2002-2012)
o Samples w/ detects = 95.04% (6,175 of 6,497); 10.91% > 1/2HRL; 5.11% >HRL
o Sites w/ detects = 94.99% (3,584 of 3,773); 13.25% > 1/2HRL; 6.92% >HRL
o Detected Cone: Median = 0.152 jig/L 99%ile = 7.53 (jg/L Max = 55.9 (jg/L
Cycle 3 (2013-2016)
o Samples w/ detects = 70.15% (1,676 of 2,389); 8.66% > 1/2HRL; 4.4% >HRL
o Sites w/ detects = 70.77% (1,634 of 2,309); 8.71% > 1/2HRL; 4.5% >HRL
o Detected Cone: Median = 0.119 jxg/L | 99%ile = 11.7 ng/L Max = 96.3 (jg/L
NWIS Ambient Water (1991-2016) [WQP, 2017]
• Samples w/ detects = 36.11% (28,806 of 79,772)
• Sites w/ detects = 49.12% (7,663 of 15,599)
• Detected Cone: Median = 0.291 ng/L 99%ile = 500 ng/L Max = 10,200 ng/L
Manganese
• CASRN = 7439-96-5
• Substance Key = 18823
• HRL = 300 ng/L
Recent CCRs from 22 CWSs that serve >1M (2010-2017) [obtained by EPA
from PWS websites]
• Data from 10 CWSs; detections in 8 CWSs; detections ranged from 8 (jg/L to
230 ng/L
NAWQA Ambient Water [WQP, 2018]
• MRLs unavailable (min detect = 0.05 ng/L)
• Higher occurrence (detection percentage) in SW
• Higher detected concentrations in GW
2006 Community Water System Survey [USEPA, 2009a]
• Data from 1 system
• Detected in the single finished water sample; detect = 0.003 jig/L
Cycle 1 (1992-2001)
o Samples w/ detects = 86.15% (30,580 of 35,495); 10.13% > 1/2HRL; 5.02% >HRL
o Sites w/detects = 78.28% (6,488 of 8,288); 18.77%> 1/2HRL; 11.06%>HRL
o Detected Cone: Median = 19.5 (jg/L 99%ile = 1,300 jig/L Max = 59,000 jig/L
Cycle 2 (2002-2012)
o Samples w/ detects = 89.89% (8,689 of 9,666); 14.59% > 1/2HRL; 8.42% >HRL
o Sites w/ detects = 91.48% (3,885 of 4,247); 15.71%> 1/2HRL; 9.47%>HRL
o Detected Cone: Median = 11.1 (jg/L 99%ile = 1,701 jig/L Max = 22,000 jig/L
Cycle 3 (2013-2016)
o Samples w/ detects = 80.91% (3,256 of 4,024); 11.28% > 1/2HRL; 5.42% >HRL
o Sites w/ detects = 74.41% (1,791 of 2,407); 11.38% > 1/2HRL; 6.90%>HRL
o Detected Cone: Median = 21.5 jig/L 99%ile = 1,564 jig/L Max = 9,530 jig/L
NWIS Ambient Water (1991-2016) [WQP, 2017]
• Samples w/ detects = 86.89% (248,776 of 286,309)
• Sites w/ detects = 82.94% (37,511 of 45,224)
• Detected Cone: Median = 41.45 ng/L 99%ile = 5750 ng/L Max = 1130000 ng/L
A-ll
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EPA - OGWDW Final Regulatory Determination 4 Support Document-Appendix A. Additional Information, Part 1: Chemical Contaminants January 2021
Contaminant
Initial Occurrence Findings -
Non-National Drinking Water Data / Supplemental
Initial Occurrence Findings -
Ambient Water / NAWQA-NWIS
Molybdenum
• CASRN = 7439-98-7
• Substance Key = 18825
• HRL = 30 ng/L
2006 Community Water System Survey [USEPA, 2009a]
• Data from 2 systems
• Detected in 2 of 2 finished water samples; 90%ile detect = 31.000 (jg/L
NAWQA Ambient Water [WQP, 2018]
• MRLs unavailable (min detect = 0.01 ng/L)
• Occurrence in SW and GW
Cycle 1 (1992-2001)
o Samples w/ detects = 48.64% (3,437 of 7,066); 3.69% > 1/2HRL; 1.37% >HRL
o Sites w/ detects = 55.38% (2,002 of 3,615); 5.12% > 1/2HRL; 2.1% >HRL
o Detected Cone: Median = 2.72 jig/L 99%ile = 50.8 jig/L Max = 4,730 jig/L
Cycle 2 (2002-2012)
o Samples w/ detects = 85.04% (5,593 of 6,577); 2.9% > 1/2HRL; 0.87% >HRL
o Sites w/ detects = 85.91% (3,267 of 3,803); 2.81% > 1/2HRL; 0.87% >HRL
o Detected Cone: Median = 1.17 (jg/L 99%ile = 30 jig/L Max = 304 (jg/L
Cycle 3 (2013-2016)
o Samples w/ detects = 85.84% (2,104 of 2,451); 2.86% > 1/2HRL; 0.78% >HRL
o Sites w/ detects = 86.33% (2,034 of 2,356); 2.84% > 1/2HRL; 0.81% >HRL
o Detected Cone: Median = 0.857 (rg/L 99%ile = 27.6 (jg/L Max = 226 (rg/L
NWIS Ambient Water (1991-2016) [WQP, 2017]
• Samples w/ detects = 57.08% (38,479 of 67,408)
• Sites w/ detects = 66.14% (11,612 of 17,558)
• Detected Cone: Median = 1.79 ng/L | 99%ile = 70 ng/L | Max = 42,000 ng/L
Vanadium
• CASRN = 7440-62-2
• Substance Key = 18882
• HRL = 0.4 ng/L
2006 Community Water System Survey [USEPA, 2009a]
• Data from 3 systems
• Detected in 4 of 5 finished water samples; 90%ile detect = 4.100 |rg/L
NAWQA Ambient Water [WQP, 2018]
• MRLs unavailable (min detect = 0.02 ng/L)
• Occurrence in SW and GW
• Higher detected concentrations in GW
Cycle 1 (1992-2001)
o Samples w/ detects = 37.23% (1,067 of2,866); 35.42%> 1/2HRL; 31.58%>HRL
o Sites w/ detects = 54.06% (639 of 1,182); 52.71% > 1/2HRL; 48.05% >HRL
o Detected Cone: Median = 2.4 jig/L 99%ile = 67.4 (jg/L Max = 190 (jg/L
Cycle 2 (2002-2012)
o Samples w/ detects = 91.71% (9,132 of9,957); 82.55%> 1/2HRL; 74.3%>HRL
o Sites w/ detects = 87% (3,373 of 3,877); 75.39% > 1/2HRL; 66.29% >HRL
o Detected Cone: Median =1.4 jig/L 99%ile = 37.5 (jg/L Max = 294 jig/L
Cycle 3 (2013-2016)
o Samples w/ detects = 92.99% (8,656 of 9,309); 87.47% > 1/2HRL; 78.76% >HRL
o Sites w/ detects = 76.04% (1,869 of 2,458); 63.59% > 1/2HRL; 53.17% >HRL
o Detected Cone: Median =1.5 jig/L 99%ile = 31.6 (jg/L Max = 139 jig/L
NWIS Ambient Water (1991-2016) [WQP, 2017]
• Samples w/ detects = 35.75% (24,998 of 69,926)
• Sites w/ detects = 60.39% (9,195 of 15,227)
• Detected Cone: Median = 3.9 ug/L 99%ile = 140 ng/L Max = 19,000 ng/L
A-12
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EPA - OGWDW
Final Regulatory Determination 4 Support Document - Appendix A. Additional Information, Part 1: Chemical Contaminants
January 2021
Contaminant
Initial Occurrence Findings -
Ambient Water / STORET
Initial Occurrence Findings -
Ambient Water / Additional Studies
Other Data
1,1,1,2-T etrachloroethane
• CASRN = 630-20-6
• Substance Key = 9105
• HRL = 1 (j.g/L
STORET [WQP, 2017]
• MRL unavailable (min detect = 0 ng/L)
• Data from 30 states
• Samples w/ detects = 58.75% (15,368 of 26,160)
• Sites w/ detects = 53.67% (2,295 of 4,276)
• Detected Cone: Median = 0.5 jig/L 99%ile = 50
Hg/L Max= 1,800 (j.g/L
NAWQA Quality of Public Supply Wells (1993-2007; RL = 0.015 - 0.2 ng/L) [Toccalino et
al, 2010]
• Samples w/ detections = 0.36% (3 of 832)
• Detected Cone: Median = 0.01 jig/L 99%ile = 0.01 jig/L Max = 0.011 (jg/L
NAWQA VOCs in Northeast and Mid-Atlantic Regions (1993-1998; RL = 0.5 - 20 ng/L)
[Grady and Casey, 2001]
• Samples w/ detections in randomly selected CWSs = 0.02% (2 of 12,727); range of
detections = 1.0 jig/L
Not detected in the following studies:
• NAWQA Carbonate Aquifer Study (1993-2005; not detected > 0.2 |ig/L) [Lindsey et al.,
2009]
• NAWQA Domestic Well Water Quality (1991-2004) [DeSimone, 2009]
• USGS CWSs Drawing from Streams and Groundwater (2002-2005) [Hopple et al., 2009
and Kingsbury et al., 2008]
• NAWQA National Random Survey (1999-2000) [Grady, 2003]
• NAWQA National Focused Survey (1999-2001) [Delzer and Ivahnenko, 2003]
• NAWQA Historical VOC Monitoring (1985-1995) [Squillace et al,19991
None.
Acephate
•CASRN = 30560-19-1
• Substance Key = 31325
• HRL = 0.4 ng/L
STORET [WQP, 2017]
• MRL unavailable (min detect = NA |ig/L)
• Data from 4 states
• Samples w/ detects = 0% (0 of 200)
• Sites w/ detects = 0% (0 of 57)
None.
CDC Fourth National Report
(2007-2008) [CDC, 2019]
• 95%ile
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EPA - OGWDW Final Regulatory Determination 4 Support Document-Appendix A. Additional Information, Part 1: Chemical Contaminants January 2021
Contaminant
Initial Occurrence Findings -
Ambient Water / STORET
Initial Occurrence Findings -
Ambient Water / Additional Studies
Other Data
Cobalt
• CASRN = 7440-48-4
• Substance Key = 18870
• HRL = 2 ng/L
STORET [WQP, 2017]
• MRL unavailable (min detect = 0 ng/L)
• Data from 47 states
• Samples w/ detects = 38.28% (74,780 of 195,334)
• Sites w/ detects = 54.58% (13,718 of 25,134)
• Detected Cone: Median =1.01 jig/L 99%ile =
311 ng/L | Max= 1,900,000 ng/L
NAWQA Trace Elements in Groundwater (1992-2003; RL = 1 ng/L) [Ayotte et al., 2011]
• Samples w/ detections = 27.7% of 3,026 samples, max conc. = 680 (rg/L
NAWQA Domestic Well Water Quality (1991-2004; MRL and LT-MDL = 1 ng/L)
[DeSimone, 2009]
• Samples w/ detections in aquifer studies = 34.2% (537 of 1,572); 90%ile = 0.52 (rg/L
• Samples w/ detections in agricultural land-use studies = 47.4% (37 of 78); 90%ile = 0.23
Hg/L
NAWQA Quality of Public Supply Wells (1993-2007; RL = 0.01 - 1 ng/L) [Toccalino et
al, 2010]
• Samples w/ detections = 63.16% (396 of 627)
• Detected Conc: Median = 0.11 (rg/L 99%ile = 4.37 (jg/L Max = 10.77 jig/L
NAWQA Glacial Aquifer Study of Northern U.S. (1991-2003; no RL reported) [Groschen
etal, 2009]
• Samples w/ detections = 53.2% (451 of 847), max conc. = 95 ng/L
CDC Fourth National Report
(2015-2016) [CDC, 2019]
• 95%ile= 1.53 ng/L in 3,061
urine samples
• 95%ile = 0.400 ng/L in 3,454
blood samples
Manganese
• CASRN = 7439-96-5
• Substance Key = 18823
• HRL = 300 ng/L
STORET [WQP, 2017]
• MRL unavailable (min detect = 0 ng/L)
• Data from 50 states
• Samples w/ detects = 92.3% (704,428 of 763,164)
• Sites w/ detects = 91.18% (67,729 of 74,280)
• Detected Cone: Median = 46.9 jig/L 99%ile =
6,500 (j.g/L | Max= 18,604,000 ng/L
Contaminants of Emerging Concern in Source and Treated Drinking Waters (2010-2012;
RL = 1 ng/L) [Glassmeyer et al, 2017]
• Samples w/ detections in source water = 92% of 25 samples, max conc. = 1,497 jig/L
• Samples w/ detections in finished water = 64% of 25 samples, max conc. = 55.6 jig/L
NAWQA Trace Elements in Groundwater (1992-2003; RL = 1 |ig/L) [Ayotte et al, 2011]
• Samples w/ detections = 69.5% of 4,976 samples, max conc. = 28,000 jig/L
NAWQA Domestic Well Water Quality (1991-2004; Range of MRLs & LT-MDLs 0.1-1
Hg/L) [DeSimone, 2009]
• Samples w/ detections in aquifer studies = 63.9% (1,380 of 2,159); 90%ile = 172.39 jig/L
• Samples w/ detections in agricultural land-use studies = 30.9% (131 of 424); 90%ile =
41.5 ng/L
NAWQA Quality of Public Supply Wells (1993-2007; MRL = 0.05 - 4 ng/L) [Toccalino et
al, 2010]
• Samples w/ detections = 67.2% (543 of 808)
• Detected Conc: Median = 8.99 jig/L 99%ile = 732.03 jig/L Max = 1923 jig/L
NAWQA Glacial Aquifer Study of Northern U.S. (1991-2003) [Groschen et al, 2009]
• Samples w/ detections = 86.5% (1375 of 1590), max conc. = 28200 ng/L
CDC Fourth National Report
(2015-2016) [CDC, 2019]
• 95%ile = 16.4 ng/L in 4,987
blood samples
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EPA - OGWDW Final Regulatory Determination 4 Support Document-Appendix A. Additional Information, Part 1: Chemical Contaminants January 2021
Contaminant
Initial Occurrence Findings -
Ambient Water / STORET
Initial Occurrence Findings -
Ambient Water / Additional Studies
Other Data
Molybdenum
• CASRN = 7439-98-7
• Substance Key = 18825
• HRL = 30 ng/L
STORET [WQP, 2017]
• MRL unavailable (min detect = 0 ng/L)
• Data from 44 states
• Samples w/ detects = 47.19% (53,470 of 113,303)
• Sites w/ detects = 45.19% (9,662 of 21,379)
• Detected Cone: Median = 2.61 jig/L 99%ile =
9,820 ng/L | Max = 360,000 ng/L
NAWQA Trace Elements in Groundwater (1992-2003; RL = 1 ng/L) [Ayotte et al., 2011]
• Samples w/ detections = 57.6% of 3,063 samples, max conc. = 4,700 (rg/L
NAWQA Domestic Well Water Quality (1991-2004; Range of MRLs & LT-MDLs = 0.03 -
1 ng/L) [DeSimone, 2009]
• Samples w/ detections in aquifer studies = 58.6% (921 of 1,572); 90%ile = 6.0 (rg/L
• Samples w/ detections in agricultural land-use studies = 62.8% (49 of 78); 90%ile = 3.0
Hg/L
• 0.57% of wells exceeded 40 jig/L
NAWQA Quality of Public Supply Wells (1993-2007; RL = 0.06 - 1 ng/L) [Toccalino et
al, 2010]
• Samples w/ detections = 77.23% (485 of 628)
• Detected Conc: Median = 2 jig/L 99%ile = 30.28 (jg/L Max = 89 jig/L
NAWQA Glacial Aquifer Study of Northern U.S. (1991-2003; no RL reported) [Groschen
etal, 2009]
• Samples w/ detections = 71.8% (608 of 847), max conc. = 304 ng/L
CDC Fourth National Report
(2015-2016) [CDC, 2019]
• 95%ile = 137 ng/L in 3,060
urine samples
Vanadium
• CASRN = 7440-62-2
• Substance Key = 18882
• HRL = 0.4 ng/L
STORET [WQP, 2017]
• MRL unavailable (min detect = 0 ng/L)
• Data from 48 states
• Samples w/ detects = 45.92% (84,431 of 183,853)
• Sites w/ detects = 56.8% (13,175 of 23,195)
• Detected Cone: Median = 3.68 jig/L 99%ile =
207 (j.g/L Max = 86,000 (j.g/L
Contaminants of Emerging Concern in Source and Treated Drinking Waters (2010-2012;
RL = 1 ng/L) [Glassmeyer et al, 2017]
• Samples w/ detections in source water = 44% of 25 samples, max conc. = 5.8 ng/L
• Samples w/ detections in finished water = 16% of 25 samples, max conc. = 4.9 jig/L
NAWQA Trace Elements in Groundwater (1992-2003; RL = 1 |ig/L) [Ayotte et al, 2011]
• Samples w/ detections = 69.1% of 833 samples, max conc. = 190 jig/L
NAWQA Domestic Well Water Quality (1991-2004; Range of MRLs & LT-MDLs 0.2 - 1
Hg/L) [DeSimone, 2009]
• Samples w/ detections in aquifer studies = 68.3% (452 of 662); 90%ile = 20.4 jig/L
• Samples w/ detections in agricultural land-use studies = 94.4% (34 of 36); 90%ile = 28.4
Hg/L
NAWQA Quality of Public Supply Wells (1993-2007; MRL = 0.02 - 5 ng/L) [Toccalino et
al, 2010]
• Samples w/ detections = 88.4% (404 of 457)
• Detected Conc: Median = 3.15 (j.g/L 99%ile = 55.44 (j.g/L Max = 120.65 (j.g/L
NAWQA Glacial Aquifer Study of Northern U.S. (1991-2003) [Groschen et al, 2009]
• Samples w/ detections = 62.3% (344 of 552), max conc. = 294 ng/L
None.
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January 2021
References
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115 pp. Available from: https://pubs.usgs.gov/sir/2011/5059/pdf/sir2011-5059 report-covers 508.pdf
Blomquist, J.D., J.M. Denis, J.L. Cowles, J.A. Hetrick, R.D. Jones, andN.B. Birchfield. 2001. Pesticides in Selected Water-Supply Reservoirs and Finished Drinking Water, 1999-2000:
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Delzer, G.C. and T. Ivahnenko. 2003. Occurrence and Temporal Variability of Methyl tert-Butyl Ether (MTBE) and Other Volatile Organic Compounds in Select Sources of Drinking Water:
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DeSimone, L.A. 2009. Quality of Water from Domestic Wells in Principal Aquifers of the United States, 1991-2004. U. S. Geological Survey Scientific Investigations Report 2008-5227. 139
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Gilliom, R.J., J.E. Barbash, C.G. Crawford, P.A. Hamilton, J.D. Martin, N. Nakagaki, L.H. Nowell, J.C. Scott, P.E. Stackelberg, G.P. Thelin, and D.M. Wolock. 2007. The Quality of Our
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Glassmeyer, S.T., E.T. Furlong, D.W. Kolpin, A.L. Batt, R. Benson, J. S. Boone, O. Conerly, M.J. Donohue, D.N. King, M.S. Kostich, H.E. Mash, S.L. Pfaller, K.M. Schenck, J.E. Simmons,
E.A. Varughese, S.J. Vesper, E.N. Villegas, and V.S. Wilson. 2017. Nationwide Reconnaissance of Contaminants of Emerging Concern in Source and Treated Drinking Waters of the United
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Grady, S.J. 2003. A National Survey of Methyl tert-Butyl Ether and Other Volatile Organic Compounds in Drinking-Water Sources: Results of the Random Survey. U.S. Geological Survey
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Grady, S.J. and G.D. Casey. 2001. Occurrence and Distribution of Methyl tert-Butyl Ether and Other Volatile Organic Compounds in Drinking Water in the Northeast and Mid-Atlantic
Regions of the United States, 1993-98. U.S. Geological Survey Water-Resources Investigations Report 00-4228. 128 pp. Available on the Internet at:
https://pubs.er.usgs.gov/publication/wri004228.
Groschen, G.E., T.L. Arnold, W.S. Morrow, and K.L. Warner. 2009. Occurrence and Distribution of Iron, Manganese, and Selected Trace Elements in Ground Water in the Glacial Aquifer
System of the Northern United States. U.S. Geological Survey Scientific Investigations Report 2009-5006. 89 pp. Available on the Internet at: http://pubs.usgs.gov/sir/2009/50Q6/.
Hoberman, A.M. (2003) Oral (gavage) developmental neurotoxicity study of acephate technical in Rats. Unpublished report No. 222-022 from Argus Research Laboratories, Inc., Horsham,
PA, USA. Submitted to WHO by Arvesta Corporation, San Francisco, CA, USA.
Hopple, J.A., G.C. Delzer, and J.A. Kingsbury. 2009. Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater, 2002-05. U.S.
Geological Survey Scientific Investigations Report 2009-5200. 74 pp. Available on the Internet at: http://pubs.usgs.gOv/sir/2009/5200/pdf/sir2009-5200.pdf.
HSDB. 2007. Hazardous Substances Data Bank, National Library of Medicine. Profile for Acephate. Last revision date: May 14, 2007. Available for CASRN and Name Search at:
https://toxnet.nlm.nih.gov/newtoxnet/hsdb.htm
HSDB. 2008a. Hazardous Substances Data Bank, National Library of Medicine. Profile for 1,1,1,2-Tetrachloroethane. Last revision date: September 4, 2008. Available for CASRN and Name
Search at: https://toxnet.nlm.nih.gov/newtoxnet/hsdb.htm
HSDB. 2008b. Hazardous Substances Data Bank, National Library of Medicine. Profile for Manganese, Elemental. Last revision date: January 10, 2008. Available for CASRN and Name
Search at: https://toxnet.nlm.nih.gov/newtoxnet/hsdb.htm
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January 2021
References
HSDB. 2008c. Hazardous Substances Data Bank, National Library of Medicine. Profile for Manganese Compounds. Last revision date: January 10,2008. Available for CASRN and Name
Search at: https://toxnet.nlm.nih.gov/newtoxnet/hsdb.htm
HSDB. 2008d. Hazardous Substances Data Bank, National Library of Medicine. Profile for Molybdenum, Elemental. Last revision date: April 25, 2008. Available for CASRN and Name
Search at: https://toxnet.nlm.nih.gov/newtoxnet/hsdb.htm
HSDB. 2008e. Hazardous Substances Data Bank, National Library of Medicine. Profile for Molybdenum Compounds. Last revision date: April 25,2008. Available for CASRN and Name
Search at: https://toxnet.nlm.nih.gov/newtoxnet/hsdb.htm
HSDB. 2016a. Profile for 1,2,3-Trichloropropane; last revised October 25, 2016. Available for search by name or CASRN on the Internet at: https://toxnet.nlm.nih.gov/cgi-
bin/sis/htmlgen?HSDB
HSDB. 2016b. Profile for Vanadium Compounds; last revised October 25, 2016. Available for search by name or CASRN on the Internet at: https://toxnet.nlm.nih.gov/cgi-
bin/sis/htmlgen?HSDB
HSDB. 2017a. Hazardous Substances Data Bank, National Library of Medicine. Profile for alpha-Hexachlorocyclohexane. Last revision date: September 5,2017. Available for CASRN and
Name Search at: https://toxnet.nlm.nih.gov/newtoxnet/hsdb.htm
HSDB. 2017b. Hazardous Substances Data Bank, National Library of Medicine. Profile for Cobalt, Elemental. Last revision date: September 5, 2017. Available for CASRN and Name Search
at: https://toxnet.nlm.nih.gov/newtoxnet/hsdb.htm
HSDB. 2017c. Hazardous Substances Data Bank, National Library of Medicine. Profile for Cobalt Compounds. Last revision date: September 5,2017. Available for CASRN and Name Search
at: https://toxnet.nlm.nih.gov/newtoxnet/hsdb.htm
HSDB. 2018. Hazardous Substances Data Bank, National Library of Medicine. Profile for Aniline. Last revision date: November 28,2018. Available for CASRN and Name Search at:
https://toxnet.nlm.nih.gov/newtoxnet/hsdb.htm
Ito, N., H. Nagasaki, M. Arai, S. Sugihara and S. Makiura. 1973. Histologic and ultrastructural studies on the hepatocarcinogenicity of benzene hexachloride in mice. J. Natl. Cancer Inst. 51(3):
817-826.
Kingsbury, J.A., G.C. Delzer, and J.A. Hopple. 2008. Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams, 2002-05. U.S.
Geological Survey Scientific Investigations Report 2008-5208. 66 pp. Available on the Internet at: http://pubs.usgs.gov/sir/2008/5208/pdf/sir2008-5208.pdf.
Kovalsky, V.V., G.A. Yarovaya andD.M. Shmavonyan. 1961. Changes of purine metabolism in man and animals under conditions of molybdenum biogeochemical provinces. Zh. Obshch.
Biol. 22:179-191. (Russian trans.)
Lindsey, B.D., M.P. Berndt, B.G. Katz, A.F. Ardis, and K.A. Skach. 2008. Factors Affecting Water Quality in Selected Carbonate Aquifers in the United States, 1993-2005. U.S. Geological
Survey Scientific Investigations Report 2008-5240. Available on the Internet at: http://pubs.usgs.gov/sir/2008/5240/.
Moran, M. J., W.W. Lapham, B.L. Rowe, and J.S. Zogorski. 2002. Occurrence and Status of Volatile Organic Compounds in Ground Water from Rural, Untreated, Self-Supplied Domestic
Wells in the United States, 1986-1999. U.S. Geological Survey Water-Resources Investigations Report 02-4085, 51 pp.
National Center for Food and Agricultural Policy (NCFAP). 2000. National Pesticide Use Database. Available on the Internet at: http://www.ncfap.org/pesticide-use. Accessed September 24,
2019.
National Research Council (NRC). 1989. Biologic markers in reproductive toxicology. National Academy of Sciences/National Research Council. Washington, DC: National Academy Press,
15-35.
National Toxicology Program (NTP). 1983. Carcinogenesis studies of 1,1,1,2- tetrachloroethane in F344/N rats and B6C3F1 mice. NTP, Washington, DC.
Roche,M. andM. Layrisse. 1956. Effect of Cobalt on Thyroidal Uptake of 1131. The Journal of Clinical Endocrinology and Metabolism. 16(6): 831-833.
Schroeder, H.A., J.J. Balassa, andl.H. Tipton. 1966. Essential trace metals in man: Manganese. A study in homeostasis. J. Chron. Dis. 19:545-571.
Squillace, P. J., M.J. Moran, W.W. Lapham, C.V. Price, R.M. Clawges, and J.S. Zogorski. 1999. Volatile Organic Compounds in Untreated Ambient Groundwater of the United States, 1985-
1995. Environmental Science and Technology 33(23):4176-4187.
Toccalino, P.L., J.E. Norman, and K.J. Hitt. 2010. Quality of Source Water from Public-supply Wells in the United States, 1993-2007. U.S. Geological Survey Scientific Investigations Report
2010-5024. 206 pp. Available on the Internet at: http://pubs.usgs.gov/sir/2010/5024/.
United States Department of Agriculture (USDA). 2018. Pesticide Data Program (PDP) - Databases and Annual Summaries. Available on the Internet at:
https://www.ams.usda.gov/datasets/pdp/pdpdata. Accessed December 2018.
United States Environmental Protection Agency (USEPA). 1987. Integrated Risk Information System (IRIS) Chemical Assessment Summary for alpha-Hexachlorocyclohexane;
Carcinogenicity Assessment for Lifetime Exposure. Available on the Internet at: https://cfpub.epa.gov/ncea/iris/iris_documents/documents/subst/0162_summary.pdf. Last updated March 31,
1987.
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January 2021
References
USEPA. 1988. Integrated Risk Information System (IRIS) Chemical Assessment Summary for Aniline; Carcinogenicity Assessment for Lifetime Exposure. Available on the Internet at:
https://cfpub.epa.gov/ncea/iris/iris documents/documents/subst/0162 summary.pdf. Last updated September 7,1988.
USEPA. 1989. Integrated Risk Information System (IRIS) Chemical Assessment Summary for 1,1,1,2-Tetrachloroethane; Carcinogenicity Assessment for Lifetime Exposure. Available on the
Internet at: https://cfpub.epa.gov/ncea/iris/iris documents/documents/subst/0265 summary ,pdf#nameddest=woe. Last updated March 1,1989.
USEPA. 1990. National Pesticide Survey: Survey Analytes. Office of Water, Office of Pesticides and Toxic Substances. EPA 570-9-90-NPS2.
USEPA. 1992. Integrated Risk Information System (IRIS) Chemical Assessment Summary for Molybdenum; Carcinogenicity Assessment for Lifetime Exposure. Available on the Internet at:
https://cfpub.epa.gov/ncea/iris/iris documents/documents/subst/0425 summary.pdf. Last updated November 1, 1992.
USEPA. 2001. UCM- State Rounds 1 and 2 (1988 - 1997) Occurrence Data. Available on the Internet at: https://www.epa.gov/dwucmr/occurrence-data-unregulated-contaminant-monitoring-
rule#12.
USEPA. 2004. Drinking Water Health Advisory for Manganese. EPA-822-R-04-003. Available on the Internet at: https://www.epa.gov/sites/production/files/2014-
09/documents/support ccl magnese dwreport O.pdf.
USEPA. 2006. Reregistration Eligibility Decision for Acephate. EPA 738-R-01-013. Office of Pesticide Programs (OPP). Available on the Internet at:
https://archive.epa.gov/pesticides/reregistration/web/pdf/acephate red.pdf.
USEPA. 2007. Provisional Peer Reviewed Toxicity Values for Aniline. EPA/690/R-07/001F. Final. 5-23-2007. Available on the Internet at:
https://cfpub.epa.gov/ncea/pprtv/documents/Aniline.pdf.
USEPA. 2008. Provisional Peer Reviewed Toxicity Values for Cobalt. EPA/690/R-08/008F. Final. 8-25-2008. Available on the Internet at:
https://cfpub.epa.gov/ncea/pprtv/documents/Cobalt.pdf.
USEPA. 2009a. Community Water System Survey 2006, Draft 3.5. EPA 815-R-09-001.
USEPA. 2009b. Provisional Peer Reviewed Toxicity Values for Vanadium and Its Soluble Inorganic Compounds Other Than Vanadium Pentoxide. EPA/690/R-09/070F. Final. 9-30-2009.
Available on the Internet at: https://cfpub.epa.gov/ncea/pprtv/documents/Vanadium.pdf.
USEPA. 2017a. TRI Explorer: Trends. Available on the Internet at: https://enviro.epa.gov/triexplorer/tri_release.trends. Accessed November 2017.
USEPA. 2017b. Third Unregulated Contaminant Monitoring Rule Dataset. Available on the Internet at: https://www.epa.gov/dwucmr/occurrence-data-unregulated-contaminant-monitoring-
rule#3. Accessed January 2017.
USEPA. 2018a. CDR Reporting Requirements. Available on the Internet at: https://www.epa.gov/chemical-data-reporting/how-report-under-chemical-data-reporting. Accessed December
2018.
USEPA. 2018b. Acephate: Revised Draft Human Health Risk Assessment (DRA) in support of Registration Review. March 28, 2018.
Water Quality Portal (WQP). 2017. Water Quality Portal Data Warehouse. Available on the Internet at: https://www.waterqualitydata.us/. Data Warehouse consulted December 2017.
WQP. 2018. Water Quality Portal Data Warehouse. Available on the Internet at: https://www.waterqualitydata.us/. Data Warehouse consulted September 2018.
World Health Organization (WHO). 1973. Trace Elements in Human Nutrition: Manganese. Technical Report Service, 532. World Health Organization, Geneva, Switzerland.
Zogorski, J.S., J.M. Carter, T. Ivahnenko, W.W. Lapham, M.J. Moran, B.L. Rowe, P.J. Squillace, and P.L. Toccalino. 2006. Volatile Organic Compounds in the Nation's Ground Water and
Drinking-Water Supply Wells. USGS Circular 1292. Available on the Internet at: http://pubs.usgs.gov/circ/circl292/pdf/circularl292.pdf.
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EPA - OGWDW Final Regulatory Determination 4 Support Document - Appendix A. Additional Information, Part 2: Legionella and Cyanotoxins
January 2021
Contaminant
Background
Health Effect Findings
Initial Occurrence Findings -
National Drinking Water Data
Legionella pneumophila
• CASRN = NA
• Substance Key = NA
• HRL = None
Background
• Legionella bacteria are found naturally in the environment
worldwide, usually in aquatic environments. The bacteria also
occur in distribution systems and premise plumbing.
• Legionella are ubiquitous in the aquatic environment,
including both natural water bodies and man-made waters.
Research has revealed that Legionella thrive in biofilms, and
interaction with other organisms in biofilms is important for
their survival and proliferation in water (USEPA, 2001).
Critical Health Endpoint
• Legionellosis; Legionnaires' disease; Pontiac fever
Health Assessment Status
•USEPA (2001)
None.
Sensitive Populations/Lifestages
• People > 50 years old
• Current or former smokers
• People with a chronic lung disease
• People with a weakened immune system
Anatoxin-a
• CASRN = 64285-06-9
• Substance Key = 80772
• HRL = None
Background
• An azabicyclo cyanotoxin (a toxin naturally produced and
released by cyanobacteria).
Critical Health Endpoint
• Neurotoxic effects
Health Assessment Status
•USEPA (2015a)
UCMR 4 Assessment Monitoring (2018 -
2020) results forthcoming for the following
cyanotoxins: total microcystins and six
microcystin congeners (-LA, -LF, -LR, -LY, -
RR, and -YR), cylindrospermopsin, anatoxin-a
and nodularin.
Fate / Transport
• Does not sorb well in sandy sediments; stronger sorption can
occur in clay- and organic-rich sediments.
• Degradation of anatoxin-a can occur via a variety of loss
mechanisms. Photolysis is reported to be rapid with half-lives
of 1 to 2 hours reported at pH 8 to 9. Other research indicates
a biodegradation half-life of 5 days; however, little
information is available regarding biodegradation relative to
other cyanobacterial toxins [USEPA, 2015a],
Sensitive Populations/Lifestages
• Undetermined
Cylindrospermopsin
• CASRN = 143545-90-8
• Substance Key = 81115
• Health Advisory (10-day) =
- 0.7 ng/L for bottle-fed infants and
preschoolers
-3.0 (rg/L for school-age children
and adults
Background
• A pyrimidinedione cyanotoxin (a toxin naturally produced
and released by cyanobacteria).
Critical Health Endpoint
• Kidney damage
Health Assessment Status
•USEPA (2015b)
UCMR 4 Assessment Monitoring (2018 -
2020) results forthcoming for the following
cyanotoxins: total microcystins and six
microcystin congeners (-LA, -LF, -LR, -LY, -
RR, and -YR), cylindrospermopsin, anatoxin-a
and nodularin.
Fate / Transport
• Does not sorb significantly to sandy or silty sediments
• Biodegradation under aerobic conditions has a half-life of
2.4 days while under anaerobic conditions, the half-life is 23.6
days. The lack of sorption by cylindrospermopsin may hinder
biodegradation by minimizing contact time with sediment
[USEPA, 2015b]
Sensitive Populations/Lifestages
• Individuals with liver and/or kidney disease, pregnant
woman, nursing mothers, and the elderly population.
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January 2021
Contaminant
Background
Health Effect Findings
Initial Occurrence Findings -
National Drinking Water Data
Total microcystins
• CASRN = N/A
• Substance Key = N/A
• Health Advisory (10-day) =
- 0.3 ng/L for bottle-fed infants and
preschoolers
- 1.6 (rg/L for school-age children
and adults
Background
• An arginine-based cyanotoxin (a toxin naturally produced
and released by cyanobacteria).
Critical Health Endpoint
• Liver damage
Health Assessment Status
•USEPA (2015c)
UCMR 4 Assessment Monitoring (2018 -
2020) results forthcoming for the following
cyanotoxins: total microcystins and six
microcystin congeners (-LA, -LF, -LR, -LY, -
RR, and -YR), cylindrospermopsin, anatoxin-a
and nodularin.
Fate / Transport
• Does not sorb in sandy aquifers but adsorbs to natural
suspended solids.
• A biodegradation half-life of 0.2 to 3.6 days has been
reported for microcystin-LR. Another study involving natural
waters reported persistence for 3 days to 3 weeks, with >95%
loss occurring in the first 3 to 4 days [USEPA, 2015c],
Sensitive Populations/Lifestages
• Individuals with liver and/or kidney disease, pregnant
woman, nursing mothers, and the elderly population.
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EPA - OGWDW Final Regulatory Determination 4 Support Document - Appendix A. Additional Information, Part 2: Legionella and Cyanotoxins January 2021
Contaminant
Initial Occurrence Findings -
Multi-State Drinking Water Studies
Legionella pneumophila
• CASRN = NA
• Substance Key = NA
• HRL = None
Chlorine and Chloramine Impact on the Detection and Quantification of Legionella pneumophila and Mycobacterium Species (2011-2017) [Donohue et al., 2019]
• Between 2011 and 2017, 358 tap water samples were collected from 46 states and territories across the U.S. (210 samples from chlorinated tap water and 148 samples from
chloraminated tap water). Sampling locations had no known association with outbreaks of legionellosis or pulmonary NTM disease and were not statistically selected.
• L. pneumophila was detected in 26% of chlorinated tap water samples and 22% of chloraminated tap water samples. There was no significant difference in detection frequency
in hot-water or cold-water tap samples whether from chlorine- or chloramine-treated water sources.
Monitoring distribution systems for Legionella pneumophila using Legiolert (2017-2018) [LeChevallier, 2019a]
• Based on data from 12 utilities; five sites were along the East coast, four sites in the West, and three sites within the center of the U.S.
• Distribution system samples w/ detections ofL. pneumophila = 0.17% (1 of 576).
• Most systems used their existing Total Coliform Rule (TCR) monitoring locations, but 26 (4.5%) of the 576 distribution system samples were from finished water reservoirs or
storage tanks.
• L. pneumophila was detected in 1 distribution system sample at a concentration of 1 MPN/100 mL. A repeat sample collected a week later was negative for L. pneumophila.
Occurrence of culturable Legionella pneumophila in drinking water distribution systems (2018) [LeChevallier, 2019b]
• Based on data from 10 utilities; five sites were along the East coast, two sites in the West, and three sites within the center of the U.S.
• Distribution system samples w/ detections ofL. pneumophila = 2.4% (14 of 576).
• Most systems used their existing Total Coliform Rule monitoring locations, but at least 36 (6.3%) of the 573 distribution system samples were from finished water reservoirs or
storage tanks.
• L. pneumophila was detected in 14 distribution system samples. Of the 10 systems examined, 5 had at least one positive L. pneumophila sample with an average concentration
(including non-detections) ranging from 0.09 to 14.8 MPN/100 mL. For the 14 distribution systems samples that were positive for L. pneumophila, individual sample
concentrations ranged from 1 to 522 MPN/100 mL.
Molecular Survey of Occurrence and Quantity of Legionella spp., Mycobacterium spp., Pseudomonas aeruginosa and amoeba hosts in municipal drinking water storage tank
sediments (2012-2014) [Lu et al., 2015]
• 87 sediment samples from 18 municipal drinking water storage tanks across 10 states of the United States were collected.
• Legionella spp. was detected in 66.7% of samples.
Anatoxin-a
• CASRN = 64285-06-9
• Substance Key = 80772
• HRL = None
Cyanotoxins in US Drinking Water: Occurrence, Case Studies and State Approaches to Regulation (2010-2015) [AWWA, 2016]
• Anatoxin-a was not detected in any treated drinking water samples.
Cylindrospermopsin
• CASRN = 143545-90-8
• Substance Key = 81115
• Health Advisory (10-day) =
- 0.7 ng/L for bottle-fed infants
and preschoolers
-3.0 (rg/L for school-age
children and adults
Cyanotoxins in US Drinking Water: Occurrence, Case Studies and State Approaches to Regulation (2010-2015) [AWWA, 2016]
• Cylindrospermopsin was not detected in any treated drinking water samples.
Total microcystins
• CASRN = N/A
• Substance Key = N/A
• Health Advisory (10-day) =
- 0.3 (rg/L for bottle-fed infants
and preschoolers
- 1.6 ng/L for school-age
children and adults
Cyanotoxins in US Drinking Water: Occurrence, Case Studies and State Approaches to Regulation (2010-2015) [AWWA, 2016]
• Out of the 3,261 treated water samples collected for cyanotoxins, 2.7% of those were detections. All treated water detections were from Ohio. 1.16% of microcystin treated
drinking water samples in Ohio were greater than 0.3 ng/L.
Assessment of Blue-Green Algal Toxins in Raw and Finished Drinking Water (1996-1998) [AWWARF, 2001]
• Study on the occurrence of cyanobacterial toxins in source and treated drinking waters from 24 PWSs in the U.S. and Canada. Of 677 samples tested, microcystin was found in
80% (539) of the waters sampled. Two samples of finished drinking water were above 1 |ig/L.
Occurrence of microcystins in 33 US water supplies (2003) [Haddix et al., 2007]
• Survey conducted to test for microcystins in 33 U.S. drinking water treatment plants in the northeastern and Midwestern U.S. In 77 finished water samples, microcystins
concentrations ranged from undetectable (<0.15 |ig/L) to 0.36 |ig/L.
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EPA - OGWDW Final Regulatory Determination 4 Support Document - Appendix A. Additional Information, Part 2: Legionella and Cyanotoxins January 2021
Contaminant
Initial Occurrence Findings -
State-Specific Drinking Water Data
Legionella pneumophila
• CASRN = NA
• Substance Key = NA
• HRL = None
Molecular Survey of the Occurrence of Legionella spp., Mycobacterium spp., Pseudomonas aeruginosa, and Amoeba Hosts in Two Chloraminated
Drinking Water Distribution Systems (2010) [Wang et al., 2012]
• Examined the impact of biotic and abiotic factors on the occurrence patterns of Legionella pneumophila, Mycobacterium avium, and Pseudomonas
aeruginosa in two representative chloraminated public water systems. One was located in Virginia; the other was located in Florida.
• Both systems saw high occurrences of mycobacteria (100%) and Legionella (>69%), and lower occurrences of L. pnemophila, M. Avium, and
Pseudomonas aeruginosa.
Longitudinal and Source-to-Tap New Orleans, LA, U.S.A. (2011-2014) [Hull et al., 2017]
• Two municipal drinking water systems of New Orleans, LA were sampled; raw and finished water samples were collected in 2011, 2012, and 2014.
• Although Legionella spp. relative abundances were greater in raw waters, they were found in all finished and tap waters at >1% relative abundance, and
in more than half the taps at >10% relative abundance.
Molecular Detection of Legionella spp. and their associations with Mycobacterium spp., Pseudomonas aeruginosa and amoeba hosts in a drinking water
distribution system (2012-2013 [Lu et al., 2016]
• A total of 41 samples were collected from 6 drinking water distribution system sites between February, 2012 and June, 2013.
• Mycobacterium spp. had the highest frequency of detection (88%), followed by Legionella spp. (57%).
Occurrence of Legionella spp. in Water-Main Biofilms from Two Drinking Water Distribution Systems (2014-2015) [Waak et al., 2018]
• Bacteria and Legionella spp. biofilm presence was compared between a chloraminated distribution system in the US and a Norwegian distribution system
with no residual.
• Legionella spp. was detected in 0 out of 35 chloraminated samples, and 10 of 23 no-residual samples.
Anatoxin-a
• CASRN = 64285-06-9
• Substance Key = 80772
• HRL = None
Oregon (2018)
• In 2018, the City of Salem found low levels of cyanotoxins in treated drinking water (Detroit Reservoir). Multiple "do not drink" advisories were issued
over the course of 6 weeks from late May 2018 to early July 2018 [City of Salem OR, 2018], Levels of anatoxin-a in 22 drinking water samples ranged
from 0.0024 jig/L to 0.0667 (jg/L [Urness et al., 2018],
Washington (2019)
• At Summit Lake, a "do not drink" advisory was issued on April 11, 2019 to warn residents not to drink the lake water. Levels of anatoxin-a were up to 18
Hg/L [Chew, 20191.
Cylindrospermopsin
• CASRN = 143545-90-8
• Substance Key = 81115
• Health Advisory (10-day) =
- 0.7 ng/L for bottle-fed infants and preschoolers
-3.0 ng/L for school-age children and adults
Oregon (2018)
• In 2018, the City of Salem found cylindrospermopsin in treated drinking water (Detroit Reservoir). Multiple "do not drink" advisories were issued over
the course of 6 weeks from late May 2018 to early July 2018 [City of Salem OR, 2018],
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EPA - OGWDW Final Regulatory Determination 4 Support Document - Appendix A. Additional Information, Part 2: Legionella and Cyanotoxins January 2021
Contaminant
Initial Occurrence Findings -
State-Specific Drinking Water Data
Total microcystins
• CASRN = N/A
• Substance Key = N/A
• Health Advisory (10-day) =
- 0.3 ng/L for bottle-fed infants and preschoolers
- 1.6 (rg/L for school-age children and adults
Florida (2000)
• Microcystins were the most commonly found toxin in pre- and post-treated drinking water. Finished water concentrations ranged from undetectable to
12.5 ng/L [Burns, 2008],
Iowa (2016-2018)
• In 2016, microcystin was detected the drinking water of the City of Des Moines below lower health advisory level [Des Moines Water Works, 2016], No
specific concentrations values were reported in this source.
• In 2018, the City of Greenfield issued a "do not drink" advisory due to unusually high turbidity levels in the water. Test results showed that the city did
not have dangerous levels of microcystin [Eller, 2018], No specific concentrations values were reported in this source.
Kansas (2018-2019)
• In 2018, the City of Norton issued an advisory due to a visible bloom on Lake Sebelius. Microcystin levels were as high as 1 jig/L [KDHE, 2018],
• In 2019, the City of Carbondale issued a do not drink advisory due to low levels of microcystins in finished drinking water [Grabauskas, 2019],
New York (2016-2018)
• In 2016, detectable levels of microcystins were found in the treated drinking water from the City of Auburn and the City of Owasco. Levels ranged from
0.16 to 0.121 |ig/L. No advisories issued since levels below EPA's health advisory level [Hannagan, 2016],
• In 2017, blue green algae was reportedly found in samples taken from the Village public drinking water from Skaneateles Lake in Syracuse. The algae
was at levels below heath advisory limits. An advisory was issued in the City of Syracuse for those who draw water from Skaneateles Lake through private
intakes [Village of Skaneateles, 2017], No specific concentrations values were reported in this source.
• In 2018, a "do not drink" advisory was issued for the cities of Rushville and Middlesex. The advisory issued for all consumers due to a visible bloom in
Canandaigua Lake. Microcystin was detected at 0.66 jig/L (NY DOH, 2018).
Ohio (2013 -2019)
• In 2013, Carroll Township, OH shut down its municipal water supplies for two days due to microcystin concentrations greater than 1 (jg/L [Wynne and
Stumpf, 2015],
• In 2014, the City of Toledo issued a two-day "do not drink or boil" advisory due to microcystin concentrations in the city's drinking water above 1 jig/L
[Gebhardt, 2014],
• Finished water data from the Ohio EPA (2019) indicated the following results for microcystin-LR: 0.09% of samples with detections (3 of 3,465); 3.19%
of systems with detections (3 of 94); range of detected concentrations = 0.326 jig/L - 0.493 ng/L.
• Multiple detections in many different Ohio systems from Ohio EPA's database (2010-2015).
Oregon (2018)
• In 2018, the City of Salem found low levels of microcystin in treated drinking water (Detroit Reservoir). Multiple "do not drink" advisories were issued
over the course of 6 weeks from late May 2018 to early July 2018 [City of Salem OR, 2018], Levels of microcystins in 70 drinking water samples ranged
from 0.0021 jig/L to 2.3746 jig/L [Urness et al., 2018],
Texas(2016)
• In 2016, the City of Ingleside issued a 13-day "do not drink" advisory due to detections of microcystin in their drinking water distribution system
[AWWA, 20161. No specific concentrations values were reported in this source.
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EPA - OGWDW Final Regulatory Determination 4 Support Document - Appendix A. Additional Information, Part 2: Legionella and Cyanotoxins January 2021
Contaminant
Initial Occurrence Findings -
Ambient Water
Legionella pneumophila
• CASRN = NA
• Substance Key = NA
• HRL = None
NA
Anatoxin-a
• CASRN = 64285-06-9
• Substance Key = 80772
• HRL = None
Many states monitor for cyanotoxins as part of their monitoring programs. Please see https://www.epa.gov/cyanohabs/state-habs-monitoring-programs-
and-resources for links to individual state monitoring programs. Additional national-level cyanotoxin data can be found in EPA's National Lakes
Assessment Reports from 2007 and 2012 [USEPA, 2009; USEPA, 2016; Loftin et al., 2016],
There have been many documented reports of dog, aquatic life, and livestock illnesses and deaths as a result of the consumption of surface water with
cyanobacterial blooms [e.g., Backer et al., 2013; Hauser, 20191.
Cylindrospermopsin
• CASRN = 143545-90-8
• Substance Key = 81115
• Health Advisory (10-day) =
- 0.7 ng/L for bottle-fed infants and preschoolers
-3.0 (rg/L for school-age children and adults
Many states monitor for cyanotoxins as part of their monitoring programs. Please see https://www.epa.gov/cyanohabs/state-habs-monitoring-programs-
and-resources for links to individual state monitoring programs. Additional national-level cyanotoxin data can be found in EPA's National Lakes
Assessment Reports from 2007 and 2012 [USEPA, 2009; USEPA, 2016; Loftin et al., 2016],
There have been many documented reports of dog, aquatic life, and livestock illnesses and deaths as a result of the consumption of surface water with
cyanobacterial blooms (e.g., Backer et al., 2013; Hauser, 2019). USEPA (2019) has issued recommendations for recreational criteria and swimming
advisories for cylindrospermopsin.
Total microcystins
• CASRN = N/A
• Substance Key = N/A
• Health Advisory (10-day) =
- 0.3 (rg/L for bottle-fed infants and preschoolers
- 1.6 ng/L for school-age children and adults
Many states monitor for cyanotoxins as part of their monitoring programs. Please see https://www.epa.gov/cyanohabs/state-habs-monitoring-programs-
and-resources for links to individual state monitoring programs. Additional national-level data for microcystins can be found in EPA's National Lakes
Assessment Reports from 2007 and 2012 [USEPA, 2009; USEPA, 2016; Loftin et al., 2016],
There have been many documented reports of dog, aquatic life, and livestock illnesses and deaths as a result of the consumption of surface water with
cyanobacterial blooms (e.g., Backer et al., 2013; Hauser, 2019). USEPA (2019) has issued recommendations for recreational criteria and swimming
advisories for microcystins.
A-24
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January 2021
References
American Water Works Association (AWWA). 2016. Cyanotoxins in US Drinking Water: Occurrence, Case Studies and State Approaches to Regulation. September 2016. Available on the
Internet at: https://www.awwa.Org/Portals/0/AWWA/Governrnent/201609_Cyanotoxin_Occurrence_States_Approach.pdl7verf018-12-13-101832-037.
American Water Works Association Research Foundation (AWWARF). 2001. Assessment of Blue-Green Algal Toxins in Raw and Finished Drinking Water. Final report #256. Prepared by
Carmichael, W. W. AWWA Research Foundation and American Water Works Association. Denver, CO.
Backer, L.C. J.H. Landsberg, M. Miller, K. Keel, and T.K. Taylor. 2013. Canine Cyanotoxin Poisonings in the United States (1920s-2012): Review of Suspected and Confirmed Cases from
Three Data Sources. Toxins (Basel). 5(9):1597-1628.
Burns, J. 2008. Toxic cyanobacteria in Florida waters. Adv Exp Med Biol. 619:127-37.
