xvEPA
United States
Environmental Protection
Agency
Contaminant Occurrence Support
Document for Category 2
Contaminants for the Second Six-
Year Review of National Primary
Drinking Water Regulations
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Office of Water (4607M)
EPA-815-B-09-011
October 2009
www. epa.gov/safewater
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Disclaimer
This report is in support of the preliminary revise/take no action decisions for EPA's
second Six-Year Review of Existing Drinking Water Standards Federal Register Notice. This
report is intended to provide technical background for the second Six-Year Review.
This document is not a regulation itself, and it does not substitute for the Safe Drinking
Water Act (SDWA) or EPA's regulations. Mention of trade names or commercial products does
not constitute endorsement or recommendation for use.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Acknowledgements
EPA's Office of Ground Water and Drinking Water (OGWDW) conducted the national
assessments of regulated contaminant occurrence in public drinking water presented in this report
in support of the second Six-Year Review of National Primary Drinking Water Regulations. This
effort was directed by Ms. Karen Wirth and Mr. Rajiv Khera.
EPA would like to thank the many states, territories, and tribes and their staff who
contributed data sets and valuable advice during EPA's compilation and review of the
contaminant occurrence (compliance monitoring) data. Thank you also to the many public water
systems and their staff who conducted the monitoring that provided the extensive amount of
regulated contaminant occurrence data used in this report.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Executive Summary
This document provides occurrence-related background information on 47 regulated
drinking water contaminants in support of the Environmental Protection Agency's (EPA's) second
Six-Year Review of National Primary Drinking Water Regulations (the "second Six-Year
Review"). For the second Six-Year Review, these 47 regulated contaminants are referred to as the
"Category 2" contaminants. The "Category 1" contaminants (discussed in a separate report) are
those regulated contaminants with relatively high rates of occurrence at or near concentration
thresholds of concern, new or ongoing health effects assessments; and potential new laboratory
analytical capabilities. The Category 2 contaminants discussed in this report are the regulated
contaminants that meet some, but not all, of the occurrence, health effects, or laboratory analytical
factors defining the Category 1 contaminants. For example, some Category 2 contaminants might
exhibit moderately high occurrence nationally, but research on their health effects is still in
progress and has not yet concluded. A list of the 47 regulated contaminants assessed here is
included in this document's Table of Contents.
This support document is divided into contaminant-specific chapters. The individual
contaminant chapters include background information (regulatory history, general chemical
information, and environmental fate and behavior), use and environmental release information, an
overview of occurrence in ambient water, and national estimates of contaminant occurrence in
public drinking water systems.
The national drinking water occurrence estimates presented here are based on the data
contained in the National Compliance Monitoring Information Collection Request Dataset for the
Second Six-Year Review (the "Six Year Review-ICR Dataset"), which includes data collected
from 1998 to 2005. This is the largest and most comprehensive drinking water contaminant dataset
ever compiled by EPA's Drinking Water Program and includes 15 million records for 69 regulated
contaminants submitted by 47 states/primacy agencies (45 states plus Region 8 and Region 9
tribes). Using this dataset, a variety of occurrence estimates were generated to characterize the
national occurrence of regulated contaminants in public water systems (PWSs).
National occurrence estimates using the Six Year Review-ICR Dataset were generated
using a two-stage analytical approach. In the first stage (Stage 1 analysis) the data were reviewed
and quality-checked to ensure high quality and were then analyzed to generate simple, non-
parametric estimates of contaminant occurrence. The Stage 1 analysis, based on maximum sample
concentration values, is inherently conservative; it is designed not to underestimate occurrence and
is therefore protective of public health. Simple counts are made of the number of systems, and
populations served by those systems, with at least one sample analytical result (measured
contaminant concentration) above a specified concentration threshold. The second stage (Stage 2
analysis) is based on estimated system mean concentrations of contaminants. Because it uses
estimated mean concentrations rather than maximum sample concentrations, Stage 2 analysis is
less conservative than the Stage 1 analysis. The Stage 2 analysis also provides occurrence
assessments that may be more reflective of potential chronic exposure. Only the Stage 1 analyses
were conducted for the 47 contaminants assessed in this report.
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For the Stage 1 analyses, contaminant occurrence data were analyzed in several different
ways to more fully characterize national occurrence. One measure is the percentage of population-
served by systems nationwide that reported at least one sample analytical result greater than a
contaminant's Maximum Contaminant Level (MCL) concentration, the drinking water contaminant
standard. This provides a preliminary estimate of potential exposure to a drinking water
contaminant at concentrations of health concerns. Based on this measure, the range of occurrence
(highest to lowest) and the top five occurring contaminants were estimated, grouped by chemical
(i.e., inorganic chemicals [lOCs], synthetic organic chemicals [SOCs], volatile organic compounds
[VOCs]), and are summarized below. The results for the four regulated radionuclides assessed are
also summarized below.
IOC occurrence ranged from a high of nitrate with 7.310% (of the total population-served
by systems reporting at least one detection greater than the nitrate MCL concentration) to a low of
barium with 0.092% (relative to the barium MCL concentration). The top five occurring lOCs
based on this Stage 1 measure are nitrate (7.310%), nitrite (4.840%), antimony (1.505%), beryllium
(1.505%), and arsenic (1.240%). (Note: The percentage of arsenic is based on the former MCL
concentration of 0.05 mg/L that was in effect when the compliance monitoring data, used for the
second Six-Year Review analysis, were collected. Additional analyses were conducted relative to
the current arsenic MCL concentration of 0.01 mg/L.) These detections represent single detections
and are not representative of MCL violations.
SOC occurrence ranged from a high of di(2-ethylhexyl)phthalate with 6.397% (of the total
population-served by PWSs reporting at least one detection greater than the MCL concentration) to
a low of 0.000% for diquat, endrin, glyphosate, methoxychlor, picloram, and silvex. The top five
occurring SOCs based on this Stage 1 measure are di(2-ethylhexyl)phthalate (6.397%), atrazine
(1.551%), ethylene dibromide (1.201%), benzo(a)pyrene (0.117%), and polychlorinated biphenyls
(0.101%). These detections represent single detections and are not representative of MCL
violations. Note: The high occurrence of di(2-ethylhexyl)phthalate could be due, in part, to sample
contamination from older generation laboratory and field sampling equipment made of plastics that
contained (and sometimes released) phthalates.
VOC occurrence ranged from a high of 1,1-dichloroethylene with 2.517% (of the total
population-served by PWSs reporting at least one detection greater than the 1,1-dichloroethylene
MCL concentration) to a low of 0.000% for 1,2-dichlorobenzene, trans-1,2-dichloroethylene,
ethylbenzene, monochlorobenzene, 1,2,4-trichlorobenzene, and 1,1,1-trichloroethane. The top four
occurring VOCs based on this measure are 1,1-dichloroethylene (2.517%), cis-1,2-
dichloroethylene (0.074%), 1,4-dichlorobenzene (0.044%), and styrene (0.001%). These detections
represent single detections and are not representative of MCL violations.
The national occurrence of four radionuclides was also assessed using the same Stage 1
analysis that provides a preliminary estimate of exposure. Based on the measure of the percent of
total population-served by PWSs reporting at least one detection greater than each contaminant's
MCL concentration, the highest occurring radionuclide is uranium (11.884%). These detections
represent single detections and are not representative of MCL violations.
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These IOC, SOC, VOC, and radionuclide occurrence measures (based on the percentage of
population-served) are quite similar to the findings for measures reflecting occurrence for PWSs.
Additional occurrence details are presented in the report such as occurrence estimates by source
water type and estimates for the actual numbers of PWSs and population-served numbers (in
addition to the percentages presented above).
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Contents
Disclaimer iii
Acknowledgements v
Executive Summary vii
Contents xi
Abbreviations xiii
1 Introduction 1-1
1.1 Purpose and Scope 1-1
1.2 The Six-Year Review Process 1-2
1.3 Data Sources 1-2
1.3.1 Agency for Toxic Substances and Disease Registry 1-3
1.3.2 Extension Toxicology Network 1-4
1.3.3 Hazardous Substances Data Bank 1-4
1.3.4 United States Geological Survey Pesticide Use Maps 1-4
1.3.5 Toxic Substances Control Act Chemical Substance Inventory 1-5
1.3.6 Toxics Release Inventory 1-5
1.3.7 National Water Quality Assessment 1-6
1.3.8 National Compliance Monitoring Information Collection Request (ICR) Dataset for
the Second Six-Year Review (Six-Year Review-ICR Dataset) 1-8
1.4 Occurrence Analysis 1-12
1.5 References 1-13
2 Alachlor 2-1
3 Alpha Particles 3-1
4 Antimony 4-1
5 Arsenic 5-1
6 Asbestos 6-1
7 Atrazine 7-1
8 Barium 8-1
9 Benzo(a)pyrene 9-1
10 Beryllium 10-1
11 Beta Particles 11-1
12 Cadmium 12-1
13 Chromium (Total) 13-1
14 Cyanide 14-1
15 Dalapon 15-1
16 Di(2-ethylhexyl)adipate (DEHA) 16-1
17 Di(2-ethylhexyl)phthalate (DEHP) 17-1
18 1,2-Dichlorobenzene 18-1
19 1,4-Dichlorobenzene 19-1
20 1,1-Dichloroethylene 20-1
21 cis-l,2-Dichloroethylene 21-1
22 trans-1,2-Dichloroethylene 22-1
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23 Dinoseb 23-1
24 Diquat 24-1
25 Endrin 25-1
26 Ethylbenzene 26-1
27 Ethylene Dibromide (EDB) 27-1
28 Fluoride 28-1
29 Glyphosate 29-1
30 Lindane (gamma-Hexachlorocyclohexane) 30-1
31 Mercury (Inorganic) 31-1
32 Methoxychlor 32-1
33 Monochlorobenzene (Chlorobenzene) 33-1
34 Nitrate (as N) 34-1
35 Nitrite (as N) 35-1
36 Pentachlorophenol 36-1
37 Picloram 37-1
38 Polychlorinated Biphenyls (PCBs) 38-1
39 Combined Radium-226 and Radium-228 39-1
40 Selenium 40-1
41 Simazine 41-1
42 Styrene 42-1
43 2,3,7,8-TCDD (Dioxin) 43-1
44 Thallium 44-1
45 1,2,4-Tri chlorobenzene 45-1
46 1,1,1-Trichloroethane 46-1
47 2,4,5-Trichlorophenoxypropionic Acid (Silvex) 47-1
48 Uranium 48-1
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Abbreviations
ATSDR Agency for Toxic Substances and Disease Registry
CDD Chlorinated Dibenzo-p-dioxins
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
Cr(0) Chromium element
Cr(m) Chromium valence state in
Cr(VI) Chromium valence state VI or hexavalent Chromium
CWS Community Water System
1,4-DCB 1,4,-Dichlorobenzene
DDT Di chl orodiphenyltri chl oroethane
1,2-DCE 1,2-Dichloroethylene
DEHA Di(2-ethylhexyl)adipate
DEHP Di(2-ethylhexyl)phthalate
DWEL Drinking Water Equivalent Level
EDB Ethylene Dibromide
EPA Environmental Protection Agency (United States)
EPCRA Emergency Planning and Community Right-to-Know Act
EXTOXNET Extension TOXicology NET work
FR Federal Register
HCH Hexachlorocyclohexane
HSDB Hazardous Substances Data Bank
ICR Information Collection Request
IOC Inorganic Chemical
IUR Inventory Update Reporting
LCR Lead and Copper Rule
LOAEL Lowest Observed Adverse Effect Level
MCL Maximum Contaminant Level
MCLG Maximum Contaminant Level Goal
MFL million fibers per liter
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mg milligram
mg/kg/day milligrams per kilogram per day
mg/L milligrams per liter
MRL Minimum Reporting Level
Mrem/yr Millirems per year
NAWQA National Water Quality Assessment
ND Not Detected
NLM National Library of Medicine
NPDWR National Primary Drinking Water Regulation(s)
NTNCWS Non-Transient Non-Community Water System
OGWDW Office of Ground Water and Drinking Water
PAH Polycyclic Aromatic Hydrocarbon
PCB Polychlorinated Biphenyl
ppb parts per billion
ppm parts per million
PVC Polyvinyl chloride
PWS Public Water System
QA/QC Quality Assurance / Quality Control
RCRA Resource Conservation and Recovery Act
RfD Reference Dose
RED Reregi strati on Eligibility Decision
RL Reporting Limit
RSC Relative Source Contribution
SARA Superfund Amendments and Reauthorization Act
SDWA Safe Drinking Water Act
SMCL Secondary Maximum Contaminant Level
SOC Synthetic Organic Chemical
SRP Scientific Review Panel
1,2,4-TCB 1,2,4-Trichlorobenzene
TNCWS Transient Non-Community Water Systems
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TOXNET TOXicology Data NET work
TRI Toxics Release Inventory
TSCA Toxic Substances Control Act
USEPA United States Environmental Protection Agency
USGS United States Geological Survey
VOC Volatile Organic Compound
jig micrograms
|ig/kg/day micrograms per kilogram per day
|ig/kg/year micrograms per kilogram per year
|ig/L microgram per liter
USER United States Bureau of Reclamation
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1 Introduction
1.1 Purpose and Scope
The Environmental Protection Agency (EPA) performed a detailed review of compliance
monitoring data of 69 National Primary Drinking Water Regulations (NPDWR) in support of the
second Six-Year Review. This document summarizes contaminant occurrence information for 47
of those regulated contaminants. The remaining 22 contaminants represent the "Category 1"
contaminants which are those contaminants with relatively high levels of occurrence at or near
concentration thresholds of concern, new or ongoing health effects assessments, and new
potential laboratory methods capabilities. This report's focus is on the 47 contaminants classified
as "Category 2" contaminants (contaminants that meet some, but not all, of the occurrence,
health effects, or laboratory methods criteria defining the Category 1 contaminants).. The
occurrence estimates reported are based on the National Compliance Monitoring Information
Collection Request Dataset for the Second Six-Year Review (the "Six Year Review-ICR
Dataset"). The Six Year Review-ICR Dataset contains compliance monitoring data from 1998 to
2005. This dataset is the largest and most comprehensive compliance monitoring dataset ever
compiled by EPA's Drinking Water Program, and includes 15 million records for 69 regulated
contaminants submitted by 47 states/primacy agencies (45 states plus Region 8 and Region 9
tribes). Using this dataset, an analytical approach was employed to estimate a variety of
occurrence measures to characterize the national occurrence of regulated contaminants in public
water systems (PWSs) to support the second Six-Year Review process.
This support document is organized so that information on one contaminant is presented
in each chapter. This introductory Chapter 1 presents general background information applicable
to all contaminants. This chapter includes a description of the information and data sources used
for this assessment as well as the analytical approach used to estimate national contaminant
occurrence from the compliance monitoring data. To provide regulatory context, the Six-Year
Review process is also briefly described.
Chapters 2 through 48 present information specific to each of the Category 2 regulated
drinking water contaminants that EPA is reviewing under this second Six-Year Review. The
Table of Contents provides a list of the Category 2 contaminants included in the chapters in this
report. (The contaminant chapters are arranged alphabetically.)
Each chapter includes a brief presentation of the contaminant's uses, production,
environmental releases, and occurrence in ambient water. Detailed information is then provided
for a contaminant's occurrence in drinking water and related information is given regarding
preliminary exposure estimates (estimates of the populations-served by PWSs found to have
contaminants occurring in their drinking water samples). USEPA (2009a) provides similar
information for the Category 1 contaminants. For a complete description and presentation of all
estimates of contaminant occurrence generated in support of the second Six-Year Review (for
Category 1 and 2 contaminants), please refer to the accompanying report The Analysis of the
Regulated Contaminant Occurrence Data from Public Water Systems in Support of the Second
Six-Year Review of National Primary Drinking Water Regulations (USEPA, 2009b).
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1.2 The Six-Year Review Process
EPA's Office of Ground Water and Drinking Water (OGWDW) is responsible for
implementing the provisions of the Safe Drinking Water Act (SOW A). The 1996 SDWA
amendments require EPA to review existing NPDWRs no less often than every six years and, if
appropriate, revise them. As long as an NPDWR revision maintains or provides for greater
protection of public health, the SDWA 1996 amendments give the EPA Administrator discretion
to determine if revision is appropriate. EPA believes any revision must continue to meet the basic
statutory requirements of the SDWA (e.g., generally setting the maximum contaminant level
(MCL) as close to the maximum contaminant level goal (MCLG) as is feasible). EPA also
believes any revision must present significant opportunities to improve the level of public health
protection and/or to achieve cost savings while maintaining or improving the level of public
health protection. The Six-Year Review process evaluates the contaminant occurrence, health
effects, analytical methodology, and treatment technology factors relevant to this formal re-
assessment of each NPDWR. This support document presents information relevant to
contaminant occurrence.
During the first Six-Year Review, EPA developed a protocol document — EPA Protocol
for the Review of Existing National Primary Drinking Water Regulations (USEPA, 2003 a) and
updated USEPA (2009c) for the current review cycle — to describe the process and strategy for
review that EPA will use to meet its statutory requirement. To most efficiently utilize limited
resources, EPA conducts a series of analyses at the beginning of each Six-Year Review cycle,
intended to target those NPDWRs that are the most appropriate candidates for revision. EPA uses
available, scientifically sound data to make decisions regarding whether or not to revise a
regulation. EPA reviews the following key information to make decisions regarding regulatory
changes: current health risk assessments, technology assessments (including reviews of
laboratory analytical methods and treatment techniques), and occurrence and exposure
assessments.
EPA will consider regulatory revisions based on the various components of each primary
drinking water regulation, including possible changes to MCLs, MCLGs, treatment techniques,
analytical method and treatment capabilities. In some cases, EPA may also consider revisions to
monitoring or system reporting requirements as part of the Six-Year Review; however, in most
cases, these types of revisions will be considered through other vehicles. For any NPDWR that is
a potential candidate for revision based on its review, EPA will also take economic
considerations into account before making its "revise/no action" decision. Moreover, EPA will
apply basic risk management principles to determine whether these candidate regulations warrant
regulatory revision to ensure that any revision will present a meaningful opportunity to improve
the level of public health protection and/or present a meaningful opportunity for cost savings
while maintaining, or improving, the level of public health protection.
1.3 Data Sources
Several data sources were used in this report to provide information on contaminant use,
production, occurrence, and potential exposure. The primary data source used for contaminant
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background and use information was the Agency for Toxic Substances and Disease Registry
(ATSDR). The Toxics Release Inventory (TRI) provided data on contaminant releases.
Production data were obtained from the Toxic Substances Control Act (TSCA) Chemical
Substance Inventory. Information on contaminant occurrence in ambient water was primarily
derived from the United States Geological Survey (USGS) National Water Quality Assessment
(NAWQA) Program. Drinking water contaminant occurrence analyses are generated using state
drinking water compliance monitoring contaminant occurrence data that EPA obtained from 45
states and 2 Primacy Entities (the "Six-Year Review-ICR Dataset"). This dataset is the largest
compliance monitoring data set compiled and analyzed to date by EPA's Drinking Water
Program. These primary data sources are described in detail in the subsequent sections of this
chapter. The information from and the analyses generated using these data sources are
summarized in the contaminant-specific chapters of this report.
1.3.1 Agency for Toxic Substances and Disease Registry
In 1980, Congress created the ATSDR to implement the health-related sections of laws
that protect the public from hazardous wastes and environmental spills of hazardous substances
(ATSDR, 2001). The Comprehensive Environmental Response, Compensation, and Liability Act
of 1980 (CERCLA), commonly known as the "Superfund" Act, provided the Congressional
mandate to remove or clean up abandoned and inactive hazardous waste sites and to provide
federal assistance in toxic emergencies. As the lead agency within the Public Health Service for
implementing the health-related provisions of CERCLA, ATSDR is charged under the Superfund
Act to assess the presence and nature of health hazards at specific Superfund sites, to help
prevent or reduce further exposure and the illnesses that result from such exposures, and to
expand the knowledge base about health effects from exposure to hazardous substances
(ATSDR, 2001).
In the 1984 amendments to the Resource Conservation and Recovery Act of 1976
(RCRA), which provides for the management of legitimate hazardous waste storage or
destruction facilities, ATSDR was authorized to conduct public health assessments at these sites,
when requested by EPA, states, or individuals. ATSDR was also authorized to assist EPA in
determining which substances should be regulated and the levels at which substances may pose a
threat to human health (ATSDR, 2001).
With the passage of the Superfund Amendments and Reauthorization Act of 1986
(SARA), ATSDR received additional responsibilities in environmental public health. This act
broadened ATSDR's responsibilities in the areas of public health assessments, establishment and
maintenance of toxicological databases, information dissemination, and medical education
(ATSDR, 2001).
ATSDR issues Toxicological Profiles for over 250 substances, including 32 of the 47
contaminants discussed in this report. These profiles contain exhaustive reports on the
substances' health effects, chemical and physical properties, use and production, potential for
human exposure, and analytical methods. Whenever available, ATSDR was used as a primary
source in this report for contaminant background and use information.
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1.3.2 Extension Toxicology Network
The Extension TOXicology NET work (EXTOXNET) is a cooperative effort of
University of California-Davis, Oregon State University, Michigan State University, Cornell
University, and the University of Idaho (EXTOXNET, 2008). Primary files are maintained and
archived at Oregon State University. The EXTOXNET InfoBase provides a variety of
information about pesticide toxicology and environmental chemistry. These include: discussions
of toxicological issues of concern; toxicology newsletters; other resources for toxicology
information; toxicology fact sheets; Pesticide Information Profiles; and Toxicology Information
Briefs. Pesticide Information Profiles were used to provide background information for six of the
Category 2 contaminants. Pesticide Information Profiles are not based on an exhaustive literature
search. The information does not in any way replace or supersede the information on the
pesticide product labeling or other regulatory requirements.
1.3.3 Hazardous Substances Data Bank
The Hazardous Substances Data Bank (HSDB) is a toxicology data file on the National
Library of Medicine's (NLM) Toxicology Data Network (TOXNET®). It focuses on the
toxicology of potentially hazardous chemicals and also includes information on human exposure,
industrial hygiene, emergency handling procedures, environmental fate, regulatory requirements,
and related areas. All data are referenced and derived from a core set of books, government
documents, technical reports and selected primary journal literature. HSDB is peer-reviewed by
the Scientific Review Panel (SRP), a committee of experts in the major subject areas within the
data bank's scope. HSDB is organized into individual chemical records for over 4,500
compounds, five of which are Category 2 contaminants discussed in this report (HSDB, 2006).
These data were used to provide background information for some of the Category 2
contaminants.
1.3.4 United States Geological Survey Pesticide Use Maps
The USGS has produced maps of pesticide use for 244 compounds used in United States
crop production, 6 of which are Category 2 contaminants discussed in this report. 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 maps
presented in this report were created by the USGS using state-level estimates of pesticide use
rates for individual crops that were compiled by the CropLife Foundation, Crop Protection
Research Institute based on information collected during 1999 through 2004, combined with
county-level data on harvested crop acreage obtained from the 2002 Census of Agriculture. The
maps do not represent a specific year, but rather show typical use patterns (i.e., average annual
pesticide use) over the five year period of 1999 through 2004. Use intensity rates are expressed as
the pounds applied per square mile of mapped agricultural land in a county (USGS, 2007).
USGS (2007) notes several key limitations of the data used to produce these maps. For
instance, the estimates of applied pesticides are averaged at the state-level, while the maps
extrapolate to the county-level by using county crop acreages from the Census of Agriculture.
Consequently, the maps do not truly represent the local variability of cropping and management
practices found within many states. Furthermore, the 2002 Census of Agriculture may not have
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represented all crop acreage, nor included all types of pasture. The maps are not intended for
making local-scale estimates of pesticide use, such as estimates at the county-level (USGS,
2007).
1.3.5 Toxic Substances Control Act Chemical Substance Inventory
Information on chemicals manufactured in or imported into the United States and listed
on the TSCA Chemical Substance Inventory is collected periodically by EPA. This collection
commenced following the promulgation of the Inventory Update Reporting (IUR) regulation in
1986. The 1986 regulation required chemical manufacturers and importers to report to EPA every
four years the identity of, and basic manufacturing information for, chemical substances
manufactured and imported annually in quantities of 10,000 pounds or more (USEPA, 2003b).
Under the TSCA, companies that manufacture or import chemicals may be required to
report information about these chemicals including, the identity of the chemicals, the amounts
manufactured or processed, certain details about their manufacture, and other data. This
information is stored in EPA's TSCA Chemical Substance Inventory Update System and is used
by EPA and other government agencies to identify potential use and exposure scenarios so that
they may protect human health and the environment (USEPA, 2003b).
EPA requires that chemical manufacturers periodically update their information in the
TSCA Chemical Substance Inventory because the chemicals used in the United States may
change and the quantity manufactured and industrial, commercial, and consumer uses of a
chemical may change. In order to accomplish this update, EPA periodically holds an Inventory
Update Reporting cycle. Inventory data are currently available for years 1986, 1990, 1994, 1998,
and 2002. TSCA Inventory data are available for 25 of the 47 contaminants discussed in this
report (USEPA, 2003b).
1.3.6 Toxics Release Inventory
EPA established the 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 the states annual information on toxic chemical releases from facilities that
meet reporting criteria. This reported information is maintained in a database accessible through
TRI Explorer (http://www.epa.gov/triexplorer). 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, 2002 and
2003c). Today, TRI includes information on releases of nearly 650 chemicals (including 33 of
the 47 contaminants discussed in this report).
Although TRI can provide a general idea of release trends, it has limitations. For
example, 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 or use more than 10,000 pounds
of a substance. Reporting requirements have changed over time (e.g., reporting thresholds have
decreased); this creates the potential for misleading data trends over time (USEPA, 1996). TRI
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data are meant to reflect releases and should not be used to estimate general public exposure to a
chemical (USEPA, 2002).
1.3.7 National Water Quality Assessment
Lakes, rivers, and aquifers are the sources of most drinking water. The USGS NAWQA
program is a national-scale assessment of the occurrence of contaminants in surface and ground
water. Monitoring contaminant occurrence in these ambient waters provides information for the
potential for contaminants to adversely affect drinking water supplies and drinking water.
The USGS instituted the NAWQA program in 1992 to examine ambient water quality
status and trends in the United States. The NAWQA program is designed to apply nationally
consistent methods to provide a consistent basis for comparisons among study basins across the
country and over time. These occurrence assessments serve to facilitate interpretation of natural
and anthropogenic factors affecting national water quality. Data are available from the NAWQA
program for 29 of the Category 2 contaminants. For more detailed information on the NAWQA
program design and implementation, please refer to Leahy and Thompson (1994) and Hamilton
et al. (2004).
The NAWQA program conducts monitoring and water quality assessments in significant
watersheds and aquifers referred to as "study units." The program's sampling approach is not
"statistically" designed (i.e., it does not involve random sampling), but it provides a
representative view of the nation's waters in its coverage and scope. Together, the 51 study units
monitored between 1992 and 2001 include the aquifers and watersheds that supply more than
60% of the nation's drinking water and water used for agriculture and industry. The NAWQA
program monitors the occurrence of chemicals such as pesticides, nutrients, volatile organic
compounds (VOCs), trace elements, and radionuclides, and the condition of aquatic habitats and
fish, insects, and algal communities (NRC, 2002; Hamilton et al., 2004). NAWQA has collected
data from over 6,400 surface water and 7,000 ground water sampling points.
Monitoring of study units occurs in stages. Between 1992 and 2001, approximately one-
third of the study units at a time were studied intensively for a period of three to five years,
alternating with a period of less intensive research and monitoring that lasted between five and
seven years. Thus, all participating study units rotated through intensive assessment in a ten-year
cycle (Leahy and Thompson, 1994). The first ten-year cycle was designated Cycle 1. Summary
reports are available for the 51 study units that underwent intensive monitoring in Cycle 1
(USGS, 2001). Cycle 2 monitoring is scheduled to proceed in 42 study units from 2002 to 2012
(Hamilton et al., 2004).
Pesticide National Synthesis Project
The NAWQA Pesticide National Synthesis Project is a national-scale assessment of the
occurrence and behavior of pesticides in streams and ground water of the United States and the
potential for pesticides to adversely affect drinking water supplies or aquatic ecosystems.
Results from the most recent Pesticide National Synthesis analysis, based on complete
Cycle 1 (1992-2001) data from NAWQA study units, are posted on the NAWQA Pesticide
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National Synthesis website (Gilliom et al., 2007). Data for surface water and ground water 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
ground water), and undeveloped. The National Synthesis analysis for pesticides 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 fewer 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. In
the National Synthesis analysis, the data were time-weighted to provide an estimate of the annual
frequency of detection and occurrence at a given concentration (Gilliom et al., 2007). For
instance, the detection frequency can be thought of as the percent of the year in which detections
are found at a typical site in this land use category and the 95th percentile concentration can be
thought of as a concentration that is not exceeded for 95% of the year at a typical site in this land-
use category.
The Pesticide National Synthesis only analyzed ground water data from wells; data from
springs and agricultural tile drains were not included. The sampling regimen used for wells was
different than that for surface water. 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.
EPA Summary Analysis of NAWQA Study Unit Monitoring Results
Whereas the NAWQA program often uses the most representative data for a site to
calculate summary statistics, EPA, with the cooperation of USGS, has performed a summary
analysis of all Cycle 1 water monitoring data from all study units (1992 to 2001) for many of the
regulated contaminants. EPA's analysis of the NAWQA data is analogous to the simple, straight-
forward "Stage 1" analysis the agency performed on drinking water data from PWS compliance
monitoring. That is, all the occurrence data for a particular contaminant were compiled and
analyzed using non-parametric methods to yield simple summary statistics to characterize
contaminant occurrence.
All surface water data were included in the EPA summary analysis. For ground water, all
well data were used; however, as with the USGS National Pesticide Synthesis, data from springs
and drains were excluded. For each contaminant, EPA calculated detection frequencies simply as
the percentage of samples and the percentage of sites with at least one detection. (A detection is
an analytical result equal to or greater than the reporting limit.) EPA used USGS data without
any censoring or weighting. From samples with detections a number of descriptive statistics were
also calculated, including the minimum, median, 95th percentile, 99th percentile, and maximum
concentrations. Reporting limits varied over time during the NAWQA program. The highest
reporting limit used for each contaminant is presented with the results of the analysis. Note that
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because reporting limits varied, the minimum concentration reported as a detection can be lower
than the highest reporting limit.
1.3.8 National Compliance Monitoring Information Collection Request (ICR) Datasetfor
the Second Six-Year Review (Six-Year Review-ICR Dataset)
Because there existed no national database of complete public drinking water compliance
monitoring data (all public drinking water contaminant sample results for analytical detections
and non-detections), EPA conducted a voluntary data call-in for states' compliance monitoring
records. These compliance monitoring data are the contaminant occurrence data collected under
the SDWA as part of the program to maximize compliance with federal public drinking water
standards. These data are collected by public water systems and reported to the states. EPA
received compliance monitoring data from a total of 51 states/primacy agencies: 46 states,
American Samoa, Washington, D.C., Region 8 tribes, Region 9 tribes, and the Navajo Nation.1
Through extensive data management efforts, quality assurance evaluations, and communications
with state/primacy agency data management staff, EPA established the Six-Year Review-ICR
Dataset. This high quality, national contaminant occurrence database consists of data from 47
states/primacy agencies (see Exhibit 1-1 below). The data received from American Samoa,
Washington, D.C., and the Navajo Nation could not be included in the second Six-Year Review
data analyses because those data sets were in significantly different formats. The data from
Kansas were received after the data assessment and quality assurance measures were completed
and were not able to be included in this occurrence analysis.
1 Upon request, Regions 8 and 9 provided a crosswalk table that listed the state in which each tribal water system was
located. All analyses conducted at the state-level (e.g., maps illustrating the geographic distribution of occurrence)
present the tribal systems' data along with the state in which they are located.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 1-1. States with Compliance Monitoring Data Included in the Six-Year
Review-ICR Dataset
IB Amcricnn Samoa
D District of Columbia
[ I (ilium
n Northern Mariana I-:]!iml'-:
D Puerto Kko
• R*.aioH B Tribes
• Region Q Navajn Nation
• Region 9 Tribes.
D Virgin Islands
stii
Data available but itot used
3) Data not available
The contaminant occurrence data from these 47 states/primacy agencies (45 states plus
Region 8 Tribes and Region 9 Tribes) comprise more than 15 million analytical records from
approximately 132,000 public water systems. Approximately 254 million people are served by
these public water systems nationally. The Six-Year Review-ICR Dataset is the largest, most
comprehensive set of compliance monitoring data ever used by EPA's Drinking Water Program.
Data quality, completeness, and representativeness are key considerations for the dataset.
Given the intended use of this national dataset as well as the size, scope, and variety of formats
of the constituent data sets received from the states, EPA conducted extensive data management
and quality assurance/quality control (QA/QC) assessments on the data to be included in the Six-
Year Review-ICR Dataset. For a review of the completeness and representativeness of the data
set, refer to USEPA (2009b). USEPA (2009b) also presents details of the tasks conducted for
data management (establishing consistent formats across the numerous state data sets, setting
uniform analytical results units, addressing non-numerical non-detection values, etc.) and data
quality checks (addressing incorrect analytical units, outlier values, etc.). Exhibit 1-2 summarizes
the Six-Year Review-ICR data for each contaminant used to generate the occurrence estimates
presented in this report.
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Exhibit 1-2. Overview of the Contaminant Occurrence Data in the Six-Year
Review-ICR Data Set for the Category 2 Contaminants
Contaminant
(MCL)
Number
of States
with Data
Total
Number of
Records
Total
Number of
Systems
Total
Population-
Served by
Systems
MRL
Inorganic Chemicals (lOCs)
Antimony
(0.006 mg/L)
Arsenic1
(0.05 mg/L)
Asbestos
(7 mf/L)
Barium
(2 mg/L)
Beryllium
(0.004 mg/L)
Cadmium
(0.005 mg/L)
Chromium (Total)
(0.1 mg/L)
Cyanide
(0.2 mg/L)
Fluoride
(4 mg/L)
Mercury (Inorganic)
(0.002 mg/L)
Nitrate (as N)
(10 mg/L)
Nitrite (as N)
(1 mg/L)
Selenium
(0.05 mg/L)
Thallium
(0.002 mg/L)
45
45
38
45
45
45
45
44
45
45
44
44
45
45
185,986
224,035
18,181
183,118
183,575
181,667
185,952
120,368
333,211
181,629
1,052,487
397,175
181,684
185,047
49,016
49,473
8,278
49,125
48,021
48,920
48,908
32,067
48,600
48,859
119,537
86,313
48,925
48,925
223,251,662
230,393,228
85,161,934
229,775,707
221,383,819
229,685,370
229,628,430
162,458,600
233,569,199
229,853,379
229,508,036
207,984,813
229,863,411
223,324,845
0.001 mg/L
0.005 mg/L
0.2 MFL
0.1 mg/L
0.001 mg/L
0.001 mg/L
0.01 mg/L
0.005 mg/L
0.1 mg/L
0.0002 mg/L
0.1 mg/L
0.1 mg/L
0.005 mg/L
0.0005 mg/L
Synthetic Organic Chemicals (SOCs)2
Alachlor
(2 M9/L)
Atrazine
(3 ug/L)
Benzo(a)pyrene
(0.2 ug/L)
Dalapon
(200 ug/L)
Di(2-ethylhexyl)adipate (DEHA)
(400 ug/L)
Di(2-ethylhexyl)phthalate (DEHP)
(6 ug/L)
Dinoseb
(7 ug/L)
Diquat
(20 ug/L)
Endrin
(2 ug/L)
Ethylene Dibromide (EDB)
(0.05 ug/L)
Glyphosate
(700 ug/L)
44
44
43
42
43
42
43
38
44
43
42
155,989
161,690
119,871
112,423
121,792
120,846
121,896
55,634
134,336
218,797
58,174
36,845
37,215
28,578
28,387
28,902
27,667
32,713
15,595
32,783
36,215
16,351
197,311,966
200,372,590
184,144,163
178,186,111
184,134,674
179,948,572
182,919,390
120,622,647
184,043,162
188,153,915
116,276,011
0.2 ug/L
0.1 ug/L
0.02 ug/L
1 ug/L
0.02 ug/L
0.6 ug/L
0.2 ug/L
2 ug/L
0.01 ug/L
0.01 ug/L
6 ug/L
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Contaminant
(MCL)
Lindane (gamma-
Hexachlorocyclohexane) (0.2 ug/L)
Methoxychlor
(40 Mg/L)
Pentachlorophenol
(1 ug/L)
Picloram
(500 |jg/L)
Polychlorinated Biphenyls (PCBs)
(0.5 Mg/L)
Simazine
(4 ug/L)
2,3,7,8-TCDD (Dioxin)
(0.00003 |jg/L)
2,4,5-Trichlorophenoxypropionc Acid
(Silvex) (50 |jg/L)
Number
of States
with Data
44
44
43
43
34
44
27
43
Total
Number of
Records
135,585
137,068
136,475
121,920
67,216
158,256
11,076
122,713
Total
Number of
Systems
33,265
33,421
34,339
32,910
18,393
36,830
2,383
32,887
Total
Population-
Served by
Systems
187,258,935
187,636,119
190,507,709
186,386,430
124,114,208
196,986,505
52,854,445
183,000,768
MRL
0.02 ug/L
0.1 ug/L
0.04 ug/L
0.1 ug/L
0.1 ug/L
0.07 ug/L
0.000005 ug/L
0.2 ug/L
Volatile Organic Compounds (VOCs)
1,2-Dichlorobenzene
(600 |jg/L)
1,4-Dichlorobenzene
(75 Mg/L)
1,1-Dichloroethylene
(7 Mg/L)
cis-1 ,2-Dichloroethylene
(70 Mg/L)
trans-1 ,2-Dichloroethylene
(100 ug/L)
Ethylbenzene
(700 |jg/L)
Monochlorobenzene (Chlorobenzene)
(100 ug/L)
Styrene
(100|jg/L)
1 ,2,4-Trichlorobenzene
(70 ug/L)
1,1,1 -Trichloroethane
(200 |jg/L)
45
44
45
44
44
45
44
45
45
45
372,946
370,698
378,630
373,316
371,258
374,141
370,519
372,269
371,132
374,950
50,422
49,969
50,425
50,314
50,319
50,447
50,311
50,421
50,135
50,440
226,929,816
224,476,625
226,909,664
225,615,734
225,611,137
226,939,375
225,627,782
226,933,636
226,842,102
226,931,546
0.5 ug/L
0.5 ug/L
0.5 ug/L
0.5 ug/L
0.5 ug/L
0.5 ug/L
0.5 ug/L
0.5 ug/L
0.5 ug/L
0.5 ug/L
Radiological Contaminants
Alpha Particles
(15pCi/L)
Beta Particles
(screening level = 50 pCi/L)
Combined Radium-226 & -228
(original Radionuclides rule)
(5 pCi/L) 3
Combined Radium-226 & -228
(revised Radionuclides rule)
(5 pCi/L) 3
Uranium
(30 ug/L)
35
34
35
33
33
73,002
59,983
18,452
18,050
41,581
18,653
14,231
6,884
3,893
5,921
121,170,400
120,274,924
47,422,440
41,426,437
70,631,392
1 pCi/L
4 pCi/L
1 pCi/L
1 pCi/L
0.001 ug/L
1. The MCL concentration for arsenic is now 0.01 mg/L The Six-Year data were analyzed relative to the former MCL
concentration of 0.05 mg/L because that was the MCL during the period of review for the Six-Year 2 analysis (1998
through 2005). However, additional analyses relative to the new arsenic MCL concentration are included in Chapter
5.
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2. The reduced number of systems sampling for SOC data, as compared to lOCs and VOCs, likely relates to state
waivers for pesticides and herbicides.
3. The revised Radionuclides Rule (published in 2000) went into effect on December 8, 2003 so combined radium-
226 and -228 occurrence data collected before December 8, 2003 were analyzed and presented in the row labeled
"original Radionuclides rule" and data collected after December 8, 2003 were analyzed and presented in the row
labeled "revised Radionuclides rule."
1.4 Occurrence Analysis
A two-stage analytical approach is used to evaluate the Six-Year Review-ICR
contaminant occurrence data. "Stage 1" and "Stage 2" analyses (described below) were
conducted on the second Six-Year Review Category 1 contaminants, but only Stage 1 analyses
were conducted on the Category 2 contaminants described in this report.
The Stage 1 analytical methodology is a conservative approach for estimating
contaminant occurrence; estimates are based on simple counts of whether or not a system
reported at least one sample analytical detection greater than a specified concentration threshold.2
(This Stage 1 analysis can be viewed roughly as a peak occurrence assessment.) Occurrence
measures for each contaminant are estimated for systems and population-served by the systems.
A typical Stage 1 analysis is a simple count of the number (or percentage) of systems with at least
one analytical detection (at least one sample analytical result greater than or equal to the
minimum reporting level, MRL) of a specific contaminant, or at least one sample analytical
detection with a concentration greater than the MCL concentration. In contrast, Stage 2 analyses
are based on counts of systems with estimated mean concentrations of a contaminant greater than
some concentration threshold of interest. The Stage 1 analysis is more conservative than the
Stage 2 analysis. Stage 1 analyses will therefore always result in occurrence estimates that are
greater than (or occasionally equal to), but never less than Stage 2 analysis. Therefore, when very
low occurrence is estimated for a particular contaminant using the Stage 1 analytical approach,
the use of the Stage 2 analytical approach is generally not warranted. For a complete description
of the Stage 1 (and Stage 2) methodology, refer to USEPA (2009b). These findings for either the
Stage 1 or Stage 2 analyses are not representative of MCL violations.
EPA assessed the generated occurrence estimates of the regulated contaminants relative
to several different thresholds. Simple assessments of occurrence were made relative to the MRL,
identifying the presence of any detection of a contaminant. Analytical detections were also
evaluated relative to higher contaminant concentrations including the MCL concentration and
one-half the MCL concentration (l/2 MCL concentration). Analyses were conducted at greater
than the MCL concentration and greater than or equal to !/2 the MCL concentration. Contaminant
occurrence findings based on the Six-Year Review - ICR data are summarized in tables
presented in the specific contaminant chapters that follow this introductory chapter. To review all
the national occurrence estimates for all contaminants assessed for this second Six-Year Review,
please refer to the document The Analysis of the Contaminant Occurrence Data from Public
2 These Stage 1 analyses are conservative in the sense that they are protective of human health (i.e., because they are
based on a single, maximum sample detection value rather than an average value for each system, the Stage 1
analyses are more likely to overestimate occurrence and potential risks to human health than underestimate them).
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Water Systems in Support of the Second Six-Year Review of National Primary Drinking Water
Regulations (USEPA, 2009b).
1.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2001. About the Agency for Toxic
Substances and Disease Registry. Available on the Internet at:
http://www.atsdr.cdc.gov/about.html. Accessed June 28, 2001.
Extension Toxicology Network (EXTOXNET). 2008. "EXTOXNET - Extension TOXicology
NETwork." Available on the Internet at: http://extoxnet.orst.edu/etn.txt.html.
Gilliom, R.J., I.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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
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 Substance Data Bank (HSDB). 2006. "Fact Sheet Hazardous Substances Data Bank
(HSDB®)." Last modified September 25, 2006. Available on the Internet at:
http://www.nlm.nih.gov/pubs/factsheets/hsdbfs.html.
Leahy, P.P. and T.H. Thompson. 1994. The National Water-Quality Assessment Program. U.S.
Geological Survey Open-File Report 94-70, 4 p. Available on the Internet at:
http://water.uses.gov/nawqa/NAWQA.OFR94-70.html. Accessed October 25, 2004.
National Research Council (NRC). 2002. Opportunities to Improve the U.S. Geological Survey
National Water Quality Assessment Program. National Academy Press. 238 p. Available on the
Internet at: http://www.nap.edu/catalog/10267.html.
United States Environmental Protection Agency (USEPA). 2002. The Toxics Release Inventory
(TRI) and Factors to Consider When Using TRI Data. EPA-260-F-02-017. November 2002.
Available on the Internet at: http://www.epa.gov/triinter/2002 tri brochure.pdf
USEPA. 2003 a. EPA Protocol for the Review of Existing National Primary Drinking Water
Regulations. EPA-815-R-03-002. June 2003. Available on the Internet at:
http://www.epa.gov/safewater/standard/review/pdfs/support 6vr_protocal final.pdf
USEPA. 2003b. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information. Available on the Internet at: http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm.
USEPA. 2003 c. How are the Toxics Release Inventory Data Used? —government, business,
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academic and citizen uses. EPA-260-R-002-004. May 2003. Available on the Internet at:
http://www.epa.gov/tri/guide_docs/pdf/2003/2003_datausepaper.pdf.
USEPA. 2009a. Contaminant Occurrence Support Document for Category 1 Contaminants for
the Second Six-Year Review of National Primary Drinking Water Regulations. EPA Report 815-
B-09-01 O.October 2009.
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. 2009c. EPA Protocol for the Second Review of Existing National Primary Drinking
Water Regulations (Updated). EPA Report 815-B-09-002. October 2009.
United States Geological Survey (USGS). 2001. "Summary publications from 51 NAWQA study
units sampled in 1991-2001." Available on the Internet at:
http://water.usgs.gov/nawqa/nawqasum/. Last updated May 19, 2004.
USGS. 2007. Pesticide National Synthesis Project, 2002 Pesticide Use Maps. Available on the
Internet at: http://water.usgs.gov/nawqa/pnsp/usage/maps/compound listing.php?year=02.
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2 Alachlor
This chapter on alachlor is part of a report that is organized so that each chapter presents
information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and alachlor
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
2.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for alachlor on January 30, 1991 (56
FR 3526 (USEPA, 1991)). The NPDWR established a maximum contaminant level goal
(MCLG) of zero based on a cancer classification of B2, probable human carcinogen. The
NPDWR also established a maximum contaminant level (MCL) of 2 |ig/L based on analytical
feasibility.
According to USEPA (1998), alachlor (Ci4H20NO2Cl) is a colorless to white crystalline
solid typically used as an herbicide to control cropland weeds and grasses. It generally has a high
mobility and potential to leach, and the half life for its disappearance from soil ranges from 6 to
21 days. It is extremely persistent in ground water (USEPA, 1998). Trade names for alachlor
include Lasso and Alanex (USEPA, 1998).
2.2 Use, Production, and Releases
Alachlor was first registered in 1969. It is used nationwide, with particularly heavy usage
on corn, peanuts, sorghum, and soybeans (USEPA, 1998).
Exhibit 2-1, compiled by the United States Geological Survey (USGS, 2007), shows the
geographic distribution of estimated average annual alachlor use in the United States from 1999
through 2004. A breakdown of use by crop is also included. The map was created by the USGS
using state-level data sets on pesticide use rates from 1999-2004 compiled by the CropLife
Foundation, at the Crop Protection Research Institute, combined with county-level data on
harvested crop acreage obtained from the 2002 Census of Agriculture. Due to the nature of the
data sources, non-agricultural uses are not reflected here, and variations in use at the county-level
are also not well represented (Thelin and Gianessi, 2000). The USGS (2007) estimates that
almost 6.2 million pounds of alachlor active ingredient were used on average each year between
1999 and 2004.
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Exhibit 2-1: Estimated Annual Agricultural Use for Alachlor (c. 2002)
ALACHLOR - herbicide
2002 estimated annual agricultural use
Average annual use of
active ingredient
(pounds per square mils of agricultural
land in county)
G no estimated use
D 0.001 ID 0.044
D 0.045 to 0.245
D 0.246 to 1.043
D 1.044 to 2.799
• >=2.8
Crops
corn
soybeans
sorghum
sweet corn
dry beans
peanuts
Total
pounds applied
3687504
1Z41413
1023185
157974
1071 55
4200
Percent
national use
59.27
19.95
16.45
2.54
1.72
0.07
Source: USGS, 2007
The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for alachlor.
Alachlor is listed as a Toxics Release Inventory (TRI) chemical. TRI data indicate that
total off-site and on-site releases of alachlor for the period 1998-2006 ranged from 274 pounds to
about 11,000 pounds, with a general decrease over time (USEPA, 2008).
2.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The USGS National
Water Quality Assessment (NAWQA) program is a national-scale assessment of the occurrence
of contaminants in ambient surface and ground water. Contaminant occurrence in ambient water
provides information on the potential for contaminants to adversely affect drinking water
supplies. Data on the occurrence of alachlor in ambient water are available from the NAWQA
program.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
2.3.1 NA WQA Pesticide National Synthesis Project
The NAWQA Pesticide National Synthesis Project is a national-scale assessment of the
occurrence and behavior of pesticides in streams and ground water of the United States and the
potential for pesticides to adversely affect drinking water supplies or aquatic ecosystems. Under
the National Synthesis Project, the USGS monitored alachlor between 1992 and 2001 in streams
and wells across the country (Gilliom etal., 2007). The maximum long-term method detection
limit for alachlor was 0.002 |ig/L.
In NAWQA stream samples (Exhibit 2-2), alachlor was found at frequencies ranging
from 5.34% of samples in undeveloped areas to 6.11% in urban areas, 20.26% in mixed land use
settings, and 40.07% of samples in agricultural settings. The 95th percentile concentration was
0.002 |ig/L in undeveloped areas, 0.004 |ig/L in urban areas, 0.021 |ig/L in mixed land use
settings, and 0.110 |ig/L in agricultural settings. The highest concentration, 6.7 |ig/L, was found
at an agricultural site.
Exhibit 2-2: USGS National Synthesis Summary of NAWQA Monitoring of Alachlor
in Streams, 1992-2001
Land Use
Type
Agricultural
Mixed
Undeveloped
Urban
No. of Samples
(No. of Sites)
1,996(83)
1,378(65)
144(8)
806 (30)
Detection
Frequency
40.07%
20.26%
5.34%
6.11%
50tn Percentile
(Median)
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
95th Percentile
Concentration
(in ug/L)
0.110
0.021
0.002
0.004
Maximum
Concentration
(in ug/L)
6.700
3.800
0.010
0.092
Source: Gilliom et a/., 2007
1. ND = not detected (Concentration is less than the maximum long term method detection limit and is expected to
be less than any higher percentile concentration shown in the table)
In ground water NAWQA samples (Exhibit 2-3), alachlor was found at frequencies
ranging from 0% of samples in undeveloped areas to 0.47% in urban areas, 0.77% of samples in
mixed land use settings, and 2.78% of samples in agricultural settings. The 95th percentile
concentrations were less than the method detection limit in all settings. The highest
concentration, 1.3 |ig/L, was found in a mixed land use setting.
Exhibit 2-3: USGS National Synthesis Summary of NAWQA Monitoring of Alachlor
in Ground Water, 1992-2001
Land Use Type
Agricultural
Mixed
Number
of Wells
1,401
2,729
Detection
Frequency
2.78%
0.77%
50tn Percentile
(Median)
Concentration
(in ug/L)
ND1
ND1
95th Percentile
Concentration
(in ug/L)
ND1
ND1
Maximum
Concentration
(in ug/L)
0.946
1.3
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Land Use Type
Undeveloped
Urban
Number
of Wei Is
34
854
Detection
Frequency
0.00%
0.47%
50tn Percent! le
(Median)
Concentration
(in ug/L)
ND1
ND1
95th Percent! le
Concentration
(in ug/L)
ND1
ND1
Maximum
Concentration
(in ug/L)
ND1
0.146
Source: Gilliom et a/., 2007
1. ND = not detected (Concentration is less than the maximum long term method detection limit and is expected to be
less than any higher percentile concentration shown in the table)
2.3.2 EPA Summary Analysis ofNA WQA Data
Whereas the NAWQA program often uses the most representative data for a site to
calculate summary statistics, EPA, with the cooperation of the USGS, has performed a summary
analysis of all Cycle 1 water monitoring data from all study units (1992-2001) for alachlor.
Detection frequencies were computed as the percentage of samples and sites with detections (i.e.,
with at least one result equal to or greater than the reporting limit). Sample detections can be
biased by frequent sampling in areas with high (or low) occurrence. Calculating the percentage
of sites with detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 2-4. Overall, alachlor was
detected in 16.4% of samples and at 7.9% of sites. Alachlor was detected more frequently in
surface water sites than in ground water sites. The median concentration based on detections
from all sites was 0.015 |ig/L. The 99th percentile concentration based on detections from all
sites was 3.33 |ig/L.
Exhibit 2-4: EPA Summary Analysis of Alachlor Data from NAWQA Study Units,
1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
6,108
15,641
21,749
% Samples
with
Detections
1.9%
22.0%
16.4%
Number
of Sites
5,217
1,949
7,166
% Sites
with
Detections
1.6%
24.9%
7.9%
Concentration Values
(of detections, in ug/L)
Minimum
0.0023
0.0008
0.0008
Median
0.0246
0.015
0.015
95th
Percen-
tile
3.8
0.62
0.65
99th
Percen-
tile
9.8
3.09
3.33
Maximum
10
38.2
38.2
1. RLs (Reporting Limits) for alachlor varied, but did not exceed 0.002 pg/L Note that because this EPA analysis
involves more data points than the USGS analyses presented above, a direct comparison is not possible.
2.4 Occurrence in Drinking Water
Alachlor is regulated as a synthetic organic chemical (SOC) in drinking water. All non-
purchased community water systems (CWSs) and non-transient non-community water systems
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
(NTNCWSs) are required to sample for SOCs. The maximum waiver period for SOCs is three
years, but this waiver can be renewed indefinitely. (Systems may receive a waiver at any time
without having collected an SOC sample. With a waiver, systems are not required to collect an
SOC sample.)
All CWSs and NTNCWSs without an SOC waiver must collect four consecutive
quarterly samples during the initial three-year compliance period.l If all four samples are non-
detections, then a system serving less than 3,300 persons may reduce to one sample during each
consecutive compliance period; a system serving more than 3,300 persons may reduce to two
quarterly samples within a 12-month period during a 3-year compliance period. If a chemical is
detected (but is less than the MCL), the system must take one sample per quarter until results are
below the MCL (minimum of two quarterly samples for ground water systems and four quarterly
samples for surface water systems). If all quarterly samples are below the MCL, the system may
return to annual sampling. If a chemical is detected at a level greater than the MCL, the system
(whether ground water or surface water) must take quarterly samples until four consecutive
quarters are below the MCL. If all quarterly samples are below the MCL, the system may return
to annual sampling.
The analysis of alachlor occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
Forty-four of the Six-Year Review-ICR states provided occurrence data for alachlor.
(There were no alachlor data from Oklahoma.) These data consist of 155,989 analytical results
from 36,845 public water systems (PWSs) during the period from 1998 to 2005. The number of
sample results and systems vary by state, although the state data sets have been reviewed and
checked to ensure adequacy of coverage and completeness.
2.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 2-5
presents the number of samples and systems, as well as the population-served by the systems,
and the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For alachlor, 0.328% of 36,845 systems reported
detections. Exhibit 2-6 lists the minimum, median, 90th percentile, and maximum alachlor
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of alachlor, based on detections from all systems, is 0.31 |ig/L.
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the
MCL.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 2-5: Alachlor Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
118,787
33,522
73,774,399
Surface Water
37,202
3,323
123,537,567
Combined Ground &
Surface Water
155,989
36,845
197,311,966
Percent with Detections
Ground Water
0.193%
0.206%
3.728%
Surface Water
0.204%
1.565%
4.247%
Combined Ground &
Surface Water
0.196%
0.328%
4.053%
Exhibit 2-6: Alachlor Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.01
Median
0.32
90tn
Percentile
0.98
Maximum
5
Surface Water
0.01
0.2
0.83
14
Combined Ground &
Surface Water
0.01
0.31
0.92
14
The following maps illustrate the geographic distribution of alachlor occurrence in
drinking water. Exhibit 2-7 shows the states with systems with at least one detection and Exhibit
2-8 shows the states with systems with at least one detection greater than the MCL concentration.
Note that five states did not submit data for use in the Six-Year Review (Kansas2, Louisiana,
Mississippi, Pennsylvania, and Washington). Oklahoma submitted Six-Year data for most
contaminants; however, there is a statewide waiver for alachlor in Oklahoma so no alachlor data
were available from that state.
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Detection rates were generally low; only four states reported detections in more than 1%
of their systems. These states are all located in the eastern half of the United States. In six states,
between 0.5% and 1% of systems reported detections. Six states reported detections greater than
the MCL concentration of 2 |ig/L.
Exhibit 2-7: Percentage of Systems with at Least One Alachlor Detection, by State
Mfl Slates with Waivers or Not Submitting
! States with No Detections
| Less than 0.5% of Systems Detecting
Between 0.5% and 1% of Systems Detecting
More than 1% of Systems Detecting
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 2-8: Percentage of Systems with at Least One Alachlor Detection Greater
than the MCL Concentration (> 2 ug/L), by State
States with Waivers or Not Submitting
I States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
Between 0.1% and 0.5% of Systems with Detections > MCL
| More than 0.5% of Systems with Detections > MCL
Exhibit 2-9 presents the Stage 1 analysis of alachlor occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 1 |ig/L and 2 |ig/L. Nineteen (0.052% of) systems, serving about 85,000 persons,
reported at least one detection greater than or equal to 1 |ig/L; and 8 (0.022% of) systems,
serving about 25,000 persons, reported at least one detection greater than 2 |ig/L.
Exhibit 2-9: Alachlor Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 2 |jg/L
> 1 |jg/L
N umber of
Systems
Exceeding
Threshold
5
14
Percent of
Systems
Exceeding
Threshold
0.015%
0.042%
Total Population-
Served by
Systems
Exceeding
Threshold
13,383
39,016
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.018%
0.053%
Surface
Water
> 2 |jg/L
s 1 H9/L
3
5
0.090%
0.150%
12,036
46,473
0.010%
0.038%
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source
Water
Type
Combined
Ground &
Surface
Water
Threshold
> 2 |jg/L
> 1 H9/L
N umber of
Systems
Exceeding
Threshold
8
19
Percent of
Systems
Exceeding
Threshold
0.022%
0.052%
Total Population-
Served by
Systems
Exceeding
Threshold
25,419
85,489
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.013%
0.043%
2.5 References
Gilliom, R.J., I.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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
Thelin, G.P. and L.P. Gianessi. 2000. Method for Estimating Pesticide Use for County Areas of
the Conterminous United States. U.S. Geological Survey Open-File Report 00-250, 62 p.
Available on the Internet at: http://ca.water.usgs.gov/pnsp/rep/ofr00250/ofr00250.pdf.
United States Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
USEPA. 1998. Reregistration Eligibility Decision (RED) Alachlor. Washington, DC: Office of
Prevention, Pesticides, and Toxic Substances. EPA-738-R-98-020. Available on the Internet at:
http://www.epa.gov/oppsrrdl/REDs/0063.pdf.
USEPA. 2008. TRI Explorer: Trends - Alachlor. Released February 21, 2008. Available on the
Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for alachlor.] Accessed March 7,
2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
United States Geological Survey (USGS). 2007. 2002 Pesticide Use Maps. Available on the
Internet at:
http://water.usgs.gov/nawqa/pnsp/usage/maps/show map. php?year=02&map=ml 863.
Accessed March 6, 2008.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Alpha Particles
This chapter on gross alpha particle activity (alpha particles) is part of a report that is
organized so that each chapter presents information on one specific contaminant. Chapter 1 of
this report, Introduction, presents background information on all sources of data used as well as
the analytical approach used to estimate contaminant occurrence in drinking water. This
contaminant chapter includes background information (such as regulatory history, general
chemical information, and environmental fate and behavior), use and environmental release
information, and alpha particle occurrence estimates in ambient water and drinking water. All
drinking water occurrence estimates were based on data from the National Compliance
Monitoring Information Collection Request (ICR) Dataset for the Second Six-Year Review (the
"Six Year Review-ICR Dataset"). For detailed information regarding this dataset, data
management, data quality assessments, and the analytical approach used to generate all
contaminant occurrence estimates presented in this chapter, please refer to USEPA (2009).
3.1 Background
EPA published an interim Drinking Water Regulation for gross alpha particle activity on
July 9, 1976 (41 FR 28402 (USEPA, 1976)). The Maximum Contaminant Level (MCL) for gross
alpha particle activity (including radium-226, but excluding uranium and radon) established on
that date was 15 pCi/L. In 2000, EPA published the final National Primary Drinking Water
Regulations (NPDWR) for radionuclides. The MCL for alpha particles remained at 15 pCi/L.
The 2000 rule set a Maximum Contaminant Level Goal (MCLG) of zero for alpha particles,
based on a cancer classification of A (known human carcinogen) (USEPA, 2000).
Radioactive elements (radionuclides) occur naturally in some drinking water sources
(USEPA, 2006a). They result from the erosion of natural deposits of certain radioactive minerals
(USEPA, 2008). Alpha radiation is a type of ionizing radiation; alpha particles consist of two
protons and two neutrons. In fact, most of the naturally occurring radionuclides are alpha particle
emitters (USEPA, 2006b). Water samples with elevated alpha particle levels are generally
indicative of naturally occurring radioactive elements, including radium-224 and radium-226
(MDE, 2008).
3.2 Use, Production, and Releases
As alpha particles occur naturally in conjunction with radioactive elements, data for use,
production, and release are not available.
3.3 Occurrence in Ambient Water
No National Water Quality Assessment (NAWQA) Program data are available on the
occurrence of alpha particles in ambient waters.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
3.4 Occurrence in Drinking Water
Under the original radionuclides rule, all community water systems (CWSs) must
initially collect four consecutive quarterly samples in their distribution system. If the annual
average concentration of the initial sampling is equal to or less than /^ the MCL (7.5 pCi/L), then
a system may reduce to one sample every four years. If any alpha particle results are greater than
5 pCi/L (but is equal to or less than the MCL of 15 pCi/L), the system must analyze the same or
an equivalent sample for Radium-226. If Radium-226 is greater than 3 pCi/L, the system must
analyze for Radium-228. If the annual average alpha particle activity is greater than 1A the MCL
(but is equal to or less than the MCL), the system must take four consecutive quarterly samples
every four years. If the annual average of alpha particle activity is greater than the MCL, the
system must take one sample each quarter until the annual average is below the MCL or until the
state sets an alternate monitoring schedule.
Under the revised radionuclides rule, all CWSs must collect four consecutive quarterly
samples for alpha particle measurement at each entry point to the distribution system between
December 8, 2003 and December 31, 2007 unless the state grandfathered data collected between
June 2000 and December 8, 2003. In addition, the state may waive the final two quarters of
sampling if results from the first two quarters are below the detection limit. If the running annual
average of initial quarterly samples is less than the detection limit, the system may reduce
sampling to once every nine years. If the average is equal to or greater than the detection limit
but equal to or less than /^ the MCL, the system may reduce sampling to once every six years. If
the average is greater than /^ the MCL (but is equal to or less than the MCL), the system may
reduce sampling to once every three years. If the average is greater than the MCL, the system
must take one sample each quarter until the running annual average of results from consecutive
quarters no longer exceeds the MCL, or until the state sets an alternate monitoring schedule.
Quarterly monitoring is also triggered by one result that is more than four times the MCL or high
enough to cause the running annual average to exceed the MCL.
The analysis of alpha particle occurrence presented in the following section is based on
state compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and
most comprehensive compliance monitoring data set compiled by EPA's Drinking Water
Program to date.
Alpha particle data were provided by 35 of the Six-Year Review-ICR states. (No data
were received from Arkansas, California, Delaware, Georgia, Hawaii, Illinois, Massachusetts,
New Hampshire, Oklahoma, or Wisconsin.) The alpha particle data from the 35 states consist of
73,002 analytical results from 18,653 public water systems (PWSs) during the period from 1998
to 2005. The number of sample results and systems vary by state, although the state data sets
have been reviewed and checked to ensure adequacy of coverage and completeness.
3.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 3-1
presents the number of samples and systems, as well as the population-served by the systems,
and the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
are not representative of MCL violations. For alpha particles, 68.080% of 18,653 systems
reported detections. Exhibit 3-2 lists the minimum, median, 90th percentile, and maximum alpha
particle concentrations based on detections from all systems in the Six-Year Review-ICR
Dataset. The median concentration of alpha particles, based on detections from all systems, is
3.36pCi/L.
Exhibit 3-1: Summary of Alpha Particles Occurrence Data from the Six-Year
Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
61,653
16,467
40,744,045
Surface Water
11,349
2,186
80,426,355
Combined Ground &
Surface Water
73,002
18,653
121,170,400
Percent with Detections
Ground Water
58.993%
69.242%
78.754%
Surface Water
47.934%
59.332%
63.369%
Combined Ground &
Surface Water
57.274%
68.080%
68.542%
Exhibit 3-2: Alpha Particles Summary Statistics
Source Water Type
Ground Water
Detection Value (pCi/L)
Minimum
8E-10
Median
3.7
90tn
Percentile
13.81
Maximum
348.33
Surface Water
0.01
1.6
6.8
133.53
Combined Ground &
Surface Water
8E-10
3.36
13
348.33
The following maps illustrate the geographic distribution of alpha particle occurrence in
drinking water. Exhibit 3-3 shows the states with systems with at least one detection and Exhibit
3-4 shows the states with systems with at least one detection greater than the MCL
concentration. Note that five states did not submit any data for use in the Six-Year Review
(Kansas1, Louisiana, Mississippi, Pennsylvania, and Washington). Arkansas, California,
Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Delaware, Georgia, Hawaii, Illinois, Massachusetts, New Hampshire, Oklahoma, or Wisconsin
submitted Six-Year data for most contaminants, but did not submit data for alpha particles.
The distribution of systems with detections of alpha particles is geographically dispersed
and detection rates were relatively high. In 9 states, more than 90% of systems reported
detections of alpha particles. In 26 states, more than 0.5% of systems reported at least one
detection greater than the MCL concentration of 15 pCi/L.
