EPA #815Z08001
Thursday,
February 21, 2008
Part H
Environmental
Protection Agency
Drinking Water Contaminant Candidate
List 3—Draft; Notice
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Federal Register/Vol. 73, No. 35/Thursday, February 21, 2008/Notices
ENVIRONMENTAL PROTECTION
AGENCY
[EPA-HQ-OW-2007-1189 FRL-8529-7]
RIN 2040-AD99
Drinking Water Contaminant Candidate
List 3—Draft
AGENCY: Environmental Protection
Agency (EPA).
ACTION: Notice.
SUMMARY: EPA is publishing for public
review and comment a draft list of
contaminants that are currently not
subject to any proposed or promulgated
national primary drinking water
regulations, that are known or
anticipated to occur in public water
systems, and which may require
regulations under the Safe Drinking
Water Act (SOWA). This is the third
Contaminant Candidate List (CCL 3)
published by the Agency since the
SDWA amendments of 1996.
This draft CCL 3 includes 93
chemicals or chemical groups and 11
microbiological contaminants. The EPA
seeks comment on the draft CCL 3, the
approach used to develop the list, and
other specific contaminants.
DATES: Comments must be received on
or before May 21, 2008.
ADDRESSES: Submit your comments,
identified by Docket ID No. EPA-HQ-
OW-2007-1189, by one of the following
methods:
• http://www.regulations.gov: Follow
the on-line instructions for submitting
comments.
• Mail: Water Docket, Environmental
Protection Agency, Mailcode: 2822T,
1200 Pennsylvania Ave., NTW.,
Washington, DC 20460.
« Hand Delivery: Water Docket, EPA
Docket Center (EPA/DC) EPA West,
Room 3334, 1301 Constitution Ave.,
NW., Washington, DC. Such deliveries
are only accepted during the Docket's
normal hours of operation, and special
arrangements should be made for
deliveries of boxed information.
Instructions: Direct your comments to
Docket ID No. EPA-HQ-OW-2007-
1189. EPA's policy is that all comments
received will be included in the public
docket without change and may be
made available online at http://
www.regulations.gov, including any
personal information provided, unless
the comment includes information
claimed to be Confidential Business
Information (CBI) or other information
whose disclosure is restricted by statute.
Do not submit information that you
consider to be CBI or otherwise
protected through http://
www.regulations.gov OT e-mail. The
http://www.regulations.gov Web site is
an "anonymous access" system, which
means EPA will not know your identity
or contact information unless you
provide it in the body of your comment.
If you send an e-mail comment directly
to EPA without going through http://
www.regulations.gov your e-mail
address will be automatically captured
and included as part of the comment
that is placed in the public docket and
made available on the Internet. If you
submit an electronic comment, EPA
recommends that you include your
name and other contact information in
the body of your comment and with any
disk or CD-ROM you submit. If EPA
cannot read your comment due to
technical difficulties and cannot contact
you for clarification, EPA may not be
able to consider your comment.
Electronic files should avoid the use of
special characters, any form of
encryption, and be free of any defects or
viruses. For additional instructions on
submitting comments, go to Unit I.B of
the SUPPLEMENTARY INFORMATION section
of this document.
Docket: All documents in the docket
are listed in the http://
www.regulations.gov index. Although
listed in the index, some information is
not publicly available, e.g., CBI or other
information whose disclosure is
restricted by statute. Certain other
material, such as copyrighted material,
will be publicly available only in hard
copy. Publicly available docket
materials are available either
electronically in http://
www.regulations.gov or in hard copy at
the Water Docket, EPA/DC, EPA West,
Room 3334, 1301 Constitution Ave.,
NW., Washington, DC. The Public
Reading Room is open from 8:30 a.m. to
4:30 p.m., Monday through Friday,
excluding legal holidays. The telephone
number for the Public Reading Room is
(202) 566-1744, and the telephone
number for the EPA Docket Center is
(202) 566-2426.
FOR FURTHER INFORMATION CONTACT: For
information on chemical contaminants
contact Thomas Carpenter, Office of
Ground Water and Drinking Water,
Standards and Risk Management
Division, at (202) 564-4885 or e-mail
carpenter.thomas@epa.gov. For
information on microbial contaminants
contact Tracy Bone, Office of Ground
Water and Drinking Water, at 202-564-
5257 or e-mail bone.tracv@epa.gov. For
general information contact the EPA
Safe Drinking Water Hotline at (800)
426—4791 or e-mail: hotline-
sdwa@epa.gov.
Abbreviations and Acronyms
<—less than
<—less than or equal to
>—greater than
>—greater than or equal to
p.—microgram, one-millionth of a gram
ug/L—micrograms per liter
ATSDR—Agency for Toxic Substances
and Disease Registry
AWWA—American Water Works
Association
CASRN—Chemical Abstract Services
Registry Number
CDC—Centers for Disease Control and
Prevention
CCL—Contaminant Candidate List
CCL 1—EPA's First Contaminant
Candidate List
CCL 2—EPA's Second Contaminant
Candidate List
CCL 3—EPA's Third Contaminant
Candidate List
CFR—Code of Federal Regulations
CUS/IUR—Chemical Update System/
Inventory Update Rule
DBF—disinfection byproduct
DWEL—drinking water equivalent level
EPA—United States Environmental
Protection Agency
ESA—ethanesulfonic acid
FDA—United States Food and Drug
Administration
FR—Federal Register
g—gram
HAAs—haloacetic acids
lOCs—inorganic contaminants
IRIS—Integrated Risk Information
System
kg—kilogram
L—liter
LD50—lethal dose 50; an estimate of a
single dose that is expected to cause
the death of 50 percent of the exposed
animals; it is derived from
experimental data.