Chew, J. 2019. "Thurston health officials: Toxic algae found in Summit Lake — don't drink the water." iFiberOne NewsRadio. April 11, 2019. Available on the Internet at:
http://www.ifiberonenewsradio.com/news/local_news/thurston-health-officials-toxic-algae-found-in-summit-lake-don/article_76bble2c-5ca0-lle9-84db-b7ed3739flD5.html
City of Salem, OR. 2018. Drinking Water Advisory. Available on the Internet at: https://www.cityofsalem.net/Pages/drinking-water-advisory-may-29.aspx
Des Moines Waterworks. 2016. "Des Moines Waterworks Detects Microcystin in Des Moines Water System." Announcement posted on August 03,2016. Available on the Internet at:
http: //www, dmww. com/ about-us/announcements/advisory. aspx
Donohue, M.J., S. Vesper, J. Mistry, and J.M. Donohue. 2019. Chlorine and Chloramine Impact on the Detection and Quantification of Legionella pneumophila and Mycobacterium Species.
Appl Environ Microbiol. 2019 Oct 11.
Eller, D. 2018. "Greenfield, dropping bottled-water order, requires residents to boil water." Des Moines Register. July 19, 2018. Available on the Internet at:
https://www.desmoinesregister.eom/story/news/2018/07/19/greenfield-water-bottled-order-algae-safe-health-concerns-microcystin/800817002/
Gebhardt, K. 2014. City of Toledo Drinking Water Advisory and Ohio EPA Response to Harmful Algal Blooms. In Proceedings of the Oral Presentation to the Great Lakes Commission
Meeting, Buffalo, NY, USA, 30 September 2014. Available on the Internet at: https://www.glc.org/wp-content/uploads/2016/10/2014-glc-annmtg-Gebhardt-HABDrinkingWaterLakeErie.pdf
Grabauskas, B. 2019. "Carbondale public drinking water notice." WIBW.com. June 21,2019. Available on the Internet at: https://www.wibw.com/content/news/Carbondale-issues-water-
notice-water-not-safe-for-children-under-6-511657851 .html
Haddix. P.L., C.J. Hughley, andM.W. LeChevallier. 2007. Occurrence of microcystins in 33 US water supplies. Journal AWWA. 99(9): 118-125.
Hannagan, C. 2016. "Toxins from blue-green algae blooms found in Auburn, Owasco drinking water." Syracuse.com. September 27,2016. Available on the Internet at:
https://www.syracuse.eom/news/2016/09/toxins_from_blue-green_algae_blooms_in_owasco_lake_found_in_auburn_owasco_water.html
Hauser, C. 2019. "Algae Can Poison Your Dog." New York Times. Aug. 12, 2019. Available on the Internet at: https://www.nytimes.com/2019/08/12/us/blue-green-algae-dogs.html.
Hull, N.M., E.P. Holinger, K.A. Ross, C.E. Robertson, J.K. Harris, M.J. Stevens, and N.R. Pace. 2017. Longitudinal and Source-to-Tap New Orleans, LA, U.S.A. Drinking Water
Microbiology .Environ. Sci. Technol. 51:4220-4229.
Kansas Department of Health and Environment (KDHE). 2018. City of Norton PWS HAB Incident 2018. Available on the Internet at: http://www.kdheks.gov/algae-
illness/2019 Symposium/Dan Wells Norton PWS HAB Presentation.pdf.
LeChevallier, M.W. 2019a. Monitoring distribution systems for Legionella pneumophila using Legiolert. AWWA Water Science. l(l):el 122. January/February 2019.
LeChevallier, M.W. 2019b Occurrence of culturable Legionella pneumophila in drinking water distribution system. AWWA Water Science. l(3):el 139. May/June 2019.
Loftin, K.A., J.L. Graham, E.D. Hilborn, S.C. Lehmann, M.T. Meyer, J.E. Dietze, and C.B. Griffith. 2016. Cyanotoxins in inland lakes of the United States: Occurrence and potential
recreational health risks in the EPA National Lakes Assessment 2007. Harmful Algae. 56: 77-90.
Lu, J., I. Struewing, S. Yelton, and N. Ashbolt. 2015. Molecular survey of occurrence and quantity of Legionella spp., Mycobacterium spp., Pseudomonas aeruginosa and amoeba hosts in
municipal drinking water storage tank sediments. Journal of Applied Microbiology. 119(1 ):278-88.
Lu, J., I. Struewing, E. Vereen, A.E. Kirby, K. Levy, C. Moe, and N. Ashbolt. 2016. Molecular Detection of Legionella spp. and their associations with Mycobacterium spp., Pseudomonas
aeruginosa and amoeba hosts in a drinking water distribution system. Journal of Applied Microbiology. 120(2):509-21.
New York Department of Health (NY DOH). 2018. "New York State Department of Health Recommends Do Not Drink: Blue-green Algae Toxin Detected in Village of Rushville Water
Above Health Advisory Level." Available on the Internet at: https://www.health.ny.gov/press/releases/2018/2018-10-l l_ha_blue_green_algae_toxin_rushville.htm
Ohio Environmental Protection Agency (Ohio EPA). 2019. Harmful Algal Blooms, Algal Toxin Results from Public Water Supplies. Available on the Internet at:
https: //epa. ohio. go v/ddagw/HAB
Urness, Z., T. Loew, and J. Bach. 2018. "Updated July 3: Full test results of Salem's drinking water." Salem Statesman Journal. June 3,2018, Updated July 3, 2018. Available on the Internet at:
https://www.statesmanjournal.eom/story/news/2018/06/03/salem-drinking-water-advisory-test-results/667330002/
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January 2021
References
United States Environmental Protection Agency (USEPA). 2001. Legionella: Drinking Water Health Advisory. Office of Water. EPA-822-B-01-005. Available on the Internet at:
https://www.epa.gov/sites/production/files/2015-10/documents/legionella-report.pdf.
USEPA. 2009. National Lakes Assessment: A Collaborative Survey of the Nation's Lakes. EPA 841-R-09-001. Available on the Internet at: https://www.epa.gov/sites/production/files/2013-
11/documents/nla newlowres fullrpt.pdf.
USEPA. 2015a. Health Effects Support Document for the Cyanobacterial Toxin Anatoxin-A. Office of Water. EPA- 820R15104. June 2015. Available on the Internet at:
https://www.epa.gov/sites/production/files/2017-06/documents/anatoxin-a-report-2015.pdf.
USEPA. 2015b. Drinking Water Health Advisory for the Cyanobacterial Toxin Cylindrospermopsin. Office of Water. EPA- 820R15101. June 2015. Available on the Internet at:
https://www.epa.gov/sites/production/files/2017-06/documents/cylindrospermopsin-report-2015.pdf.
USEPA. 2015c. Drinking Water Health Advisory for the Cyanobacterial Microcystin Toxins. Office of Water. EPA- 820R15100. June 2015. Available on the Internet at:
https://www.epa.gov/sites/production/files/2017-06/documents/microcystins-report-2015.pdf.
USEPA. 2016. National Lakes Assessment 2012: A Collaborative Survey of Lakes in the United States. EPA 841-R-16-113. Available on the Internet at:
https://www.epa.gov/sites/production/files/2016-12/documents/nla report dec 2016.pdf
USEPA. 2019. Recommendations for Cyanobacteria and Cyanotoxin Monitoring in Recreational Waters. Office of Water. EPA 823-R-19-001. Available on the Internet at:
https://www.epa.gov/sites/production/files/2019-09/documents/recommend-cyano-rec-water-2019-update.pdf.
Village of Skaneateles. 2017. Archives of Press Releases from 2017 Blue Green Algae Bloom. Available on the Internet at:
http://www.villageofskaneateles.com/component/content/article/13/51-blue-green-algae-drinking-water-information.html
Waak, M.B., T.M. LaPara, C. Halle, and R.M. Hozalski. 2018. Occurrence of Legionella spp. in Water-Main Biofilms from Two Drinking Water Distribution Systems. Environ. Sci. Technol.
52:7630-7639.
Wang, H., M. Edwards, J.O. Falkinhamlll, and A. Prudena. 2012. Molecular Survey of the Occurrence of Legionella spp., Mycobacterium spp., Pseudomonas aeruginosa, and Amoeba Hosts
in Two Chloraminated Drinking Water Distribution Systems. Applied and Environmental Microbiology. 78(17):6285-6294.
Wynne, T.T. and R.P. Stumpf. 2015. Spatial and temporal patterns in the seasonal distribution of toxic cyanobacteria in Western Lake Erie from 2002-2014. Toxins (Basel). 2015 May 12;7(5).
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Final Regulatory Determination 4 Support Document - App B, 1,4-Dioxane
January 2021
Appendix B:
1,4-Dioxane
An appendix from:
Final Regulatory Determination 4 Support Document
EPA Report 815-R-21-001
B-l
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Final Regulatory Determination 4 Support Document - App B, 1,4-Dioxane
January 2021
Contents
Contents B-2
Exhibits B-3
Abbreviations B-4
B. 1 Contaminant Background and Chemical and Physical Properties B-6
B.2 Sources and Environmental Fate B-7
B.2.1 Production, Use, and Release B-7
B.2.2 Environmental Fate B-ll
B.3 Health Effects B-ll
B.3.1 Toxicokinetics B-ll
B.3.2 Available Health Effects Assessments B-12
B.3.3 Health Effects B-13
B.3.4 Basis of 11RI. B-15
B.3.5 Health Effects Data Gaps B-17
B.4 Occurrence B-18
B.4.1 Occurrence in Ambient Water B-18
B.4.2 Occurrence in Drinking Water B-23
B.4.3 Other Data B-35
B.5 Analytical Methods B-35
B.6 Treatment Technologies B-36
B.7 References B-36
B-2
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Final Regulatory Determination 4 Support Document - App B, 1,4-Dioxane
January 2021
Exhibits
Exhibit B-l: Chemical Structure of 1,4-Dioxane B-6
Exhibit B-2: Physical and Chemical Properties of 1,4-Dioxane B-7
Exhibit B-3: IUR Reported Annual Manufacture and Importation of 1,4-Dioxane in the
United States, 1986-2006 (pounds) B-8
Exhibit B-4: CDR Reported Annual Manufacture and Importation of 1,4-Dioxane in the
United States, 2011-2015 (pounds) B-8
Exhibit B-5: Environmental Releases (in pounds) of 1,4-Dioxane in the United States,
1988-2016 B-9
Exhibit B-6: Summary and State Count of Total Releases and Total Surface Water
Discharges of 1,4-Dioxane, 1988-2016 B-10
Exhibit B-7: Available Health Effects Assessments for 1,4-Dioxane B-13
Exhibit B-8: 1,4-Dioxane NAWQA Data - Summary of Detected Concentrations B-20
Exhibit B-9: 1,4-Dioxane NAWQA Data - Summary of Samples B-20
Exhibit B-10: 1,4-Dioxane NAWQA Data - Summary of Sites B-21
Exhibit B-l 1: 1,4-DioxaneNWIS Data, 1991 -2016 B-22
Exhibit B-12: 1,4-Dioxane STORET Data - Summary of Detected Concentrations B-23
Exhibit B-13: 1,4-Dioxane STORET Data - Summary of Samples and Sites B-23
Exhibit B-14: 1,4-Dioxane STORET Data - Summary of States B-23
Exhibit B-15: 1,4-Dioxane Occurrence Data from UCMR 3 Assessment Monitoring -
Summary of Detected Concentrations B-25
Exhibit B-16: 1,4-Dioxane National Occurrence Measures Based on UCMR 3
Assessment Monitoring Data - Summary of Samples B-26
Exhibit B-17: 1,4-Dioxane National Occurrence Measures Based on UCMR 3
Assessment Monitoring Data - Summary of System and Population Served Data
- Detections B-27
Exhibit B-18: 1,4-Dioxane National Occurrence Measures Based on UCMR 3
Assessment Monitoring Data - Summary of System and Population Served Data
- Detections > V2 the HRL (0.15 |ig/L) B-28
Exhibit B-19: 1,4-Dioxane National Occurrence Measures Based on UCMR 3
Assessment Monitoring Data - Summary of System and Population Served Data
- Detections > HRL (0.3 |ig/L) B-29
Exhibit B-20: 1,4-Dioxane State Drinking Water Occurrence Data - Summary of
Detected Concentrations B-31
Exhibit B-21: 1,4-Dioxane State Drinking Water Occurrence Data - Summary of
Samples B-32
Exhibit B-22: 1,4-Dioxane State Drinking Water Occurrence Data - Summary of
Systems B-33
Exhibit B-23: California State Water Resources Control Board: 1,4-Dioxane Occurrence
(2012-2015) B-3 5
B-3
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Final Regulatory Determination 4 Support Document - App B, 1,4-Dioxane
January 2021
Abbreviations
1,1,1-TCA
1,1,1-Trichl oroethane
AT SDR
Agency for Toxic Substances and Disease Registry
BMD
Benchmark Dose
BMDL
Benchmark Dose Limit
BS
Biodegrades Slowly
BW
Body Weight
CAS
Chemical Abstracts Service
CCL 4
Fourth Contaminant Candidate List
CCR
Consumer Confidence Report
CDC
Centers for Disease Control and Prevention
CDR
Chemical Data Reporting
CRL
Cancer Risk Level
CSF
Cancer Slope Factor
CWSS
Community Water System Survey
CYP450
Cytochrome P450
DWEL
Drinking Water Equivalent Level
DWI
Drinking Water Intake
EPA
Environmental Protection Agency
EPCRA
Emergency Planning and Community Right-to-Know Act
GC/MS
Gas Chromatography/Mass Spectrometry
GLP
Good Laboratory Practice
GWUDI
Groundwater Under the Direct Influence of Surface Water
HA
Health Advisory
HEAA
P-hydroxyethoxyacetic acid
HRL
Health Reference Level
IARC
International Agency for Research on Cancer
ICR
Information Collection Request
IRIS
Integrated Risk Information System
IUR
Inventory Update Reporting
Kh
Henry's Law Constant
Koc
Octanol-Water Partitioning Coefficient
Kow
Organic Carbon Partitioning Coefficient
LCMRL
Lowest Concentration Minimum Reporting Level
LOAEL
Lowest Observed Adverse Effect Level
LOD
Limit of Detection
MOA
Mode of Action
MRL
Minimum Reporting Level
NAWQA
National Water-Quality Assessment
ND
No Detection
NHANES
National Health and Nutrition Examination Survey
NIRS
National Inorganics and Radionuclides Survey
NOAEL
No Observed Adverse Effect Level
NPDWR
National Primary Drinking Water Regulation
NWIS
National Water Information System
OCSPP
Office of Chemical Safety and Pollution Prevention
OECD
Organization for Economic Co-operation and Development
B-4
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Final Regulatory Determination 4 Support Document - App B, 1,4-Dioxane
January 2021
PA
Principal Aquifer
PBPK
Physiologically-Based Pharmacokinetic
PFOA
Perfluorooctanoic Acid
PFOS
Perfluorooctanesulfonic Acid
POD
Point of Departure
PWS
Public Water System
RfD
Reference Dose
RSC
Relative Source Contribution
RSD
Relative Standard Deviation
SDWIS/Fed
Safe Drinking Water Information System/Federal Version
SIM
Selective Ion Monitoring
SPE
Solid Phase Extraction
STORET
Storage and Retrieval Data System
SWRCB
State Water Resources Control Board
SYR2
Second Six-Year Review
SYR3
Third Six-Year Review
TDI
Tolerable Daily Intake
TRI
Toxics Release Inventory
TSCA
Toxic Substances Control Act
UCM
Unregulated Contaminant Monitoring
UCMR
Unregulated Contaminant Monitoring Rule
UC MR 1
First Unregulated Contaminant Monitoring Rule
UCMR 2
Second Unregulated Contaminant Monitoring Rule
UCMR 3
Third Unregulated Contaminant Monitoring Rule
UF
Uncertainty Factor
USGS
United States Geological Survey
UV
Ultraviolet
WHO
World Health Organization
WQP
Water Quality Portal
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Appendix B: 1,4-Dioxane
The Environmental Protection Agency (EPA) evaluated 1,4-dioxane as a candidate for
regulation as a drinking water contaminant under the fourth Contaminant Candidate List (CCL 4)
Regulatory Determinations process. Information on the CCL 4 process is found in Chapter 1.
Background on data sources used to evaluate CCL 4 chemicals is found in Chapter 2.
This appendix presents information and analyses specific to 1,4-dioxane, including
background information on the contaminant, information on contaminant sources and
environmental fate, an analysis of health effects, an analysis of occurrence in ambient and
drinking water, and information about the availability of analytical methods and treatment
technologies. EPA is not making a regulatory determination for 1,4-dioxane at this time.
B.l Contaminant Background and Chemical and Physical Properties
1,4-Dioxane is a cyclic aliphatic ether that is used as a solvent and a solvent stabilizer. As
a solvent it is used in such products as inks, coatings, adhesives, oils, resins, waxes, and dyes
(HSDB, 2015). Nearly 90 percent of past production of 1,4-dioxane was used for stabilization of
chlorinated solvents (ATSDR, 2012). One such use, in 1,1,1-trichloroethane (1,1,1-TCA), was
eliminated in the 1990s due to phase out of 1,1,1-TCA production in the U.S. in accordance with
the Clean Air Act and the Montreal Protocol (HSDB, 2015). Use as a stabilizer in other
chlorinated solvents may still be in practice. It is also found as a trace contaminant in consumer
products such as cosmetics and shampoos and in certain foods (ATSDR, 2012).
Synonyms for 1,4-dioxane include /Jc/ra-dioxane, 1,4-diethylene dioxide, di(ethylene
oxide), dioxane, diethylene dioxide, diethylene ether, and glycol ethylene ether (HSDB, 2015).
Exhibit B-l presents the structural formula for 1,4-dioxane. Physical and chemical
properties and other reference information are listed in Exhibit B-2.
Exhibit B-1: Chemical Structure of 1,4-Dioxane
(
o
Source: USEPA, 2019a
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Exhibit B-2: Physical and Chemical Properties of 1,4-Dioxane
Property
Data
Chemical Abstracts Service (CAS)
Registry Number
123-91-1 (ChemlDPIus, 2018)
EPA Pesticide Chemical Code
Not applicable
Chemical Formula
C4H802 (ChemlDPIus, 2018)
Molecular Weight
88.106 g/mol (HSDB, 2015)
Color/Physical State
Colorless liquid or solid (below 53°F (11.7 °C)) (HSDB, 2015)
Boiling Point
101.2 °C (HSDB, 2015)
Melting Point
11.75 °C (HSDB, 2015)
Density
1.0337 g/mL at 20° C (HSDB, 2015)
Freundlich Adsorption Coefficient
-
Vapor Pressure
38.1 mm Hg at 25° C (HSDB, 2015)
Henry's Law Constant (Kh)
4.8E-06 atm-m3/mol at 25° C (HSDB, 2015; ChemlDPIus, 2018)
Log Kow
-0.27 (dimensionless) (HSDB, 2015)
Koc
17 and 29 L/kg (HSDB, 2015)
Solubility in Water
Miscible (ATSDR, 2012)
Other Solvents
Miscible with most organic solvents including aromatic hydrocarbons and
oils (HSDB, 2015)
Conversion Factors
(at 25° C, 1 atm)
1 ppm (v/v) = 0.278 mg/m3
1 mg/m3 = 3.60 ppm (v/v)
(calculated)
Note:indicates that no information was found.
Note: Many of these properties are temperature-dependent. Values are given for properties at 20-25°C unless
otherwise noted. Due to varying experimental conditions, and due to the variabilities associated with modeling, the
standard information sources may provide a range of values. Where more than one value was available from these
sources, one value was selected for this table based on best professional judgment.
B.2 Sources and Environmental Fate
B.2.1 Production, Use, and Release
Production data for 1,4-dioxane are available from EPA's Inventory Update Reporting
(IUR) and Chemical Data Reporting (CDR) programs, and industrial release data are available
from EPA's Toxics Release Inventory (TRI), as described below. Additional information about
these sources is provided in Chapter 2.
Inventory Update Reporting (IUR) / Chemical Data Reporting (CDR) Program
Under the authority of the Toxic Substances Control Act (TSCA), EPA gathers
information on production (including both manufacture and importation) of industrial chemicals.
Under the IUR, producers provided information once every four years from 1986 to 2006. Since
2012, producers have continued to provide information in accordance with the CDR Rule that
superseded the IUR in 2011. Under CDR, producers collect annual production data and report it
once every four years.
Until 2006, the IUR regulation required manufacturers and importers of organic chemical
substances included on the TSCA Chemical Substance Inventory to report site and
manufacturing information for chemicals produced (i.e., manufactured or imported) in amounts
of 10,000 pounds or more at a single site. In 2006, the minimum threshold for reporting was
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increased to 25,000 pounds and reporting began for inorganic chemicals (USEPA, 2008a).
Among changes made under CDR, a two-tier system of reporting thresholds was implemented,
with 25,000 pounds as the threshold for some contaminants and 2,500 pounds as the threshold
for others (USEPA, 2014; USEPA, 2018a). As a result of program modifications, the results
from 2006 and later might not be directly comparable to results from earlier years. Under CDR,
every four years manufacturers and importers are required to report annual data from each of the
previous four years, provided that the thresholds of 2,500 or 25,000 pounds are met during at
least one of the four years (USEPA, 2018a).
For the historical IUR data, EPA assigned one of eight production volume ranges for
each chemical included in the inventory. The ranges used for the 2006 reports differ slightly
from those used in the 1986 through 2002 reports, as described in Chapter 2. Exhibit B-3
presents the publicly available information on production of 1,4-dioxane in the United States
from 1986 to 2006 as reported under IUR. Reported production of 1,4-dioxane in the United
States decreased between 1990 and 1994 and then remained within the range of 1 million to 10
million pounds.
Exhibit B-4 presents the publicly available production data for 1,4-dioxane in the United
States from 2011 to 2015 as reported under CDR. Reported annual production of 1,4-dioxane has
fluctuated, with the highest amounts (in the range of 1 million to 10 million pounds) reported in
2013 and 2015.
Exhibit B-3: IUR Reported Annual Manufacture and Importation of 1,4-Dioxane in
the United States, 1986-2006 (pounds)
Chemical Inventory Update Reporting Cycle
1986
1990
1994
1998
2002
2006
Range of
Production /
Importation
Volume
> 10 million -
50 million
> 10 million -
50 million
> 1 million -
10 million
> 1 million -
10 million
> 1 million -
10 million
1 million - < 10
million
Source: USEPA, 2008a
Exhibit B-4: CDR Reported Annual Manufacture and Importation of 1,4-Dioxane in
the United States, 2011-2015 (pounds)
Chemical Inventory Update Re
porting Cycle
2011
2012
2013
2014
2015
Range of Production /
Importation Volume
Withheld
500,000 -1
million
1 million -10
million
100,000-
500,000
1 million -10
million
"Withheld" = results not publicly available due to confidential business information.
Source: USEPA, 2018a
Toxics Release Inventory (TRI)
EPA established TRI in 1987 in response to section 313 of the Emergency Planning and
Community Right-to-Know Act (EPCRA). EPCRA section 313 requires the reporting of annual
information on toxic chemical releases from facilities that meet specific criteria. This reported
information is maintained in a database accessible through TRI Explorer (USEPA, 2017a).
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Although TRI can provide a general idea of release trends, it has limitations. Not all
facilities are required to report all releases. Facilities are required to report releases if they
manufacture or process more than 25,000 pounds of a chemical or use more than 10,000 pounds
per year. Reporting requirements have changed over time (e.g., reporting thresholds have
decreased), so conclusions about temporal trends should be drawn with caution. TRI data are
meant to reflect releases and should not be used to estimate general public exposure to a
chemical (USEPA, 2019b).
TRI data for 1,4-dioxane for the years 1988 through 2016 are summarized in Exhibit B-5
(USEPA, 2017a). On-site air emissions and on-site surface water releases made up the bulk of
releases in the early reporting years, and both declined over time from ranges in the hundreds of
thousands of pounds to ranges in the tens of thousands of pounds. On-site underground injections
were negligible until around 2005, from which time they have ranged in the tens and hundreds of
thousands of pounds. From the mid-1990s onward, off-site releases have also frequently ranged
in the hundreds of thousands of pounds.
Exhibit B-5: Environmental Releases (in pounds) of 1,4-Dioxane in the United
States, 1988-2016
Year
On-Site Releases (in pounds)
Total Off-
Site
Releases
(in pounds)
Total On-
and Off-Site
Releases
(in pounds)
Air
Emissions
Surface
Water
Discharges
Underground
Injection
Releases to
Land
1988
612,633
203,320
0
11,702
10,954
838,609
1989
841,790
273,523
0
33,723
3,476
1,152,512
1990
663,571
303,856
0
12,549
13,602
993,578
1991
753,350
318,133
0
15,952
76,539
1,163,974
1992
684,758
447,066
0
3,297
47,275
1,182,396
1993
580,436
652,296
0
2,236
61,762
1,296,730
1994
230,919
305,771
0
2,266
16,115
555,071
1995
223,144
216,689
0
5,736
352,998
798,567
1996
120,869
226,998
0
5,409
479,390
832,666
1997
118,375
196,272
0
4,609
305,803
625,059
1998
112,597
144,534
250
14,405
478,141
749,927
1999
164,883
168,128
250
52,972
666,121
1,052,354
2000
107,515
163,776
0
18,131
357,657
647,079
2001
112,584
84,778
0
63,135
678,752
939,249
2002
106,400
75,119
0
1,902
964,136
1,147,557
2003
143,448
73,690
0
48
83,318
300,504
2004
116,993
75,123
0
2
616,543
808,661
2005
128,610
80,872
105,826
2
133,572
448,883
2006
127,117
49,035
141,288
1
796
318,237
2007
125,383
56,996
332,838
2
2,794
518,012
2008
95,880
41,014
118,665
2
66,937
322,497
2009
69,386
45,146
54,416
229
136,034
305,210
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Year
On-Site Releases (in pounds)
Total Off-
Site
Releases
(in pounds)
Total On-
and Off-Site
Releases
(in pounds)
Air
Emissions
Surface
Water
Discharges
Underground
Injection
Releases to
Land
2010
95,396
23,007
133,684
15,349
425,339
692,775
2011
99,094
43,377
375,568
61,567
307,709
887,317
2012
89,169
57,341
349,146
6
336,572
832,234
2013
102,034
49,901
371,878
15,400
442,203
981,416
2014
96,477
51,224
731,892
16,115
422,943
1,318,651
2015
62,610
56,935
94,304
13,422
469,674
696,946
2016
55,732
61,907
12,867
503
486,124
617,134
Source: USEPA, 2017a
Exhibit B-6 presents an expanded summary of total releases and total surface water
discharges that includes the count of states reporting releases for the years 1988 through 2016
(USEPA, 2017a). The number of states reporting any releases of 1,4-dioxane ranged from 15 to
27 over the years 1988-2016. The number of states reporting surface water discharges of 1,4-
dioxane ranged from six to ten during these years. (For the purposes of TRI, "state" counts
include the District of Columbia and United States territories in addition to the 50 states.)
Exhibit B-6: Summary and State Count of Total Releases and Total Surface Water
Discharges of 1,4-Dioxane, 1988-2016
Year
Total Release
(in pounds)
Count of States
with Releases
Total Surface
Water
Discharges
(in pounds)
Count of States
with Surface
Water
Discharges
1988
838,609
26
203,320
6
1989
1,152,512
27
273,523
7
1990
993,578
26
303,856
8
1991
1,163,974
24
318,133
9
1992
1,182,396
27
447,066
9
1993
1,296,730
20
652,296
8
1994
555,071
16
305,771
7
1995
798,567
15
216,689
7
1996
832,666
15
226,998
8
1997
625,059
16
196,272
7
1998
749,927
21
144,534
8
1999
1,052,354
23
168,128
10
2000
647,079
24
163,776
9
2001
939,249
23
84,778
9
2002
1,147,557
23
75,119
9
2003
300,504
24
73,690
9
2004
808,661
23
75,123
7
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Year
Total Release
(in pounds)
Count of States
with Releases
Total Surface
Water
Discharges
(in pounds)
Count of States
with Surface
Water
Discharges
2005
448,883
20
80,872
9
2006
318,237
20
49,035
7
2007
518,012
19
56,996
7
2008
322,497
20
41,014
7
2009
305,210
19
45,146
8
2010
692,775
16
23,007
7
2011
887,317
19
43,377
7
2012
832,234
17
57,341
7
2013
981,416
21
49,901
7
2014
1,318,651
22
51,224
7
2015
696,946
23
56,935
6
2016
617,134
23
61,907
6
Source: USEPA, 2017a
B.2.2 Environmental Fate
As discussed in Chapter 2, the measures used by EPA to assess mobility include (where
available) the organic carbon partitioning coefficient (Koc), log octanol-water partitioning
coefficient (log Kow), Henry's Law Constant (Kh), water solubility, and vapor pressure. A vapor
pressure of 38.1 mm Hg at 25 degrees C indicates that if 1,4-dioxane is released to air, the
contaminant will exist entirely in the vapor phase. Koc values of 17 and 29 L/kg suggest that 1,4-
dioxane will be very mobile in soil and will not sorb to sediment. The vapor pressure and a Kh of
4.8E-06 atm-m3/mol suggest that volatilization will be a significant pathway from dry soils,
moist soils, and water. Half-lives of 7.3 and 56 days were calculated for loss by volatilization
from a model river and a model lake, respectively. 1,4-Dioxane is considered recalcitrant and is
not likely to degrade by microbial degradation, photolysis, or hydrolysis (HSDB, 2015). EPA has
concluded that 1,4,-dioxane does not readily biodegrade in the environment (USEPA, 2006).
Chapter 2 presents scales used by EPA to informally rank chemical contaminants' likely
mobility (understood as their tendency to partition to water rather than other media) and
persistence as "high," "moderate," or "low" based on physical and chemical properties (see
Exhibit 2-2 and Exhibit 2-3). For 1,4-dioxane, a Kh of 4.8E-06 atm-m3/mol predicts a moderate
likelihood of partitioning to water. Koc values of 17 and 29 L/kg, a log Kow of -0.27, and
miscibility with water predict a high likelihood of partitioning to water. A qualitative
biodegradation rate of BS (biodegrades slowly) was developed by modeling performed as part of
CCL 3. This qualitative rate indicates moderate persistence.
B.3 Health Effects
B.3.1 Toxicokinetics
No data are available on the toxicokinetics of 1,4-dioxane in humans after oral exposure;
limited are data available for inhalation exposure. A maximum of 80 percent absorption was
detected in humans following administration of 1,4-dioxane via inhalation (WHO, 2005). Data
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from adult male volunteers exposed to 50 ppm 1,4-dioxane for six hours (total dose equaling 5.4
mg/kg) via inhalation indicated initial, rapid absorption with plasma levels of 1,4 dioxane
nearing steady state after six hours (USEPA, 2013).
Once absorbed and distributed, 1,4-dioxane is readily metabolized and does not
accumulate in the body (IARC, 1999). 1,4-Dioxane is readily metabolized to P-
hydroxyethoxyacetic acid (HEAA) in humans (ATSDR, 2012). Other metabolites, such as 1,4-
dioxane-2-one, have also been reported; however, the presence of l,4-dioxane-2-one may have
been due to analytical methods carried out under acidic conditions (USEPA, 1987; USEPA,
2013).
The half-life for elimination of 1,4-dioxane from plasma was 59 minutes, and the half-life
for elimination of 1,4-dioxane elimination in urine was 48 minutes. HEAA plasma levels peaked
1 hour after exposure ended (ATSDR, 2012). 1,4-Dioxane is predominantly excreted in the urine
as HEAA (IARC, 1999; USEPA, 2013).
Absorption, distribution, metabolism, and elimination of 1,4-dioxane are well described
in rats (USEPA, 2013). In rats, more than 95 percent of orally administered 1,4-dioxane is
absorbed through the gastrointestinal tract at doses of up to 1,000 mg/kg body weight (WHO,
2005). In vitro studies indicate poor absorption through human skin, as only 3.2 percent of the
applied dose passed through excised human skin in occluded conditions and 0.3 percent passed
under non-occluded conditions (USEPA, 2013; IARC, 1999). In a dermal absorption study using
[14C]-l,4-dioxane in primates, approximately 3 percent of the original radiolabel was absorbed
over a 24-hour period under non-occluded conditions (USEPA, 2013; WHO, 2005).
Animal studies demonstrate that 1,4-dioxane is rapidly distributed to the blood, liver,
kidney, spleen, lung, colon, skeletal muscle, and other tissues (USEPA, 2013; WHO, 2005).
Injection of rats with radiolabeled 1,4-dioxane results in wide, generally uniform distribution of
1,4-dioxane-derived radioactivity across tissues (ATSDR, 2012; USEPA, 2013).
Available data from rat studies (Young, 1978a; Young, 1978b) indicate that metabolism
of 1,4-dioxane is a saturable process in which increases in dose result in a larger percentage of
the total dose expired in air and a smaller percentage excreted in urine (USEPA, 2013; ATSDR,
2012). The clearance rate decreased from 2.82 mL/min after exposure to a single intravenous
injection of 10 mg/kg [14C]-1,4-dioxane to 0.17 mL/min after exposure to an additional injection
of 1,000 mg/kg [14C]- 1,4-dioxane (ATSDR, 2012). A similar pattern was observed in rats given
gavage doses of [14C]- 1,4-dioxane, with greater urinary elimination of the radiolabel observed at
the lower dose (10 mg/kg) than at the higher dose (1,000 mg/kg), while expiration of the
radiolabel to air increased at the higher dose; about 2 percent of the radiolabel was eliminated in
feces regardless of the dose level or frequency of dosing (USEPA, 2013). Evidence for the
saturable nature of 1,4-dioxane metabolism was also found in rat studies by Woo et al. (1977a;
1977b).
Physiologically-based pharmacokinetic (PBPK) models have been described for 1,4-
dioxane in rats, mice, and humans, including lactating women (USEPA, 2013).
B.3.2 Available Health Effects Assessments
Exhibit B-7 presents a summary of the available health effects assessments for 1,4-
dioxane. As indicated by the bolded row, the 2010 and 2013 IRIS Assessments (USEPA, 2010;
USEPA, 2013) were selected for use in the calculation of the Health Reference Level (HRL) (see
Section B.3.4 below for details on that calculation).
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Exhibit B-7: Available Health Effects Assessments for 1,4-Dioxane
Health
Assessment
Assessment
Year
RfD
(mg/kg/day)
Principal
Study for RfD
CSF
(mg/kg/day)"1
Principal
study for
CSF
Cancer Descriptor
EPA Health
Advisory
1987
No value
NA
No value
NA
B2 (probable
human carcinogen)
WHO
2005
9.6 x 10"2
Kociba et al.
1974
1.6 x 10"2
Yamazaki et
al. 1994
2B (possibly
carcinogenic to
humans)
ATSDR
2012
0.1
Kociba et al.
1974
No value
NA
No value
EPA IRIS
2010 for RfD;
2013 for CSF
0.03
Kociba et al.
1974
0.10
Kano et al.
2009
Likely to Be
Carcinogenic to
Humans
B.3.3 Health Effects
Systemic (Noncancer)
Most of the available health effects information for 1,4-dioxane in humans are from case
reports of workers or volunteers exposed dermally and via inhalation (USEPA 2013; ATSDR
2012). Several cases of death in humans have been documented after inhalation exposure to high
concentrations of 1,4-dioxane. Additionally, liver, kidney, respiratory and neurological effects
have been reported in these human studies. In animals, liver and kidney toxicity are the primary
effects observed following both oral and inhalation exposures (USEPA 2013). Inhalation studies
also demonstrate nasal toxicity as a major noncancer health effect (USEPA, 2013). Studies in
humans evaluating cancer are limited by small sample size and number of reported cases. There
are several cancer studies (both oral and inhalation) in multiple strains and species of rodents
reporting tumors in the peritoneum, mammary gland, liver, kidney, skin, Zymbal gland, nasal
tissue, and lung (USEPA, 2013).
EPA's Office of Water developed health advisories (HAs) for one-day and ten-day
exposures to 1,4-dioxane in 1987 (USEPA, 1987). The Fairley et al. (1934) study was selected
for calculating a one-day HA of 4.12 mg/L for a 10 kg child, based on the lowest-observed-
adverse-effect level (LOAEL) at the 1 mL dose for liver and kidney effects in rabbits. In this
study, a single dose (1, 2, 3, or 5 mL) of 1,4-dioxane (with a density of 1.03 g/mL) was given
intravenously to rabbits. Degeneration of the renal cortices and extensive and gross cellular
degeneration of the liver was observed when the rabbits were necropsied one month later. In the
absence of an acceptable study for the derivation of a ten-day HA, the one-day HA was divided
by 10 to calculate an estimated ten-day HA of 0.412 mg/L (USEPA, 1987). A lifetime HA was
not recommended for 1,4-dioxane due to its suspected carcinogenicity. 1,4-Dioxane was
classified as a Group B2 probable human carcinogen using the criteria described in EPA's
Guidelines for Carcinogenic Risk Assessment (USEPA, 1986) at the time of the HA publication
(USEPA, 1987).
Kociba et al. (1974) served as the critical study for noncancer health assessments by EPA
(2010, 2013), the World Health Organization (WHO) (2005), and the Agency for Toxic
Substances and Disease Registry (ATSDR) (2012). In this study, groups of male and female
Sherman rats were exposed to 0.01, 0.1, or 1.0 percent 1,4-dioxane in drinking water for up to
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716 days. The LOAEL and no-observed-adverse-effect level (NOAEL) of 94 mg/kg/day and 9.6
mg/kg/day, respectively, were determined from this study based on liver and kidney effects in
male rats (USEPA, 2010; USEPA, 2013). Approximately half of the animals in the 1.0 percent
1,4-dioxane treatment group had died by 16 months of exposure and histopathological analysis
revealed degenerative and necrotic alterations in liver parenchyma and renal tubules (IARC
1999).
WHO used the NOAEL of 9.6 mg/kg/day identified in Kociba et al. (1974) to derive a
noncancer guideline value for 1,4-dioxane based on renal tubular epithelial and hepatocellular
degeneration and necrosis in rats. The tolerable daily intake (TDI) of 96 [j,g/kg/day for 1,4-
dioxane was calculated by dividing the NOAEL by a composite uncertainty factor (UF) of 100 to
account for inter- and intraspecies variation.
The EPA Integrated Risk Information System (IRIS) derived an oral reference dose
(RfD) for 1,4-dioxane of 0.03 mg/kg/day. This value too is based on the Kociba (1974) study. To
the NOAEL of 9.6 mg/kg/day EPA applied a composite UF of 300 to account for
pharmacokinetic and pharmacodynamic differences between rats and humans (10),
interindividual variability (10), and database deficiencies (3) (USEPA, 2010; USEPA, 2013).
The RfD derived by EPA IRIS was used to calculate a lifetime HA of 0.2 mg/L for 1,4-
dioxane. The lifetime HA was calculated based on a Drinking Water Equivalent Level (DWEL)
of 1 mg/L, which was derived from the RfD of 0.03 mg/kg/day assuming a body weight of 70 kg
and a drinking water intake of 2 liters per day (L/day) for adults, and assuming a relative source
contribution (RSC) of 20 percent of total exposure from drinking water (USEPA, 2018b).
Similarly, ATSDR derived a chronic-duration oral minimal risk level of 0.1 mg/kg/day
from the NOAEL identified in Kociba et al. (1974). ATSDR divided the NOAEL of 9.6
mg/kg/day by a composite UF of 100 to account for animal to human extrapolation (10) and
human variability (10); the resulting value was then rounded to one significant figure to calculate
the minimal risk level (ATSDR, 2012).
Developmental/Reproductive
There currently are no reproductive studies available for 1,4-dioxane (ATSDR, 2012).
One developmental study evaluated effects of 1,4-dioxane exposure to pregnant Sprague-Dawley
rats by gavage in water on days 6-15 of gestation and found no effect on implantation numbers,
live fetuses, post-implantation loss, or rate of malformations in the 0.25 and 0.5 mL/kg dose
groups (equivalent to dose estimates of 250 and 500 mg/kg/day, respectively). Fetal toxicity
(decreased body weight, delayed ossification of sternebrae) and slight maternal toxicity
(decreased body weight gain) were observed in animals dosed with 1 mL/kg 1,4-dioxane
(equivalent to a dose estimate of 1 mg/kg/day) (USEPA, 2013; IARC, 1999; WHO, 2005). EPA
identified NOAEL and LOAEL values of 500 and 1,000 mg/kg/day, respectively, from this
study, based on delayed ossification of the sternebrae and reduced fetal body weights (USEPA,
2013).
Cancer Data and Classification
There is limited information concerning human exposure to 1,4-dioxane and cancer.
Studies in humans are limited by cohort size and the small number of reported cancer cases
(USEPA, 2010; USEPA, 2013). A prospective mortality study evaluating death from cancer in
workers exposed to low concentrations (0.1 to 17 ppm) of 1,4- dioxane for up to 21 years found
no significant increases in the incidence of death due to cancer (ATSDR, 2012; IARC, 1999). In
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rodents, hepatic, nasal cavity, peritoneal, and mammary gland tumors were reported in long-term
oral exposure studies (USEPA, 2013). Tumors in the skin and lung have also been reported in
rodents exposed to 1,4-dioxane (WHO, 2005).
The International Agency for Research on Cancer (IARC) determined there was
sufficient evidence in experimental animals and inadequate evidence in humans for the
carcinogenicity of 1,4-dioxane and classified 1,4-dioxane as a Group 2B carcinogen (possibly
carcinogenic to humans) (IARC, 1982; IARC 1999). In EPA's 1987 HA, the IARC Group 2B
cancer classification was cited in the evaluation of the carcinogenic potential of 1,4-dioxane. In
addition, it was noted that 1,4-dioxane may be classified as a Group B2 carcinogen (USEPA,
1987). EPA recommended a linearized multistage model for estimating carcinogenic risk in the
1987 HA (USEPA, 1987).
WHO derived a TDI of 1.6 x 10"2 mg/kg/day using a NOAEL of 16 mg/kg/day for
hepatocellular tumors observed in a long-term drinking water study in rats. The TDI was
calculated by dividing the NOAEL by a composite UF of 1000 to account for interspecies
variation (10), intraspecies variation (10), and non-genotoxic carcinogenicity (10) (WHO, 2005).
EPA IRIS (USEPA, 2010; USEPA, 2013) classified 1,4-dioxane as a probable human
carcinogen (Group B2) based on inadequate evidence or no data from human epidemiology
studies and sufficient evidence of carcinogenicity in animals in accordance with EPA's 1986
Guidelines for Carcinogenic Risk Assessment (USEPA, 1986). In 2013, IRIS (USEPA, 2013)
classified 1,4-dioxane as "likely to be carcinogenic to humans" in accordance with EPA's 2005
Guidelines for Carcinogenic Risk Assessment (USEPA, 2005), based on evidence of
carcinogenicity in two-year studies performed with three strains of rats, two strains of mice, and
guinea pigs.
Potentially Sensitive Groups/Lifestages
Metabolism of 1,4-dioxane appears to be mediated by the cytochrome P450 (CYP450)
enzyme system (USEPA, 2013). It is possible that variations in CYP450 enzyme expression and
function may result in increased susceptibility to 1,4-dioxane effects. Individuals with pre-
existing conditions affecting target organs such as the liver and kidneys may also be more
susceptible.
It is not known whether 1,4-dioxane can cross the placenta and there are no known
studies of whether 1,4-dioxane can be transferred through breastmilk from mother to offspring
(ATSDR, 2012). No human studies were found evaluating in utero or maternal effects in
humans. However, there is evidence to suggest in utero (decreased body weight, delayed
ossification of sternebrae) as well as maternal sensitivity (decreased body weight gain) to 1,4-
dioxane toxicity in rats (USEPA, 2013; IARC, 1999; WHO, 2005).
In addition, there are no studies currently available that specifically address the health
effects of exposure to 1,4-dioxane in children or in immature animals. It is therefore unknown
whether children are more susceptible than adults to health effects from 1,4-dioxane (ATSDR,
2012; USEPA, 2013).
B.3.4 Basis of HRL
For the health reference level (HRL) derivation, EPA selected the oral cancer slope factor
(CSF) of 0.10 (mg/kg/day)"1 for 1,4-dioxane derived by EPA IRIS for hepatocellular adenomas
or carcinomas in female mice (USEPA, 2013). The principal study selected for the derivation of
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the CSF was Kano et al. (2009).1. In this study, conducted by the Japanese Bioassay Research
Center, groups of 6-week old F344/DuCrj rats (50 per sex at each dose level) and Cij:BDFl mice
(50 per sex at each dose level) were administered 1,4-dioxane in drinking water for two years.
Based on daily water intake rates, the investigators calculated the doses to be: 0, 11 ± 1, 55 ± 3,
and 274 ±18 mg/kg/day for male rats; 0, 18 ± 3, 83 ± 14, and 429 ± 69 mg/kg/day for female
rats; 0, 49 ± 5, 191 ± 21, and 677 ± 74 mg/kg/day for male mice; and 0, 66 ± 10, 278 ± 40, and
964 ± 88 mg/kg/day for female mice.
Although two other chronic drinking water studies (Kociba et al., 1974; NCI, 1978)
provided liver tumor incidence data, Kano et al. (2009) was selected as the principal study for
derivation of the oral CSF because it had three dose groups and characterized the dose-response
relationship at lower exposure levels than the other chronic studies. Kano et al. (2009) also
reported the incidence of both hepatocellular carcinomas and adenomas, unlike the Kociba et al.
(1974) study, in which only the incidence of hepatocellular carcinomas was reported.
Additionally, the Kano et al. (2009) study was conducted in accordance with the Organization
for Economic Co-operation and Development (OECD) Principles for Good Laboratory Practice
(GLP) (USEPA, 2013).
This study reported an increased incidence of hepatocellular adenomas and carcinomas
and tumors of the nasal cavity in high-dose male and female rats. High-dose male rats also
displayed a significant increase in mesotheliomas of the peritoneum. Male rats showed an
increasing trend in mammary gland fibroadenoma and fibroma of the subcutis, and female rats
showed an increasing trend in mammary gland adenomas. An increased incidence of liver tumor
formation was also observed in male and female mice. There was an increasing trend in
hepatocellular carcinoma and/or adenoma incidence in low-, mid-, and high-dose male mice. The
incidence of hepatocellular carcinoma was found to be statistically significantly increased in
female mice in all dose groups. These data suggest that female mice were the most sensitive
group tested for 1,4-dioxane-induced liver carcinogenicity. Importantly, the BDF1 mouse is not
particularly sensitive to hepatocellular adenomas and carcinomas based on background incidence
rates reported in other studies, indicating that the results from Kano et al. (2009) are reasonable
(USEPA, 2013). Refer to USEPA (2013) for a full review of all the noncancer effects reported in
Kano et al. (2009).
In the absence of a plausible mode of action (MOA) for 1,4-dioxane carcinogenicity, the
CSF was derived using linear extrapolation from the point of departure (POD) (i.e., the 95
percent lower confidence limit on the dose associated with a benchmark response near the lower
end of the observed data) calculated by fitting a curve to the experimental dose-response data
using log-logistic benchmark dose modeling. USEPA (2013) indicated that a multistage model
did not provide an adequate fit because of the steep rise in the dose-response curve from the low-
dose to the mid-dose groups followed by a plateau between the mid- and high-dose groups for
the hepatocellular adenoma or carcinoma incidence data in the female mice. EPA performed a
comparison of benchmark dose (BMD) and benchmark dose limit (BMDL) estimates derived for
studies of rats and mice and found that female mice are more sensitive to 1,4-dioxane-induced
liver carcinogenicity than are other species, and that they are more sensitive to 1,4-dioxane-
induced liver carcinogenicity than to other types of tumors. EPA therefore derived the CSF for
1,4-dioxane using the benchmark dose level (BMDL) human equivalent dose for hepatocellular
1 Note that results from the two-year drinking water study have been reported in multiple publications and/or
communications (Kano et al., 2009; Yamazaki et al., 1994; JBRC, 1998; and Yamazaki, 2006).
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adenomas or carcinomas in female mice with a benchmark response of 50 percent as the POD
(USEPA, 2013).
The HRL for 1,4 dioxane is calculated as follows using the oral CSF described above:
CRL BW
HRL = —— *
CSF DWI
1 x 10-6 80 kg
HRL = — * = 0.32 jxg/L
Q 1 mg/kg 2.5 L/day
day
HRL = 0.3 iig/L
CRL = Cancer risk level, assumed to be 1 in a million (1 x 10"6)
CSF = Cancer Slope Factor ((mg/kg/day)"1)
BW = Body weight, 80 kg (USEPA, 2011)
DWI = Drinking water intake, 2.5 L/day (USEPA, 2011)
For comparison purposes, an HRL for 1,4 dioxane based on the RfD of 0.03 mg/kg/day
derived by EPA IRIS (USEPA, 2010; USEPA, 2013) would be 200 |ig/L. Since the HRL derived
using the oral CSF (0.3 |ig/L) is lower than the HRL of 200 |ig/L derived based on the RfD
(noncancer effects), the HRL based on the oral CSF is protective of noncancer effects.
EPA derived an estimate of baseline cancer cases per year using the CSF as described
above, together with a national extrapolated population-weighted mean concentration based on
data from the third Unregulated Contaminant Monitoring Rule (UCMR 3) (described in Section
B.4.2 below). For purposes of this calculation, EPA assumed that all UCMR 3 non-detect
samples had 1,4-dioxane concentrations of 0.07 |ig/L, the value of the minimum reporting level
(MRL). Use of this conservative assumption was intended to provide a high-end estimate of the
number of national cancer cases. Based on this methodology, EPA estimates that 1,4-dioxane in
drinking water is responsible for fewer than two cancer cases per year. However, while the
number of baseline annual cancer cases is relatively low, other adverse health effects following
exposure to 1,4-dioxane may also contribute to potential risk to public health, and analyses
addressing these have not yet been completed.
B.3.5 Health Effects Data Gaps
There are adequate animal toxicology data available for hazard and risk assessment of
1,4-dioxane (USEPA, 2013). Oral toxicity studies include chronic and subchronic drinking water
studies in rats and mice, and one developmental study in rats. The database also includes two
subchronic inhalation studies in rabbits, guinea pigs, mice, and rats as well as two chronic
inhalation studies in rats. PBPK models and genotoxicity studies for 1,4-dioxane have also been
described.
There is a lack of developmental and reproductive toxicity information for 1,4-dioxane. A
single oral prenatal developmental toxicity study in rats is currently available. The results from
this study indicate that the developing fetus might be a target of toxicity. In addition, there are no
data currently available to determine whether children are more sensitive than adults to the
effects of 1,4-dioxane exposure (USEPA, 2013). Additional developmental and reproductive
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toxicity investigations, including multigenerational reproductive studies, could provide valuable
information.
There are not enough data to determine the mode of carcinogenic action for 1,4 dioxane,
as the key events underlying promotion of tumor formation by 1,4-dioxane are unknown.
Although available data indicate that 1,4-dioxane is metabolized in vivo, it is unknown whether a
metabolite or 1,4-dioxane itself, or some combination of 1,4-dioxane and its metabolites, is
responsible for the observed carcinogenicity. It is unknown how additional MOA information
would affect the dose-response assessment for 1,4-dioxane because of the variety of tumors
observed in animal studies and the lack of data on how 1,4-dioxane or its metabolites interact
with cells to promote tumor formation (USEPA, 2013). The metabolism of 1,4-dioxane in vivo
and the mechanism underlying 1,4-dioxane carcinogenicity could be investigated further. There
is some indication that liver toxicity and subsequent tumor development may only occur when
1,4-dioxane metabolism is saturated, but further research could be useful (ATSDR, 2012).
Health Canada released a guideline technical document for 1,4-dioxane for public
consultation in 2018 (Health Canada, 2018). The consultation period ended on November 9,
2018, and a final publication is pending. The Agency recently completed its new TSCA risk
evaluation for 1,4-dioxane by the Office of Chemical Safety and Pollution Prevention (OCSPP)
(USEPA, 2020a) and intends to consider it and the Canadian guideline technical document, once
finalized, (Health Canada, 2018) and other relevant new science relevant to drinking water
contamination prior to making a regulatory determination.