Exhibit 3-3: Percentage of Systems with at Least One Alpha Particles Detection,
by State
;>:;X States with Waivers or Not Submitting
States with No Detections
~ Less than 50% of Systems Detecting
| Between 50% and 90% of Systems Detecting
^B More than 90% of Systems Detecting
included in the analyses
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 3-4: Percentage of Systems with at Least One Alpha Particles Detection
Greater than the MCL Concentration (> 15 pCi/L), by State
'////, States with Waivers or Not Submitting
States witn No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
H Between 0.1% and 0.5% of Systems with Detections > MCL
^H More than 0.5% of Systems with Detections > MCL
Exhibit 3-5 presents the Stage 1 analysis of alpha particle occurrence in drinking water
from systems and population-served by those systems in the Six-Year Review-ICR Dataset
relative to two thresholds: 7.5 pCi/L and 15 pCi/L. A total of 2,596 (13.917% of) systems,
serving over 18.3 million persons, reported at least one detection greater than or equal to 7.5
pCi/L; and 854 (4.578% of) systems, serving more than 7.5 million persons, reported at least one
detection greater than 15 pCi/L.
Exhibit 3-5: Alpha Particles Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
>15pCi/L
>7.5pCi/L
Number of
Systems
Exceeding
Threshold
832
2,511
Percent of
Systems
Exceeding
Threshold
5.053%
15.249%
Total Population-
Served by
Systems
Exceeding
Threshold
2,891,759
8,323,500
Percent of
Population-Served
by Systems
Exceeding
Threshold
7.097%
20.429%
Surface
Water
>15pCi/L
>7.5pCi/L
22
85
1.006%
3.888%
4,631,051
10,037,894
5.758%
12.481%
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source
Water
Type
Combined
Ground &
Surface
Water
Threshold
>15pCi/L
>7.5pCi/L
Number of
Systems
Exceeding
Threshold
854
2,596
Percent of
Systems
Exceeding
Threshold
4.578%
13.917%
Total Population-
Served by
Systems
Exceeding
Threshold
7,522,810
18,361,394
Percent of
Population-Served
by Systems
Exceeding
Threshold
6.208%
15.153%
3.5 References
MDE (Maryland Department of the Environment). 2008. Radium and Your Drinking Water (A
Homeowner's Guide). Available on the Internet at:
http://www.mde. state.md.us/Programs/WaterPrograms/Water_Supply/radium.asp. Accessed
March 25, 2008.
United States Environmental Protection Agency (USEPA). 1976. Title 40—Protection of
Environment. Chapter 1—Environmental Protection Agency. Part 141—Interim Primary
Drinking Water Regulations. Promulgation of Regulations on Radionuclides. Federal Register,
Vol. 41, No. 133, p. 28402, July 9, 1976.
USEPA. 2000. National Primary Drinking Water Regulations; Radionuclides; Final Rule.
Federal Register. Vol. 65, No. 236. p. 76707, December 7, 2000.
USEPA. 2006a. Basic Information about Radionuclides in Drinking Water. Last modified
September 19, 2006. Available on the Internet at:
http://www.epa.gov/safewater/radionuclides/basicinformation.html. Accessed March 18, 2008.
USEPA. 2006b. Technical Fact Sheet: Final Rule for (Non-Radon) Radionuclides in Drinking
Water. Last modified September 19, 2006. Available on the Internet at:
http://www.epa.gov/OGWDW/radionuclides/regulation techfactsheet.html. Accessed March 25,
2008.
USEPA. 2008. Drinking Water Contaminants. Last modified February 15, 2008. Available on
the Internet at: http://www.epa.gov/safewater/contaminants/index.html. Accessed March 17,
2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
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4 Antimony
This chapter on antimony is part of a report that is organized so that each chapter presents
information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and antimony
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
4.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for antimony on July 17, 1992 (57 FR
31776 (USEPA, 1992)). The NPDWR established a maximum contaminant level goal (MCLG)
and a maximum contaminant level (MCL) of 0.006 mg/L. EPA based the maximum contaminant
level goal on a reference dose (RfD) of 0.0004 mg/kg-day and a cancer classification of D, not
classifiable as to human carcinogenicity.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 1992), in
its native state (uncombined with other elements), antimony is a silvery white, brittle metal.
However, native antimony is rare. It usually occurs in the mineral stibnite, and also in trace
amounts in silver, copper, and lead ores. According to the United States Bureau of Reclamation
(USER, 2001), antimony is found in over 100 minerals. Little antimony is currently mined in the
United States. Most is imported, but it is also produced as a by-product of smelting lead and
other metals (ATSDR, 1995).
Most antimony ends up in soil, where it attaches strongly to particles that contain iron,
manganese, or aluminum. Antimony is found at low levels in some rivers, lakes, and streams
(ATSDR, 1995). Antimony compounds do not tend to accumulate in aquatic life (ATSDR,
1992).
4.2 Use, Production, and Releases
Because it is brittle, antimony is not used in its native state. In alloy form, it is used in
lead storage batteries, solder, sheet and pipe metal, bearings, castings, and pewter. Antimony
oxide is added to textiles and plastics to prevent them from catching fire. It is also used in paints,
ceramics, and fireworks, and as enamels for plastics, metal, and glass (ATSDR, 1995). The most
common end-use of antimony compounds is antimony trioxide for fire retardation (ATSDR,
1992).
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The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 4-1 presents the production of antimony in the United States from 1986 to 2002.
Note that the production of antimony in the United States was not documented in the Chemical
Update System until 1994 and has increased progressively since then.
Exhibit 4-1: Production of Antimony in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
No reports
No reports
< 10,000 pounds
10,000 - 500,000 pounds
> 1 million - 10 million pounds
Source: USEPA, 2003
Antimony and antimony compounds are listed as Toxics Release Inventory (TRI)
chemicals. TRI data indicate that total off-site and on-site releases of antimony for the period
1998-2006 ranged from approximately 829,000 pounds to approximately 1.8 million pounds,
with maximum releases occurring in 2003. On-site releases were greater than off-site releases
(USEPA, 2008a). Total antimony compound releases ranged from approximately 10 million
pounds to approximately 32 million pounds, with a general decrease over time. Amounts
released on-site were greater than amounts released off-site (USEPA, 2008b).
4.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of antimony in
ambient water are available from the NAWQA program.
4.3.1 EPA Summary Analysis ofNA WQA Data
EPA, with the cooperation of the USGS, has performed a summary analysis of all Cycle
1 water monitoring data from all study units (1992-2001) for antimony. Detection frequencies
were computed as the percentage of samples and sites with detections (i.e., with at least one
result equal to or greater than the reporting limit). Sample detections can be biased by frequent
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sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 4-2. Overall, antimony was
detected in 13.4% of samples and at 11.0% of sites. Antimony was detected slightly more
frequently in surface water than in ground water. The median concentration based on detections
from all sites was 0.186 |ig/L (0.000186 mg/L). The 99th percentile concentration based on
detections from all sites was 8 |ig/L (0.008 mg/L).
Exhibit 4-2: EPA Summary Analysis of Antimony Data from NAWQA Study Units,
1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
3,252
2,380
5,632
% Samples
with
Detections
12.5%
14.6%
13.4%
Number
of Sites
2,904
394
3,298
% Sites
with
Detections
9.9%
19.3%
11.0%
Concentration Values
(of detections, in ug/L)
Minimum
0.025
0.024
0.024
Median
0.099
0.23
0.186
95th
Percen-
tile
1.75
4.933
2.376
99th
Percen-
tile
4
10.779
8
Maximum
6.296
16.863
16.863
1. RLs (Reporting Umits) for antimony varied, but did not exceed 0.025 pg/L
4.4 Occurrence in Drinking Water
Antimony is regulated as an inorganic chemical (IOC) in drinking water. All community
water systems (CWSs) and non-transient non-community water systems (NTNCWSs) are
required to sample for the lOCs.l The maximum waiver period for lOCs is nine years.
Ground water systems must sample once during the initial three-year compliance period.
After three compliance periods without a detection, a ground water system may be granted a
nine-year waiver. Surface water systems must sample annually during the initial three-year
compliance period. After three annual samples without a detection, a surface water system may
be granted a nine-year waiver. If the results are greater than the MCL, the public water system
(PWS) must take one sample per quarter until results are below the MCL (minimum of two
quarterly samples for ground water systems and four quarterly samples for surface water
systems).2 If all quarterly samples are below the MCL, the system may continue at initial
monitoring indefinitely until the state or EPA establishes an alternate schedule.
1 Nitrate and nitrite have their own monitoring requirements. See the nitrate and nitrite chapters for details of those
requirements.
2 All new systems or systems using a new water source that began operation after January 22, 2004 must
demonstrate compliance with the MCL within a period of time specified by the State. The system must also comply
with the initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with
the MCL.
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The analysis of antimony occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
All of the Six-Year Review-ICR states provided occurrence data for antimony. These
data consist of 185,986 analytical results from 49,016 systems during the period from 1998 to
2005. The number of sample results and systems vary by state, although the state data sets have
been reviewed and checked to ensure adequacy of coverage and completeness.
4.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 4-3
presents the number of samples and systems, as well as the population-served by the systems,
and the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For antimony, 5.978% of 49,016 systems reported
detections. Exhibit 4-4 lists the minimum, median, 90th percentile, and maximum antimony
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of antimony, based on detections from all systems, is 0.001 mg/L.
Exhibit 4-3: Antimony Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
145,441
44,971
85,727,750
Surface Water
40,545
4,045
137,523,912
Combined Ground &
Surface Water
185,986
49,016
223,251,662
Percent with Detections
Ground Water
2.673%
5.677%
15.708%
Surface Water
3.581%
9.320%
21.390%
Combined Ground &
Surface Water
2.871%
5.978%
19.208%
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Exhibit 4-4: Antimony Summary Statistics
Source Water Type
Ground Water
Detection Value (mg/L)
Minimum
0.000041
Median
0.00079
90tn
Percent! le
0.006
Maximum
0.06
Surface Water
0.000042
0.001545
0.0071
0.06
Combined Ground &
Surface Water
0.000041
0.001
0.006
0.06
The following maps illustrate the geographic distribution of antimony occurrence in
drinking water. Exhibit 4-5 shows the states with systems with at least one detection and Exhibit
4-6 shows the states with systems with at least one detection greater than the MCL
concentration. Note that five states did not submit data for use in the Six-Year Review (Kansas3,
Louisiana, Mississippi, Pennsylvania, and Washington).
The distribution of systems with detections of antimony is geographically dispersed. In
seven states, more than 10% of systems detected antimony. In 30 states, between 1% and 10% of
systems reported detections. Nineteen states reported no detections greater than the MCL
concentration. For six states, more than 0.5% of systems reported at least one detection greater
than the MCL concentration of 0.006 mg/L.
Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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Exhibit 4-5: Percentage of Systems with at Least One Antimony Detection,
by State
>///,, States Not Submitting Any Data
States with No Detections
• Less than 1% of Systems Detecting
Between 1% and 10% of Systems Detecting
More than 10% of Systems Detecting
Exhibit 4-6: Percentage of Systems with at Least One Antimony Detection Greater
than the MCL Concentration (> 0.006 mg/L), by State
'////, States Not Submitting Any Data
States with No Detections > MCL
| Less than 0.1% of Systems with Detections > MCL
^B Between 0.1% and 0.5% of Systems with Detections > MCL
HB More than 0.5% of Systems with Detections > MCL
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Exhibit 4-7 presents the Stage 1 analysis of antimony occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 0.003 mg/L and 0.006 mg/L. A total of 629 (1.283% of) systems, serving more
than 12 million persons, reported at least one detection greater than or equal to 0.003 mg/L; and
130 (0.265% of) systems, serving almost 3.4 million persons, reported at least one detection
greater than 0.006 mg/L.
Exhibit 4-7: Antimony Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 0.006 mg/L
> 0.003 mg/L
Number of
Systems
Exceeding
Threshold
97
512
Percent of
Systems
Exceeding
Threshold
0.216%
1.139%
Total Population-
Served by
Systems
Exceeding
Threshold
251,693
1,812,718
Percent of
Population-Served
by Systems
Exceeding
Threshold
0.294%
2.115%
Surface
Water
> 0.006 mg/L
> 0.003 mg/L
33
117
0.816%
2.892%
3,108,813
10,308,814
2.261%
7.496%
Combined
Ground &
Surface
Water
> 0.006 mg/L
> 0.003 mg/L
130
629
0.265%
1 .283%
3,360,506
12,121,532
1.505%
5.430%
4.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 1992. Toxicological Profile for
Antimony and Compounds. September 1992. Available on the Internet at:
http ://www. atsdr. cdc.gov/toxprofiles/tp23 .pdf.
ATSDR. 1995. ToxFAQs for Antimony and Compounds. September 1995. Available on the
Internet at: http://www.atsdr.cdc.gov/tfacts23.html.
United States Bureau of Reclamation (USER). 2001. Antimony Fact Sheet. Last modified Sept.
21, 2001. Available on the Internet at:
http://www.usbr.gov/pmts/water/publications/reportpdfs/Sb.pdf
United States Environmental Protection Agency (USEPA). 1992. Drinking Water; National
Primary Drinking Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals;
National Primary Drinking Water Regulations Implementation; Final Rule. Federal Register.
Vol. 57, No. 138. p. 31776, July 17, 1992.
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USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - Antimony. Last modified September 10, 2007. Available on the Internet at:
http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for antimony.] Accessed February
21,2008.
USEPA. 2008a. TRI Explorer: Trends - Antimony. Released February 21, 2008. Available on
the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for antimony.] Accessed
March 6, 2008.
USEPA. 2008b. TRI Explorer: Trends - Antimony Compounds. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for antimony
compounds.] Accessed March 6, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
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5 Arsenic
This chapter on arsenic is part of a report that is organized so that each chapter presents
information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and arsenic
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
5.1 Background
In 1976, the United States Environmental Protection Agency (EPA) issued a National
Interim Primary Drinking Water Regulation for arsenic at 0.05 mg/L. Under the 1986
amendments to the Safe Drinking Water Act (SDWA), Congress directed EPA to publish
Maximum Contaminant Level Goals (MCLGs) and promulgate National Primary Drinking Water
Regulations (NPDWRs) for 83 contaminants, including arsenic. EPA failed to publish an arsenic
NPDWR at that time (USEPA, 1998). On June 22, 2000, EPA proposed a Maximum
Contaminant Level (MCL) of 0.005 mg/L (USEPA, 2000). The Final Rule, published on January
22, 2001, established an MCLG of zero (based on a cancer classification of A, known human
carcinogen) and an MCL at 0.01 mg/L (USEPA, 2001). The date by which systems must comply
with the new 0.01 mg/L standard was January 23, 2006. Until then, the MCL was 0.05 mg/L
(USEPA, 2003a).
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2007),
arsenic is a naturally occurring element widely distributed in the earth's crust. Its primary sources
are its main ore mineral, arsenopyrite, and smelting of copper, gold, and lead (USGS, 2006). It is
odorless and tasteless (USEPA, 2007) in its native (uncombined) state. In the environment, it
combines with oxygen, chlorine, and sulfur to form inorganic arsenic compounds. Organic
arsenic compounds are formed when arsenic in animals and plants combines with carbon and
hydrogen (ATSDR, 2007).
5.2 Use, Production, and Releases
Inorganic arsenic compounds are mainly used to preserve wood. Chromated copper
arsenate (CCA), no longer used in the United States for residential uses, was used to make
"pressure-treated" lumber. It is, however, still used in industrial applications. Organic arsenic
compounds are used as pesticides, primarily on cotton fields and orchards (ATSDR, 2007).
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The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 5-1 presents the production of arsenic in the United States from 1986 to 2002.
Note that the production of arsenic in the United States was only documented in the Chemical
Update System in 1998.
Exhibit 5-1: Production of Arsenic in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
No reports
No reports
No reports
> 500,000 - 1 million pounds
No reports
Source: USEPA, 20036
Arsenic and arsenic compounds are listed as Toxics Release Inventory (TRI) chemicals.
TRI data indicate that total off-site and on-site releases of arsenic for the period 1998-2006
ranged from approximately 824,000 pounds to approximately 76.8 million pounds, with an
overall decrease over time. On-site releases were greater than off-site releases (USEPA, 2008a).
Total arsenic compound releases ranged from approximately 111 million pounds to
approximately 569 million pounds, with a general decrease over time. Amounts released on-site
were greater than amounts released off-site (USEPA, 2008b).
5.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of arsenic in
ambient water are available from the NAWQA program.
5.3.1 EPA Summary Analysis ofNA WQA Data
EPA, with the cooperation of the USGS, has performed a summary analysis of all Cycle 1
water monitoring data from all study units (1992-2001) for arsenic. Detection frequencies were
computed as the percentage of samples and sites with detections (i.e., with at least one result
equal to or greater than the reporting limit). Sample detections can be biased by frequent
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sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 5-2. Overall, arsenic was
detected in 55.1% of samples and at 52.9% of sites. Arsenic was detected more frequently in
surface water than in ground water. The median concentration based on detections from all sites
was about 2.3 |ig/L (0.0023 mg/L). The 99th percentile concentration based on detections from all
sites was 79 |ig/L (0.079 mg/L).
Exhibit 5-2: EPA Summary Analysis of Arsenic Data from NAWQA Study Units,
1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
3,725
2,460
6,185
% Samples
with
Detections
53.7%
57.1%
55.1%
Number
of Sites
3,303
468
3,771
% Sites
with
Detections
51.7%
61.3%
52.9%
Concentration Values
(of detections, in ug/L)
Minimum
0.091
0.09
0.09
Median
2
3
2.27
95th
Percen-
tile
24.06
16.406
22.728
99th
Percen-
tile
57
104.15
79
Maximum
550
284
550
1. RLs (Reporting Limits) for arsenic varied, but did not exceed 0.091 pg/L
5.4 Occurrence in Drinking Water
Arsenic is regulated as an inorganic chemical (IOC) in drinking water. All community
water systems (CWSs) and non-transient non-community water systems (NTNCWSs) are
required to sample for the lOCs.l The maximum waiver period for lOCs is nine years.
Ground water systems must sample once during the initial three-year compliance period.
After three compliance periods without a detection, a ground water system may be granted a
nine-year waiver. Surface water systems must sample annually during the initial three-year
compliance period. After three annual samples without a detection, a surface water system may
be granted a nine-year waiver. If the results are greater than the MCL, the public water system
(PWS) must take one sample per quarter until results are below the MCL (minimum of two
quarterly samples for ground water systems and four quarterly samples for surface water
systems).2 If all quarterly samples are below the MCL, the system may continue at initial
monitoring indefinitely until the state or EPA establishes an alternate schedule.
1 Nitrate and nitrite have their own monitoring requirements. See the nitrate and nitrite chapters for details of those
requirements.
2 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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The analysis of arsenic occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
All of the Six-Year Review-ICR states provided occurrence data for arsenic. These data
consist of 224,035 analytical results from 49,473 systems during the period from 1998 to 2005.
The number of sample results and systems vary by state, although the state data sets have been
reviewed and checked to ensure adequacy of coverage and completeness.
5.4.1 Stage 1A nalysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 5-3
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For arsenic, 37.329% of 49,473 systems reported
detections. Exhibit 5-4 lists the minimum, median, 90th percentile, and maximum arsenic
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of arsenic, based on detections from all systems, is 0.005 mg/L.
Exhibit 5-3: Arsenic Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
176,964
45,387
85,737,044
Surface Water
47,071
4,086
144,656,184
Combined Ground &
Surface Water
224,035
49,473
230,393,228
Percent with Detections
Ground Water
39.904%
37.788%
50.451%
Surface Water
25.627%
32.232%
48.633%
Combined Ground &
Surface Water
36.904%
37.329%
49.309%
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Exhibit 5-4: Arsenic Summary Statistics
Source Water Type
Ground Water
Detection Value (mg/L)
Minimum
0.000058
Median
0.00546
90tn
Percentile
0.02
Maximum
0.75
Surface Water
0.00006
0.0033
0.01
0.44
Combined Ground &
Surface Water
0.000058
0.005
0.02
0.75
The following maps illustrate the geographic distribution of arsenic occurrence in
drinking water. Exhibit 5-5 shows the states with systems with at least one detection, Exhibit 5-6
shows the states with systems with at least one detection greater than the new MCL concentration
of 0.01 mg/L, and Exhibit 5-7 shows the states with systems with at least one detection greater
than the former MCL concentration of 0.05 mg/L. Note that five states did not submit data for
use in the Six-Year Review (Kansas3, Louisiana, Mississippi, Pennsylvania, and Washington).
Detection rates were high for arsenic. In 12 states, more than 50% of systems detected
arsenic. Most of these states are located in the Southwest, northern Midwest, or northern New
England. In 19 states, more than 5% of systems reported at least one detection greater than the
new MCL concentration of 0.01 mg/L. In 16 states, more than 0.5% of systems reported at least
one detection greater than the former MCL concentration of 0.05 mg/L.
3 Kansas submitted data after the data management and analyses had been conducted; data from Kansas are not
included in the analyses.
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Exhibit 5-5: Percentage of Systems with at Least One Arsenic
Detection, by State
States Not Submitting Any Data
States with No Detections
• Less than 10% of Systems Detecting
Between 10% and 50% of Systems Detecting
More than 50% of Systems Detecting
Exhibit 5-6: Percentage of Systems with at Least One Arsenic Detection
Greater than the new MCL Concentration (> 0.01 mg/L), by State
States Not Submitting Any Data
States with No Detections > 0.01 mg/L
Less than 1% of Systems with Detections > 0.01 mg/L
Between 1% and 5% of Systems with Detections > 0.01 mg/L
Mora than 5% of Systems with Detections > 0.01 mg/L
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Exhibit 5-7: Percentage of Systems with at Least One Arsenic Detection Greater
than the former MCL Concentration (> 0.05 mg/L), by State
'////, States Not Submitting Any Data
j States with No Detections > 0.05 mg/L
_| Less than 0.1% of Systems with Detections > 0.05 mg/L
^B Between 0.1% and 0.5% of Systems with Detections > 0.05 mg/L
^B More than 0.5% of Systems with Detections > 0.05 mg/L
Exhibit 5-8 presents the Stage 1 analysis of arsenic occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
several thresholds: 0.005 mg/L, 0.01 mg/L, 0.025 mg/L, and 0.05 mg/L. Note that the MCL
concentration for arsenic is currently 0.01 mg/L. The Six-Year data were also analyzed relative to
the former MCL concentration of 0.05 mg/L because that was the MCL concentration during the
period of review for the Six-Year 2 analysis (1998 through 2005).
More than 8,200 (16.631% of) systems, serving more than 47 million persons, reported at
least one detection greater than or equal to 0.005 mg/L; and about 3,500 (7.107% of) systems,
serving almost 24.4 million persons, reported at least one detection greater than 0.01 mg/L.
Almost 1,300 (2.569% of) systems, serving more than 11 million persons, reported at least one
detection greater than or equal to 0.025 mg/L; and 371 (0.750% of) systems, serving
approximately 2.9 million persons, reported at least one detection greater than 0.05 mg/L.
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Exhibit 5-8: Arsenic Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water Type
Ground
Water
Threshold
> 0.05 mg/L
> 0.025 mg/L
> 0.01 mg/L
> 0.005 mg/L
Number of
Systems
Exceeding
Threshold
346
1,216
3,364
7,859
Percent of
Systems
Exceeding
Threshold
0.762%
2.679%
7.412%
17.316%
Total Population -
Served by
Systems
Exceeding
Threshold
1,352,250
3,901,453
8,655,516
18,464,077
Percent of
Population-Served
by Systems
Exceeding
Threshold
1.577%
4.550%
10.095%
21.536%
Surface
Water
> 0.05 mg/L
> 0.025 mg/L
> 0.01 mg/L
> 0.005 mg/L
25
55
152
369
0.612%
1.346%
3.720%
9.031%
1,503,598
7,158,650
15,741,605
28,990,530
1.039%
4.949%
10.882%
20.041%
Combined
Ground &
Surface
Water
> 0.05 mg/L
> 0.025 mg/L
> 0.01 mg/L
> 0.005 mg/L
371
1,271
3,516
8,228
0.750%
2.569%
7.107%
16.631%
2,855,848
11,060,103
24,397,121
47,454,607
1 .240%
4.801%
10.589%
20.597%
5.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2007. ToxFAQs for Arsenic.
August 2007. Available on the Internet at: http://www.atsdr.cdc.gov/tfacts2.html.
United States Environmental Protection Agency (USEPA). 1998. Announcement of Stakeholders
Meeting on Arsenic in Drinking Water. Federal Register. Vol. 63, No. 17. p. 3890-3891, January
27, 1998.
USEPA. 2000. National Primary Drinking Water Regulations; Arsenic and Clarifications to
Compliance and New Source Contaminants Monitoring. Federal Register. Vol. 65, No. 121. p.
38888, June 22, 2000.
USEPA. 2001. National Primary Drinking Water Regulations; Arsenic and Clarifications to
Compliance and New Source Contaminants Monitoring. Federal Register. Vol. 66, No. 14. p.
6975-7066, January 22, 2001.
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USEPA. 2003a. Minor Clarification of National Primary Drinking Water Regulation for Arsenic.
Federal Register. Vol. 68, No. 57. p. 14507, March 25, 2003.
USEPA. 2003b. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - Arsenic. Last modified September 10, 2007. Available on the Internet at:
http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for arsenic.] Accessed February
21,2008.
USEPA. 2007. Arsenic in Drinking Water: Basic Information. Last modified March 26, 2007.
Available on the Internet at: http://www.epa.gov/safewater/arsenic/basicinformation.html.
Accessed March 6, 2008.
USEPA. 2008a. TRI Explorer: Trends - Arsenic. Released February 21, 2008. Available on the
Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for arsenic.] Accessed March 6,
2008.
USEPA. 2008b. TRI Explorer: Trends - Arsenic Compounds. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for arsenic
compounds.] Accessed March 6, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
United States Geological Survey (USGS). 2006. U.S. Geological Survey, Mineral Commodity
Summaries (arsenic). Available on the internet at:
http://minerals.usgs.gov/minerals/pubs/commodity/arsenic/arsenmcs06.pdf Accessed March 15,
2008.
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6 Asbestos
This chapter on asbestos is part of a report that is organized so that each chapter presents
information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and asbestos
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
6.1 Background
EPA published the current National Primary Drinking Water Regulations (NPDWR) for
asbestos on January 30, 1991 (56 FR 3526 (USEPA, 1991)). The NPDWR established a
maximum contaminant level goal (MCLG) and a maximum contaminant level (MCL) of 7
million fibers per liter (MFL) for asbestos fibers exceeding 10 micrometers in length. EPA
evaluated asbestos as a Category U contaminant1 (equivalent to Group C, possible human
carcinogen) by the oral route of exposure.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2001),
asbestos is the name given to a group of six different fibrous minerals (amosite, chrysotile,
crocidolite, and the fibrous varieties of tremolite, actinolite, and anthophyllite) that occur
naturally in the environment. Asbestos minerals have separable long fibers that are strong and
flexible enough to be spun and woven and are heat resistant (ATSDR, 2001). The fibers can be
released to air or water from the breakdown of natural deposits or manufactured products. Small
fibers may remain airborne for a long time. Asbestos does not move through soil or decompose
(ASTDR, 2001).
6.2 Use, Production, and Releases
Because its minerals are so strong, flexible, and heat resistant, asbestos has been used for
a wide range of manufactured goods, mostly in building materials (roofing shingles, ceiling and
floor tiles, paper products, and asbestos-cement products), friction products (automobile clutch,
1 Note that this "Category II" classification for asbestos is different than it being a part of the group of 47 Category 2
contaminants discussed in this report. "Category II" contaminants include those contaminants for which EPA has
determined there is limited evidence of carcinogenicity from drinking water considering weight of evidence,
pharmacokinetics, potency, and exposure. For Category II contaminants, EPA has used two approaches to set the
MCLG: Either (1) setting the MCLG based upon non-carcinogenic endpoints of toxicity (the reference dose) then
applying an additional risk management factor of 1 to 10; or (2) setting the MCLG based upon a theoretical lifetime
excess cancer risk range of 10~5 to 10~6 using a conservative mathematical extrapolation model (USEPA, 2002).
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brake, and transmission parts), heat-resistant fabrics, packaging, gaskets, and coatings. Some
vermiculite or talc products may contain asbestos (ATSDR, 2001).
The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for asbestos.
Asbestos (friable) is listed as a Toxics Release Inventory (TRI) chemical. TRI data
indicate that total off-site and on-site releases of asbestos (friable) for the period 1998-2006
ranged from approximately 6.7 million pounds to approximately 24 million pounds, with a
decrease over time. On-site releases were greater than off-site releases (USEPA, 2008).
6.3 Occurrence in Ambient Water
No National Water Quality Assessment (NAWQA) Program data are available from the
United States Geological Survey (USGS) on the occurrence of asbestos in ambient waters from
the Pesticide National Synthesis Project (Gilliom et a/., 2007) or the EPA Summary Analysis of
Cycle 1 data.
6.4 Occurrence in Drinking Water
Asbestos is regulated as an inorganic chemical (IOC) in drinking water. All community
water systems (CWSs) and non-transient non-community water systems (NTNCWSs) are
required to sample for the IOCs.2 The maximum waiver period for lOCs is nine years. Statewide
waivers are often granted for asbestos.
Ground water systems must sample once during the initial three-year compliance period.
After three compliance periods without a detection, a ground water system may be granted a
nine-year waiver. Surface water systems must sample annually during the initial three-year
compliance period. After three annual samples without a detection, a surface water system may
be granted a nine-year waiver. If the results are greater than the MCL, the public water system
(PWS) must take one sample per quarter until results are below the MCL (minimum of two
quarterly samples for ground water systems and four quarterly samples for surface water
systems).3 If all quarterly samples are below the MCL, the system may continue at initial
monitoring indefinitely until the state or EPA establishes an alternate schedule.
The analysis of asbestos occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
2 Nitrate and nitrite have their own monitoring requirements. See the nitrate and nitrite chapters for details of those
requirements.
3 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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Asbestos data were provided by 38 of the Six-Year Review-ICR states. (There were no
asbestos data from the following states: Arkansas, Hawaii, Michigan, Minnesota, Missouri,
Oklahoma, and Texas.) The asbestos data from the 38 states consist of 18,181 analytical results
from 8,278 systems during the period from 1998 to 2005. The number of sample results and
systems vary by state, although the state data sets have been reviewed and checked to ensure
adequacy of coverage and completeness.
6.4.1 Stage 1A nalysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 6-1
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For asbestos, 3.237% of 8,278 systems reported
detections. Exhibit 6-2 lists the minimum, median, 90th percentile, and maximum asbestos
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of asbestos, based on detections from all systems, is 0.2 MFL.
Exhibit 6-1: Asbestos Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
13,837
6,873
22,423,343
Surface Water
4,344
1,405
62,738,591
Combined Ground &
Surface Water
18,181
8,278
85,161,934
Percent with Detections
Ground Water
2.211%
2.663%
5.018%
Surface Water
3.016%
6.050%
20.393%
Combined Ground &
Surface Water
2.404%
3.237%
16.345%
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Exhibit 6-2: Asbestos Summary Statistics
Source Water Type
Ground Water
Detection Value (MFL)
Minimum
0.02
Median
0.26
90tn
Percentile
4
Maximum
143.9
Surface Water
0.008
0.2
1.07
2,494
Combined Ground &
Surface Water
0.008
0.2
3.48
2,494
The following maps illustrate the geographic distribution of asbestos occurrence in
drinking water. Exhibit 6-3 shows the states with systems with at least one detection and Exhibit
6-4 shows the states with systems with at least one detection greater than the MCL concentration.
Note that five states did not submit data for use in the Six-Year Review (Kansas4, Louisiana,
Mississippi, Pennsylvania, and Washington). Arkansas, Hawaii, Michigan, Minnesota, Missouri,
Oklahoma, and Texas submitted Six-Year data for most contaminants but did not submit data for
asbestos.
The distribution of systems with detections of asbestos is geographically dispersed. In
nine states, more than 5% of systems detected asbestos. In 16 states, between 1% and 5% of
systems reported detections. Twenty-eight states reported no detections of asbestos greater than
the MCL concentration of 7 MFL. In three states, more than 0.5% of systems reported at least
one detection greater than 7 MFL.
4 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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Exhibit 6-3: Percentage of Systems with at Least One Asbestos Detection,
by State
Estates with Waivers or Not Submitting
States with No Detections
Less than 1 % of Systems Detecting
Between 1% and 5% of Systems Detecting
More than 5% of Systems Detecting
Exhibit 6-4: Percentage of Systems with at Least One Asbestos Detection Greater
than the MCL Concentration (> 7 MFL), by State
States with Waivers or Not Submitting
States with No Detections > MCL
I Less than 0.5% of Systems with Detections > MCL
I Between 0.5% and 1% of Systems with Detections > MCL
| More than 1% of Systems with Detections > MCL
Exhibit 6-5 presents the Stage 1 analysis of asbestos occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative
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two thresholds: 3.5 MFL and 7 MFL. A total of 25 (0.302% of) systems, serving more than
400,000 persons, reported at least one detection greater than or equal to 3.5 MFL; and 14
(0.169% of) systems, serving approximately 254,000 persons, reported at least one detection
greater than 7 MFL.
Exhibit 6-5: Asbestos Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
>7MFL
> 3.5 MFL
Number of
Systems
Exceeding
Threshold
11
19
Percent of
Systems
Exceeding
Threshold
0.160%
0.276%
Total Population-
Served by
Systems
Exceeding
Threshold
57,015
82,927
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.254%
0.370%
Surface
Water
>7MFL
> 3.5 MFL
3
6
0.214%
0.427%
196,962
322,738
0.314%
0.514%
Combined
Ground &
Surface
Water
>7MFL
> 3.5 MFL
14
25
0.169%
0.302%
253,977
405,665
0.298%
0.476%
6.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2001. ToxFAQs for Asbestos.
September 2001. Available on the Internet at: http://www.atsdr.cdc.gov/tfacts61.html.
Gilliom, R.J., I.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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
United States Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
USEPA. 2002. National Primary Drinking Water Regulations; Announcement of the Results of
EPA's Review of Existing Drinking Water Standards and Request for Public Comment. Federal
Register. Vol. 67, No. 74. p. 19051, April 17, 2002.
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USEPA. 2008. TRI Explorer: Trends - Asbestos. Released February 21, 2008. Available on the
Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for asbestos (friable).] Accessed
March 6, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
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7 Atrazine
This chapter on atrazine is part of a report that is organized so that each chapter presents
information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and atrazine
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
7.1 Background
The United States Environmental Protection (EPA) published the current National
Primary Drinking Water Regulations (NPDWR) for atrazine on January 30, 1991 (56 FR 3526
(USEPA, 1991)). The NPDWR established a maximum contaminant level goal (MCLG) and a
maximum contaminant level (MCL) of 3 |ig/L. EPA based the MCLG on a reference dose (RfD)
of 5 jig/kg-day (0.005 mg/kg-day) and a cancer classification of Group C, possible human
carcinogen, based on limited evidence of carcinogenicity in animals in the absence of human
data. EPA published a Federal Register (FR) notice in February 1999, in which EPA responded
to recommendations by the Children's Health Advisory Committee, by committing to re-evaluate
the MCL for atrazine after the Agency has finalized its risk assessment (64 FR 5277 (USEPA,
1999)).
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2003a),
atrazine (CgHi/tClNs) is an herbicide that does not occur naturally. Pure atrazine is an odorless,
white powder that is not very volatile, reactive, or flammable, and that will dissolve in water
(ATSDR, 2003a). Atrazine has a high to medium mobility and is degraded slowly in most
environments, whether by biological or chemical processes. In soils it may persist for days or
months. In rare situations it may remain for years. Breakdown is especially slow in rivers and
lakes. It will also persist for a long time in groundwater. Atrazine does not tend to accumulate in
living organisms (ATSDR, 2003b).
7.2 Use, Production, and Releases
Although it is a restricted use pesticide, atrazine is the most heavily used pre- and post-
emergence herbicide in the United States (ATSDR, 2003b). It is used to kill weeds, primarily on
farms for crops such as corn, sorghum, and sugarcane; however, it has also been used on highway
and railroad rights-of-way (ATSDR, 2003a). Only trained individuals are allowed to spray
atrazine (ATSDR, 2003b).
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Exhibit 7-1, compiled by the United States Geological Survey (USGS, 2007), shows the
geographic distribution of estimated average annual atrazine use in the United States from 1999
through 2004. A breakdown of use by crop is also included. The map was created by the USGS
using state-level data sets on pesticide use rates from 1999-2004 compiled by the CropLife
Foundation, at the Crop Protection Research Institute, combined with county-level data on
harvested crop acreage obtained from the 2002 Census of Agriculture. Due to the nature of the
data sources, non-agricultural uses are not reflected here, and variations in use at the county-level
are also not well represented (Thelin and Gianessi, 2000). The USGS (2007) estimates that
almost 76.5 million pounds of atrazine active ingredient were used on average each year between
1999 and 2004.
Exhibit 7-1: Estimated Annual Agricultural Use for Atrazine (c. 2002)
ATRAZINE - herbicide
2002 estimated annual agricultural use
Average annual use of
active ingredient
(pounds per square mils of agricultural
land in county)
G no estimated use
D 0.001 ID 0.307
D 0.308 to 1.91
D 1.911 to 9.32
D 9.321 to 34.596
• >= 34.597
Total
Cr°Ps pounds aoolied
corn
sorghum
sugarcane
cropland in summer fallow
sweet corn
sod harvested
other hay
field and grass seed crop
66148829
5636302
2377458
1843850
429351
54700
7013
620
Percent
national use
86.47
7.37
3.11
2.41
0.56
0.07
0.01
0.00
Source: USGS, 2007
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 7-2 presents the production of atrazine in the United States from 1986 to 2002.
Note that the production of atrazine in the United States increased from 1986 to 1998 and was
not reported in the Chemical Update System in 2002.
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Exhibit 7-2: Production of Atrazine in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
> 1 million - 10 million pounds
> 1 million - 10 million pounds
> 10 million - 50 million pounds
> 10 million - 50 million pounds
No reports
Source: USEPA, 2003
Atrazine is listed as a Toxics Release Inventory (TRI) chemical. TRI data indicate that
total off-site and on-site releases of atrazine for the period 1998-2006 ranged from about 504,000
pounds to about 700,000 pounds, with the maximum releases occurring in 2005. On-site releases
were greater than off-site releases (USEPA, 2008).
7.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The USGS National
Water Quality Assessment (NAWQA) program is a national-scale assessment of the occurrence
of contaminants in ambient surface and ground water. Contaminant occurrence in ambient water
provides information on the potential for contaminants to adversely affect drinking water
supplies. Data on the occurrence of atrazine in ambient water are available from the NAWQA
program.
7.3.1 NA WQA Pesticide National Synthesis Project
The NAWQA Pesticide National Synthesis Project is a national-scale assessment of the
occurrence and behavior of pesticides in streams and ground water of the United States and the
potential for pesticides to adversely affect drinking water supplies or aquatic ecosystems. Under
the National Synthesis Project, the USGS monitored atrazine between 1992 and 2001 in streams
and wells across the country (Gilliom etal., 2007). The maximum long-term method detection
limit for atrazine was 0.004 |ig/L.
In NAWQA stream samples (Exhibit 7-3), atrazine was found at frequencies ranging
from 54.26% of samples in undeveloped areas to 70.73% in urban areas, 85.13% in mixed land
use settings, and 89.93% of samples in agricultural settings. The 95th percentile concentration
was 0.050 |ig/L in undeveloped areas, 0.209 |ig/L in urban areas, 0.678 |ig/L in mixed land use
settings, and 2.400 |ig/L in agricultural settings. The highest concentration, 201 |ig/L, was found
at an agricultural site.
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Exhibit 7-3: USGS National Synthesis Summary of NAWQA Monitoring of Atrazine
in Streams, 1992-2001
Land Use
Type
Agricultural
Mixed
Undeveloped
Urban
No. of Samples
(No. of Sites)
2,009(83)
1,382(65)
143(8)
801 (30)
Detection
Frequency
89.93%
85.13%
54.26%
70.73%
50th Percent! le
(Median)
Concentration
(in ug/L)
0.073
0.016
0.003
0.009
95th Percentile
Concentration
(in |jg/L)
2.400
0.678
0.050
0.209
Maximum
Concentration
(in ug/L)
201.000
41.300
2.000
3.370
Source: Gilliom et a/., 2007
In ground water NAWQA samples (Exhibit 7-4), atrazine was found at frequencies
ranging from 11.76% of samples in undeveloped areas to 18.17% in mixed land use settings,
31.34% of samples in urban areas, and 42.18% of samples in agricultural settings. The 95th
percentile concentration was 0.0082 |ig/L in undeveloped areas, 0.033 |ig/L in mixed land use
settings, 0.089 |ig/L in urban areas, and 0.358 |ig/L in agricultural settings. The highest
concentration, 4.78 |ig/L, was found at an agricultural site.
Exhibit 7-4: USGS National Synthesis Summary of NAWQA Monitoring of Atrazine
in Ground Water, 1992-2001
Land Use Type
Agricultural
Mixed
Undeveloped
Urban
Number
of Wells
1,406
2,730
34
852
Detection
Frequency
42.18%
18.17%
11.76%
31.34%
50th Percentile
(Median)
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
95th Percentile
Concentration
(in ug/L)
0.358
0.033
0.0082
0.089
Maximum
Concentration
(in ug/L)
4.78
2.8
0.0085
4.2
Source: Gilliom et a/., 2007
1. ND = not detected (Concentration is less than the maximum long term method detection limit and is expected to
be less than any higher percentile concentration shown in the table)
7.3.2 EPA Summary Analysis ofNA WQA Data
Whereas the NAWQA program often uses the most representative data for a site to
calculate summary statistics, EPA, with the cooperation of the USGS, has performed a summary
analysis of all Cycle 1 water monitoring data from all study units (1992-2001) for atrazine.
Detection frequencies were computed as the percentage of samples and sites with detections (i.e.,
with at least one result equal to or greater than the reporting limit). Sample detections can be
biased by frequent sampling in areas with high (or low) occurrence. Calculating the percentage of
sites with detections can reduce this bias.
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The results of the EPA analysis are presented in Exhibit 7-5. Overall, atrazine was
detected in 65.8% of samples and at 44.2% of sites. Atrazine was detected more frequently in
surface water than in ground water. The median concentration based on detections from all sites
was 0.0369 |ig/L. The 99th percentile concentration based on detections from all sites was 13.4
Exhibit 7-5: EPA Summary Analysis of Atrazine Data from NAWQA Study Units,
1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
6,093
15,604
21,697
%
Samples
with
Detections
30.8%
79.4%
65.8%
Number
of Sites
5,203
1,948
7,151
% Sites
with
Detections
29.7%
83.0%
44.2%
Concentration Values
(of detections, in ug/L)
Minimum
0.0004
0.0001
0.0001
Median
0.017
0.0412
0.0369
95th
Percen-
tile
0.53
2.57
2.21
99th
Percen-
tile
1.71
14.8
13.4
Maximum
5.01
201
201
1. RLs (Reporting Limits) for atrazine varied, but did not exceed 0.0004 ug/L. Note that because this EPA analysis
involves more data points than the USGS analyses presented above, a direct comparison is not possible.
7.4 Occurrence in Drinking Water
Atrazine is regulated as a synthetic organic chemical (SOC) in drinking water. All non-
purchased community water systems (CWSs) and non-transient non-community water systems
(NTNCWSs) are required to sample for SOCs. The maximum waiver period for SOCs is three
years, but this waiver can be renewed indefinitely. (Systems may receive a waiver at any time
without having collected an SOC sample. With a waiver, systems are not required to collect an
SOC sample.)
All CWSs and NTNCWSs without an SOC waiver must collect four consecutive
quarterly samples during the initial three-year compliance period.l If all four samples are non-
detections, then a system serving less than 3,300 persons may reduce to one sample during each
consecutive compliance period; a system serving more than 3,300 persons may reduce to two
quarterly samples within a 12-month period during a 3-year compliance period. If a chemical is
detected (but is less than the MCL), the system must take one sample per quarter until results are
below the MCL (minimum of two quarterly samples for ground water systems and four quarterly
samples for surface water systems). If all quarterly samples are below the MCL, the system may
return to annual sampling. If a chemical is detected at a level greater than the MCL, the system
(whether ground water or surface water) must take quarterly samples until four consecutive
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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quarters are below the MCL. If all quarterly samples are below the MCL, the system may return
to annual sampling.
The analysis of atrazine occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
Forty-four of the Six-Year Review-ICR states provided occurrence data for atrazine.
(There were no atrazine data from Oklahoma.) These data consist of 161,690 analytical results
from 37,215 public water systems (PWSs) during the period from 1998 to 2005. The number of
sample results and systems vary by state, although the state data sets have been reviewed and
checked to ensure adequacy of coverage and completeness.
7.4.1 Stage 1A nalysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 7-6
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For atrazine, 2.386% of 37,215 systems reported
detections. Exhibit 7-7 lists the minimum, median, 90th percentile, and maximum atrazine
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of atrazine, based on detections from all systems, is 0.4 |ig/L.
Exhibit 7-6: Atrazine Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
121,515
33,752
74,386,872
Surface Water
40,175
3,463
125,985,718
Combined Ground &
Surface Water
161,690
37,215
200,372,590
Percent with Detections
Ground Water
1.725%
1.132%
7.923%
Surface Water
11.796%
14.612%
22.482%
Combined Ground &
Surface Water
4.227%
2.386%
17.077%
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Exhibit 7-7: Atrazine Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.003
Median
0.19
90tn
Percentile
0.69
Maximum
10.9
Surface Water
0.00037
0.55
1.7
27
Combined Ground &
Surface Water
0.00037
0.4
1.43
27
The following maps illustrate the geographic distribution of atrazine occurrence in
drinking water. Exhibit 7-8 shows the states with systems with at least one detection and Exhibit
7-9 shows the states with systems with at least one detection greater than the MCL concentration.
Note that five states did not submit data for use in the Six-Year Review (Kansas2, Louisiana,
Mississippi, Pennsylvania, and Washington). Oklahoma submitted Six-Year data for most
contaminants; however, there is a statewide waiver for atrazine in Oklahoma so no atrazine data
were available from that state.
Seven states reported detections in more than 5% of their systems. With the exception of
Hawaii, these states were all located in the central part of the United States. In 14 states, between
1% and 5% of systems reported detections. Only four states reported no detections of atrazine.
Fifteen states reported detections greater than the MCL concentration of 3 |ig/L.
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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Exhibit 7-8: Percentage of Systems with at Least One Atrazine Detection, by State
y//\ States with Waivers or Not Submitting
States with No Detections
ELess than 1 % of Systems Detecting
Between 1% and 5% of Systems Detecting
^H More than 5% of Systems Detecting
Exhibit 7-9: Percentage of Systems with at Least One Atrazine Detection Greater
than the MCL Concentration (> 3 M9/L), by State
^/ States with Waivers or Not Submitting
States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
B Between 0.1% and 0.5% of Systems with Detections > MCL
• More than 0.5% of Systems with Detections > MCL
Exhibit 7-10 presents the Stage 1 analysis of atrazine occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 1.5 |ig/L and 3 |ig/L. More than 180 (0.494% of) systems, serving about 8.2
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
million persons, reported at least one detection greater than or equal to 1.5 |ig/L; and 98 (0.263%
of) systems, serving more than 3.1 million persons, reported at least one detection greater than 3
Exhibit 7-10: Atrazine Stage 1 Analysis - Systems and Population with at Least
One Threshold Exceedance
Source
Water Type
Ground
Water
Threshold
> 3 |jg/L
>1.5|jg/L
Number of
Systems
Exceeding
Threshold
7
24
Percent of
Systems
Exceeding
Threshold
0.021%
0.071%
Total Population-
Served by
Systems
Exceeding
Threshold
93,709
220,526
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.126%
0.296%
Surface
Water
> 3 |jg/L
>1.5|jg/L
91
160
2.628%
4.620%
3,014,621
7,977,093
2.393%
6.332%
Combined
Ground &
Surface
Water
> 3 |jg/L
>1.5|jg/L
98
184
0.263%
0.494%
3,108,330
8,197,619
1.551%
4.091%
7.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2003a. ToxFAQs for Atrazine.
September 2003. Available on the Internet at: http://www.atsdr.cdc.gov/tfactsl53.html.
ATSDR. 2003b. Toxicological Profile for Atrazine. September 2003. Available on the Internet
at: http://www.atsdr.cdc.gov/toxprofiles/tpl53.pdf
Gilliom, R.J., I.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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
Thelin, G.P. and L.P. Gianessi. 2000. Method for Estimating Pesticide Use for County Areas of
the Conterminous United States. U.S. Geological Survey Open-File Report 00-250, 62 p.
Available on the Internet at: http://ca.water.usgs.gov/pnsp/rep/ofr00250/ofr00250.pdf
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United States Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
USEPA. 1999. Response to Recommendations from the Children's Health Protection Advisory
Committee Regarding Evaluation of Existing Environmental Standards; Notice. Federal Register.
Vol. 64, No. 22. p. 5277, February 3, 1999.
USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - Atrazine. Last modified September 10, 2007. Available on the Internet at:
http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for atrazine.] Accessed February
21,2008.
USEPA. 2008. TRI Explorer: Trends - Atrazine. Released February 21, 2008. Available on the
Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for atrazine.] Accessed March 6,
2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
United States Geological Survey (USGS). 2007. 2002 Pesticide Use Maps. Available on the
Internet at:
http://water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=02&map=ml980.
Accessed March 6, 2008.
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8 Barium
This chapter on barium is part of a report that is organized so that each chapter presents
information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and barium
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
8.1 Background
The United State Environmental Protection Agency (EPA) published the current National
Primary Drinking Water Regulations (NPDWR) for barium on July 1, 1991 (56 FR 30266
(USEPA, 1991)). The NPDWR established a maximum contaminant level goal (MCLG) and a
maximum contaminant level (MCL) of 2 mg/L. EPA based the MCLG on a reference dose (RfD)
of 0.07 mg/kg-day and a cancer classification of D, not classifiable as to human carcinogenicity.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2007),
barium is a silvery-white metal. Its primary source in nature is the mineral barite (Klein and
Hurlbut, 1993). Barium can be combined with nitrate, carbonate, or chloride to form barium
compounds (ATSDR, 2007). The length of time that it will last in air, land, water, or sediments
depends on the form of barium released. Some compounds, such as barium chloride, barium
nitrate, or barium hydroxide, that dissolve easily in water usually do not last in these forms for a
long time in the environment. However, the barium in these compounds that is dissolved in water
quickly combines with sulfate or carbonate that are naturally found in water and become the
longer lasting forms (barium sulfate and barium carbonate). Fish and aquatic organisms can
accumulate barium (ATSDR, 2007).
8.2 Use, Production, and Releases
Barium compounds are used by the oil and gas industries to make drilling muds. (Drilling
muds keep the drill bits lubricated, making it easier to drill through rock.) Barium compounds are
also used to make paint, bricks, ceramics, glass, and rubber. In addition, barium sulfate can be
used by doctors to perform medical tests and to take x-rays of the gastrointestinal tract (ATSDR,
2007).
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
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years. Exhibit 8-1 presents the production of barium in the United States from 1986 to 2002.
Note that the production of barium in the United States was only documented in the Chemical
Update System in 1994.
Exhibit 8-1: Production of Barium in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
No reports
No reports
10,000 - 500,000 pounds
No reports
No reports
Source: USEPA, 2003
Barium and barium compounds are listed as Toxics Release Inventory (TRI) chemicals.
TRI data indicate that total off-site and on-site releases of barium for the period 1998-2006
ranged from approximately 6.6 million pounds to approximately 12.9 million pounds, with a
decrease over time. On-site releases were greater than off-site releases (USEPA, 2008a). Total
barium compound releases ranged from approximately 211 million pounds to approximately 306
million pounds, with a general decrease over time. Amounts released on-site were greater than
amounts released off-site (USEPA, 2008b).
8.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of barium in
ambient water are available from the NAWQA program.
8.3.1 EPA Summary Analysis ofNA WQA Data
EPA, with the cooperation of the USGS, has performed a summary analysis of all Cycle 1
water monitoring data from all study units (1992-2001) for barium. Detection frequencies were
computed as the percentage of samples and sites with detections (i.e., with at least one result
equal to or greater than the reporting limit). Sample detections can be biased by frequent
sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
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The results of the EPA analysis are presented in Exhibit 8-2. Overall, barium was
detected in 99.3% of samples and at 98.8% of sites. Percentages of samples with detections were
similarly high for surface water and ground water. The median concentration based on detections
from all sites was approximately 38 |ig/L (0.038 mg/L). The 99th percentile concentration based
on detections from all sites was approximately 560 |ig/L (0.560 mg/L).
Exhibit 8-2: EPA Summary Analysis of Barium Data from NAWQA Study Units,
1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
3,253
2,378
5,631
% Samples
with
Detections
98.8%
100.0%
99.3%
Number
of Sites
2,905
393
3,298
% Sites
with
Detections
98.7%
100.0%
98.8%
Concentration Values
(of detections, in ug/L)
Minimum
1
1
1
Median
47
29.8
38.155
95th
Percen-
tile
327
107
237.43
99th
Percen-
tile
675
145.37
559.67
Maximum
5,053
258.4
5,053
1. RLs (Reporting Limits) for barium varied, but did not exceed 1 pg/L
8.4 Occurrence in Drinking Water
Barium is regulated as an inorganic chemical (IOC) in drinking water. All community
water systems (CWSs) and non-transient non-community water systems (NTNCWSs) are
required to sample for the lOCs.l The maximum waiver period for lOCs is nine years.
Ground water systems must sample once during the initial three-year compliance period.
After three compliance periods without a detection, a ground water system may be granted a
nine-year waiver. Surface water systems must sample annually during the initial three-year
compliance period. After three annual samples without a detection, a surface water system may
be granted a nine-year waiver. If the results are greater than the MCL, the public water system
(PWS) must take one sample per quarter until results are below the MCL (minimum of two
quarterly samples for ground water systems and four quarterly samples for surface water
systems).2 If all quarterly samples are below the MCL, the system may continue at initial
monitoring indefinitely until the state or EPA establishes an alternate schedule.
The analysis of barium occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
1 Nitrate and nitrite have their own monitoring requirements. See the nitrate and nitrite chapters for details of those
requirements.
2 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
All of the Six-Year Review-ICR states provided occurrence data for barium. These data
consist of 183,118 analytical results from 49,125 systems during the period from 1998 to 2005.
The number of sample results and systems vary by state, although the state data sets have been
reviewed and checked to ensure adequacy of coverage and completeness.
8.4.1 Stage 1A nalysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 8-3
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For barium, 72.020% of 49,125 systems reported
detections. Exhibit 8-4 lists the minimum, median, 90th percentile, and maximum barium
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of barium, based on detections from all systems, is 0.05 mg/L.
Exhibit 8-3: Barium Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
142,438
45,118
85,388,860
Surface Water
40,680
4,007
144,386,847
Combined Ground &
Surface Water
183,118
49,125
229,775,707
Percent with Detections
Ground Water
62.814%
71.978%
82.897%
Surface Water
54.444%
72.498%
77.449%
Combined Ground &
Surface Water
60.955%
72.020%
79.473%
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Exhibit 8-4: Barium Summary Statistics
Source Water Type
Ground Water
Detection Value (mg/L)
Minimum
0.000086
Median
0.06
90tn
Percentile
0.23
Maximum
19
Surface Water
0.0001
0.04
0.15
19
Combined Ground &
Surface Water
0.000086
0.05
0.21
19
The following maps illustrate the geographic distribution of barium occurrence in
drinking water. Exhibit 8-5 shows the states with systems with at least one detection and Exhibit
8-6 shows the states with systems with at least one detection greater than the MCL concentration.
Note that five states did not submit data for use in the Six-Year Review (Kansas3, Louisiana,
Mississippi, Pennsylvania, and Washington).
Detection rates were high for barium and the distribution of systems with detections of
barium is geographically dispersed. In 17 states, more than 90% of systems detected barium. In
three states, more than 0.5% of systems reported at least one detection greater than the MCL
concentration of 2 mg/L.
3 Kansas submitted data after the data management and analyses had been conducted; data from Kansas are not
included in the analyses.
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Exhibit 8-5: Percentage of Systems with at Least One Barium Detection,
by State
States Not Submitting Any Data
States with No Detections
Less than 50% of Systems Detecting
Between 50% and 90% of Systems Detecting
More than 90% of Systems Detecting
Exhibit 8-6: Percentage of Systems with at Least One Barium Detection Greater
than the MCL Concentration (> 2 mg/L), by State
States Not Submitting Any Data
States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
| Between 0.1% and 0.5% of Systems with Detections > MCL
| More than 0.5% of Systems with Detections > MCL
Exhibit 8-7 presents the Stage 1 analysis of barium occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
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two thresholds: 1 mg/L and 2 mg/L. A total of 240 (0.489% of) systems, serving more than
820,000 persons, reported at least one detection greater than or equal to 1 mg/L; and 66 (0.134%
of) systems, serving more than 211,000 persons, reported at least one detection greater than 2
mg/L.
Exhibit 8-7: Barium Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 2 mg/L
> 1 mg/L
Number of
Systems
Exceeding
Threshold
61
225
Percent of
Systems
Exceeding
Threshold
0.135%
0.499%
Total Population-
Served by
Systems
Exceeding
Threshold
189,533
609,877
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.222%
0.714%
Surface
Water
> 2 mg/L
> 1 mg/L
5
15
0.125%
0.374%
21,575
211,283
0.015%
0.146%
Combined
Ground &
Surface
Water
> 2 mg/L
> 1 mg/L
66
240
0.134%
0.489%
211,108
821,160
0.092%
0.357%
8.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2007. ToxFAQs for Barium.
August 2007. Available on the Internet at: http://www.atsdr.cdc.gov/tfacts24.html.
Klein, C. and C.S. Hurlbut (after J.D. Dana). 1993. Manual of Mineralogy (21st edition). John
Wiley and Sons.
United States Environmental Protection Agency (USEPA). 1991. Drinking Water; National
Primary Drinking Water Regulations; Monitoring for Volatile Organic Chemicals; MCLGs and
MCLs for Aldicarb, Aldicarb Sulfoxide, Aldicarb Sulfone, Pentachlorophenol, and Barium; Final
Rule. Federal Register. Vol. 56, No. 126. p. 30266, July 1, 1991.
USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - Barium. Last modified September 10, 2007. Available on the Internet at:
http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for barium.] Accessed February
21,2008.
USEPA. 2008a. TRI Explorer: Trends - Barium. Released February 21, 2008. Available on the
Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for barium.] Accessed March 4,
2008.
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USEPA. 2008b. TRI Explorer: Trends - Barium Compounds. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for barium
compounds.] Accessed March 4, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
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9 Benzo(a)pyrene
This chapter on benzo(a)pyrene is part of a report that is organized so that each chapter
presents information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and
benzo(a)pyrene occurrence estimates in ambient water and drinking water. All drinking water
occurrence estimates were based on data from the National Compliance Monitoring Information
Collection Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR
Dataset"). For detailed information regarding this dataset, data management, data quality
assessments, and the analytical approach used to generate all contaminant occurrence estimates
presented in this chapter, please refer to USEPA (2009).
9.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for benzo(a)pyrene on July 17, 1992
(57 FR 31776 (USEPA, 1992)). The NPDWR established a maximum contaminant level goal
(MCLG) of zero based on a cancer classification of B2, probable human carcinogen. The
NPDWR also established a maximum contaminant level (MCL) of 0.2 |ig/L based on analytical
method feasibility.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 1995),
benzo(a)pyrene (C2oHi2) is one of a group of compounds called polycyclic aromatic
hydrocarbons (PAHs). It is largely associated with soils, particulate matter, and sediments; it
does not readily leach. In soils, degradation takes weeks to months and is caused primarily by
microbial activity. In water, it is susceptible to degradation by sunlight (ATSDR, 1995).
9.2 Use, Production, and Releases
PAHs are very common because they are formed naturally as a result of incomplete
combustion of organic materials. Although they can be manufactured as individual compounds
for research purposes, they are not manufactured as the mixtures found in combustion products.
There is no known use for benzo(a)pyrene except as a research chemical (ATSDR, 1995).
The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for benzo(a)pyrene.
Benzo(a)pyrene is not listed as a Toxics Release Inventory (TRI) chemical; thus, no TRI
release records are available.
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9.3 Occurrence in Ambient Water
No National Water Quality Assessment (NAWQA) Program data are available from the
United States Geological Survey (USGS) on the occurrence of benzo(a)pyrene in ambient waters
from the Pesticide National Synthesis Project (Gilliom et a/., 2007) or the EPA Summary
Analysis of Cycle 1 data.
9.4 Occurrence in Drinking Water
Benzo(a)pyrene is regulated as a synthetic organic chemical (SOC) in drinking water. All
non-purchased community water systems (CWSs) and non-transient non-community water
systems (NTNCWSs) are required to sample for SOCs. The maximum waiver period for SOCs is
three years, but this waiver can be renewed indefinitely. (Systems may receive a waiver at any
time without having collected an SOC sample. With a waiver, systems are not required to collect
an SOC sample.)
All CWSs and NTNCWSs without an SOC waiver must collect four consecutive
quarterly samples during the initial three-year compliance period. * If all four samples are non-
detections, then a system serving less than 3,300 persons may reduce to one sample during each
consecutive compliance period; a system serving more than 3,300 persons may reduce to two
quarterly samples within a 12-month period during a 3-year compliance period. If a chemical is
detected (but is less than the MCL), the system must take one sample per quarter until results are
below the MCL (minimum of two quarterly samples for ground water systems and four quarterly
samples for surface water systems). If all quarterly samples are below the MCL, the system may
return to annual sampling. If a chemical is detected at a level greater than the MCL, the system
(whether ground water or surface water) must take quarterly samples until four consecutive
quarters are below the MCL. If all quarterly samples are below the MCL, the system may return
to annual sampling.
The analysis of benzo(a)pyrene occurrence presented in the following section is based on
state compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and
most comprehensive compliance monitoring data set compiled by EPA's Drinking Water
Program to date.
Forty-three of the Six-Year Review-ICR states provided occurrence data for
benzo(a)pyrene. (There were no benzo(a)pyrene data from Hawaii or Oklahoma.) These data
consist of 119,871 analytical results from 28,578 public water systems (PWSs) during the period
from 1998 to 2005. The number of sample results and systems vary by state, although the state
data sets have been reviewed and checked to ensure adequacy of coverage and completeness.
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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9.4.1 Stage 1A nalysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 9-1
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For benzo(a)pyrene, 0.490% of 28,578 systems
reported detections. Exhibit 9-2 lists the minimum, median, 90th percentile, and maximum
benzo(a)pyrene concentrations based on detections from all systems in the Six-Year Review-ICR
Dataset. The median concentration of benzo(a)pyrene, based on detections from all systems, is
0.07
Exhibit 9-1: Benzo(a)pyrene Occurrence Data from the
Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
92,473
25,566
65,074,173
Surface Water
27,398
3,012
119,069,990
Combined Ground &
Surface Water
119,871
28,578
184,144,163
Percent with Detections
Ground Water
0.124%
0.399%
4.456%
Surface Water
0.201%
1 .262%
5.385%
Combined Ground &
Surface Water
0.142%
0.490%
5.057%
Exhibit 9-2: Benzo(a)pyrene Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.007
Median
0.06
90tn
Percentile
0.18
Maximum
1
Surface Water
0.01
0.1
0.34
0.54
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Source Water Type
Combined Ground &
Surface Water
Detection Value (ug/L)
Minimum
0.007
Median
0.07
90tn
Percentile
0.2
Maximum
1
The following maps illustrate the geographic distribution of benzo(a)pyrene occurrence in
drinking water. Exhibit 9-3 shows the states with systems with at least one detection and Exhibit
9-4 shows the states with systems with at least one detection greater than the MCL concentration.
Note that five states did not submit data for use in the Six-Year Review (Kansas2, Louisiana,
Mississippi, Pennsylvania, and Washington). Hawaii and Oklahoma did submit Six-Year data for
most contaminants, but did not submit data for benzo(a)pyrene.
Detection rates were generally low for benzo(a)pyrene. Seven states reported detections in
more than 1% of their systems. With the exception of Arizona, these states are all located in the
eastern part of the United States. In five states, between 0.5% and 1% of systems reported
detections. Fourteen states reported no detections, and 12 states reported detections greater than
the MCL concentration of 0.2 |ig/L.
Exhibit 9-3: Percentage of Systems with at Least One Benzo(a)pyrene Detection,
by State
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Exhibit 9-4: Percentage of Systems with at Least One Benzo(a)pyrene Detection
Greater than the MCL Concentration (> 0.2 ug/L), by State
Estates with Waivers or Not Submitting
States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
Between 0.1% and 0.5% of Systems with Detections > MCL
H More than 0.5% of Systems with Detections > MCL
Exhibit 9-5 presents the Stage 1 analysis of benzo(a)pyrene occurrence in drinking water
from systems and population-served by those systems in the Six-Year Review-ICR Dataset
relative to two thresholds: 0.1 |ig/L and 0.2 |ig/L. A total of 53 (0.185% of) systems, serving
almost 3 million persons, reported at least one detection greater than or equal to 0.1 |ig/L; and 14
(0.049% of) systems, serving almost 215,000 persons, reported at least one detection greater than
0.2|ig/L.
Exhibit 9-5: Benzo(a)pyrene Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 0.2 |jg/L
>0.1 |jg/L
Number of
Systems
Exceeding
Threshold
9
35
Percent of
Systems
Exceeding
Threshold
0.035%
0.137%
Total Population-
Served by
Systems
Exceeding
Threshold
12,087
69,321
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.019%
0.107%
Surface
Water
> 0.2 |jg/L
>0.1 |jg/L
5
18
0.166%
0.598%
202,896
2,899,838
0.170%
2.435%
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Source
Water
Type
Combined
Ground &
Surface
Water
Threshold
> 0.2 |jg/L
>0.1 |jg/L
Number of
Systems
Exceeding
Threshold
14
53
Percent of
Systems
Exceeding
Threshold
0.049%
0.185%
Total Population-
Served by
Systems
Exceeding
Threshold
214,983
2,969,159
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.117%
1.612%
9.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 1995. Toxicological Profile for
Poly cyclic Aromatic Hydrocarbons. August 1995. Available on the Internet at:
http://www.atsdr.cdc.gov/toxprofiles/tp69.pdf.