Ibs—pounds
LOAEL—lowest-observed-adverse-effect
level
MCL—maximum contaminant level
MCLG—maximum contaminant level
goal
MRDD—maximum recommended daily
dose
mg/kg—milligrams per kilogram body
weight
mg/kg/day—milligrams per kilogram
body weight per day
mg/L—milligrams per liter
MMWR—Morbidity and Mortality
Weekly Report
NAS—National Academy of Sciences
NCI—National Cancer Institute
NCOD—National Contaminant
Occurrence Database
NDWAC—National Drinking Water
Advisory Council
NOAEL—no-observed-adverse-effect
level
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9629
NRC—National Academy of Sciences'
National Research Council
NPDWR—national primary drinking
water regulation
NTP—National Toxicology Program
OPP—Office of Pesticide Programs
PFOA—perfluorooctanoic acid
PFOS—perfluorooctane sulfonic acid
PWS—public water system
RED—reference dose
SAB—Science Advisory Board
SDWA—Safe Drinking Water Act
TCR—Total Coliform Rule
TD5()—tumorigenic dose 50; The dose-
rate which if administered chronically
for the standard life-span of the
species will have a 50% probability of
causing tumors at some point during
that period.
TRI—Toxics Release Inventory
TDS—training data set
UCM—Unregulated Contaminant
Monitoring
UCMR 1—First Unregulated
Contaminant Monitoring Regulation
UCMR 2—Second Unregulated
Contaminant Monitoring Regulation
US—United States of America
USDA—United States Department of
Agriculture
USGS—United States Geological Survey
WBDO—waterborne disease outbreak
WHO—World Health Organization
yr—year
SUPPLEMENTARY INFORMATION:
I. General Information
A. Does this Action Impose Any
Requirements on My Public Water
System?
B. What Should I Consider as I Prepare My
Comments for EPA?
II. Purpose, Background, and Summary of
This Action
A. What is the Purpose of This Action?
B. Background on the CCL, Regulatory
Determinations, and Unregulated
Contaminant Monitoring
1. Statutory Requirements for CCL and
Regulatory Determinations
2. The First Contaminant Candidate List
3. The Regulatory Determinations for CCL
1
4. The Second Contaminant Candidate List
5. The Regulatory Determinations for CCL
2
6. The Unregulated Contaminant
Monitoring Rule
7. The Third Contaminant Candidate List
C. Summary of the Approach Used to
Identify and Evaluate Candidates for CCL
3
D. What is on EPA's Draft CCL 3?
III. What Analyses Did EPA Use To Develop
the Draft CCL 3?
A. Classification Approach for Chemicals
1. Identifying the Universe
2. Screening from the Universe to a PCCL
3. Using Classification Models to Develop
the CCL 3
4. Selection of the Draft CCL 3—Chemicals
B. Classification Approach for Microbial
Contaminants
1. Developing the Universe
2. The Universe to PCCL
3. The PCCL to Draft CCL Process
4. Selection of the Draft CCL 3 Microbes
from the PCCL
C. Public Input
1. Nominations & Surveillance
2. External Expert Review and Input
3. How are the CCL and UCMR Interrelated
for Specific Chemicals and Groups?
IV. Request for Comment
A. Pharmaceuticals
B. Perfluorooctanoic acid and
Perfluorooctane sulfonic acid
C. Helicobacter pylori
V. EPA's Next Steps
VI. References
I. General Information
A. Does This Action Impose Any
Requirements on My Public Water
System?
The draft Contaminant Candidate List
3 (CCL 3) or the final CCL 3, when
published, will not impose any
requirements on anyone. Instead, this
action notifies interested parties of the
availability of EPA's draft CCL 3 and
seeks comment on the contaminants
listed.
B. What Should I Consider as I Prepare
My Comments for EPA?
You may find the following
suggestions helpful for preparing your
comments:
• Explain your views as clearly as
possible.
• Describe any assumptions that you
used.
• Provide any technical information
and/or data you used that support your
views.
• Provide specific examples to
illustrate your concerns.
• Offer alternatives.
Make sure to submit your comments
by the comment period deadline. To
ensure proper receipt by EPA, identify
the appropriate docket identification
number in the subject line on the first
page of your response. It would also be
helpful if you provided the name, date,
and Federal Register citation related to
your comments.
II. Purpose, Background, and Summary
of This Action
This section briefly summarizes the
purpose of this action, the statutory
requirements, previous activities related
to the Contaminant Candidate List
(CCL), and the approach used to
develop the CCL 3.
A. What Is the Purpose of This Action?
The Safe Drinking Water Act (SDWA),
as amended in 1996, requires EPA to
publish a list of currently unregulated
contaminants that may pose risks for
drinking water (referred to as the
Contaminant Candidate List, or CCL)
and to make determinations on whether
to regulate at least five contaminants
from the CCL with a national primary
drinking water regulation (NPDWR)
(section 1412(b)(l)). The 1996 SDWA
requires the Agency to publish both the
CCL and the regulatory determinations
every five years. The purpose of this
action is to present EPA's draft list of
contaminants on the CCL 3, a
description of the selection process, and
the rationale used to make the list.
This action also includes a request for
comment on the Agency's draft CCL 3,
the approach used to develop the list,
and other specific contaminants.
B. Background on the CCL, Regulatory
Determinations, and Unregulated
Contaminant Monitoring
1. Statutory Requirements for CCL and
Regulatory Determinations
Section 1412(b) (1) of SDWA, as
amended in 1996, requires EPA to
publish the Contaminant Candidate List
every five years. SDWA specifies that
the list must include contaminants that
are not subject to any proposed or
promulgated NPDWRs, are known or
anticipated to occur in public water
systems (PWSs), and may require
regulation under SDWA.
The 1996 SDWA Amendments also
specify three criteria to determine
whether a contaminant may require
regulation:
• The contaminant may have an
adverse effect on the health of persons;
• The contaminant is known to occur
or there is a substantial likelihood that
the contaminant will occur in public
water systems with a frequency and at
levels of public health concern; and
• In the sole judgment of the
Administrator, regulation of such
contaminant presents a meaningful
opportunity for health risk reduction for
persons served by public water systems.