B.4 Occurrence
This section presents data on the occurrence of 1,4-dioxane in ambient water and
drinking water in the United States. As described in section B.3, an HRL of 0.3 |ig/L was
calculated for 1,4-dioxane based on carcinogenic effects. HRLs are risk-derived concentrations
against which EPA evaluates the occurrence data to determine if contaminants occur at levels of
potential public health concern. Occurrence data from various sources presented below are
analyzed with respect to the HRL and one-half the HRL. When possible, estimates of the
population exposed at concentrations above the HRL and one-half the HRL are presented.
For additional background information about data sources used to evaluate occurrence,
please refer to Chapter 2.
B.4.1 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the ambient sources of most drinking water. Contaminant
occurrence in ambient water provides information on the potential for contaminants to adversely
affect drinking water supplies. Occurrence data for 1,4-dioxane in ambient water are available
from the United States Geological Survey (USGS) National Water-Quality Assessment
(NAWQA) program, the USGS National Water Information System (NWIS) database, and
EPA's legacy Storage and Retrieval Data System (STORET) data available through the Water
Quality Portal (WQP).
United States Geological Survey (USGS) National Water-Quality Assessment (NA WQA)
Ambient Water Analyses
USGS instituted the NAWQA program in 1991 to examine ambient water quality status
and trends in the United States. The NAWQA program generates high quality contaminant
occurrence and other water quality parameter data for significant watersheds and aquifers across
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the nation. The program collects data on surface water and groundwater chemistry, hydrology,
land use, stream habitat, and aquatic life in parts or all of nearly all 50 States. The program is
designed to apply nationally consistent methods to provide a uniform basis for contaminant
occurrence comparisons and assessments among study basins across the country and over time.
The occurrence assessments can also serve to facilitate interpretation of natural and
anthropogenic factors affecting national water quality. For more detailed information on the
NAWQA program design and implementation, refer to Leahy and Thompson (1994) and
Hamilton et al. (2004).
The process of sampling, analysis, and data synthesis is divided into cycles of
approximately ten years: Cycle 1 covered 1991-2001, Cycle 2 covered 2002-2012, and Cycle 3 is
ongoing and covers 2013-2023. Study units are sampled and analyzed on a staggered schedule
within each cycle. Each NAWQA cycle begins with a two-year startup phase for planning and
retroactive analysis, followed by a three-year intensive data collection phase, and finally a five-
year phase for analyzing the data, developing reports, and continuing a low level of monitoring
(NRC, 2012).
During Cycle 1 (1991-2001), 51 study units were sampled. Data were gathered from
6,307 wells from 272 groundwater networks or clusters and from 6,400 sampling points at 505
surface water monitoring sites, primarily rivers and streams but also some lakes and reservoirs
(NRC, 2002). In Cycle 2 (2002-2012), the number of study units was reduced from 51 to 42
(NRC, 2012). Long-term stream monitoring was established at 113 streams representing 8 major
river basins. Long-term groundwater monitoring was established at sites representing 20
principal aquifers with more than 10 to 15 years of consistent monitoring data available (Rowe et
al., 2013).
Sampling for Cycle 3 is currently underway (2013-2023). Surface water monitoring will
be conducted at 313 sites, increased from 113 sites in Cycle 2 (Rowe et al., 2013). Groundwater
assessments in Cycle 3 will be designed to evaluate status and trends at the principal aquifer
(PA) and national scales. Assessments are planned in 24 PAs that account for the majority of
current and future national groundwater use for drinking water. Data available through 2017 are
presented in this report. For more details on the Cycle 3 sampling design, refer to Rowe et al.
(2010; 2013).
EPA's analysis of the NAWQA data is a simple, non-parametric occurrence analysis that
provides summary statistics to characterize contaminant occurrence. EPA calculated detection
frequencies as the percentage of samples and the percentage of sites with at least one detection,
without any censoring or weighting. (A detection is an analytical result equal to or greater than
the reporting level.) EPA reported the minimum and maximum detected concentrations and
calculated other descriptive statistics including the median, 90th percentile, and 99th percentile
concentrations (based only on samples with detections). Reporting levels varied over time during
the NAWQA program. In some cases, therefore, the minimum concentration reported as a
detection could be lower than the highest reporting level.
Exhibit B-8 through Exhibit B-10 present analyses of the 1,4-dioxane NAWQA data,
downloaded from the Water Quality Portal in September 2018 (WQP, 2018). No Cycle 1 or
Cycle 2 data were available for 1,4-dioxane. In Cycle 3 (through 2017), 1,4-dioxane was
detected in approximately 0.70 percent of samples (11 out of 1,579) and at 0.57 percent of sites
(8 out of 1,406). The median concentration based on detections in Cycle 3 was 1.83 |ig/L. As
noted above, NAWQA data are ambient water data, not finished drinking water data.
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Exhibit B-8: 1,4-Dioxane NAWQA Data - Summary of Detected Concentrations
Site Type
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Cycle 1 (1991 -2001)
Groundwater
-
-
-
-
-
Surface Water
-
-
-
-
-
All Sites
-
-
-
-
-
Cycle 2 (2002-2012)
Groundwater
-
-
-
-
-
Surface Water
-
-
-
-
-
All Sites
-
-
-
-
-
Cycle 3 (2013-2017)
Groundwater
0.9
1.83
3.06
3.53
3.58
Surface Water
0.568
2.07
17.6
18.8
18.9
All Sites
0.568
1.83
16.5
18.7
18.9
Source: WQP, 2018
Exhibit B-9: 1,4-Dioxane NAWQA Data - Summary of Samples
Site Type
No. of
Samples
Detection Frequency
(detections are results > reporting level)
No. of
Samples
with
Detections
%
Samples
with
Detections
No. of
Samples
with
Detections
> 1/2 HRL
%
Samples
with
Detections
> 1/2 HRL
No. of
Samples
with
Detections
> HRL
%
Samples
with
Detections
> HRL
Cycle 1 (1991 -2001)
Groundwater
-
-
-
-
-
-
-
Surface Water
-
-
-
-
-
-
-
All Sites
-
-
-
-
-
-
-
Cycle 2 (2002-2012)
Groundwater
-
-
-
-
-
-
-
Surface Water
-
-
-
-
-
-
-
All Sites
-
-
-
-
-
-
-
Cycle 3 (2013-2017)
Groundwater
1,428
3
0.21%
3
0.21%
3
0.21%
Surface Water
151
8
5.30%
8
5.30%
8
5.30%
All Sites
1,579
11
0.70%
11
0.70%
11
0.70%
Source: WQP, 2018
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Exhibit B-10: 1,4-Dioxane NAWQA Data - Summary of Sites
Site Type
No. of
Sites
Detection Frequency
(detections are results > reporting level)
No. of
Sites with
Detections
% Sites
with
Detections
No. of
Sites with
Detections
> 1/2 HRL
% Sites
with
Detections
> 1/2 HRL
No. of
Sites with
Detections
> HRL
% Sites
with
Detections
> HRL
Cycle 1 (1991 -2001)
Groundwater
-
-
-
-
-
-
-
Surface Water
-
-
-
-
-
-
-
All Sites
-
-
-
-
-
-
-
Cycle 2 (2002-2012)
Groundwater
-
-
-
-
-
-
-
Surface Water
-
-
-
-
-
-
-
All Sites
-
-
-
-
-
-
-
Cycle 3 (2013-2017)
Groundwater
1,355
3
0.22%
3
0.22%
3
0.22%
Surface Water
51
5
9.80%
5
9.80%
5
9.80%
All Sites
1,406
8
0.57%
8
0.57%
8
0.57%
Source: WQP, 2018
National Water Information System (NWIS) Data
The National Water Information System (NWIS) is the Nation's principal repository of
water resources data USGS collects from more than 1.5 million sites (USGS, 2016). NWIS-Web
is the general online interface to the USGS NWIS database. Discrete water-sample and time-
series data are available from sites in all 50 states, including 5 million water samples with 90
million water-quality results. All USGS water quality and flow data are stored in NWIS,
including site characteristics, streamflow, groundwater level, precipitation, and chemical
analyses of water, sediment, and biological media, though not all parameters are available for
every site. NWIS houses the NAWQA data and includes other USGS data from unspecified
projects. NWIS contains many more samples at many more sites than the NAWQA Program.
Although NWIS is comprised of primarily ambient water data, some finished drinking water data
are included as well. This section presents analyses of non-NAWQA data in NWIS, downloaded
from the Water Quality Portal in December 2017 (WQP, 2017). These data do not overlap with
the results presented in Exhibit B-8 through Exhibit B-10.
The results of the non-NAWQA NWIS 1,4-dioxane analyses are presented in Exhibit B-
11. 1,4-Dioxane was detected in approximately 27 percent of samples (537 out of 1,978 samples)
and at approximately 12 percent of sites (136 out of 1,182 sites). The median concentration
based on detections was equal to 4.10 |ig/L. (Note that the NWIS data are presented as
downloaded; potential outliers were not evaluated or excluded from the analysis.)
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Exhibit B-11: 1,4-Dioxane NWIS Data, 1991 - 2016
Site Type
Detection Frequency
(detections are results > reporting level)
Concentration Values
(of detections, in |jg/L)
No. of
Samples
No. of
Samples
with
Detections
No.
of
Sites
No. of
Sites with
Detections
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Groundwater
1,834
517
1,084
127
0.083
4.40
11.0
4,190
31,000
Surface
Water
143
19
99
9
0.723
1.65
3.59
6.97
7.66
Finished
Water
1
1
1
1
10.5
10.5
10.5
10.5
10.5
All Sites
1,978
537
1,182
136
0.083
4.10
10.2
4,096
31,000
Source: WQP, 2017
Storage and Retrieval (STORET) Data / Water Quality Portal (WQP)
From its launch in 1999 until it was decommissioned in June 2018, EPA's STORET Data
Warehouse was collaboratively populated with raw biological, chemical, and physical data from
surface water and groundwater sampling by federal, state, and local agencies, Native American
tribes, volunteer groups, academics, and others. Legacy STORET data are accessible through the
Water Quality Portal (WQP): https://www.waterqualitvdata.us/portal/.
STORET data are from monitoring locations in all 50 states as well as multiple territories
and jurisdictions of the United States. Most data are from ambient waters, but in some cases
finished drinking water data are included as well. STORET's data quality limitations include
variations in the extent of national coverage and data completeness from parameter to parameter.
Data may have been collected as part of targeted, rather than randomized, monitoring.
This section presents analyses of STORET data, downloaded from the WQP in December
2017 (WQP, 2017). EPA reviewed STORET groundwater data from wells and surface water data
from lakes, rivers/streams, and reservoirs (WQP, 2017). The results of the STORET analysis for
1,4-dioxane are presented in Exhibit B-12 through Exhibit B-14. These 1,4-dioxane samples
were collected between 2002 and 2016. Of the 569 sites sampled, 417 (73.3 percent) reported
detections of 1,4-dioxane. Detected concentrations ranged from 0.032 |ig/L to 1,400 |ig/L. The
90th percentile concentration of detections was equal to 20 |ig/L. The minimum detected
concentration may be indicative of the reporting levels used. (A minimum value of zero, on the
other hand, could represent a detection that was entered into the database as a non-numerical
value (e.g., "Present").)
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Exhibit B-12: 1,4-Dioxane STORET Data - Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (|jg/L
Minimum1
Median
90th Percentile
Maximum
Groundwater
0.08
2.1
20
1,400
Surface Water
0.032
11.5
16
100
Total
0.032
2.4
20
1,400
Source: WQP, 2017
1A minimum value of zero may represent a detection that was entered into the database as a non-numerical value
(e.g., "Present").
Exhibit B-13: 1,4-Dioxane STORET Data - Summary of Samples and Sites
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Total
Number
of Sites
Sites with Detections
Number
Percent
Number
Percent
Groundwater
2,564
1,640
63.96%
475
369
77.68%
Surface Water
168
106
63.10%
94
48
51.06%
Total
2,732
1,746
63.91%
569
417
73.29%
Source: WQP, 2017
Exhibit B-14: 1,4-Dioxane STORET Data - Summary of States
Source Water
Type
Total
Number of
States
States with Detections
Number
Percent
Groundwater
2
2
100.00%
Surface Water
5
3
60.00%
Total1
7
5
71.43%
Source: WQP, 2017
1 The number of states with groundwater data plus the number of
states with surface water data may not equal the "Total" number of
states providing data because some states provided both
groundwater and surface water data.
B.4.2 Occurrence in Drinking Water
Data sources reviewed by the Agency for information on contaminant occurrence in
drinking water included: EPA's first, second, and third Unregulated Contaminant Monitoring
Rules (UCMR 1, UCMR 2, UCMR 3); Rounds 1 and 2 of the Agency's Unregulated
Contaminant Monitoring (UCM) program that preceded the Unregulated Contaminant
Monitoring Rule (UCMR); EPA's Information Collection Rule; EPA's National Inorganics and
Radionuclides Survey (NIRS); and a range of others as discussed in Chapter 2. Among the
sources reviewed, the following had data and information on 1,4-dioxane occurrence in drinking
water. These data and information are discussed in this section.
• EPA's Third Unregulated Contaminant Monitoring Rule (UCMR 3).
State drinking water monitoring programs.
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EPA's Community Water System Survey (CWSS).
Additional sources: namely, the California State Water Resources Control Board
(California SWRCB)
Note that there may be some overlap, as sources with different purposes and audiences
may have reported the same underlying data. UCMR 3 is a national data source. Other data
sources profiled in this section are considered "supplemental" sources. Also note that the
presentation of NWIS results in the ambient water section, above, includes some finished water
data.
Primary Data Sources
EPA's Third Unregulated Contaminant Monitoring Rule (UCMR 3) 2013-2015
UCMR 3 monitoring, designed to provide nationally representative contaminant
occurrence data, was conducted from 2013 through 2015. UCMR 3 List 1 Assessment
Monitoring occurrence data are available for 1,4-dioxane. For UCMR 3, all large and very large
public water systems (PWSs) (those serving between 10,001 and 100,000 people and serving
more than 100,000 people, respectively), plus a statistically representative national sample of
800 small PWSs (serving 10,000 people or fewer), were required to conduct Assessment
Monitoring during a 12-month period between January 2013 and December 2015.2 Surface water
(and groundwater under the direct influence of surface water (GWUDI)) sampling points were
monitored four times during the applicable year of monitoring, and groundwater sampling points
were monitored twice during the applicable year of monitoring. See USEPA (2012) and USEPA
(2019c) for more information on the UCMR 3 study design and data analysis.
The design of UCMR 3 permits estimation of national occurrence by multiplying the total
number of systems (or population served) in the nation in a system size category by the percent
of systems expected to exceed a specified threshold. An extrapolation methodology is applied to
small systems because not all small systems were required to participate in the UCMR 3
Assessment Monitoring. Because all large and very large systems were required to participate in
the UCMR 3 Assessment Monitoring, national estimates of occurrence in these size categories
can be done using survey census figures rather than extrapolation. Total national occurrence is
estimated by summing the extrapolated figures for small systems and the census figures for the
large and very large systems.
Exhibit B-15 through Exhibit B-19 provide an overview of 1,4-dioxane occurrence
results from UCMR 3 Assessment Monitoring. Laboratories participating in UCMR 3 were
required to report values at or above MRLs defined by EPA. The MRLs are established to ensure
reliable and consistent results from the array of laboratories needed for a national monitoring
program and are set based on the capability of multiple commercial laboratories prior to the
beginning of each UCMR round. The MRL used for 1,4-dioxane in the UCMR 3 survey was
0.07 |ig/L (77 FR 26072; USEPA, 2012). Exhibit B-15 shows a statistical summary of 1,4-
dioxane concentrations by system size and source water type (including the minimum, median,
90th percentile, 99th percentile, and maximum). Exhibit B-16 presents a sample-level summary of
the results. Exhibit B-17 through Exhibit B-19 show system-level results, including national
extrapolations, at three thresholds: detections, one-half the HRL, and the HRL. Detections are
2 Only 799 small systems submitted Assessment Monitoring results.
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evaluated on a "greater than or equal to" basis (> the MRL), while health-based thresholds are
evaluated in terms of exceedances (> one-half HRL, and > HRL).
As noted above, UCMR 3 monitoring was required at a representative sample of small
systems and at all large and very large systems. As a reminder that the figures from large and
very large systems represent a census of systems in those categories, results in those categories
are labelled "CENSUS" in Exhibit B-17 through Exhibit B-19. No extrapolation was necessary
in these categories, as it was for the small systems, to derive national estimates of occurrence in
these exhibits. National estimates of occurrence are reported separately in each system size and
source water category, and also in aggregate.
A total of 36,810 finished water samples for 1,4-dioxane were collected from 4,915
systems. 1,4-Dioxane was measured > MRL in 11.40 percent of UCMR 3 samples. Reported 1,4-
dioxane concentrations for these "positive" results ranged from 0.07 |ig/L (the MRL) to 34 |ig/L.
Of 4,915 systems, 641 (13.0 percent of systems, serving 20.6 percent of the PWS-served
population) reported at least one detection greater than one-half the HRL (0.15 |ig/L) and 382
(7.8 percent of systems, serving 12.7 percent of the PWS-served population) reported at least one
detection greater than the HRL of 0.3 |ig/L. Extrapolating these findings suggests that an
estimated 3,116 PWSs serving 52.5 million people nationally would have at least one 1,4-
dioxane detection greater than one-half the HRL and an estimated 1,602 PWSs serving 31.8
million people nationally would have at least one 1,4-dioxane detection greater than the HRL.
EPA also evaluated the proportion of UCMR 3 systems with average 1,4-dioxane
concentrations greater than the HRL (not shown in tables below). Assigning non-detections a
concentration value of one-half the MRL, EPA calculated that approximately 149 systems had a
system average concentration of 1,4-dioxane greater than the HRL. Of these 149 systems, 38
percent were located in California and New York (38 systems in California and 18 systems in
New York). Note that California has a notification level of 1 |ig/L for 1,4-dioxane and New York
has a recommended MCL of 1.0 |ig/L for 1,4-dioxane (California SWRCB, 2018; NYSDOH,
2018).
Exhibit B-15: 1,4-Dioxane Occurrence Data from UCMR 3 Assessment Monitoring
- Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (in |jg/L) > MRL of 0.07 |jg/L
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Small Systems (serving < 10,000 people)
Groundwater
0.07
0.13
0.50
3.26
3.64
Surface Water
0.07
0.14
0.53
1.83
2.11
All Small Systems
0.07
0.14
0.53
2.77
3.64
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
0.07
0.17
0.95
4.50
34.00
Surface Water
0.07
0.15
1.10
5.16
13.30
All Large Systems
0.07
0.16
1.00
4.83
34.00
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Final Regulatory Determination 4 Support Document - App B, 1,4-Dioxane
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Source Water Type
Concentration Value of Detections (in |jg/L) > MRL of 0.07 |jg/L
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
0.07
0.23
1.12
6.33
22.93
Surface Water
0.07
0.17
0.61
6.40
8.80
All Very Large Systems
0.07
0.19
0.86
6.62
22.93
All Systems
All Water Systems
0.07
0.17
0.93
5.30
34.00
Source: USEPA, 2017b
Exhibit B-16: 1,4-Dioxane National Occurrence Measures Based on UCMR 3
Assessment Monitoring Data - Summary of Samples
Source Water Type
Total # of
Samples
Samples with Detections
> MRL (0.07 |jg/L)
Samples with
Detections
>1/2 HRL (0.15
Samples with
Detections
> HRL (0.3 |jg/L)
Number
Percent
Number
Percent
Number
Percent
Small Systems (serving < 10,000 people)
Groundwater
1,852
71
3.83%
32
1.73%
13
0.70%
Surface Water
1,421
124
8.73%
58
4.08%
27
1.90%
All Small Systems
3,273
195
5.96%
90
2.75%
40
1.22%
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
11,640
1,236
10.62%
677
5.82%
391
3.36%
Surface Water
14,790
1,637
11.07%
814
5.50%
453
3.06%
All Large Systems
26,430
2,873
10.87%
1,491
5.64%
844
3.19%
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
2,011
423
21.03%
272
13.53%
172
8.55%
Surface Water
5,096
706
13.85%
394
7.73%
188
3.69%
All Very Large Systems
7,107
1,129
15.89%
666
9.37%
360
5.07%
All Systems
All Water Systems
36,810
4,197
11.40%
2,247
6.10%
1,244
3.38%
Source: USEPA, 2017b
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Final Regulatory Determination 4 Support Document - App B, 1,4-Dioxane
January 2021
Exhibit B-17: 1,4-Dioxane National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data - Summary
of System and Population Served Data - Detections
Source Water Type
UCMR 3 Sample
Number With At Least One
Detection > MRL (0.07 iig/L)
Percent With At Least One
Detection
National Inventory1
National Estimate2
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people
Groundwater
527
1,498,845
36
101,736
6.83%
6.79%
55,700
38,730,597
3,800
2,630,000
Surface Water
272
1,250,215
49
256,179
18.01%
20.49%
9,728
20,007,917
1,750
4,100,000
All Small Systems
799
2,749,060
85
357,915
10.64%
13.02%
65,428
58,738,514
5,560
6,730,000
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
1,450
37,101,949
343
10,219,737
23.66%
27.55%
1,470
37,540,614
343
10,200,000
Surface Water
2,258
69,538,817
501
16,138,714
22.19%
23.21%
2,310
70,791,005
501
16,100,000
All Large Systems
3,708
106,640,766
844
26,358,451
22.76%
24.72%
3,780
108,331,619
844
26,400,000
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
68
16,355,951
34
9,643,118
50.00%
58.96%
68
16,355,951
34
9,640,000
Surface Water
340
115,158,260
114
48,341,749
33.53%
41.98%
343
120,785,622
114
48,300,000
All Very Large
Systems
408
131,514,211
148
57,984,867
36.27%
44.09%
411
137,141,573
148
58,000,000
All Systems
All Water Systems
4,915
240,904,037
1,077
84,701,233
21.91%
35.16%
69,619
304,211,706
6,550
91,100,000
Source: USEPA, 2017b
1 The small system national inventory numbers for systems and population served by systems were derived from a freeze of the December 2010 Safe Drinking Water
Information System/Federal version (SDWIS/Fed) data. These counts are based on all community and non-transient non-community water systems that served 10,000
people or fewer. All large and very large systems were required to conduct UCMR 3 Assessment Monitoring; thus, the national inventory numbers for the large and very
large systems are based on the number of systems expected to complete UCMR 3 monitoring. SDWIS/Fed inventory data from 2010 were used for the UCMR 3 national
extrapolations as these data were consistent with the UCMR 3 inventory data at the timeframe of the UCMR 3 sample design.
2 National estimates for the small systems are generated by multiplying the UCMR 3 national statistical sample findings of system/population percentages and national
system/population inventory numbers for PWSs. National estimates for the large and very large systems are based directly on the UCMR 3 results, since this was a
census. Due to rounding, some calculations may appear to be slightly off.
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Final Regulatory Determination 4 Support Document - App B, 1,4-Dioxane
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Exhibit B-18: 1,4-Dioxane National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data - Summary
of System and Population Served Data - Detections > 1/2 the HRL (0.15 |jg/L)
Source Water
Type
UCMR 3 Sample
Number With At Least One
Detection > 1/2 HRL
(0.15 |ig/L)
Percent With At Least One
Detection > 1/2 HRL
(0.15 |ig/L)
National Inventory1
National Estimate2
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Groundwater
527
1,498,845
16
49,360
3.04%
3.29%
55,700
38,730,597
1,690
1,280,000
Surface Water
272
1,250,215
23
110,562
8.46%
8.84%
9,728
20,007,917
823
1,770,000
All Small Systems
799
2,749,060
39
159,922
4.88%
5.82%
65,428
58,738,514
2,510
3,040,000
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
1,450
37,101,949
212
6,286,934
14.62%
16.95%
1,470
37,540,614
212
6,290,000
Surface Water
2,258
69,538,817
292
9,492,239
12.93%
13.65%
2,310
70,791,005
292
9,490,000
All Large Systems
3,708
106,640,766
504
15,779,173
13.59%
14.80%
3,780
108,331,619
504
15,800,000
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
68
16,355,951
21
5,058,129
30.88%
30.93%
68
16,355,951
21
5,060,000
Surface Water
340
115,158,260
77
28,595,952
22.65%
24.83%
343
120,785,622
77
28,600,000
All Very Large
Systems
408
131,514,211
98
33,654,081
24.02%
25.59%
411
137,141,573
98
33,700,00
All Systems
All Water Systems
4,915
240,904,037
641
49,593,176
13.04%
20.59%
69,619
304,211,706
3,120
52,500,000
Source: USEPA, 2017b
1 The small system national inventory numbers for systems and population served by systems were derived from a freeze of the December 2010 SDWIS/Fed data. These
counts are based on all community and non-transient non-community water systems that served 10,000 people or fewer. All large and very large systems were required
to conduct UCMR 3 Assessment Monitoring; thus, the national inventory numbers for the large and very large systems are based on the number of systems expected to
complete UCMR 3 monitoring. SDWIS/Fed inventory data from 2010 were used for the UCMR 3 national extrapolations as these data were consistent with the UCMR 3
inventory data at the timeframe of the UCMR 3 sample design.
2 National estimates for the small systems are generated by multiplying the UCMR 3 national statistical sample findings of system/population percentages and national
system/population inventory numbers for PWSs. National estimates for the large and very large systems are based directly on the UCMR 3 results, since this was a
census. Due to rounding, some calculations may appear to be slightly off.
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Final Regulatory Determination 4 Support Document - App B, 1,4-Dioxane
January 2021
Exhibit B-19: 1,4-Dioxane National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data - Summary
of System and Population Served Data - Detections > HRL (0.3 |jg/L)
Source Water Type
UCMR 3 Sample
Number With At Least One
Detection > HRL
(0.3 |ig/L)
Percent With At Least One
Detection > HRL
(0.3 |ig/L)
National Inventory1
National Estimate2
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Groundwater
527
1,498,845
8
19,175
1.52%
1.28%
55,700
38,730,597
846
495,000
Surface Water
272
1,250,215
11
55,049
4.04%
4.40%
9,728
20,007,917
393
881,000
All Small Systems
799
2,749,060
19
74,224
2.38%
2.70%
65,428
58,738,514
1,240
1,380,000
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
1,450
37,101,949
122
3,582,963
8.41%
9.66%
1,470
37,540,614
122
3,580,000
Surface Water
2,258
69,538,817
178
5,909,196
7.88%
8.50%
2,310
70,791,005
178
5,910,000
All Large Systems
3,708
106,640,766
300
9,492,159
8.09%
8.90%
3,780
108,331,619
300
9,490,000
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
68
16,355,951
16
3,925,941
23.53%
24.00%
68
16,355,951
16
3,930,000
Surface Water
340
115,158,260
47
17,051,036
13.82%
14.81%
343
120,785,622
47
17,100,000
All Very Large
Systems
408
131,514,211
63
20,976,977
15.44%
15.95%
411
137,141,573
63
21,000,000
All Systems
All Water Systems
4,915
240,904,037
382
30,543,360
7.77%
12.68%
69,619
304,211,706
1,600
31,800,000
Source: USEPA, 2017b
1 The small system national inventory numbers for systems and population served by systems were derived from a freeze of the December 2010 SDWIS/Fed data. These
counts are based on all community and non-transient non-community water systems that served 10,000 people or fewer. All large and very large systems were required
to conduct UCMR 3 Assessment Monitoring; thus, the national inventory numbers for the large and very large systems are based on the number of systems expected to
complete UCMR 3 monitoring. SDWIS/Fed inventory data from 2010 were used for the UCMR 3 national extrapolations as these data were consistent with the UCMR 3
inventory data at the timeframe of the UCMR 3 sample design.
2 National estimates for the small systems are generated by multiplying the UCMR 3 national statistical sample findings of system/population percentages and national
system/population inventory numbers for PWSs. National estimates for the large and very large systems are based directly on the UCMR 3 results, since this was a
census. Due to rounding, some calculations may appear to be slightly off.
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Adamson et al. (2017) conducted an independent analysis of UCMR 3 data for 1,4-
dioxane and other contaminants. Some care should be taken when comparing UCMR 3
occurrence findings from that study with results presented elsewhere in this document. Note, for
example, that these authors relied on data from a May 2016 data pull, before all UCMR 3 results
were reported and posted, resulting in a total count of 35,856 1,4-dioxane samples, compared to
the 36,810 samples in the final data set.
Adamson et al. (2017) calculated odds ratios to examine co-occurrence between 1,4-
dioxane and other UCMR 3 contaminants. The strongest relationship found was with 1,1-
dichloroethane. Based on calculated odds ratios, samples with a 1,4-dioxane detection were 46.0
times more likely to occur with a 1,1-dichloroethane detection than without a 1,1-dichloroethane
detection when adjusted for system size. Statistically significant (at a 95 percent confidence
level) co-occurrence was also observed with perfluorooctanesulfonic acid (PFOS) and
perfluorooctanoic acid (PFOA). Samples with a 1,4-dioxane detection were 14.2 times more
likely to occur with a PFOS detection than without a PFOS detection when adjusted for system
size, and 13.4 times more likely to occur with a PFOA detection than without a PFOA detection
when adjusted for system size. Similar co-occurrence relationships were observed when 1,4-
dioxane was evaluated at a health-based threshold of 3.5 |ig/L (which is close to EPA's HRL).
Adamson et al. (2017) also examined temporal trends. When results for all samples were
aggregated by quarter (cumulative detection rate per quarter, for 12 quarters over the three-year
monitoring period of 2013-2015), a declining trend was observed but the p-value of 0.086 for the
regression line was slightly higher than the p < 0.05 threshold for statistical significance used in
this study. An alternative approach, linear regression of all detected 1,4-dioxane concentrations
plotted over time, established a statistically significant (p < 0.0001) decline over the three-year
period. The authors note that attempts to establish temporal trends on a facility basis (i.e., in
relation to the initial concentration observed at a facility) were inconclusive.
Supplemental Data Sources
State Monitoring Data, 1996-2011
Because there is no available national database that receives and stores all relevant data
regarding the occurrence of regulated contaminants in public drinking water systems, EPA
conducts voluntary data requests from the states, territories, and tribes in support of national
occurrence assessments. These assessments are part of the Six-Year Review. Under the second
and third Six-Year Review (SYR2 and SYR3), a few states submitted PWS occurrence data for
unregulated contaminants along with the requested data on regulated contaminants. EPA was
able to supplement the data on unregulated contaminants by downloading additional publicly
available monitoring data from state websites. For SYR2, the result was a collection of
unregulated contaminant monitoring data from nine states and other entities, such as tribes,
territories, and EPA Regions. For SYR3, the dataset of unregulated contaminant monitoring data
included results from 14 states/entities. For both rounds of the Six-Year Review, these
unregulated data provide varying degrees of completeness in their coverage of the states/entities
and are not necessarily representative of occurrence in those states/entities. For more details on
the Six-Year Review Information Collection Request (ICR) Dataset for SYR2, refer to USEPA
(2009a). For more details on the SYR3 ICR Dataset, refer to EPA's SYR3 occurrence analysis
(USEPA, 2016).
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Final Regulatory Determination 4 Support Document - App B, 1,4-Dioxane
January 2021
Drinking water occurrence data for 1,4-dioxane were available from California under
SYR2 (1999-2005) and California, Michigan, and Pennsylvania under SYR3 (2006-2011).3
Results are presented in Exhibit B-20 through Exhibit B-22. The exhibits do not include
estimates of population served because the 1,4-dioxane data submitted under SYR2 and SYR3
represent only a small portion of all PWSs in each state. See USEPA (2009a) and USEPA (2016)
for the total number of systems that submitted SYR2 and SYR3 data, respectively, from each
state. Comprehensive information about methods used and reporting levels is not available for
this data set. Minimum detected concentrations are reported in Exhibit B-20; these minimum
values may be indicative of reporting levels used.
As noted above, the monitoring data from each state/entity are limited and not necessarily
representative of occurrence in the state/entity. The number of PWSs per state with 1,4-dioxane
data ranges from only two PWSs in Pennsylvania SYR3 data to 220 PWSs in the California
SYR3 data. Overall, detected concentrations ranged from 0.001 |ig/L to 7,830 |ig/L. 1,4-Dioxane
was detected at least once in all of the states with data. The percentage of systems with
detections in each state ranged from 11.71 percent (California SYR2) to 50.00 percent
(Pennsylvania SYR3). The percentage of systems with detections greater than the HRL ranged
from 9.09 percent (Michigan SYR3) to 50.00 percent (Pennsylvania SYR3).
Exhibit B-20: 1,4-Dioxane State Drinking Water Occurrence Data - Summary of
Detected Concentrations
State
Source Water
Type
(Sample Type)
Concentration Value of Detections (|jg/L)
(Date Range)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Second Six-Year Review (SYR2)
Groundwater
(Raw)
0.061
2.1
4.6
5.7
6
Groundwater
(Finished)
0.69
1.3
1.9
2.1
2.1
California
(1996-2005)
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Raw)
0.001
3.7
9.1
22.0
26
Surface Water
(Finished)
0.205
7.5
10.1
40.8
46.2
Surface Water
(Not Provided)1
3.5
3.7
3.8
3.8
3.8
Total
0.001
2.8
8.09
22
46.2
3 Some states provided more than six years' worth of data to EPA in response to the SYR2 and SYR3 ICRs.
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Final Regulatory Determination 4 Support Document - App B, 1,4-Dioxane
January 2021
State
(Date Range)
Source Water
Type
(Sample Type)
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Third Six-Year Review (SYR3)
California
(2006-2011)
Groundwater
(Raw)
0.5
2.5
8.3
19.9
28
Groundwater
(Finished)
0.5
1.3
5.5
7.4
9.1
Groundwater
(Not Provided)1
ND
ND
ND
ND
ND
Surface Water
(Raw)
0.71
2.8
5.8
6.9
7
Surface Water
(Finished)
ND
ND
ND
ND
ND
Surface Water
(Not Provided)1
ND
ND
ND
ND
ND
Total
0.5
2
7
19.02
28
Michigan
(2006-2011)
Groundwater
(Not Provided)1
1
2.85
8.62
3,846
7,830
Surface Water
(Not Provided)1
N/A
N/A
N/A
N/A
N/A
Not Provided2
1
3
9
9
9
Total
1
3
8.96
2,987
7,830
Pennsylvania
(2006-2011)
Groundwater
(Not Provided)1
37.1
65.3
88.2
200.1
611
Surface Water
(Not Provided)1
N/A
N/A
N/A
N/A
N/A
Total
37.1
65.3
88.2
200
611
Source: Data provided to EPA by states and downloaded by EPA from state websites
ND = no detections in this category
N/A = not applicable (no data in this category)
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
Exhibit B-21: 1,4-Dioxane State Drinking Water Occurrence Data - Summary of
Samples
State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Samples
Samples with
Detections
Samples with
Detections
> 1/2 HRL (0.15
M9/L)
Samples with
Detections > HRL
(0.3 jig/L)
Number
Percent
Number
Percent
Number
Percent
Second Six-Year Review (SYR2)
California
(1996-2005)
Groundwater
(Raw)
1,503
129
8.58%
128
8.52%
126
8.38%
Groundwater
(Finished)
277
6
2.17%
6
2.17%
6
2.17%
Groundwater
(Not Provided)1
1
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
837
137
16.37%
89
10.63%
82
9.80%
Surface Water
(Finished)
399
16
4.01%
16
4.01%
15
3.76%
Surface Water
(Not Provided)1
20
4
20.00%
4
20.00%
4
20.00%
Total
3,037
292
9.61%
243
8.00%
233
7.67%
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Final Regulatory Determination 4 Support Document - App B, 1,4-Dioxane
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State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Samples
Samples with
Detections
Samples with
Detections
> 1/2 HRL (0.15
M9/L)
Samples with
Detections > HRL
(0.3 jig/L)
Number
Percent
Number
Percent
Number
Percent
Third Six-Year Review (SYR3)
California
(2006-2011)
Groundwater
(Raw)
4,198
942
22.44%
942
22.44%
942
22.44%
Groundwater
(Finished)
2,538
334
13.16%
334
13.16%
334
13.16%
Groundwater
(Not Provided)1
5
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
1,146
120
10.47%
120
10.47%
120
10.47%
Surface Water
(Finished)
188
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
3
0
0.00%
0
0.00%
0
0.00%
Total
8,078
1,396
17.28%
1,396
17.28%
1,396
17.28%
Michigan
(2006-2011)
Groundwater
(Not Provided)1
97
52
53.61%
1
1.03%
1
1.03%
Surface Water
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Not Provided2
26
11
42.31%
0
0.00%
0
0.00%
Total
123
63
51.22%
1
0.81%
1
0.81%
Pennsylvani
a
(2006-2011)
Groundwater
(Not Provided)1
313
312
99.68%
312
99.68%
312
99.68%
Surface Water
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Total
313
312
99.68%
312
99.68%
312
99.68%
Source: Data provided to EPA by states and downloaded by EPA from state websites
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
Exhibit B-22: 1,4-Dioxane State Drinking Water Occurrence Data - Summary of
Systems
State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Systems with
Detections
Systems with
Detections
> 1/2 HRL
(0.15 ufl/L)
Systems with
Detections > HRL
(0.3 |ig/L)
Systems
Number
Percent
Number
Percent
Number
Percent
Second Six-Year Review (SYR2)
Groundwater
(Raw)
152
17
11.18%
17
11.18%
16
10.53%
Groundwater
(Finished)
21
4
19.05%
4
19.05%
4
19.05%
California
(1996-2005)
Groundwater
(Not Provided)1
1
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
44
7
15.91%
7
15.91%
7
15.91%
Surface Water
(Finished)
25
4
16.00%
4
16.00%
3
12.00%
Surface Water
(Not Provided)1
3
1
33.33%
1
33.33%
1
33.33%
Total
205
24
11.71%
24
11.71%
23
11.22%
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State
(Date Range)
Source Water
Type
(Sample Type)
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections
> 1/2 HRL
(0.15 ug/L)
Systems with
Detections > HRL
(0.3 |ig/L)
Number
Percent
Number
Percent
Number
Percent
Third Six-Year Review (SYR3)
California
(2006-2011)
Groundwater
(Raw)
187
46
24.60%
46
24.60%
46
24.60%
Groundwater
(Finished)
17
9
52.94%
9
52.94%
9
52.94%
Groundwater
(Not Provided)1
3
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Raw)
28
6
21.43%
6
21.43%
6
21.43%
Surface Water
(Finished)
7
0
0.00%
0
0.00%
0
0.00%
Surface Water
(Not Provided)1
3
0
0.00%
0
0.00%
0
0.00%
Total
220
53
24.09%
53
24.09%
53
24.09%
Michigan
(2006-2011)
Groundwater
(Not Provided)1
11
4
36.36%
1
9.09%
1
9.09%
Surface Water
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Not Provided2
3
3
100%
0
0.00%
0
0.00%
Total
11
4
36.36%
1
9.09%
1
9.09%
Pennsylvania
(2006-2011)
Groundwater
(Not Provided)1
2
1
50.00%
1
50.00%
1
50.00%
Surface Water
(Not Provided)1
0
0
0.00%
0
0.00%
0
0.00%
Total
2
1
50.00%
1
50.00%
1
50.00%
Source: Data provided to EPA by states and downloaded by EPA from state websites.
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from raw or finished groundwater or
surface water.
Community Water System Survey (CWSS), 2006
The 2006 CWSS (USEPA, 2009b; USEPA, 2009c) gathered data on the financial and
operating characteristics of a random sample of community water systems nationwide. All
systems serving more than 500,000 people (94 systems in 2006) received the survey. These 94
large systems were asked questions about concentrations of unregulated contaminants in their
raw and finished water. Of these 94 systems, 58 systems (62 percent) responded to the survey,
though not all of these systems answered every question. EPA supplemented the data set by
gathering additional information about contaminant occurrence at the 94 systems from publicly
available sources (e.g., consumer confidence reports (CCRs)).
In the 2006 CWSS, one of the 94 systems serving more than 500,000 people reported
monitoring data for 1,4-dioxane. This system reported results from a total of 25 samples. 1,4-
Dioxane was detected in 17 (68 percent) of the 25 samples. The 90th percentile of detected
concentrations was equal to 1.4 |ig/L which is greater than the 1,4-dioxane HRL of 0.3 ng/L.
Reporting levels were not specified in this survey; however, the minimum detected concentration
may be indicative of reporting levels used.
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Additional Source Water and Drinking Water Studies
The State of California has a drinking water notification level of 1 |ig/L for 1,4-dioxane
(California SWRCB, 2018). An initial notification level of 3 |ig/L was set in 1998, following a
number of 1,4-dioxane detections that had been found in wells throughout the state, mostly in
southern California. In November of 2010, the notification level was revised to 1 |ig/L.
The California State Water Resources Control Board includes a summary of 1,4-dioxane
occurrence on their webpage. Exhibit B-23, below, presents the number of drinking water
sources and systems reporting a peak detection of 1,4-dioxane at or greater than 1 |ig/L from
2012 through 2015. "Sources" are all active and standby wells with two or more reported
detections (California SWRCB, 2018).
Exhibit B-23: California State Water Resources Control Board: 1,4-Dioxane
Occurrence (2012 - 2015)
County
Number of
Sources
Number
of Systems
Peak
Concentration
(ng/L)
Los Angeles
111
36
29.3
Monterey
1
1
3
Orange
23
13
9.7
TOTAL
135
50
29.3
Source: California SWRCB, 2018
B.4.3 Other Data
The Centers for Disease Control and Prevention (CDC) Fourth National Report on Human
Exposure to Environmental Chemicals, 2019 Updated Tables
Since 1999, the National Health and Nutrition Examination Survey (NHANES) has
examined the U.S. population annually and released the data in 2-year cycles. The survey is
based on a representative sample of the U.S. population based on age, gender, and race/ethnicity
(CDC, 2019). The Fourth National Report on Human Exposure to Environmental Chemicals was
published in 2009 (CDC, 2009). The exposure data tables have been updated several times since
the original publication, most recently in 2019 (CDC, 2019). The 2019 updated tables include
data on whole blood concentrations (ng/mL) for 1,4-dioxane. The most recent data are from the
2015-2016 reporting period. With a sample size of 2,950, the 95th percentile whole blood
concentration was below the limit of detection (LOD). The LOD was 0.5 ng/mL. Please note that
this value cannot be directly compared to the HRL because it represents a whole blood
concentration, not a drinking water concentration.
B.5 Analytical Methods
EPA has published two analytical methods that are available for the analysis of 1,4-
dioxane in drinking water:
• EPA Method 522, Version 1.0, Determination of 1,4-Dioxane in Drinking Water by
Solid Phase Extraction (SPE) and Gas Chromatography/Mass Spectrometry (GC/MS)
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with Selective Ion Monitoring (SIM). The Lowest Concentration Minimum Reporting
Levels (LCMRLs) generated by the laboratory that developed the method range from
0.036 to 0.047 |ig/L. Mean recoveries in reagent water, surface water, and
groundwater range from 93.9 to 110%, with Relative Standard Deviations (RSDs) of
2.1 to 20% (USEPA, 2008b).
• EPA Method 541, Determination of 1-Butanol, 1,4-Dioxane, 2-Methoxyethanol and
2-Propen-l-ol in Drinking Water by Solid Phase Extraction and Gas
Chromatography/Mass Spectrometry. The LCMRLs generated by the laboratory that
developed the method range from 0.074 to 0.090 |ig/L. Recoveries in reagent water,
surface water, and groundwater range from 93.0 to 104%, with Relative Standard
Deviations (RSDs) of 2.0 to 5.0% (USEPA, 2015).
Laboratories participating in UCMR 3 were required to use EPA Method 522 and, as
noted in Section B.4.2, were required to report 1,4-dioxane values at or above the EPA-defined
MRL of 0.07 |ig/L (77 FR 26072; USEPA, 2012). The MRL was set based on the capability of
multiple laboratories at the time.
B.6 Treatment Technologies
EPA evaluates whether suitable treatment technologies are available prior to
promulgating a final National Primary Drinking Water Regulation (NPDWR).
EPA's Drinking Water Treatability Database (USEPA, 2020b) summarizes available
technical literature on the efficacy of treatment technologies for a range of priority drinking
water contaminants. According to the Database, advanced oxidation processes such as ozone
combined with hydrogen peroxide, ultraviolet light combined with titanium dioxide, ultraviolet
light combined with peroxide, and hydrogen peroxide combined with ferrous iron (Fenton's
reaction) are considered to be the most effective treatment processes for 1,4-dioxane removal,
routinely achieving greater than 99 percent reduction. Membrane separation using reverse
osmosis (up to 96 percent removal) was also shown to be effective at removing 1,4-dioxane at
the bench-scale level. Under specific conditions, adsorptive media (18 to 49 percent removal
with a swellable organically modified silica) and granular activated carbon (only 18 percent
removal in column studies) were able to remove some 1,4-dioxane. These processes may not be
feasible for full-scale water treatment applications. Other atypical water treatment technologies
(biological treatment and biofiltration, both with added microbes, corona discharge, gamma
irradiation, and sonication) also showed promise at removing 1,4-dioxane.
Based on limited studies, the following processes were determined to be ineffective at
removing 1,4-dioxane: aeration, chlorine disinfection, permanganate addition, conventional
treatment, hydrogen peroxide addition, ozonation, powdered activated carbon, and ultraviolet
(UV) irradiation alone (USEPA, 2020b). The exact percentage removal a water system may
achieve with a given technology will be dependent upon a variety of factors, including source
water quality and water system characteristics.
B.7 References
Adamson, D.T., Pina, E.A., Cartwright, A.E., Rauch, S.R., Anderson, R.H., Mohr, T. and
Connor, J. A. 2017. 1,4-Dioxane drinking water occurrence data from the third
unregulated contaminant monitoring rule. Science of the Total Environment, vol. 596, pp.
236-245.
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Final Regulatory Determination 4 Support Document - App B, 1,4-Dioxane
January 2021
Agency for Toxic Substances and Disease Registry (ATSDR). 2012. Toxicological Profile for
1,4-Dioxane. Available on the Internet at:
www.atsdr.cdc.gov/toxprofiles/TP.asp?id=955&tid=199.
California State Water Resources Control Board (California SWRCB). 2018. 1,4-Dioxane.
Available on the Internet at:
http://www.waterboards.ca.gov/drinking water/certlic/drinkingwater/14-Dioxane.shtml.
Accessed December 2018.
Centers for Disease Control and Prevention (CDC). 2009. Fourth National Report on Human
Exposure to Environmental Chemicals, Department of Health and Human Services,
Centers for Disease Control and Prevention. Available on the Internet at:
http://www.cdc.gov/exposurereport/.
CDC. 2019. Fourth National Report on Human Exposure to Environmental Chemicals, Updated
Tables, January 2019: Volume One. Department of Health and Human Services, Centers
for Disease Control and Prevention. Available on the Internet at:
http://www.cdc.gov/exposurereport/.
ChemlDPlus. 2018. Available on the Internet at: http://chem.sis.nlm.nih.gov/chemidplus/.
Accessed December 5, 2018.
Fairley, A., E.C. Linton, and A.H. Ford-Moore. 1934. The toxicity to animals of 1,4-dioxane. J.
Hyg. 34:486-501. (as cited inUSEPA 1987).
Hamilton, P. A., T.L. Miller, and D.N. Myers. 2004. Water Quality in the Nation's Streams and
Aquifers: Overview of Selected Findings, 1991-2001. USGS Circular 1265. Available on
the Internet at: http://water.usgs.gov/pubs/circ/2004/1265/pdf/circularl265.pdf.
Hazardous Substances Data Bank (HSDB). 2015. Profile for 1,4-Dioxane. Available on the
Internet at: http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen7HSDB. Last revision date:
December 23, 2015.
Health Canada. 2018. 1,4-Dioxane in Drinking Water - Guideline Technical Document for
Public Consultation. Available at: https://www.canada.ca/content/dam/hc-
sc/documents/programs/consultation-l-4-dioxane-drinking-water/pub-eng.pdf.
International Agency for Research on Cancer (IARC). 1982. IARC Monographs on the
Evaluation of the Carcinogenic Risk of Chemicals to Humans. Supplement 4.
IARC. 1999. IARC monographs on the evaluation of carcinogenic risks to humans: Re-
evaluation of some organic chemicals, hydrazine and hydrogen peroxide [IARC
Monograph], Supplement 7.
Japan Bioassay Research Center (JBRC). 1998. Two-year studies of 1,4-dioxane in F344 rats and
BDF1 mice (drinking water). Kanagawa, Japan, (as cited in USEPA, 2013).
Kano, H; Y. Umeda, T. Kasai, T. Sasaki, M. Matsumoto, K. Yamazaki, K. Nagano, H. Arito, S.
Fukushima. 2009. Carcinogenicity studies of 1,4-dioxane administered in drinking-water
to rats and mice for 2 years. Food Chem Toxicol 47: 2776-2784. (as cited in USEPA,
2013).
Kociba, R.J., S.B. McCollister, C. Park, T.R. Torkelson, P.J. Ghering. 1974. 1,4-Dioxane. I.
Results of a 2-year ingestion study in rats. Toxicology and Applied Pharmacology,
30:275-286. (as cited in ATSDR 2012, USEPA, 2013, WHO, 2005).
B-37
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Leahy, P.P. and T.H. Thompson. 1994. Overview of the National Water-Quality Assessment
Program. U.S. Geological Survey Open-File Report 94-70. 4 pp. Available on the
Internet at: http://water.usgs.gov/nawqa/NAWQA.OFR94-70.html.
National Research Council (NRC). 2002. Opportunities to Improve the U.S. Geological Survey
National Water Quality Assessment Program. Washington, D.C.: National Academy
Press. Available on the Internet at: https://www.nap.edu/read/10267/chapter/l.
NRC. 2012. Preparing for the Third Decade of the National Water-Quality Assessment
Program. Washington, D.C.: National Academies Press.
National Cancer Institute (NCI). 1978. Bioassay of 1,4-dioxane for possible carcinogenicity. (78-
1330 NCICGTR-80). Bethesda, MD.
http://ntp.niehs.nih.gov/ntp/htdocs/LT rpts/tr080.pdf (as cited in USEPA, 2013).
New York State Department of Health (NYSDOH). 2018. Drinking Water Quality Council
Recommends Nation's Most Protective Maximum Contaminant Levels for Three
Unregulated Contaminants in Drinking Water. Available on the Internet at:
https://www.health.ny.gov/press/releases/2018/2018-12-
18 drinking water quality council recommendations.htm. Last updated December
2018.
Rowe, G.L., K. Belitz, H.I. Essaid, R.J. Gilliom, P A. Hamilton, A.B. Hoos, D.D. Lynch, M.D.
Munn, and D.W. Wolock. 2010. Design of Cycle 3 of the National Water-Quality
Assessment Program, 2013-2023: Part 1: Framework of Water-Quality Issues and
Potential Approaches. U.S. Geological Survey Open-File Report 2009-1296.
https://pubs.usgs.gov/of/2009/1296/.
Rowe, G.L., K. Belitz, C.R. Demas, H.I. Essaid, R.J. Gilliom, P A. Hamilton, A.B. Hoos, C.J.
Lee, M.D. Munn, and D.W. Wolock. 2013. Design of Cycle 3 of the National Water-
Quality Assessment Program, 2013-23: Part 2: Science Plan for Improved Water-Quality
Information and Management. U.S. Geological Survey. Open-File Report 2013-1160.
https://pubs.er.usgs.gov/publication/ofr20131160.
United States Environmental Protection Agency (USEPA). 1986. Guidelines for carcinogenic
risk assessment. Fed. Reg. 51 (185):33992-34003.
USEPA. 1987. p-Dioxane Health Advisory. Available at:
https://nepis.epa.gov/Exe/ZvPDF.cgi/2000SOXI.PDF?Dockev=2000SQXI.PDF.