Gilliom, R.J., I.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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
United States Environmental Protection Agency (USEPA). 1992. Drinking Water; National
Primary Drinking Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals;
National Primary Drinking Water Regulations Implementation; Final Rule. Federal Register.
Vol. 57, No. 138. p. 31776, July 17, 1992.
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. Office of Water. EPA-815-B-09-006. October 2009.
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10 Beryllium
This chapter on beryllium is part of a report that is organized so that each chapter
presents information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and beryllium
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
10.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for beryllium on July 17, 1992 (57 FR
31776 (USEPA, 1992)). The NPDWR established a maximum contaminant level goal (MCLG)
and a maximum contaminant level (MCL) of 0.004 mg/L. EPA classified beryllium in Group B2,
probable human carcinogen, based on clear evidence of its carcinogenicity via inhalation or
injection in several animal species. However, EPA also placed beryllium in drinking water
Category II1 for regulation, based on the weight of evidence for carcinogenicity via ingestion,
and the potency, exposure and pharmacokinetics of this chemical. EPA derived the maximum
contaminant level goal (MCLG) by applying an additional risk management factor of 10 to the
RfD of 0.005 mg/kg-day (USEPA, 1992).
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2002),
beryllium is a hard, grayish metal. In nature, it is found in minerals, coal, soil, and volcanic dust.
Its primary ore mineral, beryl, is also known as the gemstones emerald (when green) and
aquamarine (when blue) (Klein and Hurlbut, 1993). Beryllium can be released into the air by
burning coal and soil. It poses a health risk from inhalation at high doses, although ambient
levels are low enough that the general public is unlikely to develop beryllium disease (ATSDR,
2002).
10.2 Use, Production, and Releases
Beryllium ores are commercially mined. The beryllium is purified for use in nuclear
weapons and reactors, aircraft and space vehicle structures, instruments, x-ray machines, and
mirrors. Beryllium ores are used to make specialty ceramics for electrical and high-technology
applications. Beryllium alloys are used in automobiles, computers, sports equipment (golf clubs
and bicycle frames), and dental bridges (ATSDR, 2002).
1 Note that this "Category II" classification for beryllium is different than it being a part of the group of 47 Category
2 contaminants discussed in this report.
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The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for beryllium.
Beryllium and beryllium compounds are listed as Toxics Release Inventory (TRI)
chemicals. TRI data indicate that total off-site and on-site releases of beryllium for the period
1998-2006 ranged from approximately 74,000 pounds to approximately 458,000 pounds, with an
increase over time. On-site releases were greater than off-site releases (USEPA, 2008a). Total
beryllium compound releases ranged from approximately 641,000 pounds to approximately
972,000 pounds, with a general decrease over time. Amounts released on-site were greater than
amounts released off-site (USEPA, 2008b).
10.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of beryllium in
ambient water are available from the NAWQA program.
10.3.1 EPA Summary Analysis of NAWQA Data
EPA, with the cooperation of the USGS, has performed a summary analysis of all Cycle
1 water monitoring data from all study units (1992-2001) for beryllium. Detection frequencies
were computed as the percentage of samples and sites with detections (i.e., with at least one
result equal to or greater than the reporting limit). Sample detections can be biased by frequent
sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 10-1. Overall, beryllium was
detected in 1.5% of samples and at 2.5% of sites. Beryllium was detected in similar percentages
of surface water and ground water sites. The median concentration based on detections from all
sites was 0.07 |ig/L (0.00007 mg/L). The 99th percentile concentration based on detections from
all sites was 18 |ig/L (0.018 mg/L).
Exhibit 10-1: EPA Summary Analysis of Beryllium Data from NAWQA Study Units,
1992-2001
ground
water
Detection Frequency
(detections are results > RL1)
Number
of
Samples
3,252
% Samples
with
Detections
2.2%
Number
of Sites
2,904
% Sites
with
Detections
2.4%
Concentration Values
(of detections, in ug/L)
Minimum
0.03
Median
0.0885
95th
Percen-
tile
7.535
99th
Percen-
tile
18
Maximum
18
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surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
2,379
5,631
% Samples
with
Detections
0.5%
1.5%
Number
of Sites
394
3,298
% Sites
with
Detections
2.8%
2.5%
Concentration Values
(of detections, in ug/L)
Minimum
0.032
0.03
Median
0.0445
0.07
95th
Percen-
tile
11
7.535
99th
Percen-
tile
11
18
Maximum
11
18
1. RLs (Reporting Limits) for beryllium varied, but did not exceed 0.032 pg/L.
10.4 Occurrence in Drinking Water
Beryllium is regulated as an inorganic chemical (IOC) in drinking water. All community
water systems (CWSs) and non-transient non-community water systems (NTNCWSs) are
required to sample for the IOCs.2 The maximum waiver period for lOCs is nine years.
Ground water systems must sample once during the initial three-year compliance period.
After three compliance periods without a detection, a ground water system may be granted a
nine-year waiver. Surface water systems must sample annually during the initial three-year
compliance period. After three annual samples without a detection, a surface water system may
be granted a nine-year waiver. If the results are greater than the MCL, the public water system
(PWS) must take one sample per quarter until results are below the MCL (minimum of two
quarterly samples for ground water systems and four quarterly samples for surface water
systems).3 If all quarterly samples are below the MCL, the system may continue at initial
monitoring indefinitely until the state or EPA establishes an alternate schedule.
The analysis of beryllium occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
All of the Six-Year Review-ICR states provided occurrence data for beryllium. These
data consist of 183,575 analytical results from 48,021 systems during the period from 1998 to
2005. The number of sample results and systems vary by state, although the state data sets have
been reviewed and checked to ensure adequacy of coverage and completeness.
2 Nitrate and nitrite have their own monitoring requirements. See the nitrate and nitrite chapters for details of those
requirements.
3 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the
MCL.
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10.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 10-2
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For beryllium, 3.117% of 48,021 systems reported
detections. Exhibit 10-3 lists the minimum, median, 90th percentile, and maximum beryllium
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of beryllium, based on detections from all systems, is 0.0005 mg/L.
Exhibit 10-2: Beryllium Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
143,332
44,015
84,495,418
Surface Water
40,243
4,006
136,888,401
Combined Ground &
Surface Water
183,575
48,021
221,383,819
Percent with Detections
Ground Water
1.348%
2.992%
11.296%
Surface Water
0.825%
4.493%
15.313%
Combined Ground &
Surface Water
1 .233%
3.117%
13.780%
Exhibit 10-3: Beryllium Summary Statistics
Source Water Type
Ground Water
Detection Value (mg/L)
Minimum
0.000021
Median
0.0004
90tn
Percentile
0.003
Maximum
0.14
Surface Water
0.000021
0.001
0.002
0.05
Combined Ground &
Surface Water
0.000021
0.0005
0.003
0.14
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The following maps illustrate the geographic distribution of beryllium occurrence in
drinking water. Exhibit 10-4 shows the states with systems with at least one detection and
Exhibit 10-5 shows the states with systems with at least one detection greater than the MCL
concentration. Note that five states did not submit data for use in the Six-Year Review (Kansas4,
Louisiana, Mississippi, Pennsylvania, and Washington).
The distribution of systems with detections of beryllium is geographically dispersed. In
10 states, more than 5% of systems detected beryllium. In 19 states, between 1% and 5% of
systems reported detections. Twenty-five states reported no detections of beryllium greater than
the MCL concentration of 0.004 mg/L. In four states, more than 0.5% of systems reported at least
one detection greater than 0.004 mg/L.
Exhibit 10-4: Percentage of Systems with at Least One Beryllium Detection,
by State
////A States Not Submitting Any Data
States with No Detections
Less than 1% of Systems Detecting
^BJ Between 1% and 5% of Systems Detecting
^B More than 5% of Systems Detecting
4 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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Exhibit 10-5: Percentage of Systems with at Least One Beryllium Detection
Greater than the MCL Concentration (> 0.004 mg/L), by State
Estates Not Submitting Any Data
States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
Between 0.1% and 0.5% of Systems with Detections > MCL
H More than 0.5% of Systems with Detections > MCL
Exhibit 10-6 presents the Stage 1 analysis of beryllium occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 0.002 mg/L and 0.004 mg/L. A total of 250 (0.521% of) systems, serving about
5.8 million persons, reported at least one detection greater than or equal to 0.002 mg/L; and 53
(0.110% of) systems, serving almost 3.1 million persons, reported at least one detection greater
than 0.004 mg/L.
Exhibit 10-6: Beryllium Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 0.004 mg/L
> 0.002 mg/L
Number of
Systems
Exceeding
Threshold
41
202
Percent of
Systems
Exceeding
Threshold
0.093%
0.459%
Total Population-
Served by
Systems
Exceeding
Threshold
148,433
1,453,696
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.176%
1.720%
Surface
Water
> 0.004 mg/L
> 0.002 mg/L
12
48
0.300%
1.198%
2,918,844
4,332,647
2.132%
3.165%
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Source
Water
Type
Combined
Ground &
Surface
Water
Threshold
> 0.004 mg/L
> 0.002 mg/L
Number of
Systems
Exceeding
Threshold
53
250
Percent of
Systems
Exceeding
Threshold
0.110%
0.521%
Total Population-
Served by
Systems
Exceeding
Threshold
3,067,277
5,786,343
Percent of
Population -Served
by Systems
Exceeding
Threshold
1.386%
2.614%
10.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2002. ToxFAQs for Beryllium.
September 2002. Available on the Internet at: http://www.atsdr.cdc.gov/tfacts4.html.
Klein, C. and C.S. Hurlbut (after J.D. Dana). 1993. Manual of Mineralogy (21st edition). John
Wiley and Sons.
United States Environmental Protection Agency (USEPA). 1992. Drinking Water; National
Primary Drinking Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals;
National Primary Drinking Water Regulations Implementation; Final Rule. Federal Register.
Vol. 57, No. 138. p. 31776, July 17, 1992.
USEPA. 2008a. TRI Explorer: Trends - Beryllium. Released February 21, 2008. Available on
the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for beryllium.] Accessed
March 6, 2008.
USEPA. 2008b. TRI Explorer: Trends - Beryllium Compounds. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for beryllium
compounds.] Accessed March 6, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
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11 Beta Particles and Photon Emitters
This chapter on beta particles and photon emitters is part of a report that is organized so
that each chapter presents information on one specific contaminant. Chapter 1 of this report,
Introduction, presents background information on all sources of data used as well as the
analytical approach used to estimate contaminant occurrence in drinking water. This contaminant
chapter includes background information (such as regulatory history, general chemical
information, and environmental fate and behavior), use and environmental release information,
and beta particle occurrence estimates in ambient water and drinking water. All drinking water
occurrence estimates were based on data from the National Compliance Monitoring Information
Collection Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR
Dataset"). For detailed information regarding this dataset, data management, data quality
assessments, and the analytical approach used to generate all contaminant occurrence estimates
presented in this chapter, please refer to USEPA (2009).
11.1 Background
EPA published an interim Drinking Water Regulation for the sum of the doses from man-
made beta particles and photon emitters on July 9, 1976 (41 FR 28402 (USEPA, 1976)). The
Maximum Contaminant Level (MCL) that was established was a concentration that produces a
dose equivalent of 50 pCi/L or less to the total body or any internal organ for the sum of the
doses from man-made beta particles and photon emitters. A total of 168 individual beta particle
and photon emitters may be used to calculate compliance with the MCL (USEPA, 2001). The
beta particles and photon emitters include: cesium-137, cobalt-60, iodine-129 &-131, plutonium,
strontium-90, technetium-99, and tritium, in addition to another 160 individual beta particle and
photon emitters. In 2000, EPA published the final National Primary Drinking Water Regulations
(NPDWR) for radionuclides. The MCL for beta particles and photon emitters remained at 4
mrem/yr.l The 2000 rule set a Maximum Contaminant Level Goal (MCLG) for beta particles at
zero (USEPA, 2000).
Beta particle and photon radioactivity may occur due to contamination from facilities
using or producing radioactive materials (USEPA, 2006). The decay of natural and man-made
deposits of certain minerals that are radioactive may emit a form of radiation known as photons
and beta radiation (USEPA, 2008a). Three regulated beta emitters - iodine-131, strontium-90,
and tritium - are described in more detail below. Data for these three beta emitters are available
in the Six Year Review-ICR Dataset but occurrence results were not included in this report.
Iodine-131
According to USEPA (2008b), iodine-131 is produced by the fission of uranium atoms
during operation of nuclear reactors and by plutonium (or uranium) in the detonation of nuclear
1 Although the MCL for beta particles, 4 millirem per year (mrem/yr), is in the unit of measure of mrem/yr, the
primary unit of analytical measure is picocuries per liter (pCi/L). This unit of measure relates to screening thresholds
of 15 pCi/L and 50 pCi/L that are defined in the 2000 Radionuclides Rule.
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weapons. It has a half-life of about eight days and emits beta particles upon radioactive decay
(USEPA, 2008b).
Radioactive iodines have the same physical properties as stable iodine; yet, radioactive
iodines decay with time. Iodine is a nonmetallic, purplish-black crystalline solid. It has the
unusual property of sublimation. It sublimes to a deep violet vapor at room temperature. This
vapor is irritating to the eyes, nose and throat. Iodine dissolves in alcohol and in water and melts
at 236 °F (USEPA, 2008b).
Iodine reacts easily with other chemicals, and isotopes of iodine are found as compounds
rather than as a pure elemental nuclide. Thus, iodine-131 found in nuclear facilities and waste
treatment plants quickly forms compounds with the mixture of chemicals present. However,
iodine released to the environment from nuclear power plants is usually a gas (USEPA, 2008b).
Strontium-90
According to USEPA (2007a), strontium-90 (Sr-90) is a by-product of the fission of
uranium and plutonium in nuclear reactors, and in nuclear weapons. It is found in waste from
nuclear reactors and can also contaminate reactor parts and fluids. Large amounts of Sr-90 were
produced during atmospheric nuclear weapons tests conducted in the 1950's and 1960's and
dispersed worldwide (USEPA, 2007a).
Non-radioactive strontium and its radioactive isotopes have the same physical properties.
Strontium is a soft metal similar to lead. It is chemically very reactive, and is only found in
compounds in nature. When freshly cut, it has a silvery luster, but rapidly reacts with air and
turns yellow. Finely cut strontium will burst into flame in air. Because of these qualities, it is
generally stored in kerosene (USEPA, 2007a).
Sr-90 emits a beta particle with no gamma radiation, as it decays to yttrium-90 (also a
beta-emitter). Sr-90 has a half-life of about 29 years. It behaves chemically much like calcium,
and therefore tends to concentrate in the bones and teeth (USEPA, 2007a).
Tritium
According to USEPA (2007b), tritium is produced naturally in the upper atmosphere
when cosmic rays strike nitrogen molecules in the air. It is also produced during nuclear weapons
explosions, as a byproduct in reactors producing electricity, and in special production reactors,
where the isotope lithium-6 is bombarded to produce tritium (USEPA, 2007b).
Tritium is a hydrogen atom that has two neutrons in the nucleus, in addition to its single
proton, giving it an atomic weight near three. Although tritium can be a gas, its most common
form is in water, because, like non-radioactive hydrogen, radioactive tritium reacts with oxygen
to form water. Tritium replaces one of the stable hydrogens in the water molecule, ttO, and is
called tritiated water. Like H2O, tritiated water is colorless and odorless. Tritium has a half-life of
about 12 years and emits a very weak beta particle (USEPA, 2007b).
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11.2 Use, Production, and Releases
As beta particles occur naturally with decay of natural and man-made deposits of certain
minerals that are radioactive, data for use, production, and release are not available. Use,
production, and release data for three regulated beta emitters - iodine-131, strontium-90, and
tritium - are described in more detail below.
Iodine-131
Iodines are among the most widely used radionuclides, used mostly in the medical field.
Because of its short half-life and useful beta emission, iodine-131 is used extensively in nuclear
medicine. Its tendency to collect in the thyroid gland makes iodine especially useful for
diagnosing and treating thyroid problems. Iodine's chemical properties make it easy to attach to
molecules for imaging studies. It is useful in tracking the metabolism of drugs or compounds, or
for viewing structural defects in various organs, such as the heart (USEPA, 2008b).
Strontium-90
Strontium-90 is used as a radioactive tracer in medical and agricultural studies. The heat
generated by Sr-90's radioactive decay can be converted to electricity for long-lived, portable
power supplies. These are often used in remote locations, such as in navigational beacons,
weather stations, and space vehicles (USEPA, 2007a).
Sr-90 is also used in electron tubes, as a radiation source in industrial thickness gauges,
and for the treatment of eye diseases. Controlled amounts of Sr-90 have been used as a treatment
for bone cancer (USEPA, 2007a).
Tritium
Tritium has several important uses. Its most significant use is as a component in the
triggering mechanism in thermonuclear (fusion) weapons. Very large quantities of tritium are
required for the maintenance of our nation's nuclear weapons capabilities (USEPA, 2007b).
Tritium is also produced commercially in reactors. It is used in various self-luminescent
devices, such as exit signs in buildings, aircraft dials, gauges, luminous paints, and wristwatches.
Tritium is also used in life science research, and in studies investigating the metabolism of
potential new drugs (USEPA, 2007b).
11.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of beta particles
in ambient water are available from the NAWQA program.
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11.3.1 EPA Summary Analysis ofNAWQA Data
EPA, with the cooperation of the USGS, has performed a summary analysis of all Cycle 1
water monitoring data from all study units (1992-2001) for beta particles. Detection frequencies
were computed as the percentage of samples and sites with detections (i.e., with at least one
result equal to or greater than the reporting limit). Sample detections can be biased by frequent
sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 11-1. Overall, beta particles were
detected in 53.0% of samples and at 52.3% of sites. Beta particles were detected in all 10 surface
water samples and 51.9% of the 418 ground water samples. The median beta particle
concentration based on detections from all sites was about 7.1 pCi/L. The 99th percentile
concentration based on detections from all sites was about 82 pCi/L.
Exhibit 11-1: EPA Summary Analysis of Beta Particles Data from NAWQA Study
Units, 1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
418
10
428
% Samples
with
Detections
51.9%
100.0%
53.0%
Number
of Sites
414
5
419
% Sites
with
Detections
51.7%
100.0%
52.3%
Concentration Values
(of detections, in pCi/L)
Minimum
1.1
4.49
1.1
Median
7.1
15.5
7.117
95th
Percen-
tile
36.48
35
36
99th
Percen-
tile
82.22
35
82.22
Maximum
652.82
35
652.82
1. RLs (Reporting Limits) for beta particle activity varied, but did not exceed 4.5 pCi/L
11.4 Occurrence in Drinking Water
Under the original radionuclides rule, all surface water community water systems (CWSs)
serving more than 100,000 persons, as well as other CWSs as specified by the state, were
required to sample for beta particle measurement. Initially, all CWSs must collect four
consecutive quarterly samples or the composite of four consecutive quarterly samples. If the
annual average particle activity of the initial sampling is less than 50 pCi/L, a system may reduce
to one sample every four years. If the annual average is greater than 50 pCi/L, the sample must be
analyzed to identify the major radioactive constituents present, and the appropriate internal organ
and total body doses must be calculated. If the annual average beta particle activity is greater than
the MCL, the system must take one sample each quarter until the annual average is below the
MCL or until the state sets an alternate monitoring schedule.
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If the average annual activity of tritium is greater than 20,000 pCi/L, and strontium-90 is
greater than 8 pCi/L, or if both radionuclides are present and the sum of annual dose equivalents
to total body or bone marrow is greater than 4 mrem/year, the system is out of compliance.
If a system is using water contaminated by effluents from a nuclear facility, and if beta
particle activity is greater than 15 pCi/L, the system may be required to monitor quarterly for
strontium-89 (limit is 80 pCi/L), cesium-134 (limit is 80 pCi/L), and iodine-131 (limit is 3
pCi/L). The average annual concentration of man-made radionuclides must not produce an
annual dose equivalent to the total body or any internal organ greater than 4 millirem/year.
Under the new radionuclides rule, all CWSs designated by the state as vulnerable or
contaminated (i.e., utilizing waters contaminated by effluents from nuclear facilities) are required
to sample for beta particle activity.
CWSs designated by the state as vulnerable must collect four consecutive quarterly
samples for beta emitters. "Quarterly" monitoring for gross beta is based on the analysis of
monthly samples or the analysis of a three month composite of samples. Vulnerable CWSs must
also collect annual samples for tritium and strontium-90. "Annual" samples must be collected
quarterly and analyzed or composited and analyzed. Sampling must begin within one quarter
after the quarter in which the CWS is notified by the state. If the beta particle activity minus the
naturally occurring potassium-40 beta particle activity has a running annual average less than or
equal to 50 pCi/L (screening level), the system may reduce sampling to once every three years.
CWSs utilizing waters contaminated by effluents from nuclear facilities must collect four
consecutive quarterly samples for beta emitters and iodine-131 as well as annual samples for
tritium and strontium-90 (the quarterly and annual monitoring requirements noted for vulnerable
systems are also applicable to contaminated systems). Sampling must begin within one quarter
after the quarter in which the system is notified by the state. If the beta particle activity minus the
naturally occurring potassium-40 beta particle activity has a running annual average (computed
quarterly) less than or equal to 15 pCi/L (screening level), the system may reduce sampling to
once every three years.
For both vulnerable and contaminated systems, if a sample is greater than the screening
level, the system must further analyze the sample for the major radioactive constituents and
determine compliance with the MCLs for beta particle and photon radioactivity using the "sum of
the fractions" calculation outlined in 40 CFR 141.66(d)(2). If the results show an MCL violation
for any of the constituents, the system must conduct monthly monitoring at any sampling point
that exceeds the MCL beginning the month after the exceedance occurs. A system can resume
quarterly monitoring if the running annual of three months of samples is at or below the MCL.
The analysis of beta particle occurrence presented in the following section is based on
state compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and
most comprehensive compliance monitoring data set compiled by EPA's Drinking Water
Program to date.
Beta particle data were provided by 34 of the Six-Year Review-ICR states. (No data were
received from Florida, Georgia, Hawaii, Maine, Michigan, North Dakota, Nebraska, New
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Hampshire, Oklahoma, and South Carolina.) The beta particle data from the 34 states consist of
59,983 analytical results from 14,231 public water systems (PWSs) during the period from 1998
to 2005. The number of sample results and systems vary by state, although the state data sets
have been reviewed and checked to ensure adequacy of coverage and completeness.
11.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 11-2
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For beta particles, 74.513% of 14,231 systems reported
detections. Exhibit 11-3 lists the minimum, median, 90th percentile, and maximum beta particle
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of beta particles, based on detections from all systems, is 5.2 pCi/L.
Exhibit 11-2: Summary of Beta Particles Occurrence Data from the Six-Year
Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
48,622
12,505
31,262,033
Surface Water
11,361
1,726
89,012,891
Combined Ground &
Surface Water
59,983
14,231
120,274,924
Percent with Detections
Ground Water
65.143%
72.971%
80.112%
Surface Water
61.685%
85.689%
89.231%
Combined Ground &
Surface Water
64.488%
74.513%
86.861%
Exhibit 11-3: Beta Particles Summary Statistics
Source Water Type
Ground Water
Detection Value (pCi/L)
Minimum
0.00001
Median
5.8
90tn
Percentile
17.8
Maximum
340.5
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Source Water Type
Surface Water
Detection Value (pCi/L)
Minimum
0.003
Median
4
90tn
Percentile
9.06
Maximum
488
Combined Ground &
Surface Water
0.00001
5.2
16.09
488
The following maps illustrate the geographic distribution of beta particle occurrence in
drinking water. Exhibit 11-4 shows the states with systems with at least one detection and
Exhibit 11-5 shows the states with systems with at least one detection greater than the screening
level of 50 pCi/L.2 Note that five states did not submit any data for use in the Six-Year Review
(Kansas3, Louisiana, Mississippi, Pennsylvania, and Washington). Florida, Georgia, Hawaii,
Maine, Michigan, North Dakota, Nebraska, New Hampshire, Oklahoma, and South Carolina
submitted Six-Year data for most contaminants, but did not submit data for of beta particles.
The distribution of systems with detections of beta particles is geographically dispersed
and detection rates were relatively high. In 15 states, more than 90% of systems reported
detections of beta particles. In seven states, more than 1% of systems reported at least one
detection greater than the screening level of 50 pCi/L.
Although the MCL for beta particles, 4 millirem per year (mrem/yr), is in the unit of measure of mrem/yr, the
primary unit of analytical measure is picocuries per liter (pCi/L). This unit of measure relates to screening thresholds
of 15 pCi/L and 50 pCi/L that are defined in the 2000 Radionuclides Rule. More than 95% of all compliance
monitoring data for beta particles submitted by the states to EPA were in units of pCi/L. The analyses presented here
are based on compliance monitoring data represented in units of pCi/L and are conducted relative to the screening
threshold of 50 pCi/L.
3 Kansas submitted data after the data management and analyses had been conducted; data from Kansas are not
included in the analyses.
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Exhibit 11-4: Percentage of Systems with at Least One Beta Particles Detection,
by State
'///A States with Waivers or Not Submitting
States with No Detections
| Less than or Equal to 50% of Systems Detecting
| Between 50% and 90% of Systems Detecting
I More than 90% of Systems Detecting
Exhibit 11-5: Percentage of Systems with at Least One Beta Particles Detection
Greater than 50 pCi/L, by State
: States with Waivers or Not Submitting
States with No Detections > 50 pCi/L
Less than ^ % of Systems with Detections > 50 pCI/L
| Between 1% and 5% of Systems with Detections > 50 pCi/L
| More than 5% of Systems with Detections > 50 pCi/L
Exhibit 11-6 presents the Stage I analysis of beta particle occurrence in drinking water
from systems and populations served by those systems in the Six-Year Review-ICR Dataset
relative to two thresholds: 25 pCi/L and 50 pCi/L. A total of 335 (2.354% of) systems, serving
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almost 9.7 million persons, reported at least one detection greater than or equal to 25 pCi/L; and
75 (0.527% of) systems, serving almost 1.5 million persons, reported at least one detection
greater than 50 pCi/L.
Exhibit 11-6: Beta Particles Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 50 pCi/L
> 25 pCi/L
Number of
Systems
Exceeding
Threshold
68
302
Percent of
Systems
Exceeding
Threshold
0.544%
2.415%
Total Population-
Served by
Systems
Exceeding
Threshold
540,849
1,662,946
Percent of
Population -Served
by Systems
Exceeding
Threshold
1.730%
5.319%
Surface
Water
> 50 pCi/L
> 25 pCi/L
7
33
0.406%
1.912%
936,487
7,998,101
1.052%
8.985%
Combined
Ground &
Surface
Water
> 50 pCi/L
> 25 pCi/L
75
335
0.527%
2.354%
1,477,336
9,661,047
1 .228%
8.032%
11.5 References
United States Environmental Protection Agency (USEPA). 1976. Title 40—Protection of
Environment. Chapter 1—Environmental Protection Agency. Part 141—Interim Primary Drinking
Water Regulations. Promulgation of Regulations on Radionuclides. Federal Register, Vol. 41,
No. 133, p. 28402, July 9, 1976.
USEPA. 2000. National Primary Drinking Water Regulations; Radionuclides; Final Rule.
Federal Register. Vol. 65, No. 236. p. 76707, December 7, 2000.
USEPA. 2001. Radionuclides Rule: A Quick Reference Guide. EPA-816-F-01-003, June 2001.
Available on the Internet at:
http://www.epa.gov/safewater/radionuclides/pdfs/qrg radionuclides.pdf
USEPA. 2006. Basic Information about Radionuclides in Drinking Water. Last modified
September 19, 2006. Available on the Internet at:
http://www.epa.gov/safewater/radionuclides/basicinformation.html. Accessed March 18, 2008.
USEPA. 2007a. Radiation Protection: Strontium-90. Last modified November 13, 2007.
Available on the Internet at: http://www.epa.gov/radiation/radionuclides/strontium.html.
Accessed March 18, 2008.
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USEPA. 2007b. Radiation Protection: Tritium. Last modified November 15, 2007. Available on
the Internet at: http://www.epa.gov/radiation/radionuclides/uranium.html. Accessed March 18,
2008.
USEPA. 2008a. Drinking Water Contaminants. Last modified February 15, 2008. Available on
the Internet at: http://www.epa.gov/safewater/contaminants/index.html. Accessed March 17,
2008.
USEPA. 2008b. Radiation Protection: Iodine. Last modified February 20, 2008. Available on the
Internet at: http://www.epa.gov/radiation/radionuclides/iodine.html. Accessed March 18, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
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12 Cadmium
This chapter on cadmium is part of a report that is organized so that each chapter presents
information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and cadmium
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
12.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for cadmium on January 30, 1991 (56
FR 3526 (USEPA, 1991)). The NPDWR established a maximum contaminant level goal
(MCLG) and a maximum contaminant level (MCL) of 0.005 mg/L. Because of inadequate dose-
response data to determine whether it poses a carcinogenic hazard from oral exposure, the
Agency regulated cadmium as a Group D carcinogen, not classifiable as to human
carcinogenicity by the oral route of exposure. Therefore, EPA developed the MCLG for cadmium
based on the reference dose (RfD) of 0.0005 mg/kg-day.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 1999),
cadmium is a natural element in the earth's crust. All soils and rocks, including coal and mineral
fertilizers, contain some cadmium. It is usually found combined with other elements such as
oxygen (cadmium oxide), chlorine (cadmium chloride), or sulfur (cadmium sulfate, cadmium
sulfide). Some cadmium compounds are able to leach through soils to ground water. Cadmium
tends to accumulate in aquatic life (ATSDR, 1999).
12.2 Use, Production, and Releases
Cadmium is used for metal plating and coating operations, and plastics. It is also used in
nickel-cadmium and solar batteries and in pigments. Most cadmium used in the United States is
extracted during the production of other metals such as zinc, lead, and copper (ATSDR, 1999).
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 12-1 presents the production of cadmium in the United States from 1986 to 2002.
Note that the production of cadmium in the United States was only documented in the Chemical
Update System in 1998.
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Exhibit 12-1: Production of Cadmium in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
No reports
No reports
No reports
> 1 million - 10 million pounds
No reports
Source: USEPA, 2003
Cadmium and cadmium compounds are listed as Toxics Release Inventory (TRI)
chemicals. TRI data indicate that total off-site and on-site releases of cadmium for the period
1998-2006 ranged from approximately 698,000 pounds to approximately 2.8 million pounds,
with a decrease after 1999 and an increase after 2004. On-site releases were greater than off-site
releases (USEPA, 2008a). Total cadmium compound releases ranged from approximately 2.6
million pounds to approximately 13.3 million pounds, with a general decrease over time.
Amounts released on-site were greater than amounts released off-site (USEPA, 2008b).
12.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of cadmium in
ambient water are available from the NAWQA program.
12.3.1 EPA Summary Analysis of NAWQA Data
EPA, with the cooperation of the USGS, has performed a summary analysis of all Cycle 1
water monitoring data from all study units (1992-2001) for cadmium. Detection frequencies were
computed as the percentage of samples and sites with detections (i.e., with at least one result
equal to or greater than the reporting limit). Sample detections can be biased by frequent
sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 12-2. Overall, cadmium was
detected in 8.1% of samples and at 7.4% of sites. Cadmium was detected at a higher percentage
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of surface water sites than ground water sites. The median concentration based on detections
from all sites was 0.135 |ig/L (0.000135 mg/L). The 99th percentile concentration based on
detections from all sites was about 13 |ig/L (0.013 mg/L).
Exhibit 12-2: EPA Summary Analysis of Cadmium Data from NAWQA Study Units,
1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
3,399
3,345
6,744
% Samples
with
Detections
7.3%
8.9%
8.1%
Number
of Sites
3,005
469
3,474
% Sites
with
Detections
6.0%
16.2%
7.4%
Concentration Values
(of detections, in ug/L)
Minimum
0.018
0.018
0.018
Median
0.087
0.205
0.135
95th
Percen-
tile
4
9
8.375
99th
Percen-
tile
7.43
18
13.179
Maximum
9.363
18.244
18.244
1. RLs (Reporting Limits) for cadmium varied, but did not exceed O.OISpg/L
12.4 Occurrence in Drinking Water
Cadmium is regulated as an inorganic chemical (IOC) in drinking water. All community
water systems (CWSs) and non-transient non-community water systems (NTNCWSs) are
required to sample for the lOCs.l The maximum waiver period for lOCs is nine years.
Ground water systems must sample once during the initial three-year compliance period.
After three compliance periods without a detection, a ground water system may be granted a
nine-year waiver. Surface water systems must sample annually during the initial three-year
compliance period. After three annual samples without a detection, a surface water system may
be granted a nine-year waiver. If the results are greater than the MCL, the public water system
(PWS) must take one sample per quarter until results are below the MCL (minimum of two
quarterly samples for ground water systems and four quarterly samples for surface water
systems).2 If all quarterly samples are below the MCL, the system may continue at initial
monitoring indefinitely until the state or EPA establishes an alternate schedule.
The analysis of cadmium occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
1 Nitrate and nitrite have their own monitoring requirements. See the nitrate and nitrite chapters for details of those
requirements.
2 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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All of the Six-Year Review-ICR states provided occurrence data for cadmium. These data
consist of 181,667 analytical results from 48,920 systems during the period from 1998 to 2005.
The number of sample results and systems vary by state, although the state data sets have been
reviewed and checked to ensure adequacy of coverage and completeness.
12.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 12-3
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For cadmium, 5.605% of 48,920 systems reported
detections. Exhibit 12-4 lists the minimum, median, 90th percentile, and maximum cadmium
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of cadmium, based on detections from all systems, is 0.00054 mg/L.
Exhibit 12-3: Cadmium Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
141,170
44,928
85,335,776
Surface Water
40,497
3,992
144,349,594
Combined Ground &
Surface Water
181,667
48,920
229,685,370
Percent with Detections
Ground Water
2.360%
5.382%
14.395%
Surface Water
1.721%
8.116%
18.449%
Combined Ground &
Surface Water
2.217%
5.605%
16.943%
Exhibit 12-4: Cadmium Summary Statistics
Source Water Type
Ground Water
Detection Value (mg/L)
Minimum
0.000006
Median
0.0005
90tn
Percentile
0.004
Maximum
0.08
12-4
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Source Water Type
Detection Value (mg/L)
Minimum
Median
90tn
Percentile
Maximum
Surface Water
0.000007
0.000853
0.003
0.05
Combined Ground &
Surface Water
0.000006
0.00054
0.0035
0.08
The following maps illustrate the geographic distribution of cadmium occurrence in
drinking water. Exhibit 12-5 shows the states with systems with at least one detection and
Exhibit 12-6 shows the states with systems with at least one detection greater than the MCL
concentration. Note that five states did not submit data for use in the Six-Year Review (Kansas3,
Louisiana, Mississippi, Pennsylvania, and Washington).
The distribution of systems with detections of cadmium is geographically dispersed. In 18
states, more than 5% of systems detected cadmium. In seven states, more than 0.5% of systems
reported at least one detection greater than the MCL concentration of 0.005 mg/L.
Exhibit 12-5: Percentage of Systems with at Least One Cadmium Detection,
by State
-j///t States Not Submitting Any Data
States with No Detections
Less than 1% of Systems Detecting
^B Between 1% and 5% of Systems Detecting
^H More than 5% of Systems Detecting
3 Kansas submitted data after the data management and analyses had been conducted; data from Kansas are not
included in the analyses.
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Exhibit 12-6: Percentage of Systems with at Least One Cadmium Detection
Greater than the MCL Concentration (> 0.005 mg/L), by State
$%%. States Not Submitting Any Data
States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
^B Between 0.1% and 0.5% of Systems with Detections > MCL
^B More than 0.5% of Systems with Detections > MCL
Exhibit 12-7 presents the Stage 1 analysis of cadmium occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 0.0025 mg/L and 0.005 mg/L. A total of 466 (0.953% of) systems, serving almost
6 million persons, reported at least one detection greater than or equal to 0.0025 mg/L; and 134
(0.274% of) systems, serving almost 2.4 million persons, reported at least one detection greater
than 0.005 mg/L.
Exhibit 12-7: Cadmium Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 0.005 mg/L
> 0.0025 mg/L
Number of
Systems
Exceeding
Threshold
121
407
Percent of
Systems
Exceeding
Threshold
0.269%
0.906%
Total Population-
Served by
Systems
Exceeding
Threshold
497,363
1,710,771
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.583%
2.005%
Surface
Water
> 0.005 mg/L
> 0.0025 mg/L
13
59
0.326%
1 .478%
1,901,706
4,288,872
1.317%
2.971%
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Source
Water
Type
Combined
Ground &
Surface
Water
Threshold
> 0.005 mg/L
> 0.0025 mg/L
Number of
Systems
Exceeding
Threshold
134
466
Percent of
Systems
Exceeding
Threshold
0.274%
0.953%
Total Population-
Served by
Systems
Exceeding
Threshold
2,399,069
5,999,643
Percent of
Population -Served
by Systems
Exceeding
Threshold
1.045%
2.612%
12.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 1999. ToxFAQsfor Cadmium.
June 1999. Available on the Internet at: http://www.atsdr.cdc.gov/tfacts5.html.
United States Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - Cadmium. Last modified September 10, 2007. Available on the Internet at:
http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for cadmium.] Accessed February
21,2008.
USEPA. 2008a. TRI Explorer: Trends - Cadmium. Released February 21, 2008. Available on the
Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for cadmium.] Accessed March 5,
2008.
USEPA. 2008b. TRI Explorer: Trends - Cadmium Compounds. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for cadmium
compounds.] Accessed March 5, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
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13 Chromium (Total)
This chapter on chromium (total) is part of a report that is organized so that each chapter
presents information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and chromium
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
13.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for total chromium (Cr) on January 30,
1991 (56 FR 3526 (USEPA, 1991)). The NPDWR established a maximum contaminant level
goal (MCLG) and maximum contaminant level (MCL) of 0.1 mg/L. Although the NPDWR
regulates total chromium, the adverse health effects associated with hexavalent chromium
(chromium VI) are the basis of the current MCLG because that is the more toxic species
(USEPA, 1991). EPA based the MCLG on a reference dose (RfD) of 0.005 mg/kg-day and an
assumed relative source contribution (RSC) from water of 70% for total chromium. EPA
regulated chromium as a Group D carcinogen, not classifiable as to human carcinogenicity by the
oral route of exposure.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2000),
chromium exists in three common stable valence states. In order of generally increasing toxicity,
these states are Cr (0), (HI), and (VI). In its elemental form (Cr(0)), chromium is a hard, blue-
white elemental metal. It is found in the earth's crust in minerals as Cr(IU). Chromium
compounds have no taste or odor (ATSDR, 2000).
Chromium typically enters the environment in either the Cr(UI) or Cr(VI) valence state.
The major sources of chromium to ground water include leaching from rocks, mineral deposits,
and mining and mill wastes. The two largest sources of chromium emission to the atmosphere are
the chemical manufacturing industry and the combustion of natural gas, oil, and coal. Chromium
tends to bind to soils strongly, though small amounts can dissolve in water and infiltrate into
aquifers (ATSDR, 2000).
13.2 Use, Production, and Releases
The use of chromium to produce stainless steel and nonferrous alloys are two of its more
important applications. Mixed with other metals, it can enhance hardenability and resistance to
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corrosion. Chromium is also used in bricks in furnaces, dyes and pigments, and for chrome
plating, leather tanning, and wood preserving (ATSDR, 2000).
The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for chromium.
Chromium and chromium compounds are listed as Toxics Release Inventory (TRI)
chemicals. TRI data indicate that total off-site and on-site releases of chromium for the period
1998-2006 ranged from approximately 10 million pounds to approximately 31 million pounds,
with an overall decrease over time. Off-site releases were greater than on-site releases for all
years except 1998 (USEPA, 2008a). Total chromium compound releases ranged from
approximately 50 million pounds to approximately 140 million pounds, with a general decrease
over time. Amounts released on-site were greater than amounts released off-site (USEPA,
2008b).
13.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of chromium in
ambient water are available from the NAWQA program.
13.3.1 EPA Summary Analysis of NAWQA Data
EPA, with the cooperation of the USGS, performed a summary analysis of all Cycle 1
water monitoring data from all study units (1992-2001) for chromium. Detection frequencies
were computed as the percentage of samples and sites with detections (i.e., with at least one
result equal to or greater than the reporting limit). Sample detections can be biased by frequent
sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 13-1. Overall, chromium was
detected in 47.2% of samples and at 61.1% of sites. Chromium was detected more frequently in
ground water than in surface water. The median concentration based on detections from all sites
is 2 |ig/L (0.002 mg/L). The 99th percentile concentration based on detections from all sites is
about 17.5 |ig/L (0.0175 mg/L).
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Exhibit 13-1: EPA Summary Analysis of Chromium Data from NAWQA Study
Units, 1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
3,341
2,610
5,951
% Samples
with
Detections
62.3%
28.0%
47.2%
Number
of Sites
2,967
418
3,385
% Sites
with
Detections
62.8%
48.6%
61.1%
Concentration Values
(of detections, in ug/L)
Minimum
0.402
0.4
0.4
Median
2.58
1.7115
2
95th
Percen-
tile
9
4.59
8
99th
Percen-
tile
19
10
17.4741
Maximum
148
89
148
1. RLs (Reporting Limits) for chromium varied, but did not exceed 0.4 pg/L
13.4 Occurrence in Drinking Water
Chromium is regulated as an inorganic chemical (IOC) in drinking water. All community
water systems (CWSs) and non-transient non-community water systems (NTNCWSs) are
required to sample for the lOCs.l The maximum waiver period for lOCs is nine years.
Ground water systems must sample once during the initial three-year compliance period.
After three compliance periods without a detection, a ground water system may be granted a
nine-year waiver. Surface water systems must sample annually during the initial three-year
compliance period. After three annual samples without a detection, a surface water system may
be granted a nine-year waiver. If the results are greater than the MCL, the public water system
(PWS) must take one sample per quarter until results are below the MCL (minimum of two
quarterly samples for ground water systems and four quarterly samples for surface water
systems).2 If all quarterly samples are below the MCL, the system may continue at initial
monitoring indefinitely until the state or EPA establishes an alternate schedule.
The analysis of chromium occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
All of the Six-Year Review-ICR states provided occurrence data for chromium. These
data consist of 185,952 analytical results from 48,908 systems during the period from 1998 to
2005. The number of sample results and systems vary by state, although the state data sets have
been reviewed and checked to ensure adequacy of coverage and completeness.
1 Nitrate and nitrite have their own monitoring requirements. See the nitrate and nitrite chapters for details of those
requirements.
2 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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13.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 13-2
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For chromium, 24.209% of 48,908 systems reported
detections. Exhibit 13-3 lists the minimum, median, 90th percentile, and maximum chromium
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of chromium, based on detections from all systems, is 0.00415 mg/L.
Exhibit 13-2: Chromium Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
143,094
44,905
85,254,121
Surface Water
42,858
4,003
144,374,309
Combined Ground &
Surface Water
185,952
48,908
229,628,430
Percent with Detections
Ground Water
15.696%
24.044%
40.204%
Surface Water
14.098%
26.055%
41.829%
Combined Ground &
Surface Water
15.328%
24.209%
41.226%
Exhibit 13-3: Chromium Summary Statistics
Source Water Type
Ground Water
Detection Value (mg/L)
Minimum
0.000009
Median
0.004
90tn
Percentile
0.01
Maximum
5.2
Surface Water
0.000009
0.006
0.02
0.32
Combined Ground &
Surface Water
0.000009
0.00415
0.01
5.2
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The following maps illustrate the geographic distribution of chromium occurrence in
drinking water. Exhibit 13-4 shows the states with systems with at least one detection and
Exhibit 13-5 shows the states with systems with at least one detection greater than the MCL
concentration. Note that five states did not submit data for use in the Six-Year Review (Kansas3,
Louisiana, Mississippi, Pennsylvania, and Washington).
The distribution of systems with detections of chromium is geographically dispersed.
Detection rates were high, with 8 states having greater than 50% of their systems detecting
chromium and another 25 states between 10% and 50% of systems with detections of chromium.
Only one state reported more than 0.5% of systems detecting chromium greater than the MCL
concentration of 0.1 mg/L.
Exhibit 13-4: Percentage of Systems with at Least One Chromium Detection,
by State
I
States Not Submitting Any Data
States with No Detections
Less than 10% of Systems Detecting
Between 10% and 50% of Systems Detecting
More than 50% of Systems Detecting
3 Kansas submitted data after the data management and analyses had been conducted; data from Kansas are not
included in the analyses.
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Exhibit 13-5: Percentage of Systems with at Least One Chromium Detection
Greater than the MCL Concentration (> 0.1 mg/L), by State
Estates Not Submitting Any Data
States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
Between 0.1% and 0.5% of Systems with Detections > MCL
H More than 0.5% of Systems with Detections > MCL
Exhibit 13-6 presents the Stage 1 analysis of chromium occurrence in drinking water
from systems and population-served by those systems in the Six-Year Review-ICR Dataset
relative to two thresholds: 0.05 mg/L and 0.1 mg/L. A total of 172 (0.352% of) systems, serving
almost 9.5 million persons, reported at least one detection greater than or equal to 0.05 mg/L; and
43 (0.088% of) systems, serving about 717,000 persons, reported at least one detection greater
than 0.1 mg/L.
Exhibit 13-6: Chromium Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 0.1 mg/L
> 0.05 mg/L
Number of
Systems
Exceeding
Threshold
37
144
Percent of
Systems
Exceeding
Threshold
0.082%
0.321%
Total Population-
Served by
Systems
Exceeding
Threshold
122,695
1,064,526
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.144%
1.249%
Surface
Water
> 0.1 mg/L
> 0.05 mg/L
6
28
0.150%
0.699%
593,922
8,424,108
0.411%
5.835%
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Source
Water
Type
Combined
Ground &
Surface
Water
Threshold
> 0.1 mg/L
> 0.05 mg/L
Number of
Systems
Exceeding
Threshold
43
172
Percent of
Systems
Exceeding
Threshold
0.088%
0.352%
Total Population-
Served by
Systems
Exceeding
Threshold
716,617
9,488,634
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.312%
4.132%
13.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2000. Toxicological Profile for
Chromium. September 2000. Available on the Internet at:
http://www.atsdr.cdc.gov/toxprofiles/tp7.html.
United States Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule Federal Register. Vol. 56, No. 30. p.
3526, January 30, 1991.
USEPA. 2008a. TRI Explorer: Trends - Chromium. Released February 21, 2008. Available on
the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for chromium.] Accessed
February 29, 2008.
USEPA. 2008b. TRI Explorer: Trends - Chromium Compounds. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for chromium
compounds.] Accessed February 29, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
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14 Cyanide
This chapter on cyanide is part of a report that is organized so that each chapter presents
information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and cyanide
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
14.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for cyanide on July 17, 1992 (57 FR
31776 (USEPA, 1992)). The NPDWR established a maximum contaminant level goal (MCLG)
and maximum contaminant level (MCL) of 0.2 mg/L. The MCLG was developed based on a
reference dose (RfD) of 0.02 mg/kg-day and a cancer classification of D, not classifiable as to
human carcinogenicity.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2006a),
cyanide is combined with other chemicals to form compounds. Some simple cyanide compounds
are hydrogen cyanide, sodium cyanide and potassium cyanide. Certain bacteria, fungi, and algae
can produce cyanide. In addition, cyanide is found in a number of foods and plants. In certain
plant foods (e.g., almonds, millet sprouts, lima beans, soy, spinach, bamboo shoots, and cassava
roots), cyanides occur naturally as part of sugars or other naturally-occurring compounds. Most
cyanide in the soil or water will form hydrogen cyanide and evaporate. In the soil, some cyanide
compounds will degraded by microorganisms. They do not bind to soils and may leach to ground
water when concentrations are toxic to microorganisms (ATSDR, 2006a).
14.2 Use, Production, and Releases
Hydrogen cyanide and other cyanides are used in electroplating, metallurgy, organic
chemicals production, photographic developing, manufacture of plastics, fumigation of ships,
and some mining processes. In recent years, there has been strong demand for the use of
hydrogen cyanide in nylon and other synthetic fibers. Other cyanides are used as herbicides
(ATSDR, 2006b).
The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for cyanide.
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Cyanide compounds are listed as Toxics Release Inventory (TRI) chemicals. TRI data
indicate that total off-site and on-site releases of cyanide compounds for the period 1998-2006
ranged from approximately 5.1 million pounds to approximately 9.9 million pounds, with a
decrease over time. On-site releases were greater than off-site releases (USEPA, 2008).
14.3 Occurrence in Ambient Water
No National Water Quality Assessment (NAWQA) Program data are available from the
United States Geological Survey (USGS) on the occurrence of cyanide in ambient waters from
the Pesticide National Synthesis Project (Gilliom et a/., 2007) or the EPA Summary Analysis of
Cycle 1 data.
14.4 Occurrence in Drinking Water
Cyanide is regulated as an inorganic chemical (IOC) in drinking water. All community
water systems (CWSs) and non-transient non-community water systems (NTNCWSs) are
required to sample for the lOCs.l The maximum waiver period for lOCs is nine years. (Statewide
waivers for cyanide may be granted if all systems in the state are required to chlorinate. Cyanide
waivers may also be granted if a state determines that a system is not vulnerable to cyanide
contamination due to a lack of industrial cyanide sources.)
Ground water systems must sample once during the initial three-year compliance period.
After three compliance periods without a detection, a ground water system may be granted a
nine-year waiver. Surface water systems must sample annually during the initial three-year
compliance period. After three annual samples without a detection, a surface water system may
be granted a nine-year waiver. If the results are greater than the MCL, the public water system
(PWS) must take one sample per quarter until results are below the MCL (minimum of two
quarterly samples for ground water systems and four quarterly samples for surface water
systems).2 If all quarterly samples are below the MCL, the system may continue at initial
monitoring indefinitely until the state or EPA establishes an alternate schedule.
The analysis of cyanide occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
Forty-four of the Six-Year Review-ICR states provided occurrence data for cyanide.
(There were no cyanide data from South Carolina.) These data consist of 120,368 analytical
results from 32,067 systems during the period from 1998 to 2005. The number of sample results
1 Nitrate and nitrite have their own monitoring requirements. See the nitrate and nitrite chapters for details of those
requirements.
2 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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and systems vary by state, although the state data sets have been reviewed and checked to ensure
adequacy of coverage and completeness.
14.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 14-1
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For cyanide, 4.144% of 32,067 systems reported
detections. Exhibit 14-2 lists the minimum, median, 90th percentile, and maximum cyanide
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of cyanide, based on detections from all systems, is 0.0089 mg/L.
Exhibit 14-1: Cyanide Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
93,931
29,277
66,122,477
Surface Water
26,437
2,790
96,336,123
Combined Ground &
Surface Water
120,368
32,067
162,458,600
Percent with Detections
Ground Water
1.559%
3.559%
14.736%
Surface Water
1.808%
10.287%
19.276%
Combined Ground &
Surface Water
1.613%
4.144%
17.428%
Exhibit 14-2: Cyanide Summary Statistics
Source Water Type
Ground Water
Detection Value (mg/L)
Minimum
0.0009
Median
0.009
90tn
Percentile
0.1
Maximum
1.93
Surface Water
0.001
0.0085
0.05
1.88
14-3
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source Water Type
Combined Ground &
Surface Water
Detection Value (mg/L)
Minimum
0.0009
Median
0.0089
90tn
Percentile
0.08
Maximum
1.93
The following maps illustrate the geographic distribution of cyanide occurrence in
drinking water. Exhibit 14-3 shows the states with systems with at least one detection and
Exhibit 14-4 shows the states with systems with at least one detection greater than the MCL
concentration. Note that five states did not submit data for use in the Six-Year Review (Kansas3,
Louisiana, Mississippi, Pennsylvania, and Washington). South Carolina did submit Six-Year data
for most contaminants, but did not submit cyanide data.
The distribution of systems with cyanide detections is geographically dispersed. Sixteen
states reported that more than 5% of systems detected cyanide. In three states, more than 0.5% of
systems reported at least one detection greater than the MCL concentration of 0.2 mg/L.
Exhibit 14-3: Percentage of Systems with at Least One Cyanide
Detection, by State
y/^ States with Waivers or Not Submitting
[ States with No Detections
Less than 1% of Systems Detecting
| Between 1% and 5% of Systems Detecting
^H More than 5% of Systems Detecting
3 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
14-4
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Exhibit 14-4: Percentage of Systems with at Least One Cyanide Detection Greater
than the MCL Concentration (> 0.2 mg/L), by State
Estates with Waivers or Not Submitting
States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
Between 0.1% and 0.5% of Systems with Detections > MCL
H More than 0.5% of Systems with Detections > MCL
Exhibit 14-5 presents the Stage 1 analysis of cyanide occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 0.1 mg/L and 0.2 mg/L. A total of 117 (0.365% of) systems, serving more than
1.8 million persons, reported at least one detection greater than or equal to 0.1 mg/L; and 44
(0.137% of) systems, serving almost 257,000 persons, reported at least one detection greater than
0.2 mg/L.
Exhibit 14-5: Cyanide Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 0.2 |jg/L
>0.1 |jg/L
Number of
Systems
Exceeding
Threshold
39
91
Percent of
Systems
Exceeding
Threshold
0.133%
0.311%
Total Population-
Served by
Systems
Exceeding
Threshold
222,909
546,722
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.337%
0.827%
Surface
Water
> 0.2 |jg/L
>0.1 |jg/L
5
26
0.179%
0.932%
33,999
1,304,404
0.035%
1.354%
14-5
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source
Water
Type
Combined
Ground &
Surface
Water
Threshold
> 0.2 |jg/L
>0.1 |jg/L
Number of
Systems
Exceeding
Threshold
44
117
Percent of
Systems
Exceeding
Threshold
0.137%
0.365%
Total Population-
Served by
Systems
Exceeding
Threshold
256,908
1,851,126
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.158%
1.139%
14.5 References
Agency for Toxic Substances or Disease Registry (ATSDR). 2006a. ToxFAQsfor Cyanide. July
2006. Available on the Internet at: http://www.atsdr.cdc.gov/tfacts8.html.
ATSDR. 2006b. Toxicological Profile for Cyanide. July 2006. Available on the Internet at:
http://www.atsdr.cdc.gov/toxprofiles/tp8.html.
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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
United States Environmental Protection Agency (USEPA). 1992. Drinking Water; National
Primary Drinking Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals;
National Primary Drinking Water Regulations Implementation; Final Rule. Federal Register.
Vol. 57, No. 138. p. 31776, July 17, 1992.
USEPA. 2008. TRI Explorer: Trends - Cyanide Compounds. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for cyanide
compounds.] Accessed March 5, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
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15 Dalapon
This chapter on dalapon (2,2-dichloropropionic acid) is part of a report that is organized
so that each chapter presents information on one specific contaminant. Chapter 1 of this report,
Introduction, presents background information on all sources of data used as well as the
analytical approach used to estimate contaminant occurrence in drinking water. This contaminant
chapter includes background information (such as regulatory history, general chemical
information, and environmental fate and behavior), use and environmental release information,
and dalapon occurrence estimates in ambient water and drinking water. All drinking water
occurrence estimates were based on data from the National Compliance Monitoring Information
Collection Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR
Dataset"). For detailed information regarding this dataset, data management, data quality
assessments, and the analytical approach used to generate all contaminant occurrence estimates
presented in this chapter, please refer to USEPA (2009).
15.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for dalapon on July 17, 1992 (57 FR
31776 (USEPA, 1992)). The NPDWR established a maximum contaminant level goal (MCLG)
and a maximum contaminant level (MCL) of 200 |ig/L. EPA developed the MCLG based on a
reference dose (RfD) of 30 jig/kg-day (0.03 mg/kg-day) and a cancer classification of D, not
classifiable as to human carcinogenicity.
According to the Extension Toxicology Network (EXTOXNET, 1996), in its pure acid
form, dalapon (CsFLjCbC^is a colorless liquid with an acrid odor. As sodium-magnesium salts,
it is a white to off-white powder. It will persist in soils for two to eight weeks. Dalapon leaches
readily; its mobility is limited due to breakdown by soil microbes. It is also readily broken down
by microbes in water. It tends not to accumulate in aquatic life (EXTOXNET, 1996).
15.2 Use, Production, and Releases
Dalapon is an herbicide used to control grasses in a wide variety of crops. The major crop
use for dalapon is on sugarcane and sugar beets. It is also used on fruits, potatoes, carrots,
asparagus, alfalfa and flax. It is also used in a number of non-crop applications such as lawns,
drainage ditches, along railroad tracks, and in industrial areas (EXTOXNET, 1996).
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 15-1 presents the production of dalapon in the United States from 1986 to 2002.
Note that the production of dalapon in the United States was only documented in the Chemical
Update System in 1986 and 1990 and was lower in the 1990.
15-1
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Exhibit 15-1: Production of Dalapon in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
> 10 million - 50 million pounds
10,000 - 500,000 pounds
No reports
No reports
No reports
Source: USEPA, 2003
Dalapon is not listed as a Toxics Release Inventory (TRI) chemical. Therefore, no TRI
release records are available.
15.3 Occurrence in Ambient Water
No National Water Quality Assessment (NAWQA) Program data are available from the
United States Geological Survey (USGS) on the occurrence of dalapon in ambient waters from
the Pesticide National Synthesis Project (Gilliom et a/., 2007) or the EPA Summary Analysis of
Cycle 1 data.
15.4 Occurrence in Drinking Water
Dalapon is regulated as a synthetic organic chemical (SOC) in drinking water. All non-
purchased community water systems (CWSs) and non-transient non-community water systems
(NTNCWSs) are required to sample for SOCs. The maximum waiver period for SOCs is three
years, but this waiver can be renewed indefinitely. (Systems may receive a waiver at any time
without having collected an SOC sample. With a waiver, systems are not required to collect an
SOC sample.)
All CWSs and NTNCWSs without an SOC waiver must collect four consecutive
quarterly samples during the initial three-year compliance period.l If all four samples are non-
detections, then a system serving less than 3,300 persons may reduce to one sample during each
consecutive compliance period; a system serving more than 3,300 persons may reduce to two
quarterly samples within a 12-month period during a 3-year compliance period. If a chemical is
detected (but is less than the MCL), the system must take one sample per quarter until results are
below the MCL (minimum of two quarterly samples for ground water systems and four quarterly
samples for surface water systems). If all quarterly samples are below the MCL, the system may
return to annual sampling. If a chemical is detected at a level greater than the MCL, the system
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
15-2
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(whether ground water or surface water) must take quarterly samples until four consecutive
quarters are below the MCL. If all quarterly samples are below the MCL, the system may return
to annual sampling.
The analysis of dalapon occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
Dalapon data were provided by 42 of the Six-Year Review-ICR states. (No dalapon data
were received from Hawaii, New Hampshire, or Oklahoma.) The dalapon data from the 42 states
consist of 112,423 analytical results from 28,387 public water systems (PWSs) during the period
from 1998 to 2005. The number of sample results and systems vary by state, although the state
data sets have been reviewed and checked to ensure adequacy of coverage and completeness.
15.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 15-2
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For dalapon, 1.828% of 28,387 systems reported
detections. Exhibit 15-3 lists the minimum, median, 90th percentile, and maximum dalapon
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of dalapon, based on detections from all systems, is 1.6 |ig/L.
Exhibit 15-2: Dalapon Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
88,908
25,558
64,625,469
Surface Water
23,515
2,829
113,560,642
Combined Ground &
Surface Water
112,423
28,387
178,186,111
Percent with Detections
Ground Water
0.733%
1.471%
6.168%
Surface Water
1.905%
5.055%
8.451%
15-3
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Combined Ground &
Surface Water
0.978%
1.828%
7.623%
Exhibit 15-3: Dalapon Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.01
Median
1.7
90tn
Percentile
6.6
Maximum
1,210
Surface Water
0.04
1.4
3.2
83
Combined Ground &
Surface Water
0.01
1.6
5
1,210
The following maps illustrate the geographic distribution of dalapon occurrence in
drinking water. Exhibit 15-4 shows the states with systems with at least one detection and
Exhibit 15-5 shows the states with systems with at least one detection greater than the MCL
concentration. Note that five states did not submit data for use in the Six-Year Review (Kansas2,
Louisiana, Mississippi, Pennsylvania, and Washington). Hawaii, New Hampshire, and Oklahoma
submitted Six-Year data for most contaminants, but did not submit data for dalapon.
Detection rates were generally low; 11 states reported detections in more than 1% of their
systems. These states are all located in the eastern half of the United States, as well as the
northern Midwest. In six states, between 0.5% and 1% of systems reported detections. Missouri
was the only state that reported detections greater than the MCL concentration of 200 |ig/L.
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas data are not
included in the analyses.
15-4
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 15-4: Percentage of Systems with at Least One Dalapon Detection,
by State
Estates with Waivers or Not Submitting
States with No Detections
Less than 0.5% of Systems Detecting
Between 0.5% and 1% of Systems Detecting
More than 1% of Systems Detecting
Exhibit 15-5: Percentage of Systems with at Least One Dalapon Detection Greater
than the MCL Concentration (> 200 ygIL), by State
States with Waivers or Not Submitting
States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
| Between 0.1% and 0.5% of Systems with Detections > MCL
| More than 0.5% of Systems with Detections > MCL
Exhibit 15-6 presents the Stage 1 analysis of dalapon occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
15-5
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
two thresholds: 100 |ig/L and 200 |ig/L. One ground water system, serving about 20,000 persons,
reported at least one detection greater than or equal to both thresholds. No surface water systems
reported detections exceeding either threshold.
Exhibit 15-6: Dalapon Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 200 |jg/L
>100|jg/L
Number of
Systems
Exceeding
Threshold
1
1
Percent of
Systems
Exceeding
Threshold
0.004%
0.004%
Total Population-
Served by
Systems
Exceeding
Threshold
20,114
20,114
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.031%
0.031%
Surface
Water
> 200 |jg/L
>100|jg/L
0
0
0.000%
0.000%
0
0
0.000%
0.000%
Combined
Ground &
Surface
Water
> 200 |jg/L
>100|jg/L
1
1
0.004%
0.004%
20,114
20,114
0.011%
0.011%
15.5 References
Extension Toxicology Network (EXTOXNET). 1996. EXTOXNET Pesticide Information
Profiles-Dalapon. Last modified June 1996. Available on the Internet at:
http://extoxnet.orst.edu/pips/dalapon.htm. Accessed July 6, 2008.
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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
United States Environmental Protection Agency (USEPA). 1992. Drinking Water; National
Primary Drinking Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals;
National Primary Drinking Water Regulations Implementation; Final Rule. Federal Register.
Vol. 57, No. 138. p. 31776, July 17, 1992.
USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - Dalapon. Last modified September 10, 2007. Available on the Internet at:
http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for dalapon.] Accessed February
21,2008.
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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. Office of Water. EPA-815-B-09-006. October 2009.
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16 Di(2-ethylhexyl)adipate (DEHA)
This chapter on di(2-ethylhexyl)adipate (DEHA) is part of a report that is organized so
that each chapter presents information on one specific contaminant. Chapter 1 of this report,
Introduction, presents background information on all sources of data used as well as the
analytical approach used to estimate contaminant occurrence in drinking water. This contaminant
chapter includes background information (such as regulatory history, general chemical
information, and environmental fate and behavior), use and environmental release information,
and di(2-ethylhexyl)adipate occurrence estimates in ambient water and drinking water. All
drinking water occurrence estimates were based on data from the National Compliance
Monitoring Information Collection Request (ICR) Dataset for the Second Six-Year Review (the
"Six Year Review-ICR Dataset"). For detailed information regarding this dataset, data
management, data quality assessments, and the analytical approach used to generate all
contaminant occurrence estimates presented in this chapter, please refer to USEPA (2009).
16.1 Background
The United States Environmental Protection Agency (EPA) published the National
Primary Drinking Water Regulations (NPDWR) for di(2-ethylhexyl)adipate on July 17, 1992 (57
FR 31776 (USEPA, 1992)). The NPDWR established a maximum contaminant level goal
(MCLG) and a maximum contaminant level (MCL) of 400 |ig/L. The Agency developed the
MCLG based on a reference dose (RfD) of 600 jig/kg-day (0.6 mg/kg-day) and a cancer
classification of C, possible human carcinogen.
According to the Hazardous Substance Data Bank (HSDB, 2008), di(2-ethylhexyl)adipate
(C22H42O/t) is a light-colored, oily liquid with a slight aromatic odor. Other names for di(2-
ethylhexyl)adipate include bis(2-ethylhexyl)adipate and DEHA. It tends to bind strongly to soils
and does not readily leach. In soil or water, it breaks down quickly by microbial action (HSDB,
2008).
16.2 Use, Production, and Releases
Di(2-ethylhexyl)adipate is used in making plastics. It can also be used as a solvent, in
aircraft lubricants, and as a hydraulic fluid. Furthermore, di(2-ethylhexyl)adipate is also used as a
plasticizer or solvent in the following cosmetics: bath oils, eye shadow, cologne, foundations,
rouge, blusher, nail-polish remover, moisturizers and indoor tanning preparations, and in meat
wrapping operations (HSDB, 2008).
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 16-1 presents the production of di(2-ethylhexyl)adipate in the United States from
1986 to 2002. Note that the production of di(2-ethylhexyl)adipate in the United States has
fluctuated since 1986.
16-1
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Exhibit 16-1: Production of Di(2-ethylhexyl)adipate in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
> 10 million - 50 million pounds
> 10 million - 50 million pounds
> 50 million - 100 million pounds
> 50 million - 100 million pounds
> 10 million - 50 million pounds
Source: USEPA, 2003
Di(2-ethylhexyl)adipate is not listed as a Toxics Release Inventory (TRI) chemical; thus,
no TRI release records are available.
16.3 Occurrence in Ambient Water
No National Water Quality Assessment (NAWQA) Program data are available from the
United States Geological Survey (USGS) on the occurrence of di(2-ethylhexyl)adipate in ambient
waters from the Pesticide National Synthesis Project (Gilliom et a/., 2007) or the EPA Summary
Analysis of Cycle 1 data.