In developing the draft CCL 3, the
Agency considered the best available
data and information for unregulated
contaminants. As required under the
Safe Drinking Water Act, EPA evaluated
substances identified in section 101(14)
of the Comprehensive Environmental
Response, Compensation, and Liability
Act of 1980 and substances registered as
pesticides under the Federal Insecticide,
Fungicide, and Rodenticide Act. In
addition to these required data sources,
the Agency also developed the National
Contaminant Occurrence Database
(NCOD) established under section
1445(g) of SDWA. Substances from
NCOD were included in the initial set
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of contaminants considered for the draft
CCL 3.
SDWA also directs the Agency to
consider the health effects and
occurrence information for unregulated
contaminants to identify those
contaminants that present the greatest
public health concern related to
exposure from drinking water. In
selecting contaminants for the draft CCL
3, adverse health effects that may pose
a greater risk to subgroups which
represent a meaningful portion of the
population were considered. Adverse
health effects associated with infants,
children, pregnant women, the elderly,
and individuals with a history of serious
illness were evaluated for both
chemicals and microbes. The specific
analyses and evaluations used by the
Agency are discussed and cited in the
relevant sections of this notice.
2. The First Contaminant Candidate List
Following the 1996 SDWA
Amendments, EPA sought input from
the National Drinking Water Advisory
Council (NDWAC) on the process that
should be used to identify contaminants
for inclusion on the first CCL (CCL 1).
For chemical contaminants, the Agency
developed screening and evaluation
criteria based on the recommendations
provided by NDWAC. For
microbiological contaminants, NDWAC
recommended that the Agency seek
external expertise to identify and select
potential waterborne pathogens. As a
result, an external group of
microbiologists and public health
experts developed the criteria for
screening, conducted an evaluation of
microbial agents, and selected the initial
list of microbiological contaminants for
the CCL 1.
The draft CCL 1 was published on
October 6, 1997 (62 FR 52193 (USEPA,
1997)). After consideration of all
comments, EPA published the final CCL
1, which included 50 chemical and 10
microbiological contaminants, on March
2, 1998 (63 FR 10273 (USEPA, 1998 b)).
A more detailed discussion of how EPA
developed CCL 1 can be found in the
1997 and the 1998 Federal Register
notices (62 FR 52193 (USEPA, 1997)
and 63 FR 10273 (USEPA, 1998 b)).
3. The Regulatory Determinations for
CCL1
EPA published its preliminary
regulatory determinations for a subset of
contaminants listed on CCL 1 on June 3,
2002 (67 FR 38222 (USEPA, 2002 b)).
The Agency published its final
regulatory determinations on July 18,
2003 (68 FR 42898 (USEPA, 2003 a)).
EPA identified 9 contaminants from the
60 contaminants listed on CCL 1 that
had sufficient data and information
available to make regulatory
determinations. The 9 contaminants
were Acanthamoeba, aldrin, dieldrin,
hexachlorobutadiene, manganese,
metribuzin, naphthalene, sodium, and
sulfate. The Agency determined that a
national primary drinking water
regulation was not necessary for any of
these 9 contaminants. The Agency
issued guidance on Acanthamoeba and
health advisories for magnesium,
sodium, and sulfate.
4. The Second Contaminant Candidate
List
The Agency published its draft
second CCL (CCL 2) Federal Register
notice on April 2, 2004 (69 FR 17406
(USEPA, 2004)) and the final CCL 2
Federal Register notice on February 24,
2005 (70 FR 9071 (USEPA, 2005 b)). The
CCL 2 carried forward the 51 remaining
chemical and microbial contaminants
that were listed on CCL 1.
5. The Regulatory Determinations for
CCL 2
EPA published its preliminary
regulatory determinations for a subset of
contaminants listed on CCL 2 on May 1,
2007 (72 FR 24015 (USEPA, 2007 d)).
EPA identified 11 contaminants from
the 51 contaminants listed on CCL 2
that had sufficient data and information
available to make preliminary regulatory
determinations. The 11 contaminants
are boron, the dacthal mono- and di-
acid degradates, l,l-dichloro-2,2-bis (p-
chlorophenyl) ethylene (DDE), 1,3-
dichloropropene, 2,4-dinitrotoluene,
2,6-dinitrotoluene, s-ethyl
propylthiocarbamate (EPTC), fonofos,
terbacil, and 1,1,2,2-tetrachloroethane.
The Agency has made a preliminary
determination that a national primary
drinking water regulation is not
necessary for any of these 11
contaminants. The Agency is scheduled
to publish its final regulatory
determinations in 2008. In the May 1,
2007 FR notice, the Agency indicated
that additional information was needed
to make the regulatory determinations
for perchlorate and methyl tertiary butyl
ether (MTBE) and provided a summary
of the current health effects, occurrence,
and exposure information.
6. The Unregulated Contaminant
Monitoring Rule
SDWA provides EPA with the
authority to require all large and a
subset of small systems to monitor for
unregulated contaminants. EPA may
require monitoring for up to 30
contaminants under the Unregulated
Contaminant Monitoring Rule (UCMR).
Since the 1996 SDWA amendments, the
Agency has issued two UCMRs (UCMR
1 and UCMR 2). UCMR 1 was
promulgated on September 17, 1999 (64
FR 50556 (USEPA, 1999)) and UCMR 2
on January 4, 2007 (72 FR 367 (USEPA,
2007 a)), followed by two revisions
published later in January 2007 (72 FR
3916 (USEPA, 2007 b) and 72 FR 4328
(USEPA, 2007 c)). Monitoring under
UCMR 2 will take place during the
2008-2010 time period.
UCMR 2 requires monitoring for
several pesticides and pesticide
degradates, five polybrominated
diphenyl ether (PBDE) flame retardants,
a group of nitrosamines and two
munitions (TNT and RDX). All of the
chemicals on UCMR 2 were included
among the contaminants evaluated for
CCL 3. Data collected under the UCMR
are an important source of occurrence
information for the CCL process.