USEPA. 2005. Guidelines for carcinogen risk assessment. EPA/630/P-03/001F. Washington,
DC: Risk Assessment Forum, https://www3.epa.gov/airtoxics/cancer guidelines final 3-
25-05.pdf
USEPA. 2006. Treatment Technologies for 1,4-Dioxane: Fundamentals and Field Applications.
EPA 542-R-06-009. Available on the Internet at:
https://www.epa.gov/remedvtech/treatment-technologies-14-dioxane-fundamentals-and-
field-applications.
USEPA. 2008a. Using the 2006 Inventory Update Reporting (IUR) Public Data: Background
Document. Office of Pollution Prevention and Toxics. December. Available on the
Internet at:
https://www.epa.gov/sites/production/files/documents/iurdbbackground O.pdf.
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USEPA. 2008b. EPA Method 522. Determination of 1,4-Dioxane in Drinking Water by Solid
Phase Extraction (SPE) and Gas Chromatography/Mass Spectrometry (GC/MS) with
Selective Ion Monitoring (SIM). Version 1.0. National Exposure Research Laboratory,
Office of Research and Development. EPA 600-R-08-101.
USEPA. 2009a. The Analysis of Regulated Contaminant Occurrence Data from Public Water
Systems in Support of the Second Six-Year Review of National Primary Drinking Water
Regulations. EPA-815-B-09-006. October 2009.
USEPA. 2009b. Community Water System Survey 2006 Volume I: Overview. EPA 815-R-09-
001. Available on the Internet at:
https://nepis. epa.gov/Exe/ZyPDF. cgi?Dockev=P 1009JJI.txt.
USEPA. 2009c. Community Water System Survey 2006 Volume II: Detailed Tables and
Methodology. EPA 815-R-09-002. Available on the Internet at:
https://nepis. epa.gov/Exe/ZyPDF. cgi?Dockev=P 1009USA.txt.
USEPA. 2010. Toxicological review of 1,4-Dioxane (CAS No. 123-91-1) in support of summary
information on the Integrated Risk Information System (IRIS) [EPA Report], (EPA-
635/R-09-005-F). Washington, DC.
USEPA. 2011. Exposure Factors Handbook 2011 Edition (Final). EPA/600/R09/052F.
Available at: https://cfpub.epa.gov/ncea/risk/recordisplav.cfm?deid=236252.
USEPA. 2012. Revisions to the Unregulated Contaminant Monitoring Regulation (UCMR 3) for
Public Water Systems. Federal Register 77(85): 26072, May 2, 2012.
USEPA. 2013. Toxicological review of 1,4-Dioxane (with inhalation update) (CAS No. 123-91-
1) in support of summary information on the Integrated Risk Information System (IRIS)
[EPA Report], (EPA-635/R-11/003-F). Washington, DC.
USEPA. 2014. Chemical Data Reporting. Fact Sheet: Basic Information. June. EPA Publication
740-K-13-001.
USEPA. 2015. EPA Method541. Determination of 1-Butanol, 1,4-Dioxane, 2-Methoxyethanol
and 2-Propen-l-ol in Drinking Water by Solid Phase Extraction and Gas
Chromatography/Mass Spectrometry. Office of Ground Water and Drinking Water. EPA
815-R-15-011.
USEPA. 2016. The Analysis of Regulated Contaminant Occurrence Data from Public Water
Systems in Support of the Third Six-Year Review of National Primary Drinking Water
Regulations: Chemical Phase Rules and Radionuclides Rules. EPA 810-R-16-014.
December 2016.
USEPA. 2017a. TRI Explorer: Trends. Available on the Internet at:
https://enviro.epa.gov/triexplorer/tri release.trends. Accessed November 2017.
USEPA. 2017b. Third Unregulated Contaminant Monitoring Rule Dataset. Available on the
Internet at: https://www.epa.gov/dwucmr/occurrence-data-unregulated-contaminant-
monitoring-rule#3. Accessed January 2017.
USEPA. 2018a. CDR Reporting Requirements. Available on the Internet at:
https://www.epa.gov/chemical-data-reporting/how-report-under-chemical-data-reporting.
Accessed December 2018.
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USEPA. 2018b. 2018 Edition of the Drinking Water Standards and Health Advisories Tables.
Available at: https://www.epa.gov/sites/production/files/2018-
03/documents/dwtable2018.pdf.
USEPA. 2019a. CompTox Chemicals Dashboard, Searched by DSSTox Substance Id =
DTXSID4020533. Available on the Internet at:
https://comptox.epa. gov/dashboard/dsstoxdb/results?search=DTXSID4020533.
USEPA. 2019b. The Toxics Release Inventory (TRI) and Factors to Consider When Using TRI
Data. Available on the Internet at: https://www.epa.gov/toxics-release-inventory-tri-
program/factors-consider-when-using-toxics-release-inventory-data
USEPA. 2019c. Occurrence Data from the Third Unregulated Contaminant Monitoring Rule
(UCMR 3). EPA 815-R-19-007.
USEPA. 2020a. Final Risk Evaluations for 1,4-Dioxane. EPA Document # EPA-740-R1-8007.
December 2020. https://www.epa.gov/assessing-and-managing-chemicals-under-
tsca/final -ri sk-evaluati on-14-di oxane#ri skevaluati on.
USEPA. 2020b. Drinking Water Treatability Database.
https://iaspub.epa.gov/tdb/pages/general/home.do. Last updated March 2020.
United States Geological Survey (USGS). 2016. National Water Information System (NWIS)
Water-Quality Web Services. Available on the Internet at:
https://waterdata.usgs.gov/nwis. Last modified December 2016.
Water Quality Portal (WQP). 2017. Water Quality Portal Data Warehouse. Available on the
Internet at: https://www.waterqualitvdata.us/. Data Warehouse consulted December 2017.
World Health Organization (WHO). 2005. 1,4-Dioxane in drinking-water. Background
document for development of WHO Guidelines for drinking-water quality. Geneva,
World Health Organization (WHO/SDE/WSH/05.08/120).
Woo, Y.T., J.C. Arcos, M.F. Argus, G.W. Griffin, and K. Nishiyama. 1977a. Structural
identification of p-dioxane-2-one as the major urinary metabolite of p-dioxane. Naunyn
Schmiedebergs Arch Pharmacol 299: 283-287. http://dx.doi.org/10.1007/BF0050Q322 (as
cited in USEPA, 2013).
Woo, Y.T.; M.F. Argus; J.C. Arcos. 1977b. Tissue and subcellular distribution of 3H-dioxane in
the rat and apparent lack of microsome-catalyzed covalent binding in the target tissue.
Life Sci 21: 1447-1456. http://dx.doi.org/10.1016/0024-3205(77)90199-0 (as cited in
USEPA, 2013).
WQP. 2018. Water Quality Portal Data Warehouse. Available on the Internet at:
https://www.waterqualitvdata.us/. Data Warehouse consulted September 2018.
Yamazaki, K. 2006. Correspondence between Kazunori Yamazaki and Julie Stickney. (as cited
in USEPA, 2013).
Yamazaki, K, H. Ohno, M. Asakura, et al. 1994. Two-year toxicological and carcinogenesis
studies of 1,4-dioxane in F344 rats and BDF1 mice. In: K. Sumino; S. Sato; N.G.
Shinkokai (Eds.), Proceedings: Second Asia-Pacific Symposium on Environmental and
Occupational Health 22-24 July, 1993: Kobe (pp. 193-198). Kobe, Japan: Kobe
University School of Medicine, International Center for Medical Research.
B-40
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Final Regulatory Determination 4 Support Document - App B, 1,4-Dioxane
January 2021
Young, J.D., W.H. Braun, and P.J. Gehring. 1978a. The dose-dependent fate of 1,4-dioxane in
rats. J Environ Pathol Toxicol 2: 263-282. https://pubmed.ncbi.nlm.nih.gov/739213/ (as
cited in USEPA, 2013).
Young, J.D., W.H. Braun, and P.J. Gehring. 1978b. Dose-dependent fate of 1,4-dioxane in rats. J
Toxicol Environ Health A 4:709-726. http://dx.doi.org/10.1080/152873978Q9529693 (as
cited in USEPA, 2013).
B-41
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Appendix C:
1,2,3-Trichloropropane
An appendix from:
Final Regulatory Determination 4 Support Document
EPA Report 815-R-21-001
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Contents
Contents C-2
Exhibits C-3
Abbreviations C-4
C, 1 Contaminant Background and Chemical and Physical Properties C-6
C.2 Sources and Environmental Fate C-7
C.2.1 Production, Use, and Release C-7
C.2.2 Environmental Fate C-10
C.3 Health Effects C-ll
C.3.1 Toxicokinetics C-ll
C.3.2 Available Health Effects Assessments C-12
C.3.3 Health Effects C-14
C.3.4 Basis of 11RI. C-16
C.3.5 Health Effects Data Gaps C-17
C.4 Occurrence C-17
C.4.1 Occurrence in Ambient Water C-17
C.4.2 Occurrence in Drinking Water C-24
C.4.3 Other Data C-42
C.5 Analytical Methods C-43
C.6 Treatment Technologies C-44
C.7 References C-44
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Exhibits
Exhibit C-l: Chemical Structure of 1,2,3-Trichloropropane C-6
Exhibit C-2: Physical and Chemical Properties of 1,2,3-Trichloropropane C-7
Exhibit C-3: IUR Reported Annual Manufacture and Importation of 1,2,3-
Trichloropropane in the United States, 1986-2006 (pounds) C-8
Exhibit C-4: CDR Reported Annual Manufacture and Importation of 1,2,3-
Trichloropropane in the United States, 2011-2015 (pounds) C-8
Exhibit C-5: Environmental Releases (in pounds) of 1,2,3-Trichloropropane in the United
States, 1995-2016 C-9
Exhibit C-6: Summary and State Count of Total Releases and Total Surface Water
Discharges of 1,2,3-Trichloropropane, 1995-2016 C-10
Exhibit C-7: Available Health Effects Assessments for 1,2,3-Trichloropropane C-12
Exhibit C-8: 1,2,3-Trichloropropane NAWQA Data - Summary of Detected
Concentrations C-19
Exhibit C-9: 1,2,3-Trichloropropane NAWQA Data - Summary of Samples C-19
Exhibit C-10: 1,2,3-Trichloropropane NAWQA Data - Summary of Sites C-20
Exhibit C-l 1: 1,2,3-TrichloropropaneNWIS Data, 1991 -2016 C-22
Exhibit C-12: 1,2,3-Trichloropropane STORET Data - Summary of Detected
Concentrations C-23
Exhibit C-13: 1,2,3-Trichloropropane STORET Data - Summary of Samples and Sites C-23
Exhibit C-14: 1,2,3-Trichloropropane STORET Data - Summary of States C-23
Exhibit C-15: 1,2,3-Trichloropropane Occurrence Data from UCMR 3 Assessment
Monitoring - Summary of Reported Concentrations C-26
Exhibit C-16: 1,2,3-Trichloropropane National Occurrence Measures Based on UCMR 3
Assessment Monitoring Data - Summary of Samples C-26
Exhibit C-17: 1,2,3-Trichloropropane National Occurrence Measures Based on UCMR 3
Assessment Monitoring Data - Summary of System and Population Served Data -
All Reported Detections C-27
Exhibit C-18: 1,2,3-Trichloropropane Occurrence Data from UCM Rounds 1 and 2 -
Summary of Reported Concentrations C-29
Exhibit C-19: 1,2,3-Trichloropropane Occurrence Data from UCM Rounds 1 and 2 -
Summary of Samples C-29
Exhibit C-20: 1,2,3-Trichloropropane Occurrence Data from UCM Rounds 1 and 2 -
Summary of System and Population Served Data - All Reported Detections C-30
Exhibit C-21: 1,2,3-Trichloropropane State Drinking Water Occurrence Data - Summary
of Reported Concentrations C-32
Exhibit C-22: 1,2,3-Trichloropropane State Drinking Water Occurrence Data - Summary
of Samples C-34
Exhibit C-23: 1,2,3-Trichloropropane State Drinking Water Occurrence Data - Summary
of Systems C-37
Exhibit C-24: 1,2,3-Trichloropropane Data from Public-Supply Wells (Toccalino et al.,
2010) - Summary of Reported Concentrations C-41
Exhibit C-25: 1,2,3-Trichloropropane Data from Public-Supply Wells (Toccalino et al.,
2010) - Summary of Samples C-41
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Abbreviations
123-TCP
1,2,3-Trichloropropane
ADAF
Age Dependent Adjustment Factor
ADD
Acceptable Daily Dose
AwwaRF
American Water Works Association Research Foundation
BMD10
Benchmark Dose at 10% Extra Risk
BMDADJ
Adjusted Benchmark Dose
BMDL10
Benchmark Dose Limit at 10% Extra Risk
BMDLADJ
Adjusted Benchmark Dose Limit
BW
Body Weight
CalEPA
California Environmental Protection Agency
CAS
Chemical Abstracts Service
CCL 3
Third Contaminant Candidate List
CCL 4
Fourth Contaminant Candidate List
CCR
Consumer Confidence Report
CDC
Centers for Disease Control and Prevention
CDR
Chemical Data Reporting
CSF
Cancer Slope Factor
CWS
Community Water System
CWSS
Community Water System Survey
CYP450
Cytochrome P-450
DBCP
l,2-Dibromo-3-Chloro-Propane
DNA
Deoxyribonucleic Acid
DWI
Drinking Water Intake
EDB
1,2-Dibromoethane
EPA
Environmental Protection Agency
EPCRA
Emergency Planning And Community Right-to-Know Act
EPI Suite™
Estimation Programs Interface Suite™
F
Fraction of a 70-year lifetime applicable to the age period
GAC
Granular Activated Carbon
GWUDI
Groundwater Under the Direct Influence of Surface Water
HRC®
Hydrogen Release Compound®
HRL
Health Reference Level
ICR
Information Collection Request
IRIS
Integrated Risk Information System
IUR
Inventory Update Reporting
Kh
Henry's Law Constant
Koc
Organic Carbon Partitioning Coefficient
Kow
Octanol-Water Partitioning Coefficient
LCMRL
Lowest Concentration Minimum Reporting Level
LD50
Median Lethal Dose
LOAEL
Lowest Observed Adverse Effect Level
LOD
Limit of Detection
MDL
Method Detection Limit
MOA
Mode of Action
MRL
Minimum Reporting Limit
MTBE
Methyl Tertiary Butyl Ether
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NAWQA
National Water Quality Assessment
ND
No Detection
NHANES
National Health and Nutrition Examination Survey
NIRS
National Inorganics and Radionuclides Survey
NJDEP
New Jersey Department of Environmental Protection
NOAEL
No Observed Adverse Effect Level
NPDWR
National Primary Drinking Water Regulation
NTP
National Toxicology Program
NWIS
National Water Information System
OW
Office of Water
PA
Principal Aquifer
POD
Point of Departure
PWS
Public Water System
RfD
Reference Dose
RNA
Ribonucleic Acid
RSD
Relative Standard Deviation
SDWIS
Safe Drinking Water Information System
SDWIS/Fed
Safe Drinking Water Information System/Federal Version
SIM
Selected Ion Monitoring
SOC
Synthetic Organic Compound
STORET
Storage And Retrieval Data System
SYR2
Second Six-Year Review
SYR3
Third Six-Year Review
TRI
Toxic Release Inventory
TSCA
Toxic Substances Control Act
UCM
Unregulated Contaminant Monitoring
UCMR
Unregulated Contaminant Monitoring Rule
UCMR 1
First Unregulated Contaminant Monitoring Rule
UCMR 2
Second Unregulated Contaminant Monitoring Rule
UCMR 3
Third Unregulated Contaminant Monitoring Rule
UF
Uncertainty Factor
USGS
United States Geological Survey
VOC
Volatile Organic Compound
WQP
Water Quality Portal
WRF
Water Research Foundation
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Appendix C: 1,2,3-Trichloropropane
The Environmental Protection Agency (EPA) evaluated 1,2,3-trichloropropane as a
candidate for regulation as a drinking water contaminant under the fourth Contaminant
Candidate List (CCL 4) Regulatory Determinations process. Information on the CCL 4 process is
found in Chapter 1. Background on data sources used to evaluate CCL 4 chemicals is found in
Chapter 2.
This appendix presents information and analysis specific to 1,2,3-trichloropropane,
including background information on the contaminant, information on contaminant sources and
environmental fate, an analysis of health effects, an analysis of occurrence in ambient and
drinking water, and information about the availability of analytical methods and treatment
technologies. EPA is not making a regulatory determination for 1,2,3-trichloropropane at this
C.l Contaminant Background and Chemical and Physical Properties
1,2,3-Trichloropropane is a halogenated alkane. It is produced as a chemical intermediate
in industry and has also been used as a paint and varnish remover, solvent, degreasing agent, and
chemical intermediate. It has also been found as an impurity in some soil fumigants. Synonyms
for 1,2,3-trichloropropane include allyl trichloride, trichlorohydrin, and glycerol trichlorohydrin
(HSDB, 2016).
Exhibit C-l presents the structural formula for 1,2,3-trichloropropane. Physical and
chemical properties and other reference information are listed in Exhibit C-2.
time.
Exhibit C-1: Chemical Structure of 1,2,3-Trichloropropane
CI
CI
CI
Source: USEPA, 2019a
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Exhibit C-2: Physical and Chemical Properties of 1,2,3-Trichloropropane
Property
Data
Chemical Abstracts Service (CAS)
Registry Number
96-18-4 (ChemlDPIus, 2018)
EPA Pesticide Chemical Code
Not applicable
Chemical Formula
C3H5CI3 (ChemlDPIus, 2018)
Molecular Weight
147.43 g/mol (HSDB, 2016)
Color/Physical State
Colorless liquid (HSDB, 2016)
Boiling Point
158 °C (HSDB, 2016)
Melting Point
-13.9 °C (HSDB, 2010)
Density
1.3889 g/mL at 20 °C (HSDB, 2010)
Freundlich Adsorption Coefficient
1,080 (|ig/g)(L/|ig)1/n (Speth and Miltner, 1990)
Vapor Pressure
3.69 mm Hg at 25 °C (HSDB, 2016)
Henry's Law Constant (Kh)
0.000343 atm-m3/mol at 25 °C (HSDB, 2016)
Log Kow
2.27 (dimensionless) (HSDB, 2016)
Koc
77 and 95 L/kg (HSDB, 2016)
Solubility in Water
1,750 mg/L at 25 °C (HSDB, 2016)
Other Solvents
Slightly soluble in carbon tetrachloride; soluble in ethanol, ethyl ether and
chloroform (HSDB, 2016)
Conversion Factors
(at 25 °C, 1 atm)
1 ppm (v/v) = 0.166 mg/m3
1 mg/m3 = 6.02 ppm (v/v)
(calculated)
Note: Many of these properties are temperature-dependent. Values are given for properties at 20-25°C unless
otherwise noted. Due to varying experimental conditions, and due to the variabilities associated with modeling, the
standard information sources may provide a range of values. Where more than one value was available from these
sources, one value was selected for this table based on best professional judgment.
C.2 Sources and Environmental Fate
C.2.1 Production, Use, and Release
Production data for 1,2,3-trichloropropane are available from EPA's Inventory Update
Reporting (IUR) and Chemical Data Reporting (CDR) programs, and industrial release data are
available from EPA's Toxics Release Inventory (TRI), as described below. Additional
information about these sources is provided in Chapter 2.
Inventory Update Reporting (IUR) / Chemical Data Reporting (CDR) Program
Under the authority of the Toxic Substances Control Act (TSCA), EPA gathers
information on production (including both manufacture and importation) of industrial chemicals.
Under the IUR, producers provided information once every four years from 1986 to 2006. Since
2012, producers have continued to provide information in accordance with the CDR Rule that
superseded the IUR in 2011. Under CDR, producers collect annual production data and report it
once every four years.
Until 2006, the IUR regulation required manufacturers and importers of organic chemical
substances included on the TSCA Chemical Substance Inventory to report site and
manufacturing information for chemicals produced (i.e., manufactured or imported) in amounts
of 10,000 pounds or more at a single site. In 2006, the minimum threshold for reporting was
increased to 25,000 pounds and reporting began for inorganic chemicals (USEPA, 2008a).
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Among changes made under CDR, a two-tier system of reporting thresholds was implemented,
with 25,000 pounds as the threshold for some contaminants and 2,500 pounds as the threshold
for others (USEPA, 2014; USEPA, 2018). As a result of program modifications, the results from
2006 and later might not be directly comparable to results from earlier years. Under CDR, every
four years manufacturers and importers are required to report annual data from each of the
previous four years, provided that the thresholds of 2,500 or 25,000 pounds are met during at
least one of the four years (USEPA, 2018).
For the historical IUR data, EPA assigned one of eight production volume ranges for
each chemical included in the inventory. The ranges used for the 2006 reports differ slightly
from those used in the 1986 through 2002 reports, as described in Chapter 2. Exhibit C-3
presents the publicly available information on production of 1,2,3-trichloropropane in the United
States from 1986 to 2006 as reported under IUR. (Note that no data were reported for 1994.)
Reported production of 1,2,3-trichloropropane in the United States decreased between 1998 and
2006.
Exhibit C-4 presents the publicly available production data for 1,2,3-trichloropropane in
the United States from 2011 to 2015 as reported under CDR. All quantitative data on 1,2,3-
trichloropropane production during this period are withheld as confidential business information.
Exhibit C-3: IUR Reported Annual Manufacture and Importation of 1,2,3-
Trichloropropane in the United States, 1986-2006 (pounds)
Chemical Inventory Update Reporting Cycle
1986
1990
1994
1998
2002
2006
Range of
Production /
Importation
Volume
> 10 million -
50 million
> 10 million -
50 million
No Reports
> 10 million -
50 million
> 1 million -
10 million
500,000-
<1 million
Source: USEPA, 2008a
Exhibit C-4: CDR Reported Annual Manufacture and Importation of 1,2,3-
Trichloropropane in the United States, 2011-2015 (pounds)
Chemical Inventory Update Re
porting Cycle
2011
2012
2013
2014
2015
Range of Production /
Importation Volume
Withheld
Withheld
Withheld
Withheld
Withheld
"Withheld" = results not publicly available due to confidential business information.
Source: USEPA, 2018
Toxics Release Inventory (TRI)
EPA established TRI in 1987 in response to section 313 of the Emergency Planning and
Community Right-to-Know Act (EPCRA). EPCRA section 313 requires the reporting of annual
information on toxic chemical releases from facilities that meet specific criteria. This reported
information is maintained in a database accessible through TRI Explorer (USEPA, 2017a).
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Although TRI can provide a general idea of release trends, it has limitations. Not all
facilities are required to report all releases. Facilities are required to report releases if they
manufacture or process more than 25,000 pounds of a chemical or use more than 10,000 pounds
per year. Reporting requirements have changed over time (e.g., reporting thresholds have
decreased), so conclusions about temporal trends should be drawn with caution. TRI data are
meant to reflect releases and should not be used to estimate general public exposure to a
chemical (USEPA, 2019b).
TRI data for 1,2,3-trichloropropane from the years 1995 through 2016 are summarized in
Exhibit C-5 (USEPA, 2017a). On-site air emissions, which dominate reported releases in most
years, peaked in 2002 at over 92,000 pounds. Surface water discharges typically ranged in the
hundreds or thousands of pounds. There were no reported releases by underground injection.
Exhibit C-5: Environmental Releases (in Pounds) of 1,2,3-Trichloropropane in the
United States, 1995-2016
Year
On-Site Releases (in pounds)
Total Off-
Site
Releases
(in pounds)
Total On-
and Off-Site
Releases
(in pounds)
Air
Emissions
Surface
Water
Discharges
Underground
Injection
Releases to
Land
1995
11,081
1,600
0
0
0
12,681
1996
2,091
0
0
0
0
2,091
1997
6,386
62
0
0
13
6,461
1998
13,837
300
0
0
6,758
20,895
1999
13,959
2,300
0
8,189
4,412
28,860
2000
16,614
5,498
0
28
0
22,140
2001
9,528
802
0
12,084
5,887
28,301
2002
92,479
4,255
0
1,269
0
98,003
2003
9,339
3,747
0
920
250
14,256
2004
8,174
282
0
597
0
9,053
2005
1,247
200
0
15
10
1,472
2006
1,526
416
0
73
10
2,025
2007
1,126
291
0
47
10
1,474
2008
1,296
187
0
42
32
1,557
2009
1,549
208
0
43
16
1,816
2010
3,076
369
0
55
3
3,503
2011
2,984
416
0
28,070
3
31,473
2012
2,828
1,251
0
2,119
1
6,199
2013
2,724
303
0
9,510
1
12,538
2014
3,091
972
0
6,389
2
10,454
2015
2,639
1,271
0
9,426
0
13,336
2016
2,717
2,218
0
3
102
5,040
Source: USEPA, 2017a
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Exhibit C-6 presents an expanded summary of total releases and total surface water
discharges that includes the count of states reporting releases for the years 1995 through 2016
(USEPA, 2017a). Two or three states each year reported releases of 1,2,3-trichloropropane. No
more than one state each year reported releases to surface water. (For the purposes of TRI,
"state" counts include the District of Columbia and U.S. territories in addition to the 50 states.)
Exhibit C-6: Summary and State Count of Total Releases and Total Surface Water
Discharges of 1,2,3-Trichloropropane, 1995-2016
Year
Total Release
(in pounds)
Count of States
with Releases
Total Surface
Water
Discharges
(in pounds)
Count of States
with Surface
Water
Discharges
1995
12,681
3
1,600
1
1996
2,091
2
0
0
1997
6,461
2
62
1
1998
20,895
3
300
1
1999
28,860
3
2,300
1
2000
22,140
2
5,498
1
2001
28,301
3
802
1
2002
98,003
2
4,255
1
2003
14,256
3
3,747
1
2004
9,053
2
282
1
2005
1,472
3
200
1
2006
2,025
3
416
1
2007
1,474
3
291
1
2008
1,557
3
187
1
2009
1,816
3
208
1
2010
3,503
3
369
1
2011
31,473
3
416
1
2012
6,199
3
1,251
1
2013
12,538
3
303
1
2014
10,454
3
972
1
2015
13,336
2
1,271
1
2016
5,040
2
2,218
1
Source: USEPA, 2017a
C.2.2 Environmental Fate
As discussed in Chapter 2, the measures used by EPA to assess mobility include (where
available) the organic carbon partitioning coefficient (Koc), log octanol-water partitioning
coefficient (log Kow), Henry's Law Constant (Kh), water solubility and vapor pressure. A vapor
pressure of 3.69 mm Hg at 25 degrees C indicates that if it is released to air, 1,2,3-
trichloropropane will exist in the vapor phase. Koc values of 77 and 95 L/kg suggest that 1,2,3-
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trichloropropane will be mobile in both soil and water and will not adsorb to sediment in water.
With a Kh of 0.000343 atm-m3/mol and a vapor pressure of 3.69 mm Hg, 1,2,3-trichloropropane
is expected to volatilize from surface water and from wet and dry soils. Bioconcentration of
1,2,3-trichloropropane in aquatic organisms is expected to be low, and biodegradation is not
expected to be significant in water or soil. Trials with several soil types, including both
biologically-active and sterile soils indicate a half-life of 2.7 days (HSDB, 2016). Because the
half-life of 2.7 days was observed in sterile soils, the loss is inferred to be caused by
volatilization.
Chapter 2 presents scales used by EPA to informally rank chemical contaminants' likely
mobility (understood as their tendency to partition to water rather than other media) and
persistence as "high," "moderate," or "low" based on physical and chemical properties (see
Exhibit 2-2 and Exhibit 2-3). For 1,2,3-trichloropropane, Koc values of 77 and 95 L/kg and a
water solubility of 1,750 mg/L predict a high likelihood of partitioning to water. The log Kow of
2.27 and a Kh of 0.000343 atm-m3/mol predict a moderate likelihood of partitioning to water.
The BIOWIN (v4.10) module of EPA's Estimation Program Interface (EPI Suite™;
USEPA, 2012a) uses several models to predict biodegradation, including complete degradation
to a primary metabolite and complete degradation to carbon dioxide and water. The predictions
are not half-lives and therefore cannot be directly compared to the Persistence scales in Table 2-
2, although BIOWIN uses the same time frames as the Persistence scales. BIOWIN predicts
complete degradation of 1,2,3-trichloropropane to a primary metabolite in days-weeks and
complete degradation to carbon dioxide and water in weeks-months. Other models used in
BIOWIN indicate that 1,2,3-trichloropropane does not degrade fast, suggesting low to moderate
persistence.
C.3 Health Effects
C.3.1 Toxicokinetics
No human toxicokinetic information is currently available for 1,2,3-trichloropropane
(USEPA, 2009a). In experimental animals, estimates of absorbed oral dose are 75 percent and 68
percent in male and female rats, respectively, and 84 percent in male mice. After absorption,
1,2,3-trichloropropane is rapidly distributed, extensively metabolized, and efficiently cleared in
experimental animals, with a 23-hour half-life observed in male rats. Radio-labeled 1,2,3-
trichloropropane has been detected in the forestomach, intestines, liver, and kidneys of rats and
mice 24 hours after administration. Toxicokinetic data from experimental animal studies
demonstrate the ability of 1,2,3-trichloropropane or its metabolites to bind to intracellular
macromolecules (e.g., proteins, nucleic acids). Cytochrome P-450 (CYP450) or glutathione
conjugation appear to be involved in the oxidation of 1,2,3-trichloropropane in rodents; however,
detailed information on the metabolism of 1,2,3-trichloropropane in experimental animals is
currently unavailable. Evidence for the involvement of CYP450 in the metabolism of 1,2,3-
trichloropropane is supported by in vitro data indicating that human microsomes can form 1,3-
dichloroacetone from 1,2,3-trichloropropane in the presence of reduced nicotinamide adenine
dinucleotide phosphate. The primary route of excretion of 1,2,3-trichloropropane metabolites in
rats and mice is through urine. Researchers have identified N-acetyl-S-(2-hydroxy-3-
chloropropyl)cysteine, l,3-(2-propanol)-bis-S-(N-acetylcysteine), N-acetyl-S-(2-hydroxy-2-
carboxyethyl)cysteine, 2,3-dichloropropionic acid, 2-chloroethanol, ethylene glycol, and oxalic
acid as potential urinary metabolites of 1,2,3-trichloropropane (USEPA, 2009a).
C-ll
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C.3.2 Available Health Effects Assessments
Exhibit C-7 presents a summary of the available health effects assessments 1,2,3-
trichloropropane. As indicated by the bolded row, the 2009 Integrated Risk Information System
(IRIS) assessment (USEPA, 2009a) was selected for use in the calculation of the Health
Reference Level (HRL) (see Section C.3.4 below for details on that calculation).
Exhibit C-7: Available Health Effects Assessments for 1,2,3-Trichloropropane
For the Lifetime HA
For the 10 s Cancer Risk
Health
Year
Concentration
Cancer
Assessment
RfD
Principal
CSF
Principal
Descriptor
(mg/kg/day)
study
(mg/kg/day)"1
study
EPA Office of
Water (OW)
Drinking Water
Health Advisory
1989
0.006
NTP,
1983(a,b)
No Value
NA
No value
1992 with an
addendum in
Agency for Toxic
Substances and
Disease Registry
2011 (2019
draft for public
comment is
No Value
NA
No value
NA
No value
(ATSDR)
available, but
not summarized
here)
California EPA
NTP,
1993
Public Health
Goal
2009
0.0057
NTP, 1993
25
No value
EPA IRIS
2009
0.004
NTP, 1993
30
NTP,
1993
Likely to be
carcinogenic
to humans
EPA searched peer-reviewed, publicly available health assessments from EPA program
offices, from other national and international programs, and from state programs to obtain
toxicity values, such as Reference Doses (RfD) and Cancer Slope Factors (CSF), for derivation
of the HRL.
The EPA Office of Water (OW) published a drinking water health advisory for 1,2,3-
trichloropropane in 1989 (USEPA, 1989). The health advisory presents an RfD of 0.006
mg/kg/day for 1,2,3-trichloropropane, based on studies by the National Toxicology Program
(NTP), a 5 day/week, 120-day oral gavage study in rats (NTP, 1983a) and a 5 day/week, 120-day
oral gavage study in mice (NTP, 1983b). A lowest-observed-adverse-effect level (LOAEL) of 16
mg/kg/day from these studies was associated with hematological effects in rats and a lower brain
weight ratio in female mice (NTP, 1983a,b). The no-observed-adverse-effect level (NOAEL)
reported from the rat and mice studies was 8 mg/kg/day (NTP, 1983a,b). A ratio of 5/7 was
applied to the NOAEL of 8 mg/kg/day to account for the 5 day/week exposure. An uncertainty
factor (UF) of 1,000 was then applied to account for the uncertainties associated with using a
NOAEL from an animal study with a subchronic exposure duration (USEPA, 1989).
The California EPA (CalEPA) published an assessment and public health goal for 1,2,3-
trichloropropane in 2009 (CalEPA, 2009). CalEPA calculated an acceptable daily dose (ADD)
value of 5.7 |ig/kg/day (0.0057 mg/kg/day) for 1,2,3-trichloropropane based on a 5 day/week,
17-week gavage study conducted in rats (NTP, 1993). Critical effects of decreased erythrocyte
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counts, hemoglobin, and mean hematocrit were observed in female rats at doses of 16 mg/kg/day
or greater. The ADD was based on the NOAEL of 8 mg/kg/day (NTP, 1993), to which a ratio of
5/7 was applied to account for the 5 day/week exposure. A total uncertainty factor of 1,000 was
applied to account for human variability (10), interspecies differences (10), and extrapolation
from a subchronic to chronic duration (10). The CalEPA assessment also presents a CSF of 25
(mg/kg/day)"1 for 1,2,3-trichloropropane, based on the same NTP (1993) study. The CSF is based
on the lower 95th percent confidence limit on the dose associated with a 10 percent increase in
forestomach tumors in female mice and low dose linear extrapolation (CalEPA, 2009).
The most recent health assessment that has been conducted for 1,2,3-trichloropropane is
the EPA IRIS ToxicologicalReview of 1,2,3-Trichloropropane (USEPA, 2009a). For 1,2,3-
trichloropropane, an RfD of 0.004 mg/kg/day was developed based on the critical effect of
increased absolute liver weight in male F344/N rats administered doses of 0, 3, 10, or 30
mg/kg/day of 1,2,3-trichloropropane by gavage for five days per week in a two-year bioassay
(NTP, 1993). The point of departure (POD) was identified utilizing the benchmark dose
modeling approach. The benchmark dose at 10 percent extra risk (BMDio) and the benchmark
dose limit at 10 percent extra risk (BMDLio) corresponding to the 95 percent lower bound on the
dose associated with a 10 percent increase in mean absolute liver weight were estimated to be 3.8
mg/kg/day and 1.6 mg/kg/day, respectively (USEPA, 2009a). The BMDio and BMDLio were
each multiplied by 5/7 to adjust for approximate continuous daily exposures, resulting in an
adjusted benchmark dose (BMDadj) and adjusted benchmark dose limit (BMDLadj) of 2.70
mg/kg/day and 1.1 mg/kg/day, respectively. A total uncertainty factor of 300, for intraspecies
differences (10), interspecies variability (10), and database deficiencies (3), was applied to the
BMDLadj to calculate the RfD (USEPA, 2009a).
The EPA IRIS assessment also presents a CSF for 1,2,3-trichloropropane (USEPA,
2009a). The critical study used to derive the EPA IRIS CSF of 30 (mg/kg/day)"1 for 1,2,3-
trichloropropane is the same NTP (1993) chronic duration oral bioassay gavage study used to
develop the RfD. In the NTP (1993) study, F344/N rats and B63Fi mice were administered
1,2,3-trichloropropane in doses of 0, 3, 10, or 30 mg/kg/day (for the rats) and 6, 20, or 60
mg/kg/day (for the mice) by gavage for five days per week for two years. Statistically significant
and dose-related increases in the formation of multiple tumors were reported in both sexes of the
two species. In rats, statistically significant increases in incidences of tumors were reported for
the oral cavity, forestomach, pancreas, kidney, preputial gland, clitoral gland, mammary gland,
and Zymbal's gland. In mice, statistically significant increases in incidences of tumors were
reported for the oral cavity, forestomach, liver, Harderian gland, and uterus. The CSF is based on
alimentary system squamous cell neoplasms, liver adenomas or carcinomas, Harderian gland
adenomas, and uterine/cervix adenomas or adenocarcinomas in female mice. The POD was
determined and a multistage Weibull model and a linear low-dose extrapolation approach from
the POD was used to estimate human carcinogenic risk associated with 1,2,3-trichloropropane
exposure due to its mutagenic mode of carcinogenic action. USEPA (2009a) noted that the
observed dose-response relationships do not continue linearly above exposure levels greater than
0.6 mg/kg/day (the value that represents the human equivalent dose that corresponds to the POD
for the female alimentary system tumors). Thus, USEPA (2009a) recommends that the CSF
should not be used for exposures above this level.
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C.3.3 Health Effects
Systemic (Noncancer)
As described in EPA's ToxicologicalReview of 1,2,3-Trichloropropane (USEPA,
2009a), irritation of eyes, nose and throat in humans was demonstrated upon exposure of male
and female study subjects to 100 ppm 1,2,3-trichloropropane via inhalation for 15 minutes
(Silverman et al., 1946). Oral median lethal dose (LD50) values are reported to range from 150
mg/kg up to 500 mg/kg body weight in rats (WHO, 2003). In a study by Lag et al. (1991) in
which male rats were administered 1,2,3-trichloropropane at doses ranging from 147 to 441
mg/kg through intraperitoneal injection, dose-dependent increases in kidney/body weight ratio,
urea excretion, and mortality were observed after 48 hours (USEPA, 2009a). As described in
EPA's Toxicological Review of 1,2,3-Trichloropropane (USEPA, 2009a), a 120-day rat and mice
study was conducted by NTP (1993) to determine appropriate doses for the 2-year chronic rat
and mice studies described above. In rats, the 17-week LOAEL determined for hepatocellular
necrosis in males was 32 mg/kg/day, and the LOAEL determined for hepatocellular necrosis in
females was 125 mg/kg/day. The LOAEL in male rats for increased sorbitol dehydrogenase was
63 mg/kg/day. In addition, the LOAEL for a decrease in pseudocholinesterase was 32 mg/kg/day
in male rats and 8 mg/kg/day in female rats. The LOAEL for renal tubular necrosis was 125
mg/kg/day in male rats. The LOAEL for epithelial necrosis of the nasal turbinates was 125
mg/kg/day in both male and female rats. In mice, the 17-week LOAEL determined for
regenerative lung lesions was 125 mg/kg/day for males and 63 mg/kg/day for females. For liver
lesions and liver necrosis, the LOAEL was 125 mg/kg/day for both male and female mice
(USEPA, 2009a).
In a 90-day study performed by Merrick et al. (1991), Sprague-Dawley male and female
rats were administered 1,2,3-trichloropropane in corn oil by gavage (USEPA, 2009a). The
LOAEL for inflammation-associated myocardial necrosis in male rats was 1.5 mg/kg/day. The
LOAEL for plasma cell hyperplasia in the mandibular lymph node was 7.4 mg/kg/day in male
rats and 1.5 mg/kg/day in female rats (USEPA, 2009a).
In a 90-day study performed by Villeneuve et al. (1985), Sprague-Dawley male and
female rats were exposed to 1,2,3-trichloropropane in drinking water for seven days per week
(USEPA, 2009a). LOAELs of 113 to 149 mg/kg/day were determined for increased liver weight
in males and females and increased serum cholesterol in females (USEPA, 2009a).
Developmental/Reproductive
Hardin et al. (1981) noted maternal toxicity in rats exposed to intraperitoneal injections of
1,2,3-trichloropropane of 37 mg/kg/day from gestational day 1 to 15 (USEPA, 1989). Johannsen
et al. (1988) described the results of single generation inhalation toxicity studies of 1,2,3-
trichloropropane in rats, and reported reduced body weight gain in high dose adult groups, but no
differences in some reproductive outcomes such as litter size and pup body weight (USEPA,
1989; USEPA 2009a). In a Johannsen et al. (1988) 13-week study, the LOAEL for decreased
body weight in female rats was 15 ppm, the LOAEL for increased relative liver weight in male
and female rats was 5 and 15 ppm (respectively), the LOAEL for increased relative lung weights
in female rats was 15 ppm, the LOAEL for increased kidney weights in male rats was 50 ppm,
and a LOAEL of 5 ppm was identified for both peribronchial lymphoid hyperplasia in male rats
and hemaptopoiesis of the spleen in female rats (USEPA, 2009a).
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An NTP (1990) fertility and reproduction assessment was conducted in CD-I mice. Mice
were exposed to 0, 30, 60, or 120 mg/kg/day 1,2,3-trichloropropane by gavage for 126 days. A
LOAEL of 60 mg/kg/day was identified for decreased number of pregnancies per fertile mouse
pair at the fourth and fifth breeding (USEPA, 2009a). In an additional experiment performed in
this NTP (1990) assessment, a LOAEL of 120 mg/kg/day was identified in treated females for
decreased number of pups per litter, decreased male pup weight, and decreased proportion of
males per litter. In still another experiment performed for this NTP (1990) assessment, a LOAEL
of 120 mg/kg/day was identified for decreased fertility and mating indices and a LOAEL of 30
mg/kg/day was identified for lengthened estrous cycle (USEPA, 2009a). This study indicates
fetal susceptibility, and shows that fertility and reproduction are adversely affected by 1,2,3-
trichloropropane exposure.
Cancer Data and Classification
Under the Agency's Guidelines for Carcinogenic Risk Assessment (USEPA, 2005a), the
EPA IRIS (USEPA, 2009a) concluded that 1,2,3-trichloropropane is "likely to be carcinogenic to
humans" based on statistically significant and dose-related increases in the formation of multiple
tumors in both male and female F344/N rats and B6C3Fi mice from an NTP (1993) 2-year
gavage study. In rats, statistically significant increases in incidences of tumors of the oral cavity,
forestomach, pancreas, kidney, preputial gland, clitoral gland, mammary gland, and Zymbal's
gland were reported. In mice, statistically significant increases in the incidences of tumors of the
oral cavity, forestomach, liver, Harderian gland, and uterus were reported (NTP, 1993; USEPA,
2009a).
The hypothesized mode of action (MOA) for 1,2,3-trichloropropane tumorigenicity in
animals involves mutagenicity through reactive metabolites (USEPA, 2009a). In vivo studies
that directly measure mutagenicity are currently unavailable. The mutagenic MOA for 1,2,3-
trichloropropane is supported by evidence of mutagenic response in short-term bacterial studies
with microsomal activation; induction of the formation of wing spots in the somatic mutation and
recombination test in Drosophila melanogaster; covalent binding of metabolites to hepatic
protein, deoxyribonucleic acid (DNA), and ribonucleic acid (RNA); and DNA strand breaks in
hepatocytes in rat studies (USEPA, 2009a). The mutagenic MOA for 1,2,3-trichloropropane is
also supported by a dose-dependent increase in the formation of DNA adducts (e.g., S-[l-
(hydroxymethyl)-2-(N7-guanyl)ethyl]glutathione) in various organs of B6C3Fi mice and
F344/N/N rats, with DNA adducts found in tumor-forming organs of male rats and mice; and a
dose-dependent increase in the formation of 1,3-dichloroacetone (a DNA-reactive intermediate
metabolite), as well as reactive episulfonium ion metabolites (USEPA, 2009a). EPA concluded
that the weight of available evidence supports a mutagenic MOA for 1,2,3-trichloropropane-
induced carcinogenicity and recommended application of age-dependent adjustment factors
(ADAFs) to the slope factor in accordance with the Supplemental Guidance for Assessing
Susceptibility from Early-Life Exposure to Carcinogens (USEPA, 2005b) to account for some of
the potential differences in age-dependent response to carcinogens with a mutagenic MOA.
Potentially Sensitive Groups/Lifestages
The above-described information supports the conclusion that 1,2,3-trichloropropane acts
to induce carcinogenesis via a mutagenic MOA. Children exposed to carcinogens with a
mutagenic MOA are assumed to have increased early-life susceptibility and a potentially
increased carcinogenic susceptibility during early-life exposures (NTP, 1993; USEPA, 2005b,
2009a), and, therefore, represent a potentially sensitive group/lifestage.
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C.3.4 Basis of HRL
The HRL was calculated based on the EPA IRIS CSF for 1,2,3-trichloropropane of 30
(mg/kg/day)"1 (USEPA, 2009a). The critical study used to derive the EPA IRIS CSF for 1,2,3-
trichloropropane is the NTP (1993) chronic duration oral bioassay gavage study in F344/N rats
and B6C3Fi mice, which reports statistically significant and dose-related increases in the
formation of multiple tumors in both sexes of the two species. In rats, statistically significant
increases in incidences of tumors of the oral cavity, forestomach, pancreas, kidney, preputial
gland, clitoral gland, mammary gland, and Zymbal's gland were reported. In mice, statistically
significant increases in incidences of tumors of the oral cavity, forestomach, liver, Harderian
gland, and uterus were reported. The CSF is based on the alimentary system squamous cell
neoplasms, liver hepatocellular adenomas or carcinomas, Harderian gland adenomas, and
uterine/cervix adenomas or adenocarcinomas observed in female mice. USEPA (2009a) selected
the multistage Weibull model to determine the POD to reflect the influence of competing risks
and intercurrent mortality observed in the NTP (1993) study. This model incorporates the time
and the dose at which death-with-tumors occurred. As described above, evidence indicates that
1,2,3-trichloropropane carcinogenicity occurs due to a mutagenic MO A; thus, a linear, low-dose
approach from the POD was used to determine the CSF (USEPA, 2009a).
The HRL for the cancer effects of 1,2,3-trichloropropane is 0.0004 |ig/L, based on the
EPA IRIS CSF for 1,2,3-trichloropropane of 30 (mg/kg/day)"1 (USEPA, 2009a). The CSF of 30
per mg/kg was calculated for adult exposures and does not take into account presumed early-life
susceptibility to 1,2,3-trichloropropane exposure. The evidence described above indicates that
1,2,3-trichloropropane carcinogenicity occurs via a mutagenic MO A. EPA provides guidance on
assessing early life carcinogen exposure (USEPA, 2005a; USEPA, 2005b), and children
potentially exposed to mutagenic carcinogens can be assumed to have the potential for increased
early-life susceptibility to carcinogens. Therefore, for mutagenic carcinogens, EPA recommends
that risk assessors apply special adjustment factors to a given CSF which are dependent on age
(ADAFs, or age-dependent adjustment factors). Section 5.4.5 of the IRIS assessment for 1,2,3-
trichloropropane describes application of the ADAFs to the CSF. EPA recommends the
application of these ADAFs when estimating cancer risks from early life (<16 years of age)
exposure to 1,2,3-trichloropropane (USEPA, 2009a).
The HRL is generally calculated as follows for cancer risk (for mutagenic carcinogens,
taking into consideration ADAFs per USEPA 2005b guidelines), and is finally rounded to one
significant figure:
lxlO-6 y (BWi*Fi*ADAFi\
HRL ~ CSF * Li V DWIi )
_ lxlO-6 y iBWi * Fj * ADAFt\
HRL— * / ( )
30 Zj i\ DWIt >
Hg
HRL = 0.0004
L
DWI = Drinking Water Intake (L/day); based on adult default value of 2.5 L/day
(USEPA, 2011)
BW = Body weight (kg); based on adult default value of 80 kg (USEPA, 2011)
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EPA - OGWDW Final Regulatory Determination 4 Support Document - App C, 1,2,3-Trichloropropane
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CSF = Cancer Slope Factor value ((mg/kg/day)"1); selected based on protocol hierarchy
F = The fraction of a 70-year lifetime applicable to the age period, namely 2/70 for birth
to two-years, 14/70 for two years to sixteen years, and 54/70 for sixteen years to seventy
years
ADAF = Age Dependent Adjustment Factor: ADAF = 10 for the age group birth to two-
years, ADAF=3 for two years to sixteen years, and ADAF=1 for and sixteen years to
seventy years
C.3.5 Health Effects Data Gaps
Additional studies that could provide useful information include developmental and
multigenerational reproduction studies (beyond two-generations) for 1,2,3-trichloropropane,
further MOA studies for tumor development, and additional MOA or toxicodynamic studies for
hepatotoxicity induced by 1,2,3-trichloropropane.
C.4 Occurrence
This section presents data on the occurrence of 1,2,3-trichloropropane in ambient water
and drinking water in the United States. As described in section C.3, an HRL of 0.0004 |ig/L was
calculated for 1,2,3-trichloropropane based on carcinogenic effects. HRLs are risk-derived
concentrations against which EPA evaluates the occurrence data to determine if contaminants
occur at levels of potential public health concern. Occurrence data from various sources
presented below are analyzed with respect to the HRL and one-half the HRL. When possible,
estimates of the population exposed at concentrations above the HRL and one-half the HRL are
presented.
For additional background information about data sources used to evaluate occurrence,
please refer to Chapter 2.
C.4.1 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the ambient sources of most drinking water. Contaminant
occurrence in ambient water provides information on the potential for contaminants to adversely
affect drinking water supplies. Occurrence data for 1,2,3-trichloropropane in ambient water are
available from the United States Geological Survey (USGS) National Water-Quality Assessment
(NAWQA) program, the USGS National Water Information System (NWIS) database, EPA's
legacy Storage and Retrieval Data System (STORET) data available through the Water Quality
Portal (WQP), and several published USGS studies.
United States Geological Survey (USGS) National Water-Quality Assessment (NAWQA)
Ambient Water Analyses
USGS instituted the NAWQA program in 1991 to examine ambient water quality status
and trends in the United States. The NAWQA program generates high quality contaminant
occurrence and other water quality parameter data for significant watersheds and aquifers across
the nation. The program collects data on surface water and groundwater chemistry, hydrology,
land use, stream habitat, and aquatic life in parts or all of nearly all 50 States. The program is
designed to apply nationally consistent methods to provide a uniform basis for contaminant
occurrence comparisons and assessments among study basins across the country and over time.
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The occurrence assessments can also serve to facilitate interpretation of natural and
anthropogenic factors affecting national water quality. For more detailed information on
NAWQA program design and implementation, refer to Leahy and Thompson (1994) and
Hamilton et al. (2004).
The process of sampling, analysis, and data synthesis is divided into cycles of
approximately ten years: Cycle 1 covered 1991-2001, Cycle 2 covered 2002-2012, and Cycle 3 is
ongoing and covers 2013-2023. Study units are sampled and analyzed on a staggered schedule
within each cycle. Each NAWQA cycle begins with a two-year startup phase for planning and
retroactive analysis, followed by a three-year intensive data collection phase, and finally a five-
year phase for analyzing the data, developing reports, and continuing a low level of monitoring
(NRC, 2012).
During Cycle 1 (1991-2001), 51 study units were sampled. Data were gathered from
6,307 wells from 272 groundwater networks or clusters and from 6,400 sampling points at 505
surface water monitoring sites, primarily rivers and streams but also some lakes and reservoirs
(NRC, 2002).In Cycle 2 (2002-2012), the number of study units was reduced from 51 to 42
(NRC, 2012). Long-term stream monitoring was established at 113 streams representing 8 major
river basins. Long-term groundwater monitoring was established at sites representing 20
principal aquifers with more than 10 to 15 years of consistent monitoring data available (Rowe et
al., 2013).
Sampling for Cycle 3 is currently underway (2013-2023). Surface water monitoring will
be conducted at 313 sites, increased from 113 sites in Cycle 2 (Rowe et al., 2013). Groundwater
assessments in Cycle 3 will be designed to evaluate status and trends at the principal aquifer
(PA) and national scales. Assessments are planned in 24 PAs that account for the majority of
current and future national groundwater use for drinking water. Data available through 2017 are
presented in this report. For more details on the Cycle 3 sampling design, refer to Rowe et al.