16.4 Occurrence in Drinking Water
Di(2-ethylhexyl)adipate is regulated as a synthetic organic chemical (SOC) in drinking
water. All non-purchased community water systems (CWSs) and non-transient non-community
water systems (NTNCWSs) are required to sample for SOCs. The maximum waiver period for
SOCs is three years, but this waiver can be renewed indefinitely. (Systems may receive a waiver
at any time without having collected an SOC sample. With a waiver, systems are not required to
collect an SOC sample.)
All CWSs and NTNCWSs without an SOC waiver must collect four consecutive
quarterly samples during the initial three-year compliance period.l If all four samples are non-
detections, then a system serving less than 3,300 persons may reduce to one sample during each
consecutive compliance period; a system serving more than 3,300 persons may reduce to two
quarterly samples within a 12-month period during a 3-year compliance period. If a chemical is
detected (but is less than the MCL), the system must take one sample per quarter until results are
below the MCL (minimum of two quarterly samples for ground water systems and four quarterly
samples for surface water systems). If all quarterly samples are below the MCL, the system may
return to annual sampling. If a chemical is detected at a level greater than the MCL, the system
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
16-2
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
(whether ground water or surface water) must take quarterly samples until four consecutive
quarters are below the MCL. If all quarterly samples are below the MCL, the system may return
to annual sampling.
The analysis of di(2-ethylhexyl)adipate occurrence presented in the following section is
based on state compliance monitoring data from the Six-Year Review-ICR Dataset. This is the
largest and most comprehensive compliance monitoring data set compiled by EPA's Drinking
Water Program to date.
Di(2-ethylhexyl)adipate data were provided by 43 of the Six-Year Review-ICR states.
(No di(2-ethylhexyl)adipate data were received from Hawaii or Oklahoma.) These data consist of
121,792 analytical results from 28,902 public water systems (PWSs) during the period from 1998
to 2005. The number of sample results and systems vary by state, although the state data sets
have been reviewed and checked to ensure adequacy of coverage and completeness.
16.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 16-2
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For di(2-ethylhexyl)adipate, 1.754% of 28,902 systems
reported detections. Exhibit 16-3 lists the minimum, median, 90th percentile, and maximum di(2-
ethylhexyl)adipate concentrations based on detections from all systems in the Six-Year Review-
ICR Dataset. The median concentration of di(2-ethylhexyl)adipate, based on detections from all
systems, is 0.91 |ig/L.
Exhibit 16-2: Di(2-ethylhexyl)adipate Occurrence Data from the
Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
94,351
25,891
65,031,810
Surface Water
27,441
3,011
119,102,864
Combined Ground &
Surface Water
121,792
28,902
184,134,674
Percent with Detections
Ground Water
0.627%
1.599%
6.686%
Surface Water
0.609%
3.089%
6.811%
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Combined Ground &
Surface Water
0.623%
1.754%
6.767%
Exhibit 16-3: Di(2-ethylhexyl)adipate Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.01
Median
0.935
90tn
Percentile
15.13
Maximum
1,300
Surface Water
0.02
0.8
4.1
43.7
Combined Ground &
Surface Water
0.01
0.91
8.2
1,300
The following maps illustrate the geographic distribution of di(2-ethylhexyl)adipate
occurrence in drinking water. Exhibit 16-4 shows the states with systems with at least one
detection and Exhibit 16-5 shows the states with systems with at least one detection greater than
the MCL concentration. Note that five states did not submit data for use in the Six-Year Review
(Kansas2, Louisiana, Mississippi, Pennsylvania, and Washington). Hawaii and Oklahoma did
submit Six-Year data for most contaminants, but did not submit data for di(2-ethylhexyl)adipate.
The distribution of systems with detections of di(2-ethylhexyl)adipate is geographically
dispersed. Seven states reported detections in more than 5% of their systems. In 10 states,
between 1% and 5% of systems reported detections. Only two states reported detections greater
than the MCL concentration of 400 |ig/L.
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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Exhibit 16-4: Percentage of Systems with at Least One Di(2-ethylhexyl)adipate
Detection, by State
Estates with Waivers or Not Submitting
States with No Detections
Less than 1 % of Systems Detecting
Between 1% and 5% of Systems Detecting
More than 5% of Systems Detecting
Exhibit 16-5: Percentage of Systems with at Least One Di(2-ethylhexyl)adipate
Detection Greater than the MCL Concentration (> 400 pg/L), by State
States with Waivers or Not Submitting
States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
Between 0.1% and 0.5% of Systems with Detections > MCL
More than 0.5% of Systems with Detections > MCL
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Exhibit 16-6 presents the Stage 1 analysis of di(2-ethylhexyl)adipate occurrence in
drinking water from systems and population-served by those systems in the Six-Year Review-
ICR Dataset relative to two thresholds: 200 |ig/L and 400 |ig/L. Seven ground water systems,
serving about 25,000 persons, reported at least one detection greater than or equal to 200 ng/L;
and 2 ground water systems, serving about 23,000 persons, reported at least one detection greater
than 400 |ig/L. No surface water systems reported detections greater than either threshold.
Exhibit 16-6: Di(2-ethylhexyl)adipate Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 400 |jg/L
> 200 |jg/L
Number of
Systems
Exceeding
Threshold
2
7
Percent of
Systems
Exceeding
Threshold
0.008%
0.027%
Total Population-
Served by
Systems
Exceeding
Threshold
22,913
24,953
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.035%
0.038%
Surface
Water
> 400 |jg/L
> 200 |jg/L
0
0
0.000%
0.000%
0
0
0.000%
0.000%
Combined
Ground &
Surface
Water
> 400 |jg/L
> 200 |jg/L
2
7
0.007%
0.024%
22,913
24,953
0.012%
0.014%
16.5 References
Gilliom, R.J., I.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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
Hazardous Substance Data Bank (HSDB). 2008. BIS(2-ETHYLHEXYL) ADIPATE. Available
on the Internet at: http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen7HSDB. [Search for BIS(2-
ETHYLHEXYL)ADIPATE.] Accessed: July 2, 2008.
United States Environmental Protection Agency (USEPA). 1992. Drinking Water; National
Primary Drinking Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals;
National Primary Drinking Water Regulations Implementation; Final Rule. Federal Register.
Vol. 57, No. 138. p. 31776, July 17, 1992.
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USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - Di(2-ethylhexyl)adipate. Last modified September 10, 2007. Available on the
Internet at: http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for di(2-
ethylhexyl)adipate.] Accessed February 21, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
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17 Di(2-ethylhexyl)phthalate (DEHP)
This chapter on di(2-ethylhexyl)phthalate (DEHP) is part of a report that is organized so
that each chapter presents information on one specific contaminant. Chapter 1 of this report,
Introduction, presents background information on all sources of data used as well as the
analytical approach used to estimate contaminant occurrence in drinking water. This contaminant
chapter includes background information (such as regulatory history, general chemical
information, and environmental fate and behavior), use and environmental release information,
and di(2-ethylhexyl)phthalate occurrence estimates in ambient water and drinking water. All
drinking water occurrence estimates were based on data from the National Compliance
Monitoring Information Collection Request (ICR) Dataset for the Second Six-Year Review (the
"Six Year Review-ICR Dataset"). For detailed information regarding this dataset, data
management, data quality assessments, and the analytical approach used to generate all
contaminant occurrence estimates presented in this chapter, please refer to USEPA (2009).
17.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for di(2-ethylhexyl)phthalate on July
17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR established a maximum contaminant
level goal (MCLG) of zero based on a cancer classification of B2, probable human carcinogen,
and a maximum contaminant level (MCL) of 6 |ig/L based on analytical feasibility.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2002),
di(2-ethylhexyl)phthalate (C 24^04) is a member of the group of related chemicals called
phthalates or phthalic acid esters. Di(2-ethylhexyl)phthalate (also known as bis(2-
ethylhexyl)phthalate or DEHP) is a colorless liquid with almost no odor. It will bind to soil,
limiting its ability to leach into ground water. In water it rapidly biodegrades unless oxygen is
limited. It can accumulate in aquatic organisms; however tissue levels are usually low because it
is metabolized by larger organisms (ATSDR, 2002).
17.2 Use, Production, and Releases
Di(2-ethylhexyl)phthalate is a manufactured chemical that is commonly added to plastics
to make them flexible. Its greatest use is as a plasticizer for polyvinyl chloride (PVC). Because of
concerns about health effects, di(2-ethylhexyl)phthalate is no longer used as a plasticizer in food
wraps. It is present in plastic products such as wall coverings, tablecloths, floor tiles, furniture
upholstery, shower curtains, garden hoses, swimming pool liners, rainwear, baby pants, dolls,
some toys, shoes, automobile upholstery and tops, packaging film and sheets, sheathing for wire
and cable, medical tubing, and blood storage bags (ATSDR, 2002).
The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for di(2-ethylhexyl)phthalate.
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Di(2-ethylhexyl)phthalate is listed as a Toxics Release Inventory (TRI) chemical. TRI
data indicate that total off-site and on-site releases of di(2-ethylhexyl)phthalate for the period
1998-2006 ranged from 998,000 pounds to approximately 1.5 million pounds, with a general
decrease over time. Off-site releases were greater than on-site releases (USEPA, 2008).
17.3 Occurrence in Ambient Water
No National Water Quality Assessment (NAWQA) Program data are available from the
United States Geological Survey (USGS) on the occurrence of di(2-ethylhexyl)phthalate in
ambient waters from the Pesticide National Synthesis Project (Gilliom et a/., 2007) or the EPA
Summary Analysis of Cycle 1 data.
17.4 Occurrence in Drinking Water
Di(2-ethylhexyl)phthalate is regulated as a synthetic organic chemical (SOC) in drinking
water. All non-purchased community water systems (CWSs) and non-transient non-community
water systems (NTNCWSs) are required to sample for SOCs. The maximum waiver period for
SOCs is three years, but this waiver can be renewed indefinitely. (Systems may receive a waiver
at any time without having collected an SOC sample. With a waiver, systems are not required to
collect an SOC sample.)
All CWSs and NTNCWSs without an SOC waiver must collect four consecutive
quarterly samples during the initial three-year compliance period.l If all four samples are non-
detections, then a system serving less than 3,300 persons may reduce to one sample during each
consecutive compliance period; a system serving more than 3,300 persons may reduce to two
quarterly samples within a 12-month period during a 3-year compliance period. If a chemical is
detected (but is less than the MCL), the system must take one sample per quarter until results are
below the MCL (minimum of two quarterly samples for ground water systems and four quarterly
samples for surface water systems). If all quarterly samples are below the MCL, the system may
return to annual sampling. If a chemical is detected at a level greater than the MCL, the system
(whether ground water or surface water) must take quarterly samples until four consecutive
quarters are below the MCL. If all quarterly samples are below the MCL, the system may return
to annual sampling.
The analysis of di(2-ethylhexyl)phthalate occurrence presented in the following section is
based on state compliance monitoring data from the Six-Year Review-ICR Dataset. This is the
largest and most comprehensive compliance monitoring data set compiled by EPA's Drinking
Water Program to date.
Di(2-ethylhexyl)phthalate data were provided by 42 of the Six-Year Review-ICR states.
(There were no di(2-ethylhexyl)phthalate data from the following states: Hawaii, Oklahoma, and
Wisconsin.) The di(2-ethylhexyl)phthalate data from the 42 states consist of 120,846 analytical
results from 27,667 public water systems (PWSs) during the period from 1998 to 2005. The
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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number of sample results and systems vary by state, although the state data sets have been
reviewed and checked to ensure adequacy of coverage and completeness.
17.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 17-1
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For di(2-ethylhexyl)phthalate, 11.197% of 27,667
systems reported detections. (The high occurrence of di(2-ethylhexyl)phthalate could be due, in
part, to sample contamination from older generation laboratory and field sampling equipment
made of plastics that contained (and sometimes released) phthalates and may exaggerate the
actual sample concentrations.) Exhibit 17-2 lists the minimum, median, 90th percentile, and
maximum di(2-ethylhexyl)phthalate concentrations based on detections from all systems in the
Six-Year Review-ICR Dataset. The median concentration of di(2-ethylhexyl)phthalate, based on
detections from all systems, is 1.2 |ig/L.
Exhibit 17-1: Di(2-ethylhexyl)phthalate Occurrence Data from the
Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
92,944
24,677
62,976,862
Surface Water
27,902
2,990
116,971,710
Combined Ground &
Surface Water
120,846
27,667
179,948,572
Percent with Detections
Ground Water
4.864%
10.577%
19.240%
Surface Water
5.061%
16.321%
28.450%
Combined Ground &
Surface Water
4.910%
11.197%
25.227%
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Exhibit 17-2: Di(2-ethylhexyl)phthalate Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.05
Median
1.3
90tn
Percentile
6.26
Maximum
250
Surface Water
0.06
1.1
4.4
49
Combined Ground &
Surface Water
0.05
1.2
5.8
250
The following maps illustrate the geographic distribution of di(2-ethylhexyl)phthalate
occurrence in drinking water. Exhibit 17-3 shows the states with systems with at least one
detection and Exhibit 17-4 shows the states with systems with at least one detection greater than
the MCL concentration. Note that five states did not submit data for use in the Six-Year Review
(Kansas2, Louisiana, Mississippi, Pennsylvania, and Washington). Hawaii, Oklahoma, and
Wisconsin did submit Six-Year data for most contaminants, but did not submit di(2-
ethylhexyl)phthalate data.
The distribution of systems with detections of di(2-ethylhexyl)phthalate is geographically
dispersed. As stated earlier, the high occurrence of di(2-ethylhexyl)phthalate could be due, in
part, to sample contamination from older generation laboratory and field sampling equipment
made of plastics that contained (and sometimes released) phthalates and may exaggerate the
actual sample concentrations. Seventeen states reported detections in more than 10% of their
systems. In 12 states, between 5% and 10% of systems reported detections. Systems in 35 states
reported at least one detection greater than the MCL concentration of 6 |ig/L.
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 17-3: Percentage of Systems with at Least One Di(2-ethylhexyl)phthalate
Detection, by State
Estates with Waivers or Not Submitting
States with No Detections
Less than 5% of Systems Detecting
Between 5% and 10% of Systems Detecting
More than 10% of Systems Detecting
Exhibit 17-4: Percentage of Systems with at Least One Di(2-ethylhexyl)phthalate
Detection Greater than the MCL Concentration (> 6 pg/L), by State
fflft States with Waivers or Not Submitting
States with No Detections > MCL
Less than 1% of Systems with Detections > MCL
^B Between 1% and 5% of Systems with Detections > MCL
^B More than 5% of Systems with Detections > MCL
Exhibit 17-5 presents the Stage 1 analysis of di(2-ethylhexyl)phthalate occurrence in
drinking water from systems and population-served by those systems in the Six-Year Review-
ICR Dataset relative to two thresholds: 3 |ig/L and 6 |ig/L. A total of 955 (3.452% of) systems,
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serving more than 25 million persons, reported at least one detection greater than or equal to 3
Hg/L; and 460 (1.663% of) systems, serving more than 11.5 million persons, reported at least one
detection greater than 6 |ig/L.
Exhibit 17-5: Di(2-ethylhexyl)phthalate Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 6 |jg/L
> 3 ug/L
Number of
Systems
Exceeding
Threshold
390
786
Percent of
Systems
Exceeding
Threshold
1.580%
3.185%
Total Population-
Served by
Systems
Exceeding
Threshold
2,513,952
5,407,270
Percent of
Population -Served
by Systems
Exceeding
Threshold
3.992%
8.586%
Surface
Water
> 6 |jg/L
> 3 ug/L
70
169
2.341%
5.652%
8,996,752
19,734,540
7.691%
16.871%
Combined
Ground &
Surface
Water
> 6 ug/L
> 3 ug/L
460
955
1 .663%
3.452%
11,510,704
25,141,810
6.397%
13.972%
17.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2002. Toxicological Profile for
Di(2-ethylhexyl)phthalate (DEEP). September 2002. Available on the Internet at:
http://www.atsdr.cdc.gov/toxprofiles/tp9.pdf
Gilliom, R.J., I.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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
United States Environmental Protection Agency (USEPA). 1992. Drinking Water; National
Primary Drinking Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals;
National Primary Drinking Water Regulations Implementation; Final Rule. Federal Register.
Vol. 57, No. 138. p. 31776, July 17, 1992.
USEPA. 2008. TRI Explorer: Trends - Di(2-ethylhexyl)Phthalate. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for di(2-
ethylhexyl)phthalate.] Accessed March 6, 2008.
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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. Office of Water. EPA-815-B-09-006. October 2009.
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18 1,2-Dichlorobenzene (o-Dichlorobenzene)
This chapter on 1,2-dichlorobenzene (o-dichlorobenzene) is part of a report that is
organized so that each chapter presents information on one specific contaminant. Chapter 1 of
this report, Introduction, presents background information on all sources of data used as well as
the analytical approach used to estimate contaminant occurrence in drinking water. This
contaminant chapter includes background information (such as regulatory history, general
chemical information, and environmental fate and behavior), use and environmental release
information, and 1,2-dichlorobenzene occurrence estimates in ambient water and drinking water.
All drinking water occurrence estimates were based on data from the National Compliance
Monitoring Information Collection Request (ICR) Dataset for the Second Six-Year Review (the
"Six Year Review-ICR Dataset"). For detailed information regarding this dataset, data
management, data quality assessments, and the analytical approach used to generate all
contaminant occurrence estimates presented in this chapter, please refer to USEPA (2009).
18.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for 1,2-dichlorobenzene on January 30,
1991 (56 FR 3526 (USEPA, 1991)). The NPDWR established a maximum contaminant level
goal (MCLG) and a maximum contaminant level (MCL) of 600 |ig/L. EPA developed the MCLG
based on a reference dose (RfD) of 90 jig/kg-day (0.09 mg/kg-day) and a cancer classification of
D, not classifiable as to human carcinogenicity.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2006),
1,2-dichlorobenzene (CeFLtCb) is a colorless to pale yellow liquid. It is part of the
dichlorobenzene family, which also includes 1,3-dichlorobenzene and 1,4-dichlorobenzene. It
has a pleasant, aromatic odor, and is not very flammable or soluble in water. 1,2-
Dichlorobenzene tends to bind moderately tightly to soil, although some leaching can occur. It is
fairly resistant to various forms of degradation. Other names for 1,2-dichlorobenzene include o-
dichlorobenzene and 1,2-DCB (ATSDR, 2006).
18.2 Use, Production, and Releases
1,2-Dichlorobenzene is used as a solvent for waxes, gums, resins, and wood preservatives
and as an agent in the synthesis of dyes and odor-controlling products. It is also used as a
precursor to 3,4-dichloroaniline in the production of herbicides (ATSDR, 2006).
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 18-1 presents the production of 1,2-dichlorobenzene in the United States from
1986 to 2002. Note that the production of 1,2-dichlorobenzene in the United States has fluctuated
from year to year since 1986.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 18-1: Production of 1,2-Dichlorobenzene in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
> 10 million - 50 million pounds
> 50 million - 100 million pounds
> 10 million - 50 million pounds
> 50 million - 100 million pounds
> 10 million - 50 million pounds
Source: USEPA, 2003
1,2-Dichlorobenzene is listed as a Toxics Release Inventory (TRI) chemical. TRI data
indicate that total off-site and on-site releases of 1,2-dichlorobenzene for the period 1998-2006
ranged from approximately 87,000 pounds to approximately 390,000 pounds, with a general
decrease over time. On-site releases were greater than off-site releases (USEPA, 2008).
18.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of 1,2-
dichlorobenzene in ambient water are available from the NAWQA program.
18.3.1 EPA Summary Analysis of NAWQA Data
EPA, with the cooperation of USGS, has performed a summary analysis of all Cycle 1
water monitoring data from all study units (1992-2001) for 1,2-dichlorobenzene. Detection
frequencies were computed as the percentage of samples and sites with detections (i.e., with at
least one result equal to or greater than the reporting limit). Sample detections can be biased by
frequent sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 18-2. Overall, 1,2-
dichlorobenzene was detected in 1.2% of samples and at 1.1% of sites. 1,2-Dichlorobenzene was
detected more frequently in surface water than in ground water. The median concentration based
on detections from all sites was 0.04 |ig/L. The 99th percentile concentration based on detections
from all sites was 1.502 |ig/L.
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Exhibit 18-2: EPA Summary Analysis of 1,2-Dichlorobenzene Data from NAWQA
Study Units, 1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
4,660
1,419
6,079
% Samples
with
Detections
0.6%
3.2%
1.2%
Number
of Sites
4,159
191
4,350
% Sites
with
Detections
0.7%
9.4%
1.1%
Concentration Values
(of detections, in ug/L)
Minimum
0.002
0.01
0.002
Median
0.036
0.04
0.04
95th
Percen-
tile
0.749
0.36
0.3653
99th
Percen-
tile
1.502
0.447
1.502
Maximum
1.502
0.447
1.502
1. RLs (Reporting Limits) for 1,2-dichlorobenzene varied, but did not exceed 0.01 ug/L.
18.4 Occurrence in Drinking Water
1,2-Dichlorobenzene is regulated as a volatile organic compound (VOC) in drinking
water. All non-purchased community water systems (CWSs) and non-transient non-community
water systems (NTNCWSs) are required to sample for VOCs. The maximum waiver period for
VOCs is six years for ground water systems and three years for surface water systems.
All CWSs and NTNCWSs must collect four consecutive quarterly samples during the
initial three-year compliance period.l If all four samples are non-detections, then the system may
reduce to annual sampling. After three annual samples without a detection, a system may be
granted a waiver. If a compound is detected (but at less than the MCL), the system must take one
sample per quarter until results are below the MCL (minimum of two quarterly samples for
ground water systems and four quarterly samples for surface water systems). If all quarterly
samples are below the MCL, the system may return to annual sampling. If a compound is
detected at a level greater than the MCL, the system (whether ground water or surface water)
must take four consecutive quarterly samples until all are below the MCL. If all quarterly
samples are below the MCL, the system may return to annual sampling.
The analysis of 1,2-dichlorobenzene occurrence presented in the following section is
based on state compliance monitoring data from the Six-Year Review-ICR Dataset. This is the
largest and most comprehensive compliance monitoring data set compiled by EPA's Drinking
Water Program to date.
All of the Six-Year Review-ICR states provided occurrence data for 1,2-dichlorobenzene.
These data consist of 372,946 analytical results from 50,422 public water systems (PWSs) during
the period from 1998 to 2005. The number of sample results and systems vary by state, although
the state data sets have been reviewed and checked to ensure adequacy of coverage and
completeness.
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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18.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 18-3
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For 1,2-dichlorobenzene, 0.230% of 50,422 systems
reported detections. Exhibit 18-4 lists the minimum, median, 90th percentile, and maximum 1,2-
dichlorobenzene concentrations based on detections from all systems in the Six-Year Review-
ICR Dataset. The median concentration of 1,2-dichlorobenzene, based on detections from all
systems, is 0.8 |ig/L.
Exhibit 18-3: 1,2-Dichlorobenzene Occurrence Data from the
Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
288,648
46,166
86,389,766
Surface Water
84,298
4,256
140,540,050
Combined Ground &
Surface Water
372,946
50,422
226,929,816
Percent with Detections
Ground Water
0.081%
0.201%
0.539%
Surface Water
0.045%
0.540%
2.326%
Combined Ground &
Surface Water
0.073%
0.230%
1 .646%
Exhibit 18-4: 1,2-Dichlorobenzene Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.01
Median
0.9
90tn
Percentile
3
Maximum
110
Surface Water
0.004
0.5
1.3
6
18-4
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source Water Type
Detection Value (ug/L)
Minimum
Median
90tn
Percentile
Maximum
Combined Ground &
Surface Water
0.004
0.8
2.74
110
Exhibit 18-5 illustrates the geographic distribution of 1,2-dichlorobenzene occurrence in
drinking water, identifying the states with systems with at least one detection. (No systems
reported detections greater than the MCL concentration; thus, no map is included for MCL
concentration exceedances.) Note that five states did not submit data for use in the Six-Year
Review (Kansas2, Louisiana, Mississippi, Pennsylvania, and Washington).
Only three states reported detections in more than 1% of systems. In four states, between
0.5% and 1% of systems reported detections. No systems reported detections greater than the
MCL concentration of 600 |ig/L.
Exhibit 18-5: Percentage of Systems with at Least One 1,2-Dichlorobenzene
Detection, by State
J2%| states Not Submitting Any Data
States with No Detections
| Less than 0.5% of Systems Detecting
| Between 0.5% and 1% of Systems Detecting
| More than 1% of Systems Detecting
I
Exhibit 18-6 presents the Stage 1 analysis of 1,2-dichlorobenzene occurrence in drinking
water from systems and population-served by those systems in the Six-Year Review-ICR Dataset
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
18-5
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
relative to two thresholds: 300 |ig/L and 600 |ig/L. No systems reported detections greater than
or equal to either threshold.
Exhibit 18-6: 1,2-Dichlorobenzene Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 600 |jg/L
> 300 |jg/L
Number of
Systems
Exceeding
Threshold
0
0
Percent of
Systems
Exceeding
Threshold
0.000%
0.000%
Total Population-
Served by
Systems
Exceeding
Threshold
0
0
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.000%
0.000%
Surface
Water
> 600 |jg/L
> 300 |jg/L
0
0
0.000%
0.000%
0
0
0.000%
0.000%
Combined
Ground &
Surface
Water
> 600 |jg/L
> 300 |jg/L
0
0
0.000%
0.000%
0
0
0.000%
0.000%
18.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2006. Toxicological Profile for
Dichlorobenzenes. August 2006. Available on the Internet at:
http://www.atsdr.cdc.gov/toxprofiles/tplO.html.
United States Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - 1,2-Dichlorobenzene. Last modified September 10, 2007. Available on the Internet
at: http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for 1,2-dichlorobenzene.]
Accessed February 21, 2008.
USEPA. 2008. TRI Explorer: Trends - 1,2-Dichlorobenzene. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for 1,2-
dichlorobenzene.] Accessed March 5, 2008.
18-6
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
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. Office of Water. EPA-815-B-09-006. October 2009.
18-7
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
19 1,4-Dichlorobenzene (p-Dichlorobenzene)
This chapter on 1,4-dichlorobenzene (p-dichlorobenzene) is part of a report that is
organized so that each chapter presents information on one specific contaminant. Chapter 1 of
this report, Introduction, presents background information on all sources of data used as well as
the analytical approach used to estimate contaminant occurrence in drinking water. This
contaminant chapter includes background information (such as regulatory history, general
chemical information, and environmental fate and behavior), use and environmental release
information, and 1,4-dichlorobenzene occurrence estimates in ambient water and drinking water.
All drinking water occurrence estimates were based on data from the National Compliance
Monitoring Information Collection Request (ICR) Dataset for the Second Six-Year Review (the
"Six Year Review-ICR Dataset"). For detailed information regarding this dataset, data
management, data quality assessments, and the analytical approach used to generate all
contaminant occurrence estimates presented in this chapter, please refer to USEPA (2009).
19.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for 1,4-dichlorobenzene on July 8,
1987 (52 FR 25690 (USEPA, 1987)). The NPDWR established a maximum contaminant level
goal (MCLG) and a maximum contaminant level (MCL) of 75 |ig/L. EPA developed the MCLG
based on a reference dose (RfD) of 100 jig/kg-day (0.1 mg/kg-day) and a cancer classification of
C, possible human carcinogen.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2006),
1,4-dichlorobenzene (CeFLtCb) is a colorless to white solid that smells like mothballs and is one
of two chemicals commonly used to make mothballs. It is part of the dichlorobenzene family of
chemicals, which also includes 1,2-dichlorobenzene and 1,3-dichlorobenzene. Commercially,
1,4-dichlorobenzene is the most important of the three dichlorobenzene isomers. 1,4-
Dichlorobenzene is not very flammable or soluble in water. It can bind to soil and is not easily
biodegraded. Other names for 1,4-dichlorobenzene include p-dichlorobenzene and 1,4-DCB
(ATSDR, 2006).
19.2 Use, Production, and Releases
In addition to mothballs, 1,4-dichlorobenzene is used to make deodorant blocks for
garbage cans, restrooms, and animal-holding facilities. Its usefulness in these applications arises
from 1,4-dichlorobenzene's low solubility in water and its relatively high volatility: it sublimes
readily near room temperature. 1,4-Dichlorobenzene has been increasingly used in the synthesis
of resins. It has also been used as an insecticide on fruit and as an agent to control mold and
mildew growth on tobacco seeds, leather, and some fabrics (ATSDR, 2006).
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
19-1
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
years. Exhibit 19-1 presents the production of 1,4-dichlorobenzene in the United States from
1986 to 2002. Note that the production of 1,4-dichlorobenzene in the United States has increased
since 1986.
Exhibit 19-1: Production of 1,4-Dichlorobenzene in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
> 10 million - 50 million pounds
> 50 million - 100 million pounds
> 50 million - 100 million pounds
> 50 million - 100 million pounds
> 50 million - 100 million pounds
Source: USEPA, 2003
1,4-Dichlorobenzene is listed as a Toxics Release Inventory (TRI) chemical. TRI data
indicate that total off-site and on-site releases of 1,4-dichlorobenzene for the period 1998-2006
ranged from approximately 98,000 pounds to approximately 189,000 pounds, with a general
decrease over time. On-site releases were greater than off-site releases (USEPA, 2008).
19.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of 1,4-
dichlorobenzene in ambient water are available from the NAWQA program.
19.3.1 EPA Summary Analysis of NAWQA Data
EPA, with the cooperation of the USGS, has performed a summary analysis of all Cycle 1
water monitoring data from all study units (1992-2001) for 1,4-dichlorobenzene. Detection
frequencies were computed as the percentage of samples and sites with detections (i.e., with at
least one result equal to or greater than the reporting limit). Sample detections can be biased by
frequent sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 19-2. Overall, 1,4-
dichlorobenzene was detected in 4.3% of samples and at 3.1% of sites. It was detected more
frequently in surface water than in ground water. The median concentration based on detections
19-2
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
from all sites was 0.015 |ig/L. The 99l percentile concentration based on detections from all sites
was 1.15 ng/L.
Exhibit 19-2: EPA Summary Analysis of 1,4-Dichlorobenzene Data from NAWQA
Study Units, 1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
4,660
1,417
6,077
% Samples
with
Detections
1.8%
12.5%
4.3%
Number
of Sites
4,159
191
4,350
% Sites
with
Detections
1.9%
29.3%
3.1%
Concentration Values
(of detections, in ug/L)
Minimum
0.0029
0.002
0.002
Median
0.0135
0.0155
0.015
95th
Percen-
tile
0.457
0.2298
0.3
99th
Percen-
tile
1.7
0.66
1.15
Maximum
1.7
0.67
1.7
1. RLs (Reporting Limits) for 1,4-dichlorobenzene varied, but did not exceed 0.003 ug/L.
19.4 Occurrence in Drinking Water
1,4-Dichlorobenzene is regulated as a volatile organic compound (VOC) in drinking
water. All non-purchased community water systems (CWSs) and non-transient non-community
water systems (NTNCWSs) are required to sample for VOCs. The maximum waiver period for
VOCs is six years for ground water systems and three years for surface water systems.
All CWSs and NTNCWSs must collect four consecutive quarterly samples during the
initial three-year compliance period.l If all four samples are non-detections, then the system may
reduce to annual sampling. After three annual samples without a detection, a system may be
granted a waiver. If a compound is detected (but at less than the MCL), the system must take one
sample per quarter until results are below the MCL (minimum of two quarterly samples for
ground water systems and four quarterly samples for surface water systems). If all quarterly
samples are below the MCL, the system may return to annual sampling. If a compound is
detected at a level greater than the MCL, the system (whether ground water or surface water)
must take four consecutive quarterly samples until all are below the MCL. If all quarterly
samples are below the MCL, the system may return to annual sampling.
The analysis of 1,4-dichlorobenzene occurrence presented in the following section is
based on state compliance monitoring data from the Six-Year Review-ICR Dataset. This is the
largest and most comprehensive compliance monitoring data set compiled by EPA's Drinking
Water Program to date.
All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
19-3
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Forty-four of the Six-Year Review-ICR states provided occurrence data for 1,4-
dichlorobenzene. (There were no 1,4-dichlorobenzene data from Arkansas.) These data consist of
370,698 analytical results from 49,969 public water systems (PWSs) during the period from 1998
to 2005. The number of sample results and systems vary by state, although the state data sets
have been reviewed and checked to ensure adequacy of coverage and completeness.
19.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 19-3
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For 1,4-dichlorobenzene, 1.497% of 49,969 systems
reported detections. Exhibit 19-4 lists the minimum, median, 90th percentile, and maximum 1,4-
dichlorobenzene concentrations based on detections from all systems in the Six-Year Review-
ICR Dataset. The median concentration of 1,4-dichlorobenzene, based on detections from all
systems, is 0.8 |ig/L.
Exhibit 19-3: 1,4-Dichlorobenzene Occurrence Data from the
Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
286,821
45,785
85,479,601
Surface Water
83,877
4,184
138,997,024
Combined Ground &
Surface Water
370,698
49,969
224,476,625
Percent with Detections
Ground Water
0.417%
1 .424%
2.374%
Surface Water
0.217%
2.294%
3.910%
Combined Ground &
Surface Water
0.371%
1 .497%
3.325%
19-4
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 19-4: 1,4-Dichlorobenzene Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.0052
Median
0.8
90tn
Percentile
2.5
Maximum
700
Surface Water
0.002
0.6
1.4
13.6
Combined Ground &
Surface Water
0.002
0.8
2.4
700
The following maps illustrate the geographic distribution of 1,4-dichlorobenzene
occurrence in drinking water. Exhibit 19-5 shows the states with systems with at least one
detection and Exhibit 19-6 shows the states with systems with at least one detection greater than
the MCL concentration. Note that five states did not submit data for use in the Six-Year Review
(Kansas2, Louisiana, Mississippi, Pennsylvania, and Washington). Arkansas did submit Six-Year
data for most contaminants, but did not submit data for 1,4-dichlorobenzene.
In eight states, more than 2% of systems detected 1,4-dichlorobenzene. These states are
mostly located in the eastern half of the United States, as well as the upper Midwest. Sixteen
states reported that 1% to 2% of systems reported detections. Only three states reported
detections greater than the MCL concentration of 75 |ig/L, but the exceedances occurred in less
than 0.1% of systems.
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
19-5
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 19-5: Percentage of Systems with at Least One 1,4-Dichlorobenzene
Detection, by State
Estates with Waivers or Not Submitting
States with No Detections
Less than 1 % of Systems Detecting
Between 1% and 2% of Systems Detecting
More than 2% of Systems Detecting
Exhibit 19-6: Percentage of Systems with at Least One 1,4-Dichlorobenzene
Detection Greater than the MCL Concentration (> 75 pg/L), by State
States with Waivers or Not Submitting
States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
| Between 0.1% and 0.2% of Systems with Detections > MCL
| More than 0.2% of Systems with Detections > MCL
19-6
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 19-7 presents the Stage 1 analysis of 1,4-dichlorobenzene occurrence in drinking
water from systems and population-served by those systems in the Six-Year Review-ICR Dataset
relative to two thresholds: 37.5 |ig/L and 75 |ig/L. Six ground water systems, serving about
103,500 persons, reported at least one detection greater than or equal to 37.5 |ig/L; and 3 ground
water systems, serving approximately 99,000 persons, reported at least one detection greater than
75 ng/L. No surface water systems reported detections exceeding either threshold.
Exhibit 19-7: 1,4-Dichlorobenzene Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 75 |jg/L
> 37.5 |jg/L
Number of
Systems
Exceeding
Threshold
3
6
Percent of
Systems
Exceeding
Threshold
0.007%
0.013%
Total Population-
Served by
Systems
Exceeding
Threshold
99,019
103,510
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.116%
0.121%
Surface
Water
> 75 |jg/L
> 37.5 |jg/L
0
0
0.000%
0.000%
0
0
0.000%
0.000%
Combined
Ground &
Surface
Water
> 75 |jg/L
> 37.5 |jg/L
3
6
0.006%
0.012%
99,019
103,510
0.044%
0.046%
19.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2006. Toxicological Profile for
Dichlorobenzenes. August 2006. Available on the Internet at:
http://www.atsdr.cdc.gov/toxprofiles/tplO.html.
United States Environmental Protection Agency (USEPA). 1987. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals; Monitoring for Unregulated Contaminants;
Final Rule. Federal Register. Vol. 52, No. 130. p. 25690, July 8, 1987.
USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - 1,4-Dichlorobenzene. Last modified September 10, 2007. Available on the Internet
at: http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for 1,4-dichlorobenzene.]
Accessed February 21, 2008.
USEPA. 2008. TRI Explorer: Trends - 1,4-Dichlorobenzene. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for 1,4-
dichlorobenzene.] Accessed March 5, 2008.
19-7
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
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. Office of Water. EPA-815-B-09-006. October 2009.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
20 1,1-Dichloroethylene
This chapter on 1,1-dichloroethylene is part of a report that is organized so that each
chapter presents information on one specific contaminant. Chapter 1 of this report, Introduction,
presents background information on all sources of data used as well as the analytical approach
used to estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and 1,1-
dichloroethylene occurrence estimates in ambient water and drinking water. All drinking water
occurrence estimates were based on data from the National Compliance Monitoring Information
Collection Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR
Dataset"). For detailed information regarding this dataset, data management, data quality
assessments, and the analytical approach used to generate all contaminant occurrence estimates
presented in this chapter, please refer to USEPA (2009).
20.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for 1,1-dichloroethylene on July 8,
1987 (52 FR 25690 (USEPA, 1987)). The NPDWR established a maximum contaminant level
goal (MCLG) and a maximum contaminant level (MCL) of 7 |ig/L. The Agency developed the
MCLG based on a reference dose (RfD) of 10 jig/kg-day (0.01 mg/kg-day) and a cancer
classification of C, possible human carcinogen.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 1995),
1,1-dichloroethylene (CiEfzCb) is an industrial chemical that is not found naturally in the
environment. It is a colorless liquid with a mild, sweet smell. If released to water or soil, it
readily evaporates and is degraded by sunlight. When it does not evaporate, degradation is slow.
1,1-Dichloroethylene is also called vinylidene chloride (ATSDR, 1995).
20.2 Use, Production, and Releases
1,1-Dichloroethylene is used to make certain plastics, including flexible films such as
food wrap, and packaging materials. It is also used to make flame retardant coatings for fiber and
carpet backings, in piping, coating for steel pipes, and in adhesive applications (ATSDR, 1995).
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 20-1 presents the production of 1,1-dichloroethylene in the United States from
1986 to 2002. Note that the production of 1,1-dichloroethylene in the United States has
fluctuated since 1986.
20-1
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 20-1: Production of 1,1-Dichloroethylene in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
> 100 million - 500 million pounds
> 100 million - 500 million pounds
> 10 million - 50 million pounds
> 100 million - 500 million pounds
> 10 million - 50 million pounds
Source: USEPA, 2003
1,1-Dichloroethylene is listed as a Toxics Release Inventory (TRI) chemical. (It is listed
under the synonym vinylidene chloride.) TRI data indicate that total off-site and on-site releases
for the period 1998-2006 ranged from approximately 42,000 pounds to approximately 478,000
pounds, with a general decrease over time. On-site releases were greater than off-site releases
(USEPA, 2008).
20.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of 1,1-
dichloroethylene in ambient water are available from the NAWQA program.
20.3.1 EPA Summary Analysis of NAWQA Data
EPA, with the cooperation of the USGS, has performed a summary analysis of all Cycle 1
water monitoring data from all study units (1992-2001) for 1,1-dichloroethylene. Detection
frequencies were computed as the percentage of samples and sites with detections (i.e., with at
least one result equal to or greater than the reporting limit). Sample detections can be biased by
frequent sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 20-2. Overall, 1,1-
dichloroethylene was detected in 2.4% of samples and at 2.0% of sites. It was detected more
frequently in surface water than in ground water. The median concentration based on detections
from all sites was 0.0217 |ig/L. The 99
sites was 5.317 |ig/L.
,th
percentile concentration based on detections from all
20-2
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 20-2: EPA Summary Analysis of 1,1-Dichloroethylene Data from NAWQA
Study Units, 1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
4,658
1,414
6,072
% Samples
with
Detections
1.6%
5.0%
2.4%
Number
of Sites
4,159
191
4,350
% Sites
with
Detections
1.5%
13.1%
2.0%
Concentration Values
(of detections, in ug/L)
Minimum
0.004
0.005
0.004
Median
0.0295
0.0193
0.0217
95th
Percen-
tile
0.8491
0.34
0.51
99th
Percen-
tile
5.317
34
5.317
Maximum
5.317
34
34
1. RLs (Reporting Limits) for 1,1-dichloroethylene varied, but did not exceed 0.005 ug/L.
20.4 Occurrence in Drinking Water
1,1-Dichloroethylene is regulated as a volatile organic compound (VOC) in drinking
water. All non-purchased community water systems (CWSs) and non-transient non-community
water systems (NTNCWSs) are required to sample for VOCs. The maximum waiver period for
VOCs is six years for ground water systems and three years for surface water systems.
All CWSs and NTNCWSs must collect four consecutive quarterly samples during the
initial three-year compliance period.l If all four samples are non-detections, then the system may
reduce to annual sampling. After three annual samples without a detection, a system may be
granted a waiver. If a compound is detected (but at less than the MCL), the system must take one
sample per quarter until results are below the MCL (minimum of two quarterly samples for
ground water systems and four quarterly samples for surface water systems). If all quarterly
samples are below the MCL, the system may return to annual sampling. If a compound is
detected at a level greater than the MCL, the system (whether ground water or surface water)
must take four consecutive quarterly samples until all are below the MCL. If all quarterly
samples are below the MCL, the system may return to annual sampling.
The analysis of 1,1-dichloroethylene occurrence presented in the following section is
based on state compliance monitoring data from the Six-Year Review-ICR Dataset. This is the
largest and most comprehensive compliance monitoring data set compiled by EPA's Drinking
Water Program to date.
All of the Six-Year Review-ICR states provided occurrence data for 1,1-dichloroethylene.
These data consist of 378,630 analytical results from 50,425 public water systems (PWSs) during
the period from 1998 to 2005. The number of sample results and systems vary by state, although
the state data sets have been reviewed and checked to ensure adequacy of coverage and
completeness.
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
20-3
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
20.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 20-3
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For 1,1-dichloroethylene, 0.688% of 50,425 systems
reported detections. Exhibit 20-4 lists the minimum, median, 90th percentile, and maximum 1,1-
dichloroethylene concentrations based on detections from all systems in the Six-Year Review-
ICR Dataset. The median concentration of 1,1-dichloroethylene, based on detections from all
systems, is 1.7 |ig/L.
Exhibit 20-3: 1,1-Dichloroethylene Occurrence Data from the
Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
290,587
46,171
86,395,257
Surface Water
88,043
4,254
140,514,407
Combined Ground &
Surface Water
378,630
50,425
226,909,664
Percent with Detections
Ground Water
0.804%
0.643%
4.623%
Surface Water
3.832%
1.175%
6.713%
Combined Ground &
Surface Water
1.508%
0.688%
5.917%
Exhibit 20-4: 1,1-Dichloroethylene Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.054
Median
1.1
90tn
Percentile
8.4
Maximum
214
Surface Water
0.12
2.145
7.9
67
20-4
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source Water Type
Combined Ground &
Surface Water
Detection Value (ug/L)
Minimum
0.054
Median
1.7
90tn
Percentile
8
Maximum
214
The following maps illustrate the geographic distribution of 1,1-dichloroethylene
occurrence in drinking water. Exhibit 20-5 shows the states with systems with at least one
detection and Exhibit 20-6 shows the states with systems with at least one detection greater than
the MCL concentration. Note that five states did not submit data for use in the Six-Year Review
(Kansas2, Louisiana, Mississippi, Pennsylvania, and Washington).
The distribution of systems with detections of 1,1-dichloroethylene is geographically
dispersed and detection rates were generally low. Twelve states reported detections in more than
1% of their systems. Nine states reported detections in 0.5% to 1% of systems. Five states
reported no detections. Thirteen states reported detections greater than the MCL concentration of
7 ug/L.
Exhibit 20-5: Percentage of Systems with at Least One 1,1-Dichloroethylene
Detection, by State
: States with Waivers or Not Submitting
States with No Detections
Less than 0.5% of Systems Detecting
Between 0.5% and 1% of Systems Detecting
More than 1% of Systems Detecting
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
20-5
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 20-6: Percentage of Systems with at Least One 1,1-Dichloroethylene
Detection Greater than the MCL Concentration (> 7 ug/L), by State
? States with Waivers or Not Submitting
States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
Between 0.1% and 0.5% of Systems with Detections > MCL
More than 0.5% of Systems with Detections > MCL
Exhibit 20-7 presents the Stage 1 analysis of 1,1-dichloroethylene occurrence in drinking
water from systems and population-served by those systems in the Six-Year Review-ICR Dataset
relative to two thresholds: 3.5 |ig/L and 7 |ig/L. A total of 68 (0.135% of) systems, serving
almost 7.8 million persons, reported at least one detection greater than or equal to 3.5 |ig/L; and
33 (0.065% of) systems, serving approximately 5.7 million persons, reported at least one
detection greater than 7 |ig/L.
Exhibit 20-7: 1,1-Dichloroethylene Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 7 |jg/L
>3.5|jg/L
Number of
Systems
Exceeding
Threshold
24
52
Percent of
Systems
Exceeding
Threshold
0.052%
0.113%
Total Population-
Served by
Systems
Exceeding
Threshold
261,170
922,641
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.302%
1.068%
Surface
Water
> 7 |jg/L
>3.5|jg/L
9
16
0.212%
0.376%
5,451,023
6,853,605
3.879%
4.878%
20-6
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source
Water
Type
Combined
Ground &
Surface
Water
Threshold
> 7 |jg/L
>3.5|jg/L
Number of
Systems
Exceeding
Threshold
33
68
Percent of
Systems
Exceeding
Threshold
0.065%
0.135%
Total Population-
Served by
Systems
Exceeding
Threshold
5,712,193
7,776,246
Percent of
Population -Served
by Systems
Exceeding
Threshold
2.517%
3.427%
20.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 1995. ToxFAQsfor 1,1-
Dichloroethene. September 1995. Available on the Internet at:
http://www.atsdr.cdc.gov/tfacts39.html.
United States Environmental Protection Agency (USEPA). 1987. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals; Monitoring for Unregulated Contaminants;
Final Rule. Federal Register. Vol. 52, No. 130. p. 25690, July 8, 1987.
USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - 1,1-Dichloroethylene. Last modified September 10, 2007. Available on the Internet
at: http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for 1,1-dichloroethylene.]
Accessed February 21, 2008.
USEPA. 2008. TRI Explorer: Trends - Vinylidene Chloride. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for vinylidene
chloride.] Accessed March 9, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
21 cis-l,2-Dichloroethylene
This chapter on cis-l,2-dichloroethylene is part of a report that is organized so that each
chapter presents information on one specific contaminant. Chapter 1 of this report, Introduction,
presents background information on all sources of data used as well as the analytical approach
used to estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and cis-1,2-
dichloroethylene occurrence estimates in ambient water and drinking water. All drinking water
occurrence estimates were based on data from the National Compliance Monitoring Information
Collection Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR
Dataset"). For detailed information regarding this dataset, data management, data quality
assessments, and the analytical approach used to generate all contaminant occurrence estimates
presented in this chapter, please refer to USEPA (2009).
21.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for cis-l,2-dichloroethylene on January
30, 1991 (56 FR 3526 (USEPA, 1991)). The NPDWR established a maximum contaminant level
goal (MCLG) and maximum contaminant level (MCL) of 70 |ig/L. The Agency developed the
MCLG based on a reference dose (RfD) of 10 jig/kg-day (0.01 mg/kg-day) and a cancer
classification of D, not classifiable as to human carcinogenicity.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 1996),
1,2-dichloroethylene (CiEfzCb) is a highly flammable, colorless liquid with a sharp, harsh odor
that can be smelled in very small amounts. Two slightly different forms exist, a "cis" form and a
"trans" form. When 1,2-dichloroethylene is released to land or water, most of it evaporates into
the air. 1,2-Dichloroethylene below soil surfaces in landfills or hazardous waste sites may
dissolve in water and possibly contaminate groundwater (ATSDR, 1996). 1,2-Dichloroethylene
is also known as 1,2-dichloroethene and 1,2-DCE.
21.2 Use, Production, and Releases
1,2-Dichloroethylene is used most often to produce solvents and in chemical mixtures.
Specifically, it is used as a solvent for waxes and resins; in the extraction of rubber; as a
refrigerant; in the manufacture of pharmaceuticals and artificial pearls; in the extraction of oils
and fats from fish and meat; and in making other organic compounds (ATSDR, 1996).
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 21-1 presents the production of cis-1,2-dichloroethylene in the United States from
1986 to 2002. Note that the production of cis-1,2-dichloroethylene in the United States decreased
21-1
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
from 1990 to 1994 and was not reported in the Chemical Update System in 1986, 1998, and
2002.
Exhibit 21-1: Production of cis-1,2-Dichloroethylene in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
No reports
> 500,000 - 1 million pounds
10,000 - 500,000 pounds
No reports
No reports
Source: USEPA, 2003
cis-l,2-Dichloroethylene is not listed as a Toxics Release Inventory (TRI) chemical; thus,
no TRI release records are available.
21.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of cis-1,2-
dichloroethylene in ambient water are available from the NAWQA program.
21.3.1 EPA Summary Analysis of NAWQA Data
EPA, with the cooperation of the USGS, has performed a summary analysis of all Cycle 1
water monitoring data from all study units (1992-2001) for cis-l,2-dichloroethylene. Detection
frequencies were computed as the percentage of samples and sites with detections (i.e., with at
least one result equal to or greater than the reporting limit). Sample detections can be biased by
frequent sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 21-2. Overall, cis-1,2-
dichloroethylene was detected in 9.9% of samples and at 3.8% of sites. cis-l,2-Dichloroethylene
was detected more frequently in surface water than in ground water. The median concentration
based on detections from all sites was 0.049 |ig/L. The 99th percentile concentration based on
detections from all sites was 9.4 |ig/L.
21-2
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 21-2: EPA Summary Analysis of cis-1,2-Dichloroethylene Data from
NAWQA Study Units, 1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
4,658
1,402
6,060
% Samples
with
Detections
3.1%
32.4%
9.9%
Number
of Sites
4,159
182
4,341
% Sites
with
Detections
2.5%
35.7%
3.8%
Concentration Values
(of detections, in ug/L)
Minimum
0.003
0.005
0.003
Median
0.2
0.04
0.049
95th
Percen-
tile
6.2
0.5707
1.2
99th
Percen-
tile
71
4.67
9.4
Maximum
82
7.62
82
1. RLs (Reporting Limits) forcis-1,2-dichloroethylene varied, but did not exceed 0.005 pg/L
21.4 Occurrence in Drinking Water
cis-l,2-Dichloroethylene is regulated as a volatile organic compound (VOC) in drinking
water. All non-purchased community water systems (CWSs) and non-transient non-community
water systems (NTNCWSs) are required to sample for VOCs. The maximum waiver period for
VOCs is six years for ground water systems and three years for surface water systems.
All CWSs and NTNCWSs must collect four consecutive quarterly samples during the
initial three-year compliance period.l If all four samples are non-detections, then the system may
reduce to annual sampling. After three annual samples without a detection, a system may be
granted a waiver. If a compound is detected (but at less than the MCL), the system must take one
sample per quarter until results are below the MCL (minimum of two quarterly samples for
ground water systems and four quarterly samples for surface water systems). If all quarterly
samples are below the MCL, the system may return to annual sampling. If a compound is
detected at a level greater than the MCL, the system (whether ground water or surface water)
must take four consecutive quarterly samples until all are below the MCL. If all quarterly
samples are below the MCL, the system may return to annual sampling.
The analysis of cis-l,2-dichloroethylene occurrence presented in the following section is
based on state compliance monitoring data from the Six-Year Review-ICR Dataset. This is the
largest and most comprehensive compliance monitoring data set compiled by EPA's Drinking
Water Program to date.
Forty-four of the Six-Year Review-ICR states provided occurrence data for cis-1,2-
dichloroethylene. (There were no cis-l,2-dichloroethylene data from Hawaii.) These data consist
of 373,316 analytical results from 50,314 public water systems (PWSs) during the period from
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
21-3
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
1998 to 2005. The number of sample results and systems vary by state, although the state data
sets have been reviewed and checked to ensure adequacy of coverage and completeness.
21.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 21-3
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For cis-l,2-dichloroethylene, 0.964% of 50,314
systems reported detections. Exhibit 21-4 lists the minimum, median, 90th percentile, and
maximum cis-l,2-dichloroethylene concentrations based on detections from all systems in the
Six-Year Review-ICR Dataset. The median concentration of cis-l,2-dichloroethylene, based on
detections from all systems, is 1.1 |ig/L.
Exhibit 21-3: cis-1,2-Dichloroethylene Occurrence Data from the
Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
287,606
46,072
85,155,955
Surface Water
85,710
4,242
140,459,779
Combined Ground &
Surface Water
373,316
50,314
225,615,734
Percent with Detections
Ground Water
1.506%
0.914%
7.828%
Surface Water
3.046%
1.509%
8.808%
Combined Ground &
Surface Water
1.860%
0.964%
8.438%
Exhibit 21-4: cis-1,2-Dichloroethylene Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.01
Median
1
90tn
Percentile
5
Maximum
220
21-4
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source Water Type
Surface Water
Detection Value (ug/L)
Minimum
0.008
Median
1.2
90tn
Percentile
5
Maximum
160
Combined Ground &
Surface Water
0.008
1.1
5
220
The following maps illustrate the geographic distribution of cis-l,2-dichloroethylene
occurrence in drinking water. Exhibit 21-5 shows the states with systems with at least one
detection and Exhibit 21-6 shows the states with systems with at least one detection greater than
the MCL concentration. Note that five states did not submit data for use in the Six-Year Review
(Kansas,2 Louisiana, Mississippi, Pennsylvania, and Washington). Hawaii did submit Six-Year
data for most contaminants, but did not submit data for cis-l,2-dichloroethylene.
The distribution of systems with detections of cis-l,2-dichloroethylene is geographically
dispersed and detection rates were generally low. Sixteen states reported detections in more than
1% of their systems. In eight states, between 0.5% and 1% of systems reported detections.
Seventeen states reported detections in less than 0.5% of systems. Four states reported detections
greater than the MCL concentration of 70 |ig/L.
Exhibit 21-5: Percentage of Systems with at Least One cis-1,2-Dichloroethylene
Detection, by State
////\ Slates with Waivers or Not Submitting
States with No Detections
• Less than 0.5% of Systems Detecting
Between 0.5% and 1% of Systems Detecting
More than 1% of Systems Detecting
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
21-5
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 21-6: Percentage of Systems with at Least One cis-1,2-Dichloroethylene
Detection Greater than the MCL Concentration (> 70 ug/L), by State
States with Waivers or Not Submitting
States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
| Between 0.1% and 0.5% of Systems with Detections > MCL
j More than 0.5% of Systems with Detections > MCL
Exhibit 21-7 presents the Stage 1 analysis of cis-l,2-dichloroethylene occurrence in
drinking water from systems and population-served by those systems in the Six-Year Review-
ICR Dataset relative to two thresholds: 35 jig/L and 70 |ig/L. Thirteen (0.026% of) systems,
serving almost 550,000 persons, reported at least one detection greater than or equal to 35 |ig/L;
and 5 (0.010% of) systems, serving almost 167,000 persons, reported at least one detection
greater than 70 |ig/L.
Exhibit 21-7: cis-1,2-Dichloroethylene Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 70 |jg/L
> 35 |jg/L
Number of
Systems
Exceeding
Threshold
3
10
Percent of
Systems
Exceeding
Threshold
0.007%
0.022%
Total Population-
Served by
Systems
Exceeding
Threshold
37,997
218,371
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.045%
0.256%
Surface
Water
> 70 |jg/L
> 35 |jg/L
2
3
0.047%
0.071%
128,756
328,756
0.092%
0.234%
21-6
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source
Water
Type
Combined
Ground &
Surface
Water
Threshold
> 70 |jg/L
> 35 |jg/L
Number of
Systems
Exceeding
Threshold
5
13
Percent of
Systems
Exceeding
Threshold
0.010%
0.026%
Total Population-
Served by
Systems
Exceeding
Threshold
166,753
547,127
Percent of
Population-Served
by Systems
Exceeding
Threshold
0.074%
0.243%
21.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 1996. Toxicological Profile for
1,2-Dichloroethene. August 1996. Available on the Internet at:
http://www.atsdr.cdc.gov/toxprofiles/tp87.html.
United States Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - cis-l,2-Dichloroethylene. Last modified September 10, 2007. Available on the
Internet at: http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for cis-1,2-
dichloroethylene.] Accessed February 21, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
21-7
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
22 trans-l,2-Dichloroethylene
This chapter on trans- 1,2-dichloroethylene is part of a report that is organized so that each
chapter presents information on one specific contaminant. Chapter 1 of this report, Introduction,
presents background information on all sources of data used as well as the analytical approach
used to estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and trans-1,2-
dichloroethylene occurrence estimates in ambient water and drinking water. All drinking water
occurrence estimates were based on data from the National Compliance Monitoring Information
Collection Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR
Dataset"). For detailed information regarding this dataset, data management, data quality
assessments, and the analytical approach used to generate all contaminant occurrence estimates
presented in this chapter, please refer to USEPA (2009).
22.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for trans-1,2-dichloroethylene on
January 30, 1991 (56 FR 3526 (USEPA, 1991)). The NPDWR established a maximum
contaminant level goal (MCLG) and a maximum contaminant level (MCL) of 100 |ig/L. The
Agency developed the MCLG based on a reference dose (RfD) of 20 jig/kg-day (0.02 mg/kg-day)
and a cancer classification of D, not classifiable as to human carcinogenicity.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 1996),
1,2-dichloroethylene (dEfeC^is a highly flammable, colorless liquid with a sharp, harsh odor
that can be smelled in very small amounts. Two slightly different forms exist, a "cis" form and a
"trans" form. When 1,2-dichloroethylene is released to land or water, most of it evaporates into
the air. 1,2-Dichloroethylene below soil surfaces in landfills or hazardous waste sites may
dissolve in water and possibly contaminate groundwater (ATSDR, 1996). 1,2-Dichloroethylene
is also known as 1,2-dichloroethene and 1,2-DCE.
22.2 Use, Production, and Releases
1,2-Dichloroethylene is used most often to produce solvents and in chemical mixtures.
Specifically, it is used as a solvent for waxes and resins; in the extraction of rubber; as a
refrigerant; in the manufacture of pharmaceuticals and artificial pearls; in the extraction of oils
and fats from fish and meat; and in making other organic compounds. The trans isomer is more
widely used in industry than either the cis isomer or the commercial mixture (ATSDR, 1996).
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 22-1 presents the production of trans-1,2-dichloroethylene in the United States
22-1
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
from 1986 to 2002. Note that the production of trans- 1,2-dichloroethylene in the United States
has fluctuated since 1986.
Exhibit 22-1: Production of trans-1,2-Dichloroethylene in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
10,000 - 500,000 pounds
> 1 million - 10 million pounds
> 1 million - 10 million pounds
10,000 - 500,000 pounds
> 1 million - 10 million pounds
Source: USEPA, 2003
trans-1,2-Dichloroethylene is not listed as a Toxics Release Inventory (TRI) chemical;
thus, no TRI release records are available.
22.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of trans-1,2-
dichloroethylene in ambient water are available from the NAWQA program.
22.3.1 EPA Summary Analysis of NAWQA Data
EPA, with the cooperation of the USGS, has performed a summary analysis of all Cycle 1
water monitoring data from all study units (1992-2001) for trans-1,2-dichloroethylene. Detection
frequencies were computed as the percentage of samples and sites with detections (i.e., with at
least one result equal to or greater than the reporting limit). Sample detections can be biased by
frequent sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 22-2. Overall, trans-1,2-
dichloroethylene was detected in 0.9% of samples and at 0.8% of sites, trans-1,2-
Dichloroethylene was detected more frequently in surface water than in ground water. The
median concentration based on detections from all sites was 0.029 |ig/L. The 99th percentile
concentration based on detections from all sites was 5.6 |ig/L.
22-2
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 22-2: EPA Summary Analysis of trans-1,2-Dichloroethylene Data from
NAWQA Study Units, 1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
4,658
1,413
6,071
% Samples
with
Detections
0.6%
1.6%
0.9%
Number
of Sites
4,159
190
4,349
% Sites
with
Detections
0.6%
5.3%
0.8%
Concentration Values
(of detections, in ug/L)
Minimum
0.0038
0.0053
0.0038
Median
0.3
0.01595
0.029
95th
Percen-
tile
5.3
2.83
4.5
99th
Percen-
tile
5.6
3.52
5.6
Maximum
5.6
3.52
5.6
1. RLs (Reporting Limits) for trans-1,2-dichloroethylene varied, but did not exceed 0.0053 pg/L
22.4 Occurrence in Drinking Water
trans-1,2-Dichloroethylene is regulated as a volatile organic compound (VOC) in
drinking water. All non-purchased community water systems (CWSs) and non-transient non-
community water systems (NTNCWSs) are required to sample for VOCs. The maximum waiver
period for VOCs is six years for ground water systems and three years for surface water systems.
All CWSs and NTNCWSs must collect four consecutive quarterly samples during the
initial three-year compliance period.l If all four samples are non-detections, then the system may
reduce to annual sampling. After three annual samples without a detection, a system may be
granted a waiver. If a compound is detected (but at less than the MCL), the system must take one
sample per quarter until results are below the MCL (minimum of two quarterly samples for
ground water systems and four quarterly samples for surface water systems). If all quarterly
samples are below the MCL, the system may return to annual sampling. If a compound is
detected at a level greater than the MCL, the system (whether ground water or surface water)
must take four consecutive quarterly samples until all are below the MCL. If all quarterly
samples are below the MCL, the system may return to annual sampling.
The analysis of trans-1,2-dichloroethylene occurrence presented in the following section
is based on state compliance monitoring data from the Six-Year Review-ICR Dataset. This is the
largest and most comprehensive compliance monitoring data set compiled by EPA's Drinking
Water Program to date.
Forty-four of the Six-Year Review-ICR states provided occurrence data for trans-1,2-
dichloroethylene. (There were no trans-1,2-dichloroethylene data from Hawaii.) These data
consist of 371,258 analytical results from 50,319 public water system (PWSs) during the period
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
22-3
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from 1998 to 2005. The number of sample results and systems vary by state, although the state
data sets have been reviewed and checked to ensure adequacy of coverage and completeness.
22.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 22-3
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For trans-1,2-dichloroethylene, 0.189% of 50,319
systems reported detections. Exhibit 22-4 lists the minimum, median, 90th percentile, and
maximum trans-1,2-dichloroethylene concentrations based on detections from all systems in the
Six-Year Review-ICR Dataset. The median concentration of trans-1,2-dichloroethylene, based on
detections from all systems, is 1 |ig/L.
Exhibit 22-3: trans-1,2-Dichloroethylene Occurrence Data from the
Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
286,957
46,078
85,155,343
Surface Water
84,301
4,241
140,455,794
Combined Ground &
Surface Water
371,258
50,319
225,611,137
Percent with Detections
Ground Water
0.089%
0.171%
1.908%
Surface Water
0.300%
0.377%
1.048%
Combined Ground &
Surface Water
0.137%
0.189%
1.372%
Exhibit 22-4: trans-1,2-Dichloroethylene Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.02
Median
0.6
90tn
Percentile
1.5
Maximum
24
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source Water Type
Surface Water
Detection Value (ug/L)
Minimum
0.2
Median
1.2
90tn
Percentile
6.9
Maximum
17
Combined Ground &
Surface Water
0.02
1
6.1
24
Exhibit 22-5 illustrates the geographic distribution of trans- 1,2-dichloroethylene
occurrence in drinking water, identifying the states with systems with at least one detection. (No
systems reported detections greater than the MCL concentration; thus, no map is included for
MCL concentration exceedances.) Note that five states did not submit data for use in the Six-
Year Review (Kansas2, Louisiana, Mississippi, Pennsylvania, and Washington). Hawaii did
submit Six-Year data for most contaminants, but did not submit data for trans-1,2-
dichloroethylene.
Detection rates were generally low for trans-1,2-dichloroethylene; only two states
reported detections in more than 0.5% of their systems. In 22 states, between 0.1% and 0.5% of
systems reported detections. Seventeen states reported no detections. Furthermore, no states
reported detections greater than the MCL concentration of 100 |ig/L.
Exhibit 22-5: Percentage of Systems with at Least One trans-1,2-Dichloroethylene
Detection, by State
'////; States with Waivers or Not Submitting
States with No Detections
BLess than 0.1% of Systems Detecting
Between 0.1% and 0.5% of Systems Detecting
^B More than 0.5% of Systems Detecting
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
22-5
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Exhibit 22-6 presents the Stage 1 analysis of trans-1,2-dichloroethylene occurrence in
drinking water from systems and population-served by those systems in the Six-Year Review-
ICR Dataset relative to two thresholds: 50 |ig/L and 100 |ig/L. No systems reported detections
greater than or equal to either threshold.
Exhibit 22-6: trans-1,2-Dichloroethylene Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 100|jg/L
> 50 |jg/L
Number of
Systems
Exceeding
Threshold
0
0
Percent of
Systems
Exceeding
Threshold
0.000%
0.000%
Total Population-
Served by
Systems
Exceeding
Threshold
0
0
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.000%
0.000%
Surface
Water
> 100|jg/L
> 50 |jg/L
0
0
0.000%
0.000%
0
0
0.000%
0.000%
Combined
Ground &
Surface
Water
> 100|jg/L
> 50 |jg/L
0
0
0.000%
0.000%
0
0
0.000%
0.000%
22.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 1996. Toxicological Profile for
1,2-Dichloroethene. August 1996. Available on the Internet at:
http://www.atsdr.cdc.gov/toxprofiles/tp87.html.