7. The Third Contaminant Candidate
List
In 1998, the Agency sought advice
from the National Academy of Sciences'
National Research Council (NRG) on
how to improve the CCL process. The
NRC published its recommendations on
the CCL process in 2001 (NRC, 2001).
The NRC proposed a broader, more
reproducible process to identify the CCL
than the process used by EPA in the first
CCL. The NRC recommended that EPA
develop and use a multi-step process for
creating CCL 3 and future CCLs,
whereby a broadly defined "universe"
of potential drinking water
contaminants is identified, assessed,
and reduced to a preliminary CCL
(PCCL) using simple screening criteria.
All of the contaminants on the PCCL
would then be assessed in more detail
using a classification tool to evaluate the
likelihood that specific contaminants
could occur in drinking water at levels
and at frequencies that pose a public
health concern.
In 2002, the Agency sought input
from the National Drinking Water
Advisory Council (NDWAC) on how to
implement the NRC's recommendations
to improve the CCL process. NDWAC
agreed that EPA should proceed with
the NRC's recommendations and
provided some additional
considerations, including the
overarching principles the Agency
should follow. The NDWAC workgroup
met 10 times between September 2002
and May 2004. The NDWAC issued its
recommendations in "The National
Drinking Water Advisory Council
Report on the CCL Classification Process
to the U.S. Environmental Protection
Agency" (NDWAC, 2004).
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NDWAC recommended two guiding
principles for construction of the CCL
universe, which are:
• The universe should include those
contaminants that have demonstrated or
have potential occurrence in drinking
water, and
• The universe should include those
contaminants that have demonstrated or
have potential adverse health effects.
These inclusionary principles apply
to the selection of contaminants for
initial CCL consideration.
The NDWAC also recommended that
the universe of contaminants should be
screened based on widely available data
elements that indicate important health
effects and occurrence information. This
screening step should be as simple as
possible and capable of identifying
contaminants of the greatest significance
for further consideration. Consideration
of a classification approach was also
recommended to increase the
transparency and reproducibility of the
CCL decision process. NDWAC
recommended that EPA pursue
classification models that build on the
screening criteria to further characterize
the adverse health effects and
occurrence of chemical contaminants.
NDWAC noted that the classification
models are tools to help prioritize
contaminants for the CCL. The model
results, available information used by
the model, and expert reviews should be
used to determine which contaminants
are listed for the next CCL. The process
to develop the models should be viewed
as iterative, and EPA should involve
experts and allow opportunities for
meaningful public comment on the
evaluation of contaminants.
NDWAC recommended several
overarching principles that EPA should
use to develop the CCL. In addition to
the need for transparency and public
participation, these overarching
recommendations include:
• Integrate expert judgment
throughout the CCL process. Expert
judgment is inherent throughout the
development of the CCL process and in
implementing that process once it is
developed. Critical reviews, involving
various types of expert consultation and
collaboration, will be useful at key
points in the new, evolving CCL
process.
• Conduct an active surveillance and
nomination/evaluation processes to
ensure timely identification of
information relevant to new and
emerging agents.
• Apply an adaptive management
approach (i.e., an approach that can be
refined in future iterations as more
knowledge is acquired) to implement
the CCL process. The development of
any model should be an adaptive
process, and should be reviewed by
experts with consideration given to
updating the process with each
successive CCL cycle.
NDWAC also recognized that there
were significant differences in the
methods and information used to
characterize chemical and
microbiological contaminants. Chemical
contaminants tend to be characterized
by toxicological and occurrence data
that can be modeled or estimated if
measurement is not possible. These
discrete characteristics are often
captured in data sources. For microbes,
the adverse health effects from exposure
are characterized by clinical or
epidemiological data and there are few
methods to estimate or model their
occurrence. Limited sources of tabular
data for microbes may require
evaluation of primary literature,
technical reports, monographs, and
reference books to identify a universe of
microbes for consideration. NDWAC
recommended the Agency use human
pathogens as the starting point for
identifying microorganisms considered
for inclusion in the CCL and apply a
two-step evaluation of those pathogens.
C. Summary of the Approach Used To
Identify and Evaluate Candidates for
CCL 3
The Agency revised the CCL process
used in previous efforts based on the
knowledge and experience it has gained
from evaluating unregulated
contaminants and the recommendations
and advice from NRC and NDWAC.
Based on these recommendations the
Agency developed and implemented a
classification approach that identifies
priority drinking water contaminants in
a transparent and reproducible manner
that is amenable to an adaptive
management approach.
The Agency's approach to classifying
contaminants is based on available data
to characterize the occurrence and
adverse health risks a contaminant may
pose to consumers of public water
systems. EPA developed and
implemented the following multi-step
CCL process to identify contaminants
for inclusion on the Draft CCL 3.
• Identify a broad universe of
potential drinking water contaminants
(called the CCL 3 Universe). EPA
evaluated 284 data sources that may
identify potential chemical and
microbial contaminants and selected a
set of approximately 7,500 chemical and
microbial contaminants from these data
sources for initial consideration.
• Apply screening criteria to the CCL
3 Universe to identify those
contaminants that should be further
evaluated. Contaminants not passing the
screening criteria remained in the
universe. The screening criteria EPA
developed are based on a contaminant's
potential to occur in public water
systems and the potential for public
health concern. Applying these criteria
narrows the universe of contaminants to
a Preliminary-CCL (or PCCL).
• Identify contaminants from the
PCCL to include on die CCL based on
a more detailed evaluation of
occurrence and health effects. For
chemicals, EPA used structured
classification models as tools to evaluate
and identify drinking water priority
contaminants. Decisions to include
chemicals were made using the model
results and the best available data to
identify contaminants that may occur in
PWSs and may cause adverse health
effects. EPA used a decision tree
approach for microbial contaminants to
identify those contaminants that have
the potential to occur in PWSs and
transmit waterborne disease. These two
approaches resulted in a draft list of
chemicals and microbes for inclusion on
the Draft CCL 3.