(2010; 2013).
EPA's analysis of the NAWQA data is a simple, non-parametric occurrence analysis that
provides summary statistics to characterize contaminant occurrence. EPA calculated detection
frequencies as the percentage of samples and the percentage of sites with at least one detection,
without any censoring or weighting. (A detection is an analytical result equal to or greater than
the reporting level.) EPA reported the minimum and maximum detected concentrations and
calculated other descriptive statistics including the median, 90th percentile, and 99th percentile
concentrations (based only on samples with detections). Reporting levels varied over time during
the NAWQA program. In some cases, therefore, the minimum concentration reported as a
detection could be lower than the highest reporting level.
Exhibit C-8 through Exhibit C-10 present analyses of the 1,2,3-trichloropropane
NAWQA data, downloaded from the WQP in September 2018 (WQP, 2018). In all three cycles,
1,2,3-trichloropropane was detected in less than 3 percent of samples. All detections in all three
cycles were greater than the HRL. The median concentrations based on detections were 0.411
|ig/L, 0.167 |ig/L, and 0.026 |ig/L in Cycle 1, Cycle 2, and Cycle 3, respectively. As noted
above, NAWQA data are ambient water data, not finished drinking water data.
Note that there may be some overlap between the NAWQA data assessment presented
here and summaries of individual NAWQA studies presented below.
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Exhibit C-8: 1,2,3-Trichloropropane NAWQA Data - Summary of Detected
Concentrations
Site Type
Concentration Value of Detections (|jg/L)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Cycle 1 (1991 -2001)
Groundwater
0.085
0.460
1.14
2.77
2.92
Surface Water
0.12
0.160
0.179
0.179
0.179
All Sites
0.085
0.411
1.10
2.76
2.92
Cycle 2 (2002-2012)
Groundwater
0.069
0.167
0.614
0.688
0.696
Surface Water
ND
ND
ND
ND
ND
All Sites
0.069
0.167
0.614
0.688
0.696
Cycle 3 (2013-2017)
Groundwater
0.002
0.026
0.126
0.784
0.971
Surface Water
ND
ND
ND
ND
ND
All Sites
0.002
0.026
0.126
0.784
0.971
Source: WQP, 2018
Exhibit C-9: 1,2,3-Trichloropropane NAWQA Data - Summary of Samples
Site Type
No. of
Samples
Detection Frequency
(detections are results > reporting level)
No. of
Samples
with
Detections
%
Samples
with
Detections
No. of
Samples
with
Detections
> 1/2 HRL
%
Samples
with
Detections
> 1/2 HRL
No. of
Samples
with
Detections
> HRL
%
Samples
with
Detections
> HRL
Cycle 1 (1991 -2001)
Groundwater
4,847
56
1.16%
56
1.16%
56
1.16%
Surface Water
1,471
4
0.27%
4
0.27%
4
0.27%
All Sites
6,318
60
0.95%
60
0.95%
60
0.95%
Cycle 2 (2002-2012)
Groundwater
4,997
8
0.16%
8
0.16%
8
0.16%
Surface Water
532
0
0.00%
0
0.00%
0
0.00%
All Sites
5,529
8
0.14%
8
0.14%
8
0.14%
Cycle 3 (2013-2017)
Groundwater
1,433
42
2.93%
42
2.93%
42
2.93%
Surface Water
160
0
0.00%
0
0.00%
0
0.00%
All Sites
1,593
42
2.64%
42
2.64%
42
2.64%
Source: WQP, 2018
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Exhibit C-10: 1,2,3-Trichloropropane NAWQA Data - Summary of Sites
Site Type
No. of
Sites
Detection Frequency
(detections are results > reporting level)
No. of
Sites with
Detections
% Sites
with
Detections
No. of
Sites with
Detections
> 1/2 HRL
% Sites
with
Detections
> 1/2 HRL
No. of
Sites with
Detections
> HRL
% Sites
with
Detections
> HRL
Cycle 1 (1991 -2001)
Groundwater
4,426
47
1.06%
47
1.06%
47
1.06%
Surface Water
178
1
0.56%
1
0.56%
1
0.56%
All Sites
4,604
48
1.04%
48
1.04%
48
1.04%
Cycle 2 (2002-2012)
Groundwater
3,200
8
0.25%
8
0.25%
8
0.25%
Surface Water
56
0
0.00%
0
0.00%
0
0.00%
All Sites
3,256
8
0.25%
8
0.25%
8
0.25%
Cycle 3 (2013-2017)
Groundwater
1,355
41
3.03%
41
3.03%
41
3.03%
Surface Water
54
0
0.00%
0
0.00%
0
0.00%
All Sites
1,409
41
2.91%
41
2.91%
41
2.91%
Source: WQP, 2018
NA WQA Volatile Organic Compounds (VOC) National Synthesis: Random and
Focused VOC Surveys, 1999-2001
Through a series of National Synthesis efforts, the USGS NAWQA program prepares
comprehensive analyses of data on topics of particular concern. These National Synthesis
assessments aggregate NAWQA contaminant occurrence and water quality parameter data from
individual study units and other sources to provide a national overview.
The Volatile Organic Compound (VOC) National Synthesis began in 1994. The most
comprehensive VOC National Synthesis reports to date are one random survey and one focused
survey funded by the Water Research Foundation (WRF) (formerly known as AwwaRF) and
carried out by the USGS in collaboration with the Metropolitan Water District of Southern
California and Oregon Health & Science University. The random survey (Grady, 2002) targeted
surface waters and groundwaters used as source water by community water systems (CWSs).
Samples were taken from the source waters of 954 CWSs in 1999 and 2000. The random survey
was designed to be nationally representative of CWS source waters. In the focused survey
(Delzer and Ivahnenko, 2003), 451 samples were taken from source waters serving 134 CWSs
between 1999 and 2001. These surface waters and groundwaters were chosen because they were
suspected or known to contain methyl tertiary butyl ether (MTBE). The focused survey was
designed to provide insight into temporal variability and anthropogenic factors associated with
VOC occurrence. Details of the monitoring plan for the two studies, including detection limits
(which in many cases are significantly lower than the common reporting level), are provided by
Ivahnenko et al. (2001).
The random survey sampled groundwater and surface water sources used by 954
geographically representative CWSs in different size categories (Grady, 2002). At a reporting
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level of 0.2 |ig/L, the national random survey of source waters (Grady, 2002) found 1,2,3-
trichloropropane in one sample (0.1 percent of all samples, 0.17 percent of groundwater samples,
and 0 percent of surface water samples). The single detection was in groundwater at a
concentration of 0.31 |ig/L.
The focused survey investigated 134 CWS sources (56 surface water and 78
groundwater) between 1999 and 2001 (Delzer and Ivahnenko, 2003). These surface waters and
groundwaters were chosen because they were suspected or known to contain VOCs. At the
reporting level of 0.2 (J,g/L, the national focused survey (Delzer and Ivahnenko, 2003) did not
detect 1,2,3-trichloropropane in any of the CWS source waters sampled. In addition, the focused
survey provided results for 1,2,3-trichloropropane below the common reporting level. At levels
as low as the method detection limit (MDL) (0.027 (J,g/L), 1,2,3-trichloropropane was found in
3.8 percent of the CWS source waters sampled (3.8 percent of groundwater sites and 3.7 percent
of surface water sites). Detected concentrations ranged from 0.03 [j,g/L to 0.09 [j,g/L (Delzer and
Ivahnenko, 2003).
NA WQA Volatile Organic Compounds (VOC) National Synthesis: Compilation of
Historical VOC Monitoring Data, 1985-1995
The VOC National Synthesis also includes a compilation of historical VOC monitoring
data from multiple studies (Squillace et al., 1999). These data were collected between 1985 and
1995 from 2,948 drinking water and non-drinking water wells in both rural and urban areas.
Sampling was done by local, state, and federal agencies, and data were reviewed by USGS to
ensure they met data quality criteria.
Multiple investigators collected samples from 264 urban wells and 1,729 rural wells. At a
reporting level of 0.2 (J,g/L, the detection frequency for 1,2,3-trichloropropane was 0.38 percent
(one detection) in urban areas and 0.58 percent (ten detections) in rural areas. Detections ranged
from the reporting level (0.2 |ig/L) to 1.1 |ig/L. In urban wells, the single detection was 0.2 |ig/L;
in rural wells, the median detected concentration was 0.5 |ig/L.
National Water Information System (NWIS) Data
The National Water Information System (NWIS) is the Nation's principal repository of
water resources data USGS collects from more than 1.5 million sites (USGS, 2016). NWIS-Web
is the general online interface to the USGS NWIS database. Discrete water-sample and time-
series data are available from sites in all 50 States, including 5 million water samples with 90
million water-quality results. All USGS water quality and flow data are stored in NWIS,
including site characteristics, streamflow, groundwater level, precipitation, and chemical
analyses of water, sediment, and biological media, though not all parameters are available for
every site. NWIS houses the NAWQA data and includes other USGS data from unspecified
projects. NWIS contains many more samples at many more sites than the NAWQA Program.
Although NWIS is comprised of primarily ambient water data, some finished drinking water data
are included as well. This section presents analyses of non-NAWQA data in NWIS, downloaded
from the WQP in December 2017 (WQP, 2017). These data do not overlap with the results
presented in Exhibit C-8 through Exhibit C-10.
The results of the non-NAWQA NWIS 1,2,3-trichloropropane analysis are presented in
Exhibit C-l 1. 1,2,3-Trichloropropane was detected in approximately 1 percent of samples (115
out of 18,130 samples) and at approximately 1 percent of sites (94 out of 8,299 sites). The
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median concentration based on detections was equal to 0.045 |ig/L. (Note that the NWIS data are
presented as downloaded; potential outliers were not evaluated or excluded from the analysis.)
Exhibit C-11: 1,2,3-Trichloropropane NWIS Data, 1991 -2016
Site Type
Detection Frequency
(detections are results > reporting level)
Concentration Values
(of detections, in |jg/L)
No. of
Samples
No. of
Samples
with
Detections
No.
of
Sites
No. of
Sites with
Detections
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Groundwater
15,208
112
7,460
91
0.004
0.041
0.396
15.9
22
Surface
Water
2,895
3
852
3
0.1
0.100
0.730
0.973
1
Finished
Water
27
0
20
0
ND
ND
ND
ND
ND
All Sites
18,130
115
8,299
94
0.004
0.045
0.399
15.6
22
Source: WQP, 2017
Storage and Retrieval (STORET) Data / Water Quality Portal (WQP)
From its launch in 1999 until it was decommissioned in June 2018, EPA's STORET Data
Warehouse was collaboratively populated with raw biological, chemical, and physical data from
surface water and groundwater sampling by federal, state and local agencies, Native American
tribes, volunteer groups, academics, and others. Legacy STORET data are accessible through the
WQP: https://www.waterqualitvdata.us/portal/.
STORET data are from monitoring locations in all 50 states as well as multiple territories
and jurisdictions of the United States. Most data are from ambient waters, but in some cases
finished drinking water data are included as well. STORET's data quality limitations include
variations in the extent of national coverage and data completeness from parameter to parameter.
Data may have been collected as part of targeted, rather than randomized, monitoring.
This section presents analyses of STORET data, downloaded from the WQP in December
2017 (WQP, 2017). EPA reviewed STORET surface water and groundwater data from wells and
surface water data from lakes, rivers/streams, and reservoirs (WQP, 2017). The WQP also
included public water system (PWS) data from four states (Indiana, Missouri, Ohio, and
Washington); EPA reviewed these as well (WQP, 2017). It is unclear if the PWS data were
collected prior to or subsequent to treatment.
The results of the STORET analysis for 1,2,3-trichloropropane are presented in Exhibit
C-12 through Exhibit C-14. Samples were collected between 1988 and 2016. Of the 4,240 sites
sampled, 2,364 (55.8 percent) reported detections of 1,2,3-trichloropropane. Detected
concentrations ranged from 0 |ig/L to 2,000 |ig/L. The 90th percentile concentration of detections
was equal to 10 |ig/L. Minimum detected concentrations are reported in Exhibit C-12; these
minimum values may be indicative of the reporting levels used. (A minimum value of zero, on
the other hand, could represent a detection that was entered into the database as a non-numerical
value (e.g., "Present").)
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Exhibit C-12: 1,2,3-Trichloropropane STORET Data - Summary of Detected
Concentrations
Source Water Type
Concentration Value of Detections (|jg/L
Minimum1
Median
90th Percentile
Maximum
Groundwater
0
1
10
2,000
Surface Water
0.008
0.22
0.5
110
Total
0
1
10
2,000
PWS
0
0
0
0.5
Source: WQP, 2017
1A minimum value of zero may represent a detection that was entered into the database as a non-numerical value
(e.g., "Present").
Exhibit C-13: 1,2,3-Trichloropropane STORET Data - Summary of Samples and
Sites
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Total
Number
of Sites
Sites with Detections
Number
Percent
Number
Percent
Groundwater
26,512
15,068
56.83%
3,757
2,100
55.90%
Surface Water
1,804
897
49.72%
483
264
54.66%
Total
28,316
15,965
56.38%
4,240
2,364
55.75%
PWS
1,282
1,093
85.26%
187
186
99.47%
Source: WQP, 2017
Exhibit C-14: 1,2,3-Trichloropropane STORET Data - Summary of States
Source Water
Type
Total
Number of
States
States with Detections
Number
Percent
Groundwater
14
8
57.14%
Surface Water
26
9
34.62%
Total1
30
13
43.33%
PWS
2
2
100.00%
Source: WQP, 2017
1 The number of states with groundwater data plus the number of
states with surface water data may not equal the "Total" number of
states providing data because some states provided both
groundwater and surface water data.
Additional Ambient Water Studies
For the National Highway Runoff Data and Methodology Synthesis, USGS conducted a
review of 44 highway and urban runoff studies implemented since 1970 (Lopes and Dionne,
1998). 1,2,3-Trichloropropane was an analyte in three stormwater studies: in Maricopa County,
Arizona at a reporting level of 0.2 (J,g/L, in Colorado Springs, Colorado at a reporting level of 0.2
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[j,g/L, and in Dallas/Fort Worth, Texas at reporting levels ranging from 0.2 [j,g/L to 10 (J,g/L.
1,2,3-Trichloropropane was not detected in any of the three studies. (In the text, Lopes and
Dionne appear to state that 1,2,3-trichloropropane was detected in runoff in the Texas study, but
that is incorrect.) Note that the data from these studies might also be included in the NWIS
results presented earlier.
C.4.2 Occurrence in Drinking Water
Data sources reviewed by the Agency for information on contaminant occurrence in
drinking water included: EPA's first, second, and third Unregulated Contaminant Monitoring
Rules (UCMR 1, UCMR 2, UCMR 3); Rounds 1 and 2 of the Agency's Unregulated
Contaminant Monitoring (UCM) program that preceded the Unregulated Contaminant
Monitoring Rule (UCMR); EPA's Information Collection Rule; EPA's National Inorganics and
Radionuclides Survey (NIRS); and a range of others as discussed in Chapter 2. Among the
sources reviewed, the following sources had data and information on 1,2,3-trichloropropane
occurrence in drinking water. These data and information are discussed in this section.
• EPA's Third Unregulated Contaminant Monitoring Rule (UCMR 3).
Rounds 1 and 2 of EPA's Unregulated Contaminant Monitoring (UCM) Program.
State drinking water monitoring programs.
EPA's Community Water System Survey (CWSS).
USGS source water and drinking water studies.
Additional studies from the literature.
Note that there may be some overlap as sources with different purposes and audiences
may have reported the same underlying data. UCMR 3 and UCM Round 1 and Round 2 are
national data sources. Other data sources profiled in this section are considered "supplemental"
sources. Also note that the presentation of NWIS and STORET results in the ambient water
section, above, includes some finished water data and/or miscellaneous data from PWSs.
Primary Data Sources
EPA's Third Unregulated Contaminant Monitoring Rule (UCMR 3) 2013-2015
UCMR 3 monitoring, designed to provide nationally representative contaminant
occurrence data, was conducted from 2013 through 2015. UCMR 3 List 1 Assessment
Monitoring occurrence data are available for 1,2,3-trichloropropane. For UCMR 3, all large and
very large public water systems or PWSs (serving between 10,001 and 100,000 people and
serving more than 100,000 people, respectively), plus a statistically representative national
sample of 800 small PWSs (serving 10,000 people or fewer), were required to conduct
Assessment Monitoring during a 12-month period between January 2013 and December 2015.1
Surface water (and groundwater under the direct influence of surface water (GWUDI)) sampling
points were monitored four times during the applicable year of monitoring, and groundwater
sampling points were monitored twice during the applicable year of monitoring. See USEPA
(2012b) and USEPA (2019c) for more information on the UCMR 3 study design and data
analysis.
1 Only 799 small systems submitted Assessment Monitoring results.
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The design of UCMR 3 permits estimation of national occurrence by multiplying the total
number of systems (or population served) in the nation in a system size category by the percent
of systems expected to exceed a specified threshold. An extrapolation methodology is applied to
small systems because not all small systems were required to participate in the UCMR 3
Assessment Monitoring. Because all large and very large systems were required to participate in
the UCMR 3 Assessment Monitoring, national estimates of occurrence in these size categories
can be done using survey census figures rather than extrapolation. Total national occurrence is
estimated by summing the extrapolated figures for small systems and the census figures for the
large and very large systems.
Exhibit C-15 through Exhibit C-17 provide an overview of 1,2,3-trichloropropane
occurrence results from UCMR 3 Assessment Monitoring. Laboratories participating in UCMR 3
were required to report values at or above minimum reporting levels (MRLs) defined by EPA.
The MRLs are established to ensure reliable and consistent results from the array of laboratories
needed for a national monitoring program and are set based on the capability of multiple
commercial laboratories prior to the beginning each UCMR round. The MRL used for 1,2,3-
trichloropropane in the UCMR 3 survey was 0.03 |ig/L (77 FR 26072; USEPA, 2012b). Exhibit
C-15 shows a statistical summary of 1,2,3-trichloropropane concentrations by system size and
source water type (including the minimum, median, 90th percentile, 99th percentile, and
maximum). Exhibit C-16 presents a sample-level summary of the results. Exhibit C-17 shows
system-level results, including national extrapolations. Results are presented relative to the MRL.
(As noted above and in Chapter 2, values at or above reporting thresholds like MRLs are referred
to as "detections" in this document.) Note that since the MRL for 1,2,3-trichloropropane is
higher than the HRL, all detections greater than or equal to the MRL are also greater than one-
half the HRL and the HRL. Thus, no additional tables are included that present occurrence
results relative to one-half the HRL or the HRL.
As noted above, UCMR 3 monitoring was required at a representative sample of small
systems and at all large and very large systems. As a reminder that the figures from large and
very large systems represent a census of systems in those categories, results in those categories
are labelled "CENSUS" in Exhibit C-17. No extrapolation was necessary in these categories, as
it was for the small systems, to derive national estimates of occurrence in these exhibits. National
estimates of occurrence are reported separately in each system size and source water category,
and also in aggregate.
A total of 36,848 finished water samples for 1,2,3-trichloropropane were collected from
4,916 systems. 1,2,3-Trichloropropane was measured > MRL in 0.69 percent of UCMR 3
samples. Reported 1,2,3-trichloropropane concentrations for these "positive" results ranged from
0.03 |ig/L (the MRL) to 1.02 |ig/L. Of 4,916 systems, 67 (1.4 percent of systems, serving 2.5
percent of the PWS-served population) reported at least one detection greater than or equal to the
MRL and, therefore, also greater than the HRL of 0.0004 |ig/L. Extrapolating these findings
suggests that an estimated 381 PWSs serving 6.1 million people nationally would have at least
one 1,2,3-trichloropropane detection greater than the MRL.
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Exhibit C-15: 1,2,3-Trichloropropane Occurrence Data from UCMR 3 Assessment
Monitoring - Summary of Reported Concentrations
Source Water Type
Concentration Values (in |jg/L)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Small Systems (serving < 10,000 people)
Groundwater
0.03
0.09
0.16
0.16
0.16
Surface Water
ND
ND
ND
ND
ND
All Small Systems
0.03
0.09
0.16
0.16
0.16
Large Systems
serving 10,001 -100,000 people) — CENSUS
Groundwater
0.03
0.09
0.30
0.57
0.64
Surface Water
0.03
0.05
0.09
0.12
0.12
All Large Systems
0.03
0.07
0.28
0.54
0.64
Very Large Systems (serving > 100,000 people) — CENSUS
Groundwater
0.03
0.06
0.45
0.98
1.02
Surface Water
0.03
0.08
0.23
0.30
0.31
All Very Large
Systems
0.03
0.07
0.25
0.95
1.02
All Systems
All Water Systems
0.03
0.07
0.28
0.81
1.02
Source: USEPA, 2017b
ND = no detections in this category
Exhibit C-16: 1,2,3-Trichloropropane National Occurrence Measures Based on
UCMR 3 Assessment Monitoring Data - Summary of Samples
Source Water Type
Total # of
Samples
Samples with Detections
> MRL (0.03 |jg/L)
Number
Percent
Small Systems (serving < 10,000 people)
Groundwater
1,849
6
0.32%
Surface Water
1,417
0
0.00%
All Small Systems
3,266
6
0.18%
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
11,654
134
1.15%
Surface Water
14,808
29
0.20%
All Large Systems
26,462
163
0.62%
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
2,009
49
2.44%
Surface Water
5,111
38
0.74%
All Very Large Systems
7,120
87
1.22%
All Systems
All Water Systems
36,848
256
0.69%
Source: USEPA, 2017b
Note: Give that the HRL is 75 times lower than the MRL, there is a
broad range of potential contaminant concentrations that could be in
exceedance of the HRL but below the MRL.
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Exhibit C-17: 1,2,3-Trichloropropane National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data
- Summary of System and Population Served Data - All Reported Detections
Source Water Type
UCMR 3 Sample
Number With At Least One
Value > MRL (0.03 ng/L)
Percent With At Least One Value
> MRL
National Inventory1
> MRL
National Estimate2
> MRL
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Groundwater
527
1,498,845
3
6,467
0.57%
0.43%
55,700
38,730,597
317
167,000
Surface Water
272
1,250,215
0
0
0.00%
0.00%
9,728
20,007,917
0
0
All Small Systems
799
2,749,060
3
6,467
0.38%
0.24%
65,428
58,738,514
317
167,000
Large Systems (serving 10,001 -100,000 people) - CENSUS
Groundwater
1,451
37,113,173
44
1,221,459
3.03%
3.29%
1,470
37,540,614
44
1,220,000
Surface Water
2,258
69,538,817
9
402,379
0.40%
0.58%
2,310
70,791,005
9
402,000
All Large Systems
3,709
106,651,990
53
1,623,838
1.43%
1.52%
3,780
108,331,619
53
1,620,000
Very Large Systems (serving > 100,000 people) - CENSUS
Groundwater
68
16,355,951
5
2,184,810
7.35%
13.36%
68
16,355,951
5
2,180,000
Surface Water
340
115,158,260
6
2,144,011
1.76%
1.86%
343
120,785,622
6
2,140,000
All Very Large
Systems
408
131,514,211
11
4,328,821
2.70%
3.29%
411
137,141,573
11
4,330,000
All Systems
All Water Systems
4,916
240,915,261
67
5,959,126
1.36%
2.47%
69,619
304,211,706
381
6,120,000
Source: USEPA, 2017b
1 The small system national inventory numbers for systems and population served by systems were derived from a freeze of the December 2010 Safe Drinking Water
Information System/Federal version (SDWIS/Fed) data. These counts are based on all community and non-transient non-community water systems that served 10,000
people or fewer. All large and very large systems were required to conduct UCMR 3 Assessment Monitoring; thus, the national inventory numbers for the large and very
large systems are based on the number of systems expected to complete UCMR 3 monitoring. SDWIS/Fed inventory data from 2010 were used for the UCMR 3
national extrapolations as these data were consistent with the UCMR 3 inventory data at the timeframe of the UCMR 3 sample design.
2 National estimates for the small systems are generated by multiplying the UCMR 3 national statistical sample findings of system/population percentages and national
system/population inventory numbers for PWSs. National estimates for the large and very large systems are based directly on the UCMR 3 results, since this was a
census. Due to rounding, some calculations may appear to be slightly off.
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Unregulated Contaminant Monitoring (UCM) Program Data, 1988 -1997
In 1987, EPA initiated the UCM program, which collected contaminant occurrence data
from drinking water at PWSs. This program was implemented in two rounds. The first round of
UCM monitoring (UCM Round 1) generally extended from 1988 to 1992 and included
monitoring for 34 VOCs. The second round of UCM monitoring (UCM Round 2) generally
extended from 1993 to 1997 and included monitoring for 13 synthetic organic compounds
(SOCs) and sulfate in addition to the 34 VOCs from UCM Round 1 monitoring. All the
monitored contaminants were unregulated at the time of monitoring. A total of 38 states provided
contaminant occurrence data under UCM Round 1, and 34 states provided data under UCM
Round 2. Samples were analyzed for 1,2,3-trichloropropane under both UCM Round 1 and
Round 2.
The contaminant occurrence data submitted under the UCM monitoring reflected neither
a census nor a statistically representative sample. Therefore, EPA assessed potential biases in the
data and developed a "national cross-section" separately from the UCM Round 1 and Round 2
data submitted by the states. The UCM Round 1 national cross-section of data from 24 states
consists of more than 3.3 million analytical results from approximately 22,000 systems. The
UCM Round 2 national cross-section of data from 20 states consists of more than 3.7 million
analytical results from approximately 27,000 systems. While EPA recognizes that some
limitations exist, the agency believes that the national cross-sections are indicative of national
occurrence and provide a reasonable estimate of the overall distribution and the central tendency
of contaminant occurrence across the United States. For more details on the UCM Round 1 and 2
data and the occurrence estimation methodology, refer to USEPA (2001a), USEPA (2003), and
USEPA (2008b).
Exhibit C-18 through Exhibit C-20 present a summary of the occurrence data from UCM
Rounds 1 and 2 for 1,2,3-trichloropropane. In Round 1, 1,2,3-trichloropropane was reported as
present at 0.25 percent of PWSs, affecting 6.65 percent of the population served in the cross-
section analysis, and in 0.29 percent of PWSs, affecting 6.39 percent of the population in the all-
states analysis. The minimum reported detection in UCM Round 1 was 0.10 |ig/L in both the all-
states and the cross-section states analyses.
In Round 2, 1,2,3-trichloropropane was reported as present at 0.08 percent of PWSs,
affecting 0.06 percent of the population served in the cross-section analysis, and in 0.07 percent
of PWSs, affecting 0.05 percent of the population in the all-states analysis. In Round 2, the
minimum detected concentration was 0.03 |ig/L in both the all-states analysis and the cross-
section states analysis. Minimum reported concentrations are listed in Exhibit C-18; these
minimum values may be indicative of reporting levels used.
To calculate national extrapolations, the percent of systems (or population served)
estimated to exceed a specified threshold is multiplied by the total number of systems (or
population served) in the nation. However, national extrapolations based on UCM data should be
interpreted with caution because neither "all-states" data nor cross-section data constitute
statistically representative samples. See Chapter 2 for additional information on national
extrapolations. The results of national extrapolations are presented in Exhibit C-20.
Because Round 1 and Round 2 involve different groups of states, conclusions about
temporal trends cannot necessarily be drawn from comparison of findings from the two Rounds.
(Temporal trends could, however, be inferred from state-level findings in the case of states with
findings from both Rounds.)
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Exhibit C-18: 1,2,3-Trichloropropane Occurrence Data from UCM Rounds 1 and 2
- Summary of Reported Concentrations
Source Water Type
Concentration Values (|jg/L)
Minimum
Median
90th Percentile
99th Percentile
Maximum
UCM Round 1 - 24-State Cross-Section (1988-1992)
Groundwater
0.1
0.92
6.00
91.27
112
Surface Water
0.4
0.87
1
1
1
All Systems
0.1
0.92
6.00
90.10
112
UCM Round 1 - All States (1988-1992)
Groundwater
0.1
0.93
6.00
89.22
112
Surface Water
0.4
0.90
1.25
1.48
1.5
All Systems
0.1
0.93
5.52
87.47
112
UCM Round 2 - 20-State Cross-Section (1993-1997)
Groundwater
0.1
0.50
15.40
2,525
3,000
Surface Water
0.03
1.30
11.05
19.11
20
All Systems
0.03
0.5
16.60
2,347
3,000
UCM Round 2 - All States (1993-1997)
Groundwater
0.1
0.50
15.40
2,525
3,000
Surface Water
0.03
1.30
11.05
19.11
20
All Systems
0.03
0.5
16.60
2,347
3,000
Source: USEPA, 2001b
Exhibit C-19: 1,2,3-Trichloropropane Occurrence Data from UCM Rounds 1 and 2
- Summary of Samples
Source Water
Type
Total Number
of Samples
Samples with Reported
Detections
Number
Percent
UCM Round 1 - 24-State Cross-Section (1988-1992)
Groundwater
48,974
72
0.15%
Surface Water
8,231
4
0.05%
All Samples
57,205
76
0.13%
UCM Round 1 - All States (1988-1992)
Groundwater
51,260
79
0.15%
Surface Water
9,030
6
0.07%
All Samples
60,290
85
0.14%
UCM Round 2 - 20-State Cross-Section (1993-1997)
Groundwater
82,318
17
0.02%
Surface Water
15,637
6
0.04%
All Samples
97,955
23
0.02%
C-29
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EPA - OGWDW Final Regulatory Determination 4 Support Document - App C, 1,2,3-Trichloropropane
January 2021
Source Water
Type
Total Number
of Samples
Samples with Reported
Detections
Number
Percent
UCM Round 2 - All States (1993-1997]
Groundwater
92,755
17
0.02%
Surface Water
18,808
6
0.03%
All Samples
111,563
23
0.02%
Source: USEPA, 2001b
Note: Given that the HRL is so much lower than minimum reported
concentrations (see Exhibit C-18), which may be indicative of
reporting levels used, there may be a broad range of potential
contaminant concentrations that could be in exceedance of the
HRL but unreported.
Exhibit C-20: 1,2,3-Trichloropropane Occurrence Data from UCM Rounds 1 and 2
- Summary of System and Population Served Data - All Reported Detections
Source Water
Type
Total Number
Detections
Number
Percent
National
Extrapolation1
System
Populatio
Systems
Populatio
Systems
Population
Systems
Population
UCM Round 1 - 24-State Cross-Section (1988-1992)
Groundwater
15,771
41,472,224
40
4,744,558
0.25%
11.44%
151
11,300,000
Surface Water
1,758
43,772,741
4
620,290
0.23%
1.42%
13
2,390,000
All Systems 2
17,392
80,614,987
44
5,364,848
0.25%
6.65%
164
17,800,000
UCM Round 1 - All States (1988-1992)
Groundwater
16,132
43,240,507
47
4,751,873
0.29%
10.99%
173
10,800,000
Surface Water
1,910
45,777,158
5
621,790
0.26%
1.36%
14
2,290,000
All Systems 2
17,884
84,100,127
52
5,373,663
0.29%
6.39%
189
17,100,000
UCM Round 2 - 20-State Cross-Section (1993-1997)
Groundwater
21,441
25,784,020
13
12,288
0.06%
0.05%
36
46,900
Surface Water
2,647
44,760,057
6
30,822
0.23%
0.07%
12
116,000
All Systems 2
24,088
70,544,077
19
43,110
0.08%
0.06%
51
163,000
UCM Round 2 - All States (1993-1997)
Groundwater
24,528
30,703,266
13
12,288
0.05%
0.04%
31
39,400
Surface Water
3,010
52,783,235
6
30,822
0.20%
0.06%
11
98,600
All Systems 2
27,538
83,486,501
19
43,110
0.07%
0.05%
45
138,000
Source: USEPA, 2001b
1 National extrapolations are generated by multiplying the UCM findings of system/population percentages and
national system/population inventory numbers for PWSs developed from EPA's Safe Drinking Water Information
System (SDWIS), the CWSS, and UCMR (see Chapter 2 for discussion). Because some water systems have more
than one source water type, extrapolations are generated separately for "Groundwater", "Surface Water", and "All
Systems"; thus, the number of extrapolated groundwater systems plus the number of extrapolated surface Water
systems does not add up to the extrapolated "All Systems" numbers.
2 The number of groundwater systems plus the number of surface water systems is not equal to "All Systems"
because some water systems have more than one source water type.
C-30
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EPA - OGWDW Final Regulatory Determination 4 Support Document - App C, 1,2,3-Trichloropropane
January 2021
Supplemental Data Sources
State Monitoring Data, 1983-2011
Because there is no available national database that receives and stores all relevant data
regarding the occurrence of regulated contaminants in public drinking water systems, EPA
conducts voluntary data requests from the states, territories, and tribes in support of national
occurrence assessments. These assessments are part of the Six-Year Review. Under the second
and third Six-Year Review (SYR2 and SYR3), a few states submitted PWS occurrence data for
unregulated contaminants along with the requested data on regulated contaminants. EPA was
able to supplement the data on unregulated contaminants by downloading additional publicly
available monitoring data from state websites. For SYR2, the result was a collection of
unregulated contaminant monitoring data from nine states and other entities, such as tribes,
territories, and EPA Regions. For SYR3, the dataset of unregulated contaminant monitoring data
included results from 14 states/entities. For both rounds of the Six-Year Review, these
unregulated data provide varying degrees of completeness in their coverage of the states/entities
and are not necessarily representative of occurrence in those states/entities. For more details on
the Six-Year Review Information Collection Request (ICR) Dataset for SYR2, refer to USEPA
(2009b). For more details on the SYR3 ICR Dataset, refer to EPA's SYR3 occurrence analysis
(USEPA, 2016).
Drinking water occurrence data for 1,2,3-trichloropropane were available from
California, Florida, Illinois, North Carolina, Ohio, Region 9 tribes, South Dakota, Texas, and
Wisconsin under SYR2 (1983-2005) and American Samoa, California, Florida, Michigan,
Navajo Nation, Pennsylvania Region 9 Tribes, Washington, and Wisconsin under SYR3 (2006-
2011). 2 Results are presented in Exhibit C-21 through Exhibit C-23. The exhibits do not include
estimates of population served because the 1,2,3-trichloropropane data submitted under SYR2
and SYR3 represent only a small portion of all PWSs in each state. See USEPA (2009c) and
USEPA (2016) for the total number of systems that submitted SYR2 and SYR3 data,
respectively, from each state. Comprehensive information about methods used and reporting
levels is not available for this data set. Minimum detected concentrations, as reported in the
sources, are listed in Exhibit C-21; these minimum values may be indicative of reporting levels
used.
As noted above, the monitoring data from each state/entity are limited and not necessarily
representative of occurrence in the state/entity. The number of PWSs per state with 1,2,3-
trichloropropane data ranged from only 6 PWSs in Illinois SYR2 to 5,660 PWSs in the Texas
SYR2 data. Overall, reported concentrations ranged from 0.00021 |ig/L to 270 |ig/L.
2 Some states provided more than six years' worth of data to EPA in response to the SYR2 and SYR3 ICRs.
C-31
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EPA - OGWDW Final Regulatory Determination 4 Support Document - App C, 1,2,3-Trichloropropane January 2021
Exhibit C-21: 1,2,3-Trichloropropane State Drinking Water Occurrence Data -
Summary of Reported Concentrations
State
(Date
Range)
Source Water Type
(Sample Type)
Concentration Values (|jg/L)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Second Six-Year Review (SYR2)
California
(1995-2005)
Groundwater (Raw)
0.003
0.034
0.28
1.0
2.4
Groundwater (Finished)
0.005
0.02
0.14
10.0
21
Groundwater (Not Provided)1
ND
ND
ND
ND
ND
Surface Water (Raw)
0.001
0.05
2.9
20
74
Surface Water (Finished)
0.005
0.92
4.0
7.8
22
Surface Water (Not Provided)1
0.14
0.15
0.15
0.15
0.15
Not Provided2 (Raw)
ND
ND
ND
ND
ND
Not Provided3
ND
ND
ND
ND
ND
Total
0.001
0.063
3.098
11
74
Florida
(2004-2005)
Groundwater (Not Provided)1
ND
ND
ND
ND
ND
Surface Water (Not Provided)1
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
Illinois
(1998-2004)
Groundwater (Not Provided)1
ND
ND
ND
ND
ND
Surface Water (Not Provided)1
250
250
250
250
250
Total
250
250
250
250
250
North
Carolina
(1998-2005)
Groundwater (Raw)
ND
ND
ND
ND
ND
Groundwater (Finished)
0.57
0.7
0.8
0.8
0.8
Surface Water (Finished)
ND
ND
ND
ND
ND
Total
0.57
0.7
0.8
0.8
0.8
Ohio
(1998-2005)
Groundwater (Not Provided)1
0.5
0.5
0.5
0.5
0.5
Surface Water (Not Provided)1
ND
ND
ND
ND
ND
Total
0.5
0.5
0.5
0.5
0.5
Region 9
Tribes
(1998-2005)
Groundwater (Not Provided)1
1.8
3.7
3.7
3.7
3.7
Surface Water (Not Provided)1
ND
ND
ND
ND
ND
Total
1.8
3.7
3.7
3.7
3.7
South
Dakota
(1990-2007)
Groundwater (Not Provided)1
0.67
0.67
0.67
0.67
0.67
Surface Water (Not Provided)1
ND
ND
ND
ND
ND
Total
0.67
0.67
0.67
0.67
0.67
Texas
(1998-2005)
Groundwater (Not Provided)1
13
35
36
36.9
37
Surface Water (Not Provided)1
34
34
34
34
34
Not Provided2
ND
ND
ND
ND
ND
Total
13
35
35.8
36.88
37
Wisconsin
(1983-1999)
Groundwater (Not Provided)1
0.1
0.66
0.9
3
3.21
Surface Water (Not Provided)1
ND
ND
ND
ND
ND
Total
0.1
0.66
0.9
3
3.21
Wisconsin
(2000-2005)
Groundwater (Not Provided)1
3.9
3.9
3.9
3.9
3.9
Surface Water (Not Provided)1
ND
ND
ND
ND
ND
Total
3.9
3.9
3.9
3.9
3.9
C-32
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EPA - OGWDW Final Regulatory Determination 4 Support Document - App C, 1,2,3-Trichloropropane January 2021
State
(Date
Range)
Source Water Type
(Sample Type)
Concentration Values (|jg/L)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Third Six-Year Review (SYR3)
American
Samoa
(2006-2011)
Groundwater (Not Provided)1
ND
ND
ND
ND
ND
Surface Water (Not Provided)1
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
California
(2006-2011)
Groundwater (Raw)
0.003
0.1
0.5
2.0
270
Groundwater (Finished)
0.005
0.0
11.0
20.9
29
Groundwater (Not Provided)1
0.008
0.1
0.1
0.1
0.092
Surface Water (Raw)
0.002
0.0
1.1
4.2
8.2
Surface Water (Finished)
0.005
0.0
0.9
1.6
3.7
Surface Water (Not Provided)1
ND
ND
ND
ND
ND
Total
0.002
0.04
0.7884
13
270
Florida
(2006-2011)
Groundwater (Raw)
1.9
1.9
1.9
1.9
1.9
Groundwater (Not Provided)1
ND
ND
ND
ND
ND
Surface Water (Raw)
ND
ND
ND
ND
ND
Surface Water (Not Provided)1
ND
ND
ND
ND
ND
Total
1.9
1.9
1.9
1.9
1.9
Michigan
(2006-2011)
Groundwater (Not Provided)1
ND
ND
ND
ND
ND
Surface Water (Not Provided)1
ND
ND
ND
ND
ND
Not Provided3
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
Navajo
Nation
(2007-2011)
Groundwater (Not Provided)1
ND
ND
ND
ND
ND
Surface Water (Not Provided)1
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
Pennsylvan
ia
(2006-2011)
Groundwater (Raw)
ND
ND
ND
ND
ND
Groundwater (Not Provided)1
ND
ND
ND
ND
ND
Surface Water (Raw)
ND
ND
ND
ND
ND
Surface Water (Not Provided)1
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
Region 9
Tribes
(2006-2011)
Groundwater (Not Provided)1
0.00021
0.00021
0.00021
0.00021
0.00021
Surface Water (Not Provided)1
ND
ND
ND
ND
ND
Total
0.00021
0.00021
0.00021
0.00021
0.00021
Washington
(2006-2011)
Groundwater (Raw)
0.0322
0.0
0.0
0.0
0.0348
Groundwater (Finished)
ND
ND
ND
ND
ND
Groundwater (Not Provided)1
1.2
1.3
1.4
1.5
1.47
Surface Water (Raw)
ND
ND
ND
ND
ND
Surface Water (Finished)
ND
ND
ND
ND
ND
Surface Water (Not Provided)1
ND
ND
ND
ND
ND
Not Provided2 (Raw)
ND
ND
ND
ND
ND
Not Provided2 (Finished)
ND
ND
ND
ND
ND
Not Provided3
ND
ND
ND
ND
ND
Total
0.0322
1.2
1.402
1.4632
1.47
C-33
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EPA - OGWDW Final Regulatory Determination 4 Support Document - App C, 1,2,3-Trichloropropane
January 2021
State
(Date
Range)
Source Water Type
(Sample Type)
Concentration Values (|jg/L)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Wisconsin
(2006-2011)
Groundwater (Not Provided)1
ND
ND
ND
ND
ND
Surface Water (Not Provided)1
ND
ND
ND
ND
ND
Not Provided3
ND
ND
ND
ND
ND
Total
ND
ND
ND
ND
ND
Source: Data provided to EPA by states and downloaded by EPA from state websites
ND = no detections in this category
1 The results were not identified in the state
2 The results were not identified in the state
3 The results were not identified in the state
surface water.
Exhibit C-22: 1,2,3-Trichloropropane State Drinking Water Occurrence Data -
Summary of Samples
State
(Date Range)
Source Water Type
(Sample Type)
Total
Number of
Samples
All Reported Detections
Number
Percent
Second Six-Year Review (SYR2)
California
(1995-2005)
Groundwater (Raw)
49,435
1,182
2.39%
Groundwater (Finished)
5,290
116
2.19%
Groundwater (Not Provided)1
91
0
0.00%
Surface Water (Raw)
33,341
1,176
3.53%
Surface Water (Finished)
12,056
1,246
10.34%
Surface Water (Not Provided)1
269
2
0.74%
Not Provided2 (Raw)
34
0
0.00%
Not Provided3
4
0
0.00%
Total
100,520
3,722
3.70%
Florida
(2004-2005)
Groundwater (Not Provided)1
753
0
0.00%
Surface Water (Not Provided)1
3
0
0.00%
Total
756
0
0.00%
Illinois
(1998-2004)
Groundwater (Not Provided)1
7
0
0.00%
Surface Water (Not Provided)1
4
4
100%
Total
11
4
36.36%
North Carolina
(1998-2005)
Groundwater (Raw)
163
0
0.00%
Groundwater (Finished)
17,566
18
0.10%
Surface Water (Finished)
2,111
0
0.00%
Total
19,840
18
0.09%
Ohio
(1998-2005)
Groundwater (Not Provided)1
8,286
1
0.01%
Surface Water (Not Provided)1
997
0
0.00%
Total
9,283
1
0.01%
data set as having been collected from raw or finished water.
data set as having been collected from groundwater or surface water.
data set as having been collected from raw or finished groundwater or
C-34
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EPA - OGWDW Final Regulatory Determination 4 Support Document - App C, 1,2,3-Trichloropropane January 2021
State
(Date Range)
Source Water Type
(Sample Type)
Total
Number of
Samples
All Reported Detections
Number
Percent
Region 9 Tribes
(1998-2005)
Groundwater (Not Provided)1
1,026
3
0.29%
Surface Water (Not Provided)1
87
0
0.00%
Total
1,113
3
0.27%
South Dakota
(1990-2007)
Groundwater (Not Provided)1
1,057
1
0.09%
Surface Water (Not Provided)1
53
0
0.00%
Total
1,110
1
0.09%
Texas
(1998-2005)
Groundwater (Not Provided)1
27,969
6
0.02%
Surface Water (Not Provided)1
7,731
1
0.01%
Not Provided3
585
0
0.00%
Total
36,285
7
0.02%
Wisconsin
(1983-1999)
Groundwater (Not Provided)1
12,821
11
0.09%
Surface Water (Not Provided)1
407
0
0.00%
Total
13,228
11
0.08%
Wisconsin
(2000-2005)
Groundwater (Not Provided)1
4,130
1
0.02%
Surface Water (Not Provided)1
82
0
0.00%
Total
4,212
1
0.02%
Third Six-Year Review (SYR3)
American
Samoa
(2006-2011)
Groundwater (Not Provided)1
67
0
0.00%
Surface Water (Not Provided)1
0
0
0.00%
Total
67
0
0.00%
California
(2006-2011)
Groundwater (Raw)
22,799
2,421
10.62%
Groundwater (Finished)
13,547
554
4.09%
Groundwater (Not Provided)1
74
9
12.16%
Surface Water
10,684
1,807
16.91%
Surface Water (Finished)
6,957
1,232
17.71%
Surface Water (Not Provided)1
55
0
0.00%
Total
54,116
6,023
11.13%
Florida
(2006-2011)
Groundwater (Raw)
219
1
0.46%
Groundwater (Not Provided)1
1,652
0
0.00%
Surface Water (Raw)
0
0
0.00%
Surface Water (Not Provided)1
18
0
0.00%
Total
1,889
1
0.05%
Michigan
(2006-2011)
Groundwater (Not Provided)1
8,166
0
0.00%
Surface Water (Not Provided)1
665
0
0.00%
Not Provided3
39
0
0.00%
Total
8,870
0
0.00%
Navajo Nation
(2007-2011)
Groundwater (Not Provided)1
62
0
0.00%
Surface Water (Not Provided)1
0
0
0.00%
Total
62
0
0.00%
C-35
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EPA - OGWDW Final Regulatory Determination 4 Support Document - App C, 1,2,3-Trichloropropane January 2021
State
(Date Range)
Source Water Type
(Sample Type)
Total
Number of
Samples
All Reported Detections
Number
Percent
Groundwater (Raw)
45
0
0.00%
Pennsylvania
(2006-2011)
Groundwater (Not Provided)1
1,629
0
0.00%
Surface Water (Raw)
47
0
0.00%
Surface Water (Not Provided)1
246
0
0.00%
Total
1,967
0
0.00%
Region 9 Tribes
(2006-2011)
Groundwater (Not Provided)1
262
1
0.38%
Surface Water (Not Provided)1
26
0
0.00%
Total
288
1
0.35%
Groundwater (Raw)
4,525
2
0.04%
Groundwater (Finished)
3,241
0
0.00%
Groundwater (Not Provided)1
1,159
3
0.26%
Surface Water (Raw)
276
0
0.00%
Washington
Surface Water (Finished)
561
0
0.00%
(2006-2011)
Surface Water (Not Provided)1
72
0
0.00%
Not Provided2 (Raw)
96
0
0.00%
Not Provided2 (Finished)
2
0
0.00%
Not Provided3
44
0
0.00%
Total
9,976
5
0.05%
Groundwater (Not Provided)1
4,256
0
0.00%
Wisconsin
Surface Water (Not Provided)1
222
0
0.00%
(2006-2011)
Not Provided3
7
0
0.00%
Total
4,485
0
0.00%
Source: Data provided to EPA by states and downloaded by EPA from state websites
Note: Given that the HRL is so much lower than minimum reported concentrations
(see Exhibit C-21), which may be indicative of reporting levels used, there may be a
broad range of potential contaminant concentrations that could be in exceedance of
the HRL but unreported.
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from groundwater or surface
water.
3 The results were not identified in the state data set as having been collected from raw or finished
groundwater or surface water.
C-36
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EPA - OGWDW Final Regulatory Determination 4 Support Document - App C, 1,2,3-Trichloropropane
January 2021
Exhibit C-23: 1,2,3-Trichloropropane State Drinking Water Occurrence Data -
Summary of Systems
State
(Date Range)
Source Water Type
(Sample Type)
Total
Number of
Systems
Systems with Detections
Number
Percent
Second Six-Year Review (SYR2)
California
(1995-2005)
Groundwater (Raw)
3,172
117
3.69%
Groundwater (Finished)
158
16
10.13%
Groundwater (Not Provided)1
37
0
0.00%
Surface Water (Raw)
498
30
6.02%
Surface Water (Finished)
216
11
5.09%
Surface Water (Not Provided)1
14
1
7.14%
Not Provided2 (Raw)
22
0
0.00%
Not Provided3
1
0
0.00%
Total
3,748
151
4.03%
Florida
(2004-2005)
Groundwater (Not Provided)1
13
0
0.00%
Surface Water (Not Provided)1
1
0
0.00%
Total
14
0
0.00%
Illinois
(1998-2004)
Groundwater (Not Provided)1
2
0
0.00%
Surface Water (Not Provided)1
4
4
100%
Total
6
4
66.67%
North Carolina
(1998-2005)
Groundwater (Raw)
115
0
0.00%
Groundwater (Finished)
2,285
5
0.22%
Surface Water (Finished)
202
0
0.00%
Total
2,493
5
0.20%
Ohio
(1998-2005)
Groundwater (Not Provided)1
2,379
1
0.04%
Surface Water (Not Provided)1
153
0
0.00%
Total
2,532
1
0.04%
Region 9 Tribes
(1998-2005)
Groundwater (Not Provided)1
263
2
0.76%
Surface Water (Not Provided)1
16
0
0.00%
Total
279
2
0.72%
South Dakota
(1990-2007)
Groundwater (Not Provided)1
258
1
0.39%
Surface Water (Not Provided)1
23
0
0.00%
Total
281
1
0.36%
Texas
(1998-2005)
Groundwater (Not Provided)1
5,018
4
0.08%
Surface Water (Not Provided)1
489
1
0.20%
Not Provided3
153
0
0.00%
Total
5,660
5
0.09%
Wisconsin
(1983-1999)
Groundwater (Not Provided)1
1,795
11
0.61%
Surface Water (Not Provided)1
31
0
0.00%
Total
1,826
11
0.60%
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EPA - OGWDW Final Regulatory Determination 4 Support Document - App C, 1,2,3-Trichloropropane January 2021
State
(Date Range)
Source Water Type
(Sample Type)
Total
Number of
Systems
Systems with Detections
Number
Percent
Wisconsin
(2000-2005)
Groundwater (Not Provided)1
936
1
0.11%
Surface Water (Not Provided)1
22
0
0.00%
Total
958
1
0.10%
Third Six-Year Review (SYR3)
American Samoa
(2006-2011)
Groundwater (Not Provided)1
11
0
0.00%
Surface Water (Not Provided)1
0
0
0.00%
Total
11
0
0.00%
Groundwater (Raw)
2,443
69
2.82%
Groundwater (Finished)
116
18
15.52%
California
(2006-2011)
Groundwater (Not Provided)1
40
3
7.50%
Surface Water (Raw)
332
14
4.22%
Surface Water (Finished)
97
10
10.31%
Surface Water (Not Provided)1
12
0
0.00%
Total
2,818
87
3.09%
Groundwater (Raw)
3
1
33.33%
Florida
(2006-2011)
Groundwater (Not Provided)1
40
0
0.00%
Surface Water (Raw)
0
0
0.00%
Surface Water (Not Provided)1
1
0
0.00%
Total
42
1
2.38%
Groundwater (Not Provided)1
2,677
0
0.00%
Michigan
Surface Water (Not Provided)1
91
0
0.00%
(2006-2011)
Not Provided3
33
0
0.00%
Total
2,801
0
0.00%
Navajo Nation
(2007-2011)
Groundwater (Not Provided)1
46
0
0.00%
Surface Water (Not Provided)1
0
0
0.00%
Total
46
0
0.00%
Groundwater (Raw)
11
0
0.00%
Pennsylvania
(2006-2011)
Groundwater (Not Provided)1
212
0
0.00%
Surface Water (Raw)
3
0
0.00%
Surface Water (Not Provided)1
29
0
0.00%
Total
242
0
0.00%
Region 9 Tribes
(2006-2011)
Groundwater (Not Provided)1
141
1
0.71%
Surface Water (Not Provided)1
12
0
0.00%
Total
153
1
0.65%
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EPA - OGWDW Final Regulatory Determination 4 Support Document - App C, 1,2,3-Trichloropropane
January 2021
State
(Date Range)
Source Water Type
(Sample Type)
Total
Number of
Systems
Systems with Detections
Number
Percent
Groundwater (Raw)
1,629
1
0.06%
Groundwater (Finished)
1,087
0
0.00%
Groundwater (Not Provided)1
607
2
0.33%
Surface Water (Raw)
88
0
0.00%
Washington
Surface Water (Finished)
132
0
0.00%
(2006-2011)
Surface Water (Not Provided)1
35
0
0.00%
Not Provided2 (Raw)
65
0
0.00%
Not Provided2 (Finished)
2
0
0.00%
Not Provided3
22
0
0.00%
Total
2,773
3
0.11%
Groundwater (Not Provided)1
777
0
0.00%
Wisconsin
Surface Water (Not Provided)1
29
0
0.00%
(2006-2011)
Not Provided3
6
0
0.00%
Total
812
0
0.00%
Source: Data provided to EPA by states and downloaded by EPA from state
websites
Note: Given that the HRL is so much lower than minimum reported concentrations
(see Exhibit C-21), which may be indicative of reporting levels used, there may be a
broad range of potential contaminant concentrations that could be in exceedance of
the HRL but unreported.