United States Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - trans-1,2-Dichloroethylene. Last modified September 10, 2007. Available on the
Internet at: http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for trans-1,2-
dichloroethylene. ] Accessed February 21, 2008.
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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. Office of Water. EPA-815-B-09-006. October 2009.
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23 Dinoseb
This chapter on dinoseb is part of a report that is organized so that each chapter presents
information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and dinoseb
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
23.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for dinoseb on July 17, 1992 (57 FR
31776 (USEPA, 1992)). The NPDWR established a maximum contaminant level goal (MCLG)
and a maximum contaminant level (MCL) of 7 |ig/L. The Agency developed the MCLG based on
a reference dose (RfD) of 1 |ig/kg-day (0.001 mg/kg-day) and a cancer classification of D, not
classifiable as to human carcinogenicity.
According to the Extension Toxicology Network (EXTOXNET, 1996), dinoseb
(CioHi2N2Os) is a dark reddish-brown solid or dark orange viscous liquid (depending on the
temperature). The use of dinoseb was cancelled in the United States in 1986. Dinoseb is not
commercially available in the United States. Because dinoseb binds weakly to soil and is
degraded slowly by soil bacteria, it can leach into ground water. In surface water, it is mainly
broken down by sunlight. It is not likely to accumulate in aquatic life (EXTOXNET, 1996).
23.2 Use, Production, and Releases
The greatest use of dinoseb is as an herbicide for post-emergence weed control in
soybeans, vegetables, fruits, nuts, citrus, and other field crops. Dinoseb is also used as an
insecticide in grapes, and as a seed crop drying agent (EXTOXNET, 1996).
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 23-1 presents the production of dinoseb in the United States from 1986 to 2002.
Note that the production of dinoseb in the United States has remained constant since 1986.
23-1
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 23-1: Production of Dinoseb in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
> 1 million - 10 million pounds
> 1 million - 10 million pounds
> 1 million - 10 million pounds
> 1 million - 10 million pounds
> 1 million - 10 million pounds
Source: USEPA, 2003
Dinoseb is not listed as a Toxics Release Inventory (TRI) chemical; thus, no TRI release
records are available.
23.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of dinoseb in
ambient water are available from the NAWQA program.
23.3.1 NA WQA Pesticide National Synthesis Project
The NAWQA Pesticide National Synthesis Project is a national-scale assessment of the
occurrence and behavior of pesticides in streams and ground water of the United States and the
potential for pesticides to adversely affect drinking water supplies or aquatic ecosystems. Under
the National Synthesis Project, the USGS monitored dinoseb between 1992 and 2001 in streams
and wells across the country (Gilliom etal., 2007). The maximum long-term method detection
limit for dinoseb was 0.040 |ig/L.
In NAWQA stream samples (Exhibit 23-2), dinoseb was found at frequencies ranging
from 0% of samples in undeveloped and urban areas to 0.02% of samples in mixed land use
settings, and 0.27% of samples in agricultural settings. The 95th percentile concentrations were
less than the method detection limit in all land use settings. The highest concentration, 1 |ig/L,
was found at an agricultural site.
23-2
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 23-2: USGS National Synthesis Summary of NAWQA Monitoring of
Dinoseb in Streams, 1992-2001
Land Use
Type
Agricultural
Mixed
Undeveloped
Urban
No. of Samples
(No. of Sites)
1,466(62)
800 (36)
101 (5)
521 (19)
Detection
Frequency
0.27%
0.02%
0.00%
0.00%
50tn Percent! le
(Median)
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
95th Percentile
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
Maximum
Concentration
(in ug/L)
1.000
0.270
ND1
ND1
Source: Gilliom et a/., 2007
1. ND = not detected (Concentration is less than the maximum long term method detection limit and is expected to
be less than any higher percentile concentration shown in the table)
In ground water NAWQA samples (Exhibit 23-3), dinoseb was found at frequencies
ranging from 0% of samples in undeveloped and urban areas to 0.32% in mixed land use settings,
and 0.76% of samples in agricultural settings. The 95th percentile concentrations were less than
the method detection limit in all settings. The highest concentration, 40 |ig/L, was found at an
agricultural site.
Exhibit 23-3: USGS National Synthesis Summary of NAWQA Monitoring of
Dinoseb in Ground Water, 1991-2001
Land Use Type
Agricultural
Mixed
Undeveloped
Urban
Number
of Wells
1,187
1,569
23
666
Detection
Frequency
0.76%
0.32%
0.00%
0.00%
50tn Percentile
(Median)
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
95th Percentile
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
Maximum
Concentration
(in ug/L)
40
19.2
ND1
ND1
Source: Gilliom et a/., 2007
1. ND = not detected (Concentration is less than the maximum long term method detection limit and is expected to
be less than any higher percentile concentration shown in the table)
23.3.2 EPA Summary Analysis of NAWQA Data
Whereas the NAWQA program often uses the most representative data for a site to
calculate summary statistics, EPA, with the cooperation of the USGS, has performed a summary
analysis of all Cycle 1 water monitoring data from all study units (1992-2001) for dinoseb.
Detection frequencies were computed as the percentage of samples and sites with detections (i.e.,
with at least one result equal to or greater than the reporting limit). Sample detections can be
biased by frequent sampling in areas with high (or low) occurrence. Calculating the percentage of
sites with detections can reduce this bias.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
The results of the EPA analysis are presented in Exhibit 23-4. Overall, dinoseb was
detected in 0.5% of samples and at 0.8% of sites. Dinoseb was detected more frequently in
surface water sites than in ground water sites. The median concentration based on detections
from all sites was 0.07 |ig/L. The 99th percentile concentration based on detections from all sites
was 40 |ig/L.
Exhibit 23-4: EPA Summary Analysis of Dinoseb Data from NAWQA Study Units,
1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
4,028
5,545
9,573
% Samples
with
Detections
0.8%
0.3%
0.5%
Number
of Sites
3,651
895
4,546
% Sites
with
Detections
0.8%
0.9%
0.8%
Concentration Values
(of detections, in ug/L)
Minimum
0.0058
0.02
0.0058
Median
0.06
0.13
0.07
95th
Percen-
tile
19.2
1
8
99th
Percen-
tile
40
1
40
Maximum
40
1
40
1. RLs (Reporting Limits) for dinoseb varied, but did not exceed 0.01 ug/L. Note that because this EPA analysis
involves more data points than the USGS analyses presented above, a direct comparison is not possible.
23.4 Occurrence in Drinking Water
Dinoseb is regulated as a synthetic organic chemical (SOC) in drinking water. All non-
purchased community water systems (CWSs) and non-transient non-community water systems
(NTNCWSs) are required to sample for SOCs. The maximum waiver period for SOCs is three
years, but this waiver can be renewed indefinitely. (Systems may receive a waiver at any time
without having collected an SOC sample. With a waiver, systems are not required to collect an
SOC sample.)
All CWSs and NTNCWSs without an SOC waiver must collect four consecutive
quarterly samples during the initial three-year compliance period.l If all four samples are non-
detections, then a system serving less than 3,300 persons may reduce to one sample during each
consecutive compliance period; a system serving more than 3,300 persons may reduce to two
quarterly samples within a 12-month period during a 3-year compliance period. If a chemical is
detected (but is less than the MCL), the system must take one sample per quarter until results are
below the MCL (minimum of two quarterly samples for ground water systems and four quarterly
samples for surface water systems). If all quarterly samples are below the MCL, the system may
return to annual sampling. If a chemical is detected at a level greater than the MCL, the system
(whether ground water or surface water) must take quarterly samples until four consecutive
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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quarters are below the MCL. If all quarterly samples are below the MCL, the system may return
to annual sampling.
The analysis of dinoseb occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
Forty-three of the Six-Year Review-ICR states provided occurrence data for dinoseb.
(There were no dinoseb data from Hawaii or Oklahoma.) These data consist of 121,896 analytical
results from 32,713 public water systems (PWSs) during the period from 1998 to 2005. The
number of sample results and systems vary by state, although the state data sets have been
reviewed and checked to ensure adequacy of coverage and completeness.
23.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 23-5
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For dinoseb, 0.266% of 32,713 systems reported
detections. Exhibit 23-6 lists the minimum, median, 90th percentile, and maximum dinoseb
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of dinoseb, based on detections from all systems, is 0.32 |ig/L.
Exhibit 23-5: Dinoseb Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
99,807
29,785
66,425,963
Surface Water
22,089
2,928
116,493,427
Combined Ground &
Surface Water
121,896
32,713
182,919,390
Percent with Detections
Ground Water
0.120%
0.235%
4.513%
Surface Water
0.118%
0.581%
2.274%
Combined Ground &
Surface Water
0.120%
0.266%
3.087%
23-5
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 23-6: Dinoseb Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.03
Median
0.385
90tn
Percentile
10.55
Maximum
45
Surface Water
0.07
0.3
3
3
Combined Ground &
Surface Water
0.03
0.32
9.2
45
The following maps illustrate the geographic distribution of dinoseb occurrence in
drinking water. Exhibit 23-7 shows the states with systems with at least one detection and
Exhibit 23-8 shows the states with systems with at least one detection greater than the MCL
concentration. Note that five states did not submit data for use in the Six-Year Review (Kansas2,
Louisiana, Mississippi, Pennsylvania, and Washington). Hawaii and Oklahoma did submit Six-
Year data for most contaminants, but did not submit data for dinoseb.
Detection rates were generally low for dinoseb. Only five states reported detections in
more than 1% of their systems. These states are all located in the eastern half of the United
States. In four states, between 0.5% and 1% of systems reported detections. Twenty-two states
reported no detections. Three states reported detections greater than the MCL concentration of 7
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 23-7: Percentage of Systems with at Least One Dinoseb Detection,
by State
Estates with Waivers or Not Submitting
States with No Detections
Less than 0.5% of Systems Detecting
Between 0.5% and 1% of Systems Detecting
More than 1% of Systems Detecting
Exhibit 23-8: Percentage of Systems with at Least One Dinoseb Detection Greater
than the MCL Concentration (> 7 [iglL), by State
fflft States with Waivers or Not Submitting
States with No Detections > MCL
Less than 0.5% of Systems with Detections > MCL
^B Between 0.5% and 1% of Systems with Detections > MCL
H More than 1% of Systems with Detections > MCL
Exhibit 23-9 presents the Stage 1 analysis of dinoseb occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 3.5 |ig/L and 7 |ig/L. Six ground water systems, serving about 26,000 persons,
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
reported at least one detection greater than or equal to 3.5 |ig/L; and 5 ground water systems,
serving about 26,000 persons, reported at least one detection greater than 7 |ig/L. No surface
water systems reported detections greater than or equal to either threshold.
Exhibit 23-9: Dinoseb Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 7 |jg/L
>3.5|jg/L
Number of
Systems
Exceeding
Threshold
5
6
Percent of
Systems
Exceeding
Threshold
0.017%
0.020%
Total Population-
Served by
Systems
Exceeding
Threshold
26,212
26,292
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.039%
0.040%
Surface
Water
> 7 |jg/L
>3.5|jg/L
0
0
0.000%
0.000%
0
0
0.000%
0.000%
Combined
Ground &
Surface
Water
> 7 |jg/L
>3.5 |jg/L
5
6
0.015%
0.018%
26,212
26,292
0.014%
0.014%
23.5 References
Extension Toxicology Network (EXTOXNET). 1996. EXTOXNET Pesticide Information
Profiles-Dinoseb. Last modified June 1996. Available on the Internet at:
http://extoxnet.orst.edu/pips/dinoseb.htm. Accessed July 6, 2008.
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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
United States Environmental Protection Agency (USEPA). 1992. Drinking Water; National
Primary Drinking Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals;
National Primary Drinking Water Regulations Implementation; Final Rule. Federal Register.
Vol. 57, No. 138. p. 31776, July 17, 1992.
USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - Dinoseb. Last modified September 10, 2007. Available on the Internet at:
http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for dinoseb.] Accessed February
21,2008.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
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. Office of Water. EPA-815-B-09-006. October 2009.
23-9
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24 Diquat
This chapter on diquat is part of a report that is organized so that each chapter presents
information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and diquat
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
24.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for diquat on July 17, 1992 (57 FR
31776 (USEPA, 1992)). The NPDWR established a maximum contaminant level goal (MCLG)
and a maximum contaminant level (MCL) of 20 |ig/L. The Agency developed the MCLG based
on a reference dose (RfD) of 2.2 jig/kg-day (0.0022 mg/kg-day) and a cancer classification of D,
not classifiable as to human carcinogenicity.
According to the Extension Toxicology Network (EXTOXNET, 1996), diquat
(Ci2Hi2N22+) is an organic solid of white or yellow crystals. Diquat is a non-selective herbicide
that acts quickly to damage only the parts of the plant to which it is applied. It is persistent in
soils, adhering strongly to particles, and does not readily leach into water. If applied to water, a
portion will become associated with particles in the water, and the rest will break down quickly
due to sunlight and microbes (EXTOXNET, 1996).
24.2 Use, Production, and Releases
Diquat is a quick-acting contact herbicide that is used to control both crop and aquatic
weeds. It is used to desiccate potato vines and seed crops, and as a sugar cane-flowering
suppressant (EXTOXNET, 1996).
The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for diquat.
Exhibit 24-1, compiled by the United States Geological Survey (USGS, 2007), shows the
geographic distribution of estimated average annual diquat use in the United States from 1999
through 2004. A breakdown of use by crop is also included. The map was created by the USGS
using state-level data sets on pesticide use rates from 1999-2004 compiled by the CropLife
Foundation, at the Crop Protection Research Institute, combined with county-level data on
24-1
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
harvested crop acreage obtained from the 2002 Census of Agriculture. Due to the nature of the
data sources, non-agricultural uses are not reflected here, and variations in use at the county-
level are also not well represented (Thelin and Gianessi, 2000). The USGS (2007) estimates that
almost 195,000 pounds of diquat active ingredient were used on average each year between 1999
and 2004.
Exhibit 24-1: Estimated Annual Agricultural Use for Diquat (c. 2002)
DIQUAT - herbicide
2002 estimated annual agricultural use
Average annual use of
active ingredient
(pounds par square mile of agricultural
land in county)
D no estimated use
D 0.001 to 0.004
D 0.005 to 0.023
D 0.024 to 0.112
D 0.113 to 0.382
• >= 0.383
Crops
potatoes
tomatoes
alfalfa hay
bell peppers
eggplant
Total
Pounds Applied
174957
10182
9017
333
29
Percent
National Use
89.94
5.23
4.64
0.17
0.01
Source: USGS, 2007
Diquat is not listed as a Toxics Release Inventory (TRI) chemical; thus, no TRI release
records are available.
24.3 Occurrence in Ambient Water
No National Water Quality Assessment (NAWQA) Program data are available from the
USGS on the occurrence of diquat in ambient waters from the Pesticide National Synthesis
Project (Gilliom etal., 2007) or the EPA Summary Analysis of Cycle 1 data.
24.4 Occurrence in Drinking Water
Diquat is regulated as a synthetic organic chemical (SOC) in drinking water. All non-
purchased community water systems (CWSs) and non-transient non-community water systems
24-2
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
(NTNCWSs) are required to sample for SOCs. The maximum waiver period for SOCs is three
years, but this waiver can be renewed indefinitely. (Systems may receive a waiver at any time
without having collected an SOC sample. With a waiver, systems are not required to collect an
SOC sample.) Statewide waivers are often granted for diquat.
All CWSs and NTNCWSs without an SOC waiver must collect four consecutive
quarterly samples during the initial three-year compliance period.l If all four samples are non-
detections, then a system serving less than 3,300 persons may reduce to one sample during each
consecutive compliance period; a system serving more than 3,300 persons may reduce to two
quarterly samples within a 12-month period during a 3-year compliance period. If a chemical is
detected (but is less than the MCL), the system must take one sample per quarter until results are
below the MCL (minimum of two quarterly samples for ground water systems and four quarterly
samples for surface water systems). If all quarterly samples are below the MCL, the system may
return to annual sampling. If a chemical is detected at a level greater than the MCL, the system
(whether ground water or surface water) must take quarterly samples until four consecutive
quarters are below the MCL. If all quarterly samples are below the MCL, the system may return
to annual sampling.
The analysis of diquat occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
Diquat data were provided by 38 of the Six-Year Review-ICR states. (There were no
diquat data from the following states: Hawaii, Minnesota, Missouri, North Carolina, New
Hampshire, Oklahoma, and Texas.) These data consist of 55,634 analytical results from 15,595
public water systems (PWSs) during the period from 1998 to 2005. The number of sample results
and systems vary by state, although the state data sets have been reviewed and checked to ensure
adequacy of coverage and completeness.
24.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 24-2
presents the number of samples and systems, as well as the population-served by the systems,
and the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For diquat, 0.442% of 15,595 systems reported
detections. Exhibit 24-3 lists the minimum, median, 90th percentile, and maximum diquat
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of diquat, based on detections from all systems, is 0.8 |ig/L.
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the
MCL.
24-3
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 24-2: Diquat Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
43,185
14,021
45,472,880
Surface Water
12,449
1,574
75,149,767
Combined Ground &
Surface Water
55,634
15,595
120,622,647
Percent with Detections
Ground Water
0.171%
0.357%
6.430%
Surface Water
0.185%
1 .207%
7.498%
Combined Ground &
Surface Water
0.174%
0.442%
7.095%
Exhibit 24-3: Diquat Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.17
Median
0.75
90tn
Percentile
6.5
Maximum
9
Surface Water
0.08
2
6.9
13
Combined Ground &
Surface Water
0.08
0.8
6.5
13
Exhibit 24-4 illustrates the geographic distribution of diquat occurrence in drinking water,
identifying the states with systems with at least one detection. (No systems reported detections
greater than the MCL concentration; thus, no map is included for MCL concentration
exceedances.) Note that five states did not submit data for use in the Six-Year Review (Kansas2,
Louisiana, Mississippi, Pennsylvania, and Washington). Hawaii, Minnesota, Missouri, North
Carolina, New Hampshire, Oklahoma, and Texas did submit Six-Year data for most
contaminants but did not submit data for diquat.
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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Detection rates were generally low for diquat; only 2 states reported detections in more
than 5% of their systems. In seven states, between 1% and 5% of systems reported detections.
Twenty-one states reported no detections. Furthermore, no states reported detections greater than
the MCL concentration of 20 |ig/L.
Exhibit 24-4: Percentage of Systems with at Least One Diquat Detection,
by State
'///'_ States with Waivers or Not Submitting
States with No Detections
KLess than 1 % of Systems Detecting
Between 1% and 5% of Systems Detecting
More than 5% of Systems Detecting
Exhibit 24-5 presents the Stage 1 analysis of diquat occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 10 |ig/L and 20 |ig/L. Two surface water systems, serving about 68,000 persons,
reported at least one detection greater than or equal to 10 |ig/L. No systems reported detections
greater than 20 |ig/L.
Exhibit 24-5: Diquat Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 20 |jg/L
>10|jg/L
Number of
Systems
Exceeding
Threshold
0
0
Percent of
Systems
Exceeding
Threshold
0.000%
0.000%
Total Population-
Served by
Systems
Exceeding
Threshold
0
0
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.000%
0.000%
24-5
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source
Water
Type
Surface
Water
Threshold
> 20 |jg/L
>10|jg/L
Number of
Systems
Exceeding
Threshold
0
2
Percent of
Systems
Exceeding
Threshold
0.000%
0.127%
Total Population-
Served by
Systems
Exceeding
Threshold
0
68,095
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.000%
0.091%
Combined
Ground &
Surface
Water
> 20 |jg/L
>10|jg/L
0
2
0.000%
0.013%
0
68,095
0.000%
0.056%
24.5 References
Extension Toxicology Network (EXTOXNET). 1996. EXTOXNET Pesticide Information
Profiles- Diquat Dibromide. Last modified June 1996. Available on the Internet at:
http://extoxnet.orst.edu/pips/diquatdi.htm. Accessed July 7, 2008.
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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
Thelin, G.P. and L.P. Gianessi. 2000. Method for Estimating Pesticide Use for County Areas of
the Conterminous United States. U.S. Geological Survey Open-File Report 00-250, 62 p.
Available on the Internet at: http://ca.water.usgs.gov/pnsp/rep/ofr00250/ofr00250.pdf.
United States Environmental Protection Agency (USEPA). 1992. Drinking Water; National
Primary Drinking Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals;
National Primary Drinking Water Regulations Implementation; Final Rule. Federal Register.
Vol. 57, No. 138. p. 31776, July 17, 1992.
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. Office of Water. EPA-815-B-09-006. October 2009.
United States Geological Survey (USGS). 2007. 2002 Pesticide Use Maps. Available on the
Internet at:
http://water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=02&map=ml950.
Accessed March 6, 2008.
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25 Endrin
This chapter on endrin is part of a report that is organized so that each chapter presents
information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and endrin
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
25.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for endrin on July 17, 1992 (57 FR
31776 (USEPA, 1992)). The NPDWR established a maximum contaminant level goal (MCLG)
and a maximum contaminant level (MCL) of 2 |ig/L. The Agency developed the MCLG based on
a reference dose (RfD) of 0.3 jig/kg-day (0.0003 mg/kg-day) and a cancer classification of D, not
classifiable as to human carcinogenicity.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 1996),
endrin (C^HgCleO) is a solid, white, almost odorless substance that was used as a pesticide to
control insects, rodents, and birds. Since 1986, however, it has not been produced or sold for
general use in the United States. Endrin binds strongly to soil and does not easily leach into
ground water. It is very persistent in soil (lasting over 10 years). If released to water, it will
become associated with sediments, where it can last for a long time (ATSDR, 1996).
25.2 Use, Production, and Releases
Beginning in 1951, endrin was first used as an insecticide, rodenticide, and avicide to
control cutworms, voles, grasshoppers, borers, and other pests on cotton, sugarcane, tobacco,
apple orchards, and grain. It was also used as an insecticide on bird perches. Except for its use as
a toxicant on bird perches, which was canceled in 1991, all other uses of endrin in the United
States were voluntarily canceled by the manufacturer in 1986 (ATSDR, 1996).
The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for endrin.
Endrin is not listed as a Toxics Release Inventory (TRI) chemical; no TRI release records
are available.
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25.3 Occurrence in Ambient Water
No National Water Quality Assessment (NAWQA) Program data are available from the
United States Geological Survey (USGS) on the occurrence of endrin in ambient waters from the
Pesticide National Synthesis Project (Gilliom et a/., 2007) or the EPA Summary Analysis of
Cycle 1 data.
25.4 Occurrence in Drinking Water
Endrin is regulated as a synthetic organic chemical (SOC) in drinking water. All non-
purchased community water systems (CWSs) and non-transient non-community water systems
(NTNCWSs) are required to sample for SOCs. The maximum waiver period for SOCs is three
years, but this waiver can be renewed indefinitely. (Systems may receive a waiver at any time
without having collected an SOC sample. With a waiver, systems are not required to collect an
SOC sample.)
All CWSs and NTNCWSs without an SOC waiver must collect four consecutive
quarterly samples during the initial three-year compliance period. * If all four samples are non-
detections, then a system serving less than 3,300 persons may reduce to one sample during each
consecutive compliance period; a system serving more than 3,300 persons may reduce to two
quarterly samples within a 12-month period during a 3-year compliance period. If a chemical is
detected (but is less than the MCL), the system must take one sample per quarter until results are
below the MCL (minimum of two quarterly samples for ground water systems and four quarterly
samples for surface water systems). If all quarterly samples are below the MCL, the system may
return to annual sampling. If a chemical is detected at a level greater than the MCL, the system
(whether ground water or surface water) must take quarterly samples until four consecutive
quarters are below the MCL. If all quarterly samples are below the MCL, the system may return
to annual sampling.
The analysis of endrin occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
Forty-four of the Six-Year Review-ICR states provided occurrence data for endrin. (There
were no endrin data from Oklahoma.) These data consist of 134,336 analytical results from
32,783 public water system (PWSs) during the period from 1998 to 2005. The number of sample
results and systems vary by state, although the state data sets have been reviewed and checked to
ensure adequacy of coverage and completeness.
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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25.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 25-1
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For endrin, 0.143% of 32,783 systems reported
detections. Exhibit 25-2 lists the minimum, median, 90th percentile, and maximum endrin
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of endrin, based on detections from all systems, is 0.02 |ig/L.
Exhibit 25-1: Endrin Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
105,777
29,734
67,885,419
Surface Water
28,559
3,049
116,157,743
Combined Ground &
Surface Water
134,336
32,783
184,043,162
Percent with Detections
Ground Water
0.039%
0.101%
3.927%
Surface Water
0.105%
0.558%
3.690%
Combined Ground &
Surface Water
0.053%
0.143%
3.777%
Exhibit 25-2: Endrin Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.0025
Median
0.008
90tn
Percentile
0.14
Maximum
3.3
Surface Water
0.001
0.07
0.5
0.52
Combined Ground &
Surface Water
0.001
0.02
0.5
3.3
25-3
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
The following maps illustrate the geographic distribution of endrin occurrence in drinking
water. Exhibit 25-3 shows the states with systems with at least one detection and Exhibit 25-4
shows the states with systems with at least one detection greater than the MCL concentration.
Note that five states did not submit data for use in the Six-Year Review (Kansas2, Louisiana,
Mississippi, Pennsylvania, and Washington). Oklahoma submitted Six-Year data for most
contaminants; however, there is a statewide waiver for endrin in Oklahoma so no endrin data
were available from that state.
Detection rates were generally low; only 3 states reported detections in more than 1% of
their systems. These states are all located in the eastern half of the United States. In two states,
between 0.5% and 1% of systems reported detections. California was the only state that reported
detections greater than the MCL concentration of 2 |ig/L.
Exhibit 25-3: Percentage of Systems with at Least One Endrin Detection,
by State
y//\ States with Waivers or Not Submitting
States with No Detections
| Less than 0.5% of Systems Detecting
Between 0-5% and 1% of Systems Detecting
More than 1% of Systems Detecting
2 Kansas submitted data after the data management and analyses had been conducted; data from Kansas are not
included in the analyses.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 25-4: Percentage of Systems with at Least One Endrin Detection Greater
than the MCL Concentration (> 2 ug/L), by State
Estates with Waivers or Not Submitting
States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
Between 0.1% and 0.5% of Systems with Detections > MCL
H More than 0.5% of Systems with Detections > MCL
Exhibit 25-5 presents the Stage 1 analysis of endrin occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 1 |ig/L and 2 |ig/L. Two (0.006% of) systems, serving 2,800 persons, reported at
least one detection greater than or equal to 1 |ig/L; and 1 (0.003% of) systems, serving about 300
persons, reported at least one detection greater than 2 |ig/L. No surface water systems reported
detections greater than either threshold.
Exhibit 25-5: Endrin Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 2 |jg/L
> 1 H9/L
Number of
Systems
Exceeding
Threshold
1
2
Percent of
Systems
Exceeding
Threshold
0.003%
0.007%
Total Population-
Served by
Systems
Exceeding
Threshold
300
2,800
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.000%
0.004%
Surface
Water
> 2 |jg/L
> 1 |jg/L
0
0
0.000%
0.000%
0
0
0.000%
0.000%
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source
Water
Type
Combined
Ground &
Surface
Water
Threshold
> 2 |jg/L
> 1 H9/L
N umber of
Systems
Exceeding
Threshold
1
2
Percent of
Systems
Exceeding
Threshold
0.003%
0.006%
Total Population-
Served by
Systems
Exceeding
Threshold
300
2,800
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.000%
0.002%
25.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 1996. Toxicological Profile for
Endrin. August 1996. Available on the Internet at:
http://www.atsdr.cdc.gov/toxprofiles/tp89.html.
Gilliom, R.J., I.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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
United States Environmental Protection Agency (USEPA). 1992. Drinking Water; National
Primary Drinking Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals;
National Primary Drinking Water Regulations Implementation; Final Rule. Federal Register.
Vol. 57, No. 138. p. 31776, July 17, 1992.
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. Office of Water. EPA-815-B-09-006. October 2009.
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26 Ethylbenzene
This chapter on ethylbenzene is part of a report that is organized so that each chapter
presents information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and ethylbenzene
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
26.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for ethylbenzene on January 30, 1991
(56 FR 3526 (USEPA, 1991)). The NPDWR established a maximum contaminant level goal
(MCLG) and a maximum contaminant level (MCL) of 700 |ig/L. The Agency developed the
MCLG based on a reference dose (RfD) of 100 jig/kg-day (0.1 mg/kg-day) and a cancer
classification of D, not classifiable as to human carcinogenicity.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2007),
ethylbenzene (CgHio) is a colorless, flammable liquid that smells like gasoline. If released to
water, it will evaporate rapidly. It does not bind strongly to sediments and soils and can,
therefore, leach into ground water if released to land. It is susceptible to biodegradation.
Ethylbenzene does not accumulate significantly in aquatic organisms (ATSDR, 2007).
26.2 Use, Production, and Releases
The greatest use (more than 99%) of ethylbenzene is to make styrene. Consumer products
containing ethylbenzene include: gasoline; paints and inks; pesticides; carpet glues; varnishes
and paints; and tobacco products. It is also naturally found in coal tar and petroleum (ATSDR,
2007).
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 26-1 presents the production of ethylbenzene in the United States from 1986 to
2002. Note that the production of ethylbenzene in the United States has remained constant since
1986.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 26-1: Production of Ethylbenzene in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
> 1 billion pounds
> 1 billion pounds
> 1 billion pounds
> 1 billion pounds
> 1 billion pounds
Source: USEPA, 2003
Ethylbenzene is listed as a Toxics Release Inventory (TRI) chemical. TRI data indicate
that total off-site and on-site releases of ethylbenzene for the period 1998-2006 ranged from
approximately 5.7 million pounds to approximately 10 million pounds, with a general decrease
over time. On-site releases were greater than off-site releases (USEPA, 2008).
26.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of ethylbenzene
in ambient water are available from the NAWQA program.
26.3.1 EPA Summary Analysis of NAWQA Data
EPA, with the cooperation of the USGS, has performed a summary analysis of all Cycle 1
water monitoring data from all study units (1992-2001) for ethylbenzene. Detection frequencies
were computed as the percentage of samples and sites with detections (i.e., with at least one
result equal to or greater than the reporting limit). Sample detections can be biased by frequent
sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 26-2. Overall, ethylbenzene was
detected in 5.7% of samples and at 3.6% of sites. Ethylbenzene was detected more frequently in
surface water than in ground water. The median concentration based on detections from all sites
was 0.012 ng/L. The 99th percentile concentration based on detections from all sites was 51 |ig/L.
26-2
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 26-2: EPA Summary Analysis of Ethylbenzene Data from NAWQA Study
Units, 1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
4,653
1,402
6,055
% Samples
with
Detections
2.3%
17.3%
5.7%
Number
of Sites
4,153
182
4,335
% Sites
with
Detections
2.3%
31.3%
3.6%
Concentration Values
(of detections, in ug/L)
Minimum
0.002
0.002
0.002
Median
0.01
0.0132
0.012
95th
Percen-
tile
8.714
1.8
1.9
99th
Percen-
tile
270
1.9
51
Maximum
2100
3
2100
1. RLs (Reporting Limits) for ethylbenzene varied, but did not exceed 0.002 ug/L.
26.4 Occurrence in Drinking Water
Ethylbenzene is regulated as a volatile organic compound (VOC) in drinking water. All
non-purchased community water systems (CWSs) and non-transient non-community water
systems (NTNCWSs) are required to sample for VOCs. The maximum waiver period for VOCs
is six years for ground water systems and three years for surface water systems.
All CWSs and NTNCWSs must collect four consecutive quarterly samples during the
initial three-year compliance period.l If all four samples are non-detections, then the system may
reduce to annual sampling. After three annual samples without a detection, a system may be
granted a waiver. If a compound is detected (but at less than the MCL), the system must take one
sample per quarter until results are below the MCL (minimum of two quarterly samples for
ground water systems and four quarterly samples for surface water systems). If all quarterly
samples are below the MCL, the system may return to annual sampling. If a compound is
detected at a level greater than the MCL, the system (whether ground water or surface water)
must take four consecutive quarterly samples until all are below the MCL. If all quarterly
samples are below the MCL, the system may return to annual sampling.
The analysis of ethylbenzene occurrence presented in the following section is based on
state compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and
most comprehensive compliance monitoring data set compiled by EPA's Drinking Water
Program to date.
All of the Six-Year Review-ICR states provided occurrence data for ethylbenzene. These
data consist of 374,141 analytical results from 50,447 public water systems (PWSs) during the
period from 1998 to 2005. The number of sample results and systems vary by state, although the
state data sets have been reviewed and checked to ensure adequacy of coverage and
completeness.
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
26-3
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26.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 26-3
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For ethylbenzene, 3.909% of 50,447 systems reported
detections. Exhibit 26-4 lists the minimum, median, 90th percentile, and maximum ethylbenzene
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of ethylbenzene, based on detections from all systems, is 0.9 |ig/L.
Exhibit 26-3: Ethylbenzene Occurrence Data from the
Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
289,622
46,190
86,398,177
Surface Water
84,519
4,257
140,541,198
Combined Ground &
Surface Water
374,141
50,447
226,939,375
Percent with Detections
Ground Water
1.146%
3.750%
10.518%
Surface Water
0.629%
5.638%
12.681%
Combined Ground &
Surface Water
1.030%
3.909%
11.857%
Exhibit 26-4: Ethylbenzene Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.02
Median
0.9
90tn
Percentile
4.4
Maximum
557
Surface Water
0.002
0.9
6
97.5
26-4
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source Water Type
Combined Ground &
Surface Water
Detection Value (ug/L)
Minimum
0.002
Median
0.9
90tn
Percentile
4.6
Maximum
557
Exhibit 26-5 illustrates the geographic distribution of ethylbenzene occurrence in
drinking water, identifying the states with systems with at least one detection. (No systems
reported detections greater than the MCL concentration; thus, no map is included for MCL
concentration exceedances.) Note that five states did not submit data for use in the Six-Year
Review (Kansas2, Louisiana, Mississippi, Pennsylvania, and Washington).
The distribution of systems with detections of ethylbenzene is geographically dispersed.
Eleven states reported detections in more than 5% of systems. In 24 states, between 1% and 5%
of systems reported detections. Nine states reported detections in less than 1% of systems. No
states reported detections greater than the MCL concentration of 700 |ig/L.
Exhibit 26-5: Percentage of Systems with at Least One Ethylbenzene
Detection, by State
////% States Not Submitting Any Data
[ States with No Detections
Less than 1% of Systems Detecting
| Between 1% and 5% of Systems Detecting
^H More than 5% of Systems Detecting
Exhibit 26-6 presents the Stage 1 analysis of ethylbenzene occurrence in drinking water
from systems and population-served by those systems in the Six-Year Review-ICR Dataset
relative to two thresholds: 350 |ig/L and 700 |ig/L. Two ground water systems, serving almost
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
6,000 persons, reported at least one detection greater than or equal to 350 |ig/L. No systems
reported detections greater than 700 |ig/L.
Exhibit 26-6: Ethylbenzene Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 700 |jg/L
> 350 |jg/L
Number of
Systems
Exceeding
Threshold
0
2
Percent of
Systems
Exceeding
Threshold
0.000%
0.004%
Total Population-
Served by
Systems
Exceeding
Threshold
0
5,961
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.000%
0.007%
Surface
Water
> 700 |jg/L
> 350 |jg/L
0
0
0.000%
0.000%
0
0
0.000%
0.000%
Combined
Ground &
Surface
Water
> 700 |jg/L
> 350 |jg/L
0
2
0.000%
0.004%
0
5,961
0.000%
0.003%
26.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2007. Draft Toxicological Profile
for Ethylbenzene. September 2007. Available on the Internet at:
http://www.atsdr.cdc.gov/toxprofiles/tpllO.pdf.
United States Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - Ethylbenzene. Last modified September 10, 2007. Available on the Internet at:
http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for ethylbenzene.] Accessed
February 21,2008.
USEPA. 2008. TRI Explorer: Trends - Ethylbenzene. Released February 21, 2008. Available on
the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for ethylbenzene.] Accessed
March 8, 2008.
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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. Office of Water. EPA-815-B-09-006. October 2009.
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27 Ethylene Dibromide (EDB)
This chapter on ethylene dibromide (EDB) is part of a report that is organized so that each
chapter presents information on one specific contaminant. Chapter 1 of this report, Introduction,
presents background information on all sources of data used as well as the analytical approach
used to estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and ethylene
dibromide occurrence estimates in ambient water and drinking water. All drinking water
occurrence estimates were based on data from the National Compliance Monitoring Information
Collection Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR
Dataset"). For detailed information regarding this dataset, data management, data quality
assessments, and the analytical approach used to generate all contaminant occurrence estimates
presented in this chapter, please refer to USEPA (2009).
27.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for ethylene dibromide on January 30,
1991 (56 FR 3526 (USEPA, 1991)). The NPDWR established a maximum contaminant level
goal (MCLG) of zero based on a cancer classification of B2, probable human carcinogen. The
NPDWR also established a maximum contaminant level (MCL) of 0.05 |ig/L based on analytical
feasibility.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 1995),
ethylene dibromide ^FLjB^is a manufactured chemical that also occurs naturally in small
amounts in the ocean, where it is likely formed by algae and kelp. It is a colorless, heavy organic
liquid with a mild, sweet odor. It generally does not bind strongly to soil and will move through
soil into the groundwater where it hardly breaks down. If applied to surface water, it will
volatilize, and be broken down in the atmosphere. Other names for ethylene dibromide include
1,2-dibromoethane, EDB, and glycol bromide (ATSDR, 1995).
27.2 Use, Production, and Releases
Ethylene dibromide has been used as a pesticide in soil, and on citrus, vegetable, and
grain crops. Most of these uses were stopped by EPA in 1984. Another major use of ethylene
dibromide was as an additive in leaded gasoline. Uses today include treatment of logs for
termites and beetles, control of moths in beehives, and as a preparation for dyes and waxes
(ATSDR, 1995).
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 27-1 presents the production of ethylene dibromide in the United States from 1986
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to 2002. Note that the production of ethylene dibromide in the United States decreased from
1986 to 1998 and remained constant thereafter.
Exhibit 27-1: Production of Ethylene Dibromide in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
> 100 million - 500 million pounds
> 50 million - 100 million pounds
> 10 million - 50 million pounds
> 1 million - 10 million pounds
> 1 million - 10 million pounds
Source: USEPA, 2003
Ethylene dibromide is listed as a Toxics Release Inventory (TRI) chemical. (It is listed
under the synonym 1,2-dibromoethane.) TRI data indicate that total off-site and on-site releases
of ethylene dibromide for the period 1998-2006 ranged from approximately 5,600 pounds to
approximately 48,000 pounds, with maximum releases occurring in 1999. With the exception of
1999, on-site releases were greater than off-site releases (USEPA, 2008).
27.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of ethylene
dibromide in ambient water are available from the NAWQA program.
2 7.3.1 EPA Summary Analysis of NAWQA Data
EPA, with the cooperation of the USGS, has performed a summary analysis of all Cycle 1
water monitoring data from all study units (1992-2001) for ethylene dibromide. Detection
frequencies were computed as the percentage of samples and sites with detections (i.e., with at
least one result equal to or greater than the reporting limit). Sample detections can be biased by
frequent sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 27-2. Overall, ethylene
dibromide was detected in 0.3% of samples and at 0.2% of sites. Ethylene dibromide was only
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
detected in ground water. The median concentration based on detections in ground water was
0.098 ng/L. The 99th percentile concentration based on detections from all sites was 1.4 |ig/L.
Exhibit 27-2: EPA Summary Analysis of Ethylene Dibromide Data from NAWQA
Study Units, 1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
4,958
1,393
6,351
% Samples
with
Detections
0.4%
0.0%
0.3%
Number
of Sites
4,147
185
4,332
% Sites
with
Detections
0.2%
0.0%
0.2%
Concentration Values
(of detections, in ug/L)
Minimum
0.015
0.015
Median
0.098
0.098
95th
Percen-
tile
1.4
1.4
99th
Percen-
tile
1.4
1.4
Maximum
1.4
1.4
1. RLs (Reporting Limits) for ethylene dibromide varied, but did not exceed 0.036 ug/L.
27.4 Occurrence in Drinking Water
Ethylene dibromide is regulated as a synthetic organic chemical (SOC) in drinking water.
All non-purchased community water systems (CWSs) and non-transient non-community water
systems (NTNCWSs) are required to sample for SOCs. The maximum waiver period for SOCs is
three years, but this waiver can be renewed indefinitely. (Systems may receive a waiver at any
time without having collected an SOC sample. With a waiver, systems are not required to collect
an SOC sample.) Statewide waivers are often granted for ethylene dibromide.
All CWSs and NTNCWSs without an SOC waiver must collect four consecutive
quarterly samples during the initial three-year compliance period.l If all four samples are non-
detections, then a system serving less than 3,300 persons may reduce to one sample during each
consecutive compliance period; a system serving more than 3,300 persons may reduce to two
quarterly samples within a 12-month period during a 3-year compliance period. If a chemical is
detected (but is less than the MCL), the system must take one sample per quarter until results are
below the MCL (minimum of two quarterly samples for ground water systems and four quarterly
samples for surface water systems). If all quarterly samples are below the MCL, the system may
return to annual sampling. If a chemical is detected at a level greater than the MCL, the system
(whether ground water or surface water) must take quarterly samples until four consecutive
quarters are below the MCL. If all quarterly samples are below the MCL, the system may return
to annual sampling.
The analysis of ethylene dibromide occurrence presented in the following section is based
on state compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
and most comprehensive compliance monitoring data set compiled by EPA's Drinking Water
Program to date.
Forty-three of the Six-Year Review-ICR states provided occurrence data for ethylene
dibromide. (There were no ethylene dibromide data from Maryland or Oklahoma.) These data
consist of 218,797 analytical results from 36,215 public water systems (PWSs) during the period
from 1998 to 2005. The number of sample results and systems vary by state, although the state
data sets have been reviewed and checked to ensure adequacy of coverage and completeness.
27.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 27-3
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For ethylene dibromide, 0.538% of 36,215 systems
reported detections. Exhibit 27-4 lists the minimum, median, 90th percentile, and maximum
ethylene dibromide concentrations based on detections from all systems in the Six-Year Review-
ICR Dataset. The median concentration of ethylene dibromide, based on detections from all
systems, is 0.04 |ig/L.
Exhibit 27-3: Ethylene Dibromide Occurrence Data from the
Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
173,371
33,245
72,299,607
Surface Water
45,426
2,970
115,854,308
Combined Ground &
Surface Water
218,797
36,215
188,153,915
Percent with Detections
Ground Water
0.433%
0.442%
5.930%
Surface Water
1 .228%
1.616%
7.544%
Combined Ground &
Surface Water
0.598%
0.538%
6.924%
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 27-4: Ethylene Dibromide Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.001387
Median
0.04
90tn
Percentile
0.33
Maximum
1.6
Surface Water
0.01
0.04
0.16
0.5
Combined Ground &
Surface Water
0.001387
0.04
0.23
1.6
The following maps illustrate the geographic distribution of ethylene dibromide
occurrence in drinking water. Exhibit 27-5 shows the states with systems with at least one
detection and Exhibit 27-6 shows the states with systems with at least one detection greater than
the MCL concentration. Note that five states did not submit data for use in the Six-Year Review
(Kansas2, Louisiana, Mississippi, Pennsylvania, and Washington). Maryland and Oklahoma did
submit Six-Year data for most contaminants, but did not submit data for ethylene dibromide.
The distribution of systems with detections of ethylene dibromide is geographically
dispersed, and detection rates were generally low. Seven states reported detections in more than
1% of their systems. Eight states reported detections in 0.5% to 1% of systems. Seventeen states
reported no detections. Seventeen states reported detections greater than the MCL concentration
of 0.05 |ig/L.
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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Exhibit 27-5: Percentage of Systems with at Least One Ethylene Dibromide
Detection, by State
Estates with Waivers or Not Submitting
States with No Detections
Less than 0.5% of Systems Detecting
Between 0.5% and 1% of Systems Detecting
More than 1% of Systems Detecting
Exhibit 27-6: Percentage of Systems with at Least One Ethylene Dibromide
Detection Greater than the MCL Concentration (> 0.05 iig/L), by State
fflft States with Waivers or Not Submitting
States with No Detections > MCL
Less than 0.5% of Systems with Detections > MCL
^B Between 0.5% and 1% of Systems with Detections > MCL
H More than 1% of Systems with Detections > MCL
Exhibit 27-7 presents the Stage 1 analysis of ethylene dibromide occurrence in drinking
water from systems and population-served by those systems in the Six-Year Review-ICR Dataset
relative to two thresholds: 0.025 |ig/L and 0.05 |ig/L. More than 120 (0.337% of) systems,
27-6
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
serving more than 3.0 million persons, reported at least one detection greater than or equal to
0.025 ng/L; and 88 (0.243% of) systems, serving almost 2.3 million persons, reported at least one
detection greater than 0.05 |ig/L.
Exhibit 27-7: Ethylene Dibromide Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 0.05 |jg/L
>0.025|jg/L
Number of
Systems
Exceeding
Threshold
67
96
Percent of
Systems
Exceeding
Threshold
0.202%
0.289%
Total Population-
Served by
Systems
Exceeding
Threshold
449,648
1,143,149
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.622%
1.581%
Surface
Water
> 0.05 |jg/L
>0.025|jg/L
21
26
0.707%
0.875%
1,810,412
1,894,232
1.563%
1.635%
Combined
Ground &
Surface
Water
> 0.05 |jg/L
> 0.025 |jg/L
88
122
0.243%
0.337%
2,260,060
3,037,381
1.201%
1.614%
27.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 1995. ToxFAQsfor 1,2-
Dibromoethane. September 1995. Available on the Internet at:
http://www.atsdr.cdc.gov/tfacts37.html.
United State Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - Ethylene Dibromide. Last modified September 10, 2007. Available on the Internet
at: http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for ethylene dibromide.]
Accessed February 21, 2008.
USEPA. 2008. TRI Explorer: Trends - 1,2-Dibromoethane. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for 1,2-
dibromoethane.] Accessed March 9, 2008.
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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. Office of Water. EPA-815-B-09-006. October 2009.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
28 Fluoride
This chapter on fluoride is part of a report that is organized so that each chapter presents
information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and fluoride
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter please refer to USEPA (2009).
28.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for fluoride on April 2, 1986 (51 FR
11396 (USEPA, 1986)). The NPDWR established a maximum contaminant level goal (MCLG)
and a maximum contaminant level (MCL) of 4 mg/L. At the same time, EPA published a
secondary maximum contaminant level (SMCL) for fluoride of 2 mg/L to protect against dental
fluorosis, which is considered to be an adverse cosmetic effect.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2003), the
term "fluorides" is used to refer to the common salts of the element fluorine, with the most
common salts being sodium fluoride and calcium fluoride. Both salts are white solids, but
sodium fluoride readily dissolves in water while calcium fluoride does not. Fluorine, the element,
is a pale, yellow-green, irritating gas that has a strong, sharp odor. It is so chemically reactive that
it is almost always found naturally combined with metals as a salt. Because health effects are due
to the fluoride ion, the term "fluoride" is most commonly used in discussing health effects and
regulations (ATSDR, 2003).
Fluorides occur naturally in a variety of geologic settings (e.g., in sedimentary and
volcanic rocks) in coal, clay, and certain minerals, and also are found in sea water. Fluoride
concentrations are typically higher in ground water than surface water because fluoride is leached
from rocks through which the ground water flows (ATSDR, 2003). Fluoride may be released to
the air by volcanic activity, the burning of coal, and the aerosolization of soil particles (ATSDR,
2003).
Fluoride is unique as a drinking water contaminant because of its beneficial effects at low
level exposures, and because it is voluntarily added to some drinking water systems as a public
health measure for reducing the incidence of cavities among the treated population. The amount
of fluoride added to drinking water for fluoridation ranges from 0.7 to 1.2 mg/L, depending on
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ambient air temperatures. The decision to fluoridate a water supply is made by the state or local
municipality, and is not mandated by EPA or any other Federal entity (USEPA, 2002).
28.2 Use, Production, and Releases
The main use of sodium fluoride is as a drinking water additive for prevention of tooth
decay. It is also used as a component of laundry sours (for removal of iron stains), in wood
preservation compounds, and in rimmed steel manufacturing (ATSDR, 2003). The most
important use of hydrogen fluoride is in the production of fluorocarbon chemicals (ATSDR,
2003). Demand for hydrogen fluoride to make fluorocarbons is increasing; fluorocarbon
refrigerants are an alternative to ozone-depleting chlorofluorocarbons. The next most important
uses of hydrogen fluoride are: chemical derivatives, 18%; aluminum manufacturing, 6%;
stainless steel pickling, 5%; petroleum alkylation catalysts, 4%; and uranium chemicals
production, 3% (ATSDR, 2003). Miscellaneous other uses include glass etching, herbicides, and
rare metals (ATSDR, 2003).
The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for fluoride.
Fluorine and hydrogen fluoride are both listed as Toxics Release Inventory (TRI)
chemicals. TRI data indicate that total off-site and on-site releases of hydrogen fluoride for the
period 1998-2006 ranged from approximately 72.7 million pounds to about 83.2 million pounds,
with a general decrease over time. On-site releases were greater than off-site releases (USEPA,
2008a). TRI data for fluorine indicate that total releases ranged from about 60,000 pounds to
more than 261,000 pounds, with a decrease over time. On-site releases were greater than off-site
releases (USEPA, 2008b).
28.3 Occurrence in Ambient Water
No National Water Quality Assessment (NAWQA) Program data are available from the
United States Geological Survey (USGS) on the occurrence of fluoride in ambient waters from
the Pesticide National Synthesis Project (Gilliom et a/., 2007) or the EPA Summary Analysis of
Cycle 1 data.
28.4 Occurrence in Drinking Water
Fluoride is regulated as an inorganic chemical (IOC) in drinking water. All community
water systems (CWSs) are required to sample for fluoride.l The maximum waiver period for
lOCs is nine years.
Ground water systems must sample once during the initial three-year compliance period.
After three compliance periods without a detection, a ground water system may be granted a
nine-year waiver. Surface water systems must sample annually during the initial three-year
1 Data for both CWSs and non-transient non-community water systems (NTNCWSs) were analyzed for the Second
Six-Year Review.
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compliance period. After three annual samples without a detection, a surface water system may
be granted a nine-year waiver. If the results are greater than the MCL, the public water system
(PWS) must take one sample per quarter until results are below the MCL (minimum of two
quarterly samples for ground water systems and four quarterly samples for surface water
systems). 2 If all quarterly samples are below the MCL, the system may continue at initial
monitoring indefinitely until the state or EPA establishes an alternate schedule. PWSs exceeding
the fluoride SMCL of 2 mg/L must provide public notification to their customers.
The analysis of fluoride occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
All of the Six-Year Review-ICR states provided occurrence data for fluoride. These data
consist of 333,211 analytical results from 48,600 systems during the period from 1998 to 2005.
The number of sample results and systems vary by state, although the state data sets have been
reviewed and checked to ensure adequacy of coverage and completeness.
28.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 28-1
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For fluoride, 79.276% of 48,600 systems reported
detections (which is expected since, as previously mentioned, it is voluntarily added to some
drinking water systems as a public health measure). Exhibit 28-2 lists the minimum, median, 90th
percentile, and maximum fluoride concentrations based on detections from all systems in the Six-
Year Review-ICR Dataset. The median concentration of fluoride, based on detections from all
systems, is 0.79 mg/L.
Exhibit 28-1: Fluoride Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
249,831
44,577
85,996,458
Surface Water
83,380
4,023
147,572,741
All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
28-3
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source Water Type
Combined Ground &
Surface Water
Number of
Samples
333,211
Number of
Systems
48,600
Population-
Served by
Systems
233,569,199
Percent with Detections
Ground Water
80.310%
78.991%
90.508%
Surface Water
85.166%
82.426%
96.708%
Combined Ground &
Surface Water
81.525%
79.276%
94.425%
Exhibit 28-2: Fluoride Summary Statistics
Source Water Type
Ground Water
Detection Value (mg/L)
Minimum
0.0001
Median
0.73
90tn
Percentile
1.5
Maximum
38
Surface Water
0.00006
0.86
1.27
29.2
Combined Ground &
Surface Water
0.00006
0.79
1.4
38
The following maps illustrate the geographic distribution of fluoride occurrence in
drinking water. Exhibit 28-3 shows the states with systems with at least one detection and
Exhibit 28-4 shows the states with systems with at least one detection greater than the MCL
concentration. Note that five states did not submit data for use in the Six-Year Review (Kansas3,
Louisiana, Mississippi, Pennsylvania, and Washington).
The distribution of systems with detections of fluoride is geographically dispersed.
Detection rates were high; all states reported detections of fluoride. Eleven states reported that
more than 95% of systems reported detections, and another 6 states reported detections in 90 to
95% of systems. Thirty-eight states reported detections greater than the MCL concentration of 4
mg/L, although only 5 of the 38 states reported that more than 2% of their systems exceeded 4
mg/L.
3 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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Exhibit 28-3: Percentage of Systems with at Least One Fluoride Detection,
by State
States Not Submitting Any Data
States with No Detections
Less than 90% of Systems Detecting
Between 90% and 95% of Systems Detecting
More than 95% of Systems Detecting
Exhibit 28-4: Percentage of Systems with at Least One Fluoride Detection Greater
than the MCL Concentration (> 4 mg/L), by State
:%% States Not Submitting Any Data
States with No Detections > MCL
Less than 1% of Systems with Detections > MCL
^H Between 1% and 2% of Systems with Detections > MCL
^B More than 2% of Systems with Detections > MCL
Exhibit 28-5 presents the Stage 1 analysis of fluoride occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 2 mg/L and 4 mg/L. About 2,400 (5.029% of) systems, serving about 11.5
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million persons, reported at least one detection greater than or equal to 2 mg/L; and 519 (1.068%
of) systems, serving 2.8 million persons, reported at least one detection exceeding 4 mg/L.
Exhibit 28-5: Fluoride Stage 1 Analysis -
Systems and Populations with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 4 mg/L
> 2 mg/L
Number of
Systems
Exceeding
Threshold
493
2,298
Percent of
Systems
Exceeding
Threshold
1.106%
5.155%
Total Population-
Served by
Systems
Exceeding
Threshold
1,341,331
6,344,789
Percent of
Population -Served
by Systems
Exceeding
Threshold
1.560%
7.378%
Surface
Water
> 4 mg/L
> 2 mg/L
26
146
0.646%
3.629%
1,481,883
5,108,236
1.004%
3.462%
Combined
Ground &
Surface
Water
> 4 mg/L
> 2 mg/L
519
2,444
1.068%
5.029%
2,823,214
11,453,025
1.209%
4.903%
28.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2003. Toxicological Profile for
Fluorides, Hydrogen Fluoride, and Fluorine. September 2003. Available on the Internet at:
http://www.atsdr.cdc.gov/toxprofiles/tpl 1 .html.
Gilliom, R.J., I.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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
United States Environmental Protection Agency (USEPA). 1986. National Primary and
Secondary Drinking Water Regulations; Fluoride; Final Rule. Federal Register. Vol. 51, No. 63.
p. 11396, April 2, 1986.
USEPA. 2002. National Primary Drinking Water Regulations; Announcement of the Results of
EPA's Review of Existing Drinking Water Standards and Request for Public Comment;
Proposed Rule. Federal Register. Vol. 67, No. 74, p. 19030, April 17, 2002.
USEPA. 2008a. TRI Explorer: Trends - Hydrogen Fluoride. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for hydrogen
fluoride.] Accessed February 29, 2008.
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USEPA. 2008b. TRI Explorer: Trends - Fluorine. Released February 21, 2008. Available on the
Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for fluorine.] Accessed February
29, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
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29 Glyphosate
This chapter on glyphosate is part of a report that is organized so that each chapter
presents information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and glyphosate
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
29.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for glyphosate on July 17, 1992 (57 FR
31776 (USEPA, 1992)). The NPDWR established a maximum contaminant level goal (MCLG)
and a maximum contaminant level (MCL) of 700 |ig/L. The Agency developed the MCLG based
on a reference dose (RfD) of 100 jig/kg-day (0.1 mg/kg-day) and a cancer classification of D, not
classifiable as to human carcinogenicity.
According to the Extension Toxicology Network (EXTOXNET, 1996), glyphosate
(CsHgNOsP) is an organic solid of colorless crystals. Glyphosate itself is an acid, but it is
commonly used in salt form. It is generally distributed as water-soluble concentrates and
powders. Glyphosate binds strongly to most soils and does not leach easily. It breaks down
primarily by the action of microbes. The time required to degrade varies greatly; field studies
have reported half lives in soil of 1 to 174 days (EXTOXNET, 1996).
29.2 Use, Production, and Releases
Glyphosate is a non-selective herbicide used on many food and non-food crops as well as
non-crop areas such as roadsides. The most common uses include control of annual and perennial
plants including grasses, sedges, broad-leaved weeds, and woody plants (EXTOXNET, 1996).
Exhibit 29-1, compiled by the United States Geological Survey (USGS, 2007), shows the
geographic distribution of estimated average annual glyphosate use in the United States from
1999 through 2004. A breakdown of use by crop is also included. The map was created by the
USGS using state-level data sets on pesticide use rates from 1999-2004 compiled by the
CropLife Foundation, at the Crop Protection Research Institute, combined with county-level data
on harvested crop acreage obtained from the 2002 Census of Agriculture. Due to the nature of the
data sources, non-agricultural uses are not reflected here, and variations in use at the county-level
are also not well represented (Thelin and Gianessi, 2000). The USGS (2007) estimates that
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approximately 102 million pounds of glyphosate active ingredient were used on average each
year between 1999 and 2004. The greatest use of glyphosate is in the Midwest.
Exhibit 29-1: Estimated Annual Agricultural Use for Glyphosate (c. 2002)
GLYPHOSATE - herbicide
2002 estimated annual agricultural use
Average annual use of
active ingredient
(pounds per square mile of agricultural
land in county)
D no estimated use
D 0.001 to 0.499
D 0.5 to 3.445
D 3.446 to 14.669
D 14.67 to 47.984
• >= 47.985
Total
Cr°Ps pounds applied
soybeans
corn
cotton
wheat for grain
cropland in summer fallow
citrus fruit
sorghum
rice
almonds
grapes
70699653
7491973
7063492
35091 51
2514196
2186741
1596879
1057534
867188
711121
Percent
national use
69.49
7.36
6.94
3.45
2.47
2.15
1.57
1.04
0.85
0.70
Source: USGS, 2007
The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for glyphosate.
Glyphosate is not listed as a Toxics Release Inventory (TRI) chemical; thus, no TRI
release records are available.
29.3 Occurrence in Ambient Water
No National Water Quality Assessment (NAWQA) Program data are available from the
USGS on the occurrence of glyphosate in ambient waters from the Pesticide National Synthesis
Project (Gilliom et a/., 2007) or the EPA Summary Analysis of Cycle 1 data.
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29.4 Occurrence in Drinking Water
Glyphosate is regulated as a synthetic organic chemical (SOC) in drinking water. All non-
purchased community water systems (CWSs) and non-transient non-community water systems
(NTNCWSs) are required to sample for SOCs. The maximum waiver period for SOCs is three
years, but this waiver can be renewed indefinitely. (Systems may receive a waiver at any time
without having collected an SOC sample. With a waiver, systems are not required to collect an
SOC sample.) Statewide waivers are often granted for glyphosate.
All CWSs and NTNCWSs without an SOC waiver must collect four consecutive
quarterly samples during the initial three-year compliance period.l If all four samples are non-
detections, then a system serving less than 3,300 persons may reduce to one sample during each
consecutive compliance period; a system serving more than 3,300 persons may reduce to two
quarterly samples within a 12-month period during a 3-year compliance period. If a chemical is
detected (but is less than the MCL), the system must take one sample per quarter until results are
below the MCL (minimum of two quarterly samples for ground water systems and four quarterly
samples for surface water systems). If all quarterly samples are below the MCL, the system may
return to annual sampling. If a chemical is detected at a level greater than the MCL, the system
(whether ground water or surface water) must take quarterly samples until four consecutive
quarters are below the MCL. If all quarterly samples are below the MCL, the system may return
to annual sampling.
The analysis of glyphosate occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
Glyphosate data were provided by 42 of the Six-Year Review-ICR states. (No glyphosate
data were received from Missouri, North Carolina, or Texas.) The glyphosate data from the 42
states consist of 58,174 analytical results from 16,351 public water systems (PWSs) during the
period from 1998 to 2005. The number of sample results and systems vary by state, although the
state data sets have been reviewed and checked to ensure adequacy of coverage and
completeness.
29.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 29-2
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For glyphosate, 0.177% of 16,351 systems reported
detections. Exhibit 29-3 lists the minimum, median, 90th percentile, and maximum glyphosate
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of glyphosate, based on detections from all systems, is 10 |ig/L.
Exhibit 29-2: Glyphosate Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
46,591
14,974
46,311,603
Surface Water
11,583
1,377
69,964,408
Combined Ground &
Surface Water
58,174
16,351
116,276,011
Percent with Detections
Ground Water
0.064%
0.140%
6.074%
Surface Water
0.095%
0.581%
1.043%
Combined Ground &
Surface Water
0.070%
0.177%
3.047%
Exhibit 29-3: Glyphosate Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
5.5
Median
10
90tn
Percentile
97.5
Maximum
700
Surface Water
2.6
10
66
500
Combined Ground &
Surface Water
2.6
10
95
700
Exhibit 29-4 illustrates the geographic distribution of glyphosate occurrence in drinking
water, identifying the states with systems with at least one detection. (No systems reported
detections greater than the MCL concentration; thus, no map is included for MCL concentration
exceedances.) Note that five states did not submit data for use in the Six-Year Review (Kansas2,
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas data included
in the analyses.
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Louisiana, Mississippi, Pennsylvania, and Washington). Missouri, North Carolina, and Texas
submitted Six-Year data for most contaminants, but did not submit data for glyphosate.
Detection rates were generally low for glyphosate; only 2 states reported detections in
more than 1% of their systems. In two states, between 0.5% and 1% of systems reported
detections. Thirty-three states reported no detections of glyphosate. Furthermore, no states
reported detections greater than the MCL concentration of 700 |ig/L.
Exhibit 29-4: Percentage of Systems with at Least One Glyphosate Detection,
by State
////\ States with Waivers or Not Submitting
States with No Detections
Less than 0.5% of Systems Detecting
^B Between 0.5% and 1% of Systems Detecting
^H More than 1% of Systems Detecting
Exhibit 29-5 presents the Stage 1 analysis of glyphosate occurrence in drinking water
from systems and population-served by those systems in the Six-Year Review-ICR Dataset
relative to two thresholds: 350 |ig/L and 700 |ig/L. Two (0.012% of) systems, serving almost
49,000 persons, reported at least one detection greater than or equal to 350 |ig/L. No systems
reported detections greater than 700 |ig/L.
Exhibit 29-5: Glyphosate Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 700 |jg/L
Number of
Systems
Exceeding
Threshold
0
Percent of
Systems
Exceeding
Threshold
0.000%
Total Population-
Served by
Systems
Exceeding
Threshold
0
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.000%
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Source
Water
Type
Threshold
> 350 |jg/L
Number of
Systems
Exceeding
Threshold
1
Percent of
Systems
Exceeding
Threshold
0.007%
Total Population-
Served by
Systems
Exceeding
Threshold
40
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.000%
Surface
Water
> 700 |jg/L
> 350 |jg/L
0
1
0.000%
0.073%
0
48,800
0.000%
0.070%
Combined
Ground &
Surface
Water
> 700 |jg/L
> 350 |jg/L
0
2
0.000%
0.012%
0
48,840
0.000%
0.042%
29.5 References
Extension Toxicology Network (EXTOXNET). 1996. EXTOXNET Pesticide Information
Profiles-Glyphosate. Last modified June 1996. Available on the Internet at:
http://extoxnet.orst.edu/pips/glyphosa.htm. Accessed March 6, 2008.
Gilliom, R.J., I.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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
Thelin, G.P. and L.P. Gianessi. 2000. Method for Estimating Pesticide Use for County Areas of
the Conterminous United States. U.S. Geological Survey Open-File Report 00-250, 62 p.
Available on the Internet at: http://ca.water.usgs.gov/pnsp/rep/ofr00250/ofr00250.pdf.
United States Environmental Protection Agency (USEPA). 1992. Drinking Water; National
Primary Drinking Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals;
National Primary Drinking Water Regulations Implementation; Final Rule. Federal Register.
Vol. 57, No. 138. p. 31776, July 17, 1992.
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. Office of Water. EPA-815-B-09-006. October 2009.
United States Geological Survey (USGS). 2007. 2002 Pesticide Use Maps. Available on the
Internet at:
http://water.usgs.gov/nawqa/pnsp/usage/maps/show map.php?vear=02&map=ml099. Accessed
March 6, 2008.
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30 Lindane (Gamma-Hexachlorocyclohexane)
This chapter on lindane (gamma-hexachlorocyclohexane) is part of a report that is
organized so that each chapter presents information on one specific contaminant. Chapter 1 of
this report, Introduction, presents background information on all sources of data used as well as
the analytical approach used to estimate contaminant occurrence in drinking water. This
contaminant chapter includes background information (such as regulatory history, general
chemical information, and environmental fate and behavior), use and environmental release
information, and lindane occurrence estimates in ambient water and drinking water. All drinking
water occurrence estimates were based on data from the National Compliance Monitoring
Information Collection Request (ICR) Dataset for the Second Six-Year Review (the "Six Year
Review-ICRDataset"). For detailed information regarding this dataset, data management, data
quality assessments, and the analytical approach used to generate all contaminant occurrence
estimates presented in this chapter, please refer to USEPA (2009).