• Incorporate public input and expert
review in the CCL process. EPA sought
public input by asking for nominations
of contaminants to consider for the CCL
(71 Ffl 60704 (USEPA, 2006 b)) and
incorporated these nominations in the
three key steps already discussed. EPA
also convened several expert panels for
both chemicals and microbes to review,
and provide input and comment, on the
CCL 3 process and on a review of a
preliminary draft CCL 3.
Exhibit 1 illustrates the CCL multi-
step approach that resulted from the
Agency's efforts, input, and
collaboration with NRC and NDWAC.
This generalized process is applied to
both chemical and microbial
contaminants, though the specific
execution of particular steps differs in
detail.
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Exhibit 1. Schematic of CCL classification process
STEP1
Identifying the
Universe
STEP 2
Screening
to a PCCL
STEP 3
Selecting the
CCL
Proposed CCL
EPA provides a more detailed
discussion of the analyses and decisions
it made to develop the Draft CCL 3 in
the EPA Water Docket. EPA prepared
several support documents that are
available for review at http://
www.regulations.gov. These documents
include:
• Three comprehensive support
documents for the chemicals entitled,
"Contaminant Candidate List 3
Chemicals: Identifying the Universe"
(USEPA, 2008 a), "Contaminant
Candidate List 3 Chemicals: Screening
to a PCCL" (USEPA, 2008 b), and
"Contaminant Candidate List 3
Chemicals: Classification of the PCCL to
the CCL" (USEPA, 2008 c). These
documents describe in detail how the
classification process was developed
and used to select the chemicals for the
Draft CCL.
• Three comprehensive support
documents for the microbes entitled,
"Contaminant Candidate List 3
Microbes: Identifying the Universe"
(USEPA, 2008 d), "Contaminant
Candidate List 3 Microbes: Screening to
the PCCL" (USEPA, 2008 e), and
"Contaminant Candidate List 3
Microbes: PCCL to CCL Process"
(USEPA, 2008 f). These documents
describe the microbial listing process in
detail.
• The Agency also prepared
summaries of stakeholder involvement
and reviews conducted on the CCL
process and draft list. These documents
are also available in the EPA Water
Docket and at http://
www.regulations.gov.
• National Drinking Water Advisory
Council Report on the CCL
Classification Process to the U.S.
Environmental Protection Agency, May
19, 2004.
• A nominations and surveillance
report, entitled "Summary of the
Nominations for the Third Contaminant
Candidate List" (USEPA, 2008 g), which
describes the nominations process and
the contaminants that were nominated
as part of EPA's process.
• Two documents summarizing the
expert review of the chemical and
microbial processes, entitled "Chemical
Expert Input and Review for the Third
Contaminant Candidate List" (USEPA,
2008 h) and "Microbial Expert Input
and Review for the Third Contaminant
Candidate List" (USEPA, 2008 i).
D. What Is on EPA's Draft CCL 3?
EXHIBIT 2.—DRAFT CONTAMINANT
CANDIDATE LIST 3: MICROBIAL CON-
TAMINANTS
Pathogens
Caliciviruses
Campylobacter jejuni
Entamoeba histolytica
Escherichia coli (0157)
Helicobacter pylori
Hepatitis A virus
Legionella pneumophila
Naegleria fowleri
Salmonella enterica
Shigella sonnei
Vibrio cholerae
CHEMICAL CONTAMINANTS
CHEMICAL CONTAMINANTS—Continued
Common name—registry
name
Common name — registry
name
alpha-
Hexachlorocyclohexane ....
1,1,1,2-Tetrachloroethane ....
1,1-Dichloroethane
1 2 3-Trichloropropane
1 3-Butadiene
1 ,3-Dinitrobenzene
1 ,4-Dioxane
1-Butanol
CASRN
319-84-6
630-20-6
75-34-3
96-18-4
106-99-0
99-65-0
123-91-1
71-36-3
2-Methoxyethanol
2-Propen-1-ol i
3-Hydroxycarbofuran
4,4'-Methylenedianiline
Acephate
Acetaldehyde
Acetamide
Acetochlor
Acetochlor ethanesulfonic
acid (ESA)
Acetochlor oxanilic acjd (OA)
Acrolein
Alachlor ethanesulfonic acid
(ESA)
Alachlor oxanilic acid (OA) ...
Aniline
Bensulide
Benzyl chloride
Butylated hydroxyanisole
Captan
Chloromethane (Methyl chlo-
ride)
Clethodim
Cobalt
Cumene hydroperoxide
Cyanotoxins (3).
Dicrotophos
Dimethipin
Dimethoate
Disulfoton
Diuron
Ethion
Ethoprop
Ethylene glycol
Ethylene oxide
Ethylene thiourea
Fenamiphos
Formaldehyde
Germanium
HCFC-22
Hexane
Hydrazine
Methamidophos
Methanol
Methyl bromide
(Bromomethane)
Methyl tert-butyl ether
CASRN
109-86-4
107-18-6
16655-82-6
101-77-9
30560-19-1
75-07-0
60-35-5
34256-82-1
187022-11-3
184992^*4-^
107-02-8
142363-53-9
171262-17-2
62-53-3
741-58-2
100-44-7
25013-16-5
133-06-2
74-87-3
110429-62-4
7440-48-4
80-15-9
141-66-2
55290-64-7
60-51-5
298-04-4
330-54-1
563-12-2
13194-48-4
107-21-1
75-21-8
96-45-7
22224-92-6
50-00-0
7440-56-4
75-45-6
110-54-3
302-01-2
10265-92-6
67-56-1
74-83-9
1634-04-4
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9633
CHEMICAL CONTAMINANTS—Continued CHEMICAL CONTAMINANTS—Continued
Common name — registry
name
Metolachlor .. .
Metolachlor ethanesulfonic
acid (ESA)
Metolachlor oxanilic acid
(OA)
Motinate
Molybdenum
Nitrobenzene
Nitrofen
Nitroglycerin ..