1 The results were not identified in the state data set as having been collected from raw or finished water.
2 The results were not identified in the state data set as having been collected from groundwater or
surface water.
3 The results were not identified in the state data set as having been collected from raw or finished
groundwater or surface water.
Community Water System Survey (CWSS), 2006
The 2006 CWSS (USEPA, 2009d; USEPA, 2009e) gathered data on the financial and
operating characteristics of a random sample of CWSs nationwide. All systems serving more
than 500,000 people (94 systems in 2006) received the survey. These 94 large systems were
asked questions about concentrations of unregulated contaminants in their raw and finished
water. Of these 94 systems, 58 systems (62 percent) responded to the survey, though not all of
these systems answered every question. EPA supplemented the data set by gathering additional
information about contaminant occurrence at the 94 systems from publicly available sources
(e.g., consumer confidence reports (CCRs)).
In the 2006 CWSS, one of the 94 systems serving more than 500,000 people reported a
detection of 1,2,3-trichloropropane in a single sample, with a concentration of 400 |ig/L.
Reporting levels were not specified in this survey.
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United States Geological Survey (USGS) National Water Quality Assessment (NAWQA)
Source Water and Drinking Water Studies
Note that there may be some overlap between the NAWQA data assessment presented
earlier in the ambient water occurrence section and the summaries of NAWQA studies presented
below. The studies presented below include occurrence data from water sources for PWSs.
Organic Compounds in Source Water of Selected Community Water Systems (Hopple
et al., 2009 and Kingsbury et al., 2008), 2002-2005
As part of the NAWQA program, Hopple et al. (2009) and Kingsbury et al. (2008)
conducted studies to characterize anthropogenic organic compounds in U.S. waters used as
source waters for PWSs. Hopple et al. (2009) focused on groundwater, and Kingsbury et al.
(2008) focused on surface water. In Phase 1 of the studies, geographically diverse source water
samples were collected between October 2002 and July 2005 from nine CWSs served by streams
and from 12 aquifers. In Phase 2, USGS collected source and finished water samples at a subset
of sites between June 2004 and September 2005. The reporting level for 1,2,3-trichloropropane
was 0.18 [j,g/L for groundwater and surface water samples in Phase 1 of the studies but was not
specified for Phase 2 of the studies.
1,2,3-Trichloropropane was not detected in any of the 221 groundwater samples or 147
surface water samples collected during Phase 1 of the studies. 1,2,3-Trichloropropane was not
detected in any of the 71 raw or 71 finished water samples collected in Phase 2 of the
groundwater study. No surface water samples were analyzed for 1,2,3-trichloropropane in
Phase 2.
Volatile Organic Compounds in Drinking Water of Selected Community Water
Systems (Grady and Casey, 2001), 1993-1998
USGS compiled and analyzed occurrence data for VOCs in finished drinking water in 12
Northeast and Mid-Atlantic states (Connecticut, Delaware, Maine, Maryland, Massachusetts,
New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Virginia).
State agencies supplied USGS with VOC data collected during 1993 through 1998 for 20 percent
of the CWSs in the 12-state area, which were chosen to be representative in terms of geography,
water source, and system size. The 1,2,3-trichloropropane analysis included 1,665 CWSs in all
12 states. 1,2,3-Trichloropropane was detected in 47 of 12,711 (0.37 percent of) samples.
Detected concentrations ranged from 0.5 |ig/L to 4.5 |ig/L (Grady and Casey, 2001).
Water Quality in Public-Supply Wells (Toccalino et al., 2010), 1993-2007
To assess risks posed by contaminants in public-supply wells, water samples were
collected from source (untreated) groundwater from 932 public-supply wells located in parts of
40 NAWQA Study Units in 41 states (Toccalino et al., 2010). Each well was sampled once
between 1993 and 2007. The public wells sampled in this study represented 629 unique PWSs,
representing 0.5 percent of the approximately 140,000 groundwater-supplied PWSs, but nearly
25 percent of the population served by groundwater PWSs in the United States. The reporting
levels used for 1,2,3-trichloropropane in this study ranged from 0.06 |ig/L to 0.2 |ig/L. 1,2,3-
Trichloropropane was reported as detected in 10 (1.20 percent) of a total of 832 samples. All of
these reported detections exceeded the V2 HRL and HRL. Results from this study are presented in
Exhibit C-24 and Exhibit C-25.
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January 2021
Exhibit C-24: 1,2,3-Trichloropropane Data from Public-Supply Wells (Toccalino et
al., 2010) - Summary of Reported Concentrations
Source Water Type
Concentration Values
M9/L)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Groundwater Only
0.13
0.43
1.91
2.58
2.65
Source: Toccalino et al., 2010
Exhibit C-25: 1,2,3-Trichloropropane Data from Public-Supply Wells (Toccalino et
al., 2010) - Summary of Samples
Source Water Type
Number of
Samples
All Reported
Detections
Number
Percent
Groundwater Only
832
10
1.20%
Source: Toccalino et al., 2010
Note: Given that the HRL is so much lower than the reporting levels
used, there is a broad range of potential contaminant concentrations
that could be in exceedance of the HRL but unreported.
Water Quality in Domestic Wells (DeSimone, 2009), 1991-2004
Between 1991 and 2004, USGS assessed water quality from domestic wells across the
United States using NAWQA data (DeSimone, 2009). The program included the analysis of
major ions, trace elements, nutrients, radon, and organic compounds (pesticides and VOCs) at
approximately 2,100 domestic wells (private drinking water wells) across 48 states, covering 30
regional aquifers. In addition, USGS summarized data from wells sampled for NAWQA
agricultural land-use assessment studies to provide an indication of the potential effects of
agricultural land-use practices on the groundwater in the aquifers studied. Reporting thresholds
varied; the most common thresholds were between 0.08 [j,g/L and 0.2 |ig/L, 1,2,3-
Trichloropropane was reported as detected in 15 (0.66 percent) of the 2,269 samples from aquifer
and agricultural land-use studies.
Volatile Organic Compounds (VOCs) in Domestic Wells (Moran et al., 2002; Rowe et
al, 2007), 1986-1999 and 1996-2002
As part of the NAWQA program, USGS studied the occurrence of VOCs in groundwater
from untreated rural self-supplied domestic wells between 1986 and 1999 (Moran et al., 2002).
Drinking water from domestic wells are not subject to EPA drinking water regulations.
Reporting levels varied; results for most VOCs were reported at an assessment level of 0.2 [j,g/L
to allow for comparison of detection frequencies between different groups of analytes. 1,2,3-
Trichloropropane was detected at or above the assessment level in 10 of 1,615 samples (0.62
percent). The reported concentrations ranged from 0.2 [j,g/L to 2.1 (J,g/L, with a median of 0.4
[j,g/L (Moran et al., 2002).
USGS also published the findings of a national assessment of VOCs in domestic wells
between 1996 and 2002 (Rowe et al., 2007). In this study, samples were analyzed for 55 VOCs.
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1,2,3-Trichloropropane, analyzed at reporting levels ranging from 0.07 [j,g/L to 0.18 (J,g/L, was
found in two of 1,208 well samples analyzed for this chemical (0.17 percent). The concentrations
were not specified in this study.
Water Quality in Carbonate Aquifers (Lindsey et al., 2008), 1993-2005
As part of the NAWQA program, Lindsey et al. (2008) assessed the water quality in
carbonate aquifers, which account for 22 percent of the groundwater pumped by the nation's
PWSs. From 1993 to 2005, the study analyzed 1,042 wells and springs across 12 aquifer systems
and 20 states for major ions, radon, nutrients, pesticides, and VOCs. The study authors evaluated
occurrence of most VOCs at a uniform assessment level of 0.2 (J,g/L. 1,2,3-Trichloropropane was
not detected in any of 793 samples.
Volatile Organic Compounds in the Nation's Ground Water andDrinking-Water
Supply Wells (Zogorski et al., 2006), 1985-2002
Zogorski et al. (2006) discuss the major findings and conclusions of the national
assessment of 55 VOCs in groundwater. VOC data from 2,401 domestic wells and 1,096 public
wells were available from aquifer studies, shallow ground-water studies, and a national source-
water survey to characterize the occurrence of VOCs. One VOC analysis per well was included
in the assessment.
In samples from aquifer studies, 1,2,3-trichloropropane was detected at levels > 0.2 [j,g/L
in 17 (0.61 percent) of 2,765 samples. Among the 17 samples with reported detections, the
median concentration was 0.5 (J,g/L. In samples from domestic wells, 1,2,3-trichloropropane was
detected at levels > 0.2 [j,g/L in 9 (0.43 percent) of 2,092 samples, with a median detected
concentration of 0.38 |ig/L, In samples from public wells, 1,2,3-trichloropropane was detected at
levels > 0.2 [j,g/L in 8 (0.8 percent) of 997 samples. Among the 8 samples with reported
detections, the median concentration was 0.7 (J,g/L.
Additional Source Water and Drinking Water Studies
The New Jersey Department of Environmental Protection (NJDEP) shared sampling
results from the New Jersey SOC Waiver Program with EPA during the third Contaminant
Candidate List (CCL 3) contaminant nominations process (USEPA, 2009b). NJDEP detected
1,2,3-trichloropropane in excess of a New Jersey health-based drinking water guidance value of
0.005 |ig/L in 30 of 2,640 private wells, and in 11 of approximately 260 CWSs between 1999
and 2004.
C.4.3 Other Data
The Centers for Disease Control and Prevention (CDC) Fourth National Report on Human
Exposure to Environmental Chemicals, 2019 Updated Tables
Since 1999, the National Health and Nutrition Examination Survey (NHANES) has
examined the U.S. population annually and released the data in 2-year cycles. The survey is
based on a representative sample of the U.S. population based on age, gender, and race/ethnicity
(CDC, 2019). The Fourth National Report on Human Exposure to Environmental Chemicals was
published in 2009 (CDC, 2009). The exposure data tables have been updated several times since
the original publication, most recently in 2019 (CDC, 2019). The 2019 updated tables include
data on whole blood concentrations (ng/mL) for 1,2,3-trichloropropane. The most recent data are
from the 2015-2016 reporting period. With a sample size of 3,036, the 95th percentile whole
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EPA - OGWDW Final Regulatory Determination 4 Support Document - App C, 1,2,3-Trichloropropane
January 2021
blood concentration was below the limit of detection (LOD). The LOD was 0.04 ng/mL. Please
note that this value cannot be directly compared to the HRL because it represents a whole blood
concentration, not a drinking water concentration.
C.5 Analytical Methods
EPA has published six analytical methods that are available for the analysis of 1,2,3-
trichloropropane in drinking water:
• EPA Method 502.2, Revision 2.1, Volatile Organic Compounds in Water by Purge
and Trap Capillary Column Gas Chromatography with Photoionization and
Electrolytic Conductivity Detectors in Series. Mean recoveries in reagent water range
from 99 to 100%, with Relative Standard Deviations (RSDs) of 2.0 to 2.3% (USEPA,
1995a).
• EPA Method 504.1, Revision 1.1, 1,2-Dibromoethane (EDB), l,2-Dibromo-3-
Chloro-Propane (DBCP), and 1,2,3-Trichloropropane (123-TCP) in Water By
Microextraction and Gas Chromatography. Mean recoveries (matrices not specified)
range from 91.9 to 111.1%, with RSDs of 2.13 to 13.88% (USEPA, 1995b).
• EPA Method 524.2, Revision 4.1, Measurement of Purgeable Organic Compounds in
Water by Capillary Column Gas Chromatography/Mass Spectrometry. Mean
recoveries in reagent water range from 91 to 108%), with RSDs of 2.8 to 14.4%
(USEPA, 1995c).
• EPA Method 524.3, Version 1.0, Measurement of Purgeable Organic Compounds in
Water by Capillary Column Gas Chromatography/Mass Spectrometry. The Lowest
Concentration Minimum Reporting Level (LCMRL) generated by the laboratory that
developed the method is 0.16 |ig/L. Mean recoveries in fortified reagent water and
drinking water (from groundwater and surface water sources) range from 88.1 to
123%), with RSDs of 2.0 to 10%> using Full Scan mode (USEPA, 2009f).
• EPA Method 524.4. Measurement of Purgeable Organic Compounds in Water by
Gas Chromatography/Mass Spectrometry Using Nitrogen Purge Gas. The LCMRL
generated by the laboratory that developed the method is 0.42 |ig/L using Full Scan
mode. The LCMRL using Selected Ion Monitoring (SIM) mode is 0.033 |ig/L. Mean
recoveries in fortified reagent water, groundwater, and surface water range from 84.2
to 102%) with RSDs of 2.9 to 10%> using Full Scan mode (USEPA, 2013).
• EPA Method 551.1, Revision 1.0, Determination of Chlorinated Disinfection
Byproducts, Chlorinated Solvents, and Halogenated Pesticides/Herbicides in
Drinking Water by Liquid/Liquid Extraction and Gas Chromatography with Electron
Capture Detection. Mean recoveries in preserved fortified reagent water, preserved
fortified fulvic acid enriched reagent water, and preserved fortified groundwater
range from 88 to 103%, with RSDs of 0.62 to 3.92% (USEPA, 1995d).
Laboratories participating in UCMR 3 were required to use EPA Method 524.3 in SIM
Mode and, as noted in Section C.4.2, were required to report 1,2,3-trichloropropane values at or
above the EPA-defined MRL of 0.03 |ig/L (77 FR 26072; USEPA, 2012b). The MRL was set
based on the capability of multiple laboratories at the time.
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C.6 Treatment Technologies
EPA evaluates whether suitable treatment technologies are available prior to
promulgating a final National Primary Drinking Water Regulation (NPDWR).
EPA's Drinking Water Treatability Database (USEPA, 2020) summarizes available
technical literature on the efficacy of treatment technologies for a range of drinking water
contaminants. Technologies available to treat 1,2,3-trichloropropane in groundwater and soil
include granular activated carbon (GAC), dechlorination by hydrogen release compound
(HRC®), and reductive dechlorination by zero valent zinc. Processes tested at bench scale
include: ultraviolet radiation and chemical oxidation with potassium permanganate; chemical
oxidation with Fenton's reagent; advanced oxidation with ozone and hydrogen peroxide;
reduction using granular zero-valent zinc; and biodegradation under aerobic conditions using
genetically engineered strains of Rhodococcus. The exact percentage removal a water system
may achieve with a given technology will be dependent upon a variety of factors, including
source water quality and water system characteristics.
C.7 References
California Environmental Protection Agency (CalEPA). 2009. Public Health Goal for 1,2,3-
Trichloropropane in Drinking Water. Office of Environmental Health Hazard
Assessment, Pesticide and Environmental Toxicology Section. August 2009.
https://oehha.ca.gov/water/public-health-goal/final-public-health-goal-123-
trichloropropane-drinking-water.
Centers for Disease Control and Prevention (CDC). 2009. Fourth National Report on Human
Exposure to Environmental Chemicals, Department of Health and Human Services,
Centers for Disease Control and Prevention. Available on the Internet at:
https://www.cdc.gov/exposurereport/pdf/fourthreport.pdf.
CDC. 2019. Fourth National Report on Human Exposure to Environmental Chemicals, Updated
Tables, January 2019: Volume One. Department of Health and Human Services, Centers
for Disease Control and Prevention. Available on the Internet at:
http://www.cdc.gov/exposurereport/.
ChemlDPlus. 2018. Available on the Internet at: http://chem.sis.nlm.nih.gov/chemidplus/.
Accessed December 5, 2018.
Delzer, G.C. and T. Ivahnenko. 2003. Occurrence and Temporal Variability of Methyl tert-Butyl
Ether (MTBE) and Other Volatile Organic Compounds in Select Sources of Drinking
Water: Results of the Focused Survey. U.S. Geological Survey Water-Resources
Investigations Report 02-4084. 65 pp.
DeSimone, L.A. 2009. Quality of Water from Domestic Wells in Principal Aquifers of the United
States, 1991-2004. U.S. Geological Survey Scientific Investigations Report 2008-5227.
139 pp. Available on the Internet at: http://pubs.usgs.gov/sir/2008/5227/.
Grady, S.J. and G.D. Casey. 2001. Occurrence and Distribution of Methyl tert-Butyl Ether and
Other Volatile Organic Compounds in Drinking Water in the Northeast and Mid-Atlantic
Regions of the United States, 1993-98. U.S. Geological Survey Water-Resources
Investigations Report 00-4228. 128 pp. Available on the Internet at:
https://pubs.er.usgs.gov/publication/wri004228.
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Grady, S.J. 2002. A National Survey of Methyl tert-Butyl Ether and Other Volatile Organic
Compounds in Drinking-Water Sources: Results of the Random Survey. U.S. Geological
Survey Water-Resources Investigations Report 02-4079, 85 p. Available on the Internet
at: https://pubs.er.usgs.gov/publication/wri024079.
Hamilton, P. A., T.L. Miller, and D.N. Myers. 2004. Water Quality in the Nation's Streams and
Aquifers: Overview of Selected Findings, 1991-2001. USGS Circular 1265. Available on
the Internet at: http://water.usgs.gov/pubs/circ/2004/1265/pdf/circularl265.pdf.
Hardin, B.D.; G.P. Bond, M.R. Sikov, F.D. Andrew, R.P. Beliles, and R.N. Niemeier. 1981.
Testing of selected workplace chemicals for teratogenic potential. Scandinavian Journal
of Work, Environment and Health 7:66-75 (as cited in USEPA, 1989).
Hazardous Substances Data Bank (HSDB). 2016. Available on the Internet at:
http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen7HSDB. Last revision date: October 25,
2016.
Hopple, J.A., G.C. Delzer, and J.A. Kingsbury. 2009. Anthropogenic Organic Compounds in
Source Water of Selected Community Water Systems that Use Ground Water, 2002-05.
U.S. Geological Survey Scientific Investigations Report 2009-5200. 74 pp. Available on
the Internet at: http://pubs.usgs.gov/sir/2009/5200/pdf/sir2009-5200.pdf.
Ivahnenko, T., S.J. Grady, and G.C. Delzer. 2001. Design of a National Survey of Methyl tert-
Butyl Ether and Other Volatile Organic Compounds in Drinking-Water Sources. U.S.
Geological Survey Open-File Report 01-271. 42 pp. Available on the Internet at:
https://pubs.er.usgs.gov/publication/ofr01271.
Johannsen, F.R., G.J. Levinskas, G.M. Rusch, et al. 1988. Evaluation of the subchronic and
reproductive effects of a series of chlorinated propanes in the rat. I. Toxicity of 1,2,3-
trichloropropane. J Toxicol Environ Health 25:299-315 (as cited in USEPA, 1989;
USEPA, 2009a).
Kingsbury, J.A., G.C. Delzer, and J.A. Hopple. 2008. Anthropogenic Organic Compounds in
Source Water of Nine Community Water Systems that Withdraw from Streams, 2002-05.
U.S. Geological Survey Scientific Investigations Report 2008-5208. 66 pp. Available on
the Internet at: http://pubs.usgs.gov/sir/2008/5208/pdf/sir2008-5208.pdf.
Lag, M.L.; E.J. Soderlund, J.G. Omichinski, et al. 1991. Effect of bromine and chlorine
positioning in the induction of renal and testicular toxicity by halogenated propanes.
Chem Res Toxicol 4: 528-534 (as cited in USEPA, 2009a).
Leahy, P.P. and T.H. Thompson. 1994. Overview of the National Water-Quality Assessment
Program. U.S. Geological Survey Open-File Report 94-70. 4 pp. Available on the
Internet at: http://water.usgs.gov/nawqa/NAWOA.OFR94-7Q.html.
Lindsey, B.D., M.P. Berndt, B.G. Katz, A.F. Ardis, and K.A. Skach. 2008. Factors Affecting
Water Quality in Selected Carbonate Aquifers in the United States, 1993-2005. U.S.
Geological Survey Scientific Investigations Report 2008-5240. Available on the Internet
at: http://pubs.usgs.gov/sir/2008/524Q/.
Lopes, T.J. and S.G. Dionne. 1998. A Review of Semivolatile and Volatile Organic Compounds
in Highway Runoff and Urban Stormwater. U.S. Geological Survey Open-File Report 98-
409. 67 pp. Available on the Internet at: http://pubs.usgs.gov/of/1998/ofr98-409/.
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Merrick, B.A. M. Robinson, and L.W. Condie. 1991. Cardiopathic effect of 1,2,3-
trichloropropane after subacute and subchronic exposure in rats. JAppl Toxicol 11:179-
187 (as cited in USEPA, 2009a).
Moran, M.J., W.W. Lapham, B.L. Rowe, and J.S. Zogorski. 2002. Occurrence and Status of
Volatile Organic Compounds in Ground Water from Rural, Untreated, Self-Supplied
Domestic Wells in the United States, 1986-1999. U.S. Geological Survey Water-
Resources Investigations Report 02-4085. 51 pp.
National Research Council (NRC). 2002. Opportunities to Improve the U.S. Geological Survey
National Water Quality Assessment Program. Washington, D.C.: National Academy
Press. Available on the Internet at: https://www.nap.edu/read/10267/chapter/!.
NRC. 2012. Preparing for the Third Decade of the National Water-Quality Assessment
Program. Washington, D.C.: National Academies Press.
National Toxicology Program (NTP). 1983a. National Toxicology Program. Final Report: 120-
day toxicity gavage study of 1, 2, 3-Trichloropropane in Fischer 344 rats. Vienna, VA:
Hazelton Laboratories America, Inc. June 16 (as cited in USEPA, 1989).
NTP. 1983b. National Toxicology Program. Final Report: 120-day gavage toxicity study in
B6C3F1 mice. 1, 2, 3-Trichloropropane. Vienna, VA: Hazelton Laboratories America,
Inc. April 29 (as cited in USEPA, 1989).
NTP. 1990. 1,2,3-Trichloropropane reproduction and fertility assessment in Swiss CD-I mice
when administered via gavage - final report. Public Health Services, U.S. Department of
Health and Human Services (NTIS/PB91-129676; NTP-90-209) (as cited in USEPA,
2009a).
NTP. 1993. Toxicology and carcinogenesis studies of 1,2,3-trichloropropane (CAS No. 96-18-4)
in F344/N rats and B6C3F1 mice (gavage studies). Research Triangle Park, NC, US
Department of Health and Human Services, National Toxicology Program, pp. 1-345.
NTP TR 384, December 1993 (as cited in CalEPA, 2009; USEPA, 2009a).
Rowe, B.L., P.L Toccalino, M.J. Moran, J.S. Zogorski, and C.V. Price. 2007. Occurrence and
Potential Human-Health Relevance of Volatile Organic Compounds in Drinking Water
from Domestic Wells in the United States. Environmental Health Perspectives 115(11):
1539-46.
Rowe, G.L., K. Belitz, H.I. Essaid, R.J. Gilliom, P A. Hamilton, A.B. Hoos, D.D. Lynch, M.D.
Munn, and D.W. Wolock. 2010. Design of Cycle 3 of the National Water-Quality
Assessment Program, 2013-2023: Part 1: Framework of Water-Quality Issues and
Potential Approaches. U.S. Geological Survey Open-File Report 2009-1296.
https://pubs.usgs.gov/of/2009/1296/.
Rowe, G.L., K. Belitz, C.R. Demas, H.I. Essaid, R.J. Gilliom, P A. Hamilton, A.B. Hoos, C.J.
Lee, M.D. Munn, and D.W. Wolock. 2013. Design of Cycle 3 of the National Water-
Quality Assessment Program, 2013-23: Part 2: Science Plan for Improved Water-Quality
Information and Management. U.S. Geological Survey. Open-File Report 2013-1160.
https://pubs.er.usgs.gov/publication/ofr20131160.
Silverman, L., H.F. Schulte, and M.W. First. 1946. Further Studies on Sensory Response to
Certain Industrial Solvent Vapors. JIndHyg Toxicol 28:262-266 (as cited in USEPA,
2009a).
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Speth, T. and R Miltner. 1990. Technical Note: GAC Adsorption Capacities for SOCs. Journal
of the American Water Works Association. 82(2):72.
Squillace, P.J., M.J. Moran, WW. Lapham, C.V. Price, R.M. Clawges, and J.S. Zogorski. 1999.
Volatile Organic Compounds in Untreated Ambient Groundwater of the United States,
1985-1995. Environmental Science and Technology 33(23):4176-4187. Available on the
Internet at: https://pubs.er.usgs.gov/publication/70021047.
Toccalino, P.L., J.E. Norman, and K.J. Hitt. 2010. Quality of Source Water from Public-supply
Wells in the United States, 1993-2007. U.S. Geological Survey Scientific Investigations
Report 2010-5024. 206 pp. Available on the Internet at:
http://pubs.usgs.gov/sir/2010/5Q24/.
U.S. Environmental Protection Agency (USEPA). 1989. 1,2,3-TRICHLOROPROPANE
Drinking Water Health Advisory, prepared by the Office of Water, PB91-160697.
USEPA. 1995a. Method 502.2. Volatile Organic Compounds in Water by Purge and Trap
Capillary Column Gas Chromatography with Photoionization and Electrolytic
Conductivity Detectors in Series. Revision 2.1. National Exposure Research Laboratory,
Office of Research and Development. EPA 600-4-88-039.
USEPA. 1995b. Method 504.1. 1,2-Dibromoethane (EDB), l,2-Dibromo-3-Chloro-Propane
(DBCP), and 1,2,3-Trichloropropane (123-TCP) in Water By Microextraction and Gas
Chromatography. Revision 1.1. National Exposure Research Laboratory, Office of
Research and Development. EPA 600-R-95-131.
USEPA. 1995c. Method 524.2. Measurement of Purgeable Organic Compounds in Water by
Capillary Column Gas Chromatography/Mass Spectrometry. Revision 4.1. National
Exposure Research Laboratory, Office of Research and Development. EPA 600-4-88-
039.
USEPA. 1995d. Method 551.1. Determination of Chlorinated Disinfection Byproducts,
Chlorinated Solvents, and Halogenated Pesticides/Herbicides in Drinking Water by
Liquid/Liquid Extraction and Gas Chromatography with Electron Capture Detection.
Revision 1.0. National Exposure Research Laboratory, Office of Research and
Development. EPA 600-R-95-131.
USEPA. 2001a. Occurrence of Unregulated Contaminants in Public Water Systems: An Initial
Assessment. Office of Water. EPA 815-P-00-001.
USEPA. 2001b. UCM - State Rounds 1 and 2 (1988 - 1997) Occurrence Data. Available on the
Internet at: https://www.epa.gov/dwucmr/occurrence-data-unregulated-contaminant-
monitoring-rule# 12.
USEPA. 2003. Occurrence Estimation Methodology and Occurrence Findings for Six-Year
Review of National Primary Drinking Water Regulations. Office of Water. EPA 815-R-
03-006.
USEPA. 2005a. Guidelines for carcinogen risk assessment. Risk Assessment Forum,
Washington, DC. EPA/630/P-03/001B.
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USEPA. 2005b. Supplemental guidance for assessing susceptibility from early-life exposure to
carcinogens. U.S. Environmental Protection Agency Risk
http://www.epa.gov/cancerguidelines/guidelines-carcinogen-supplement.htm.
Assessment Forum. Washington, DC. EPA/630/R-03/003F.
USEPA. 2008a. Using the 2006 Inventory Update Reporting (IUR) Public Data: Background
Document. Office of Pollution Prevention and Toxics. December. Available on the
Internet at:
https://www.epa.gov/sites/production/files/documents/iurdbbackground O.pdf.
USEPA. 2008b. The Analysis of Occurrence Data from the Unregulated Contaminant
Monitoring (UCM) Program and National Inorganics and Radionuclides Survey (NIRS)
in Support of Regulatory Determinations for the Second Drinking Water Contaminant
Candidate List. EPA 815-R-08-014.
USEPA. 2009a. Toxicological review of 1,2,3-trichloropropane in support of summary
information on the Integrated Risk Information System (IRIS). Washington, DC: U.S.
Environmental Protection Agency. EPA/635/R-O8/01 OF.
https://cfpub.epa.gov/ncea/iris/iris documents/documents/toxreviews/0200tr.pdf.
USEPA. 2009b. Summary of Nominations for the Third Contaminant Candidate List. EPA 815-
R-09-011.
USEPA. 2009c. The Analysis of Regulated Contaminant Occurrence Data from Public Water
Systems in Support of the Second Six-Year Review of National Primary Drinking Water
Regulations. EPA-815-B-09-006. October 2009.
USEPA. 2009d. Community Water System Survey 2006 Volume I: Overview. EPA 815-R-09-
001. Available on the Internet at:
https://nepis. epa.gov/Exe/ZyPDF. cgi?Dockev=P 1009JJI.txt.
USEPA. 2009e. Community Water System Survey 2006 Volume II: Detailed Tables and Survey
Methodology. EPA 815-R-09-002. Available on the Internet at:
https://nepis. epa.gov/Exe/ZyPDF. cgi?Dockev=P 1009USA.txt.
USEPA. 2009f. Method 524.3. Measurement of Purgeable Organic Compounds in Water by
Capillary Column Gas Chromatography/Mass Spectrometry. Version 1.0. Technical
Support Center, Office of Ground Water and Drinking Water. EPA 815-B-09-009.
USEPA. 2011. Exposure Factors Handbook: 2011 Edition (Final). EPA/600/R-09/052F.
September. Available at: https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=236252.
USEPA. 2012a. Estimation Program Interface (EPI Suite™) Program Modification & New
Features in v4.11 (November 2012). Available at:
https://19ianuarv2017snapshot.epa.gov/tsca-screening-tools/estimation-program-
interface-epi-suite-tm-program-modifications-new-features .html.
USEPA. 2012b. Revisions to the Unregulated Contaminant Monitoring Regulation (UCMR 3)
for Public Water Systems. Federal Register 77(85): 26072, May 2, 2012.
USEPA. 2013. Method 524.4. Measurement of Purgeable Organic Compounds in Water by Gas
Chromatography/Mass Spectrometry Using Nitrogen Purge Gas. Technical Support
Center, Office of Ground Water and Drinking Water. EPA 815-R-13-002.
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January 2021
USEPA. 2014. Chemical Data Reporting. Fact Sheet: Basic Information. June. EPA Publication
740-K-13-001.
USEPA. 2016. The Analysis of Regulated Contaminant Occurrence Data from Public Water
Systems in Support of the Third Six-Year Review of National Primary Drinking Water
Regulations: Chemical Phase Rules and Radionuclides Rules. EPA 810-R-16-014.
December 2016.
USEPA. 2017a. TRI Explorer: Trends. Available on the Internet at:
https://enviro.epa.gov/triexplorer/tri release.trends. Accessed November 2017.
USEPA. 2017b. Third Unregulated Contaminant Monitoring Rule Dataset. Available on the
Internet at: https://www.epa.gov/dwucmr/occurrence-data-unregulated-contaminant-
monitoring-rule#3. Accessed January 2017.
USEPA. 2018. CDR Reporting Requirements. Available on the Internet at:
https://www.epa.gov/chemical-data-reporting/how-report-under-chemical-data-reporting.
Accessed December 2018.
USEPA. 2019a. CompTox Chemicals Dashboard, Searched by DSSTox Substance Id =
DTXSID4020533. Available on the Internet at:
https://comptox.epa. gov/dashboard/dsstoxdb/results?search=DTXSID4020533.
USEPA. 2019b. The Toxics Release Inventory (TRI) and Factors to Consider When Using TRI
Data. Available on the Internet at: https://www.epa.gov/toxics-release-inventory-tri-
program/factors-consider-when-using-toxics-release-inventory-data.
USEPA. 2019c. Occurrence Data from the Third Unregulated Contaminant Monitoring Rule
(UCMR 3). EPA 815-R-19-007.
USEPA. 2020. Drinking Water Treatability Database.
https://iaspub.epa.gov/tdb/pages/general/home.do. Last updated March 2020.
United States Geological Survey (USGS). 2016. National Water Information System (NWIS)
Water-Quality Web Services. Available on the Internet at:
https://waterdata.usgs.gov/nwis. Last modified December 2016.
Villeneuve, D.C., I. Chu, V.E. Secours, et al. 1985. Results of a 90-day toxicity study on 1,2,3-
and 1,1,2-trichloropropane administered via the drinking water. Sci Total Environ
47:421-426 (as cited in USEPA, 2009a).
Water Quality Portal (WQP). 2017. Water Quality Portal Data Warehouse. Available on the
Internet at: https://www.waterqualitvdata.us/. Data Warehouse consulted December 2017.
WQP. 2018. Water Quality Portal Data Warehouse. Available on the Internet at:
https://www.waterqualitvdata.us/. Data Warehouse consulted September 2018.
World Health Organization (WHO). 2003. Concise International Chemical Assessment
Document 56. 1,2,3-Trichloropropane. Geneva, Switzerland.
http://www.who.int/ipcs/publications/cicad/en/cicad56.pdf.
Zogorski, J.S., J.M. Carter, T. Ivahnenko, W.W. Lapham, M.J. Moran, B.L. Rowe, P.J.
Squillace, and P.L. Toccalino. 2006. Volatile Organic Compounds in the Nation's
Ground Water andDrinking-Water Supply Wells. USGS Circular 1292. Available on the
Internet at: http://pubs.usgs.gov/circ/circl292/pdf/circularl292.pdf.
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Appendix D:
PFOS and PFOA Annotated Bibliography
An appendix from:
Final Regulatory Determination 4 Support Document
EPA Report 815-R-21-001
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Contents
Contents D-2
Exhibits D-3
Abbreviations D-4
D. 1 Specific Aims of the Updated Literature Search for PFOA and PFOS D-5
I).2 Database Searches D-5
D.3 Screening for Inclusion and Exclusion D-6
D.4 PFOA and PFOS Update - Search Strings D-l 1
D.5 Bibliography of PECO Relevant Studies D-13
D.5.1 Human D-13
D.5.2 Animal (Mammalian Model) D-52
D.5.3 Human and Animal (Mammalian Model) D-62
D.5.4 PBPK Models D-63
D.5.5 Human and PBPK Model D-64
D.5.6 Animal and PBPK Model D-65
D.5.7 Unclear D-65
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Exhibits
Exhibit D-l: PECO Statement for the PFOA and PFOS Updated Literature Search D-7
Exhibit D-2: Supplemental Tags for the PFOA and PFOS Updated Literature Search D-8
Exhibit D-3: Literature Flow Diagram for the PFOA and PFOS Updated Literature Search.. D-10
Exhibit D-4: Search Strings D-l 1
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Abbreviations
ADME
Absorption, Distribution, Metabolism, and Excretion
CAS
Chemical Abstracts Service
EPA
Environmental Protection Agency
HERO
Health and Environmental Research Online Database
HESD
Health Effect Support Document
HISA
Highly Influential Science Assessments
ISI
Influential Scientific Information
NTP
National Toxicology Program
PBPK
Phy si ol ogi cally-b ased Pharmacokineti c
PECO
Populations, Exposure, Comparators, and Outcomes
PFOA
Perfluorooctanoic Acid
PFOS
Perfluorooctanesulfonic Acid
RfD
Reference Dose
SWIFT
Sciome Workbench for Interactive computer-Facilitated Text-mining
TSCATS
Toxic Substances Control Act Test Submissions
WOS
Web of Science
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Appendix D: PFOS and PFOA Annotated Bibliography
D.l Specific Aims of the Updated Literature Search for PFOA and PFOS
In 2016, EPA published health assessments (health effects support documents or HESDs)
for perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) based on the
Agency's evaluation of the peer reviewed science available at that time. For specific details on
the potential for adverse health effects and approaches used to identify and evaluate information
on hazard and dose-response, please see the HESDs for PFOA and PFOS and the 2016 Health
Advisories for PFOA and PFOS. The lifetime HA of 0.07 |ig/L is used as the HRL for
Regulatory Determination 4.
The specific aims of the PFOA and PFOS updated literature search screening were to:
1.) Identify health effects information (epidemiological, toxicological studies and
physiologically-based pharmacokinetic (PBPK) models), published since the 2016
health effect support documents (HESDs) for PFOA and PFOS that could potentially
influence future PFOA or PFOS drinking water regulatory actions.
2.) Provide a bibliography of these relevant studies containing human, animal
(mammalian model), and PBPK data.
Additional analyses of the included studies are needed to confirm relevance, extract the
data to assess the weight of evidence, and identify critical studies in order to inform future
decision making. Following EPA's final positive regulatory determination for PFOA and PFOS,
the Agency will undertake the rulemaking process to establish a National Primary Drinking
Water Regulation for those contaminants. For that rulemaking effort, in addition to using the best
available science, the Safe Drinking Water Act (SDWA) requires the Agency seek
recommendations from the EPA Science Advisory Board and consider public comment on any
proposed rule. Therefore, EPA anticipates further scientific review of new science prior to
promulgation of any regulatory standard.
D.l Database Searches
Following EPA's 2013 Conflict of Interest Review Process for Contractor-Managed Peer
Reviews of EPA Highly Influential Science Assessments (HIS A) and Influential Scientific
Information (ISI) Documents, HESDs for PFOA and PFOS were released for public comment
and panel peer review in 2014. The current updated literature search focused on studies
published since 2013, under the assumption that any critical studies published previously would
have been considered in the public comment and external peer review processes used in
developing the HESDs. This updated literature search focused only on the chemical name with
no limitations on lines of evidence (i.e., human, animal, in vitro, in silico) or health outcomes.
The databases listed below were searched for literature containing the chemical search terms.
Full details of the search strategy for each database are presented in Section D.4.
• PubMed (National Library of Medicine)
• Web of Science (Thomson Reuters)
• ToxLine (National Library of Medicine; only searched for the 2013 - April 2019
literature search)
• TSCATS (only searched for the 2013 - April 2019 literature search)
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The database searches were conducted by an EPA information specialist on April 11,
2019 and September 3, 2020 and all records were stored in the Health and Environmental
Research Online (HERO) database. Since the April 2019 search, Toxline was incorporated into
PubMed. Because Toxline was defunct, TSCATS could not be searched after the April 2019
search. This was not considered to be an issue because prior to being taken down, the most
recent TSCATS reference in Toxline was from 2002. After deduplication in HERO, these studies
were imported into SWIFT Review software (https://www.sciome.com/swift-review/) to identify
those references most likely to be applicable to human health and ecotoxicological risk
assessment. In brief, SWIFT Review has pre-set literature search strategies ("filters") developed
and applied by information specialists to separate studies more likely to be useful for identifying
human health content from those that are less likely (e.g., those focused on analytical methods).
The filters function like a typical search strategy in which studies are tagged as belonging to a
certain filter if the terms in the filter literature search strategy appear in title, abstract, keyword,
or medical subject headings (MeSH) fields. The SWIFT Review filters applied to the PFOA and
PFOS literature search focused on lines of evidence: human studies, animal models for human
health, and in vitro studies. The details of the search strategies that underlie the filters are
available online (https://hawcprd.epa.gov/media/attachment/SWIFT-
Review Search Strategies.pdf). Studies not retrieved using these filters were not considered
further. Studies that included one or more of the search terms in the title, abstract, keyword, or
MeSH fields were exported as a RIS (Research Information System) file for screening in
DistillerSR, as described below. Application of the SWIFT evidence stream filters reduced the
number of studies for title and abstract screening from 3,382 to 1,976 studies for the April 2019
search, and from 1,153 to 868 studies for the September 2020 search.
Additionally, in 2020, the National Toxicology Program (NTP) website was searched for
PFOA and PFOS toxicity studies with final reports that could provide relevant health effects
information. Three reports were identified and included as relevant: (1) a 28-day PFOS study in
rats, (2) a 28-day PFOA study in rats, and (3) a two-year carcinogenicity study for PFOA in rats.
These final reports are included in this literature search because these data have undergone
standard NTP quality assurance/control processing, peer review, and are publicly available.
D.3 Screening for Inclusion and Exclusion
The goal of the PFOA and PFOS updated literature search was to identify health effects
studies that could influence the derivation of an oral reference dose (RfD) or cancer slope
published since the development of EPA's 2016 HESDs for PFOA and PFOS. The studies
identified were screened against the populations, exposure, comparators, and outcomes (PECO)
criteria described in the PECO statement (Exhibit D-l). The PECO statement was developed to
identify studies that could be relevant to the quantitative assessment for PFOA and PFOS for
Regulatory Determination 4. The studies screened by SWIFT Review as applicable to human
health were imported into a systematic review software package (Distiller SR, available at
https://www.evidencepartners.com/products/distillersr-svstematic-review-software) for this title
and abstract screening.
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Exhibit D-1: PECO Statement for the PFOA and PFOS Updated Literature Search
p
Human: Any population and lifestage (occupational or general population, including children
and other sensitive populations).
Animal: Nonhuman mammalian animal species (whole organism) of any lifestage (including
preconception, in utero, lactation, peripubertal, and adult stages).
In vitro/cell studies or in silico/modeling toxicity studies should be tagged as supplemental
E
Relevant forms:
PFOA (chemical abstracts service (CAS) number 335-67-1).
Other names: perfluorooctanoate, perfluorooctanoic acid, perfluoroctanoic acid,
2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctanoic acid, Pentadecafluoro-1-octanoic acid,
Pentadecafluoro-n-octanoic acid, Octanoic acid, pentadecafluoro-, Perfluorocaprylic acid,
Pentadecafluorooctanoic acid, perfluoroheptanecarboxylic acid
PFOS (CAS number 1763-23-1).
perfluorooctane sulfonate, perfluorooctanesulfonic acid, perfluorooctane sulfonic acid,
perfluorooctane sulphonate, perfluorooctane sulfonate, perfluorooctanyl sulfonate,
Heptadecafluorooctane-1-sulphonic, Heptadecafluoro-1-octanesulfonic acid,
1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-heptadecafluoro-1-octanesulfonic acid
Human: Any exposure to PFOA or PFOS via oral routes. Other exposure routes, including
inhalation, dermal or unknown/multiple routes, will be tracked during title and abstract
screening and tagged as "potentially relevant supplemental information."
Animal: Any exposure to PFOA or PFOS via oral routes. Other exposure routes, including
inhalation, dermal, injection, or unknown/multiple routes, will be tracked during title and
abstract screening and tagged as "potentially relevant supplemental information." Studies
involving exposures to mixtures will be included only if they include exposure to PFOA OR
PFOS alone.
C
Human: A comparison or referent population exposed to lower levels (or no
exposure/exposure below detection limits) of PFOA or PFOS, or exposure to PFOA or
PFOS for shorter periods of time. Case reports and case series will be tracked as "potentially
relevant supplemental information."
Animal: A concurrent control group exposed to vehicle-only treatment or untreated control.
O
All health outcomes (both cancer and noncancer).
PBPK
Models
Studies describing PBPK models will be included
The title and abstract of each study were independently screened by two screeners using
Distiller SR. The studies that met the PECO criteria were tagged as having relevant: human data,
animal data in a mammalian model, or a PBPK model. Studies may have received multiple tags
as appropriate. A study was included when it was unclear from the title and abstract whether it
met the PECO criteria. Studies that did not meet the PECO criteria, but could provide important
supporting information were categorized relative to the type of supporting information they
provided. These supplemental categories are outlined in Exhibit D-2.
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Exhibit D-2: Supplemental Tags for the PFOA and PFOS Updated Literature
Search
Category
Evidence
Mechanistic studies
Studies reporting measurements related to a health outcome that inform the
biological or chemical events associated with phenotypic effects, in both
mammalian and non-mammalian model systems, including in vitro, in vivo (by
various routes of exposure), ex vivo, and in silico studies. When possible,
mechanistic studies will be sub-tagged as pertinent to cancer, non-cancer, or
unclear/unknown.
Non-mammalian model
systems
Studies in non-mammalian model systems, e.g., fish, birds, C. elegans
ADME and toxicokinetic
Studies designed to capture information regarding absorption, distribution,
metabolism, and excretion, including toxicokinetic studies. Such information
may be helpful in updating or revising the parameters used in existing PBPK
models.
Acute/short-term duration
exposures
Animal studies of less than 28 days
Exposure characteristics
Exposure characteristic studies include data that are unrelated to toxicological
endpoints, but which provide information on exposure sources or
measurement properties of the environmental agent (e.g., demonstrate a
biomarker of exposure).
Susceptible populations
Studies that identify potentially susceptible subgroups; for example, studies
that focus on a specific demographic, lifestage, or genotype.
Mixture studies
Mixture studies that are not considered PECO-relevant because they do not
contain an exposure or treatment group assessing only the chemical of
interest.
Non-oral routes of
exposure
Studies not addressing routes of exposure that fall outside the PECO scope,
include inhalation and dermal exposure routes
Case studies or case
series
Case reports and case series will be tracked as potentially relevant
supplemental information.
Records with no original
data
Records that do not contain original data, such as other agency assessments,
informative scientific literature reviews, editorials or commentaries.
Conference abstracts
Records that do not contain sufficient documentation to support study
evaluation and data extraction.
Bioaccumulation in fish
Retained records relevant to other EPA projects mentioned in the PFAS
Action Plan
When two screeners did not agree on whether a study should be included, excluded or
tagged as supplemental, a conflict resolution discussion occurred with all four screeners. The
four screeners discussed the study and came to a consensus on the appropriate tag. A study
proceeded to full text review if it was unclear from the title and abstract whether the study was
relevant or how a study should be tagged. As depicted in Exhibit D-3, a total of 2,844 studies
were screened and 620 studies were tagged as either meeting the PECO criteria or needing
further review, 1559 studies were tagged as supplemental, and 665 were tagged as excluded for
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not meeting PECO criteria. The bibliography of the PECO relevant studies can be found in
Section D.5.
As stated above, the goal of this updated literature screen was to identify health effects
studies which could potentially influence future PFOA or PFOS drinking water regulatory
actions. The studies identified as containing human, animal or PBPK data are presented in
Section D.5. Additional analyses of the included studies is needed to confirm relevance with a
full text screening, extract the data to assess the weight of evidence, and identify critical studies
in order to inform future decision making. The 1559 studies tagged as supplemental were not
included in Section D.5 but may also be relevant. For example, 152 studies were tagged as
potentially containing toxicokinetic data which will be important to evaluate for future PFOA
and PFOS drinking water regulatory actions. All studies identified in the literature search,
including the supplemental studies, can be found on HERO:
https://hero.epa.gov/hero/index.cfm/proiect/page/proiect id/2608.