30.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for lindane on January 30, 1991 (56
FR 3526 (USEPA, 1991)). The NPDWR established a maximum contaminant level goal
(MCLG) and a maximum contaminant level (MCL) of 0.2 |ig/L. The Agency based the MCLG
on a reference dose (RfD) of 0.3 jig/kg-day (0.0003 mg/kg-day) and a cancer classification of C,
possible human carcinogen.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2005),
lindane (CeHeCle) is one of eight isomers of the manufactured chemical hexachlorocyclohexane
(HCH). Lindane is a white solid that may evaporate into the air as a colorless vapor with a
slightly musty odor. In the air, the different forms of HCH can exist as a vapor or attached to
small particles such as soil and dust. The particles may be removed from the air by rain or
degraded by other compounds in the atmosphere. In soil, sediments, and water, HCH is broken
down to less toxic substances by algae, fungi, and bacteria, but this process can take a long time.
Other names for lindane include gamma-hexachlorocyclohexane, gamma-HCH, and y-HCH
(ATSDR, 2005).
30.2 Use, Production, and Releases
Lindane has not been produced in the United States since 1976, but is imported for
insecticide use (ATSDR, 2005). Between 1998 and 1999, lindane registrants voluntarily
cancelled all registered uses of lindane, except for seed treatment uses on 19 agricultural crops
and a dog mange treatment. Use for dog mange was voluntarily cancelled in 2001. In 2001 and
2002 registrants voluntarily cancelled all but six lindane seed treatment uses. In 2006, EPA
called for the voluntary cancellation of all agricultural uses of lindane (USEPA, 2006).
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
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years. Exhibit 30-1 presents the production of lindane in the United States from 1986 to 2002.
Note that the production of lindane in the United States was only documented in the Chemical
Update System in 1986 and 1998 and was the same for both those years.
Exhibit 30-1: Production of Lindane in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
10,000 - 500,000 pounds
No reports
No reports
10,000 - 500,000 pounds
No reports
Source: USEPA, 2003
Lindane is listed as a Toxics Release Inventory (TRI) chemical. TRI data indicate that
total off-site and on-site releases of lindane for the period 1998-2006 ranged from 10 pounds to
approximately 26,000 pounds, with a decrease over time (USEPA, 2008).
30.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of lindane in
ambient water are available from the NAWQA program.
30.3.1 NA WQA Pesticide National Synthesis Project
The NAWQA Pesticide National Synthesis Project is a national-scale assessment of the
occurrence and behavior of pesticides in streams and ground water of the United States and the
potential for pesticides to adversely affect drinking water supplies or aquatic ecosystems. Under
the National Synthesis Project, the USGS monitored lindane (gamma-HCH) between 1992 and
2001 in streams and wells across the country (Gilliom et a/., 2007). The maximum long-term
method detection limit for lindane was 0.002 |ig/L.
In NAWQA stream samples (Exhibit 30-2), lindane was found at frequencies ranging
from 0.48% of samples in undeveloped areas to 1.02% in agricultural settings, 1.91% in mixed
land use settings, and 3.11% of samples in urban areas. The 95th percentile concentration was
less than the method detection limit in all land use settings. The highest concentration, 0.130
Hg/L, was found in an undeveloped setting.
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Exhibit 30-2: USGS National Synthesis Summary of NAWQA Monitoring of
Lindane in Streams, 1992-2001
Land Use
Type
Agricultural
Mixed
Undeveloped
Urban
No. of Samples
(No. of Sites)
2,001 (83)
1,355(65)
144(8)
803 (30)
Detection
Frequency
1.02%
1.91%
0.48%
3.11%
50tn Percent! le
(Median)
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
95th Percentile
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
Maximum
Concentration
(in ug/L)
0.053
0.043
0.130
0.048
Source: Gilliom et a/., 2007
1. ND = not detected (Concentration is less than the maximum long term method detection limit and is expected to be
less than any higher percentile concentration shown in the table)
In ground water NAWQA samples (Exhibit 30-3), lindane was only detected in mixed
land use settings (at a frequency of 0.07%). The highest concentration at a mixed land use setting
was0.152|ig/L.
Exhibit 30-3: USGS National Synthesis Summary of NAWQA Monitoring of
Lindane in Ground Water, 1992-2001
Land Use Type
Agricultural
Mixed
Undeveloped
Urban
Number
of Wei Is
1,397
2,728
33
843
Detection
Frequency
0.00%
0.07%
0.00%
0.00%
50tn Percentile
(Median)
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
95th Percentile
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
Maximum
Concentration
(in ug/L)
ND1
0.152
ND1
ND1
Source: Gilliom et a/., 2007
1. ND = not detected (Concentration is less than the maximum long term method detection limit and is expected to be
less than any higher percentile concentration shown in the table)
30.3.2 EPA Summary Analysis of NAWQA Data
Whereas the NAWQA program often uses the most representative data for a site to
calculate summary statistics, EPA, with the cooperation of the USGS, has performed a summary
analysis of all Cycle 1 water monitoring data from all study units (1992-2001) for lindane.
Detection frequencies were computed as the percentage of samples and sites with detections (i.e.,
with at least one result equal to or greater than the reporting limit). Sample detections can be
biased by frequent sampling in areas with high (or low) occurrence. Calculating the percentage
of sites with detections can reduce this bias.
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The results of the EPA analysis are presented in Exhibit 30-4. Overall, lindane was
detected in 1.7% of samples and at 1.5% of sites. Lindane was detected more frequently in
surface water than in ground water. The median concentration based on detections from all sites
was 0.0102 |ig/L. The 99th percentile concentration based on detections from all sites was 0.11
Exhibit 30-4: EPA Summary Analysis of Lindane Data from NAWQA Study Units,
1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
6,060
14,870
20,930
% Samples
with
Detections
0.0%
2.3%
1.7%
Number
of Sites
5,193
1,907
7,100
% Sites
with
Detections
0.0%
5.7%
1.5%
Concentration Values
(of detections, in ug/L)
Minimum
0.009
0.0009
0.0009
Median
0.0109
0.0102
0.0102
95th
Percen-
tile
0.0128
0.075
0.075
99th
Percen-
tile
0.0128
0.11
0.11
Maximum
0.0128
0.219
0.219
1. RLs (Reporting Umits) for lindane varied, but did not exceed 0.004 pg/L. Note that because this EPA analysis
involves more data points than the USGS analyses presented above, a direct comparison is not possible.
30.4 Occurrence in Drinking Water
Lindane is regulated as a synthetic organic chemical (SOC) in drinking water. All non-
purchased community water systems (CWSs) and non-transient non-community water systems
(NTNCWSs) are required to sample for SOCs. The maximum waiver period for SOCs is three
years, but this waiver can be renewed indefinitely. (Systems may receive a waiver at any time
without having collected an SOC sample. With a waiver, systems are not required to collect an
SOC sample.)
All CWSs and NTNCWSs without an SOC waiver must collect four consecutive
quarterly samples during the initial three-year compliance period.l If all four samples are non-
detections, then a system serving less than 3,300 persons may reduce to one sample during each
consecutive compliance period; a system serving more than 3,300 persons may reduce to two
quarterly samples within a 12-month period during a 3-year compliance period. If a chemical is
detected (but is less than the MCL), the system must take one sample per quarter until results are
below the MCL (minimum of two quarterly samples for ground water systems and four quarterly
samples for surface water systems). If all quarterly samples are below the MCL, the system may
return to annual sampling. If a chemical is detected at a level greater than the MCL, the system
(whether ground water or surface water) must take quarterly samples until four consecutive
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the
MCL.
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quarters are below the MCL. If all quarterly samples are below the MCL, the system may return
to annual sampling.
The analysis of lindane occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
Forty-four of the Six-Year Review-ICR states provided occurrence data for lindane.
(There were no lindane data from Oklahoma.) These data consist of 135,585 analytical results
from more than 33,265 public water systems (PWSs) during the period from 1998 to 2005. The
number of sample results and systems vary by state, although the state data sets have been
reviewed and checked to ensure adequacy of coverage and completeness.
30.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 30-5
presents the number of samples and systems, as well as the population-served by the systems,
and the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For lindane, 0.253% of 33,265 systems reported
detections. Exhibit 30-6 lists the minimum, median, 90th percentile, and maximum lindane
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of lindane, based on detections from all systems, is 0.04 |ig/L.
Exhibit 30-5: Lindane Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
106,917
30,143
68,277,043
Surface Water
28,668
3,122
118,981,892
Combined Ground &
Surface Water
135,585
33,265
187,258,935
Percent with Detections
Ground Water
0.109%
0.219%
4.169%
Surface Water
0.105%
0.577%
3.978%
Combined Ground &
Surface Water
0.108%
0.253%
4.048%
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Exhibit 30-6: Lindane Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.002
Median
0.04
90tn
Percent! le
0.11
Maximum
0.69
Surface Water
0.001
0.03
0.2
0.5
Combined Ground &
Surface Water
0.001
0.04
0.11
0.69
The following maps illustrate the geographic distribution of lindane occurrence in
drinking water. Exhibit 30-7 shows the states with systems with at least one detection and
Exhibit 30-8 shows the states with systems with at least one detection greater than the MCL
concentration. Note that five states did not submit data for use in the Six-Year Review (Kansas2,
Louisiana, Mississippi, Pennsylvania, and Washington). Oklahoma submitted Six-Year data for
most contaminants; however, there is a statewide waiver for lindane in Oklahoma so no lindane
data were available from that state.
Detection rates were generally low; only six states reported detections in more than 1%
of their systems. These states are all located in the eastern half of the United States. In three
states, between 0.5% and 1% of systems reported detections. Two states reported detections
greater than the MCL concentration of 0.2 |ig/L.
Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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Exhibit 30-7: Percentage of Systems with at Least One Lindane Detection,
by State
States with Waivers or Not Submitting
States with No Detections
Less than 0.5% of Systems Detecting
Between 0.5% and 1% of Systems Detecting
j More than 1% of Systems Detecting
Exhibit 30-8: Percentage of Systems with at Least One Lindane Detection Greater
than the MCL Concentration (> 0.2 pg/L), by State
\)
States with Waivers or Not Submitting
H States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
Between 0.1% and 0.5% of Systems with Detections > MCL
More than 0.5% of Systems with Detections > MCL
Exhibit 30-9 presents the Stage 1 analysis of lindane occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 0.1 |ig/L and 0.2 |ig/L. Fifteen (0.045% of) systems, serving almost 550,000
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persons, reported at least one detection greater than or equal to 0.1 |ig/L; and 3 (0.009% of)
systems, serving more than 4,800 persons, reported at least one detection greater than 0.2 |ig/L.
Exhibit 30-9: Lindane Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 0.2 |jg/L
>0.1 |jg/L
Number of
Systems
Exceeding
Threshold
2
11
Percent of
Systems
Exceeding
Threshold
0.007%
0.036%
Total Population-
Served by
Systems
Exceeding
Threshold
462
36,143
Percent of
Population-Served
by Systems
Exceeding
Threshold
0.001%
0.053%
Surface
Water
> 0.2 |jg/L
>0.1 |jg/L
1
4
0.032%
0.128%
4,374
512,063
0.004%
0.430%
Combined
Ground &
Surface
Water
> 0.2 |jg/L
>0.1 |jg/L
3
15
0.009%
0.045%
4,836
548,206
0.003%
0.293%
30.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2005. ToxFAQsfor
Hexachlorocyclohexane. August 2005. Available on the Internet at:
http ://www. atsdr. cdc. gov/tfacts43 .html.
Gilliom, R.J., I.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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circl291/appendix7/.
United States Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - Lindane. Last modified September 10, 2007. Available on the Internet at:
http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for lindane.] Accessed February
21,2008.
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USEPA. 2006. Addendum to the 2002 Lindane Reregi strati on Eligibility Decision (RED). July
2006. Available on the Internet at:
http://www.epa.gov/oppsrrd 1/REDs/lindane red addendum.pdf
USEPA. 2008. TRI Explorer: Trends - Lindane. Released February 21, 2008. Available on the
Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for lindane.] Accessed March 6,
2008.
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!. Office of Water. EPA-815-B-09-006. October 2009.
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31 Mercury (Inorganic)
This chapter on mercury (inorganic) is part of a report that is organized so that each
chapter presents information on one specific contaminant. Chapter 1 of this report, Introduction,
presents background information on all sources of data used as well as the analytical approach
used to estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and mercury
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
31.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for inorganic mercury on January 30,
1991 (56 FR 3526 (USEPA, 1991)). The NPDWR established a maximum contaminant level
goal (MCLG) and a maximum contaminant level (MCL) of 0.002 mg/L. The Agency based the
MCLG on a Drinking Water Equivalent Level (DWEL) of 0.01 mg/L1 and a cancer classification
of D, not classifiable as to human carcinogenicity.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 1999),
mercury is a metal that has several forms. Metallic mercury is a shiny, silver-white, odorless
liquid; it is very rare in nature. Mercury in nature is generally combined with sulfur in the ore
mineral cinnabar. It also is emitted into the atmosphere from volcanoes and from the incineration
of coal (USGS, 2000). It can be combined with other elements, such as chlorine or oxygen, to
form inorganic mercury compounds. These are usually white powders or crystals. Mercury also
combines with carbon to make organic mercury compounds. The most common organic
compound, methylmercury, is produced mainly by microscopic organisms in the water and soil.
Increased mercury in the environment can increase the production of methylmercury (ATSDR,
1999), which is the most toxic form (USGS, 2000).
31.2 Use, Production, and Releases
Metallic mercury is used to produce chlorine gas and caustic soda. It can also be used in
thermometers, dental fillings, and batteries. Mercury is used to produce chlorine gas and caustic
soda, and is also used in thermometers, dental fillings, and batteries. Mercury salts are sometimes
used in skin lightening creams and as antiseptic creams and ointments (ATSDR, 1999).
1 The DWEL was recommended by a panel of experts on mercury, and was derived using the weight of evidence
from the entire inorganic mercury database. The DWEL was later back-calculated to a reference dose (RfD) of
0.0003 mg/kg-day (USEPA, 1995).
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The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 31-1 presents the production of mercury in the United States from 1986 to 2002.
Note that the production of mercury in the United States was only documented in the Chemical
Update System in 1986 and 1990 and remained constant in those years.
Exhibit 31-1: Production of Mercury in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
10,000 - 500,000 pounds
10,000 - 500,000 pounds
No reports
No reports
No reports
Source: USEPA, 2003
Mercury and mercury compounds are listed as Toxics Release Inventory (TRI) chemicals.
TRI data indicate that total off-site and on-site releases of mercury for the period 1998-2006
ranged from about 72,000 pounds to approximately 291,000 pounds, with a general increase over
time. In most years, off-site releases were greater than on-site releases (USEPA, 2008a). Total
mercury compound releases ranged from approximately 3.1 million pounds to approximately 9.1
million pounds, with a decrease until 1999. After 1999, total amounts released leveled off.
Amounts released on-site were greater than amounts released off-site (USEPA, 2008b).
31.3 Occurrence in Ambient Water
No National Water Quality Assessment (NAWQA) Program data are available from the
United States Geological Survey (USGS) on the occurrence of mercury in ambient waters from
the Pesticide National Synthesis Project (Gilliom et a/., 2007) or the EPA Summary Analysis of
Cycle 1 data.
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31.4 Occurrence in Drinking Water
Mercury is regulated as an inorganic chemical (IOC) in drinking water. All community
water systems (CWSs) and non-transient non-community water systems (NTNCWSs) are
required to sample for the IOCs.2 The maximum waiver period for lOCs is nine years.
Ground water systems must sample once during the initial three-year compliance period.
After three compliance periods without a detection, a ground water system may be granted a
nine-year waiver. Surface water systems must sample annually during the initial three-year
compliance period. After three annual samples without a detection, a surface water system may
be granted a nine-year waiver. If the results are greater than the MCL, the public water system
(PWS) must take one sample per quarter until results are below the MCL (minimum of two
quarterly samples for ground water systems and four quarterly samples for surface water
systems).3 If all quarterly samples are below the MCL, the system may continue at initial
monitoring indefinitely until the state or EPA establishes an alternate schedule.
The analysis of mercury occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
All of the Six-Year Review-ICR states provided occurrence data for mercury. These data
consist of 181,629 analytical results from 48,859 systems during the period from 1998 to 2005.
The number of sample results and systems vary by state, although the state data sets have been
reviewed and checked to ensure adequacy of coverage and completeness.
31.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 31-2
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For mercury, 3.964% of 48,859 systems reported
detections. Exhibit 31-3 lists the minimum, median, 90th percentile, and maximum mercury
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of mercury, based on detections from all systems, is 0.0002 mg/L.
2 Nitrate and nitrite have their own monitoring requirements. See the nitrate and nitrite chapters for details of those
requirements.
3 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
31-3
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Exhibit 31-2: Mercury Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
141,104
44,863
85,514,854
Surface Water
40,525
3,996
144,338,525
Combined Ground &
Surface Water
181,629
48,859
229,853,379
Percent with Detections
Ground Water
1.894%
3.669%
17.131%
Surface Water
1 .426%
7.282%
21.783%
Combined Ground &
Surface Water
1.789%
3.964%
20.052%
Exhibit 31-3: Mercury Summary Statistics
Source Water Type
Ground Water
Detection Value (mg/L)
Minimum
0.000021
Median
0.0002
90tn
Percentile
0.001
Maximum
0.06
Surface Water
0.000022
0.0002
0.001
0.1
Combined Ground &
Surface Water
0.000021
0.0002
0.001
0.1
The following maps illustrate the geographic distribution of mercury occurrence in
drinking water. Exhibit 31-4 shows the states with systems with at least one detection and
Exhibit 31-5 shows the states with systems with at least one detection greater than the MCL
concentration. Note that five states did not submit data for use in the Six-Year Review (Kansas4,
Louisiana, Mississippi, Pennsylvania, and Washington).
The distribution of systems with mercury detections is geographically dispersed. In 12
states, more than 5% of systems detected mercury. In five states, more than 0.5% of systems
4 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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reported at least one detection greater than the MCL concentration of 0.002 mg/L. Twenty states
reported no detections of mercury greater than 0.002 mg/L.
Exhibit 31-4: Percentage of Systems with at Least One Mercury Detection,
by State
States Not Submitting Any Data
States with No Detections
~ Less than or Equal to 1% of Systems Detecting
B Between 1% and 5% of Systems Detecting
More than 5% of Systems Detecting
Exhibit 31-5: Percentage of Systems with at Least One Mercury Detection Greater
than the MCL Concentration (> 0.002 mg/L), by State
j. "™-'4^ft,.
States Not Submitting Any Data
States with No Detections > MCL
I Less than 0.1% of Systems with Detections > MCL
Between 0.1% and 0.5% of Systems with Detections > MCL
| More than 0.5% of Systems with Detections > MCL
31-5
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Exhibit 31-6 presents the Stage 1 analysis of mercury occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 0.001 mg/L and 0.002 mg/L. A total of 274 (0.561% of) systems, serving more
than 12.8 million persons, reported at least one detection greater than or equal to 0.001 mg/L; and
82 (0.168% of) systems, serving almost 2.6 million persons, reported at least one detection
greater than 0.002 mg/L.
Exhibit 31-6: Mercury Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 0.002 mg/L
> 0.001 mg/L
Number of
Systems
Exceeding
Threshold
64
223
Percent of
Systems
Exceeding
Threshold
0.143%
0.497%
Total Population-
Served by
Systems
Exceeding
Threshold
617,666
2,282,255
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.722%
2.669%
Surface
Water
> 0.002 mg/L
> 0.001 mg/L
18
51
0.450%
1 .276%
1,973,654
10,552,870
1.367%
7.311%
Combined
Ground &
Surface
Water
> 0.002 mg/L
> 0.001 mg/L
82
274
0.168%
0.561%
2,591,320
12,835,125
1.127%
5.584%
31.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 1999. ToxFAQs for Mercury.
April 1999. Available on the Internet at: http://www.atsdr.cdc.gov/tfacts46.html.
Gilliom, R.J., I.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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
United States Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
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USEPA. 1995. Integrated Risk Information System (IRIS), Mercuric Chloride. File First On-line
May 1, 1995. Available on the Internet at: http://www.epa.gov/iris/subst/0692.htm. Accessed
March 10, 2008.
USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - Mercury. Last modified September 10, 2007. Available on the Internet at:
http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for mercury.] Accessed February
21,2008.
USEPA. 2008a. TRI Explorer: Trends - Mercury. Released February 21, 2008. Available on the
Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for mercury.] Accessed March 6,
2008.
USEPA. 2008b. TRI Explorer: Trends - Mercury Compounds. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for mercury
compounds.] Accessed March 6, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
United States Geological Survey (USGS). 2000. Mercury in the Environment, Fact Sheet 146-00
(October 2000). Available on the Internet at: http://www.usgs.gov/themes/factsheet/146-00 .
Accessed March 15, 2008.
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32 Methoxychlor
This chapter on methoxychlor is part of a report that is organized so that each chapter
presents information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and methoxychlor
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
32.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for methoxychlor on January 30, 1991
(56 FR 3526 (USEPA, 1991)). The NPDWR established a maximum contaminant level goal
(MCLG) and a maximum contaminant level (MCL) of 40 |ig/L. The Agency based the MCLG on
a reference dose (RfD) of 5 jig/kg-day (0.005 mg/kg-day) and a cancer classification of D, not
classifiable as to human carcinogenicity.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2002),
methoxychlor (CieHisdsC^) is a manufactured chemical that does not occur naturally in the
environment. Pure methoxychlor is a pale-yellow powder with a slight fruity or musty odor. This
chemical does not dissolve easily in water and binds strongly to particles. It may take months to
break down. It does not generally accumulate in the food chain. Other names for methoxychlor
include DMDT, Marlate®, or Metox® (ATSDR, 2002).
32.2 Use, Production, and Releases
Methoxychlor is used as an insecticide against flies, mosquitoes, cockroaches, chiggers,
and a wide variety of other insects. Methoxychlor is also used on agricultural crops and livestock,
and in animal feed, barns, grain storage bins, home garden, and on pets. It is preferred to
dichlorodiphenyltrichloroethane (DDT) for use on animals, in animal feed, and on DDT-sensitive
crops such as squash, melons, etc. because it is more unstable than DDT and has less residual
effect (ATSDR, 2002).
The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for methoxychlor.
32-1
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Methoxychlor is listed as a Toxics Release Inventory (TRI) chemical. TRI data indicate
that total off-site and on-site releases of methoxychlor for the period 1998-2006 ranged from 43
pounds to approximately 25,000 pounds, with the maximum releases occurring in 1998. On-site
releases were greater than off-site releases (USEPA, 2008).
32.3 Occurrence in Ambient Water
No National Water Quality Assessment (NAWQA) Program data are available from the
United States Geological Survey (USGS) on the occurrence of methoxychlor in ambient waters
from the Pesticide National Synthesis Project (Gilliom et a/., 2007) or the EPA Summary
Analysis of Cycle 1 data.
32.4 Occurrence in Drinking Water
Methoxychlor is regulated as a synthetic organic chemical (SOC) in drinking water. All
non-purchased community water systems (CWSs) and non-transient non-community water
systems (NTNCWSs) are required to sample for SOCs. The maximum waiver period for SOCs is
three years, but this waiver can be renewed indefinitely. (Systems may receive a waiver at any
time without having collected an SOC sample. With a waiver, systems are not required to collect
an SOC sample.)
All CWSs and NTNCWSs without an SOC waiver must collect four consecutive
quarterly samples during the initial three-year compliance period.l If all four samples are non-
detections, then a system serving less than 3,300 persons may reduce to one sample during each
consecutive compliance period; a system serving more than 3,300 persons may reduce to two
quarterly samples within a 12-month period during a 3-year compliance period. If a chemical is
detected (but is less than the MCL), the system must take one sample per quarter until results are
below the MCL (minimum of two quarterly samples for ground water systems and four quarterly
samples for surface water systems). If all quarterly samples are below the MCL, the system may
return to annual sampling. If a chemical is detected at a level greater than the MCL, the system
(whether ground water or surface water) must take quarterly samples until four consecutive
quarters are below the MCL. If all quarterly samples are below the MCL, the system may return
to annual sampling.
The analysis of methoxychlor occurrence presented in the following section is based on
state compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and
most comprehensive compliance monitoring data set compiled by EPA's Drinking Water
Program to date.
Forty-four of the Six-Year Review-ICR states provided occurrence data for
methoxychlor. (There were no methoxychlor data from Oklahoma.) These data consist of
137,068 analytical results from 33,421 public water systems (PWSs) during the period from 1998
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
32-2
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
to 2005. The number of sample results and systems vary by state, although the state data sets
have been reviewed and checked to ensure adequacy of coverage and completeness.
32.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 32-1
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For methoxychlor, 0.159% of 33,421 systems reported
detections. Exhibit 32-2 lists the minimum, median, 90th percentile, and maximum methoxychlor
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of methoxychlor, based on detections from all systems, is 0.1 |ig/L.
Exhibit 32-1: Methoxychlor Occurrence Data from the
Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
108,078
30,291
68,501,754
Surface Water
28,990
3,130
119,134,365
Combined Ground &
Surface Water
137,068
33,421
187,636,119
Percent with Detections
Ground Water
0.031%
0.089%
3.912%
Surface Water
0.128%
0.831%
2.406%
Combined Ground &
Surface Water
0.052%
0.159%
2.956%
Exhibit 32-2: Methoxychlor Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.009
Median
0.04
90tn
Percentile
0.62
Maximum
0.8
Surface Water
0.0073
0.2
0.6
1.1
32-3
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source Water Type
Detection Value (ug/L)
Minimum
Median
90tn
Percentile
Maximum
Combined Ground &
Surface Water
0.0073
0.1
0.6
1.1
Exhibit 32-3 illustrates the geographic distribution of methoxychlor occurrence in
drinking water, identifying the states with systems with at least one detection. (No systems
reported detections greater than the MCL concentration; thus, no map is included for MCL
concentration exceedances.) Note that five states did not submit data for use in the Six-Year
Review (Kansas2, Louisiana, Mississippi, Pennsylvania, and Washington). Oklahoma submitted
Six-Year data for most contaminants; however, there is a statewide waiver for methoxychlor in
Oklahoma so no methoxychlor data were available from that state.
Detection rates were generally low for methoxychlor; only four states reported detections
in more than 1% of their systems. In five states, between 0.5% and 1% of systems reported
detections. Twenty-eight states reported no detections of methoxychlor. Furthermore, no states
reported detections greater than the MCL concentration of 40 |ig/L.
Exhibit 32-3: Percentage of Systems with at Least One Methoxychlor Detection,
by State
•;-y/^ States with Waivers or Not Submitting
States with No Detections
BLess than 0.5% of Systems Detecting
Between 0.5% and 1% of Systems Detecting
^H More than 1% of Systems Detecting
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
32-4
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 32-4 presents the Stage 1 analysis of methoxychlor occurrence in drinking water
from systems and population-served by those systems in the Six-Year Review-ICR Dataset
relative to two thresholds: 20 |ig/L and 40 |ig/L. No systems reported detections greater than
equal to either threshold.
or
Exhibit 32-4: Methoxychlor Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 40 |jg/L
> 20 |jg/L
Number of
Systems
Exceeding
Threshold
0
0
Percent of
Systems
Exceeding
Threshold
0.000%
0.000%
Total Population-
Served by
Systems
Exceeding
Threshold
0
0
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.000%
0.000%
Surface
Water
> 40 |jg/L
> 20 |jg/L
0
0
0.000%
0.000%
0
0
0.000%
0.000%
Combined
Ground &
Surface
Water
> 40 |jg/L
> 20 |jg/L
0
0
0.000%
0.000%
0
0
0.000%
0.000%
32.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2002. Toxicological Profile for
Methoxychlor. September 2002. Available on the Internet at:
http://www.atsdr.cdc.gov/toxprofiles/tp47.pdf
Gilliom, R.J., I.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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
United States Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
USEPA. 2008. TRI Explorer: Trends - Methoxychlor. Released February 21, 2008. Available on
the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for methoxychlor.] Accessed
March 6, 2008.
32-5
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
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. Office of Water. EPA-815-B-09-006. October 2009.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
33 Monochlorobenzene (Chlorobenzene)
This chapter on monochlorobenzene (chlorobenzene) is part of a report that is organized
so that each chapter presents information on one specific contaminant. Chapter 1 of this report,
Introduction, presents background information on all sources of data used as well as the
analytical approach used to estimate contaminant occurrence in drinking water. This contaminant
chapter includes background information (such as regulatory history, general chemical
information, and environmental fate and behavior), use and environmental release information,
and monochlorobenzene occurrence estimates in ambient water and drinking water. All drinking
water occurrence estimates were based on data from the National Compliance Monitoring
Information Collection Request (ICR) Dataset for the Second Six-Year Review (the "Six Year
Review-ICR Dataset"). For detailed information regarding this dataset, data management, data
quality assessments, and the analytical approach used to generate all contaminant occurrence
estimates presented in this chapter, please refer to USEPA (2009).
33.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for monochlorobenzene on January 30,
1991 (56 FR 3526 (USEPA, 1991)). The NPDWR established a maximum contaminant level
goal (MCLG) and a maximum contaminant level (MCL) of 100 |ig/L. The Agency based the
MCLG on a reference dose (RfD) of 20 jig/kg-day (0.02 mg/kg-day) and a cancer classification
of D, not classifiable as to human carcinogenicity.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 1999),
monochlorobenzene (CeHsCl) does not occur naturally in the environment. It is a colorless,
flammable liquid with an aromatic, almond-like odor. Monochlorobenzene does not bind to soils
and can leach into ground water. If released to water or land, it will either evaporate or rapidly
biodegrade. However, some may filter into the groundwater. It does not accumulate significantly
in the food chain (ATSDR, 1999). Monochlorobenzene is also known as chlorobenzene.
33.2 Use, Production, and Releases
The production of monochlorobenzene in the United States has declined by more than
60% from its peak in 1960. It was used in the past to make other chemicals, such as phenol and
dichlorodiphenyltrichloroethane (DDT). Now it is used as a solvent for some pesticide
formulations, to degrease automobile parts, and as a chemical intermediate to make several other
chemicals (ATSDR, 1999).
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 33-1 presents the production of monochlorobenzene in the United States from
1986 to 2002. Note that the production of monochlorobenzene in the United States remained
constant from 1986 to 1998 and decreased thereafter.
33-1
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 33-1: Production of Monochlorobenzene in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
> 100 million - 500 million pounds
> 100 million - 500 million pounds
> 100 million - 500 million pounds
> 100 million - 500 million pounds
> 50 million - 100 million pounds
Source: USEPA, 2003
Monochlorobenzene is listed as a Toxics Release Inventory (TRI) chemical. TRI data
indicate that total off-site and on-site releases of monochlorobenzene for the period 1998-2006
ranged from approximately 639,000 pounds to approximately 982,000 pounds, with a general
decrease over time. On-site releases were greater than off-site releases (USEPA, 2008).
33.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of
monochlorobenzene in ambient water are available from the NAWQA program.
33.3.1 EPA Summary Analysis of NAWQA Data
EPA, with the cooperation of the USGS, has performed a summary analysis of all Cycle 1
water monitoring data from all study units (1992-2001) for monochlorobenzene. Detection
frequencies were computed as the percentage of samples and sites with detections (i.e., with at
least one result equal to or greater than the reporting limit). Sample detections can be biased by
frequent sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 33-2. Overall,
monochlorobenzene was detected in 1.9% of samples and at 1.5% of sites. It was detected more
frequently in surface water than in ground water. The median concentration based on detections
from all sites was 0.01 |ig/L. The 99th percentile concentration based on detections from all sites
was 1.3 |ig/L.
33-2
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 33-2: EPA Summary Analysis of Monochlorobenzene Data from NAWQA
Study Units, 1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
4,659
1,413
6,072
% Samples
with
Detections
0.9%
5.4%
1.9%
Number
of Sites
4,159
190
4,349
% Sites
with
Detections
0.9%
13.2%
1.5%
Concentration Values
(of detections, in ug/L)
Minimum
0.001
0.002
0.001
Median
0.00805
0.01325
0.01
95th
Percen-
tile
1.1
0.06
0.3
99th
Percen-
tile
3.51
0.43
1.3
Maximum
3.51
0.43
3.51
1. RLs (Reporting Limits) for monochlorobenzene varied, but did not exceed 0.002 pg/L
33.4 Occurrence in Drinking Water
Monochlorobenzene is regulated as a volatile organic compound (VOC) in drinking
water. All non-purchased community water systems (CWSs) and non-transient non-community
water systems (NTNCWSs) are required to sample for VOCs. The maximum waiver period for
VOCs is six years for ground water systems and three years for surface water systems.
All CWSs and NTNCWSs must collect four consecutive quarterly samples during the
initial three-year compliance period.l If all four samples are non-detections, then the system may
reduce to annual sampling. After three annual samples without a detection, a system may be
granted a waiver. If a compound is detected (but at less than the MCL), the system must take one
sample per quarter until results are below the MCL (minimum of two quarterly samples for
ground water systems and four quarterly samples for surface water systems). If all quarterly
samples are below the MCL, the system may return to annual sampling. If a compound is
detected at a level greater than the MCL, the system (whether ground water or surface water)
must take four consecutive quarterly samples until all are below the MCL. If all quarterly
samples are below the MCL, the system may return to annual sampling.
The analysis of monochlorobenzene occurrence presented in the following section is
based on state compliance monitoring data from the Six-Year Review-ICR Dataset. This is the
largest and most comprehensive compliance monitoring data set compiled by EPA's Drinking
Water Program to date.
Forty-four of the Six-Year Review-ICR states provided occurrence data for
monochlorobenzene. (There were no monochlorobenzene data from Hawaii.) These data consist
of 370,519 analytical results from 50,311 public water systems (PWSs) during the period from
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
1998 to 2005. The number of sample results and systems vary by state, although the state data
sets have been reviewed and checked to ensure adequacy of coverage and completeness.
33.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 33-3
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For monochlorobenzene, 0.268% of 50,311 systems
reported detections. Exhibit 33-4 lists the minimum, median, 90th percentile, and maximum
monochlorobenzene concentrations based on detections from all systems in the Six-Year
Review-ICR Dataset. The median concentration of monochlorobenzene, based on detections
from all systems, is 0.7 |ig/L.
Exhibit 33-3: Monochlorobenzene Occurrence Data from the
Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
286,477
46,069
85,149,817
Surface Water
84,042
4,242
140,477,965
Combined Ground &
Surface Water
370,519
50,311
225,627,782
Percent with Detections
Ground Water
0.111%
0.228%
1 .205%
Surface Water
0.067%
0.707%
1.782%
Combined Ground &
Surface Water
0.101%
0.268%
1.564%
Exhibit 33-4: Monochlorobenzene Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.02
Median
0.7
90tn
Percentile
2
Maximum
42
33-4
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source Water Type
Surface Water
Detection Value (ug/L)
Minimum
0.003
Median
0.8
90tn
Percentile
1.9
Maximum
19.7
Combined Ground &
Surface Water
0.003
0.7
1.94
42
Exhibit 33-5 illustrates the geographic distribution of monochlorobenzene occurrence in
drinking water, identifying the states with systems with at least one detection. (No systems
reported detections greater than the MCL concentration; thus, no map is included for MCL
concentration exceedances.) Note that five states did not submit data for use in the Six-Year
Review (Kansas2, Louisiana, Mississippi, Pennsylvania, and Washington). Hawaii submitted
Six-Year data for most contaminants, but did not submit data for monochlorobenzene.
Detection rates were generally low for monochlorobenzene. Nine states reported
detections in more than 0.5% of their systems. In 18 states, between 0.1% and 0.5% of systems
reported detections. Eleven states reported no detections. Furthermore, no states reported
detections greater than the MCL concentration of 100 |ig/L.
Exhibit 33-5: Percentage of Systems with at Least One Monochlorobenzene
Detection, by State
'///A States with Waivers or Not Submitting
States with No Detections
Less than 0.1% of Systems Detecting
B Between 0.1% and 0.5% of Systems Detecting
^B More than 0.5% of Systems Detecting
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
33-5
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 33-6 presents the Stage 1 analysis of monochlorobenzene occurrence in drinking
water from systems and population-served by those systems in the Six-Year Review-ICR Dataset
relative to two thresholds: 50 jig/L and 100 |ig/L. No systems reported detections greater than or
equal to either threshold.
Exhibit 33-6: Monochlorobenzene Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 100|jg/L
> 50 |jg/L
Number of
Systems
Exceeding
Threshold
0
0
Percent of
Systems
Exceeding
Threshold
0.000%
0.000%
Total Population-
Served by
Systems
Exceeding
Threshold
0
0
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.000%
0.000%
Surface
Water
> 100|jg/L
> 50 |jg/L
0
0
0.000%
0.000%
0
0
0.000%
0.000%
Combined
Ground &
Surface
Water
> 100|jg/L
> 50 |jg/L
0
0
0.000%
0.000%
0
0
0.000%
0.000%
33.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 1999. ToxFAQsfor
Chlorobenzene. July 1999. Available on the Internet at: http://www.atsdr.cdc.gov/tfactsl31.html.
United States Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - Monochlorobenzene. Last modified September 10, 2007. Available on the Internet
at: http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for monochlorobenzene.]
Accessed February 21, 2008.
USEPA. 2008. TRI Explorer: Trends - Chlorobenzene. Released February 21, 2008. Available
on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for monochlorobenzene.]
Accessed March 5, 2008.
33-6
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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. Office of Water. EPA-815-B-09-006. October 2009.
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34 Nitrate (as N)
This chapter on nitrate (as N) is part of a report that is organized so that each chapter
presents information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and nitrate
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009a).
34.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for nitrate on January 30, 1991 (56 FR
3526 (USEPA, 1991)). The NPDWR established a maximum contaminant level goal (MCLG)
and maximum contaminant level (MCL) of 10 mg/L (as nitrogen (N)).l EPA based the MCLG on
a survey of epidemiologic studies of infant methemoglobinemia in populations exposed to nitrate
contaminated water. No cancer classification is currently available for nitrate (USEPA, 2009b).
Nitrate is a water soluble nitrogen-oxygen chemical unit that is formed when nitrogen
from ammonia or other sources combines with oxygenated water (Wisconsin DNR, 2003).
Nitrate occurs naturally in soil and water and is the primary source of nitrogen for plants.
Excessively high nitrate in drinking water, however, poses a health risk, especially to infants and
to pregnant or nursing women (Oregon DEQ, 2002). High concentrations occur in fertilizers,
manure, and discharges from septic tanks and because it dissolves easily in water, nitrate can
move easily from these sources into surface water or ground water (CDPHE, undated).
34.2 Use, Production, and Releases
According to the Hazardous Substance Data Bank (HSDB, 2008), a common source of
nitrates is from their use in fertilizer. Ammonium nitrate is also used in explosives, in instant
cold packs, and to make nitrous oxide.
The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for nitrate.
1 If nitrate is analyzed as NO3, the MCL is greater than or equal to 45 mg/L.
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Nitrate compounds are listed as Toxics Release Inventory (TRI) chemicals. TRI data
indicate that total off-site and on-site releases of nitrate compounds for the period 1998-2006
ranged from about 275 million pounds to approximately 332 million pounds. On-site releases
were greater than off-site releases (USEPA, 2008).
34.3 Occurrence in Ambient Water
No National Water Quality Assessment (NAWQA) Program data are available from the
United States Geological Survey (USGS) on the occurrence of nitrate in ambient waters from the
Pesticide National Synthesis Project (Gilliom et a/., 2007) or the EPA Summary Analysis of
Cycle 1 data.
34.4 Occurrence in Drinking Water
Community water systems (CWSs), non-transient non-community water systems
(NTNCWSs), and transient non-community water systems (TNCWSs) are all required to sample
for nitrate. Waivers are not permitted.
Initially, ground water CWSs and NTNCWSs and all TNCWSs must collect one sample
each year. Surface water CWSs and NTNCWSs must collect four quarterly samples. If all results
are less than 1A the MCL, then ground water systems and TNCWSs may continue monitoring
annually and surface water systems may reduce to annual monitoring. If a result is greater than or
equal to !/2 the MCL (but less than the MCL), CWSs and NTNCWSs must collect four
consecutive quarterly samples that are all less than the MCL (for ground water systems) or less
than !/2 the MCL (for surface water systems). TNCWSs may continue with annual monitoring.
Once the four quarterly samples are all below the MCL (or 1A the MCL for surface water
systems), the system may continue to monitor routinely. If a result is greater than or equal to the
MCL, the system must collect a confirmation sample and average it with the original sample to
determine compliance with the MCL. The system must monitor quarterly until four consecutive
quarterly samples are less than the MCL (unless the state or EPA allows reduced monitoring
under an enforcement action). After that, the system may continue to monitor routinely.
The analysis of nitrate occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
Forty-four of the Six-Year Review-ICR states provided occurrence data for nitrate. (No
nitrate data from Arkansas were analyzed for the Six-Year Review. Arkansas did submit data for
nitrate plus nitrite, but only individual nitrate and nitrite results were analyzed.) These data
consist of 1,052,487 analytical results from 119,537 public water systems (PWSs) during the
period from 1998 to 2005. The number of sample results and systems vary by state, although the
state data sets have been reviewed and checked to ensure adequacy of coverage and
completeness.
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34.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 34-1
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For nitrate, 69.942% of 119,537 systems reported
detections. Exhibit 34-2 lists the minimum, median, 90th percentile, and maximum nitrate
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of nitrate, based on detections from all systems, is 1.8 mg/L.
Exhibit 34-1: Nitrate Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
899,945
114,764
92,900,757
Surface Water
152,542
4,773
136,607,279
Combined Ground &
Surface Water
1,052,487
119,537
229,508,036
Percent with Detections
Ground Water
57.670%
69.466%
85.648%
Surface Water
83.304%
81.374%
94.559%
Combined Ground &
Surface Water
61.385%
69.942%
90.952%
Exhibit 34-2: Nitrate Summary Statistics
Source Water Type
Ground Water
Detection Value (mg/L)
Minimum
1.04E-06
Median
1.6
90tn
Percentile
7.53
Maximum
99
Surface Water
7.34E-05
2.71
9.04
48.5
Combined Ground &
Surface Water
1.04E-06
1.8
7.91
99
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The following maps illustrate the geographic distribution of nitrate occurrence in drinking
water. Exhibit 34-3 shows the states with systems with at least one detection and Exhibit 34-4
shows the states with systems with at least one detection greater than the MCL concentration.
Note that five states did not submit data for use in the Six-Year Review (Kansas2, Louisiana,
Mississippi, Pennsylvania, and Washington). Arkansas did submit Six-Year data for most
contaminants (including nitrate plus nitrite) but did not submit individual nitrate data.
Detection rates were high for nitrate. In eight states, more than 90% of systems detected
nitrate. In 16 states, between 75% and 90% of systems detected nitrate. For seven states, more
than 5% of systems reported at least one detection greater than the MCL concentration of 10
mg/L.
Exhibit 34-3: Percentage of Systems with at Least One Nitrate Detection, by State
ffifr Stale* wltfi Waiver* or Not Submitting
States with No Detection*
| Less or Equal to 75% of Systems Detecting
B Between 75% and 90%of Systems Detecting
More than 90% of Systems Delecting
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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Exhibit 34-4: Percentage of Systems with at Least One Nitrate Detection Greater
than the MCL Concentration (> 10 mg/L), by State
MCL
• Lea; than 1% of Systems with Detections > MCL
Between 1% and 5% of Systems with Detections > MCL
| Mora than 5% of Systems with Detections > MCL
Exhibit 34-5 presents the Stage 1 analysis of nitrate occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 5 mg/L and 10 mg/L. More than 11,100 (9.294% of) systems, serving more than
44 million persons, reported at least one detection greater than or equal to 5 mg/L; and almost
3,000 (2.487% of) systems, serving almost 16.8 million persons, reported at least one detection
greater than 10 mg/L.
Exhibit 34-5: Nitrate Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 1 0 mg/L
> 5 mg/L
Number of
Systems
Exceeding
Threshold
2,855
10,742
Percent of
Systems
Exceeding
Threshold
2.488%
9.360%
Total Population-
Served by Systems
Exceeding
Threshold
5,278,260
19,289,360
Percent of
Population-Served
by Systems
Exceeding
Threshold
5.682%
20.763%
Surface
Water
> 1 0 mg/L
> 5 mg/L
118
368
2.472%
7.710%
11,498,833
24,830,964
8.417%
18.177%
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source
Water
Type
Combine
d Ground
& Surface
Water
Threshold
> 1 0 mg/L
> 5 mg/L
Number of
Systems
Exceeding
Threshold
2,973
11,110
Percent of
Systems
Exceeding
Threshold
2.487%
9.294%
Total Population-
Served by Systems
Exceeding
Threshold
16,777,093
44,120,324
Percent of
Population-Served
by Systems
Exceeding
Threshold
7.310%
19.224%
34.5 References
Colorado Department of Public Health and the Environment (CDPHE). Undated. Fact Sheet -
Nitrate in Drinking Water. Available on the Internet at:
http://www.cdphe.state.co.us/wq/drinkingwater/pdf/FactSheets/NitrateInDrinkingWater.pdf.
Accessed March 15, 2008.
Gilliom, R.J., I.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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
Hazardous Substance Data Bank (HSDB). 2008. AMMONIUM NITRATE. Available on the
Internet at: http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen7HSDB. [Search for AMMONIUM
NITRATE.] Accessed: July 8, 2008.
Oregon Department of Environmental Quality (DEQ). 2002. Nitrate in Drinking Water.
Available on the Internet at:
http://www.deq.state.or.us/wq/pubs/factsheets/groundwater/nitratedw.pdf. Accessed March 15,
2008.
United States Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
USEPA. 2008. TRI Explorer: Trends - Nitrate Compounds. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for nitrate
compounds.] Accessed March 6, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
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USEPA. 2009b. Six-Year Review 2 - Health Effects Assessment - Summary Report. Office of
Water. EPA-822-R-09-006. October 2009.
Wisconsin Department of Natural Resources (DNR). 2003. Nitrate. Available on the Internet at:
http://www.dnr.state.wi.us/org/water/dwg/nitrate.htm. Accessed: July 3, 2008.
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35 Nitrite (as N)
This chapter on nitrite (as N) is part of a report that is organized so that each chapter
presents information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and nitrite
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009a).
35.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for nitrite on January 30, 1991 (56 FR
3526 (USEPA, 1991)). The NPDWR established a maximum contaminant level goal (MCLG)
and a maximum contaminant level (MCL) of 1.0 mg/L (as N). EPA based the MCLG on
extrapolation from nitrate, assuming the conversion of 10 percent of nitrate-nitrogen to nitrite-
nitrogen. No cancer classification is currently available for nitrite (USEPA, 2009b).
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2007),
nitrites are naturally occurring inorganic ions that are part of the nitrogen cycle. Microbial action
in soil or water decomposes wastes containing organic nitrogen into ammonia, which is then
oxidized to nitrite and nitrate. Like nitrate, nitrite is highly soluble in water and will move
through soil and into ground water (ATSDR, 2007). It will remain in water until consumed by
plants or other organisms (HSDB, 2008).
35.2 Use, Production, and Releases
Sodium nitrite is used in the chemical and pharmaceutical industries for making dyes and
in the synthesis of pharmaceuticals and agricultural pesticides. It is also used to form nitrous
acid, as a rubber accelerator, as a preservative for meats and fish, and as a photographic and
analytical reagent. A minor use is as a fertilizer (HSDB, 2008).
The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for nitrite.
Nitrite is not listed as a Toxics Release Inventory (TRI) chemical; no TRI release records
are available.
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35.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of nitrite in
ambient water are available from the NAWQA program.
35.3.1 EPA Summary Analysis of NAWQA Data
EPA, with the cooperation of the USGS, has performed a summary analysis of all Cycle
1 water monitoring data from all study units (1992-2001) for nitrite. Detection frequencies were
computed as the percentage of samples and sites with detections (i.e., with at least one result
equal to or greater than the reporting limit). Sample detections can be biased by frequent
sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 35-1. Overall, nitrite was
detected in 51.6% of samples and at 38.5% of sites. Nitrite was detected more frequently in
surface water than in ground water. The median concentration based on detections from all sites
was 0.02 mg/L. The 99
mg/L.
,th
percentile concentration based on detections from all sites was 0.383
Exhibit 35-1: EPA Summary Analysis of Nitrite (as N) Data from NAWQA Study
Units, 1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
6,972
28,889
35,861
% Samples
with
Detections
19.6%
59.3%
51.6%
Number
of Sites
5,470
2,754
8,224
% Sites
with
Detections
22.4%
70.7%
38.5%
Concentration Values
(of detections, in mg/L)
Minimum
0.001
0.001
0.001
Median
0.02
0.02
0.02
95th
Percen-
tile
0.14
0.13
0.13
99th
Percen-
tile
0.428
0.38
0.383
Maximum
1.617
1.9
1.9
1. RLs (Reporting Limits) for nitrite (as N) varied, but did not exceed 0.001 mg/L.
35.4 Occurrence in Drinking Water
Community water systems (CWSs), non-transient non-community water systems
(NTNCWSs), and transient non-community water systems (TNCWSs) are all required to sample
for nitrite. Waivers are not permitted.
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All public water systems (PWSs) must collect one sample during their initial compliance
period. If a result is less than /^ the MCL, then the system must monitor at the frequency
specified by the state. If a result is greater than or equal to l/2 the MCL (but less than the MCL),
the system must take one sample per quarter for at least a year until they obtain four consecutive
samples below the MCL. After that, the system may continue to monitor routinely. If a result is
greater than or equal to the MCL, the system must collect a confirmation sample and average it
with the original sample to determine compliance with the MCL. The system must then monitor
quarterly until they obtain four consecutive samples below the MCL (unless the state or EPA
allows reduced monitoring under an enforcement action). After that, the system may continue to
monitor routinely.
The analysis of nitrite occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
Forty-four of the Six-Year Review-ICR states provided occurrence data for nitrite. (No
nitrite data from Arkansas were analyzed for the Six-Year Review. Arkansas did submit data for
nitrate plus nitrite, but only individual nitrate and nitrite results were analyzed.) These data
consist of 397,175 analytical results from 86,313 systems during the period from 1998 to 2005.
The number of sample results and systems vary by state, although the state data sets have been
reviewed and checked to ensure adequacy of coverage and completeness.
35.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 35-2
presents the number of samples and systems, as well as the population-served by the systems,
and the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For nitrite, 22.318% of 86,313 systems reported
detections. Exhibit 35-3 lists the minimum, median, 90th percentile, and maximum nitrite
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of nitrite, based on detections from all systems, is 0.02 mg/L.
Exhibit 35-2: Nitrite Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
345,206
82,738
81,271,403
Surface Water
51,969
3,575
126,713,410
Combined Ground &
Surface Water
397,175
86,313
207,984,813
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Percent with Detections
Ground Water
13.251%
22.285%
36.640%
Surface Water
6.477%
23.077%
49.731%
Combined Ground &
Surface Water
12.365%
22.318%
44.615%
Exhibit 35-3: Nitrite Summary Statistics
Source Water Type
Ground Water
Detection Value (mg/L)
Minimum
0.000001
Median
0.02
90tn
Percent! le
0.4
Maximum
13
Surface Water
0.000002
0.03
0.45
8.68
Combined Ground &
Surface Water
0.000001
0.02
0.4
13
The following maps illustrate the geographic distribution of nitrite occurrence in drinking
water. Exhibit 35-4 shows the states with systems with at least one detection and Exhibit 35-5
shows the states with systems with at least one detection greater than the MCL concentration.
Note that five states did not submit data for use in the Six-Year Review (Kansas1, Louisiana,
Mississippi, Pennsylvania, and Washington). Arkansas did submit Six-Year data for most
contaminants (including nitrate plus nitrite) but did not submit individual nitrite data.
Detection rates were high for nitrite. In four states, more than 50% of systems detected
nitrite. In 19 states, between 10% and 50% of systems detected nitrite. For four states, more than
1% of systems reported at least one detection greater than the MCL concentration of 1 mg/L.
1 Kansas submitted data after the data management and analyses had been conducted; data from Kansas are not
included in the analyses.
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Exhibit 35-4: Percentage of Systems with at Least One Nitrite Detection,
by State
States with Waivers or Not Submitting
States with No Detections
Less than 10% of Systems Detecting
Between 10% and 50% of Systems Detecting
More than 50% of Systems Detecting
Exhibit 35-5: Percentage of Systems with at Least One Nitrite Detection Greater
than the MCL Concentration (>1 mg/L), by State
t^j States with Waivers or Not Submitting
States with No Detections > MCL
Less than 0.5% of Systems with Detections > MCL
^B Between 0.5% and 1% of Systems with Detections > MCL
H More than 1% of Systems with Detections > MCL
Exhibit 35-6 presents the Stage 1 analysis of nitrite occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 0.5 mg/L and 1 mg/L. Nearly 1,400 (1.568% of) systems, serving almost 26.5
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million persons, reported at least one detection greater than or equal to 0.5 mg/L; and 635
(0.736% of) systems, serving more than 10 million persons, reported at least one detection
greater than 1 mg/L.
Exhibit 35-6: Nitrite Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 1 mg/L
> 0.5 mg/L
Number of
Systems
Exceeding
Threshold
584
1,241
Percent of
Systems
Exceeding
Threshold
0.706%
1.500%
Total Population-
Served by
Systems
Exceeding
Threshold
729,751
4,915,364
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.898%
6.048%
Surface
Water
> 1 mg/L
> 0.5 mg/L
51
112
1 .427%
3.133%
9,337,280
21,530,847
7.369%
16.992%
Combined
Ground &
Surface
Water
> 1 mg/L
>0.5 mg/L
635
1,353
0.736%
1.568%
10,067,031
26,446,211
4.840%
12.715%
35.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2007. "Nitrate/Nitrite Toxicity:
What Are Nitrate and Nitrite?" Last updated September 24, 2007. Available on the Internet at:
http://www.atsdr.cdc.gov/csem/nitrate/nitrate.html. Accessed March 21, 2008.
Hazardous Substance Data Bank (HSDB). 2008. SODIUM NITRITE. Available on the Internet
at: http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen7HSDB. [Search for Sodium Nitrite.] Accessed:
July 8, 2008.
United States Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
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. Office of Water. EPA-815-B-09-006. October 2009.
USEPA. 2009b. Six-Year Review 2 - Health Effects Assessment - Summary Report. Office of
Water. EPA-822-R-09-006. October 2009.
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36 Pentachlorophenol
This chapter on pentachlorophenol is part of a report that is organized so that each chapter
presents information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and
pentachlorophenol occurrence estimates in ambient water and drinking water. All drinking water
occurrence estimates were based on data from the National Compliance Monitoring Information
Collection Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR
Dataset"). For detailed information regarding this dataset, data management, data quality
assessments, and the analytical approach used to generate all contaminant occurrence estimates
presented in this chapter, please refer to USEPA (2009).
36.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for pentachlorophenol on July 1, 1991
(56 FR 30266 (USEPA, 1991)). The NPDWR established a maximum contaminant level goal
(MCLG) of zero based on a cancer classification of B2, probable human carcinogen. The
NPDWR also established a maximum contaminant level (MCL) of 1 |ig/L, based on analytical
feasibility.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2001),
pentachlorophenol (CeHClsO) is a colorless crystalline synthetic chemical. It has very little odor
at room temperature but takes on a sharp characteristic phenolic smell when heated. It can be
found in two forms: as pure pentachlorophenol and as a highly water-soluble sodium salt. At
hazardous waste sites, impure pentachlorophenol is dark gray to brown and exists as dust, beads,
or flakes. Impurities typically include polychlorinated dibenzo-p-dioxins and dibenzofurans.
Pentachlorophenol tends to adhere to soils and sediment, and adhere to particulates in water. It
will degrade in soil and surface waters due to sunlight and microorganisms (ATSDR, 2001).
36.2 Use, Production, and Releases
Once a widely used biocide and wood preservative, pentachlorophenol has been restricted
to use by certified applicators since 1984. It is still used industrially as a wood preservative for
utility poles, railroad ties, and wharf pilings (ATSDR, 2001).
The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for pentachlorophenol.
Pentachlorophenol is listed as a Toxics Release Inventory (TRI) chemical. TRI data
indicate that total off-site and on-site releases for the period 1998-2006 ranged from
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approximately 2,600 pounds to approximately 272,000 pounds, with a general decrease over time
(USEPA, 2008).
36.3 Occurrence in Ambient Water
No National Water Quality Assessment (NAWQA) Program data are available from the
United States Geological Survey (USGS) on the occurrence of pentachlorophenol in ambient
waters from the Pesticide National Synthesis Project (Gilliom et a/., 2007) or the EPA Summary
Analysis of Cycle 1 data.
36.4 Occurrence in Drinking Water
Pentachlorophenol is regulated as a synthetic organic chemical (SOC) in drinking water.
All non-purchased community water systems (CWSs) and non-transient non-community water
systems (NTNCWSs) are required to sample for SOCs. The maximum waiver period for SOCs is
three years, but this waiver can be renewed indefinitely. (Systems may receive a waiver at any
time without having collected an SOC sample. With a waiver, systems are not required to collect
an SOC sample.)
All CWSs and NTNCWSs without an SOC waiver must collect four consecutive
quarterly samples during the initial three-year compliance period.l If all four samples are non-
detections, then a system serving less than 3,300 persons may reduce to one sample during each
consecutive compliance period; a system serving more than 3,300 persons may reduce to two
quarterly samples within a 12-month period during a 3-year compliance period. If a chemical is
detected (but is less than the MCL), the system must take one sample per quarter until results are
below the MCL (minimum of two quarterly samples for ground water systems and four quarterly
samples for surface water systems). If all quarterly samples are below the MCL, the system may
return to annual sampling. If a chemical is detected at a level greater than the MCL, the system
(whether ground water or surface water) must take quarterly samples until four consecutive
quarters are below the MCL. If all quarterly samples are below the MCL, the system may return
to annual sampling.
The analysis of pentachlorophenol occurrence presented in the following section is based
on state compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest
and most comprehensive compliance monitoring data set compiled by EPA's Drinking Water
Program to date.
Forty-three of the Six-Year Review-ICR states provided occurrence data for
pentachlorophenol. (There were no pentachlorophenol data from Hawaii or Oklahoma.) These
data consist of 136,475 analytical results from 34,339 public water systems (PWSs) during the
period from 1998 to 2005. The number of sample results and systems vary by state, although the
state data sets have been reviewed and checked to ensure adequacy of coverage and
completeness.
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
36-2
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
36.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 36-1
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For pentachlorophenol, 0.731% of 34,339 systems
reported detections. Exhibit 36-2 lists the minimum, median, 90th percentile, and maximum
pentachlorophenol concentrations based on detections from all systems in the Six-Year Review-
ICR Dataset. The median concentration of pentachlorophenol, based on detections from all
systems, is 0.08 |ig/L.
Exhibit 36-1: Pentachlorophenol Occurrence Data from the
Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
107,551
31,142
68,667,605
Surface Water
28,924
3,197
121,840,104
Combined Ground &
Surface Water
136,475
34,339
190,507,709
Percent with Detections
Ground Water
0.243%
0.639%
5.996%
Surface Water
0.270%
1 .627%
4.585%
Combined Ground &
Surface Water
0.248%
0.731%
5.094%
Exhibit 36-2: Pentachlorophenol Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.01
Median
0.08
90tn
Percentile
0.6
Maximum
10
Surface Water
0.01
0.09
0.51
4
36-3
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source Water Type
Combined Ground &
Surface Water
Detection Value (ug/L)
Minimum
0.01
Median
0.08
90tn
Percentile
0.6
Maximum
10
The following maps illustrate the geographic distribution of pentachlorophenol
occurrence in drinking water. Exhibit 36-3 shows the states with systems with at least one
detection and Exhibit 36-4 shows the states with systems with at least one detection greater than
the MCL concentration. Note that five states did not submit data for use in the Six-Year Review
(Kansas2, Louisiana, Mississippi, Pennsylvania, and Washington). Hawaii and Oklahoma did
submit Six-Year data for most contaminants, but did not submit data for pentachlorophenol.
In five states, greater than 2% of the systems detected pentachlorophenol. Four out of five
of these states are located in the eastern half of the United States. In four states, between 1% and
2% of systems reported detections. Seven states reported at least one detection greater than the
MCL concentration of 1 |ig/L. In two states, more than 0.2% of systems reported detections
greater than 1 |ig/L.
Exhibit 36-3: Percentage of Systems with at Least One Pentachlorophenol
Detection, by State
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 36-4: Percentage of Systems with at Least One Pentachlorophenol
Detection Greater than the MCL Concentration (> 1 ug/L), by State
SI*'68 witn Waivers or Not Submitting
States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
Between 0.1% and 0.2% of Systems with Detections > MCL
More than 0.2% of Systems with Detections > MCL
Exhibit 36-5 presents the Stage 1 analysis of pentachlorophenol occurrence in drinking
water from systems and population-served by those systems in the Six-Year Review-ICR Dataset
relative to two thresholds: 0.5 |ig/L and 1 ng/L. A total of 29 (0.084% of) systems, serving
almost 750,000 persons, reported at least one detection greater than or equal to 0.5 |ig/L; and 8
(0.023% of) systems, serving almost 12,000 persons, reported at least one detection greater than
Exhibit 36-5: Pentachlorophenol Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 1 pg/L
>0.5|jg/L
Number of
Systems
Exceeding
Threshold
7
21
Percent of
Systems
Exceeding
Threshold
0.022%
0.067%
Total Population-
Served by
Systems
Exceeding
Threshold
11,376
434,892
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.017%
0.633%
Surface
Water
> 1 pg/L
>0.5 |jg/L
1
8
0.031%
0.250%
429
310,346
0.000%
0.255%
36-5
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source
Water
Type
Combined
Ground &
Surface
Water
Threshold
> 1 pg/L
>0.5|jg/L
Number of
Systems
Exceeding
Threshold
8
29
Percent of
Systems
Exceeding
Threshold
0.023%
0.084%
Total Population-
Served by
Systems
Exceeding
Threshold
11,805
745,238
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.006%
0.391%
36.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2001. Toxicological Profile for
Pentachlorophenol. September 2001. Available on the Internet at:
http://www.atsdr.cdc.gov/toxprofiles/tp51 .html.
Gilliom, R.J., I.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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
United States Environmental Protection Agency (USEPA). 1991. Drinking Water; National
Primary Drinking Water Regulations; Monitoring for Volatile Organic Chemicals; MCLGs and
MCLs for Aldicarb, Aldicarb Sulfoxide, Aldicarb Sulfone, Pentachlorophenol, and Barium; Final
Rule. Federal Register. Vol. 56, No. 126. p. 30266, July 1, 1991.
USEPA. 2008. TRIExplorer: Trends -Pentachlorophenol. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for
Pentachlorophenol.] Accessed March 5, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
37 Picloram
This chapter on picloram is part of a report that is organized so that each chapter presents
information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and picloram
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
37.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for picloram on July 17, 1992 (57 FR
31776 (USEPA, 1992)). The NPDWR established a maximum contaminant level goal (MCLG)
and a maximum contaminant level (MCL) of 500 |ig/L. The Agency based the MCLG on a
reference dose (RfD) of 70 jig/kg-day (0.07 mg/kg-day) and a cancer classification of D, not
classifiable as to human carcinogenicity.
Picloram (CeHsCls^Ch) is a colorless crystalline organic solid. It is moderately to highly
persistent in the soil environment (EXTOXNET, 1996). Furthermore, picloram is extremely
soluble in water and, therefore, is highly mobile. It will leach easily and, given the slow rate at
which it breaks down, will remain in water for an extended period. It generally does not pose a
threat to humans at the levels detected, but there are concerns about its effects on non-target
plants (USEPA, 1995).
37.2 Use, Production, and Releases
Picloram is a systemic herbicide used for control of woody plants and a wide range of
broad-leaved weeds. Most grasses are resistant to picloram, so it is used in range management
programs (EXTOXNET, 1996). It is applied in the greatest amounts to pasture and rangeland,
followed by forestry (USEPA, 1995).
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 37-1 presents the production of picloram in the United States from 1986 to 2002.
Note that the production of picloram in the United States has remained constant since 1986.
37-1
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 37-1: Production of Picloram in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
> 1 million - 10 million pounds
> 1 million - 10 million pounds
> 1 million - 10 million pounds
> 1 million - 10 million pounds
> 1 million - 10 million pounds
Source: USEPA, 2003
Exhibit 37-2, compiled by the United States Geological Survey (USGS, 2007), shows the
geographic distribution of estimated average annual picloram use in the United States from 1999
through 2004. A breakdown of use by crop is also included. The map was created by the USGS
using state-level data sets on pesticide use rates from 1999-2004 compiled by the CropLife
Foundation, at the Crop Protection Research Institute, combined with county-level data on
harvested crop acreage obtained from the 2002 Census of Agriculture. Due to the nature of the
data sources, non-agricultural uses are not reflected here, and variations in use at the county-level
are also not well represented (Thelin and Gianessi, 2000). The USGS (2007) estimates that
almost 1.9 million pounds of picloram active ingredient were used on average each year between
1999 and 2004.
37-2
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 37-2: Estimated Annual Agricultural Use for Picloram (c. 2002)
PICLORAM - herbicide
2002 estimated annual agricultural use
Average annual use of
active ingredient
(pounds per square mile of agricultural
land in county)
LJ no estimated use
D 0.001 to 0.054
D 0.055 to 0.166
D 0.167 to 0.415
D 0.416 to 1.067
• >= 1.068
Total
Cr°Ps pounds applied
pasture land
other hay
cropland in summer fallow
wheat for grain
barley for grain
oats for grain
1718097
169969
9779
9170
666
BO
Percent
national use
90.06
8.91
0.51
0.43
0.03
0.00
Source: USGS, 2007
Picloram is listed as a Toxics Release Inventory (TRI) chemical. TRI data indicate that
total off-site and on-site releases of picloram for the period 1998-2006 ranged from about 52,000
pounds to about 380,000 pounds, with a general decrease over time. Only on-site releases were
reported (USEPA, 2008).
37.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The USGS National
Water Quality Assessment (NAWQA) program is a national-scale assessment of the occurrence
of contaminants in ambient surface and ground water. Contaminant occurrence in ambient water
provides information on the potential for contaminants to adversely affect drinking water
supplies. Data on the occurrence of picloram in ambient water are available from the NAWQA
program.