N-Methyl-2-pyrrolidone
N-nitrosodiethylamine
(NDEA)
N-nitrosodimethylamine
(NDMA)
N-nitroso-di-n-propylamine
(NDPA)
N-Nitrosodiphenylamine
N-nitrosopyrrolidine (NPYR)
n-Propylbenzene
o-Toluidine
Oxirane methyl-
Oxydemeton-methyl
Oxyfluorfen
Perohlorate
Permethrin
PFOA (pertluorooctanoic
acid)
Profenofos
Quinoline
RDX(Hexahydrc-1,3,5-
trinitro-1 ,3,5-triazine)
sec-Butylbenzene
Strontium
Tebuconazole
Tebufenozide
Tellurium
Terbufos
Terbufos sulfone
Thiodicarb
Thiophanate-methyl
Toluene diisocyanate
Tribufos
CASRN
51218-45-2
171118-09-5
1 5201 9-73-3
221 2-67-1
7439-98-7
98-95-3
1836-75-5
55-63-0
872-50-4
55-18-5
62-75-9
621-64-7
86-30-6
930-55-2
103-65-1
95-53-4
75-56-9
301-12-2
42874-03-3
14797-73-0
52645-53-1
335-67-1
41198-08-7
91-22-5
121-62-4
135-98-8
7440-24-6
107534-96-3
112410-23-8
1 3494-80-9
13071-79-9
56070-16-7
59669-26-0
23564-05-8
26471-62-5
78-48-8
Common name — registry
name
Triethylamine
Triphenyltin hydroxide
(TPTH)
Urethane
Vanadium
Vinclozolin
Ziram
CASRN
121-44-8
76-87-9
51_79_6
7440-62-2
50471-44-8
1 37-30-4
III. What Analyses Did EPA Use To
Develop the Draft CCL 3?
A. Classification Approach for
Chemicals
1. Identifying the Universe
In the first step in the approach, EPA
compiled potential data sources,
including sources identified at a
stakeholder workshop sponsored by the
American Water Works Association
(AWWA), to develop a broad universe of
potential drinking water contaminants,
as shown in Exhibit 1. This compilation
identified the 284 data sources that were
assessed for the CCL Universe.
EPA developed a decision tree for
data source selection that was based on
four assessment factors, which were
applied to all of the potential data
sources:
• Relevance. Ensures that the data
source provided information on
demonstrated or potential health effects,
occurrence, or potential occurrence
using surrogate information (e.g.,
environmental release, environmental
fate, and transport properties);
• Completeness. Ensures that the data
source had minimum record
requirements—contact name,
description of the data elements, and
how the data were obtained;
• Redundancy. Ensures that the data
source does not contain information
identical to other more comprehensive
data sources; and
• Retrievability. Ensures that the data
in the source are formatted for
automated retrieval. Each source was
accessed on-line (or as provided by the
source) and reviewed.
Basic information about the source, its
purpose, and the data elements it
contained, was compiled and
documented. Every source was
evaluated using all assessment factors
sequentially. Those sources that met all
four factors became the prime sources
that formed the "Universe of Data
Sources." Sources that passed the first
three factors, but were not retrievable,
were designated as supplemental data
sources, to be consulted as necessary
(e.g., to fill in data gaps) in the
development of the CCL. Some of the
sources that were not easily retrievable
were identified as "unique" or
"exceptional" because of the
importance of their data (i.e., the
Hazardous Substance Database). EPA
included chemicals from these sources
in the Universe.
After application of the four
assessment factors, 39 sources (Exhibit
3) met all four factors or were
considered as exceptional. These
sources were the primary sources used
to develop the CCL Chemical Universe.
The details of the how EPA compiled
the list of data sources is discussed in
the document entitled, "CCL 3
Chemicals: Identifying the Universe"
(USEPA, 2008 a).
EXHIBIT 3.—SOURCES THAT COMPRISE THE CHEMICAL UNIVERSE OF DATA SOURCES FOR THE CCL PROCESS
Name of data source
1. ATSDR CERCLA Priority List.
2. ATSDR Minimal Risk Levels (MRLs).
3. Chemical Toxicity Database—Ministry of Health and Welfare, Japan.
4. Chemical Update System/Inventory Update Rule (CUS/IUR)—EPA.
5. Cumulative Estimated Daily Intake/Acceptable Daily Intake (CEDI/ADI) Database—FDA.
6. Database of Sources of Environmental Releases of Dioxin-Like Compounds in the United States—EPA.
7. Distributed Structure Searchable Toxicity Public Database Network (DSSTox)—EPA.
8. Everything Added to Food in the United States (EAFUS) Database—FDA.
9. Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) List—EPA.