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Exhibit D-3: Literature Flow Diagram for the PFOA and PFOS Updated Literature
Search
DATABASE SEARCHES (From 2013 Through September 2020)
PubMed
(n = 3,002)
WOS
(n = 4,367)
ToxLine
(n = 60)
s
—\
TSCATS
o
ii
c
V
y
Duplicates removed
(n = 2,894)
Excluded by SWIFT electronic screen
{n = 1691)
TITLE AND ABSTRACT
Human
{n = 450)
Animal
(n = 125)
Human and
Animal
(n = 8)
Human and
PBPK
(n = 8)
Animal and
PBPK
(n = 1)
Search of National Toxicology Program
website for data tables
(3)
Animal
(n = 3)
Excluded {n =665)
Not relevant to PECO
Tagged as supplemental*
(n= 1559)
• Mechanistic
• Nonmammalian model
• ADME / Toxicokinetics
• Less than 28 days in mammalian model
• Animal studies with exposure route other
than oral
• Exposure characteristics
• Environmental fate/occurrence
• Mixture study
• Other reviews
• Bioaccumulation data in fish
*note that most supplemental studies had multiple
tags
INCLUDED
Studies considered relevant to PECO
{n = 620)
D-10
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EPA - OGWDW Final Regulatory Determination 4 Support Document - App D, Annotated Bibliography
January 2021
D.4 PFOA and PFOS Update - Search Strings
Exhibit D-4: Search Strings
Web of
Science
(WOS)
((TS="perfluorooctanoic acid" OR TS="perfluorooctane sulfonic acid")
AND PY=(2013-2019) OR (TS="2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-
pentadecafluoro-Octanoic acid" OR TS="2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-
pentadecafluorooctanoic acid" OR TS="3,3,4,4,5,5,6,6,6-nonafluoro-2-
oxo-Hexanoyl fluoride" OR TS="3,3,4,4,5,5,6,6,6-nonafluoro-2-
oxohexanoyl fluoride" OR TS="Hexanoyl fluoride, 3,3,4,4,5,5,6,6,6-
nonafluoro-2-oxo-" OR TS="Octanoic acid, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-
pentadecafluoro-" OR TS="Pentadecafluoro-1-octanoic acid" OR
TS="Pentadecafluoro-n-octanoic acid" OR
TS="Pentadecafluorooctanoic acid" OR TS="Perfluorocaprylic acid" OR
TS="Perfluoroctanoic acid" OR TS="Perfluoroheptanecarboxylic acid"
OR TS="perfluorooctanyl sulfonate" OR TS="Perfluorooctanoic acid"
OR TS="Octanoic acid, pentadecafluoro-" OR TS="Perfluorooctanoate"
OR TS="perfluorooctane sulfonate" OR TS="A 5717" OR TS="EF 201"
OR TS="Eftop EF 201" OR TS="Perfluoro-1-heptanecarboxylic acid"
OR TS="1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-Heptadecafluoro-1-
octanesulfonic acid" OR TS="1-Octanesulfonic acid,
1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-heptadecafluoro-" OR TS="1-
Perfluorooctanesulfonic acid" OR TS="EF 101" OR TS="Eftop EF 101"
OR TS="Heptadecafluoro-1-octanesulfonic acid" OR
TS="Heptadecafluorooctane-1-sulphonic acid" OR TS="Perfluorooctane
sulfonate" OR TS="perfluorooctane sulfonate" OR TS="Perfluorooctane
sulfonic acid" OR TS="Perfluorooctanesulfonic acid" OR
TS="Perfluorooctylsulfonic acid" OR TS="perfluorooctane sulphonate"
OR TS="perfluorooctane sulfonate" OR TS="1-Octanesulfonic acid,
heptadecafluoro-"OR TS="Heptadecafluorooctanesulfonic acid" OR
TS="Perfluoro-n-octanesulfonic acid" OR TS="Perfluorooctane
Sulphonic Acid" OR TS="Perfluorooctanesulfonate" OR
TS="Perfluorooctylsulfonate" OR ((TS="PFOA" OR TS="PFOS") AND
(TS="fluorocarbon*" OR TS="fluorotelomer*" OR TS="polyfluoro*" OR
TS="perfluoro-*" OR TS="perfluoroa*" OR TS="perfluorob*" OR
TS="perfluoroc*" OR TS="perfluorod*" OR TS="perfluoroe*" OR
TS="perfluoroh*" OR TS="perfluoron*" OR TS="perfluoroo*" OR
TS="perfluorop*" OR TS="perfluoros*" OR TS= "perfluorou*" OR
TS="perfluorinated" OR TS="fluorinated" OR TS="PFAS"))) AND
PY= (2013-2019))
4/10/2019:
3,081
results
D-ll
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EPA - OGWDW Final Regulatory Determination 4 Support Document - App D, Annotated Bibliography January 2021
PubMed
(335-67-1 [rn] OR 1763-23-1 [rn] OR 45298-90-6[rn] OR
"perfluorooctanoic acid"[nm] OR "perfluorooctane sulfonic acid"[nm])
AND (2013/01/01:3000[pdat] OR 2013/01/01:3000[mhda] OR
2013/01/01:3000[edat] OR 2013/01/01:3000[crdt]) OR
(("2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluoro-Octanoic acid"[tw] OR
"2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctanoic acid"[tw] OR
"3,3,4,4,5,5,6,6,6-nonafluoro-2-oxo-Hexanoyl fluoride"[tw] OR
"3,3,4,4,5,5,6,6,6-nonafluoro-2-oxohexanoyl fluoride"[tw] OR "Hexanoyl
fluoride, 3,3,4,4,5,5,6,6,6-nonafluoro-2-oxo-"[tw] OR "Octanoic acid,
2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluoro-"[tw] OR
"Pentadecafluoro-1-octanoic acid"[tw] OR "Pentadecafluoro-n-octanoic
acid"[tw] OR "Pentadecafluorooctanoic acid"[tw] OR "Perfluorocaprylic
acid"[tw] OR "Perfluoroctanoic acid"[tw] OR "Perfluoroheptanecarboxylic
acid"[tw] OR "perfluorooctanyl sulfonate"[tw] OR "Perfluorooctanoic
acid"[tw] OR "Octanoic acid, pentadecafluoro-"[tw] OR
"Perfluorooctanoate"[tw] OR "perfluorooctane sulfonate"[tw] OR "A
5717"[tw] OR "EF 201 "[tw] OR "Eftop EF 201 "[tw] OR "Perfluoro-1-
heptanecarboxylic acid"[tw] OR "1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-
Heptadecafluoro-1-octanesulfonic acid"[tw] OR "1-Octanesulfonic acid,
1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-heptadecafluoro-"[tw] OR "1-
Perfluorooctanesulfonic acid"[tw] OR "EF 101"[tw] OR "Eftop EF
101"[tw] OR "Heptadecafluoro-1-octanesulfonic acid"[tw] OR
"Heptadecafluorooctane-1-sulphonic acid"[tw] OR "Perfluorooctane
sulfonate"[tw] OR "perfluorooctane sulfonate"[tw] OR "Perfluorooctane
sulfonic acid"[tw] OR "Perfluorooctanesulfonic acid"[tw] OR
"Perfluorooctylsulfonic acid"[tw] OR "perfluorooctane sulphonate" [tw]
OR "perfluorooctane sulfonate"[tw] OR "1-Octanesulfonic acid,
heptadecafluoro-"[tw] OR "Heptadecafluorooctanesulfonic acid"[tw] OR
"Perfluoro-n-octanesulfonic acid"[tw] OR "Perfluorooctane Sulphonic
Acid"[tw] OR "Perfluorooctanesulfonate"[tw] OR
"Perfluorooctylsulfonate"[tw] OR (("PFOA"[tw] OR "PFOS"[tw]) AND
(fluorocarbon*[tw] OR fluorotelomer*[tw] OR polyfluoro*[tw] OR
perfluoro-*[tw] OR perfluoroa*[tw] OR perfluorob*[tw] OR perfluoroc*[tw]
OR perfluorod*[tw] OR perfluoroe*[tw] OR perfluoroh*[tw] OR
perfluoron*[tw] OR perfluoroo*[tw] OR perfluorop*[tw] OR perfluoros*[tw]
OR perfluorou*[tw] OR perfluorinated[tw] OR fluorinated[tw] OR
PFAS[tw]))) AND (2013/01/01:3000[pdat] OR 2013/01/01:3000[mhda]
OR 2013/01/01:3000[edat] OR 2013/01/01:3000[crdt]))
4/10/2019:
2,191
results
Toxline
@AND+@OR+("perfluorooctane
sulfonate"+"pfos"+"perfluorooctanesulfonic acid"+"perfluorooctane
sulfonic acid"+"perfluorooctane sulphonate"+"perfluorooctane
sulfonate"+"perfluorooctanyl sulfonate"+"Heptadecafluorooctane-1-
sulphonic"+"Heptadecafluoro-1-octanesulfonic
acid"+"1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-heptadecafluoro-1-
octanesulfonic acid"+"perfluorooctanoate"+"perfluorooctanoic
acid"+"perfluoroctanoic acid"+"pfoa"+"2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-
pentadecafluorooctanoic acid"+"Pentadecafluoro-1 -octanoic
acid"+"Pentadecafluoro-n-octanoic acid"+"Octanoic acid,
pentadecafluoro-"+"Perfluorocaprylic acid"+"Pentadecafluorooctanoic
acid"+"perfluoroheptanecarboxylic acid"+@TERM+@rn+335-67-
1 +@TERM+@rn+1763-23-1 +@TERM+@rn+45298-90-
6)+@NOT+@org+pubmed+@AND+@RANGE+yr+2013+2019
4/11/2019:
60 results
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EPA - OGWDW Final Regulatory Determination 4 Support Document - App D, Annotated Bibliography
January 2021
Toxic
Substances
Control Act
Test
Submissions
(TSCATS)
@AND+@OR+@rn+"335-67-
1"+@AND+@org+TSCATS+@NOT+@org+pubmed
@AND+@OR+@rn+"1763-23-
1"+@AND+@org+TSCATS+@NOT+@org+pubmed
4/11/2019:
0 results
Total number of references from all databases for 2013-2019
3,382
results
D.5 Bibliography of PECO Relevant Studies
D.5.1 Human
[No Author ] (2000). SUPPORT: AN EPIDEMIOLOGIC INVESTIGATION OF PLASMA
CHOLECYSTOKININ AND HEPATIC FUNCTION IN PERFLUOROOCTANOIC
ACID PRODUCTION WORKERS, WITH COVER LETTER DATED 012800
#journal#, #volume#(#issue#), #Pages#
[No Author ] (2000). SUPPORT: FLUOROCHEMICAL EXPOSURE ASSESSMENT OF
DECATUR CHEMICAL and FILM PLANT EMPLOYEES, WITH ATTACHMENTS
and COVER LETTER DATED 042500 #journal#, #volume#(#issue#), #Pages#
[No Author.] (2013). Prenatal exposure to perfluorooctanoic acid and risk of obesity at the age of
20. Environnement, Risques & Sante, 12(#issue#), 21
Abraham, K., H. Mielke, H. Fromme, W. Volkel, J. Menzel, M. Peiser, F. Zepp, S.N. Willich, C.
Weikert (2020). Internal exposure to perfluoroalkyl substances (PFASs) and biological
markers in 101 healthy 1-year-old children: associations between levels of
perfluorooctanoic acid (PFOA) and vaccine response. Archives of Toxicology,
#volume#(#issue#), #Pages#
Agier, L., X. Basagana, L. Maitre, B. Granum, P.K. Bird, M. Casas, B. Oftedal, J. Wright, S.
Andrusaityte, M. de Castro, E. Cequier, L. Chatzi, D. Donaire-Gonzalez, R.
Grazuleviciene, L.S. Haug, A.K. Sakhi, V. Leventakou, R. Mceachan, M.
Nieuwenhuijsen, I. Petraviciene, O. Robinson, T. Roumeliotaki, J. Sunyer, I. Tamayo-
Uria, C. Thomsen, J. Urquiza, A. Valentin, R. Slama, M. Vrijheid, V. Siroux (2019).
Early-life exposome and lung function in children in Europe: an analysis of data from the
longitudinal, population-based HELIX cohort. #journal#, 3(#issue#), e81
Aimuzi, R., K. Luo, Q. Chen, H. Wang, L. Feng, F. Ouyang, J. Zhang (2019). Perfluoroalkyl and
polyfluoroalkyl substances and fetal thyroid hormone levels in umbilical cord blood
among newborns by prelabor caesarean delivery. Environment International,
130(#issue#), 104929
Aimuzi, R., K. Luo, R. Huang, X. Huo, M. Nian, F. Ouyang, Y. Du, L. Feng, W. Wang, J.
Zhang, Shanghai Birth Cohort Study (2020). Perfluoroalkyl and polyfluroalkyl
substances and maternal thyroid hormones in early pregnancy Environmental Pollution,
264(#issue#), 114557
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January 2021
Ait Bamai, Y., H. Goudarzi, A. Araki, E. Okada, I. Kashino, C. Miyashita, R. Kishi (2020).
Effect of prenatal exposure to per- and polyfluoroalkyl substances on childhood allergies
and common infectious diseases in children up to age 7 years: The Hokkaido study on
environment and children's health. Environment International, #volume#(#issue#),
#Pages#
Alderete, T.L., R. Jin, D.I. Walker, D. Valvi, Z. Chen, D.P. Jones, C. Peng, F.D. Gilliland, K.
Berhane, D.V. Conti, M.I. Goran, L. Chatzi (2019). Perfluoroalkyl substances,
metabolomic profiling, and alterations in glucose homeostasis among overweight and
obese Hispanic children: A proof-of-concept analysis. Environment International,
126(#issue#), 445
Alkhalawi, E., M. Kasper-Sonnenberg, M. Wilhelm, W. Volkel, J. Wittsiepe (2016).
Perfluoroalkyl acids (PFAAs) and anthropometric measures in the first year of life:
Results from the Duisburg Birth Cohort. Journal of Toxicology and Environmental
Health, Part A: Current Issues, 79(#issue#), 1041
Ammitzb0ll, C., L. Bornsen, E.R. Petersen, A.B. Oturai, H.B. S0ndergaard, P. Grandjean, F.
Sellebjerg (2019). Perfluorinated substances, risk factors for multiple sclerosis and
cellular immune activation. Journal of Neuroimmunology, 330(#issue#), 90
Andersen, C.S., C. Fei, M. Gamborg, E.A. Nohr, T.I. S0rensen, J. Olsen (2013). Prenatal
exposures to perfluorinated chemicals and anthropometry at 7 years of age. American
Journal of Epidemiology, 178(#issue#), 921
Andersson, E.M., K. Scott, Y. Xu, Y. Li, D.S. Olsson, T. Fletcher, K. Jakobsson (2019). High
exposure to perfluorinated compounds in drinking water and thyroid disease. A cohort
study from Ronneby, Sweden. Environmental Research, 176(#issue#), 108540
Arbuckle, T., C. Kubwabo, M. Walker, K. Davis, K. Lalonde, I. Kosarac, S. Wen, D.L. Arnold
(2013). Umbilical cord blood levels of perfluoroalkyl acids and polybrominated flame
retardants. International Journal of Hygiene and Environmental Health, 216(#issue#), 184
Arbuckle, T.E., S. Macpherson, W.G. Foster, S. Sathyanarayana, M. Fisher, P. Monnier, B.
Lanphear, G. Muckle, W.D. Fraser (2020). Prenatal Perfluoroalkyl Substances and
Newborn Anogenital Distance in a Canadian Cohort. Reproductive Toxicology,
94(#issue#), 31
Arrebola, J.P., J.J. Ramos, M. Bartolome, M. Esteban, O. Huetos, A.I. Canas, A. Lopez-Herranz,
E. Calvo, B. Perez-Gomez, A. Castano,BIOAMBIENT.ES (2019). Associations of
multiple exposures to persistent toxic substances with the risk of hyperuricemia and
subclinical uric acid levels in BIOAMBIENT.ES study. Environment International,
123(#issue#), 512
Ashley-Martin, J., L. Dodds, T.E. Arbuckle, A.S. Morisset, M. Fisher, M.F. Bouchard, G.D.
Shapiro, A.S. Ettinger, P. Monnier, R. Dallaire, S. Taback, W. Fraser (2016). Maternal
and Neonatal Levels of Perfluoroalkyl Substances in Relation to Gestational Weight
Gain. International Journal of Environmental Research and Public Health, 13(#issue#),
#Pages#
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January 2021
Ashley-Martin, J., L. Dodds, T.E. Arbuckle, M.F. Bouchard, M. Fisher, A.S. Morriset, P.
Monnier, G.D. Shapiro, A.S. Ettinger, R. Dallaire, S. Taback, W. Fraser, R.W. Piatt
(2017). Maternal concentrations of perfluoroalkyl substances and fetal markers of
metabolic function and birth weight. American Journal of Epidemiology, 185(#issue#),
185
Attanasio, R. (2019). Association between perfluoroalkyl acids and liver function: Data on sex
differences in adolescents. Data in Brief, 27(#issue#), 104618
Attanasio, R. (2019). Sex differences in the association between perfluoroalkyl acids and liver
function in US adolescents: Analyses of NHANES 2013-2016. Environmental Pollution,
254(Pt B), 113061
Audet-Delage, Y., N. Ouellet, R. Dallaire, E. Dewailly, P. Ayotte (2013). Persistent organic
pollutants and transthyretin-bound thyroxin in plasma of inuit women of childbearing
age. Environmental Science and Technology, 47(#issue#), 13086
Avanasi, R., H.M. Shin, V.M. Vieira, S.M. Bartell (2016). Impacts of geocoding uncertainty on
reconstructed PFOA exposures and their epidemiological association with preeclampsia.
Environmental Research, 151(#issue#), 505
Avanasi, R., H.M. Shin, V.M. Vieira, S.M. Bartell (2016). Variability and epistemic uncertainty
in water ingestion rates and pharmacokinetic parameters, and impact on the association
between perfluorooctanoate and preeclampsia in the C8 Health Project population.
Environmental Research, 146(#issue#), 299
Avanasi, R., H. Shin, V.M. Vieira, D.A. Savitz, S.M. Bartell (2016). Impact of exposure
uncertainty on the association between perfluorooctanoate and preeclampsia in the C8
health project population. Environmental Health Perspectives, 124(#issue#), 126
Bach, C., B. Matthiesen, Olsen, B. Henriksen (2018). Conditioning on Parity in Studies of
Perfluoroalkyl Acids and Time to Pregnancy: An Example from the Danish National
Birth Cohort. Environmental Health Perspectives, 126(#issue#), 117003
Bach, C.C., B.H. Bech, E.A. Nohr, J. Olsen, N.B. Matthiesen, E C. Bonefeld-J0rgensen, R.
Bossi, T.B. Henriksen (2016). Perfluoroalkyl acids in maternal serum and indices of fetal
growth: The Aarhus Birth Cohort. Environmental Health Perspectives, 124(#issue#), 848
Bach, C.C., B.H. Bech, E.A. Nohr, J. Olsen, N.B. Matthiesen, R. Bossi, N. Uldbjerg, E.C.
Bonefeld-J0rgensen, T.B. Henriksen (2015). Serum perfluoroalkyl acids and time to
pregnancy in nulliparous women. Environmental Research, 142(#issue#), 535
Bach, C.C., Z. Liew, B.H. Bech, E.A. Nohr, C. Fei, E.C. Bonefeld-Jorgensen, T.B. Henriksen, J.
Olsen (2015). Perfluoroalkyl acids and time to pregnancy revisited: An update from the
Danish National Birth Cohort Environmental Health: A Global Access Science. Source,
14(#issue#), 59
Bangma, J., L.A. Eaves, K. Oldenburg, J.L. Reiner, T. Manuck, R.C. Fry (2020). Identifying
Risk Factors for Levels of Per- and Polyfluoroalkyl Substances (PFAS) in the Placenta in
a High-Risk Pregnancy Cohort in North Carolina. Environmental Science and
Technology, 54(13), 8158
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EPA - OGWDW Final Regulatory Determination 4 Support Document - App D, Annotated Bibliography January 2021
Bao, W.W., Z.M. Qian, S.D. Geiger, E. Liu, Y. Liu, S.Q. Wang, W.R. Lawrence, B.Y. Yang,
L.W. Hu, X.W. Zeng, G.H. Dong (2017). Gender-specific associations between serum
isomers of perfluoroalkyl substances and blood pressure among Chinese: Isomers of C8
Health Project in China. Science of the Total Environment, 607-608(#issue#), 1304
Barrett, E.S., C. Chen, S.W. Thurston, L.S. Haug, A. Sabaredzovic, F.N. Fjeldheim, H.
Frydenberg, S.F. Lipson, P.T. Ellison, I. Thune (2015). Perfluoroalkyl substances and
ovarian hormone concentrations in naturally cycling women. Fertility and Sterility,
103(#issue#), 1261
Barry, V., A. Winquist, K. Steenland (2013). Perfluorooctanoic acid (PFOA) exposures and
incident cancers among adults living near a chemical plant. Environmental Health
Perspectives, 121(#issue#), 1313
Barry, V., L.A. Darrow, M. Klein, A. Winquist, K. Steenland (2014). Early life
perfluorooctanoic acid (PFOA) exposure and overweight and obesity risk in adulthood in
a community with elevated exposure. Environmental Research, 132(#issue#), 62
Bassler, J., A. Ducatman, M. Elliott, S. Wen, B. Wahlang, J. Barnett, M.C. Cave (2019).
Environmental perfluoroalkyl acid exposures are associated with liver disease
characterized by apoptosis and altered serum adipocytokines. Environmental Pollution,
247(#issue#), 1055
Beck, I.H., C.A.G. Timmermann, F. Nielsen, G. Schoeters, C. J0hnk, H.B. Kyhl, A. H0st, T.K.
Jensen (2019). Association between prenatal exposure to perfluoroalkyl substances and
asthma in 5-year-old children in the Odense Child Cohort. Environmental Health: A
Global Access Science Source, 18(1), 97
Bell, E.M., E.H. Yeung, W. Ma, K. Kannan, R. Sundaram, M.M. Smarr, G.M. Buck Louis
(2018). Concentrations of endocrine disrupting chemicals in newborn blood spots and
infant outcomes in the upstate KIDS study. Environment International, 121(#issue#), 232
Berg, V., T.H. N0st, R.D. Pettersen, S. Hansen, A.S. Veyhe, R. Jorde, J. 0. Odland, T.M.
Sandanger (2016). Persistent Organic Pollutants and the Association with Maternal and
Infant Thyroid Homeostasis: A Multipollutant Assessment. Environmental Health
Perspectives, 125(#issue#), 127
Berg, V., T.H. N0st, S. Hansen, A. Elverland, A.S. Veyhe, R. Jorde, J. 0. Odland, T.M.
Sandanger (2015). Assessing the relationship between perfluoroalkyl substances, thyroid
hormones and binding proteins in pregnant women; a longitudinal mixed effects
approach. Environment International, 77(#issue#), 63
Berk, M., L.J. Williams, A. Andreazza, J.A. Pasco, S. Dodd, F.N. Jacka, S. Moylan, E.J. Reiner,
P.V.S. Magalhaes (2014). Pop, heavy metal and the blues: secondary analysis of
persistent organic pollutants (POP), heavy metals and depressive symptoms in the
NHANES National Epidemiological Survey. British Medical Journal Open, 4(#issue#),
e005142
Blake, B.E., S.M. Pinney, E.P. Hines, S.E. Fenton, K.K. Ferguson (2018). Associations between
longitudinal serum perfluoroalkyl substance (PFAS) levels and measures of thyroid
hormone, kidney function, and body mass index in the Fernald Community Cohort.
Environmental Pollution, 242(#issue#), 894
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January 2021
Bonefeld-J0rgensen, E.C., M. Long, S.O. Fredslund, R. Bossi, J. Olsen (2014). Breast cancer risk
after exposure to perfluorinated compounds in Danish women: a case-control study
nested in the Danish National Birth Cohort. Cancer Causes and Control, 25(#issue#),
1439
Borghese, M.M., M. Walker, M.E. Helewa, W.D. Fraser, T.E. Arbuckle (2020). Association of
perfluoroalkyl substances with gestational hypertension and preeclampsia in the MIREC
study. Environment International, 141(#issue#), 105789
Braun, J.M., A. Chen, M.E. Romano, A.M. Calafat, G.M. Webster, K. Yolton, B.P. Lanphear
(2016). Prenatal perfluoroalkyl substance exposure and child adiposity at 8 years of age:
The HOME study. Obesity, 24(#issue#), 231
Braun, J.M., A.E. Kalkbrenner, A.C. Just, K. Yolton, A.M. Calafat, A. Sjodin, R. Hauser, G.M.
Webster, A. Chen, B.P. Lanphear (2014). Gestational exposure to endocrine-disrupting
chemicals and reciprocal social, repetitive, and stereotypic behaviors in 4- and 5-year-old
children: the HOME study. Environmental Health Perspectives, 122(#issue#), 513
Buck, C.O., M.N. Eliot, K.T. Kelsey, A.M. Calafat, A. Chen, S. Ehrlich, B.P. Lanphear, J.M.
Braun (2018). Prenatal exposure to perfluoroalkyl substances and adipocytokines: the
HOME Study. Pediatric Research, 84(#issue#), 854
Buck Louis, G.M., C.M. Peterson, Z. Chen, M.L. Hediger, M.S. Croughan, R. Sundaram, J.B.
Stanford, V.Y. Fujimoto, M.W. Varner, L.C. Giudice, A. Kennedy, L. Sun, Q. Wu, K.
Kannan (2012). Perfluorochemicals and endometriosis: The ENDO study. Epidemiology,
23(#issue#), 799
Buck Louis, G.M., K.J. Sapra, D.B. Barr, Z. Lu, R. Sundaram (2016). Preconception
perfluoroalkyl and polyfluoroalkyl substances and incident pregnancy loss, LIFE Study.
Reproductive Toxicology, 65(#issue#), 11
Buck Louis, G.M., S. Zhai, M.M. Smarr, J. Grewal, C. Zhang, K.L. Grantz, S.N. Hinkle, R.
Sundaram, S. Lee, M. Honda, J. Oh, K. Kannan (2018). Endocrine disruptors and
neonatal anthropometry, NICHD Fetal Growth Studies - Singletons. Environment
International, 119(#issue#), 515
Buck Louis, G.M., Z. Chen, E.F. Schisterman, S. Kim, A.M. Sweeney, R. Sundaram, C.D.
Lynch, R.E. Gore-Langton, D.B. Barr (2015). Perfluorochemicals and human semen
quality: the LIFE study. Environmental Health Perspectives, 123(#issue#), 57
Budtz-j0rgensen, E., P. Grandjean (2018). Application of benchmark analysis for mixed
contaminant exposures: Mutual adjustment of perfluoroalkylate substances associated
with immunotoxicity. PLoS ONE, 13(#issue#), e0205388
Buser, M.C., F. Scinicariello (2016). Perfluoroalkyl substances and food allergies in adolescents.
Environment International, 88(#issue#), 74
Byrne, S.C., P. Miller, S. Seguinot-Medina, V. Waghiyi, C.L. Buck, F.A. von Hippel, D.O.
Carpenter (2018). Exposure to perfluoroalkyl substances and associations with serum
thyroid hormones in a remote population of Alaska Natives. Environmental Research,
166(#issue#), 537
Callan, A.C., A. Rotander, K. Thompson, J. Heyworth, J.F. Mueller, J. 0. Odland, A.L. Hinwood
(2016). Maternal exposure to perfluoroalkyl acids measured in whole blood and birth
outcomes in offspring. Science of the Total Environment, 569-570(#issue#), 1107
D-17
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January 2021
Campbell, S., M. Raza, A.Z. Pollack (2016). Perfluoroalkyl substances and endometriosis in US
women inNHANES 2003-2006. Reproductive Toxicology, 65(#issue#), 230
Cao, W., X. Liu, X. Liu, Y. Zhou, X. Zhang, H. Tian, J. Wang, S. Feng, Y. Wu, P. Bhatti, S.
Wen, X. Sun (2018). Perfluoroalkyl substances in umbilical cord serum and gestational
and postnatal growth in a Chinese birth cohort Environment International, 116(#issue#),
197
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metabolic homeostasis in mice. Toxicology, 431(#issue#), 152365
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January 2021
Zhang, L., P. Krishnan, D.J. Ehresman, P.B. Smith, M. Dutta, B.D. Bagley, S.C. Chang, J.L.
Butenhoff, A.D. Patterson, J.M. Peters (2016). Editor's Highlight: Perfluorooctane
Sulfonate-Choline Ion Pair Formation: A Potential Mechanism Modulating Hepatic
Steatosis and Oxidative Stress in Mice. Toxicological Sciences, 153(#issue#), 186
Zhang, Q., H. Zhao, W. Liu, Z. Zhang, H. Qin, F. Luo, S. Leng (2016). Developmental
perfluorooctane sulfonate exposure results in tau hyperphosphorylation and P-amyloid
aggregation in adults rats: Incidence for link to Alzheimer's disease. Toxicology, 347-
349(#issue#), 40
Zhang, Q., W. Liu, H. Zhao, Z. Zhang, H. Qin, F. Luo, Q. Niu (2019). Developmental
perfluorooctane sulfonate exposure inhibits long-term potentiation by affecting AMPA
receptor trafficking. Toxicology, 412(#issue#), 55
Zhang, Y., X. Cao, L. Chen, Y. Qin, Y. Xu, Y. Tian, L. Chen (2020). Exposure of female mice to
perfluorooctanoic acid suppresses hypothalamic kisspeptin-reproductive endocrine
system through enhanced hepatic fibroblast growth factor 21 synthesis, leading to
ovulation failure and prolonged dioestrus. Journal of Neuroendocrinology, 32(5), el2848
Zhao, B., L. Li, J. Liu, H. Li, C. Zhang, P. Han, Y. Zhang, X. Yuan, R.S. Ge, Y. Chu (2014).
Exposure to perfluorooctane sulfonate in utero reduces testosterone production in rat fetal
Leydig cells. PLoS ONE, 9(#issue#), e78888
Zheng, F., N. Sheng, H. Zhang, S. Yan, J. Zhang, J. Wang (2017). Perfluorooctanoic acid
exposure disturbs glucose metabolism in mouse liver. Toxicology and Applied
Pharmacology, 335(#issue#), 41
Zhong, S.Q., Z.X. Chen, M L. Kong, Y.Q. Xie, Y. Zhou, X.D. Qin, G. Paul, X.W. Zeng, G.H.
Dong (2016). Testosterone-Mediated Endocrine Function and TH1/TH2 Cytokine
Balance after Prenatal Exposure to Perfluorooctane Sulfonate: By Sex Status.
International Journal of Molecular Sciences, 17(#issue#), #Pages#
D.5.3 Human and Animal (Mammalian Model)
Chen, G., L.L. Xu, Y.F. Huang, Q. Wang, B.H. Wang, Z.H. Yu, Q.M. Shi, J.W. Hong, J. Li, L.C.
Xu (2018). Prenatal Exposure to Perfluorooctane Sulfonate impairs Placental
Angiogenesis and Induces Aberrant Expression of LncRNA Xist. Biomedical and
Environmental Sciences, 31(#issue#), 843
Koustas, E., J. Lam, P. Sutton, P.I. Johnson, D.S. Atchley, S. Sen, K.A. Robinson, D.A. Axelrad,
T.J. Woodruff (2014). The Navigation Guide - Evidence-based medicine meets
environmental health: Systematic review of nonhuman evidence for PFOA effects on
fetal growth. Environmental Health Perspectives, 122(#issue#), 1015
Lam, J., E. Koustas, P. Sutton, P.I. Johnson, D.S. Atchley, S. Sen, K.A. Robinson, D.A. Axelrad,
T.J. Woodruff (2014). The Navigation Guide - Evidence-based medicine meets
environmental health: Integration of animal and human evidence for PFOA effects on
fetal growth. Environmental Health Perspectives, 122(#issue#), 1040
Lee, J.K., S. Lee, M.C. Baek, B.H. Lee, H.S. Lee, T.K. Kwon, P H. Park, T.Y. Shin, D. Khang,
S.H. Kim (2017). Association between perfluorooctanoic acid exposure and
degranulation of mast cells in allergic inflammation. Journal of Applied Toxicology,
37(#issue#), 554
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Lee, J., S. Lee, Y.A. Choi, M. Jin, Y.Y. Kim, B.C. Kang, M. Kim, H. Dhakal, S.R. Lee, S. Kim,
D. Khang, S.H. Kim (2018). Perfluorooctane sulfonate exacerbates mast cell-mediated
allergic inflammation by the release of histamine. Molecular and Cellular Toxicology,
14(#issue#), 173
Negri, E., F. Metruccio, V. Guercio, L. Tosti, E. Benfenati, R. Bonzi, C. La Vecchia, A. Moretto
(2017). Exposure to PFOA and PFOS and fetal growth: a critical merging of
toxicological and epidemiological data. Critical Reviews in Toxicology, 47(#issue#), 482
Vesterinen, H.M., P.I. Johnson, D.S. Atchley, P. Sutton, J. Lam, M.G. Zlatnik, S. Sen, T.J.
Woodruff (2014). Fetal growth and maternal glomerular filtration rate: A systematic
review. Journal of Maternal - Fetal & Neonatal Medicine, 28(#issue#), 2176
Vesterinen, H.M., R. Morello-Frosch, S. Sen, L. Zeise, T.J. Woodruff (2017). Cumulative effects
of prenatal-exposure to exogenous chemicals and psychosocial stress on fetal growth:
Systematic-review of the human and animal evidence. PLoS ONE, 12(#issue#),
e0176331
D.5.4 PBPK Models
Balk, F.G.P., K. Winkens Piitz, A. Ribbenstedt, M.I. Gomis, M. Filipovic, I.T. Cousins (2019).
Children's exposure to perfluoroalkyl acids - a modelling approach. Environmental
Science: Processes & Impacts, 21(11), 1875
Cheng, W., C.A. Ng (2017). A permeability-limited physiologically based pharmacokinetic
(PBPK) model for perfluorooctanoic acid (PFOA) in male rats. Environmental Science
and Technology, 51(#issue#), 9930
Chou, W.C., Lin, Z. (2019). Bayesian evaluation of a physiologically based pharmacokinetic
(PBPK) model for perfluorooctane sulfonate (PFOS) to characterize the interspecies
uncertainty between mice, rats, monkeys, and humans: Development and performance
verification. Environment International, 129(#issue#), 408
Dietz, R., K. Gustavson, C. Sonne, J.P. Desforges, F.F. Riget, V. Pavlova, M.A. Mckinney, R.J.
Letcher (2015). Physiologically-based pharmacokinetic modelling of immune,
reproductive and carcinogenic effects from contaminant exposure in polar bears (Ursus
maritimus) across the Arctic. Environmental Research, 140(#issue#), 45
Fabrega, F., M. Nadal, M. Schuhmacher, J.L. Domingo, V. Kumar (2016). Influence of the
uncertainty in the validation of PBPK models: A case-study for PFOS and PFOA.
Regulatory Toxicology and Pharmacology, 77(#issue#), 230
Fabrega, F., V. Kumar, E. Benfenati, M. Schuhmacher, J.L. Domingo, M. Nadal (2015).
Physiologically based pharmacokinetic modeling of perfluoroalkyl substances in the
human body. Toxicological and Environmental Chemistry, 97(#issue#), 814
Fabrega, F., V. Kumar, M. Schuhmacher, J.L. Domingo, M. Nadal (2014). PBPK modeling for
PFOS and PFOA: validation with human experimental data. Toxicology Letters,
230(#issue#), 244
Goeden, H.M., C.W. Greene, J.A. Jacobus (2019). A transgenerational toxicokinetic model and
its use in derivation of Minnesota PFOA water guidance. Journal of Exposure Science
and Environmental Epidemiology, 29(#issue#), 183
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January 2021
Kieskamp, K.K., R.R. Worley, E.D. Mclanahan, M.A. Verner (2018). Incorporation of fetal and
child PFOA dosimetry in the derivation of health-based toxicity values. Environment
International, 11 l(#issue#), 260
Loccisano, A.E., M.P. Longnecker, J.L. Campbell, M.E. Andersen, H.J. Clewell (2013).
Development of pbpk models for pfoa and pfos for human pregnancy and lactation life
stages. Journal of Toxicology and Environmental Health, Part A: Current Issues,
76(#issue#), 25
van Asselt, E.D., J. Kowalczyk, J.C. van Eijkeren, M.J. Zeilmaker, S. Ehlers, P. Fiirst, M.
Lahrssen-Wiederholt, H.J. van der Fels-Klerx (2013). Transfer of perfluorooctane
sulfonic acid (PFOS) from contaminated feed to dairy milk. Food Chemistry,
141(#issue#), 1489
Verner, M.A., A.E. Loccisano, N.H. Morken, M. Yoon, H. Wu, R. Mcdougall, M. Maisonet, M.
Marcus, R. Kishi, C. Miyashita, M.H. Chen, W.S. Hsieh, M.E. Andersen, H.J. Clewell,
M.P. Longnecker (2015). Associations of Perfluoroalkyl Substances (PFAS) with Lower
Birth Weight: An Evaluation of Potential Confounding by Glomerular Filtration Rate
Using a Physiologically Based Pharmacokinetic Model (PBPK). Environmental Health
Perspectives, 123(#issue#), 1317
Verner, M.A., G. Ngueta, E.T. Jensen, H. Fromme, W. Voelkel, U.C. Nygaard, B. Granum, M.P.
Longnecker (2016). A Simple Pharmacokinetic Model of Prenatal and Postnatal
Exposure to Perfluoroalkyl Substances (PFASs). Environmental Science and Technology,
50(#issue#), 978
Wambaugh, J.F., R.W. Setzer, A.M. Pitruzzello, J. Liu, D.M. Reif, N.C. Kleinstreuer, N.C.
Wang, N. Sipes, M. Martin, K. Das, J.C. Dewitt, M. Strynar, R. Judson, K.A. Houck, C.
Lau (2013). Dosimetric anchoring of in vivo and in vitro studies for perfluorooctanoate
and perfluorooctanesulfonate. Toxicological Sciences, 136(#issue#), 308
Wong, F., M. Macleod, J.F. Mueller, I.T. Cousins (2014). Enhanced elimination of
perfluorooctane sulfonic acid by menstruating women: evidence from population-based
pharmacokinetic modeling. Environmental Science and Technology, 48(#issue#), 8807
Worley, R.R., J. Fisher (2015). Application of physiologically-based pharmacokinetic modeling
to explore the role of kidney transporters in renal reabsorption of perfluorooctanoic acid
in the rat. Toxicology and Applied Pharmacology, 289(#issue#), 428
Worley, R.R., X. Yang, J. Fisher (2017). Physiologically based pharmacokinetic modeling of
human exposure to perfluorooctanoic acid suggests historical non drinking-water
exposures are important for predicting current serum concentrations. Toxicology and
Applied Pharmacology, 330(#issue#), 9
D.5.5 Human and PBPK Model
Convertino, M., T.R. Church, G.W. Olsen, Y. Liu, E. Doyle, C.R. Elcombe, A.L. Barnett, L.M.
Samuel, I.R. Macpherson, T.R.J. Evans (2018). Stochastic Pharmacokinetic-
Pharmacodynamic Modeling for Assessing the Systemic Health Risk of
Perfluorooctanoate (PFOA). Toxicological Sciences, 163(#issue#), 293
Dzierlenga, M.W., B.C. Allen, H.J. Clewell, M.P. Longnecker (2020). Pharmacokinetic bias
analysis of an association between clinical thyroid disease and two perfluoroalkyl
substances. Environment International, 141(#issue#), 105784
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Dzierlenga, M.W., M. Moreau, G. Song, P. Mallick, P.L. Ward, J.L. Campbell, C. Housand, M.
Yoon, B.C. Allen, H.J. Clewell, M.P. Longnecker (2020). Quantitative bias analysis of
the association between subclinical thyroid disease and two perfluoroalkyl substances in
a single study. Environmental Research, 182(#issue#), 109017
Lenters, V., N. Iszatt, J. Forns, E. Cechova, A. Kocan, J. Legler, P. Leonards, H. Stigum, M.
Eggesb0 (2019). Early-life exposure to persistent organic pollutants (OCPs, PBDEs,
PCBs, PFASs) and attention-deficit/hyperactivity disorder: A multi-pollutant analysis of
a Norwegian birth cohort. Environment International, 125(#issue#), 33
Ruark, C.D., G. Song, M. Yoon, M.A. Verner, M.E. Andersen, H.J. Clewell, M.P. Longnecker
(2017). Quantitative bias analysis for epidemiological associations of perfluoroalkyl
substance serum concentrations and early onset of menopause. Environment
International, 99(#issue#), 245
Verner, M.A., M.P. Longnecker (2015). Comment on "Enhanced elimination of
perfluorooctanesulfonic Acid by menstruating women: evidence from population-based
pharmacokinetic modeling." Environmental Science and Technology, 49(#issue#), 5836
Wong, F., M. Macleod, J.F. Mueller, I.T. Cousins (2015). Response to Comment on "Enhanced
'Elimination of Perfluorooctane Sulfonic Acid by Menstruating Women: Evidence from
Population-based Pharmacokinetic Modeling." Environmental Science and Technology,
49(#issue#), 5838
Wu, H., M. Yoon, M.A. Verner, J. Xue, M. Luo, M.E. Andersen, M.P. Longnecker, H.J. Clewell
(2015). Can the observed association between serum perfluoroalkyl substances and
delayed menarche be explained on the basis of puberty-related changes in physiology and
pharmacokinetics? Environment International, 82(#issue#), 61
D.5.6 Animal and PBPK Model
Dietz, R., J.P. Desforges, K. Gustavson, F.F. Riget, E.W. Born, R.J. Letcher, C. Sonne (2018).
Immunologic, reproductive, and carcinogenic risk assessment from POP exposure in East
Greenland polar bears (Ursus maritimus) during 1983-2013. Environment International,
118(#issue#), 169
D.5.7 Unclear
Cooper, K.R., J. A. Gleason, G.B. Post (2020). Letter Regulatory Toxicology and Pharmacology,
lll(#issue#), 104503
Ding, N., S.D. Harlow, J.F. Randolph, A.M. Calafat, B. Mukheijee, S. Batterman, E.B. Gold,
S.K. Park (2020). Associations of Perfluoroalkyl Substances with Incident Natural
Menopause: The Study of Women's Health Across the Nation. Journal of Clinical
Endocrinology and Metabolism, #volume#(#issue#), #Pages#
Hocevar, B.A., L.M. Kamendulis (2020). Promotion of pancreatic cancer by perfluorooctanoic
acid (PFOA). Cancer Prevention Research, 13(7), 36
Ko, E.B., K.A. Hwang, K.C. Choi (2019). Prenatal toxicity of the environmental pollutants on
neuronal and cardiac development derived from embryonic stem cells Reproductive
Toxicology, 90(#issue#), 15
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Lee, J., S. Oh, H. Kang, S. Kim, G. Lee, L. Li, C.T. Kim, J.N. An, Y.K. Oh, C.S. Lim, D.K.
Kim, Y.S. Kim, K. Choi, J.P. Lee (2020). Environment-Wide Association Study of CKD.
Clinical Journal of the American Society of Nephrology, 15(6), 766
Malone, C., G. £ig, P. Brown, A. Ducatman (2019). Participant Reactions to Medical Screening:
A Survey of Satisfaction With the C8 (PFOA). Health Project New Solutions: A Journal
of Environmental and Occupational Health Policy, 29(2), 186
Mounier, F., V. Loizeau, L. Pecquerie, H. Drouineau, P. Labadie, H. Budzinski, J. Lobry (2020).
Dietary bioaccumulation of persistent organic pollutants in the common sole Solea solea
in the context of global change. Part 2: Sensitivity of juvenile growth and contamination
to toxicokinetic parameters uncertainty and environmental conditions variability in
estuaries. Ecological Modelling, 431(#issue#), #Pages#
Shane, H.L., R. Baur, E. Lukomska, L. Weatherly, S.E. Anderson (2020). Corrigendum to
"Immunotoxicity and allergenic potential induced by topical application of
perfluorooctanoic acid (PFOA) in a murine model" [Food Chem. Toxicol. 136 (2020)
111114], Food and Chemical Toxicology, 137(#issue#), 111 141
Tanner, E.M., M.U. Hallerback, S. Wikstrom, C. Lindh, H. Kiviranta, C. Gennings, C.G.
Bornehag (2020). Early prenatal exposure to suspected endocrine disruptor mixtures is
associated with lower IQ at age seven. Environment International, 134(#issue#), 105185
Wang, L., H. Cao, X. Zhou, Y. Pan, G. Liu, T. Wang, Y. Wang, M. Xiao, S. Chen, Y. Liang.
(2020). Perfluorooctanesulfonate Induces Hepatomegaly and Lipoatrophy in Mice
through Phosphoenolpyruvate Carboxykinase-Mediated Glyceroneogenesis Inhibition.
Environmental Science & Technology Letters, 7(3), 185
Zhang, Y., Y. Le, P. Bu, X. Cheng (2020). Regulation of Hox and ParaHox genes by
perfluorochemicals in mouse liver. Toxicology, 441(#issue#), 152521
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Appendix E:
Regulatory Determination 4 Protocol
An appendix from:
Final Regulatory Determination 4 Support Document
EPA Report 815-R-21-001
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Executive Summary
The Safe Drinking Water Act (SDWA), as amended in 1996, requires the Environmental
Protection Agency (EPA) to make regulatory determinations every five years on at least five
unregulated contaminants from the Contaminant Candidate List (CCL), which SDWA requires
the agency to update every five years. A regulatory determination is a decision about whether or
not to begin the process to propose and promulgate a national primary drinking water regulation
(NPDWR) for an unregulated contaminant.
EPA published the final CCL 4, which listed 109 contaminants, in the FR on November
17, 2016. The contaminants on CCL 4 were evaluated for the fourth round of regulatory
determination (RD 4).
This document is structured as follows: Section E. 1 is an introduction that provides an
overview of the drinking water program risk management processes. Section E.2 presents the
statutory background of the CCL and Regulatory Determination processes and the Unregulated
Contaminant Monitoring Regulation (UCMR) established under the 1996 SDWA Amendments.
Section E.3 provides background on the CCLs and Regulatory Determinations that preceded this
round. Section E.4 provides an overview of the Regulatory Determination process. Sections E.5
through E.7 explain in detail the RD 4 protocol.
RD 4 is a three-phase process. In the Data Availability Phase, described in Section E.5,
EPA conducts an assessment of the availability, for each CCL 4 contaminant, of (a) a suitable
published health assessment from EPA or other sources, (b) finished water occurrence data, with
a preference for nationally representative sources, and (c) analytical methods in widespread use.
Those contaminants with suitable health assessments, occurrence data, and analytical methods
available proceed to the second phase.
In the Data Evaluation Phase, described in Section E.6, EPA gathers available data on
occurrence and exposure, and evaluates occurrence data relative to a health-based threshold, the
Health Reference Level (HRL). Based on this evaluation, EPA identifies contaminants that
appear to occur at levels and frequencies of public health concern (potential positive
determinations), those that have no or low occurrence at levels of health concern (potential
negative determinations), and those that have data gaps. Contaminants that are candidates for
positive and negative determinations proceed to the third phase.
In the Regulatory Determination Assessment Phase, described in Section E.7, EPA
formally evaluates candidates for positive and negative determinations against the three statutory
criteria, by asking the following questions:
• Might the contaminant have an adverse effect on the health of persons?
• Is the contaminant known to occur or is there a substantial likelihood that the
contaminant will occur in PWSs with a frequency and at levels of public health concern?
• In the sole judgment of the Administrator, does regulation of the contaminant present a
meaningful opportunity for health risk reduction for persons served by PWSs?
If the Agency answers "yes" to all three statutory criteria, then the Agency makes a
positive preliminary determination. After a positive determination is finalized, the Agency has 24
months to publish a proposed MCLG and NPDWR and then 18 months to publish a final MCLG
and promulgate a final NPDWR (SDWA section 1412(b)(1)(E)). (SDWA permits the Agency to
extend the promulgation date by an additional nine months if needed.)
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If the Agency answers "no" to one or more of the three statutory criteria, then the Agency
considers making a "negative" determination that an NPDWR is not necessary for that
contaminant at this time. The Agency may also elect to issue no determination for a contaminant
in Phase 3. If a negative determination or no determination is made for a contaminant, the
Agency may also decide to develop and publish a Health Advisory, a non-regulatory action.
While a negative determination is considered a final Agency action for this round of regulatory
determination, the contaminant may be relisted on a future CCL based on newly available health
and/or occurrence information.
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Contents
Executive Summary E-2
Contents E-4
Exhibits E-5
Abbreviations E-6
E. 1 Introduction E-8
E.2 Statutory Background E-8
E.2.1 The Contaminant Candidate List (CCL) E-9
E.2.2 The Unregulated Contaminant Monitoring Regulation (UCMR) E-10
E.2.3 Regulatory Determination E-10
E,3 Past CCL and Regulatory Determination Cycles E-l 1
K.4 Overview of the Regulatory Determination 4 Process E-l 3
E.5 Phase 1: Data Availability E-15
E.5.1 Health Data Availability Assessment E-l6
E.5.2 Occurrence Data Availability Assessment E-19
E.5.3 Analytical Methods Availability Assessment E-21
E.5.4 Evaluation of Outcomes of Health Data, Occurrence Data, and Analytical
Methods Availability Assessments E-21
E.6 Phase 2: Data Evaluation E-21
E.6.1 Phase 2—Step 1: Gather and Evaluate Additional Occurrence Data Sources
Relative to the HRL E-22
E.6.2 Phase 2—Step 2: Identify Contaminants Occurring at Levels and Frequencies of
Public Health Concern E-23
E.6.3 Phase 2—Step 3: Identify Contaminants That Have No or Low Occurrence at
Levels of Public Health Concern E-23
E.6.4 Phase 2—Step 4: Identify Contaminants that Do Not Proceed to Phase 3 and Have
Information or Data Gaps to Be Addressed E-24
E.7 Phase 3: Regulatory Determination Assessment E-24
E.7.1 Evaluation of Statutory Criterion #1 (Adverse Health Effect) E-25
E.7.2 Evaluation of Statutory Criterion #2 (Known or Likely Occurrence in PWSs with
a Frequency and Level of Concern) E-25
E.7.3 Evaluation of Statutory Criterion #3 (Meaningful Opportunity) E-27
E.7.4 Making a Regulatory Determination Decision E-28
E. 8 References Cited E-29
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Exhibits
Exhibit E-l: Drinking Water Program Risk Management Processes E-9
Exhibit E-2: CCL, Regulatory Determination, and UCMR Timeline E-l 1
Exhibit E-3: Summary of Past CCL and Regulatory Determination Cycles E-12
Exhibit E-4: The Three Primary Phases of the Regulatory Determination 4 Process E-l 4
Exhibit E-5: Regulatory Determination 4 Phase 1 Flowchart E-l6
Exhibit E-6: Regulatory Determination 4 Phase 2 Flowchart E-22
Exhibit E-7: Regulatory Determination 4 Phase 3 Flowchart E-25
Exhibit E-8: Regulatory Determination Outcomes E-29
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EPA - OGWDW Final Regulatory Determination 4 Support Document -AppE, RD 4 Protocol January 2021
Abbreviations
ADAF
Age Dependent Adjustment Factor
AT SDR
Agency for Toxic Substances and Disease Registry
BW
Body Weight
CCL
Contaminant Candidate List
CCL 1
First CCL
CCL 2
Second CCL
CCL 3
Third CCL
CCL 4
Fourth CCL
CERCLA
Comprehensive Environmental Response, Compensation, and Liability Act
CRL
Cancer Risk Level
CSF
Cancer Slope Factor
CWS
Community Water System
DDE
l,l-Dichloro-2,2-bis(p-chlorophenyl)ethylene
DL
Detection Limit
DWI
Drinking Water Intake
EPA
Environmental Protection Agency
F
Fraction of Applicable Period of Exposure
FIFRA
Federal Insecticide, Fungicide, and Rodenticide Act
HA
Health Advisory
HRL
Health Reference Level
HED HHRA
Health Effects Division Human Health Risk Assessment
HESD
Health Effects Support Document
IRED
Interim Reregi strati on Eligibility Decision
IRIS
Integrated Risk Information System
MCL
Maximum Contaminant Level
MCLG
Maximum Contaminant Level Goal
MOA
Mode of Action
MRL
Minimum Reporting Level
NCOD
National Contaminant Occurrence Database
NDWAC
National Drinking Water Advisory Council
NIRS
National Inorganics and Radionuclides Survey
NPDWR
National Primary Drinking Water Regulation
NRC
National Research Council
OPP
Office of Pesticide Programs
ORD
Office of Research and Development
OW
Office of Water
PMP
Pesticide Monitoring Program
PPRTV
Provisional Peer-Reviewed Toxicity Values
PWS
Public Water System
RD
Regulatory Determination
RD 4
Regulatory Determination 4
RED
Reregi strati on Eligibility Decision
RfD
Reference Dose
RL
Reporting Level
RSC
Relative Source Contribution
SDWA
Safe Drinking Water Act
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TRED
Tolerance Reassessment Progress and Risk Management Decision
TT
Treatment Technique
UCM
Unregulated Contaminant Monitoring
UCMR
Unregulated Contaminant Monitoring Rule
UCMR 1
First Unregulated Contaminant Monitoring Rule
UCMR 2
Second Unregulated Contaminant Monitoring Rule
UCMR 3
Third Unregulated Contaminant Monitoring Rule
UF
Uncertainty Factor
USGS
United States Geological Survey
WHO
World Health Organization
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Appendix E: Regulatory Determination 4 Protocol
E.l Introduction
Section 1412(b)(1)(B) of the Safe Drinking Water Act (SDWA), as amended in 1996,
requires the Environmental Protection Agency (EPA) to periodically develop or update a list of
substances of public health concern not currently regulated as drinking water contaminants (the
contaminant candidate list, or CCL), and to periodically determine whether regulation is
warranted for contaminants from that list (Regulatory Determination, or RD), The statute directs
EPA to determine whether to regulate at least five contaminants from the most recent CCL every
five years and allow an opportunity for public notice and comment.
The fourth CCL (CCL 4) was published on November 17, 2016 (81 FR 81099; USEPA,
2016a). This document presents the Protocol that EPA will follow as the Agency conducts the
fourth round of Regulatory Determination (Regulatory Determination 4 or RD 4). The document
provides an overview of the Regulatory Determination program and describes the three-phase
procedure that EPA will use to screen CCL 4 contaminants for data availability, select a limited
number of CCL 4 contaminants for Regulatory Determination, and make those determinations.
Final decisions of the RD 4 process will be presented in the Federal Register and
supporting information will be presented in the Regulatory Determination 4 Support Document
and other documentation.
E.l Statutory Background
The 1996 Safe Drinking Water Act (SDWA) Amendments required EPA to develop a
revised risk management and regulatory development approach for drinking water to protect
public health. To meet these requirements EPA developed an integrated framework to:
(1) List currently unregulated contaminants of public health concern, called the
Contaminant Candidate List (CCL);
(2) Collect drinking water monitoring data for unregulated contaminants under the
Unregulated Contaminant Monitoring Regulation (UCMR);
(3) Evaluate CCL contaminants and determine whether or not they warrant a national
primary drinking water regulation (NPDWR), a process called Regulatory
Determination; and
(4) Periodically review existing regulations and assess whether revisions are needed that
maintain or improve public health protection for drinking water consumers (called the
Six-Year Review).
The specific statutory requirements for the CCL and Regulatory Determination programs
can be found in SDWA Section 1412(b)(1). The statutory requirements for the UCMR can be
found in SDWA Section 1445(a)(2). The statutory requirements for the Six-Year Review
program can be found in SDWA 1412(b)(9).
Relationships among the programs are depicted in Exhibit E-l. As the diagram shows,
the Regulatory Determination program is an integral part of a larger framework of programs
intended to manage public health risks posed by drinking water contaminants. EPA has relied on
considerable stakeholder and expert input in developing and implementing each of these
programs. The Regulatory Determination program interacts directly with the CCL and the
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UCMR programs. The CCL, Regulatory Determination, and UCMR programs are briefly
described below.