37.3.1 NA WQA Pesticide National Synthesis Project
The NAWQA Pesticide National Synthesis Project is a national-scale assessment of the
occurrence and behavior of pesticides in streams and ground water of the United States and the
potential for pesticides to adversely affect drinking water supplies or aquatic ecosystems. Under
the National Synthesis Project, the USGS monitored picloram between 1992 and 2001 in streams
37-3
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
and wells across the country (Gilliom etal., 2007). The maximum long-term method detection
limit for picloram was 0.040 |ig/L.
In NAWQA stream samples (Exhibit 37-3), picloram was only detected in mixed land use
settings (at a frequency of 0.08%). The highest concentration at a mixed land use setting was
0.010 |ig/L.
Exhibit 37-3: USGS National Synthesis Summary of NAWQA Monitoring of
Picloram in Streams, 1992-2001
Land Use
Type
Agricultural
Mixed
Undeveloped
Urban
No. of Samples
(No. of Sites)
1,465(62)
800 (36)
101 (5)
520(19)
Detection
Frequency
0.00%
0.08%
0.00%
0.00%
50tn Percent! le
(Median)
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
95th Percentile
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
Maximum
Concentration
(in ug/L)
ND1
0.010
ND1
ND1
Source: Gilliom et a/., 2007
1. ND = not detected (Concentration is less than the maximum long term method detection limit and is expected to
be less than any higher percentile concentration shown in the table)
In ground water NAWQA samples (Exhibit 37-4), picloram was found at frequencies
ranging from 0% of samples in undeveloped areas to 0.13% in mixed land use settings, 0.17% in
agricultural settings, and 0.61% in urban areas. The 95th percentile concentrations were less than
the method detection limit in all settings. The highest concentration, 3.91 |ig/L, was found in an
urban area.
Exhibit 37-4: USGS National Synthesis Summary of NAWQA Monitoring of
Picloram in Ground Water, 1992-2001
Land Use Type
Agricultural
Mixed
Undeveloped
Urban
Number
of Wells
1,168
1,545
22
659
Detection
Frequency
0.17%
0.13%
0%
0.61%
50tn Percentile
(Median)
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
95th Percentile
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
Maximum
Concentration
(in ug/L)
2.2
0.17
ND1
3.91
Source: Gilliom et a/., 2007
1. ND = not detected (Concentration is less than the maximum long term method detection limit and is expected to
be less than any higher percentile concentration shown in the table)
37-4
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
37.3.2 EPA Summary Analysis ofNAWQA Data
Whereas the NAWQA program often uses the most representative data for a site to
calculate summary statistics, EPA, with the cooperation of the USGS, has performed a summary
analysis of all Cycle 1 water monitoring data from all study units (1992-2001) for picloram.
Detection frequencies were computed as the percentage of samples and sites with detections (i.e.,
with at least one result equal to or greater than the reporting limit). Sample detections can be
biased by frequent sampling in areas with high (or low) occurrence. Calculating the percentage of
sites with detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 37-5. Overall, picloram was
detected in 0.2% of samples and at 0.4% of sites. Picloram detection rates were similarly low at
both surface water and ground water sites. The median concentration based on detections from
all sites was 0.17 |ig/L. The 99
3.91
,th
percentile concentration based on detections from all sites was
Exhibit 37-5: EPA Summary Analysis of Picloram Data from NAWQA Study Units,
1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
3,966
5,519
9,485
% Samples
with
Detections
0.3%
0.1%
0.2%
Number
of Sites
3,607
891
4,498
% Sites
with
Detections
0.3%
0.8%
0.4%
Concentration Values
(of detections, in ug/L)
Minimum
0.05
0.004
0.004
Median
0.255
0.1
0.17
95th
Percen-
tile
3.91
2.7
3.305
99th
Percen-
tile
3.91
2.7
3.91
Maximum
3.91
2.7
3.91
1. RLs (Reporting Limits) for picloram varied, but did not exceed 0.02 ug/L. Note that because this EPA analysis
involves more data points than the USGS analyses presented above, a direct comparison is not possible.
37.4 Occurrence in Drinking Water
Picloram is regulated as a synthetic organic chemical (SOC) in drinking water. All non-
purchased community water systems (CWSs) and non-transient non-community water systems
(NTNCWSs) are required to sample for SOCs. The maximum waiver period for SOCs is three
years, but this waiver can be renewed indefinitely. (Systems may receive a waiver at any time
without having collected an SOC sample. With a waiver, systems are not required to collect an
SOC sample.)
37-5
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
All CWSs and NTNCWSs without an SOC waiver must collect four consecutive
quarterly samples during the initial three-year compliance period.l If all four samples are non-
detections, then a system serving less than 3,300 persons may reduce to one sample during each
consecutive compliance period; a system serving more than 3,300 persons may reduce to two
quarterly samples within a 12-month period during a 3-year compliance period. If a chemical is
detected (but is less than the MCL), the system must take one sample per quarter until results are
below the MCL (minimum of two quarterly samples for ground water systems and four quarterly
samples for surface water systems). If all quarterly samples are below the MCL, the system may
return to annual sampling. If a chemical is detected at a level greater than the MCL, the system
(whether ground water or surface water) must take quarterly samples until four consecutive
quarters are below the MCL. If all quarterly samples are below the MCL, the system may return
to annual sampling.
The analysis of picloram occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
Forty-three of the Six-Year Review-ICR states provided occurrence data for picloram.
(There were no picloram data from Hawaii or Oklahoma.) These data consist of 121,920
analytical results from 32,910 public water systems (PWSs) during the period from 1998 to 2005.
The number of sample results and systems vary by state, although the state data sets have been
reviewed and checked to ensure adequacy of coverage and completeness.
37.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 37-6
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For picloram, 0.413% of 32,910 systems reported
detections. Exhibit 37-7 lists the minimum, median, 90th percentile, and maximum picloram
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of picloram, based on detections from all systems, is 0.24 |ig/L.
Exhibit 37-6: Picloram Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
99,734
29,914
66,798,378
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
37-6
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Surface Water
22,186
2,996
119,588,052
Combined Ground &
Surface Water
121,920
32,910
186,386,430
Percent with Detections
Ground Water
0.159%
0.351%
4.486%
Surface Water
0.180%
1.035%
4.624%
Combined Ground &
Surface Water
0.163%
0.413%
4.575%
Exhibit 37-7: Picloram Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.01
Median
0.25
90tn
Percentile
2.48
Maximum
190
Surface Water
0.01
0.2
3.235
100
Combined Ground &
Surface Water
0.01
0.24
3
190
Exhibit 37-8 illustrates the geographic distribution of picloram occurrence in drinking
water, identifying the states with systems with at least one detection. (No systems reported
detections greater than the MCL concentration; thus, no map is included for MCL concentration
exceedances.) Note that five states did not submit data for use in the Six-Year Review (Kansas2,
Louisiana, Mississippi, Pennsylvania, and Washington). Hawaii and Oklahoma did submit Six-
Year data for most contaminants, but did not submit data for picloram.
Detection rates were generally low for picloram; only seven states reported detections in
more than 1% of their systems. In five states, between 0.5% and 1% of systems reported
detections. Fourteen states reported no detections. Furthermore, no states reported detections
greater than the MCL concentration of 500 |ig/L.
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
37-7
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 37-8: Percentage of Systems with at Least One Picloram Detection,
by State
Estates with Waivers or Not Submitting
States with No Detections
Less than 0.5% of Systems Detecting
Between 0.5% and 1% of Systems Detecting
More than 1% of Systems Detecting
Exhibit 37-9 presents the Stage 1 analysis of picloram occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 250 jig/L and 500 |ig/L. No systems reported detections greater than or equal to
either threshold.
Exhibit 37-9: Picloram Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 500 |jg/L
> 250 |jg/L
Number of
Systems
Exceeding
Threshold
0
0
Percent of
Systems
Exceeding
Threshold
0.000%
0.000%
Total Population-
Served by
Systems
Exceeding
Threshold
0
0
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.000%
0.000%
Surface
Water
> 500 |jg/L
> 250 |jg/L
0
0
0.000%
0.000%
0
0
0.000%
0.000%
Combined
Ground &
Surface
Water
> 500 |jg/L
> 250 |jg/L
0
0
0.000%
0.000%
0
0
0.000%
0.000%
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
37.5 References
Extension Toxicology Network (EXTOXNET). 1996. EXTOXNET Pesticide Information
Profiles-Picloram. Last modified June 1996. Available on the Internet at:
http://extoxnet.orst.edu/pips/picloram.htm. Accessed July 3, 2008.
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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
Thelin, G.P. and L.P. Gianessi. 2000. Method for Estimating Pesticide Use for County Areas of
the Conterminous United States. U.S. Geological Survey Open-File Report 00-250, 62 p.
Available on the Internet at: http://ca.water.usgs.gov/pnsp/rep/ofr00250/ofr00250.pdf.
United States Environmental Protection Agency (USEPA). 1992. Drinking Water; National
Primary Drinking Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals;
National Primary Drinking Water Regulations Implementation; Final Rule. Federal Register.
Vol. 57, No. 138. p. 31776, July 17, 1992.
USEPA. 1995. R.E.D. FACTS: Picloram. August 1995. Available on the Internet at:
http://www.epa.gov/oppsrrdl/REDs/factsheets/0096fact.pdf.
USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - Picloram. Last modified September 10, 2007. Available on the Internet at:
http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for picloram.] Accessed February
21,2008.
USEPA. 2008. TRI Explorer: Trends - Picloram. Released February 21, 2008. Available on the
Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for picloram.] Accessed March 7,
2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
United States Geological Survey (USGS). 2007. 2002 Pesticide Use Maps. Available on the
Internet at:
http://water.usgs.gov/nawqa/pnsp/usage/maps/show map. php?vear=02&map=m 1051.
Accessed March 6, 2008.
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38 Polychlorinated Biphenyls (PCBs)
This chapter on polychlorinated biphenyls (PCBs) is part of a report that is organized so
that each chapter presents information on one specific contaminant. Chapter 1 of this report,
Introduction, presents background information on all sources of data used as well as the
analytical approach used to estimate contaminant occurrence in drinking water. This contaminant
chapter includes background information (such as regulatory history, general chemical
information, and environmental fate and behavior), use and environmental release information,
and PCBs occurrence estimates in ambient water and drinking water. All drinking water
occurrence estimates were based on data from the National Compliance Monitoring Information
Collection Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR
Dataset"). For detailed information regarding this dataset, data management, data quality
assessments, and the analytical approach used to generate all contaminant occurrence estimates
presented in this chapter, please refer to USEPA (2009).
38.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for PCBs on January 30, 1991 (56 FR
3526 (USEPA, 1991)). The NPDWR established a maximum contaminant level goal (MCLG) of
zero based on a cancer classification of B2, probable human carcinogen. The NPDWR also
established a maximum contaminant level (MCL) of 0.5 |ig/L based on analytical feasibility.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2001),
there are no known natural sources of PCBs. PCBs are mixtures of up to 209 individual
chlorinated compounds. (The chemical formula for all PCBs is Ci2Hio-xClx.) PCBs are either oily
liquids or solids that are colorless to light yellow and have no known smell or taste. Some PCBs
can exist as a vapor in air. PCBs are very persistent and stable; they do not readily biodegrade.
They tend to remain with soil and do not leach significantly. If applied to water, PCBs tend to
become associated with particles in the water and become part of the sediments. They
accumulate significantly in aquatic organisms. Many commercial PCB mixtures are known in the
United States by the trade name Aroclor (ATSDR, 2001).
38.2 Use, Production, and Releases
PCBs have been used as coolants and lubricants in transformers, capacitors, and other
electrical equipment because they are good insulators and do not burn easily. The manufacture of
PCBs was stopped in the United States in 1977 because of evidence that they build up in the
environment and can cause harmful health effects. Products made before 1977 that may contain
PCBs include old fluorescent lighting fixtures, electrical devices containing PCB capacitors, and
old microscope and hydraulic oils (ATSDR, 2001).
The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for PCBs.
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PCBs are listed as Toxics Release Inventory (TRI) chemicals. TRI data indicate that total
off-site and on-site releases of PCBs for the period 1998-2006 ranged from approximately 1.2
million pounds to approximately 22 million pounds, with maximum releases occurring in 2003.
On-site releases were greater than off-site releases (USEPA, 2008).
38.3 Occurrence in Ambient Water
No National Water Quality Assessment (NAWQA) Program data are available from the
United States Geological Survey (USGS) on the occurrence of PCBs in ambient waters from the
Pesticide National Synthesis Project (Gilliom et a/., 2007) or the EPA Summary Analysis of
Cycle 1 data.
38.4 Occurrence in Drinking Water
PCBs is regulated as a synthetic organic chemical (SOC) in drinking water. All non-
purchased community water systems (CWSs) and non-transient non-community water systems
(NTNCWSs) are required to sample for SOCs. The maximum waiver period for SOCs is three
years, but this waiver can be renewed indefinitely. (Systems may receive a waiver at any time
without having collected an SOC sample. With a waiver, systems are not required to collect an
SOC sample.)
All CWSs and NTNCWSs without an SOC waiver must collect four consecutive
quarterly samples during the initial three-year compliance period. * If all four samples are non-
detections, then a system serving less than 3,300 persons may reduce to one sample during each
consecutive compliance period; a system serving more than 3,300 persons may reduce to two
quarterly samples within a 12-month period during a 3-year compliance period. If a chemical is
detected (but is less than the MCL), the system must take one sample per quarter until results are
below the MCL (minimum of two quarterly samples for ground water systems and four quarterly
samples for surface water systems). If all quarterly samples are below the MCL, the system may
return to annual sampling. If a chemical is detected at a level greater than the MCL, the system
(whether ground water or surface water) must take quarterly samples until four consecutive
quarters are below the MCL. If all quarterly samples are below the MCL, the system may return
to annual sampling.
The analysis of the occurrence of PCBs presented in the following section is based on
state compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and
most comprehensive compliance monitoring data set compiled by EPA's Drinking Water
Program to date.
Thirty-four of the Six-Year Review-ICR states provided occurrence data for PCBs. These
data consist of almost 67,216 analytical results from approximately 18,393 public water systems
(PWSs) during the period from 1998 to 2005. The number of sample results and systems vary by
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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state, although the state data sets have been reviewed and checked to ensure adequacy of
coverage and completeness.
38.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 38-1
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For PCBs, 0.158% of 18,393 systems reported
detections. Exhibit 38-2 lists the minimum, median, 90th percentile, and maximum PCB
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of PCBs, based on detections from all systems, is 0.1 |ig/L.
Exhibit 38-1: PCBs Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
53,365
16,249
45,009,798
Surface Water
13,851
2,144
79,104,410
Combined Ground &
Surface Water
67,216
18,393
124,114,208
Percent with Detections
Ground Water
0.071%
0.135%
6.179%
Surface Water
0.087%
0.326%
1.135%
Combined Ground &
Surface Water
0.074%
0.158%
2.964%
Exhibit 38-2: PCBs Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.1
Median
0.1
90tn
Percentile
0.6
Maximum
1.44
Surface Water
0.05
0.17
0.5
0.5
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Source Water Type
Detection Value (ug/L)
Minimum
Median
90tn
Percentile
Maximum
Combined Ground &
Surface Water
0.05
0.1
0.54
1.44
The following maps illustrate the geographic distribution of PCB occurrence in drinking
water. Exhibit 38-3 shows the states with systems with at least one detection and Exhibit 38-4
shows the states with systems with at least one detection greater than the MCL concentration.
Note that five states did not submit data for use in the Six-Year Review (Kansas2, Louisiana,
Mississippi, Pennsylvania, and Washington). The following states did submit Six-Year data for
most contaminants, but did not submit data for PCBs: Hawaii, Massachusetts, Michigan,
Minnesota, Missouri, Nebraska, New Hampshire, New Jersey, Oklahoma, Rhode Island, and
South Carolina.
The distribution of systems with detections of PCBs is geographically dispersed, and
detection rates were generally low. Three states reported detections in more than 1% of their
systems. Three states reported detections in 0.5% to 1% of systems. Twenty-three states reported
no detections. Two states reported detections greater than the MCL concentration of 0.5 |ig/L.
Exhibit 38-3: Percentage of Systems with at Least One PCB Detection,
by State
////% States with Waivers or Not Submitting
States with No Detections
• Less than 0.5% of Systems Detecting
Between 0.5% and 1% of Systems Detecting
^H More than 1% of Systems Detecting
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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Exhibit 38-4: Percentage of Systems with at Least One PCB Detection Greater
than the MCL Concentration (> 0.5 ug/L), by State
States with Waivers or Not Submitting
States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
| Between 0.1% and 0.5% of Systems with Detections > MCL
j More than 0.5% of Systems with Detections > MCL
Exhibit 38-5 presents the Stage 1 analysis of PCB occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 0.25 |ig/L and 0.5 |ig/L. Seven (0.038% of) systems, serving more than 721,000
persons, reported at least one detection greater than or equal to 0.25 |ig/L; and 2 (0.011% of)
systems, serving about 125,000 persons, reported at least one detection greater than 0.5 |ig/L.
Exhibit 38-5: PCBs Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 0.5 |jg/L
> 0.25 |jg/L
Number of
Systems
Exceeding
Threshold
2
4
Percent of
Systems
Exceeding
Threshold
0.012%
0.025%
Total Population-
Served by
Systems
Exceeding
Threshold
125,046
128,040
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.278%
0.284%
Surface
Water
> 0.5 |jg/L
> 0.25 |jg/L
0
3
0.000%
0.140%
0
593,206
0.000%
0.750%
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Source
Water
Type
Combined
Ground &
Surface
Water
Threshold
> 0.5 |jg/L
> 0.25 |jg/L
Number of
Systems
Exceeding
Threshold
2
7
Percent of
Systems
Exceeding
Threshold
0.011%
0.038%
Total Population-
Served by
Systems
Exceeding
Threshold
125,046
721,246
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.101%
0.581%
38.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2001. ToxFAQsfor
Poly'chlorinated Biphenyls (PCBs). February 2001. Available on the Internet at:
http://www.atsdr.cdc.gov/tfactsl7.html.
Gilliom, R.J., I.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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
United States Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
USEPA. 2008. TRI Explorer: Trends - Polychlorinated Biphenyls. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for
polychlorinated biphenyls.] Accessed March 8, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
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39 Combined Radium-226 and Radium-228
This chapter on radium (as combined radium-226 and -228) is part of a report that is
organized so that each chapter presents information on one specific contaminant. Chapter 1 of
this report, Introduction, presents background information on all sources of data used as well as
the analytical approach used to estimate contaminant occurrence in drinking water. This
contaminant chapter includes background information (such as regulatory history, general
chemical information, and environmental fate and behavior), use and environmental release
information, and combined radium occurrence estimates in ambient water and drinking water.
All drinking water occurrence estimates were based on data from the National Compliance
Monitoring Information Collection Request (ICR) Dataset for the Second Six-Year Review (the
"Six Year Review-ICR Dataset"). For detailed information regarding this dataset, data
management, data quality assessments, and the analytical approach used to generate all
contaminant occurrence estimates presented in this chapter, please refer to USEPA (2009).
39.1 Background
The United States Environmental Protection Agency (EPA) published an interim
Drinking Water Regulation for combined radium-226 and radium-228 on July 9, 1976 (41 FR
28402 (USEPA, 1976)). The Maximum Contaminant Level (MCL) established on that date was
5 pCi/L. In 2000, EPA published the final National Primary Drinking Water Regulations
(NPDWRs) for radionuclides. The MCL for combined radium remained the same; however,
monitoring requirements changed. In the original 1976 rule, radium-228 was only measured if
radium-226 was found at levels greater than 3 pCi/L. The revised Radionuclides rule in 2000
requires four consecutive quarterly samples for radium-228 and radium-226 unless samples have
been grandfathered. Furthermore, the 2000 rule set a Maximum Contaminant Level Goal
(MCLG) of zero for combined radium (USEPA, 2000). Under the revised rule, gross alpha
results may be substituted for radium-226 samples only if gross alpha samples are equal to or
less than 5 pCi/L. Radium-228 must still be monitored, and gross alpha samples may not be used
to substitute for radium-228. However, EPA is recommending that systems substitute gross alpha
for radium-226 only if previous gross alpha results are less than the gross alpha detection limit of
3 pCi/L, to avoid exceeding the combined radium MCL of 5 pCi/L.
According to USEPA (2007), radium forms when isotopes of uranium or thorium decay
in the environment. In the natural environment, radium occurs at very low levels in virtually all
rock, soil, water, plants, and animals. When uranium (or thorium) occurs in high levels in rock,
radium is often also found at high levels (USEPA, 2007).
Radium is a naturally radioactive, silvery-white metal when freshly cut. It blackens on
exposure to air. Purified radium and some radium compounds glow in the dark (luminesce). The
radiation emitted by radium can also cause certain materials to emit light. Metallic radium is
highly chemically reactive. It forms compounds that are very similar to barium compounds,
making separation of the two elements difficult (USEPA, 2007).
Radium-226, the most common isotope, originates from the decay of the plentiful
uranium-238. It is an alpha emitter, with accompanying gamma radiation, and has a half-life of
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about 1,600 years. Radium-228, found in the thorium-232 decay series, is principally a beta
emitter and has a half-life of 5.76 years. Radium decays to form isotopes of the radioactive gas
radon, which is not chemically reactive. Stable lead is the final product of this lengthy
radioactive decay series (USEPA, 2007).
39.2 Use, Production, and Releases
When radium was first discovered in the early 1900's, no one understood its danger.
People were fascinated with the mysterious properties of radium, especially the luminescence
produced when it is mixed with a phosphor. Industries sprang up to manufacture hundreds of
consumer products containing radium. Advertisements proclaimed its special powers and unique
effects in such products such as hair tonic, toothpaste, ointments, and elixirs. Mixtures of radium
salts and appropriate phosphors were widely used for clock dials and gauges before the risks of
radium exposure were understood (USEPA, 2007).
Most of its original uses have been halted for health and safety reasons. However, its
wide use in luminescent paints continued through World War II, because the soft glow of
radium's luminescence made aircraft dials, gauges and other instruments visible to their
operators at night. Radium was also an early radiation source for cancer treatment. Small seeds
were implanted in tumors to kill cancerous cells. Safer, more effective radiation sources, such as
cobalt-60 have mostly replaced it (USEPA, 2007).
Radium is a radiation source in some industrial radiography devices, a technology similar
to x-ray imaging used in industry to inspect for flaws in metal parts. When radium is mixed with
beryllium it becomes a good source of neutrons, useful in well logging devices and research.
Radium also has been added to the tips of lightning rods, improving their effectiveness by
ionizing the air around it (USEPA, 2007).
As radium is naturally occurring, data for production and release are not available.
39.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Combined radium in ambient surface
water and ground water are not available from the NAWQA Program. However, separate
radium-226 and radium-228 data are available.
39.3.1 EPA Summary Analysis of NAWQA Data
EPA, with the cooperation of the USGS, has performed a summary analysis of all Cycle
1 water monitoring data from all study units (1992-2001) for radium-226 and radium-228
separately. Detection frequencies were computed as the percentage of samples and sites with
detections (i.e., with at least one result equal to or greater than the reporting limit). Sample
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detections can be biased by frequent sampling in areas with high (or low) occurrence.
Calculating the percentage of sites with detections can reduce this bias.
The results of the EPA analysis for radium-226 are presented in Exhibit 39-1. Overall,
radium-226 was detected in 94.2% of samples and at 96.6% of sites. Radium-226 was detected
more frequently in ground water samples than in surface water samples, but it was detected in all
surface water sites. The median radium-226 concentration based on detections from all sites was
0.16 pCi/L. The 99th percentile concentration based on detections from all sites was 0.915 pCi/L.
Exhibit 39-1: EPA Summary Analysis of Radium-226 Data from NAWQA Study
Units, 1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
98
74
172
% Samples
with
Detections
95.9%
91.9%
94.2%
Number
of Sites
98
20
118
% Sites
with
Detections
95.9%
100.0%
96.6%
Concentration Values
(of detections, in pCi/L)
Minimum
0.0202
0.02
0.02
Median
0.286
0.055
0.16
95th
Percen-
tile
0.804
0.22
0.727
99th
Percen-
tile
1.11
0.35
0.915
Maximum
1.11
0.35
1.11
1. RLs (Reporting Limits) for radium-226 varied, but did not exceed 0.02 pCi/L
The results of the EPA analysis for radium-228 are presented in Exhibit 39-2. Radium-
228 was only sampled in ground water sites. It was detected in 82.6% of ground water samples
and at 82.9% of ground water sites. Radium-228 was not sampled in any surface water sites. The
median radium-228 concentration based on detections from ground water sites was 0.578 pCi/L.
The 99th percentile concentration based on detections from ground water sites was 2.53 pCi/L.
Exhibit 39-2: EPA Summary Analysis of Radium-228 Data from NAWQA Study
Units, 1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
459
0
459
% Samples
with
Detections
82.6%
82.6%
Number
of Sites
457
0
457
% Sites
with
Detections
82.9%
82.9%
Concentration Values
(of detections, in pCi/L)
Minimum
0.0244
0.0244
Median
0.578
0.578
95th
Percen-
tile
1.36
1.36
99th
Percen-
tile
2.53
2.53
Maximum
5.89
5.89
1. RLs (Reporting Limits) for radium-228 varied, but did not exceed 0.025 pCi/L.
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39.4 Occurrence in Drinking Water
Under the original Radionuclides rule (prior to December 8, 2003), all community water
systems (CWSs) must initially collect four consecutive quarterly samples for gross alpha
measurement. The gross alpha sample may be substituted for the required combined radium
analysis provided that the measured gross alpha particle activity does not exceed 5 pCi/L. If any
gross alpha result is greater than 5 pCi/L, the system must analyze the same or an equivalent
sample for radium-226. If radium-226 is greater than 3 pCi/L, the system must analyze for
radium-228.
Under the revised Radionuclides rule (after December 8, 2003), all CWSs must collect
four consecutive quarterly samples at all sampling points between December 8, 2003 and
December 31, 2007 unless data have been grandfathered. If the average of combined radium is
less than the detection limit, the system may reduce sampling to once every nine years.
(However, systems that only submit gross alpha particle activity analytical results and do not
sample for radium-226 individually may not be allowed to move to a reduced monitoring
frequency of one sample every nine years. The detection limit for gross alpha (3 pCi/L) does not
allow systems to confirm that radium-226 is below its respective detection limit as measured
individually (1 pCi/L)). If the average is equal to or greater than the detection limit but equal to
or less than /^ the MCL, the system may reduce sampling to once every six years. If the average
is greater than /^ the MCL (but is equal to or less than the MCL), the system may reduce
sampling to once every three years. If the average is greater than the MCL, the system must take
one sample each quarter until the annual average is below the MCL. Quarterly monitoring is also
triggered by one result that is more than four times the MCL or high enough to cause the running
annual average to exceed the MCL.
Gross alpha particle activity analytical results can still be substituted for radium-226, if
the gross alpha particle activity result is less than the detection limit of 3 pCi/L. In these
instances, one-half the detection limit (i.e., 1.5 pCi/L) is used for radium-226 and is added to the
radium-228 activity.
The analysis of combined radium occurrence presented in the following section is based
on state compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest
and most comprehensive compliance monitoring data set compiled by EPA's Drinking Water
Program to date.
Combined radium data were provided by 35 of the Six-Year Review-ICR states for the
original Radionuclides Rule (the period prior to December 8, 2003). (No data were received
from Arkansas, Delaware, Florida, Hawaii, Massachusetts, Michigan, Minnesota, New
Hampshire, Oklahoma, or Tennessee.) The combined radium data from the 35 states consist of
18,452 analytical results from 6,884 public water systems (PWSs) during the period from 1998
to December 8, 2003.
Combined radium data were provided by 33 of the Six-Year Review-ICR states for the
revised Radionuclides Rule (the period after December 8, 2003). (No data were received from
Arkansas, Florida, Georgia, Hawaii, Indiana, Massachusetts, Michigan, Minnesota, New
Hampshire, Oklahoma, Tennessee, or Texas.) The combined radium data from the 33 states
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consist of 18,050 analytical results from 3,893 PWSs during the period from December 9, 2003
to 2005. The number of sample results and systems vary by state, although the state data sets
have been reviewed and checked to ensure adequacy of coverage and completeness.
39.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 39-3
presents the number of samples and systems, as well as the population-served by the systems,
and the percentage of detections and the percentage of the population-served by the systems with
detections, for combined radium data collected under the original Radionuclides rule (before
December 8, 2003). Detections in systems provide a fundamental indication of national
occurrence, but are not representative of MCL violations. For combined radium (original rule),
62.188% of 6,884 systems reported detections. Exhibit 39-4 lists the minimum, median, 90th
percentile, and maximum combined radium (original rule) concentrations based on detections
from all systems in the Six-Year Review-ICR Dataset. The median concentration of combined
radium (original rule), based on detections from all systems, is 1.9 pCi/L.
Exhibit 39-3: Summary of Combined Radium Occurrence Data from the Six-Year
Review-ICR Dataset (data collected for original radionuclides rule)
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
15,920
6,190
15,006,355
Surface Water
2,532
694
32,416,085
Combined Ground &
Surface Water
18,452
6,884
47,422,440
Percent with Detections
Ground Water
67.079%
63.231%
79.462%
Surface Water
40.600%
52.882%
68.248%
Combined Ground &
Surface Water
63.446%
62.188%
71.796%
39-5
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 39-4: Combined Radium Summary Statistics
(data collected for original radionuclides rule)
Source Water Type
Ground Water
Detection Value (pCi/L)
Minimum
0.01
Median
2.1
90tn
Percent! le
9.3
Maximum
47
Surface Water
0.02
0.785
2.4
142
Combined Ground &
Surface Water
0.01
1.9
9
142
Exhibit 39-5 presents the number of samples and systems, as well as the population-
served by the systems, and the percentage of detections and the percentage of the population-
served by systems with detections, for combined radium data collected under the revised
Radionuclides rule (after December 8, 2003). For combined radium (revised rule), 69.972% of
3,893 systems reported detections. Exhibit 39-6 lists the minimum, median, 90th percentile, and
maximum combined radium (revised rule) concentrations based on detections from all systems
in the Six-Year Review-ICR Dataset. The median concentration of combined radium (revised
rule), based on detections from all systems, is 2 pCi/L.
Exhibit 39-5: Summary of Combined Radium Occurrence Data from the Six-Year
Review-ICR Dataset (data collected for revised radionuclides rule)
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
15,895
3,472
11,709,681
Surface Water
2,155
421
29,716,756
Combined Ground &
Surface Water
18,050
3,893
41,426,437
Percent with Detections
Ground Water
67.732%
71.083%
68.876%
Surface Water
43.016%
60.808%
51.978%
Combined Ground &
Surface Water
64.781%
69.972%
56.754%
39-6
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 39-6: Combined Radium Summary Statistics
(data collected for revised radionuclides rule)
Source Water Type
Ground Water
Detection Value (pCi/L)
Minimum
0.0008
Median
2.3
90tn
Percentile
8.1
Maximum
56.66
Surface Water
0.01
1
3
27.789
Combined Ground &
Surface Water
0.0008
2
7.8
56.66
The following maps illustrate the geographic distribution of combined radium occurrence
in drinking water. Exhibits 39-7 and 39-8 show the states with systems with at least one
detection for the original and revised radionuclide rules, respectively. Exhibits 39-9 and 39-10
show the states with systems with at least one detection greater than the MCL concentration for
the original and revised radionuclide rules, respectively. Note that five states did not submit any
data for use in the Six-Year Review (Kansas1, Louisiana, Mississippi, Pennsylvania, and
Washington).
The distribution of systems with detections of combined radium is geographically
dispersed. Based on the data collected for the original radionuclides rule, 13 states had more than
90% of systems reporting detections. Based on the data collected for the revised radionuclides
rule, 11 states had more than 90% of systems reporting detections. In 14 states, more than 10%
of systems reported at least one detection greater than the MCL concentration of 5 pCi/L (based
on the data collected for the original radionuclides rule. In 11 states, more than 10% of systems
reported at least one detection greater than the MCL concentration of 5 pCi/L (based on the data
collected for the revised radionuclides rule.
1 Kansas submitted data after the data management and analyses had been conducted; data from Kansas are not
included in the analyses.
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Exhibit 39-7: Percentage of Systems with at Least One Combined Radium
Detection, by State (data collected for original radionuclides rule)
\///, States with Waivers or Not Submitting
States with No Detections
Less than or Equal to 50% of Systems Detecting
H Between 50% and 90% of Systems Detecting
B More than 90% of Systems Detecting
Exhibit 39-8: Percentage of Systems with at Least One Combined Radium
Detection, by State (data collected for revised radionuclides rule)
y///. States with Waivers or Not Submitting
States with No Detections
Less than or Equal to 50% of Systems Detecting
HI Between 50% and 90% of Systems Detecting
^B More than 90% of Systems Detecting
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 39-9: Percentage of Systems with at Least One Combined Radium
Detection Greater than the MCL Concentration (> 5 pCi/L), by State (data collected
for original radionuclides rule)
-. States with Waivers or Not Submitting
States with No Detections > MCL
Less than 5% of Systems with Detections > MCL
Between 5% and 1 0% of Systems with Detections > MCL
More than 10% of Systems with Detections > MCL
Exhibit 39-10: Percentage of Systems with at Least One Combined Radium
Detection Greater than the MCL Concentration (> 5 pCi/L), by State (data collected
for revised radionuclides rule)
<%%• States with Waivers or Not Submitting
States with No Detections > MCL
Less than 5% of Systems with Detections > MCL
| Between 5% and 10% of Systems with Detections > MCL
| More than 10% of Systems with Detections > MCL
Exhibit 39-11 presents the Stage 1 analysis for the original Radionuclides Rule. These
exhibits summarize combined radium occurrence in drinking water from systems and
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populations served by those systems in the Six-Year Review-ICR Dataset relative to two
thresholds: 2.5 pCi/L and 5 pCi/L. For systems sampling under the original Radionuclides Rule,
a total of 1,222 (17.751% of) PWSs, serving almost 9.2 million persons, reported at least one
detection greater than or equal to 2.5 pCi/L; and 502 (7.292% of) PWSs, serving almost 4.6
million persons, reported at least one detection greater than 5 pCi/L
Exhibit 39-11: Combined Radium Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
(data collected under the original radionuclides rule)
Source
Water
Type
Ground
Water
Threshold
> 5 pCi/L
>2.5pCi/L
Number of
Systems
Exceeding
Threshold
488
1,185
Percent of
Systems
Exceeding
Threshold
7.884%
19.144%
Total Population-
Served by
Systems
Exceeding
Threshold
2,143,386
4,652,946
Percent of
Population-Served
by Systems
Exceeding
Threshold
14.283%
31.007%
Surface
Water
> 5 pCi/L
>2.5pCi/L
14
37
2.017%
5.331%
2,418,615
4,510,400
7.461%
13.914%
Combined
Ground &
Surface
Water
> 5 pCi/L
>2.5pCi/L
502
1,222
7.292%
17.751%
4,562,001
9,163,346
9.620%
19.323%
Exhibit 39-12 presents the Stage 1 analysis for the systems sampling under the revised
Radionuclides Rule. For systems sampling under the revised Radionuclides Rule, a total of 1,055
(27.100% of) PWSs, serving almost 7.4 million persons, reported at least one detection greater
than or equal to 2.5 pCi/L; and 446 (11.456% of) PWSs, serving more than 3.8 million persons,
reported at least one detection greater than 5 pCi/L.
Exhibit 39-12: Combined Radium Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
(data collected under the revised radionuclides rule)
Source
Water
Type
Ground
Water
Threshold
> 5 pCi/L
>2.5pCi/L
Number of
Systems
Exceeding
Threshold
432
1,008
Percent of
Systems
Exceeding
Threshold
12.442%
29.032%
Total Population
Served by
Systems
Exceeding
Threshold
2,438,570
4,280,726
Percent of
Population Served
by Systems
Exceeding
Threshold
20.825%
36.557%
39-10
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source
Water
Type
Surface
Water
Threshold
> 5 pCi/L
>2.5pCi/L
Number of
Systems
Exceeding
Threshold
14
47
Percent of
Systems
Exceeding
Threshold
3.325%
11.164%
Total Population
Served by
Systems
Exceeding
Threshold
1,372,884
3,100,164
Percent of
Population Served
by Systems
Exceeding
Threshold
4.620%
10.432%
Combined
Ground &
Surface
Water
> 5 pCi/L
>2.5pCi/L
446
1,055
1 1 .456%
27.100%
3,811,454
7,380,890
9.201%
17.817%
39.5 References
United States Environmental Protection Agency (USEPA). 1976. Title 40—Protection of
Environment. Chapter 1—Environmental Protection Agency. Part 141—Interim Primary
Drinking Water Regulations. Promulgation of Regulations on Radionuclides. Federal Register,
Vol. 41, No. 133, p. 28402, July 9, 1976.
USEPA. 2000. National Primary Drinking Water Regulations; Radionuclides; Final Rule.
Federal Register. Vol. 65, No. 236. p. 76707, December 7, 2000.
http ://www. epa. gov/fedrgstr/EPA-WATER/2000/December/Dav-07/w3 0421 .htm
USEPA. 2007. Radiation Protection: Radium. Last modified November 13, 2007. Available on
the Internet at: http://www.epa.gov/radiation/radionuclides/radium.html. Accessed March 18,
2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
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40 Selenium
This chapter on selenium is part of a report that is organized so that each chapter presents
information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and selenium
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
40.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for selenium on January 30, 1991 (56
FR 3526 (USEPA, 199la)). The NPDWR established a maximum contaminant level goal
(MCLG) and a maximum contaminant level (MCL) of 0.05 mg/L. EPA based the MCLG on a
maximum safe intake1 of 0.4 mg/person/day and a cancer classification of D, not classifiable as
to human carcinogenicity.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2003),
selenium is a naturally occurring element that is distributed widely in nature in most rocks and
soils. In its pure form, selenium exists as metallic gray to black hexagonal crystals, but in nature
it is usually combined with sulfide or with silver, copper, lead, and nickel minerals. In the
environment, the oxidized form, which occurs in alkaline soils, is more toxic. Plants can take it
up, and it may accumulate up the food chain (ATSDR, 2003).
40.2 Use, Production, and Releases
Most processed selenium is used in the electronics industry. Selenium is also used: as a
nutritional supplement; in the glass industry; as a component of pigments in plastics, paints,
enamels, inks, and rubber; in the preparation of pharmaceuticals; as a nutritional feed additive for
poultry and livestock; in pesticide formulations; in rubber production; as an ingredient in
antidandruff shampoos; and as a constituent of fungicides. Radioactive selenium is used in
diagnostic medicine (ATSDR, 2003).
1 The 0.4 mg/day safe level was based on data (Yang et al, 1989a and 1989b) that extrapolated from blood selenium
levels to estimated dietary intake in the studied population. As described in USEPA (1991a), EPA partially
considered selenium's status as a nutrient and did not use the typical procedure for deriving the MCLG. Hence, there
is no specific reference to an RfD for selenium in the 1991 FR notice. After the publication of the regulation, IRIS
(USEPA, 1991b) posted an RfD of 0.005 mg/kg-day for selenium using the same data that are the basis of the
regulation.
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The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for selenium.
Selenium and selenium compounds are listed as Toxics Release Inventory (TRI)
chemicals. TRI data indicate that total off-site and on-site releases of selenium for the period
1998-2006 ranged from approximately 267,000 pounds to approximately 4.4 million pounds,
with maximum releases in 2001 and 2006. On-site releases were greater than off-site releases
(USEPA, 2008a). Total selenium compound releases ranged from approximately 2.5 million
pounds to approximately 8.5 million pounds, with a general decrease over time. Amounts
released on-site were greater than amounts released off-site (USEPA, 2008b).
40.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of selenium in
ambient water are available from the NAWQA program.
40.3.1 EPA Summary Analysis of NAWQA Data
EPA, with the cooperation of the USGS, has performed a summary analysis of all Cycle
1 water monitoring data from all study units (1992-2001) for selenium. Detection frequencies
were computed as the percentage of samples and sites with detections (i.e., with at least one
result equal to or greater than the reporting limit). Sample detections can be biased by frequent
sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 40-1. Overall, selenium was
detected in 27.0% of samples and at 26.7% of sites. The median concentration based on
detections from all sites was 2 jig/L (0.002 mg/L). The 99th percentile concentration based on
detections from all sites was about 48 jig/L (0.048 mg/L).
Exhibit 40-1: EPA Summary Analysis of Selenium Data from NAWQA Study Units,
1992-2001
ground
water
surface
water
Detection Frequency
(detections are results > RL1)
Number
of
Samples
3,464
3,269
% Samples
with
Detections
25.8%
28.2%
Number
of Sites
3,065
462
% Sites
with
Detections
27.2%
23.4%
Concentration Values
(of detections, in ug/L)
Minimum
0.17
0.201
Median
2
2.155
95th
Percen-
tile
14.11
17
99th
Percen-
tile
37.97
78
Maximum
92.461
150
40-2
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
6,733
% Samples
with
Detections
27.0%
Number
of Sites
3,527
% Sites
with
Detections
26.7%
Concentration Values
(of detections, in ug/L)
Minimum
0.17
Median
2
95th
Percen-
tile
16.28
99th
Percen-
tile
47.564
Maximum
150
1. RLs (Reporting Umits) for selenium varied, but did not exceed 0.2 pg/L
40.4 Occurrence in Drinking Water
Selenium is regulated as an inorganic chemical (IOC) in drinking water. All community
water systems (CWSs) and non-transient non-community water systems (NTNCWSs) are
required to sample for the IOCs.2 The maximum waiver period for lOCs is nine years.
Ground water systems must sample once during the initial three-year compliance period.
After three compliance periods without a detection, a ground water system may be granted a
nine-year waiver. Surface water systems must sample annually during the initial three-year
compliance period. After three annual samples without a detection, a surface water system may
be granted a nine-year waiver. If the results are greater than the MCL, the public water system
(PWS) must take one sample per quarter until results are below the MCL (minimum of two
quarterly samples for ground water systems and four quarterly samples for surface water
systems).3 If all quarterly samples are below the MCL, the system may continue at initial
monitoring indefinitely until the state or EPA establishes an alternate schedule.
The analysis of selenium occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
All of the Six-Year Review-ICR states provided occurrence data for selenium. These data
consist of 181,684 analytical results from 48,925 systems during the period from 1998 to 2005.
The number of sample results and systems vary by state, although the state data sets have been
reviewed and checked to ensure adequacy of coverage and completeness.
40.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 40-2
presents the number of samples and systems, as well as the population-served by the systems,
2 Nitrate and nitrite have their own monitoring requirements. See the nitrate and nitrite chapters for details of those
requirements.
3 All new systems or systems using a new water source that began operation after January 22, 2004 must
demonstrate compliance with the MCL within a period of time specified by the State. The system must also comply
with the initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with
the MCL.
40-3
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
and the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For selenium, 17.284% of 48,925 systems reported
detections. Exhibit 40-3 lists the minimum, median, 90th percentile, and maximum selenium
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of selenium, based on detections from all systems, is 0.003 mg/L.
Exhibit 40-2: Selenium Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
141,387
44,924
85,462,006
Surface Water
40,297
4,001
144,401,405
Combined Ground &
Surface Water
181,684
48,925
229,863,411
Percent with Detections
Ground Water
12.790%
16.715%
34.217%
Surface Water
10.016%
23.669%
38.724%
Combined Ground &
Surface Water
12.175%
17.284%
37.048%
Exhibit 40-3: Selenium Summary Statistics
Source Water Type
Ground Water
Detection Value (mg/L)
Minimum
0.000076
Median
0.003
90tn
Percentile
0.01
Maximum
0.49
Surface Water
0.00006
0.003
0.0087
0.2
Combined Ground &
Surface Water
0.00006
0.003
0.01
0.49
The following maps illustrate the geographic distribution of selenium occurrence in
drinking water. Exhibit 40-4 shows the states with systems with at least one detection and
Exhibit 40-5 shows the states with systems with at least one detection greater than the MCL
40-4
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concentration. Note that five states did not submit data for use in the Six-Year Review (Kansas ,
Louisiana, Mississippi, Pennsylvania, and Washington).
Detection rates were high for selenium. In four states, more than 50% of systems detected
selenium. In 18 states, between 10% and 50% of systems reported detections. Twenty-eight
states reported no detections of selenium greater than the MCL concentration. For five states,
more than 0.5% of systems reported at least one detection greater than the MCL concentration of
0.05 mg/L.
Exhibit 40-4: Percentage of Systems with at Least One Selenium
Detection, by State
; States Not Submitting Any Data
_ States with No Detections
^J Less than 10% of Systems Detecting
BH Between 10% and 50% of Systems Detecting
BH More than 50% of Systems Detecting
Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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Exhibit 40-5: Percentage of Systems with at Least One Selenium Detection
Greater than the MCL Concentration (> 0.05 mg/L), by State
Estates Not Submitting Any Data
States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
Between 0.1% and 0.5% of Systems with Detections > MCL
H More than 0.5% of Systems with Detections > MCL
Exhibit 40-6 presents the Stage 1 analysis of selenium occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 0.025 mg/L and 0.05 mg/L. A total of 280 (0.572% of) systems, serving almost
4.8 million persons, reported at least one detection greater than or equal to 0.025 mg/L; and 65
(0.133% of) systems, serving almost 225,000 persons, reported at least one detection greater than
0.05 mg/L.
Exhibit 40-6: Selenium Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 0.05 mg/L
> 0.025 mg/L
Number of
Systems
Exceeding
Threshold
63
252
Percent of
Systems
Exceeding
Threshold
0.140%
0.561%
Total Population-
Served by
Systems
Exceeding
Threshold
123,164
750,440
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.144%
0.878%
Surface
Water
> 0.05 mg/L
> 0.025 mg/L
2
28
0.050%
0.700%
101,652
4,034,609
0.070%
2.794%
40-6
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source
Water
Type
Combined
Ground &
Surface
Water
Threshold
> 0.05 mg/L
> 0.025 mg/L
Number of
Systems
Exceeding
Threshold
65
280
Percent of
Systems
Exceeding
Threshold
0.133%
0.572%
Total Population-
Served by
Systems
Exceeding
Threshold
224,816
4,785,049
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.098%
2.082%
40.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2003. ToxFAQsfor Selenium.
September 2003. Available on the Internet at: http://www.atsdr.cdc.gov/tfacts92.html.
United States Environmental Protection Agency (USEPA). 199la. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
USEPA. 1991b. Integrated Risk Information System (IRIS) - Selenium. Oral RfD. Available on
the Internet at: http://www.epa.gov/iris/subst/0472.htm
USEPA. 2008a. TRI Explorer: Trends - Selenium. Released February 21, 2008. Available on the
Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for selenium.] Accessed March 6,
2008.
USEPA. 2008b. TRI Explorer: Trends - Selenium Compounds. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for selenium
compounds.] Accessed March 6, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
Yang, G., R. Zhou, S. Yin, et al. 1989a. Studies of safe maximal daily dietary selenium intake in
a seleniferous area in China. I. Selenium intake and tissue levels of the inhabitants. Journal of
Trace Elements and Electrolytes in Health and Disease. 3(2):77-87.
Yang, G., S. Yin, R. Zhou, et al. 1989b. Studies of safe maximal daily dietary Se-intake in a
seleniferous area in China. U. Relation between Se- intake and the manifestation of clinical signs
and certain biochemical alterations in blood and urine. Journal of Trace Elements and
Electrolytes in Health and Disease. 3 (2): 123 -13 0.
40-7
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41 Simazine
This chapter on simazine is part of a report that is organized so that each chapter presents
information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and simazine
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
41.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for simazine on July 17, 1992 (57 FR
31776 (USEPA, 1992)). The NPDWR established a maximum contaminant level goal (MCLG)
and a maximum contaminant level (MCL) of 4 |ig/L. The Agency based the MCLG on a
reference dose (RfD) of 5 jig/kg-day (0.005 mg/kg-day) and a cancer classification of C, possible
human carcinogen.
According to the Extension Toxicology Network (EXTOXNET, 1996), simazine
(CyH^ClNs), a selective triazine herbicide, is an organic white solid. It acts by inhibiting
photosynthesis. The ability of simazine to bind to soil is highly dependent on soil type; it will
bind more strongly to soils high in clay and organic matter. Persistence in soils is also highly
variable, and there is a wide range of reported half lives. Persistence of simazine in water is
similarly variable. Biodegradation is believed to be slow and depends on the level of algae or the
degree of weed infestation (EXTOXNET, 1996).
41.2 Use, Production, and Releases
Simazine is a pre-emergence herbicide used for control of broad-leaved and grassy weeds
in field, berry fruit, nuts, vegetable and ornamental crops, turfgrass, orchards, and vineyards. At
higher rates, it is used for nonselective weed control in industrial areas. Before 1992, simazine
was used to control submerged weeds and algae in large aquariums, farm ponds, fish hatcheries,
swimming pools, ornamental ponds, and cooling towers (EXTOXNET, 1996).
Exhibit 41-1, compiled by the United States Geological Survey (USGS, 2007), shows the
geographic distribution of estimated average annual simazine use in the United States from 1999
through 2004. A breakdown of use by crop is also included. The map was created by the USGS
using state-level data sets on pesticide use rates from 1999-2004 compiled by the CropLife
Foundation, at the Crop Protection Research Institute, combined with county-level data on
harvested crop acreage obtained from the 2002 Census of Agriculture. Due to the nature of the
41-1
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data sources, non-agricultural uses are not reflected here, and variations in use at the county-
level are also not well represented (Thelin and Gianessi, 2000). The USGS (2007) estimates that
almost 4.7 million pounds of simazine active ingredient were used on average each year between
1999 and 2004.
Exhibit 41-1: Estimated Annual Agricultural Use for Simazine (c. 2002)
SIMAZINE - herbicide
2002 estimated annual agricultural use
Average annual use of
active ingredient
(pounds per square mile of agricultural
land in county)
I I no estimated use
D 0.001 to 0.025
D 0.026 to 0.167
D 0.168 to 0.822
D 0.823 to 3.598
• >= 3.599
Crops
corn
citrus fruit
grapes
apples
peaches
almonds
pecans
walnuts
cherries
sod harvested
Total
pounds applied
2944455
881117
330508
141480
61655
58109
55062
40997
25739
24042
Percent
national use
62.86
18.81
7.06
3.02
1.32
1.24
1.18
0.88
0.55
0.51
Source: USGS, 2007
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 41-2 presents the production of simazine in the United States from 1986 to 2002.
Note that the production of simazine in the United States increased from 1986 to 1994 but has
not been reported in the Chemical Update System thereafter.
Exhibit 41-2: Production of Simazine in the United States
Inventory Update Year
1986 Range
Production Volume
> 1 million - 10 million pounds
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Inventory Update Year
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
> 1 million - 10 million pounds
> 10 million - 50 million pounds
No reports
No reports
Source: USEPA, 2003
Simazine is listed as a Toxics Release Inventory (TRI) chemical. TRI data indicate that
total off-site and on-site releases of simazine for the period 1998-2006 ranged from about 2,700
pounds to about 37,000 pounds, with the maximum releases occurring in 2004 (USEPA, 2008).
41.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The USGS National
Water Quality Assessment (NAWQA) program is a national-scale assessment of the occurrence
of contaminants in ambient surface and ground water. Contaminant occurrence in ambient water
provides information on the potential for contaminants to adversely affect drinking water
supplies. Data on the occurrence of simazine in ambient water are available from the NAWQA
program.
41.3.1 NA WQA Pesticide National Synthesis Project
The NAWQA Pesticide National Synthesis Project is a national-scale assessment of the
occurrence and behavior of pesticides in streams and ground water of the United States and the
potential for pesticides to adversely affect drinking water supplies or aquatic ecosystems. Under
the National Synthesis Project, the USGS monitored simazine between 1992 and 2001 in streams
and wells across the country (Gilliom et a/., 2007). The maximum long-term method detection
limit for simazine was 0.006 |ig/L.
In NAWQA stream samples (Exhibit 41-3), simazine was found at frequencies ranging
from 23.92% of samples in undeveloped areas to 58.16% in agricultural settings, 63.42% of
samples in mixed land use settings, and 64.72% in urban areas. The 95th percentile concentration
was 0.013 |ig/L in undeveloped areas, 0.159 |ig/L in mixed land use settings, 0.175 |ig/L in
agricultural settings, and 0.340 |ig/L in urban areas. The highest concentration, 9.030 |ig/L, was
found at an urban site.
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Exhibit 41-3: USGS National Synthesis Summary of NAWQA Monitoring of
Simazine in Streams, 1992-2001
Land Use
Type
Agricultural
Mixed
Undeveloped
Urban
No. of Samples
(No. of Sites)
2,009(83)
1,385(65)
144(8)
812(30)
Detection
Frequency
58.16%
63.42%
23.92%
64.72%
50tn Percent! le
(Median)
Concentration
(in ug/L)
0.006
0.007
ND1
0.008
95th Percentile
Concentration
(in ug/L)
0.175
0.159
0.013
0.340
Maximum
Concentration
(in ug/L)
5.760
1.620
0.140
9.030
Source: Gilliom et a/., 2007
1. ND = not detected (Concentration is less than the maximum long term method detection limit and is expected to
be less than any higher percentile concentration shown in the table)
In ground water NAWQA samples (Exhibit 41-4), simazine was found at frequencies
ranging from 2.94% of samples in undeveloped areas to 5.75% in mixed land use settings,
18.22% of samples in urban areas, and 18.38% of samples in agricultural settings. The 95th
percentile concentration was less than the maximum method detection limit in undeveloped
settings, 0.0028 |ig/L in mixed land use settings, 0.0273 |ig/L in agricultural settings, and 0.034
Hg/L in urban areas. The highest concentration, 1.38 |ig/L, was found in an agricultural setting.
Exhibit 41-4: USGS National Synthesis Summary of NAWQA Monitoring of
Simazine in Ground Water, 1992-2001
Land Use Type
Agricultural
Mixed
Undeveloped
Urban
Number
of Wells
1,404
2,732
34
856
Detection
Frequency
18.38%
5.75%
2.94%
18.22%
50tn Percentile
(Median)
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
95th Percentile
Concentration
(in ug/L)
0.0273
0.0028
ND1
0.034
Maximum
Concentration
(in ug/L)
1.38
0.315
0.0031
1.1
Source: Gilliom et a/., 2007
1. ND = not detected (Concentration is less than the maximum long term method detection limit and is expected to
be less than any higher percentile concentration shown in the table)
41.3.2 EPA Summary Analysis of NAWQA Data
Whereas the NAWQA program often uses the most representative data for a site to
calculate summary statistics, EPA, with the cooperation of the USGS, has performed a summary
analysis of all Cycle 1 water monitoring data from all study units (1992-2001) for simazine.
Detection frequencies were computed as the percentage of samples and sites with detections (i.e.,
with at least one result equal to or greater than the reporting limit). Sample detections can be
biased by frequent sampling in areas with high (or low) occurrence. Calculating the percentage of
sites with detections can reduce this bias.
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The results of the EPA analysis are presented in Exhibit 41-5. Overall, simazine was
detected in 47.2% of samples and at 26.1% of sites. Simazine was detected more frequently in
surface water than in ground water. The median concentration based on detections from all sites
was 0.0218 |ig/L. The 99th percentile concentration based on detections from all sites was 2.67
Exhibit 41-5: EPA Summary Analysis of Simazine Data from NAWQA Study Units,
1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
6,107
15,637
21,744
% Samples
with
Detections
13.9%
60.3%
47.2%
Number
of Sites
5,216
1,949
7,165
% Sites
with
Detections
13.5%
60.0%
26.1%
Concentration Values
(of detections, in ug/L)
Minimum
0.0009
0.0003
0.0003
Median
0.0112
0.023
0.0218
95th
Percen-
tile
0.194
0.513
0.49
99th
Percen-
tile
0.605
3.04
2.67
Maximum
1.38
38.8
38.8
1. RLs (Reporting Limits) for simazine varied, but did not exceed 0.0009 ug/L. Note that because this EPA analysis
involves more data points than the USGS analyses presented above, a direct comparison is not possible.
41.4 Occurrence in Drinking Water
Simazine is regulated as a synthetic organic chemical (SOC) in drinking water. All non-
purchased community water systems (CWSs) and non-transient non-community water systems
(NTNCWSs) are required to sample for SOCs. The maximum waiver period for SOCs is three
years, but this waiver can be renewed indefinitely. (Systems may receive a waiver at any time
without having collected an SOC sample. With a waiver, systems are not required to collect an
SOC sample.)
All CWSs and NTNCWSs without an SOC waiver must collect four consecutive
quarterly samples during the initial three-year compliance period.l If all four samples are non-
detections, then a system serving less than 3,300 persons may reduce to one sample during each
consecutive compliance period; a system serving more than 3,300 persons may reduce to two
quarterly samples within a 12-month period during a 3-year compliance period. If a chemical is
detected (but is less than the MCL), the system must take one sample per quarter until results are
below the MCL (minimum of two quarterly samples for ground water systems and four quarterly
samples for surface water systems). If all quarterly samples are below the MCL, the system may
return to annual sampling. If a chemical is detected at a level greater than the MCL, the system
(whether ground water or surface water) must take quarterly samples until four consecutive
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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quarters are below the MCL. If all quarterly samples are below the MCL, the system may return
to annual sampling.
The analysis of simazine occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
Forty-four of the Six-Year Review-ICR states provided occurrence data for simazine.
(There were no simazine data from Oklahoma.) These data consist of 158,256 analytical results
from 36,830 public water systems (PWSs) during the period from 1998 to 2005. The number of
sample results and systems vary by state, although the state data sets have been reviewed and
checked to ensure adequacy of coverage and completeness.
41.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 41-6
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For simazine, 0.725% of 36,830 systems reported
detections. Exhibit 41-7 lists the minimum, median, 90th percentile, and maximum simazine
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of simazine, based on detections from all systems, is 0.27 |ig/L.
Exhibit 41-6: Simazine Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
119,755
33,478
73,412,761
Surface Water
38,501
3,352
123,573,744
Combined Ground &
Surface Water
158,256
36,830
196,986,505
Percent with Detections
Ground Water
0.106%
0.221%
3.869%
Surface Water
2.639%
5.758%
14.665%
Combined Ground &
Surface Water
0.722%
0.725%
10.641%
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Exhibit 41-7: Simazine Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.01
Median
0.3
90tn
Percentile
2.46
Maximum
6.2
Surface Water
0.01
0.26
1
12.4
Combined Ground &
Surface Water
0.01
0.27
1.1
12.4
The following maps illustrate the geographic distribution of simazine occurrence in
drinking water. Exhibit 41-8 shows the states with systems with at least one detection and
Exhibit 41-9 shows the states with systems with at least one detection greater than the MCL
concentration. Note that five states did not submit data for use in the Six-Year Review (Kansas2,
Louisiana, Mississippi, Pennsylvania, and Washington). Oklahoma submitted Six-Year data for
most contaminants; however, there is a statewide waiver for simazine in Oklahoma so no
simazine data were available from that state.
The distribution of systems with detections of simazine is geographically dispersed and
detection rates were generally low. Nine states reported detections in more than 1% of their
systems. In eight states, between 0.5% and 1% of systems reported detections. Fifteen states did
not report detections. Eight states reported detections greater than the MCL concentration of 4
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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Exhibit 41-8: Percentage of Systems with at Least One Simazine Detection,
by State
Estates with Waivers or Not Submitting
States with No Detections
Less than 0.5% of Systems Detecting
Between 0.5% and 1% of Systems Detecting
More than 1% of Systems Detecting
Exhibit 41-9: Percentage of Systems with at Least One Simazine Detection
Greater than the MCL Concentration (> 4 ^giL], by State
States with Waivers or Not Submitting
States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
| Between 0.1% and 0.5% of Systems with Detections > MCL
| More than 0.5% of Systems with Detections > MCL
Exhibit 41-10 presents the Stage 1 analysis of simazine occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 2 |ig/L and 4 |ig/L. A total of 34 (0.092% of) systems, serving about 729,000
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persons, reported at least one detection greater than or equal to 2 |ig/L; and 16 (0.043% of)
systems, serving more than 123,000 persons, reported at least one detection greater than 4 |ig/L.
Exhibit 41-10: Simazine Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 4 pg/L
> 2 |jg/L
Number of
Systems
Exceeding
Threshold
4
5
Percent of
Systems
Exceeding
Threshold
0.012%
0.015%
Total Population-
Served by
Systems
Exceeding
Threshold
2,408
3,108
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.003%
0.004%
Surface
Water
> 4 pg/L
> 2 |jg/L
12
29
0.358%
0.865%
120,751
725,922
0.098%
0.587%
Combined
Ground &
Surface
Water
> 4 |jg/L
> 2 |jg/L
16
34
0.043%
0.092%
123,159
729,030
0.063%
0.370%
41.5 References
Extension Toxicology Network (EXTOXNET). 1996. EXTOXNET Pesticide Information
Profiles-Simazine. Last modified June 1996. Available on the Internet at:
http://extoxnet.orst.edu/pips/simazine.htm. Accessed July 6, 2008.
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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
Thelin, G.P. and L.P. Gianessi. 2000. Method for Estimating Pesticide Use for County Areas of
the Conterminous United States. U.S. Geological Survey Open-File Report 00-250, 62 p.
Available on the Internet at: http://ca.water.usgs.gov/pnsp/rep/ofr00250/ofr00250.pdf
United States Environmental Protection Agency (USEPA). 1992. Drinking Water; National
Primary Drinking Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals;
National Primary Drinking Water Regulations Implementation; Final Rule. Federal Register.
Vol. 57, No. 138. p. 31776, July 17, 1992.
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USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - Simazine. Last modified September 10, 2007. Available on the Internet at:
http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for simazine.] Accessed February
21,2008.
USEPA. 2008. TRI Explorer: Trends - Simazine. Released February 21, 2008. Available on the
Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for simazine.] Accessed March 6,
2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
United States Geological Survey (USGS). 2007. 2002 Pesticide Use Maps. Available on the
Internet at:
http://water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=02&map=ml981.
Accessed March 6, 2008.
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42 Styrene
This chapter on styrene is part of a report that is organized so that each chapter presents
information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and styrene
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
42.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for styrene on January 30, 1991 (56 FR
3526 (USEPA, 1991)). The NPDWR established a maximum contaminant level goal (MCLG)
and a maximum contaminant level (MCL) of 100 |ig/L. The Agency based the MCLG on a
reference dose (RfD) of 200 jig/kg-day (0.2 mg/kg-day) and a cancer classification of C, possible
human carcinogen.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2007),
styrene is a colorless liquid that evaporates easily and has a sweet smell. It often contains other
chemicals that give it a sharp, unpleasant smell. Low levels of styrene can occur naturally in a
variety of foods such as fruits, vegetables, nuts, beverages, and meats. In addition, small amounts
of styrene can be transferred to food from styrene-based packaging material. Styrene evaporates
from shallow soils and surface water and is quickly broken down in the air. Styrene that remains
in soil or water may be broken down by bacteria or other microorganisms, thereby acting to
minimize ground water concentrations. It is not expected to build up in animals (ATSDR, 2007).
42.2 Use, Production, and Releases
Styrene is widely used to make plastics and rubber. Most products contain styrene linked
together in a long chain (polystyrene) as well as unlinked styrene. Products containing styrene
include insulation, fiberglass, plastic pipes, automobile parts, shoes, drinking cups and other food
containers, and carpet backing (ATSDR, 2007).
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 42-1 presents the production of styrene in the United States from 1986 to 2002.
Note that the production of styrene in the United States has remained constant since 1986.
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Exhibit 42-1: Production of Styrene in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
> 1 billion pounds
> 1 billion pounds
> 1 billion pounds
> 1 billion pounds
> 1 billion pounds
Source: USEPA, 2003
Styrene is listed as a Toxics Release Inventory (TRI) chemical. TRI data indicate that
total off-site and on-site releases of styrene for the period 1998-2006 ranged from approximately
50 million pounds to approximately 62 million pounds, with a general decrease over time. On-
site releases were greater than off-site releases (USEPA, 2008).
42.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of styrene in
ambient water are available from the NAWQA program.
42.3.1 EPA Summary Analysis of NAWQA Data
EPA, with the cooperation of the USGS, has performed a summary analysis of all Cycle 1
water monitoring data from all study units (1992-2001) for styrene. Detection frequencies were
computed as the percentage of samples and sites with detections (i.e., with at least one result
equal to or greater than the reporting limit). Sample detections can be biased by frequent
sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 42-2. Overall, styrene was
detected in 3.5% of samples and at 2.2% of sites. Styrene was detected more frequently in surface
water than in ground water. The median concentration based on detections from all sites was
0.0116 ng/L. The 99th percentile concentration based on detections from all sites was 0.3 |ig/L.
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Exhibit 42-2: EPA Summary Analysis of Styrene Data from NAWQA Study Units,
1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
4,639
1,401
6,040
% Samples
with
Detections
1.1%
1 1 .4%
3.5%
Number
of Sites
4,139
182
4,321
% Sites
with
Detections
1.2%
23.1%
2.2%
Concentration Values
(of detections, in ug/L)
Minimum
0.003
0.001
0.001
Median
0.0139
0.01095
0.0116
95th
Percen-
tile
0.0969
0.05185
0.06
99th
Percen-
tile
0.3
0.3424
0.3
Maximum
0.3
0.4764
0.4764
1. RLs (Reporting Limits) for styrene varied, but did not exceed 0.003 ug/L.
42.4 Occurrence in Drinking Water
Styrene is regulated as a volatile organic compound (VOC) in drinking water. All non-
purchased community water systems (CWSs) and non-transient non-community water systems
(NTNCWSs) are required to sample for VOCs. The maximum waiver period for VOCs is six
years for ground water systems and three years for surface water systems.
All CWSs and NTNCWSs must collect four consecutive quarterly samples during the
initial three-year compliance period.l If all four samples are non-detections, then the system may
reduce to annual sampling. After three annual samples without a detection, a system may be
granted a waiver. If a compound is detected (but at less than the MCL), the system must take one
sample per quarter until results are below the MCL (minimum of two quarterly samples for
ground water systems and four quarterly samples for surface water systems). If all quarterly
samples are below the MCL, the system may return to annual sampling. If a compound is
detected at a level greater than the MCL, the system (whether ground water or surface water)
must take four consecutive quarterly samples until all are below the MCL. If all quarterly
samples are below the MCL, the system may return to annual sampling.