10. Generally Regarded As Safe (GRAS) Substance List—FDA.
11. Guidelines for Canadian Drinking Water Quality (CADW): Summary of Guidelines—Health Canada.
12. Hazardous Substances Data Bank (HSDB)—NLM.
13. Health Advisories (HA) Summary Tables—EPA.
14. High Production Volume (HPV) Chemical List—EPA.
15. Indirect Additives Database—FDA.
16. Integrated Risk Information System (IRIS)—EPA.
17. International Agency for Research on Cancer (IARC) Monographs.
18. International Toxicity Estimates for Risk (ITER) Database—TERA.
19. Joint Meeting On Pesticide Residues (JMPR)—2001 Inventory of Pesticide Evaluations—WHO, FAO.
20. National Drinking Water Contaminant Occurrence Database (NCOD)—Round 1 &2—EPA.
21. National Drinking Water Contaminant Occurrence Database (NCOD)—Unregulated Contaminant Monitoring Rule (UCMR)—EPA.
22. National Inorganics and Radionuclides Survey (NIRS)—EPA.
23. National Pesticide Use Database—NCFAP.
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Federal Register/Vol. 73, No. 35/Thursday, February 21, 2008/Notices
EXHIBIT 3.—SOURCES THAT COMPRISE THE CHEMICAL UNIVERSE OF DATA SOURCES FOR THE CCL PROCESS—
Continued
Name of data source
24. National Reconnaissance of Emerging Contaminants (NREC)—USGS Toxic Substances Hydrology Program.
25. National Toxicology Program (NTP) Studies.
26. National Water Quality Assessment (NAWQA)—USGS.
27. OSHA 1988 Permissible Exposure Limits (PELs)—NIOSH.
28. Pesticide Data Program—USDA.
29. Pesticides Pilot Monitoring Program—USGS/EPA.
30. Risk Assessment Information System (RAIS)—Department of Energy—Chemical Factors.
31. Risk Assessment Information System (RAIS)—Department of Energy—Health Effects Data.
32. State of California Chemicals Known to the State to Cause Cancer or Reproductive Toxicity.
33. Substances. Registry System (SRS)—EPA.
34. Syracuse Research Corporation (SRC)—BIODEG.
35. The Toxics Release Inventory (TRI)—EPA.
36. Toxic Substances Control Act (TSCA) List—EPA.
37. Toxicity Criteria Database—California Office of Environmental Health Hazard Assessment (OEHHA).
38. University of Maryland—Partial List of Acute Toxins/Partial List of Teratogens.
39. WHO Guidelines for Drinking Water Quality: Summary Tables.
There were approximately 26,000
unique substances identified from the
39 data sources. Because of the large
number of unique substances identified,
EPA developed an initial universe
selection process. In the first phase of
the data evaluation process, EPA
identified the chemicals that were
present in both health effects and
occurrence data sources. The Agency
queried the data sources and found that
approximately 7,300 chemicals, or about
one-third of the chemicals, were present
in both health effects and occurrence
data sources. Occurrence was defined
broadly to include production data and
environmental occurrence data. EPA
placed these chemicals in the chemical
universe to be further evaluated for
screening to the PCCL. EPA then
examined the rest of the approximately
18,600 chemicals left in the initial
universe more closely to determine
whether they were found only in health
effects data sources or only in
occurrence data sources. EPA found that
approximately 5,100 chemicals were in
health effects data sources only. Many
of these chemicals were biochemical
compounds (e.g., amino acids, sugars,
steroids); mixtures and natural products
(e.g., coal tar, petroleum related
substances, rocks, stone, wool); and
other entries that were identified as
unique "substances" in the data sources
but were not chemicals (e.g., turbidity,
boot and shoe manufacture, surgical
implants). EPA evaluated these to
identify which ones are chemicals of
greatest toxicological concern. Many of
the chemicals fell into the category of
greatest toxicological concern due to
their classification as carcinogens. This
is described in the report entitled, "CCL
3 Chemicals: Screening to a PCCL"
(USEPA, 2008 b). Through this process,
a total of 122 chemicals with only
toxicity data were added to the 7,300
chemicals already in the CCL Chemical
Universe.
The chemicals found only in
occurrence sources were also
categorized. The approximately 13,500
chemicals with only occurrence data
were a diverse group, comprised of
many different types of chemicals. Data
sources that provide the amount of an
individual chemical that is
manufactured and produced account for
70 percent (or 9,344) of the total. The
remaining 30 percent of chemicals are
from various other data sources (i.e.,
finished water, ambient water,
environmental release, environmental
fate and transport properties, and food
additives). EPA grouped these
chemicals by the type of occurrence
data for further evaluation. These
included the following groupings:
• Chemicals with Finished or
Ambient Water Data
• Chemicals with Release Data
• Chemicals with High Production
Volumes
EPA added 42 chemicals with
finished or ambient water data to the
Universe despite the lack of health
effects information in the data sources
because of their demonstrated
occurrence in ambient or potable water.
In addition, disinfection byproducts and
water treatment additives were added to
the Chemical Universe. While there may
not have been measured occurrence data
for these chemicals in the universe of
data sources, they are considered to
have "default" occurrence data because
they are formed in, or intentionally
added to, drinking water supplies.
EPA also added 36 chemicals with an
environmental release data source (e.g.,
those on the Toxics Release Inventory or
with pesticide application data) to the
Chemical Universe even though they
lacked health effects data.
The largest group of chemicals found
only in occurrence data sources had
only production information. These
contaminants include: organometallics,
elements, salts of the inorganic
elements, salts of organic acids, natural
product organics (including oils, fatty
acids, sugars, intermediary metabolites),
and mixtures (e.g., petroleum related
compounds, hydrocarbons, and others).
Over half of the production chemicals
are compounds and/or complexes of
elemental constituents; for example,
there were about 750 sodium or
potassium salt compounds alone. In
these cases, health effects data are not
available for the exact compound, but
are generally available for other related
compounds or the key ion or elemental
constituent (e.g., sodium). Nearly all
elements found in inorganic or organic
salts are represented in the Universe by
other compounds with both health
effects and occurrence data. EPA found
only 10 elements (excluding carbon,
hydrogen, and oxygen, and the inert
gasses krypton, neon, and xenon) that
did not otherwise have representative
compounds with health effects data in
the Universe. EPA added these
compounds (i.e., europium, gadolinium,
gold, lanthanum, praseodymium,
platinum, polonium, samarium,
terbium, and yttrium) to the Universe.
After evaluation of the characteristics of
the chemicals with production data and
the amounts produced on a yearly basis,
and because the primary constituents
(i.e., elements) of the chemicals were
already in the Chemical Universe, EPA
decided to move only those produced at
greater than 1 billion pounds per year to
the CCL Chemical Universe when they
lacked health effects information.
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9635
EPA added a total of 269 chemicals
with only occurrence data to the CCL 3
Chemical Universe. The rest of the
substances included in the original data
sources were not included in the
Universe.