Exhibit E-1: Drinking Water Program Risk Management Processes
~
On the whole, the further to the right in this diagram, the more specificity and
confidence is required in the supporting data used (e.g., health and
occurrence). Public consultation is involved in each step of the process.
E.2.1 The Contaminant Candidate List (CCL)
The 1996 SDWA Amendments required EPA to publish the first CCL (CCL 1)18
months after the date of their enactment, and to publish a new CCL every five years after
publication of the previous CCL. The CCL is a list of contaminants that are not subject to any
proposed or promulgated NPDWRs, are known or anticipated to occur in public water systems
(PWSs) and may require regulation under SDWA to protect public health. SDWA also specifies
that the CCL must consider substances identified in section 101(14) of the Comprehensive
Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) and substances
registered as pesticides under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA),
and must consider data and information from the National Contaminant Occurrence Database
(NCOD), which EPA established as required under SDWA Section 1445(g). For the CCL,
SDWA requires consultation with the scientific community, including EPA's Science Advisory
Board, and opportunity for public comment. The CCL is the starting point for the Regulatory
Determination process and is the list of priority contaminants that are evaluated for potential
drinking water regulations. Additional information about the CCL process and CCL outcomes,
including references, is provided below in Section E.3.
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E.2.2 The Unregulated Contaminant Monitoring Regulation (UCMR)
The 1996 SDWA Amendments (section 1445(a)(2)) also required that once every five
years EPA issue a new list of no more than 30 unregulated contaminants to be monitored by
PWSs. The UCMR occurrence data are designed to help determine if the contaminant occurs
"with a frequency and at levels of public health concern" (per the second statutory criterion for
regulatory determinations, below) to support the Administrator's determination under the
Regulatory Determination process of whether or not to regulate a contaminant. The 1996 SDWA
Amendments require EPA to enter the monitoring data into a national drinking water
contaminant occurrence database (implemented as NCOD).
E.2.3 Regulatory Determination
SDWA, as amended in 1996, section 1412(b)(1)(B), directs EPA to determine whether or
not to regulate at least five contaminants from the most recent CCL every five years and allow an
opportunity for public notice and comment. The first Regulatory Determination was due within
three and one-half years after the publication of CCL 1, and then once every five years. When
making a regulatory determination, the 1996 SDWA Amendments require that EPA assess three
criteria and decide whether:
(1) The contaminant may have an adverse effect on the health of persons.
(2) The contaminant is known to occur or there is substantial likelihood that the
contaminant will occur in PWSs with a frequency and at levels of public health
concern.
(3) In the sole judgment of the Administrator, regulation of such contaminant presents a
meaningful opportunity for health risk reduction for persons served by PWSs.
If EPA finds that all three of these statutory criteria are met, the Agency makes a
determination to regulate the contaminant (i.e., a positive determination). Following a positive
regulatory determination, SDWA section 1412(b)(1) directs the Agency to publish a proposed
Maximum Contaminant Level Goal (MCLG)1 and NPDWR2 in 24 months. After the proposal,
SDWDA directs the Agency to publish a final MCLG and promulgate a final NPDWR has 18
months.3 EPA may extend the deadline for such promulgation for up to 9 additional months. If
EPA finds that one or more of these statutory criteria are not met, it may make a determination
not to regulate the contaminant (i.e., a negative determination). A determination not to regulate a
contaminant is considered a final Agency action and is subject to judicial review. A third
outcome is for EPA to make no determination for a contaminant. In some cases, a contaminant
may receive no determination due to lack of adequate health effects or occurrence data. In other
cases, a decision may have been made to evaluate the contaminant outside the Regulatory
Determination process (e.g., alongside regulated contaminants as part of the Six-Year Review
process). Generally, only a fraction of CCL contaminants receives a positive or negative
determination in any given round of Regulatory Determination. CCL contaminants that receive
1 An MCLG is the maximum level of a contaminant in drinking water at which no known or anticipated adverse
effect on the health of persons would occur, and which allows an adequate margin of safety. MCLGs are non-
enforceable health goals.
2 An NPDWR is a legally enforceable standard that applies to PWSs. An NPDWR sets a legal limit (called a
maximum contaminant level or MCL) or specifies a certain treatment technique (TT) for public water systems for a
specific contaminant or group of contaminants.
3 The statute authorizes a nine-month extension of this promulgation date.
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no determination in one round of Regulatory Determination may be relisted on the next CCL and
evaluated again in the next round of Regulatory Determination.
The CCL and UCMR are integral components of the coordinated risk management
process that inform and support Regulatory Determination (Exhibit E-2 illustrates the time-line
relationship among the programs). The list of contaminants for each UCMR monitoring cycle are
developed in coordination with the CCL process and other Agency priorities. The programs
continually support and inform each other. The UCMR is designed to inform the Regulatory
Determination process, and in some cases may also collect data that would support regulation
development and help determine whether new or emerging contaminants should be listed on
future CCLs.
Exhibit E-2: CCL, Regulatory Determination, and UCMR Timeline
UCMR 1:
2G Contaminants
{Ma n rta ring 2QG I 2QQ 31
UCMR 2:
25 Contaminants
{Man(taring2008 - 2Q1Q|
UCMR
SOContamin arils
! Ma n rta ring 20 J.3 - 3315|
UCMR 4:
30 Contaminants
{Manilaring2018 - 2Q2Q|
E.3 Past CCL and Regulatory Determination Cycles
As noted above, EPA is conducting the fourth round of Regulatory Determination based
on CCL 4. The following table (Exhibit E-3) summarizes the process and outcomes of the three
previous rounds of CCL and the associated regulatory determinations.
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Exhibit E-3: Summary of Past CCL and Regulatory Determination Cycles
First CCL and Regulatory
Determination Cycle
Second CCL and Regulatory
Determination Cycle
Third CCL and Regulatory
Determination Cycle
CCL 1 was assembled based on
expert knowledge and the
evaluation of readily available
information, with input from the
National Drinking Water Advisory
Council (NDWAC), the scientific
community, and the public
(through stakeholder meetings
and the public comments).
Draft CCL 1 published October 6,
1997 (62 FR 52193; USEPA,
1997).
Final CCL 1 published March 2,
1998 (63 FR 10273; USEPA,
1998a)
The final CCL 1 contained 50
chemical and 10 microbiological
contaminants.
Preliminary Regulatory
Determination published June 3,
2002 (67 FR 38222; USEPA,
2002a).
Final Regulatory Determination
published July 18, 2003 (68 FR
42898; USEPA, 2003).
Remaining 51 CCL 1
contaminants carried forward
onto the second CCL (CCL 2).
Draft CCL 2 published on April 2,
2004 (69 FR 17406; USEPA,
2004).
Final CCL 2 published on
February 24, 2005 (70 FR 9071;
USEPA, 2005a).
Preliminary Regulatory
Determination published on May
1, 2007 (72 FR 24106; USEPA,
2007).
Final Regulatory Determination
published on July 30, 2008 (73
FR 44251; USEPA, 2008a).
CCL 3 was developed using a
systematic process based on
input and recommendations from
the National Research Council
(NRC), NDWAC and the public,
involving the use of algorithms to
screen and evaluate
contaminants based on
properties (prevalence,
magnitude, persistence/mobility,
severity and potency) using data
from a wide range of sources.
Draft CCL 3 published on
February 21, 2008 (73 FR 9628;
USEPA, 2008b).
Final CCL 3 published on
October 8, 2009 (74 FR 51850;
USEPA, 2009a).
The final CCL 3 consists of 104
chemicals or chemical groups
and 12 microbiological
contaminants.
Preliminary Regulatory
Determination published on
October 20, 2014 (79 FR 62715;
USEPA, 2014a).
Final Regulatory Determination
published on January 4, 2016
(81 FR 13; USEPA, 2016b).
Outcomes:
Acanthamoeba-. negative
determination (information about
microbe posted on EPA's
website)
Aldrin: negative determination
Dieldrin: negative determination
Hexachlorobutadiene: negative
determination
Manganese: negative
determination (health advisory
issued)
Metribuzin: negative
determination
Outcomes:
Boron: negative determination
(health advisory issued)
Dacthal mono- and di-acid
degradates: negative
determination (health advisory
issued)
1,1-Dichloro-2,2-bis(p-
chlorophenyl)ethylene (DDE):
negative determination
1.3-Dichloropropene (Telone):
negative determination
2.4-Dinitrotoluene: negative
determination (health advisory
issued)
Outcomes:
Dimethoate: negative
determination
1,3-Dinitrobenzene: negative
determination
Perchlorate: positive
determination (made off-cycle,
but counted for purposes of
Regulatory Determination 3)
Strontium: preliminary positive
determination (final
determination pending)
Terbufos: negative determination
Terbufos sulfone: negative
determination
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First CCL and Regulatory
Determination Cycle
Second CCL and Regulatory
Determination Cycle
Third CCL and Regulatory
Determination Cycle
Naphthalene: negative
determination
Sodium: negative determination
(health advisory issued)
Sulfate: negative determination
(health advisory issued)
2,6-Dinitrotoluene: negative
determination (health advisory
issued)
S-Ethyl dipropylthiocarbamate
(EPTC): negative determination
Fonofos: negative determination
Terbacil: negative determination
1,1,2,2-Tetrachloroethane:
negative determination (health
advisory issued)
Perchlorate is an example of a contaminant handled off-cycle. The final determination for
perchlorate is considered part of the third Regulatory Determination cycle. EPA published a
preliminary determination not to regulate perchlorate with an NPDWR in October 2008 (73 FR
60262; USEPA, 2008c). In 2009, EPA solicited input from the public on approaches for
analyzing and evaluating perchlorate data (74 FR 41883; USEPA, 2009b and 74 FR 48541;
USPEA, 2009c), and in February 2011, EPA issued a final determination to regulate perchlorate
(76 FR 7762; USEPA, 201 la). This decision was the first time EPA decided to regulate a
substance from the CCL. On May 23, 2019, EPA released a pre-publication notice of proposed
rulemaking that seeks public input on a range of options regarding the regulation of perchlorate
in PWSs.
The draft CCL 4 was published on February 4, 2015 (80 FR 6076; USEPA, 2015). The
final CCL 4 was published on November 17, 2016 (81 FR 81099; USEPA, 2016a). The final
CCL 4 consists of 97 chemicals or chemical groups and 12 microbiological contaminants. Most
CCL 4 contaminants were carried over from the third CCL (CCL 3). EPA added two
contaminants (manganese and nonylphenol) to the CCL 4 based on nominations. EPA struck
from the list those CCL 3 contaminants that had been subject to recent preliminary and/or final
regulatory determinations (perchlorate, dimethoate, 1,3-dinitrobenzene, terbufos, terbufos
sulfone, strontium) and three pesticides with cancelled registrations (disulfoton, fenamiphos,
molinate).
E.4 Overview of the Regulatory Determination 4 Process
EPA has developed a three-phased process to perform the fourth cycle of Regulatory
Determination. The three phases of the Regulatory Determination 4 (RD 4) Process are (1) the
Data Availability Phase, (2) the Data Evaluation Phase, and (3) the Regulatory Determination
Assessment Phase. The overall RD 4 Process is displayed in Exhibit E-4.
The purpose of the first phase, the Data Availability Phase, is to determine if EPA "may
have" sufficient data to characterize the potential health effects and known or likely occurrence
in drinking water. Although contaminants must have sufficient data to evaluate the statutory
criteria in Phase 3, EPA does not want to rule out any contaminants prematurely. Therefore, if
sufficient health and occurrence data "are likely" to be available, the contaminants will be placed
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on a "short list" for the Data Evaluation Phase, the second phase of the Regulatory
Determination process.
During the second phase, EPA will further evaluate each contaminant on the short list to
identify those that have sufficient data for EPA to assess the three statutory criteria. As part of
the second phase, EPA will specifically focus its efforts to identify those contaminants or
contaminant groups that are occurring or have substantial likelihood to occur at levels and
frequencies of public health concern, based on the best available data.
If sufficient data are available for a contaminant to characterize the potential health
effects and known or likely occurrence in drinking water, the contaminant will be evaluated
against the three statutory criteria in the Regulatory Determination Assessment Phase, which is
the third phase of the approach. Results will be published in the Federal Register as preliminary
regulatory determinations for public comment. EPA will analyze and respond to the comments
and issue the final determinations in the Federal Register.
Contaminants that do not advance from one phase to the next or do not receive a
regulatory determination due to insufficient data are recognized as having information gaps by
EPA. EPA can work towards filling information gaps: e.g., by including a contaminant on the
next round of UCMR, developing an analytical method, and/or conducting a health assessment.
Exhibit E-4: The Three Primary Phases of the Regulatory Determination 4 Process
CCL 4
Phase 1: Data Availability
Baa N
essment
Occurrence Dai
Availability Asse
'Nationally representative
finished water data, or
"O ther finished water
data showing detects
over H Heal th Reference
leuetiMl.}
f Analytical ^
Methods
Availability
155 ess me nt
Evaluation of Phasel Data Availability Assessments
Does the Contaminant potentially have sufficient health
and occurrence data and methods available?
TF
Phase 2: Data Evaluation
Step i:
Gather &
evaluate additional
occurrence data
Sources relative to HRL
Identify
contaminants with no or
bw occurrence at levels
of public health concern
Phase 3:
Regulatory Determination Assessment
Evaluate Statutory Criterion si:
Health Assessment
Might the contaminant have an
adverse effect on the health of
persons?
Evaluate Statutory Criterion S2:
Occurrence Assessment
Is the c&itamimnt krxtwn to occur or is
there substan tial Bkelihaod that the
contaminant will occur above the HRL at a
frequency and level of public heath
concern?
Evaluate Statutory Criterion S3:
Meaningful Opportunity Assessment
(Administrator's Decision)
In the sot judgment of the Administrator,
does regulation of such contaminant
present a meaningful opportunity for
health risk reduction for persons served by
public water systems?
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In addition to considering CCL 4 contaminants individually, EPA also may consider
some of them collectively as groups. EPA considers grouping contaminants for purposes of
regulation when it may strengthen public health protection from contaminants in drinking water.
When deciding whether to consider two or more contaminants as a group, EPA will evaluate
whether the contaminants have some or all of the following characteristics:
(a) have a similar health endpoint,
(b) can be measured by the same analytical methods,
(c) can be treated using the same technologies or treatment techniques, and/or
(d) have been shown to occur together.
The purpose of grouping contaminants by a similar health endpoint is to better protect
public health from the potential risk of co-occurring contaminants with common additive or
synergistic (i.e., greater than additive) adverse health effects. The affected target organ(s),
specific endpoint(s), mechanism(s)/mode(s) of action, functional molecular group(s) and the
potential for additive risk based on available data are considered in the selection of endpoints
that are used to group contaminants for regulatory consideration. The ability to measure a group
of contaminants by the same analytical method and to treat the contaminants using the same
technology or treatment technique approach improves cost effectiveness and efficiency of
regulating the group of contaminants because there is likely only a marginal additional cost for
monitoring and/or treating additional contaminants in the group if they co-occur.
When grouping contaminants for consideration under the Regulatory Determination 4
Protocol using the evaluation criteria listed above, EPA may also choose to include non-CCL
contaminants in a group with one or more CCL contaminants.
When working with groups, the Agency will gather data (where available) on both the
individual contaminants and the group. The Agency may determine that a group satisfies a
particular criterion in the Regulatory Determination 4 Protocol even if one or more individual
component contaminants do not.
The following sections describe in more detail the steps involved in the three primary
phases of the RD 4 process.
E.5 Phase 1: Data Availability
Within the Data Availability Phase, three assessments will be conducted: the Health Data
Availability Assessment, the Occurrence Data Availability Assessment, and the Analytical
Methods Availability Assessment. Contaminants and/or groups that pass all three assessments
will be placed on the "short list" for further evaluation in the Data Evaluation Phase (see Exhibit
E-5).
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Exhibit E-5: Regulatory Determination 4 Phase 1 Flowchart
Have a co m pleted/i n
progress health
assessment from EFA
[e.g., IRE, OPP,OWfor
other approved source
{e.g, ATSOR, UVHO)?
fe there a nationally
representatrve finished
water occurence data
source (e.g., UCMR
AM/SS, LCM, N IRS}?
Does
Contaminant
hauea widely
available
analytical
method?
Is there documented
occurrence in finished
water at levels -- 1/2 URL?
E.5.1 Health Data Availability Assessment
In making a regulatory determination for a contaminant, SDWA requires that the Agency
assess whether the contaminant "may have an adverse effect on the health of persons." The
Agency relies on EPA health assessments and externally peer-reviewed health assessments from
other agencies to determine if, how, and at what level a contaminant "may have an adverse effect
on the health of persons." Sources of health assessments for use in Regulatory Determination 4
may include:
• EPA assessments
o Office of Water (OW) health assessments: Health Advisory (HA) documents,
Health Effects Support Documents (HESDs)
o Office of Research and Development (ORD) Integrated Risk Information System
(IRIS) assessments
o ORD Provisional Peer-Reviewed Toxicity Values (PPRTVs)
o Office of Pesticide Programs (OPP) health assessments: Reregi strati on Eligibility
Decisions (REDs), Interim Reregi strati on Eligibility Decisions (IREDs),
Tolerance Reassessment Progress and Risk Management Decisions (TREDs),
Health Effects Division Human Health Risk Assessments (HED HHRAs)
Agency for Toxic Substances and Disease Registry (ATSDR) Toxicological Profiles
Health Canada Guidelines for Drinking Water
World Health Organization (WHO) Drinking Water Guidelines
Publicly available state assessments that have been externally peer-reviewed and provide
new science not considered in other RD 4 assessment sources listed above
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To support a regulatory determination, EPA evaluates whether a health assessment is
available. The cutoff date for publication of health assessments that could be considered in
Regulatory Determination 4 is March 1, 2019. EPA also evaluates whether health assessments
use methods, standards, and guidelines comparable to those of current EPA health assessments.
Specifically, they should be consistent with EPA's current guidelines and guidance documents:
• Guidelines for Developmental Toxicity Risk Assessment (U SEP A, 1991)
• Guidelines for Reproductive Toxicity Risk Assessment (USEPA, 1996)
• Guidelines for Neurotoxicity Risk Assessment (U SEP A, 1998b)
• A Review of the Reference Dose and Reference Concentration Processes (USEPA,
2002b)
• Guidelines for Carcinogen Risk Assessment (USEPA, 2005b)
• Supplemental Guidance for Assessing Susceptibility from Early-Life Exposure to
Carcinogens (USEPA, 2005c)
• A Framework for Assessing Health Risks of Environmental Exposures to Children
(USEPA, 2006)
• Exposure Factors Handbook (USEPA, 201 lb) and subsequent updates made to
individual chapters (see https://www.epa.gov/expobox/about-exposure-factors-
handbook)
• Recommended Use of Body Weight4 as the Default Method in Derivation of the Oral
Reference Dose (USEPA, 201 lc)
• Benchmark Dose Technical Guidance Document (USEPA, 2012)
• Child-Specific Exposure Scenarios Examples (USEPA, 2014b)
• Guidance for Applying Quantitative Data to Develop Data-Derived Extrapolation
Factors for Interspecies and Intraspecies Extrapolation (USEPA, 2014c)
If a contaminant is the subject of multiple assessments meeting the acceptance criteria,
EPA will select one for the purpose of deriving a Health Reference Level (HRL). EPA will rely
on an EPA assessment unless another approved assessment uses studies published after EPA's
most recent assessment to derive a reference dose (RfD) and/or cancer slope factor (CSF). If
multiple assessments are available from EPA, or if there are multiple assessments presenting
more current science, EPA selects the most recently completed assessment.
An HRL is not a final determination on establishing a protective level of a contaminant in
drinking water for a particular population; it is derived prior to development of a complete health
and exposure assessment and can be considered a screening value. An HRL is a health-based
concentration against which the Agency evaluates occurrence data when making decisions about
regulatory determinations. There are two general approaches to the derivation of an HRL. One
general approach is used for chemicals with a threshold dose-response (usually involving non-
cancer endpoints, and occasionally cancer endpoints). The second general approach is used for
chemicals that exhibit a linear, non-threshold response to dose (as is typical of carcinogens). A
variant version of the second approach is used when a carcinogen with a linear dose-response has
a known mutagenic mode of action.
HRLs for contaminants with a threshold dose-response (typically non-cancer
endpoints) are calculated as follows:
BW
HRL = RfD* — * RSC
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HRLs for contaminants with a linear dose-response (typically cancer endpoints) are
calculated as follows:
CRL BW
HRL = —— *
CSF DWl
HRLs for carcinogenic contaminants with a known mutagenic mode of action are
calculated as follows:
CRL 1
Where:
HRL = Health Reference Level (|ag/L)
RfD = Reference Dose (mg/kg/day)
DWI = Drinking Water Intake (L)
BW = Body weight (kg)
CSF = Cancer Slope Factor (mg/kg/day)-1
CRL = Cancer risk level, assumed to be 1 in a million (1 x 10"6)
ADAF = The Age Dependent Adjustment Factor for the age group i (by default, ADAF =
10 from birth to two years of age; ADAF = 3 from two to sixteen years of age; ADAF = 1 from
sixteen to seventy years of age)
f = fraction of applicable period of exposure (by default, lifetime of seventy years)
represented by age group i
RSC = Relative Source Contribution, which is the portion (percentage) of an individual's
exposure attributed to drinking water rather than other sources (e.g., food, ambient air). In
Regulatory Determination, a 20 percent RSC is used for HRL derivation because (1) HRLs are
developed prior to a complete exposure assessment, and (2) 20 percent is the lowest and most
conservative RSC used in the derivation of an MCLG for drinking water.
In prioritizing the contaminants of greatest public health concern for regulatory
determination, Section 1412(b)(1)(C) of SDWA requires the Agency to consider "among other
factors of public health concern, the effect of such contaminants upon subgroups that comprise a
meaningful portion of the general population (such as infants, children, pregnant women, the
elderly, individuals with a history of serious illness, or other subpopulations) that are identifiable
as being at greater risk of adverse health effects due to exposure to contaminants in drinking
water compared to the general population." If appropriate and if adequate data are available, the
Agency will take into account data from sensitive populations and lifestages quantitatively when
deriving HRLs for regulatory determinations in the following manner:
(a.) For non-carcinogens, an HRL can be developed for a sensitive population if data
are available to associate exposure with the critical health endpoint in a specific group or
during a specific period of sensitivity. Age-specific drinking water intake to body weight
ratio values from the Exposure Factors Handbook (USEPA, 201 lb) can be used to reflect the
period of exposure more accurately. When exposure to a contaminant is associated with a
developmental effect, EPA derives the HRLs using the exposure factors of a bottle-fed infant
to be protective of all children (assuming that the adverse effect identified could occur during
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the window of time when the infant is formula-fed). The Agency can also apply specific
uncertainty factors (UFs) when deriving the reference dose (RfD) if toxicological data are
lacking for a sensitive population. Two common UFs that can be applied to account for
sensitive populations are: (1) variation in sensitivity among the members of the human
population (i.e., intraspecies variability) and (2) uncertainty associated with an incomplete
database.
(b.) For HRLs developed for carcinogens with a mutagenic mode of action (MOA),
the 2005 Cancer Guidelines require consideration of increased risks due to early-life
exposure. When chemical-specific data to quantify the increased risk are lacking, Age
Dependent Adjustment Factors (ADAFs) are applied, generally with a 10-fold adjustment for
early life exposures, a 3-fold adjustment for childhood/adolescent exposures, and no
additional adjustment for exposures later in life (as shown above). Age-specific drinking-
water-intake-to-body-weight ratio values are also applied from the Exposure Factors
Handbook (USEPA, 201 lb). In cases where the data on the MOA are lacking, a default low-
dose linear extrapolation approach without ADAFs is used.
If a contaminant has a health assessment available that meets the criteria described above,
on the basis of which the Agency can calculate an HRL, it passes the Health Data Availability
Assessment.
E.5.2 Occurrence Data Availability Assessment
In making a regulatory determination, SDWA requires that the Agency assess whether
the contaminant "is known to occur or there is substantial likelihood that the contaminant will
occur in PWSs with a frequency and at levels of public health concern." When addressing this
criterion, the Agency gives preference to nationally representative finished drinking water
occurrence data, and also evaluates other sources of finished water data. (Finished water is water
that has undergone treatment and is ready for distribution to customers.) The steps for this
assessment will involve answering the following two questions:
• Are nationally representative finished water occurrence data available?
• Are non-nationally-representative finished water occurrence data available that show
occurrence at levels of potential public health concern?
If the answer to either question is "yes," the contaminant passes the Occurrence Data
Availability Assessment.
E.5.2.1 Nationally Representative Finished Water Occurrence Data
Nationally representative data sets will be the primary source of the drinking water
occurrence data used by the Agency to evaluate whether or not a contaminant is "known to
occur" in PWSs with a frequency and at levels of public health concern. If a contaminant has
data available from at least one of the following data sources, which are administered or
overseen by EPA, then it has nationally representative drinking water occurrence data:
• Third Unregulated Contaminant Monitoring Regulation (UCMR 3) - Assessment
Monitoring or Screening Survey.
• Second Unregulated Contaminant Monitoring Regulation (UCMR 2) - Assessment
Monitoring or Screening Survey.
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• First Unregulated Contaminant Monitoring Regulation (UCMR 1) - Assessment
Monitoring.
• Unregulated Contaminant Monitoring (UCM) program.
• National Inorganics and Radionuclides Survey (NIRS).
These data sources will be described in the Regulatory Determination 4 Support
Document.
If a contaminant has nationally representative data, it passes the Occurrence Data
Availability Assessment. If it does not, EPA will evaluate whether pertinent non-nationally-
representative data are available, as described below.
E.5.2.2 Non-Nationally-Representative Finished Water Occurrence Data that
Show Occurrence at Levels of Public Health Concern
If nationally representative occurrence data are not available, EPA will evaluate
additional sources of finished water data. Source of non-nationally-representative finished water
data may include:
• Finished water assessments by federal agencies (e.g., EPA and the United States
Geological Survey (USGS)). These may be assessments that are geographically
distributed across the nation but not intended to be statistically representative of the
nation. Examples include the UCMR 1 Screening Survey and the 1996 Monitoring
Requirements for Public Drinking Water Supplies, also known as the Information
Collection Rule.
• State-level finished water monitoring data.
• Research performed by institutions, universities, and government scientists (e.g.,
information published in the scientific literature).
• Other supplemental finished water monitoring surveys (e.g., Pesticide Monitoring
Program (PMP) and other targeted surveys or localized state/federal monitoring surveys).
Non-nationally-representative data may be sufficient to evaluate the statutory criteria and
support regulatory determination in some cases. It is difficult to determine that a contaminant is
not occurring or not likely to occur based on single studies or evaluations containing non-
nationally-representative data because the data are limited in scope and the contaminant could be
occurring at water systems of other types or in other locations. However, a compilation of non-
nationally-representative data sources can support a determination that there is a "substantial
likelihood that the contaminant will occur in PWSs with a frequency and at levels of public
health concern." Therefore, a contaminant without nationally representative finished water
occurrence data will be evaluated further to determine whether there is documented occurrence
in finished water at a level of public health concern. The purpose of this step is to not rule out
any contaminants too early in the process that may have occurrence at levels of public health
concern in finished water.
The Agency will assess whether non-nationally-representative finished water occurrence
data show at least one detection in finished water at levels > V2 the HRL for the critical
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endpoint.2 If a contaminant has such finished water occurrence data showing at least one
detection > V2 HRL, the contaminant passes the Occurrence Data Availability Assessment.
E.5.3 Analytical Methods Availability Assessment
In certain limited cases, a contaminant's occurrence data may have been gathered using a
specialized or experimental method that is not in general use. If a widely available analytical
method does not exist, the contaminant will not be a viable candidate for regulation with an
MCL. With that in mind, in the Analytical Methods Availability Assessment EPA will determine
for each contaminant whether a widely available analytical method for monitoring exists. (A
widely available analytical method is a method employing technology that is commonly in use at
numerous drinking water laboratories.) If a widely available analytical method exists, the
contaminant passes the Analytical Methods Availability Assessment. If a widely available
analytical method does not exist, EPA may advance the contaminant to Phase II if the agency
determines that indicator or surrogate monitoring, or use of a treatment technique (TT), could
allow for effective regulation and there is compelling evidence of occurrence.
E.5.4 Evaluation of Outcomes of Health Data, Occurrence Data, and Analytical
Methods Availability Assessments
After conducting the three assessments, the Agency will identify contaminants that meet
all three criteria:
• An EPA health assessment or an externally peer-reviewed health assessment from
another agency that conforms with current EPA guidelines is available, conforming with
current EPA guidelines, from which an HRL can be derived.
• Either (a) nationally representative finished water occurrence data are available, or (b)
non-nationally representative finished water occurrence data show occurrence at levels >
V2 HRL.
• A widely available analytical method for monitoring exists.
If a contaminant (or group) meets all of the criteria, it will be placed on the "short list"
and proceed to Phase 2, the Data Evaluation Phase.
Contaminants that do not proceed to Phase 2 will be recognized as having information
gaps by EPA. Other actions at EPA can work towards filling information gaps (e.g., by including
a contaminant on the next round of UCMR, developing an analytical method, and/or conducting
a health assessment).
E.6 Phase 2: Data Evaluation
The Regulatory Determination "short list" is a list of contaminants that have been
identified in Phase 1 as having sufficient data to warrant an expanded assessment. The purpose
of Phase 2 is to undertake the following for the "short list" contaminants:
(1) Gather additional data on occurrence in finished and ambient water and related data
(e.g., on production, use, release, and environmental fate and transport) and evaluate
occurrence data relative to the HRL.
2 Use of the Vi HRL threshold in RD efforts is based on a recommendation from the NDWAC working grouping that
provided recommendations on the first regulatory determination effort (USEPA, 2000).
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(2) Identify contaminants occurring with levels and frequencies of public health concern.
These will become "potential positive regulatory determinations."
(3) Identify contaminants that are occurring with levels and frequencies with no or low
potential for public health concern. These will become "potential negative regulatory
determinations."
(4) Identify contaminants that do not proceed to Phase 3 because they have data gaps to
be addressed.
The steps involved in the Data Evaluation Phase are described in the sections that
follow. Note that the Agency does not have a rigid threshold for health or occurrence values that
trigger a finding that a contaminant or group is or is not of public health concern. There are a
number of factors to consider in evaluating a potential public health concern, including the
critical health effect(s), the potency of a contaminant, the concentrations at which the
contaminant is occurring in finished water and ambient or source water, how frequently the
contaminant is found, the geographic distribution (national, regional, or local occurrence),
patterns of industrial or agricultural usage and release, other possible sources of exposure, and
potential impacts on sensitive populations or lifestages. Given the many possible combinations
of factors and the constantly evolving science, EPA believes it is best to study contaminants in
depth and present the best available information that helps determine whether the occurrence of a
contaminant or group is of public health concern. See Exhibit E-6 for an overview of Phase 2.
Exhibit E-6: Regulatory Determination 4 Phase 2 Flowchart
I ^
Consider the
fa llowing factors:
¦ Frequency of
detection > HRL
& >1/2 URL in
finished water
- Production, use,
rel ease-
environmental
fate, occurrence
in ambient water
- Data gaps?
¦ lb contaminant
part of a group?
*
4
High Occurrence at or above HRL?
Enter Phase3 as potential positive,
and gather additional health effects
literature
E.6.1 Phase 2—Step 1: Gather and Evaluate Additional Occurrence Data Sources
Relative to the HRL
In this step, the Agency compiles, analyzes, and evaluates all available information and
data that shed light on occurrence and potential occurrence in the nation's drinking water. These
data may include nationally representative and non-nationally-representative finished water
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occurrence data and ambient and source water occurrence data (evaluated relative to the HRL
threshold, V2 the HRL, and the minimum reporting level or MRL), as well as data and
information on production, use, release to the environment, and fate and transport. Analyses
could include modeling to characterize the distribution of concentrations below the MRL (see
Section E.7.2). This information will be used in steps 2 and 3 of Phase 2 (see E.6.2 and E.6.3),
and also in Phase 3 if a contaminant proceeds to that phase.
E.6.2 Phase 2—Step 2: Identify Contaminants Occurring at Levels and Frequencies
of Public Health Concern
In this step, the Agency will identify contaminants and groups occurring at levels and
frequencies of public health concern that will proceed to Phase 3, the Regulatory Determination
Assessment Phase for a potential positive determination. The candidate contaminants identified
in this step will be the highest priority for RD 4. The Agency will consider the following
information when identifying these contaminants:
• How many samples (number and percent) have detections > HRL and > V2 HRL in
nationally representative and other finished water occurrence data?
• How many systems (number and percent) have detections > HRL and > V2 HRL in
nationally representative and other finished water occurrence data?
• Are there uncertainties or limitations with the data and/or analyses, involving (for
example) the age of the dataset, analytical method limitations (i.e., MRL > HRL), and/or
representativeness of the data (e.g., limited to a specific region) that may cause
misestimation of occurrence in finished water at levels and frequency of public health
concern? If the HRL is lower than detection or reporting limits, parametric statistical
modeling techniques may be available that could estimate (with quantified uncertainty)
occurrence at the level of the HRL.
E.6.3 Phase 2—Step 3: Identify Contaminants that Have No or Low Occurrence at
Levels of Public Health Concern
After identifying contaminants that are occurring at levels and frequencies of public
health concern (Section E.6.2), the Agency will evaluate the remaining contaminants on the short
list to identify contaminants with no to low occurrence at levels of health concern that should
proceed to Phase 3 for a potential negative determination. Because the primary goal of
Regulatory Determination is to focus on contaminants of public health concern, potential
negative determinations are a lower priority than potential positive determinations. The Agency
will consider the following information in selecting contaminants of no or low potential for
public health concern to proceed to Phase 3:
• Does the contaminant have nationally representative finished water data showing no or
low number and percent of detections > HRL? (As noted above, while non-nationally-
representative data showing high levels and/or frequency of occurrence can support a
positive determination, nationally representative finished water data showing no or low
occurrence is required to make a negative determination.)
• If a contaminant has other finished water data in addition to nationally representative
finished water data, does it support no or low potential for occurrence in drinking water?
• Does additional occurrence information of high quality support low or no occurrence or
potential for occurrence in drinking water? For example, is the occurrence in
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ambient/source water at levels below the HRL? How are releases to the environment or
use/production changing over time?
• Are there minimal critical information/data gaps after evaluating the available health or
occurrence data?
E.6.4 Phase 2—Step 4: Identify Contaminants that Do Not Proceed to Phase 3 and
Have Information or Data Gaps to Be Addressed
Those contaminants and groups that do not proceed to Phase 3 (in steps 2 or 3 of Phase 2,
described above) because of data gaps, and receive no regulatory determination, will be
considered for the next CCL. These contaminants are recognized as having information gaps by
EPA. Other actions at EPA can work towards filling information gaps (e.g., by including a
contaminant on the next round of UCMR, developing an analytical method, and/or conducting a
health assessment).
E.7 Phase 3: Regulatory Determination Assessment
The Regulatory Determination Assessment Phase involves a complete evaluation of the
statutory criteria for each contaminant or group of contaminants that have passed Phase 2 and
have sufficient information and data for making a regulatory determination. In this phase, the
Agency evaluates the following statutory criteria:
• Statutory Criterion #1: Might the contaminant have an adverse effect on the health of
persons?
• Statutory Criterion #2: Is the contaminant known to occur or is there a substantial
likelihood that the contaminant will occur in PWSs with a frequency and at levels of
public health concern?
• Statutory Criterion #3: In the sole judgment of the Administrator, does regulation of
such contaminant present a meaningful opportunity for health risk reduction for persons
served by PWSs?
The following sections discuss the factors that the Agency considers in evaluating each of
the three statutory criteria. Note that the third statutory criterion requires the judgment of the
Administrator. See Exhibit E-7 for an overview of Phase 3.
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Exhibit E-7: Regulatory Determination 4 Phase 3 Flowchart
High Occurrence at or
aboveHRL?
Enter Phase 3 as
0
r 1
Statutory
Criterion #1
Contaminant
r 1
Statutory
Criterion #2:
potential positive
causes adverse
t4>
Contaminant is
c[>
heafth effects
In own or likely
to occur wit ha
Loiw/Nb Ottunente
(all
frequency at
l/
i or above HRL?
contaminants at
levds of concern
Enter Phase 3 as
this stage should
potential negative
pass this)
L J
Statutory
Criterion #3: Is
there a
meaningful
opportunity to
reduce risk to
the public?
Administrator's
choice
Positive
determination
Consider making a negative determination
E.7.1 Evaluation of Statutory Criterion #1 (Adverse Health Effect)
For criterion #1, the Agency evaluates whether a contaminant has a publicly available
EPA health assessment or an externally peer-reviewed health assessment from another agency
conforming with current EPA guidelines, from which an HRL can be derived. The HRL derived
in or from the health assessment takes into account many of the key elements that are considered
when evaluating the first criterion, which include the mode of action, the critical health effect(s),
the dose-response relationship for critical health effect(s) and impacts on sensitive population(s)
or lifestages. As noted earlier, an HRL is not a final determination on establishing a protective
level of a contaminant in drinking water for a particular population. The HRL is derived prior to
development of a complete health and exposure assessment and can be considered a screening
value. The HRL is a health-based concentration against which EPA compares the concentrations
of a contaminant found in public water systems to determine if the levels are of potential public
health concern.
If an acceptable health assessment is available, demonstrating adverse health effects, the
Agency answers "yes" to the first statutory criterion. Otherwise, the Agency answers "no" to the
first statutory criterion. (In practice, it is expected that any contaminant that reaches Phase 3 will
receive a "yes" to the first criterion.)
E.7.2 Evaluation of Statutory Criterion #2 (Known or Likely Occurrence in PWSs
with a Frequency and Level of Concern)
The occurrence data for each contaminant will be compared to the HRL to determine if
the contaminant occurs at a frequency and levels of public health concern. The following factors,
further refined from the previous phase and categorized by importance, will be considered when
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identifying contaminants or contaminant groups that are known or likely to occur at a frequency
and at levels of public health concern:
Factors of Primary Consideration
• How many samples (number and percent) have detections > HRL in nationally
representative and other finished water occurrence data?
• How many systems (number and percent) have detections > HRL in nationally
representative and other finished water occurrence data?
• Is the geographic distribution of contaminant occurrence national, regional, or localized?
• In addition to the number of systems, what type of systems does the contaminant occur
in? Does the contaminant occur in large or small systems? Does the contaminant occur in
surface or groundwater systems?
• Are there significant uncertainties or limitations with the data and/or analyses, involving
(for example) the age of the dataset, the use of analytical methods that cannot quantify
occurrence at concentrations as low as the HRL, and/or representativeness of the data
(e.g., limited in scope to a particular region)?
Additional Factors of Consideration
• How many samples (number and percent) have detections > V2 HRL in the nationally
representative and other finished water occurrence data?
• How many systems (number and percent) have detections > V2 HRL in the nationally
representative and other finished water occurrence data?
• How many samples (number and percent) have detections > HRL and V2 HRL in the
ambient/source water occurrence data?
• How many monitoring sites (number and percent) have detections > HRL and V2 HRL in
the ambient/source water occurrence data?
• Are production and use trends for the contaminant increasing or decreasing?
• How many pounds are discharged annually to surface water and/or released to the
environment?
• Do the environmental fate and transport parameters indicate that the contaminant would
persist and/or be mobile in water?
• Is the contaminant introduced by water treatment processes that provide public health
benefits such that it is relevant to risk-balancing considerations?
• Are there additional uncertainties or limitations with the data and/or analyses that should
be considered?
Occurrence will be evaluated relative to V2 of the HRL (in addition to the full HRL) as a
conservative estimate of occurrence at or approaching levels of public health concern.
Occurrence analyses undertaken during Phase 2 will be examined, and additional analyses (e.g.,
more narrowly focused, or using more sophisticated methodologies) may be conducted during
Phase 3 to further inform an understanding of the contaminant's occurrence.
If the Agency finds that a contaminant is known to occur or there is a substantial
likelihood of occurrence at a frequency and levels of health concern in public water systems
informed by the factors listed above, then the Agency answers "yes" to the second statutory
criterion. Otherwise, the Agency answers "no" to the second statutory criterion.
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An important consideration in this evaluation is the detection limit (DL) and/or the
reporting level (RL), sometimes designated as a MRL, used in monitoring for drinking water
contaminants. The DL is the minimum concentration of a contaminant in water that can be
reliably differentiated from the signal arising from a blank (i.e., the contaminant can be
determined to be present). It may not be possible to achieve reliable quantitation at the DL. The
RL is a concentration at or above which results are reported by a laboratory or a study and is
generally a concentration at which reliable quantitation is possible. The MRL is the minimum
concentration that is required to be reported quantitatively in a study. The MRL is set at a value
that takes into account typical laboratory capabilities to reliably and cost-effectively detect and
quantify a compound. If the HRL is equal to or greater than the MRL, any occurrence at or above
the HRL can be reliably quantified and reported with confidence. If the HRL is less than the
MRL, any reported concentration (commonly called a "detection") is necessarily greater than the
HRL. Occurrence at concentrations that exceed the HRL but are below the MRL often go
unreported. A variety of approaches can be used to estimate the occurrence below the MRL,
including fitting an appropriate distribution model using the quantified occurrence data above the
MRL.
In the case of non-threshold carcinogens, if there is little to no occurrence above an MRL
that is greater than the HRL, and the MRL is within the 10"4 to 10"6 risk range, the Agency can
make a decision for the second statutory criterion as long as this limitation is noted and other
information/data are considered (e.g., contaminant manufacturing trends, trends in the amount
released to the environment, occurrence in ambient water, etc.).
E.7.3 Evaluation of Statutory Criterion #3 (Meaningful Opportunity)
For statutory criterion #3, the Administrator decides, in his or her sole judgement,
whether a drinking water regulation for a contaminant or group presents a meaningful
opportunity for health risk reduction for persons served by public water systems. The EPA
Administrator may consider factors such as the following when evaluating statutory criterion #3:
• What is the nature of the health effect(s) identified in statutory criterion #1 and are there
sensitive populations that may be affected (evaluated either qualitatively or
quantitatively)?
• Based on the occurrence information evaluated for statutory criterion #2, including the
number of systems potentially affected, what is the national population exposed or served
by systems with levels > HRL and V2 HRL?
• For non-carcinogens, are there other sources of exposure that should be considered (i.e.,
what is the relative source contribution from drinking water)?
• What is the geographic distribution of occurrence (e.g., local, regional, national)?
• Are there any uncertainties and/or limitations in the health and occurrence information or
analyses that should be considered?
• Are there any limiting considerations related to technology (e.g., treatment or analytical
methods)?
After evaluating these factors, if the Administrator determines that there is a meaningful
opportunity to reduce risk by regulating the contaminant or group in drinking water, then the
Agency will answer "yes" to the third statutory criterion.
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E.7.4 Making a Regulatory Determination Decision
If the Agency answers "yes" to all three statutory criteria, then the Agency makes a
positive preliminary determination. Additionally, after identifying compounds occurring at
frequencies and levels of public health concern, the Agency may initiate a systematic literature
review to identify new studies that may influence the derivation of an RfD and/or CSF. The list
of potentially relevant health effects studies that could affect the derivation of an RfD or CSF
identified through the systematic review process will be placed in the docket at the time of the
preliminary determination for public comment.
If after considering input provided during the public comment period, the Agency again
answers "yes" to all three statutory criteria, the Agency then makes a positive final determination
that regulation is necessary for a particular contaminant or group. After a positive determination
is finalized, the Agency has 24 months to publish a proposed MCLG and NPDWR and then 18
months to publish a final MCLG and promulgate a final NPDWR (SDWA section
1412(b)(1)(E)). (SDWA permits the Agency to extend the promulgation date by an additional
nine months if needed.) The regulatory determination process outlined in this document is
distinct from the analyses needed to develop an NPDWR. Thus, a decision to regulate is the
beginning of the Agency's regulatory development process, not the end.
If the Agency answers "no" to one or more of the three statutory criteria, then the Agency
considers making a "negative" determination that an NPDWR is not necessary for that
contaminant at this time. A determination not to regulate a contaminant is considered a final
Agency action and is subject to judicial review. The Agency may also elect to issue no
determination for a contaminant in Phase 3. For example, the Agency may find that additional
information is required to make a positive or negative regulatory determination or may decide to
evaluate the contaminant outside the Regulatory Determination process (e.g., together with
related regulated contaminants as part of the Six-Year Review process).
Only positive determinations and negative determinations count toward the statutory
requirement that five determinations be made each cycle.
If a negative determination or no determination is made for a contaminant, the Agency
may also decide to develop and publish a HA, a non-regulatory action. HAs provide
concentration values for drinking water contaminants at or below which adverse health effects
are not anticipated to occur over specific exposure durations (one-day, ten-days, several years,
and/or a lifetime). HAs serve as informal technical guidance to assist federal, state, and local
officials and managers of public or community water systems (CWSs) in protecting public health
when emergency spills or contamination situations occur.
While a negative determination is considered a final Agency action for this round of
regulatory determination, the contaminant may be relisted on a future CCL based on newly
available health and/or occurrence information.
See Exhibit E-8 for a summary of possible Regulatory Determination outcomes.
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Exhibit E-8: Regulatory Determination Outcomes
Positive
determination
• Positive Determination (Phase 3)
*
Outcome
- Affirrr stive determination for ;ill -.liree criteria
1
S
- Begin process to develop n drinking water regulation
1
~
3
~
* Negative Determination (Phase 3)
- Negative determination for any one of the three criteria
r*egalive
- Considered a final agency action
— Drinkingwater regulation not developed
determination
(one example)
- Health Advisory is a non-regulatory option
- New data can prompt inclusion in :he next or a futi re CCL
=
aiteomt
1
V
2
X
• No Regulatory Determination (Phase lr Zr 3)
3
X
- Insufficient data, or contaminant will be evaluated on a
separate timetable
- May be included on next CCL
- Health Advisory is a non-regulatory option
E.8 References Cited
United States Environmental Protection Agency (USEPA). 1991. Guidelines for Developmental
Toxicity Risk Assessment. EPA 600-FR-91-001.
USEPA. 1996. Guidelines for Reproductive Toxicity Risk Assessment. October. EPA630-R-96-
009.
USEPA. 1997. Announcement of the Draft Drinking Water Contaminant Candidate List; Notice.
Federal Register. Vol. 62, No. 193, p. 52194, October 6, 1997. Available on the Internet
at: https://federalregister.gOv/a/97-26433.
USEPA. 1998a. Announcement of the Drinking Water Contaminant Candidate List; Notice.
Federal Register. Vol. 63, No. 40, p. 10273. March 2, 1998. Available on the Internet at:
http s: //federalregi ster. gov/a/98-5313.
USEPA. 1998b. Guidelines for Neurotoxicity Risk Assessment. April. EPA 630-R-97-0.
USEPA. 2002a. Announcement of Preliminary Regulatory Determinations for Priority
Contaminants on the Drinking Water Contaminant Candidate List. Federal Register. Vol.
67, No. 106, p. 38222, June 3, 2002. Available on the Internet at:
https ://federalregi ster. gov/a/02-13 796.
USEPA. 2002b. A Review of the Reference Dose and Reference Concentration Processes.
December. EPA 630-P-02-002F.
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USEPA. 2003. Announcement of Regulatory Determinations for Priority Contaminants on the
Drinking Water Contaminant Candidate List. Federal Register. Vol. 68, No. 138, p.
42898. July 18, 2003. Available on the Internet at: https://federalregister.gOv/a/03-18151.
USEPA. 2004. Drinking Water Contaminant Candidate List 2; Notice. Federal Register. Vol. 69,
No. 64, p. 17406, April 2, 2004. Available on the Internet at:
https://federalregister.gOv/a/04-7416.
USEPA. 2005a. Drinking Water Contaminant Candidate List 2; Final Notice. Federal Register.
Vol. 70, No. 36, p. 9071. February 24, 2005. Available on the Internet at:
https://federalregister.gOv/a/05-3527.
USEPA. 2005b. Guidelines for Carcinogen Risk Assessment. EPA 630-P-03-001B. March 2005.
Available on the Internet at: http://www.epa.gov/ttn/atw/cancer guidelines final 3-25-
05.pdf.
USEPA. 2005c. Supplemental Guidance for Assessing Susceptibility to Early-life Exposure to
Carcinogens. EPA 630-R-03-003F. March 2005. Available on the Internet at:
http://www.epa.gov/ttn/atw/childrens supplement final.pdf.
USEPA. 2006. A Framework for Assessing Health Risks of Environmental Exposures to
Children. EPA 600-R-05-093F.
USEPA. 2007. Drinking Water: Regulatory Determinations Regarding Contaminants on the
Second Drinking Water Contaminant Candidate List—Preliminary Determinations.
Federal Register. Vol. 72, No. 83, p. 24016, May 1, 2007. Available on the Internet at:
http s: //federalregi ster. gov/a/E7-7539
USEPA. 2008a. Drinking Water: Regulatory Determinations Regarding Contaminants on the
Second Drinking Water Contaminant Candidate List. Federal Register. Vol. 73, No. 147,
p. 44251. July 30, 2008. Available on the Internet at: https://federalregister.gov/a/E8-
17463
USEPA. 2008b. Drinking Water Contaminant Candidate List 3—Draft Notice. Federal Register.
Vol. 73. No 35. p. 9628, February 21, 2008. Available on the Internet at:
https://federalregister.gOv/a/E8-3114
USEPA. 2008c. Drinking Water: Preliminary Regulatory Determination on Perchlorate. Federal
Register. Vol. 73, No. 198, p. 60262, October 10, 2008. Available on the Internet at:
https://federalregister.gOv/a/E8-24042.
USEPA. 2009a. Drinking Water Contaminant Candidate List 3 - Final. Federal Register. Vol.
74, No. 194, p. 51850. October 8, 2009. Available on the Internet at:
http s: //federalregi ster. gov/a/E9-24287.
USEPA. 2009b. Drinking Water: Perchlorate Supplemental Request for Comments. Federal
Register. Vol. 74, No. 159, p. 41883, August 19, 2009. Available on the Internet at:
https://federalregister.gOv/a/E9-19507.
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USEPA. 2009c. Drinking Water: Perchlorate Supplemental Request for Comments. Federal
Register. Vol. 74, No. 183, p. 48541, September 23, 2009. Available on the Internet at:
https://federalregister.gOv/a/E9-22927.
USEPA. 201 la. Drinking Water: Regulatory Determination on Perchlorate. Federal Register.
Vol. 76, No. 29, p. 7762, February 11, 2011. Available on the Internet at:
https ://federalregister. gov/a/2011 -2603.
USEPA. 201 lb. Exposure Factors Handbook. U.S. Environmental Protection Agency,
Washington, DC. EPA 600-R-09-052F.
USEPA. 201 lc. Recommended Use of Body Weight4 as the Default Method in Derivation of the
Oral Reference Dose. EPA 100-R11-0001.
USEPA. 2012. Benchmark Dose Technical Guidance Document. June. EPA 100-R-12-001.
USEPA. 2014a. Announcement of Preliminary Regulatory Determinations for Contaminants on
the Third Drinking Water Contaminant Candidate List. Federal Register. Vol. 79, No.
202, p. 62715, October 20, 2014.
USEPA. 2014b. Child-Specific Exposure Scenarios Examples. EPA 600-R-14-217F.
USEPA. 2014c. Guidance for Applying Quantitative Data to Develop Data-Derived
Extrapolation Factors for Interspecies and Intraspecies Extrapolation. September. EPA
R-14-002F
USEPA. 2015. Drinking Water Contaminant Candidate List 4—Draft. Federal Register. Vol. 80
No. 23, p 6076, February 4, 2015.
USEPA. 2016a. Drinking Water Contaminant Candidate List 4—Final. Federal Register. Vol. 81
No. 222, p 81099, November 17, 2016.
USEPA. 2016b. Announcement of Final Regulatory Determinations for Contaminants on the
Third Drinking Water Contaminant Candidate List. Federal Register. Vol. 81 No. 1, p.
13, January 4, 2016.
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