The analysis of styrene occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
All of the Six-Year Review-ICR states provided occurrence data for styrene. These data
consist of 372,269 analytical results from 50,421 systems during the period from 1998 to 2005.
The number of sample results and systems vary by state, although the state data sets have been
reviewed and checked to ensure adequacy of coverage and completeness.
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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42.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 42-3
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For styrene, 1.047% of 50,421 systems reported
detections. Exhibit 42-4 lists the minimum, median, 90th percentile, and maximum styrene
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of styrene, based on detections from all systems, is 0.885 |ig/L.
Exhibit 42-3: Styrene Occurrence Data from the
Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
288,205
46,165
86,392,838
Surface Water
84,064
4,256
140,540,798
Combined Ground &
Surface Water
372,269
50,421
226,933,636
Percent with Detections
Ground Water
0.242%
1.003%
3.038%
Surface Water
0.109%
1.527%
2.179%
Combined Ground &
Surface Water
0.212%
1.047%
2.506%
Exhibit 42-4: Styrene Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.02
Median
0.9
90tn
Percentile
8.1
Maximum
710
Surface Water
0.002
0.69
2.6
18.8
Combined Ground &
Surface Water
0.002
0.885
7.5
710
42-4
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The following maps illustrate the geographic distribution of styrene occurrence in
drinking water. Exhibit 42-5 shows the states with systems with at least one detection and
Exhibit 42-6 shows the states with systems with at least one detection greater than the MCL
concentration. Note that five states did not submit data for use in the Six-Year Review (Kansas2,
Louisiana, Mississippi, Pennsylvania, and Washington).
The distribution of systems with detections of styrene is geographically dispersed, and
detection rates were generally low. Fourteen states reported detections in more than 1% of their
systems. In 15 states, between 0.5% and 1% of systems reported detections. Twelve states
reported detections in less than 0.5% of systems. Four states reported detections greater than the
MCL concentration of 100 |ig/L.
Exhibit 42-5: Percentage of Systems with at Least One Styrene
Detection, by State
<"//% States Not Submitting Any Data
States with No Detections
| Less than 0.5% of Systems Detecting
Between 0-5% and 1% of Systems Detecting
More than 1% of Systems Detecting
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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Exhibit 42-6: Percentage of Systems with at Least One Styrene Detection Greater
than the MCL Concentration (> 100 ug/L), by State
Estates Not Submitting Any Data
States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
Between 0.1% and 0.5% of Systems with Detections > MCL
H More than 0.5% of Systems with Detections > MCL
Exhibit 42-7 presents the Stage 1 analysis of styrene occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 50 |ig/L and 100 |ig/L. Seven ground water systems, serving almost 1,700
persons, reported at least one detection greater than or equal to 50 |ig/L; and 4 ground water
systems, serving more than 1,300 persons, reported at least one detection greater than 100 |ig/L.
No surface water systems reported any detections greater than or equal to either threshold.
Exhibit 42-7: Styrene Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 100|jg/L
> 50 |jg/L
Number of
Systems
Exceeding
Threshold
4
7
Percent of
Systems
Exceeding
Threshold
0.009%
0.015%
Total Population-
Served by
Systems
Exceeding
Threshold
1,310
1,651
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.002%
0.002%
Surface
Water
> 100|jg/L
> 50 |jg/L
0
0
0.000%
0.000%
0
0
0.000%
0.000%
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source
Water
Type
Combined
Ground &
Surface
Water
Threshold
> 100|jg/L
> 50 |jg/L
Number of
Systems
Exceeding
Threshold
4
7
Percent of
Systems
Exceeding
Threshold
0.008%
0.014%
Total Population-
Served by
Systems
Exceeding
Threshold
1,310
1,651
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.001%
0.001%
42.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2007. ToxFAQsfor Styrene.
September 2007. Available on the Internet at: http://www.atsdr.cdc.gov/tfacts53.html.
United States Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - Styrene. Last modified September 10, 2007. Available on the Internet at:
http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for styrene.] Accessed February
21,2008.
USEPA. 2008. TRI Explorer: Trends - Styrene. Released February 21, 2008. Available on the
Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for styrene.] Accessed March 8,
2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
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43 2,3,7,8-TCDD (Dioxin)
This chapter on 2,3,7,8-TCDD (dioxin) is part of a report that is organized so that each
chapter presents information on one specific contaminant. Chapter 1 of this report, Introduction,
presents background information on all sources of data used as well as the analytical approach
used to estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and dioxin
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
43.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for dioxin on July 17, 1992 (57 FR
31776 (USEPA, 1992)). The NPDWR established a maximum contaminant level goal (MCLG)
of zero based on a cancer classification of B2, probable human carcinogen. The NPDWR also
established a maximum contaminant level (MCL) of 0.00003 |ig/L based on analytical feasibility.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 1999),
chlorinated dibenzo-p-dioxins (CDDs) are a family of 75 chemically related compounds
commonly known as chlorinated dioxins. Dioxin (C4H4O2) is one of the most toxic and the most
studied of the CDDs. In their pure form, CDDs are crystals or colorless solids. They can enter the
environment as mixtures containing a number of individual components. In water, dioxin will
remain associated with soil or sediments rather than leach. It is subject to breakdown by sunlight
at the surface, but is resistant to biodegradation. Dioxin may accumulate in aquatic organisms
(ATSDR, 1999).
43.2 Use, Production, and Releases
Dioxin is not produced or used commercially in the U.S. except for research purposes. It
is a contaminant formed during the production of some chlorinated organic compounds. It may
also be formed during combustion of a variety of chlorinated organic compounds, during the
chlorine bleaching process at pulp and paper mills, or during chlorination by drinking water and
wastewater treatment plants (ATSDR, 1999).
The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for dioxin.
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Dioxin and dioxin-like compounds are listed as Toxics Release Inventory (TRI)
chemicals. TRI data indicate that total off-site and on-site releases of dioxin and dioxin-like
compounds for the period 2000-2006 ranged from approximately 86,000 pounds to
approximately 149,000 pounds, with maximum releases occurring in 2001 (USEPA, 2008). (No
TRI data were available for dioxin and dioxin-like compounds for 1998 or 1999.)
43.3 Occurrence in Ambient Water
No National Water Quality Assessment (NAWQA) Program data are available from the
United States Geological Survey (USGS) on the occurrence of dioxin in ambient waters from the
Pesticide National Synthesis Project (Gilliom et a/., 2007) or the EPA Summary Analysis of
Cycle 1 data.
43.4 Occurrence in Drinking Water
Dioxin is regulated as a synthetic organic chemical (SOC) in drinking water. All non-
purchased community water systems (CWSs) and non-transient non-community water systems
(NTNCWSs) are required to sample for SOCs. The maximum waiver period for SOCs is three
years, but this waiver can be renewed indefinitely. (Systems may receive a waiver at any time
without having collected an SOC sample. With a waiver, systems are not required to collect an
SOC sample.) Statewide waivers are often granted for dioxin.
All CWSs and NTNCWSs without an SOC waiver must collect four consecutive
quarterly samples during the initial three-year compliance period.l If all four samples are non-
detections, then a system serving less than 3,300 persons may reduce to one sample during each
consecutive compliance period; a system serving more than 3,300 persons may reduce to two
quarterly samples within a 12-month period during a 3-year compliance period. If a chemical is
detected (but is less than the MCL), the system must take one sample per quarter until results are
below the MCL (minimum of two quarterly samples for ground water systems and four quarterly
samples for surface water systems). If all quarterly samples are below the MCL, the system may
return to annual sampling. If a chemical is detected at a level greater than the MCL, the system
(whether ground water or surface water) must take quarterly samples until four consecutive
quarters are below the MCL. If all quarterly samples are below the MCL, the system may return
to annual sampling.
The analysis of dioxin occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
Twenty-seven of the Six-Year Review-ICR states provided occurrence data for dioxin.
These data consist of 11,076 analytical results from 2,383 public water systems (PWSs) during
the period from 1998 to 2005. The number of sample results and systems vary by state, although
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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the state data sets have been reviewed and checked to ensure adequacy of coverage and
completeness.
43.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 43-1
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For dioxin, 0.713% of 2,383 systems reported
detections. Exhibit 43-2 lists the minimum, median, 90th percentile, and maximum dioxin
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of dioxin, based on detections from all systems, is 0.000005 |ig/L.
Exhibit 43-1: Dioxin Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
6,445
1,956
16,399,032
Surface Water
4,631
427
36,455,413
Combined Ground &
Surface Water
11,076
2,383
52,854,445
Percent with Detections
Ground Water
0.155%
0.460%
0.211%
Surface Water
0.216%
1.874%
0.749%
Combined Ground &
Surface Water
0.181%
0.713%
0.582%
Exhibit 43-2: Dioxin Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.000002
Median
0.000005
90tn
Percentile
0.000102
Maximum
0.000178
Surface Water
0.000001
3.5E-06
1.75E-05
0.00003
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source Water Type
Detection Value (ug/L)
Minimum
Median
90tn
Percentile
Maximum
Combined Ground &
Surface Water
0.000001
0.000005
2.75E-05
0.000178
The following maps illustrate the geographic distribution of dioxin occurrence in drinking
water. Exhibit 43-3 shows the states with systems with at least one detection and Exhibit 43-4
shows the states with systems with at least one detection greater than the MCL concentration.
Note that five states did not submit data for use in the Six-Year Review (Kansas2, Louisiana,
Mississippi, Pennsylvania, and Washington). The following states did provide Six-Year data for
most contaminants, but did not provide data for dioxin: Arkansas, Delaware, Hawaii, Iowa,
Illinois, Maine, Michigan, Minnesota, Missouri, New Hampshire, New Jersey, Oklahoma, Rhode
Island, South Carolina, South Dakota, Texas, Virginia, and West Virginia.
Only six states reported detections of dioxin. Two states reported detections in more than
10% of their systems. Two states detected dioxin in 1% to 10% of their systems. Twenty-one
states reported no detections. One state reported detections greater than the MCL concentration
of 0.00003 |ig/L.
Exhibit 43-3: Percentage of Systems with at Least One Dioxin Detection, by State
?///, States with Waivers or Not Submitting
States with No Detections
!Less than 1% of Systems Detecting
Between 1% and 10% of Systems Detecting
| More than 10% of Systems Detecting
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
43-4
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Exhibit 43-4: Percentage of Systems with at Least One Dioxin Detection Greater
than the MCL Concentration (> 0.00003 ug/L), by State
States with Waivers or Not Submitting
States with No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
| Between 0.1% and 0.5% of Systems with Detections > MCL
j More than 0.5% of Systems with Detections > MCL
Exhibit 43-5 presents the Stage 1 analysis of dioxin occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 0.000015 |ig/L and 0.00003 |ig/L. Three (0.126% of) systems, serving more than
9,600 persons, reported at least one detection greater than or equal to 0.000015 |ig/L; and 1
(0.042% of) systems, serving about 7,100 persons, reported at least one detection greater than
0.00003 |ig/L.
Exhibit 43-5: Dioxin Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 0.00003 |jg/L
> 0.00001 5 |jg/L
Number of
Systems
Exceeding
Threshold
1
2
Percent of
Systems
Exceeding
Threshold
0.051%
0.102%
Total Population-
Served by
Systems
Exceeding
Threshold
7,100
7,226
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.043%
0.044%
Surface
Water
> 0.00003 |jg/L
> 0.00001 5 |jg/L
0
1
0.000%
0.234%
0
2,400
0.000%
0.007%
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source
Water
Type
Combined
Ground &
Surface
Water
Threshold
> 0.00003 |jg/L
> 0.00001 5 |jg/L
Number of
Systems
Exceeding
Threshold
1
3
Percent of
Systems
Exceeding
Threshold
0.042%
0.126%
Total Population-
Served by
Systems
Exceeding
Threshold
7,100
9,626
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.013%
0.018%
43.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 1999. ToxFAQsfor Chlorinated
Dibenzo-p-dioxins (CDDs). February 1999. Available on the Internet at:
http://www.atsdr.cdc.gov/tfactsl04.html.
Gilliom, R.J., I.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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
United States Environmental Protection Agency (USEPA). 1992. Drinking Water; National
Primary Drinking Water Regulations - Synthetic Organic Chemicals and Inorganic Chemicals;
National Primary Drinking Water Regulations Implementation; Final Rule. Federal Register.
Vol. 57, No. 138. p. 31776, July 17, 1992.
USEPA. 2008. TRI Explorer: Trends - Dioxin and dioxin-like compounds. Released February
21, 2008. Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for
dioxin and dioxin-like compounds.] Accessed March 8, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
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44 Thallium
This chapter on thallium is part of a report that is organized so that each chapter presents
information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and thallium
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
44.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for thallium on July 17, 1992 (57 FR
3526 (USEPA, 1991)). The NPDWR established a maximum contaminant level goal (MCLG) of
0.0005 mg/L based on a reference dose (RfD) of 0.00007 mg/kg-day and a cancer classification
of D, not classifiable as to human carcinogenicity. The NPDWR also established a maximum
contaminant level (MCL) of 0.002 mg/L based on analytical feasibility.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 1992),
pure thallium is a bluish-white elemental metal. In nature, it is found in clays, soils, and in
copper, lead, and zinc ores (USGS, 2008). In its pure form, it is odorless and tasteless. Thallium
can also be found in alloys with other metals and as a bromine, chlorine, fluorine, or iodine salt.
Thallium exists in two chemical states, thallous and thallic. Thallous, the more common and
stable form, is the form that humans are more likely to come into contact with in the environment
(ATSDR, 1992).
44.2 Use, Production, and Releases
Thallium is most commonly used in electronic devices, switches, and closures by the
semiconductor industry. It also has limited use in the manufacture of special glasses and for
medical procedures that evaluate heart disease. Thallium was also once used as a pesticide for
control of rodents and insects, but that use was banned in 1972 (ATSDR, 1992).
The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for thallium.
Thallium and thallium compounds are listed as Toxics Release Inventory (TRI)
chemicals. TRI data indicate that total off-site and on-site releases of thallium for the period
44-1
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
1998-2006 ranged from approximately 96,000 pounds to approximately 304,000 pounds, with an
increase over time (USEPA, 2008a). Total thallium compound releases ranged from
approximately 1.9 million pounds to approximately 11 million pounds, with a general decrease
over time. Amounts released on-site were greater than amounts released off-site (USEPA,
2008b).
44.3 Occurrence in Ambient Water
No National Water Quality Assessment (NAWQA) Program data are available from the
United States Geological Survey (USGS) on the occurrence of thallium in ambient waters from
the Pesticide National Synthesis Project (Gilliom et a/., 2007) or the EPA Summary Analysis of
Cycle 1 data.
44.4 Occurrence in Drinking Water
Thallium is regulated as an inorganic chemical (IOC) in drinking water. All community
water systems (CWSs) and non-transient non-community water systems (NTNCWSs) are
required to sample for the lOCs.1 The maximum waiver period for lOCs is nine years.
Ground water systems must sample once during the initial three-year compliance period.
After three compliance periods without a detection, a ground water system may be granted a
nine-year waiver. Surface water systems must sample annually during the initial three-year
compliance period. After three annual samples without a detection, a surface water system may
be granted a nine-year waiver. If the results are greater than the MCL, the public water system
(PWS) must take one sample per quarter until results are below the MCL (minimum of two
quarterly samples for ground water systems and four quarterly samples for surface water
systems).2 If all quarterly samples are below the MCL, the system may continue at initial
monitoring indefinitely until the state or EPA establishes an alternate schedule.
The analysis of thallium occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
All of the Six-Year Review-ICR states provided occurrence data for thallium. These data
consist of 185,047 analytical results from 48,925 systems during the period from 1998 to 2005.
The number of sample results and systems vary by state, although the state data sets have been
reviewed and checked to ensure adequacy of coverage and completeness.
1 Nitrate and nitrite have their own monitoring requirements. See the nitrate and nitrite chapters for details of those
requirements.
2 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
44.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 44-1
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For thallium, 3.493% of 48,925 systems reported
detections. Exhibit 44-2 lists the minimum, median, 90th percentile, and maximum thallium
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of thallium, based on detections from all systems, is 0.000665 mg/L.
Exhibit 44-1: Thallium Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
144,990
44,898
85,832,905
Surface Water
40,057
4,027
137,491,940
Combined Ground &
Surface Water
185,047
48,925
223,324,845
Percent with Detections
Ground Water
1.728%
3.285%
11.410%
Surface Water
1 .473%
5.811%
13.385%
Combined Ground &
Surface Water
1 .673%
3.493%
12.626%
Exhibit 44-2: Thallium Summary Statistics
Source Water Type
Ground Water
Detection Value (mg/L)
Minimum
0.00003
Median
0.00046
90tn
Percentile
0.002
Maximum
0.09
Surface Water
0.00003
0.001
0.002
0.01
Combined Ground &
Surface Water
0.00003
0.000665
0.002
0.09
44-3
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
The following maps illustrate the geographic distribution of thallium occurrence in
drinking water. Exhibit 44-3 shows the states with systems with at least one detection and
Exhibit 44-4 shows the states with systems with at least one detection greater than the MCL
concentration. Note that five states did not submit data for use in the Six-Year Review (Kansas3,
Louisiana, Mississippi, Pennsylvania, and Washington).
In three states, greater than 10% of systems detected thallium. In six states, between 5%
and 10% of systems reported detections. For four states, more than 1% of systems reported at
least one detection greater than the MCL concentration of 0.002 mg/L.
Exhibit 44-3: Percentage of Systems with at Least One Thallium Detection,
by State
>> States Not Submitting Any Data
States with No Detections
Less than 5% of Systems Detecting
Between 5% and 10% of Systems Detecting
More than 10% of Systems Detecting
3 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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Exhibit 44-4: Percentage of Systems with at Least One Thallium Detection Greater
than the MCL Concentration (> 0.002 mg/L), by State
Wft States Not Submitting Any Data
States with No Detections > MCL
• Less than 0.5% of Systems with Detections > MCL
M Between 0.5% and 1% of Systems with Detections > MCL
H More than 1% of Systems with Detections > MCL
Exhibit 44-5 presents the Stage 1 analysis of thallium occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 0.001 mg/L and 0.002 mg/L. More than 850 (1.752% of) systems, serving almost
20 million persons, reported at least one detection greater than or equal to 0.001 mg/L; and 125
(0.255% of) systems, serving more than 1.8 million persons, reported at least one detection
greater than 0.002 mg/L.
Exhibit 44-5: Thallium Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 0.002 mg/L
> 0.001 mg/L
Number of
Systems
Exceeding
Threshold
101
703
Percent of
Systems
Exceeding
Threshold
0.225%
1.566%
Total Population-
Served by
Systems
Exceeding
Threshold
281,729
5,653,247
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.328%
6.586%
Surface
Water
> 0.002 mg/L
> 0.001 mg/L
24
154
0.596%
3.824%
1,550,072
14,008,014
1.127%
10.188%
44-5
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source
Water
Type
Combined
Ground &
Surface
Water
Threshold
> 0.002 mg/L
> 0.001 mg/L
Number of
Systems
Exceeding
Threshold
125
857
Percent of
Systems
Exceeding
Threshold
0.255%
1.752%
Total Population-
Served by
Systems
Exceeding
Threshold
1,831,801
19,661,261
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.820%
8.804%
44.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 1992. Toxicological Profile for
Thallium. July 1992. Available on the Internet at:
http://www.atsdr.cdc.gov/toxprofiles/tp54.html.
Gilliom, R.J., I.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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
United States Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
USEPA. 2008a. TRI Explorer: Trends - Thallium. Released February 21, 2008. Available on the
Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for thallium.] Accessed March 6,
2008.
USEPA. 2008b. TRI Explorer: Trends - Thallium Compounds. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for thallium
compounds.] Accessed March 6, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
United States Geological Survey (USGS). 2008. Thallium Statistics and Information. Available
on the Internet at: http://minerals.usgs.gov/minerals/pubs/commodity/thallium. Accessed March
16, 2008.
44-6
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
45 1,2,4-Trichlorobenzene
This chapter on 1,2,4-trichlorobenzene is part of a report that is organized so that each
chapter presents information on one specific contaminant. Chapter 1 of this report, Introduction,
presents background information on all sources of data used as well as the analytical approach
used to estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and 1,2,4-
trichlorobenzene occurrence estimates in ambient water and drinking water. All drinking water
occurrence estimates were based on data from the National Compliance Monitoring Information
Collection Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR
Dataset"). For detailed information regarding this dataset, data management, data quality
assessments, and the analytical approach used to generate all contaminant occurrence estimates
presented in this chapter, please refer to USEPA (2009).
45.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for 1,2,4-trichlorobenzene on July 17,
1992 (57 FR 31776 (USEPA, 1992)). The NPDWR established a maximum contaminant level
goal (MCLG) and a maximum contaminant level (MCL) of 70 |ig/L. The Agency based the
MCLG on a reference dose (RfD) of 10 jig/kg-day (0.01 mg/kg-day) and a cancer classification
of D, not classifiable as to human carcinogenicity.
According to the Hazardous Substance Data Bank (HSDB, 2008), 1,2,4-trichlorobenzene
(CeHsCls) is an aromatic, colorless organic liquid. It tends to adhere to soil, minimizing leaching
into ground water. It is expected to biodegrade slowly in soils and water. It has been reported to
accumulate in aquatic organisms. 1,2,4-Trichlorobenzene is also known as 1,2,4-TCB (Kenneth
Barbalace, 2010).
45.2 Use, Production, and Releases
The greatest uses of 1,2,4-trichlorobenzene are in chemical manufacturing, dyes and
intermediates, dielectric fluid, synthetic transformer oils, lubricants, and as a heat-transfer
medium. 1,2,4-Trichlorobenzene was once used as a soil treatment for termite control (HSDB,
2008).
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 45-1 presents the production of 1,2,4-trichlorobenzene in the United States from
1986 to 2002. Note that the production of 1,2,4-trichlorobenzene in the United States remained
constant from 1986 to 1998 and then decreased in 2002.
45-1
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 45-1: Production of 1,2,4-Trichlorobenzene in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
> 10 million - 50 million pounds
> 10 million - 50 million pounds
> 10 million - 50 million pounds
> 10 million - 50 million pounds
> 1 million - 10 million pounds
Source: USEPA, 2003
1,2,4- Trichlorobenzene is listed as a Toxics Release Inventory (TRI) chemical. TRI data
indicate that total off-site and on-site releases of 1,2,4-trichlorobenzene for the period 1998-2006
ranged from approximately 40,000 pounds to approximately 183,000 pounds, with a general
decrease over time. On-site releases were greater than off-site releases (USEPA, 2008).
45.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of 1,2,4-
trichlorobenzene in ambient water are available from the NAWQA program.
45.3.1 EPA Summary Analysis ofNA WQA Data
EPA, with the cooperation of the USGS, has performed a summary analysis of all Cycle 1
water monitoring data from all study units (1992-2001) for 1,2,4-trichlorobenzene. Detection
frequencies were computed as the percentage of samples and sites with detections (i.e., with at
least one result equal to or greater than the reporting limit). Sample detections can be biased by
frequent sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 45-2. Overall, 1,2,4-
trichlorobenzene was detected in 0.3% of samples and at 0.1% of sites. 1,2,4-Trichlorobenzene
was only detected in surface water. The median concentration based on detections in surface
water was 0.036 |ig/L. The 99th percentile concentration based on detections from all sites was
0.2604 |ig/L.
45-2
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 45-2: EPA Summary Analysis of 1,2,4-Trichlorobenzene Data from NAWQA
Study Units, 1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
4,545
1,403
5,948
% Samples
with
Detections
0.0%
1.4%
0.3%
Number
of Sites
4,127
183
4,310
% Sites
with
Detections
0.0%
3.3%
0.1%
Concentration Values
(of detections, in ug/L)
Minimum
0.008
0.008
Median
0.036
0.036
95th
Percen-
tile
0.1802
0.1802
99th
Percen-
tile
0.2604
0.2604
Maximum
0.2604
0.2604
1. RLs (Reporting Limits) for 1,2,4-trichlorobenzene varied, but did not exceed 0.07 pg/L
45.4 Occurrence in Drinking Water
1,2,4-Trichlorobenzene is regulated as a volatile organic compound (VOC) in drinking
water. All non-purchased community water systems (CWSs) and non-transient non-community
water systems (NTNCWSs) are required to sample for VOCs. The maximum waiver period for
VOCs is six years for ground water systems and three years for surface water systems.
All CWSs and NTNCWSs must collect four consecutive quarterly samples during the
initial three-year compliance period.l If all four samples are non-detections, then the system may
reduce to annual sampling. After three annual samples without a detection, a system may be
granted a waiver. If a compound is detected (but at less than the MCL), the system must take one
sample per quarter until results are below the MCL (minimum of two quarterly samples for
ground water systems and four quarterly samples for surface water systems). If all quarterly
samples are below the MCL, the system may return to annual sampling. If a compound is
detected at a level greater than the MCL, the system (whether ground water or surface water)
must take four consecutive quarterly samples until all are below the MCL. If all quarterly
samples are below the MCL, the system may return to annual sampling.
The analysis of 1,2,4-trichlorobenzene occurrence presented in the following section is
based on state compliance monitoring data from the Six-Year Review-ICR Dataset. This is the
largest and most comprehensive compliance monitoring data set compiled by EPA's Drinking
Water Program to date.
All of the Six-Year Review-ICR states provided occurrence data for 1,2,4-
trichlorobenzene. These data consist of almost 371,132 analytical results from 50,135 systems
during the period from 1998 to 2005. The number of sample results and systems vary by state,
although the state data sets have been reviewed and checked to ensure adequacy of coverage and
completeness.
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
45-3
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
45.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 45-3
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For 1,2,4-trichlorobenzene, 0.321% of 50,135 systems
reported detections. Exhibit 45-4 lists the minimum, median, 90th percentile, and maximum
1,2,4-trichlorobenzene concentrations based on detections from all systems in the Six-Year
Review-ICR Dataset. The median concentration of 1,2,4-trichlorobenzene, based on detections
from all systems, is 0.6 |ig/L.
Exhibit 45-3: 1,2,4-Trichlorobenzene Occurrence Data from the
Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
287,446
45,887
86,306,318
Surface Water
83,686
4,248
140,535,784
Combined Ground &
Surface Water
371,132
50,135
226,842,102
Percent with Detections
Ground Water
0.053%
0.292%
0.903%
Surface Water
0.045%
0.636%
0.880%
Combined Ground &
Surface Water
0.051%
0.321%
0.889%
Exhibit 45-4: 1,2,4-Trichlorobenzene Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.02
Median
0.6
90tn
Percentile
2.74
Maximum
70
Surface Water
0.003
0.5
1.2
10
45-4
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source Water Type
Detection Value (ug/L)
Minimum
Median
90tn
Percentile
Maximum
Combined Ground &
Surface Water
0.003
0.6
2.2
70
Exhibit 45-5 illustrates the geographic distribution of 1,2,4-trichlorobenzene occurrence
in drinking water, identifying the states with systems with at least one detection. (No systems
reported detections greater than the MCL concentration; thus, no map is included for MCL
concentration exceedances.) Note that five states did not submit data for use in the Six-Year
Review (Kansas2, Louisiana, Mississippi, Pennsylvania, and Washington).
Detection rates were generally low for 1,2,4-trichlorobenzene; only five states reported
detections in more than 1% of their systems. In four states, between 0.5% and 1% of systems
reported detections. Sixteen states reported no detections. Furthermore, no states reported
detections greater than the MCL concentration of 70 |ig/L.
Exhibit 45-5: Percentage of Systems with at Least One 1,2,4-Trichlorobenzene
Detection, by State
/////, States Not Submitting Any Data
States with No Detections
KLess than 0.5% of Systems Detecting
Between 0.5% and 1% of Systems Detecting
More than 1% of Systems Detecting
Exhibit 45-6 presents the Stage 1 analysis of 1,2,4-trichlorobenzene occurrence in
drinking water from systems and population-served by those systems in the Six-Year Review-
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
45-5
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
ICR Dataset relative to two thresholds: 35 |ig/L and 70 |ig/L. Two (0.004% of) ground water
systems, serving about 2,100 persons, reported at least one detection greater than or equal to 35
|ig/L. No systems reported detections greater than 70 |ig/L.
Exhibit 45-6: 1,2,4-Trichlorobenzene Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 70 |jg/L
> 35 |jg/L
Number of
Systems
Exceeding
Threshold
0
2
Percent of
Systems
Exceeding
Threshold
0.000%
0.004%
Total Population-
Served by
Systems
Exceeding
Threshold
0
2,131
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.000%
0.002%
Surface
Water
> 70 |jg/L
> 35 |jg/L
0
0
0.000%
0.000%
0
0
0.000%
0.000%
Combined
Ground &
Surface
Water
> 70 |jg/L
> 35 |jg/L
0
2
0.000%
0.004%
0
2,131
0.000%
0.001%
45.5 References
Hazardous Substance Data Bank (HSDB). 2008. 1,2,4-TRICHLOROBENZENE. Available on
the Internet at: http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen7HSDB. [Search for 1,2,4-
TRICHLOROBENZENE.] Accessed: July 7, 2008.
Kenneth Barbalace. 2010. Chemical Database - 1,2,4-Trichlorobenzene.
EnvironmentalChemistry.com. 1995 -2010.
http://EnvironmentalChemistry.com/vogi/chemicals/cn/l,2,4-Trichlorobenzene.html. Accessed
March 16, 2010.
United States Environmental Protection Agency (USEPA). 1992. Drinking Water; National
Primary Drinking Water Regulations-Synthetic Organic Chemicals and Inorganic Chemicals;
National Primary Drinking Water Regulations Implementation; Final Rule. Federal Register.
Vol. 57, No. 138. p. 31776, July 17, 1992.
USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - 1,2,4-Trichlorobenzene. Last modified September 10, 2007. Available on the
Internet at: http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for 1,2,4-
trichlorobenzene.] Accessed February 21, 2008.
45-6
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
USEPA. 2008. TRI Explorer: Trends - 1,2,4-Trichlorobenzene. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for 1,2,4-
trichlorobenzene.] Accessed March 8, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
45-7
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
46 l,l?l-Trichloroethane
This chapter on 1,1,1-trichloroethane is part of a report that is organized so that each
chapter presents information on one specific contaminant. Chapter 1 of this report, Introduction,
presents background information on all sources of data used as well as the analytical approach
used to estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and 1,1,1-
trichloroethane occurrence estimates in ambient water and drinking water. All drinking water
occurrence estimates were based on data from the National Compliance Monitoring Information
Collection Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR
Dataset"). For detailed information regarding this dataset, data management, data quality
assessments, and the analytical approach used to generate all contaminant occurrence estimates
presented in this chapter, please refer to USEPA (2009).
46.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for 1,1,1-trichloroethane on July 8,
1987 (52 FR 25690 (USEPA, 1987)). The NPDWR established a maximum contaminant level
goal (MCLG) and a maximum contaminant level (MCL) of 200 |ig/L. The Agency developed the
MCLG based on a reference dose (RfD) of 35 jig/kg-day (0.035 mg/kg-day) derived from an
inhalation study and a cancer classification of D, not classifiable as to human carcinogenicity.
According to the Agency for Toxic Substances and Disease Registry (ATSDR, 2006),
1,1,1-trichloroethane is a colorless liquid with a sweet, sharp odor. It volatilizes very quickly,
and at high concentrations (between 80,000 and 105,000 ppm), the gas may ignite in the
presence of a spark. In surface waters, such as lakes and rivers, where it partially mixes with
water, much of the chemical evaporates quickly. 1,1,1-Trichloroethane also evaporates from soil
surfaces. Water can easily carry it through soil into ground water where organisms may break it
down. 1,1,1-Trichloroethane does not accumulate readily in aquatic organisms (ATSDR, 2006).
46.2 Use, Production, and Releases
1,1,1-Trichloroethane was once commonly used as an industrial solvent and as the active
ingredient in household products such as spot cleaners, glues, and aerosol sprays. However,
domestic use of the chemical has been banned in the United States since 2002 because its vapors
are detrimental to the ozone layer. Production of 1,1,1-trichloroethane for export is allowed until
2012 (ATSDR, 2006).
The Toxic Substances Control Act (TSCA) Chemical Substance Inventory does not
provide actual production volumes; instead, it indicates at which of five production volume
ranges a chemical was manufactured or imported. The TSCA Inventory is updated every four
years. Exhibit 46-1 presents the production of 1,1,1-trichloroethane in the United States from
1986 to 2002. Note that the production of 1,1,1-trichloroethane in the United States has
decreased since 1990.
46-1
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 46-1: Production of 1,1,1-Trichloroethane in the United States
Inventory Update Year
1986 Range
1990 Range
1994 Range
1998 Range
2002 Range
Production Volume
> 500 million - 1 billion pounds
> 500 million - 1 billion pounds
> 100 million - 500 million pounds
> 100 million - 500 million pounds
> 100 million - 500 million pounds
Source: USEPA, 2003
1,1,1-Trichloroethane is listed as a Toxics Release Inventory (TRI) chemical. TRI data
indicate that total off-site and on-site releases of 1,1,1-trichloroethane for the period 1998-2006
ranged from approximately 76,000 pounds to approximately 888,000 pounds, with a general
decrease over time. On-site releases were greater than off-site releases (USEPA, 2008).
46.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of 1,1,1-
trichloroethane in ambient water are available from the NAWQA program.
46.3.1 EPA Summary Analysis of NAWQA Data
EPA, with the cooperation of USGS, has performed a summary analysis of all Cycle 1
water monitoring data from all study units (1992-2001) for 1,1,1-trichloroethane. Detection
frequencies were computed as the percentage of samples and sites with detections (i.e., with at
least one result equal to or greater than the reporting limit). Sample detections can be biased by
frequent sampling in areas with high (or low) occurrence. Calculating the percentage of sites
with detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 46-2. Overall, 1,1,1-
trichloroethane was detected in 9.4% of samples and at 8.3% of sites. It was detected more
frequently in surface water than in ground water. The median concentration based on detections
from all sites was 0.024 |ig/L. The 99th percentile concentration based on detections from all
sites was 3 |ig/L.
46-2
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 46-2: EPA Summary Analysis of 1,1,1-Trichloroethane Data from NAWQA
Study Units, 1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
4,659
1,413
6,072
% Samples
with
Detections
7.4%
15.9%
9.4%
Number
of Sites
4,159
190
4,349
% Sites
with
Detections
7.2%
31.1%
8.3%
Concentration Values
(of detections, in ug/L)
Minimum
0.002
0.002
0.002
Median
0.0296
0.02
0.024
95th
Percen-
tile
0.72
0.15
0.5882
99th
Percen-
tile
3.524
0.92
3
Maximum
5.7
2.3
5.7
1. RLs (Reporting Limits) for 1,1,1-trichloroethane varied, but did not exceed 0.002 pg/L
46.4 Occurrence in Drinking Water
1,1,1-Trichloroethane is regulated as a volatile organic compound (VOC) in drinking
water. All non-purchased community water systems (CWSs) and non-transient non-community
water systems (NTNCWSs) are required to sample for VOCs. The maximum waiver period for
VOCs is six years for ground water systems and three years for surface water systems.
All CWSs and NTNCWSs must collect four consecutive quarterly samples during the
initial three-year compliance period.l If all four samples are non-detections, then the system may
reduce to annual sampling. After three annual samples without a detection, a system may be
granted a waiver. If a compound is detected (but at less than the MCL), the system must take one
sample per quarter until results are below the MCL (minimum of two quarterly samples for
ground water systems and four quarterly samples for surface water systems). If all quarterly
samples are below the MCL, the system may return to annual sampling. If a compound is
detected at a level greater than the MCL, the system (whether ground water or surface water)
must take four consecutive quarterly samples until all are below the MCL. If all quarterly
samples are below the MCL, the system may return to annual sampling.
The analysis of 1,1,1-trichloroethane occurrence presented in the following section is
based on state compliance monitoring data from the Six-Year Review-ICR Dataset. This is the
largest and most comprehensive compliance monitoring data set compiled by EPA's Drinking
Water Program to date.
All of the Six-Year Review-ICR states provided occurrence data for 1,1,1-
trichloroethane. These data consist of approximately 374,950 analytical results from about
50,440 systems during the period from 1998 to 2005. The number of sample results and systems
vary by state, although the state data sets have been reviewed and checked to ensure adequacy of
coverage and completeness.
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the
MCL.
46-3
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
46.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 46-3
presents the number of samples and systems, as well as the population-served by the systems,
and the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For 1,1,1-trichloroethane, 1.075% of 50,440 systems
reported detections. Exhibit 46-4 lists the minimum, median, 90th percentile, and maximum
1,1,1-trichloroethane concentrations based on detections from all systems in the Six-Year
Review-ICR Dataset. The median concentration of 1,1,1-trichloroethane, based on detections
from all systems, is 1 |ig/L.
Exhibit 46-3: 1,1,1-Trichloroethane Occurrence Data from the
Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
289,053
46,183
86,390,348
Surface Water
85,897
4,257
140,541,198
Combined Ground &
Surface Water
374,950
50,440
226,931,546
Percent with Detections
Ground Water
0.967%
1.052%
4.369%
Surface Water
0.950%
1.315%
7.905%
Combined Ground &
Surface Water
0.963%
1.075%
6.559%
Exhibit 46-4: 1,1,1-Trichloroethane Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.009
Median
1
90tn
Percentile
5.6
Maximum
1,400
Surface Water
0.2
0.97
4.3
92
46-4
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source Water Type
Detection Value (ug/L)
Minimum
Median
90tn
Percent! le
Maximum
Combined Ground &
Surface Water
0.009
1
5.2
1,400
The following maps illustrate the geographic distribution of 1,1,1-trichloroethane
occurrence in drinking water. Exhibit 46-5 shows the states with systems with at least one
detection and Exhibit 46-6 shows the states with systems with at least one detection greater than
the MCL concentration. Note that five states did not submit data for use in the Six-Year Review
(Kansas2, Louisiana, Mississippi, Pennsylvania, and Washington).
Six states reported detections in more than 2% of systems. Five out of these six states are
located in the eastern half of the United States. In 12 states, between 1% and 2% of systems
reported detections. Only two states reported at least one detection greater than the MCL
concentration of 200 |ig/L.
Exhibit 46-5: Percentage of Systems with at Least One 1,1,1-Trichloroethane
Detection, by State
/////> States Not Submitting Any Data
States with No Detections
• Less than 1% of Systems Detecting
Between 1% and 2% of Systems Detecting
More than 2% of Systems Detecting
Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
46-5
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 46-6: Percentage of Systems with at Least One 1,1,1-Trichloroethane
Detection Greater than the MCL Concentration (> 200 ug/L), by State
'////, States Not Submitting Any Data
States witn No Detections > MCL
Less than 0.1% of Systems with Detections > MCL
H Between 0.1% and 0.2% of Systems with Detections > MCL
^H More than 0.2% of Systems with Detections > MCL
Exhibit 46-7 presents the Stage 1 analysis of 1,1,1-trichloroethane occurrence in drinking
water from systems and population-served by those systems in the Six-Year Review-ICR Dataset
relative to two thresholds: 100 |ig/L and 200 |ig/L. Two (0.004% of) ground water systems,
serving 226 persons, reported at least one detection greater than or equal to 100 |ig/L and greater
than 200 |ig/L. No surface water systems reported detections exceeding either threshold.
Exhibit 46-7: 1,1,1-Trichloroethane Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 200 |jg/L
>100|jg/L
Number of
Systems
Exceeding
Threshold
2
2
Percent of
Systems
Exceeding
Threshold
0.004%
0.004%
Total Population-
Served by
Systems
Exceeding
Threshold
226
226
Percent of
Population-Served
by Systems
Exceeding
Threshold
0.000%
0.000%
Surface
Water
> 200 |jg/L
>100|jg/L
0
0
0.000%
0.000%
0
0
0.000%
0.000%
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source
Water
Type
Combined
Ground &
Surface
Water
Threshold
> 200 |jg/L
>100|jg/L
Number of
Systems
Exceeding
Threshold
2
2
Percent of
Systems
Exceeding
Threshold
0.004%
0.004%
Total Population-
Served by
Systems
Exceeding
Threshold
226
226
Percent of
Population-Served
by Systems
Exceeding
Threshold
0.000%
0.000%
46.5 References
Agency for Toxic Substances and Disease Registry (ATSDR). 2006. Toxicological Profile for
1,1,1-Trichloroethane. July 2006. Available on the Internet at:
http ://www. atsdr. cdc. gov/toxprofiles/tp70.html.
United States Environmental Protection Agency (USEPA). 1987. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals; Monitoring for Unregulated Contaminants;
Final Rule. Federal Register. Vol. 52, No. 130. p. 25690, July 8, 1987.
USEPA. 2003. Non-confidential Inventory Update Reporting (IUR) Production Volume
Information - 1,1,1-Trichloroethane. Last modified September 10th, 2007. Available on the
Internet at: http://www.epa.gov/oppt/iur/tools/data/2002-vol.htm. [Search for 1,1,1-
trichloroethane.] Accessed February 21, 2008.
USEPA. 2008. TRI Explorer: Trends - 1,1,1-Trichloroethane. Released February 21, 2008.
Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for 1,1,1-
trichloroethane.] Accessed March 5, 2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
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47 2,4,5-Trichlorophenoxypropionic Acid (Silvex)
This chapter on 2,4,5-Trichlorophenoxypropionic Acid (2,4,5-TP or silvex) is part of a
report that is organized so that each chapter presents information on one specific contaminant.
Chapter 1 of this report, Introduction, presents background information on all sources of data
used as well as the analytical approach used to estimate contaminant occurrence in drinking
water. This contaminant chapter includes background information (such as regulatory history,
general chemical information, and environmental fate and behavior), use and environmental
release information, and silvex occurrence estimates in ambient water and drinking water. All
drinking water occurrence estimates were based on data from the National Compliance
Monitoring Information Collection Request (ICR) Dataset for the Second Six-Year Review (the
"Six Year Review-ICR Dataset"). For detailed information regarding this dataset, data
management, data quality assessments, and the analytical approach used to generate all
contaminant occurrence estimates presented in this chapter, please refer to USEPA (2009).
47.1 Background
The United States Environmental Protection Agency (EPA) published the current
National Primary Drinking Water Regulations (NPDWR) for silvex on January 30, 1991 (56 FR
3526 (USEPA, 1991)). The NPDWR established a maximum contaminant level goal (MCLG)
and a maximum contaminant level (MCL) of 50 |ig/L. The Agency based the MCLG on a
reference dose (RfD) of 8 jig/kg-day (0.008 mg/kg-day) and a cancer classification of D, not
classifiable as to human carcinogenicity.
According to the Hazardous Substance Data Bank (HSDB, 2008), silvex (CgHyCbOs) is a
white organic powder with little odor. It adheres strongly to soils, where it is degraded by
microbial activity. If released to water, silvex will adhere to particles in the water and become
part of the sediment. It biodegrades slowly in water and sediments (HSDB, 2008).
47.2 Use, Production, and Releases
Since 1985, the use of silvex has been banned. The greatest use of silvex was as a post-
emergence herbicide for control of woody plants, and broadleaf herbaceous weeds in rice and
bluegrass turf, sugarcane, rangeland improvement programs, and on lawns. Aquatic uses
included control of weeds in ditches and riverbanks, on floodways, along canals, reservoirs,
streams, and along southern waterways (HSDB, 2008).
The Chemical Substance Inventory Update System contains confidential data reported by
industry as a partial update of the Toxic Substances Control Act (TSCA) Inventory. The TSCA
Chemical Substance Inventory does not report production data for silvex.
Silvex is not listed as a Toxics Release Inventory (TRI) chemical; thus, no TRI release
records are available.
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47.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of silvex in
ambient water are available from the NAWQA program.
47.3.1 NA WQA Pesticide National Synthesis Project
The NAWQA Pesticide National Synthesis Project is a national-scale assessment of the
occurrence and behavior of pesticides in streams and ground water of the United States and the
potential for pesticides to adversely affect drinking water supplies or aquatic ecosystems. Under
the National Synthesis Project, the USGS monitored silvex between 1992 and 2001 in streams
and wells across the country (Gilliom etal., 2007). The maximum long-term method detection
limit for silvex was 0.030 |ig/L.
In NAWQA stream samples (Exhibit 47-1), silvex was never detected in any agricultural,
mixed land use, undeveloped or urban areas.
Exhibit 47-1: USGS National Synthesis Summary of NAWQA Monitoring of
Silvex in Streams, 1992-2001
Land Use
Type
Agricultural
Mixed
Undeveloped
Urban
No. of Samples
(No. of Sites)
1,465(62)
800 (36)
101 (5)
521 (19)
Detection
Frequency
0.00%
0.00%
0.00%
0.00%
50tn Percent! le
(Median)
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
95th Percentile
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
Maximum
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
Source: Gilliom et a/., 2007
1. ND = not detected (Concentration is less than the maximum long term method detection limit and is expected to
be less than any higher percentile concentration shown in the table)
In ground water NAWQA samples (Exhibit 47-2), silvex was found at frequencies
ranging from 0% of samples in undeveloped and urban areas to 0.07% in mixed land use settings,
and 0.09% of samples in agricultural settings. The 95th percentile concentrations were less than
the method detection limit in all settings. The highest concentration, 0.06 |ig/L, was found at an
agricultural and a mixed land use site.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 47-2: USGS National Synthesis Summary of NAWQA Monitoring of
Silvex in Ground Water, 1991-2001
Land Use Type
Agricultural
Mixed
Undeveloped
Urban
Number
of Wells
1,160
1,446
23
607
Detection
Frequency
0.09%
0.07%
0.00%
0.00%
50tn Percentile
(Median)
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
95th Percentile
Concentration
(in ug/L)
ND1
ND1
ND1
ND1
Maximum
Concentration
(in ug/L)
0.06
0.06
ND1
ND1
Source: Gilliom et a/., 2007
1. ND = not detected (Concentration is less than the maximum long term method detection limit and is expected to
be less than any higher percentile concentration shown in the table)
47.3.2 EPA Summary Analysis of NAWQA Data
Whereas the NAWQA program often uses the most representative data for a site to
calculate summary statistics, EPA, with the cooperation of the USGS, has performed a summary
analysis of all Cycle 1 water monitoring data from all study units (1992-2001) for silvex.
Detection frequencies were computed as the percentage of samples and sites with detections (i.e.,
with at least one result equal to or greater than the reporting limit). Sample detections can be
biased by frequent sampling in areas with high (or low) occurrence. Calculating the percentage of
sites with detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 47-3. Silvex was detected in
0.1% of ground water samples and 0.1% of ground water sites. Silvex was never detected in
surface water. The median and 99th percentile concentrations based on detections in ground water
were both 0.06 |ig/L.
Exhibit 47-3: EPA Summary Analysis of Silvex Data from NAWQA Study Units,
1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
3,733
5,478
9,211
% Samples
with
Detections
0.1%
0.0%
0.0%
Number
of Sites
3,377
882
4,259
% Sites
with
Detections
0.1%
0.0%
0.0%
Concentration Values
(of detections, in ug/L)
Minimum
0.06
0.06
Median
0.06
0.06
95th
Percen-
tile
0.06
0.06
99th
Percen-
tile
0.06
0.06
Maximum
0.06
0.06
1. RLs (Reporting Limits) for silvex varied, but did not exceed 0.021 pg/L Note that because this EPA analysis
involves more data points than the USGS analyses presented above, a direct comparison is not possible.
47-3
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47.4 Occurrence in Drinking Water
Silvex is regulated as a synthetic organic chemical (SOC) in drinking water. All non-
purchased community water systems (CWSs) and non-transient non-community water systems
(NTNCWSs) are required to sample for SOCs. The maximum waiver period for SOCs is three
years, but this waiver can be renewed indefinitely. (Systems may receive a waiver at any time
without having collected an SOC sample. With a waiver, systems are not required to collect an
SOC sample.)
All CWSs and NTNCWSs without an SOC waiver must collect four consecutive
quarterly samples during the initial three-year compliance period.l If all four samples are non-
detections, then a system serving less than 3,300 persons may reduce to one sample during each
consecutive compliance period; a system serving more than 3,300 persons may reduce to two
quarterly samples within a 12-month period during a 3-year compliance period. If a chemical is
detected (but is less than the MCL), the system must take one sample per quarter until results are
below the MCL (minimum of two quarterly samples for ground water systems and four quarterly
samples for surface water systems). If all quarterly samples are below the MCL, the system may
return to annual sampling. If a chemical is detected at a level greater than the MCL, the system
(whether ground water or surface water) must take quarterly samples until four consecutive
quarters are below the MCL. If all quarterly samples are below the MCL, the system may return
to annual sampling.
The analysis of silvex occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
Forty-three of the Six-Year Review-ICR states provided occurrence data for silvex.
(There were no silvex data from Hawaii or Oklahoma.) These data consist of 122,713 analytical
results from 32,887 systems during the period from 1998 to 2005. The number of sample results
and systems vary by state, although the state data sets have been reviewed and checked to ensure
adequacy of coverage and completeness.
47.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 47-4
presents the number of samples and systems, as well as the population-served by the systems, and
the percentage of detections and the percentage of the population-served by the systems with
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For silvex, 0.237% of 32,887 systems reported
detections. Exhibit 47-5 lists the minimum, median, 90th percentile, and maximum silvex
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of silvex, based on detections from all systems, is 0.2 |ig/L.
1 All new systems or systems using a new water source that began operation after January 22, 2004 must demonstrate
compliance with the MCL within a period of time specified by the State. The system must also comply with the
initial sampling frequencies specified by the State to ensure that a system can demonstrate compliance with the MCL.
47-4
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 47-4: Silvex Occurrence Data from the Six-Year Review-ICR Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
100,329
29,954
66,468,861
Surface Water
22,384
2,933
116,531,907
Combined Ground &
Surface Water
122,713
32,887
183,000,768
Percent with Detections
Ground Water
0.071%
0.177%
4.241%
Surface Water
0.147%
0.852%
1 .662%
Combined Ground &
Surface Water
0.085%
0.237%
2.599%
Exhibit 47-5: Silvex Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
0.01
Median
0.2
90tn
Percentile
1
Maximum
28
Surface Water
0.01
0.2
0.5
5
Combined Ground &
Surface Water
0.01
0.2
1
28
Exhibit 47-6 illustrates the geographic distribution of silvex occurrence in drinking water,
identifying the states with systems with at least one detection. (No systems reported detections
greater than the MCL concentration; thus, no map is included for MCL concentration
exceedances.) Note that five states did not submit data for use in the Six-Year Review (Kansas2,
Louisiana, Mississippi, Pennsylvania, and Washington). Hawaii and Oklahoma did submit Six-
Year data for most contaminants, but did not submit data for silvex.
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
included in the analyses.
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Detection rates were generally low; five states reported detections in more than 1% of
their systems. Three states reported detections in 0.5% to 1% of systems. Twenty-six states
reported no detections. Furthermore, no states reported detections greater than the MCL
concentration of 50 |ig/L.
Exhibit 47-6: Percentage of Systems with at Least One Silvex Detection,
by State
///ft States with Waivers or Not Submitting
| Slates with No Detections
KLess than 0.5% of Systems Detecting
Between 0.5% and 1% of Systems Detecting
More than 1% of Systems Detecting
Exhibit 47-7 presents the Stage 1 analysis of silvex occurrence in drinking water from
systems and population-served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 25 |ig/L and 50 |ig/L. One (0.003% of) ground water system, serving 240
persons, reported at least one detection greater than or equal to 25 |ig/L. No systems reported
detections greater than 50 |ig/L.
Exhibit 47-7: Silvex Stage 1 Analysis -
Systems and Population with at Least One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 50 |jg/L
> 25 |jg/L
Number of
Systems
Exceeding
Threshold
0
1
Percent of
Systems
Exceeding
Threshold
0.000%
0.003%
Total Population-
Served by
Systems
Exceeding
Threshold
0
240
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.000%
0.000%
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source
Water
Type
Surface
Water
Threshold
> 50 |jg/L
> 25 |jg/L
Number of
Systems
Exceeding
Threshold
0
0
Percent of
Systems
Exceeding
Threshold
0.000%
0.000%
Total Population-
Served by
Systems
Exceeding
Threshold
0
0
Percent of
Population -Served
by Systems
Exceeding
Threshold
0.000%
0.000%
Combined
Ground &
Surface
Water
> 50 |jg/L
> 25 |jg/L
0
1
0.000%
0.003%
0
240
0.000%
0.000%
47.5 References
Gilliom, R.J., I.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 p.
Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ 129l/appendix7/.
Hazardous Substance Data Bank (HSDB). 2008. SILVEX. Available on the Internet at:
http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen7HSDB. [Search for Silvex.] Accessed: July 7,
2008.
United States Environmental Protection Agency (USEPA). 1991. National Primary Drinking
Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for
Unregulated Contaminants; National Primary Drinking Water Regulations Implementation;
National Secondary Drinking Water Regulations; Final Rule. Federal Register. Vol. 56, No. 30.
p. 3526, January 30, 1991.
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. Office of Water. EPA-815-B-09-006. October 2009.
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48 Uranium
This chapter on uranium is part of a report that is organized so that each chapter presents
information on one specific contaminant. Chapter 1 of this report, Introduction, presents
background information on all sources of data used as well as the analytical approach used to
estimate contaminant occurrence in drinking water. This contaminant chapter includes
background information (such as regulatory history, general chemical information, and
environmental fate and behavior), use and environmental release information, and uranium
occurrence estimates in ambient water and drinking water. All drinking water occurrence
estimates were based on data from the National Compliance Monitoring Information Collection
Request (ICR) Dataset for the Second Six-Year Review (the "Six Year Review-ICR Dataset").
For detailed information regarding this dataset, data management, data quality assessments, and
the analytical approach used to generate all contaminant occurrence estimates presented in this
chapter, please refer to USEPA (2009).
48.1 Background
EPA published the current National Primary Drinking Water Regulations (NPDWR) for
uranium on December 7, 2000 (65 FR 76707 (USEPA, 2000)). The NPDWR established a
maximum contaminant level goal (MCLG) of zero (based on a cancer classification of A, known
human carcinogen) and a maximum contaminant level (MCL) of 30 |ig/L. This regulation
became effective on December 8, 2003.
USEPA (2001) explains that for the MCL rulemaking, EPA assumed a typical conversion
factor of 0.9 pCi/|ig for the mix of uranium isotopes found at public water systems (PWSs),
which means that an MCL of 30 |ig/L will typically correspond to 27 pCi/L. EPA considered the
30 |ig/L level (which corresponds to a 27 pCi/L level) to be appropriate because it is protective
for both kidney toxicity and cancer. However, the relationship between mass concentration
(|ig/L) and activity (pCi/L) is dependent upon the relative mix of the radioactive isotopes (e.g.,
uranium-234, uranium-235, uranium- 238) that comprise the uranium at a particular drinking
water source.1 In circumstances with more extreme conversion factors (> 1.5 pCi/|ig), uranium
activity levels may exceed 40 pCi/L. In these circumstances, EPA recommends that drinking
water systems mitigate uranium levels to 30 pCi/L or less, to provide greater assurance that
adequate protection from cancer health effects is being afforded (USEPA, 2001).
According to USEPA (2007), uranium is a naturally-occurring element found at low
levels in virtually all rock, soil, and water. Significant concentrations of uranium occur in some
substances such as phosphate rock deposits, and minerals such as uraninite in uranium-rich ores.
Because uranium has such a long radioactive half-life (4.47xl09 years for U-238), the total
global quantity remains relatively constant (USEPA, 2007).
1 For further discussion of mass and activity, including the formula to convert between the two measurement units,
see USEPA (1999).
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48.2 Use, Production, and Releases
Uranium metal is very dense and heavy. When depleted, uranium is used by the military
as shielding to protect Army tanks, and also in parts of bullets and missiles. The military also
uses enriched uranium to power nuclear propelled Navy ships and submarines, and in nuclear
weapons. Fuel used for naval reactors is typically highly enriched in U-235. In nuclear weapons,
uranium is also highly enriched (USEPA, 2007)
The main use of uranium in the civilian sector is to fuel commercial nuclear power
plants, where fuel is typically enriched in U-235 to 2-3%. Depleted uranium is used in
helicopters and airplanes as counter weights on certain wing parts. Other uses include ceramic
glazes where small amounts of natural uranium (i.e., not having gone through the enrichment
process) may be added for color. Some lighting fixtures utilize uranium, as do some
photographic chemicals. Phosphate fertilizers often contain high amounts of natural uranium
because the mineral material from which they are made is typically high in uranium. Also,
people who collect rocks and minerals may have specimens of uranium minerals in their
collection such as pitchblende, uraninite, autunite, uranophane, or coffmite (USEPA, 2007).
48.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the sources of most drinking water. The United States
Geological Survey (USGS) National Water Quality Assessment (NAWQA) program is a
national-scale assessment of the occurrence of contaminants in ambient surface and ground
water. Contaminant occurrence in ambient water provides information on the potential for
contaminants to adversely affect drinking water supplies. Data on the occurrence of uranium in
ambient water are available from the NAWQA program.
48.3.1 EPA Summary Analysis of NAWQA Data
EPA, with the cooperation of the USGS, has performed a summary analysis of all Cycle
1 water monitoring data from all study units (1992-2001) for uranium. Detection frequencies
were computed as the percentage of samples and sites with detections (i.e., with at least one
result equal to or greater than the reporting limit). Sample detections can be biased by frequent
sampling in areas with high (or low) occurrence. Calculating the percentage of sites with
detections can reduce this bias.
The results of the EPA analysis are presented in Exhibit 48-1. Overall, uranium was
detected in 45.6% of samples and at 50.6% of sites. Uranium was detected more frequently in
surface water sites than in ground water sites, although ground water sites are generally more
likely to have detections of uranium. The median uranium concentration based on detections
from all sites was about 3.4 |ig/L. The 99th percentile concentration based on detections from all
sites was 115 |ig/L.
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 48-1: EPA Summary Analysis of Uranium Data from NAWQA Study Units,
1992-2001
ground
water
surface
water
all
sites
Detection Frequency
(detections are results > RL1)
Number
of
Samples
7,522
4,978
12,500
% Samples
with
Detections
49.1%
40.2%
45.6%
Number
of Sites
3,373
430
3,803
% Sites
with
Detections
50.2%
53.7%
50.6%
Concentration Values
(of detections, in ug/L)
Minimum
0.009
0.009
0.009
Median
3.274
3.607
3.434
95th
Percen-
tile
54
22
42.22
99th
Percen-
tile
153.45
42
115
Maximum
553
74
553
1. RLs (Reporting Umits) for uranium varied, but did not exceed 0.009 pg/L
48.4 Occurrence in Drinking Water
Initially, all community water systems (CWSs) must collect four consecutive quarterly
samples at all entry points to the distribution system between December 8, 2003 and December
31, 2007, unless data have been grandfathered. If the average is less than the detection limit, the
system may reduce sampling to once every nine years. If the average is equal to or greater than
the detection limit but equal to or less than 1A the MCL, the system may reduce sampling to once
every six years. If the average is greater than 1A the MCL (but is equal to or less than the MCL),
the system may reduce sampling to once every three years. If the average is greater than the
MCL, the system must take one sample each quarter until the annual average is below the MCL.
Quarterly monitoring is also triggered by one result that is more than four times the MCL or high
enough to cause the running annual average to exceed the MCL. Gross alpha samples may also
be used as a substitute for uranium samples, as long as gross alpha activity is equal to or less
than 15pCi/L.
The analysis of uranium occurrence presented in the following section is based on state
compliance monitoring data from the Six-Year Review-ICR Dataset. This is the largest and most
comprehensive compliance monitoring data set compiled by EPA's Drinking Water Program to
date.
Uranium data were provided by 33 of the Six-Year Review-ICR states. (No data were
received from Alabama, Arkansas, Delaware, Georgia, Hawaii, Indiana, Kentucky, Michigan,
New Hampshire, Oklahoma, Tennessee, or Utah.) The uranium data from the 33 states consist of
41,581 analytical results from 5,921 PWSs during the period from 1998 to 2005. The number of
sample results and systems vary by state, although the state data sets have been reviewed and
checked to ensure adequacy of coverage and completeness.
48.4.1 Stage 1 Analysis of Occurrence Data
Stage 1 analyses have been performed at the sample and system levels. Exhibit 48-2
presents the number of samples and systems, as well as the population-served by the systems,
and the percentage of detections and the percentage of the population-served by the systems with
48-3
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
detections. Detections in systems provide a fundamental indication of national occurrence, but
are not representative of MCL violations. For uranium, 69.262% of 5,921 systems reported
detections. Exhibit 48-3 lists the minimum, median, 90th percentile, and maximum uranium
concentrations based on detections from all systems in the Six-Year Review-ICR Dataset. The
median concentration of uranium, based on detections from all systems, is 6.8 |ig/L.
Exhibit 48-2: Summary of Uranium Occurrence Data from the Six-Year Review-ICR
Dataset
Source Water Type
Number of
Samples
Number of
Systems
Population-
Served by
Systems
Total Number
Ground Water
31,461
5,191
23,338,623
Surface Water
10,120
730
47,292,769
Combined Ground &
Surface Water
41,581
5,921
70,631,392
Percent with Detections
Ground Water
70.227%
71.528%
81.666%
Surface Water
71.522%
53.151%
75.079%
Combined Ground &
Surface Water
70.542%
69.262%
77.256%
Exhibit 48-3: Uranium Summary Statistics
Source Water Type
Ground Water
Detection Value (ug/L)
Minimum
1.49E-06
Median
6.57
90tn
Percentile
35
Maximum
469
Surface Water
0.001493
7.31
25.07
244.77
Combined Ground &
Surface Water
1.49E-06
6.8
32.83
469
The following maps illustrate the geographic distribution of uranium occurrence in
drinking water. Exhibit 48-4 shows the states with systems with at least one detection and
Exhibit 48-5 shows the states with systems with at least one detection greater than the MCL
concentration. Note that five states did not submit any data for use in the Six-Year Review
(Kansas2, Louisiana, Mississippi, Pennsylvania, and Washington). Alabama, Arkansas,
2 Kansas submitted data after the data management and analyses had been conducted; data for Kansas are not
48-4
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Delaware, Georgia, Hawaii, Indiana, Kentucky, Michigan, New Hampshire, Oklahoma, or
Tennessee submitted Six-Year data for most contaminants, but did not submit data for uranium.
The distribution of systems with detections of uranium is geographically dispersed and
detection rates were generally low. In seven states, more than 90% of systems reported
detections of uranium. In 11 states, more than 10% of systems reported at least one detection
greater than the MCL concentration of 30 |ig/L.
Exhibit 48-4: Percentage of Systems with at Least One Uranium Detection, by
State
£ States with Waivers or Not Submitting
States with No Detections
~ Less than 50% of Systems Detecting
| Between 50% and 90% of Systems Detecting
^B More than 90% of Systems Detecting
included in the analyses.
48-5
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Exhibit 48-5: Percentage of Systems with at Least One Uranium Detection Greater
than the MCL Concentration (> 30 ug/L), by State
;%£
~
B
H
States with Waivers or Not Submitting
States with No Detections > MCL
Less than 5% of Systems with Detections > MCL
Between 5% and 10% of Systems with Detections > MCL
More than 10% of Systems with Detections > MCL
Exhibit 48-6 presents the Stage 1 analysis of uranium occurrence in drinking water from
systems and populations served by those systems in the Six-Year Review-ICR Dataset relative to
two thresholds: 15 |ig/L and 30 |ig/L. A total of 923 (15.589% of) PWSs, serving more than 19.5
million persons, reported at least one detection greater than or equal to 15 |ig/L; and 448
(7.566% of) PWSs, serving almost 8.4 million persons, reported at least one detection greater
than 30 |ig/L.
Exhibit 48-6: Uranium Stage 1 Analysis - Systems and Population with at Least
One Threshold Exceedance
Source
Water
Type
Ground
Water
Threshold
> 30 |jg/L
>15|jg/L
Number of
Systems
Exceeding
Threshold
413
846
Percent of
Systems
Exceeding
Threshold
7.956%
16.297%
Total Population-
Served by
Systems
Exceeding
Threshold
1,240,188
5,684,077
Percent of
Population-Served
by Systems
Exceeding
Threshold
5.314%
24.355%
Surface
Water
> 30 |jg/L
> 1 5 |jg/L
35
77
4.795%
10.548%
7,153,925
13,809,436
15.127%
29.200%
48-6
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EPA-OGWDW Contaminant Occurrence Support Document for 2" 6-Year Review Category 2 Contaminants October 2009
Source
Water
Type
Combined
Ground &
Surface
Water
Threshold
> 30 |jg/L
>15|jg/L
Number of
Systems
Exceeding
Threshold
448
923
Percent of
Systems
Exceeding
Threshold
7.566%
15.589%
Total Population-
Served by
Systems
Exceeding
Threshold
8,394,113
19,493,513
Percent of
Population-Served
by Systems
Exceeding
Threshold
11.884%
27.599%
48.5 References
United States Environmental Protection Agency (USEPA). 1999. Radiation Risk Assessment at
CERCLA Sites: Q & A. EPA Report 540/R/99/006, December 1999, pp. 5-6.
USEPA. 2000. National Primary Drinking Water Regulations; Radionuclides; Final Rule.
Federal Register. Vol. 65, No. 236. p. 76707, December 7, 2000.
USEPA. 2001. "Use of Uranium Drinking Water Standards under 40 CFR 141 and 40 CFR 192
as Remediation Goals for Groundwater at CERCLA sites." Memorandum from Elaine F. Davies,
Acting Director. Directive no. 9283.1-14. November 6, 2001. Available on the Internet at:
http://www.epa.gov/swerffrr/documents/uranium_drinking_water_standards.htm
USEPA. 2007. Radiation Protection: Uranium. Last modified November 15, 2007. Available on
the Internet at: http://www.epa.gov/radiation/radionuclides/uranium.html. Accessed March 17,
2008.
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. Office of Water. EPA-815-B-09-006. October 2009.
48-7
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