The initial selection process brought
into the CCL Chemical Universe all
substances from the data sources that
met the defined selection criteria,
described above. Upon further review,
EPA found the Chemical Universe also
contained regulated as well as
unregulated compounds, mixtures, and
some substances that were not really
chemicals. To further refine the initial
list, EPA removed chemicals with a
national primary drinking water
regulation. These contaminants are
already regulated; thus, their inclusion
in the CCL process is unnecessary and
does not meet die statutory requirement
for selection of the CCL. EPA removed
1,006 chemicals, which is more than the
number of primary drinking water
standards. This is because regulated
contaminants can be found in many
forms and because many contaminants
are regulated as part of a class or
group(s). For example, EPA removed
approximately 780 radionuclides from
the initial list, because they are
regulated as alpha and beta emitters.
Also removed were various salts of
regulated elements, and entries for
individual trihalomethanes, haloacetic
acids, polychlorinated biphenyls and
polyaromatic hydrocarbons that are
regulated as a group. The Agency has
determined that it is inappropriate to
include aldicarbs (aldicarb, aldicarb
sulfoxide, and aldicarb sulfone) and
nickel on the CCL. These contaminants
are subject to regulation under SDWA
section 1412(b)(2) and thus are not part
of the contaminant selection process
specified under SDWA section
1412(b)(l). In response to an
administrative petition from the
manufacturer Rhone-Poulenc, die
Agency issued an administrative stay of
the effective date of the maximum
contaminant levels (MCLs) for aldicarbs,
and they never became effective.
NPDWRs for nickel were promulgated
on July 17, 1992 (57 FR 31776 (USEPA,
1992)), but the MCL was later vacated
and remanded by the D.C. Court of
Appeals in response to a joint motion by
EPA and industry parties challenging
the nickel MCL and MCLG. Because
these contaminants are subject to
separate regulatory consideration, EPA
has not included them in the CCL
process.
EPA also removed substances that are
considered a mixture of chemicals. EPA
defines a mixture in this case as a
combination of two or more chemicals/
items that are not defined as a unique
substance. Examples of substances in
this category include "chlorinated
compounds, aliphatic alcohols with
more than 14 carbon atoms (c>14), coal-
tar-containing shampoo, petroleum-
related substances, resin acids, and
rosin acids." Undefined mixtures, such
as "diesel engine exhaust" were also
included in this group.
EPA also removed "non-chemically
defined" entries from further
consideration for the initial list.
Examples include: "solar radiation,
wood dust, surgical implants, and
welding fumes." Some of diese
substances are present in the data
sources because they have been
evaluated for their potential to cause
cancer.
The final step removed biological
agents from the initial list.
Contaminants in this category are
biological organisms that are being
evaluated as part of die CCL 3
Microbiological Universe. Entries for
biological entities were uploaded from
the universe of data sources from
various health effects data sources and
pesticide data sources. Many biological
entities were also removed as non-
chemically defined.
During this phase of the data
evaluation, 1,717 chemicals or
substances were removed from the
initial Chemical Universe, leaving
approximately 6,000 chemicals that
were designated as the CCL 3 Universe.
A list of the CCL Chemical Universe is
provided in the docket. EPA further
evaluated these 6,000 chemicals in the
next key step of die process.
2. Screening from the Universe to a
PCCL
The next step in the CCL selection
approach involved narrowing die
Universe of chemicals to a PCCL, as
shown in Exhibit 1. EPA considered and
built upon NDWAC recommendations
that the screening process be based on
a contaminant's potential to occur in
public water systems and the potential
for public health concern, to select those
contaminants that should move to the
PCCL for further evaluation. The
screening approach:
• Identifies chemicals that have
relatively high toxicity with high
potential to occur in PWSs;
• Identifies chemicals diat have
relatively high toxicity with minimal
actual or potential occurrence in
drinking water;
• Identifies chemicals that have high
potential to occur in PWSs with
relatively moderate toxicity; and
• Considers and uses as many of die
available types of healdi effects and
occurrence data identified in the data
source evaluations as practical.
EPA compared the chemicals' health
effects relative to their occurrence and
developed analyses that specifically
incorporate many types of available data
into the screening criteria. The health
effects information included
quantitative, descriptive, or categorical
information. Within each of these broad
types of health effects information, there
are multiple types of reported healdi
related values from multiple sources.
The health effects analyses conducted
by EPA identified approaches to
compare each of diese data types and
identified similarities among chemicals
that could be used to define toxicity
categories. The occurrence information
also included many types of available
data representative of a chemical's
potential to occur in water. Occurrence
data ranged from quantified detection in
PWSs, to environmental release, to
production data.
The basic framework EPA used in
screening is shown in Exhibit 4. EPA
categorized die CCL Chemical Universe
contaminants by their toxicity along the
vertical axis and by uieir occurrence on
the horizontal axis. This allows for
separation of chemicals into those that
move to the PCCL based on their
toxicity and occurrence properties (e.g.,
upper right in Exhibit 4) and those diat
are not further evaluated and remain in
the CCL Chemical Universe (e.g., lower
left in Exhibit 4).
EPA used a set of test chemicals to
develop the screening criteria. This set
of chemicals included regulated and
unregulated chemicals that provided
comprehensive information on health
effects and occurrence in finished and/
or ambient water as well as
environmental release and production
volume. EPA then used these criteria to
select chemicals for the PCCL for further
consideration. The following sections
summarize how EPA developed die
screening criteria by evaluating the
available data for chemicals in the
Universe, using the framework (Exhibit
4) and the test chemicals. A more
detailed discussion is provided in die
support document entitled, "CCL 3
Chemicals: Screening to a PCCL"
(USEPA, 2008 b).
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Federal Register/Vol. 73, No. 35/Thursday, February 21, 2008/Notices
Exhibit 4: Partition for Screening the Universe
Low to High Occurrence
a. Health Effects Data Elements
EPA evaluated the toxicity
information and health effects data
compiled from the data sources in the
Universe and these data varied greatly.
Some of these data are quantitative (e.g.,
RfD, LOAEL, NOAEL, LD5o) and some
are descriptive (e.g., cancer
classifications or predictions). EPA
designed the screening process to
accommodate both types of health
effects data.
The quantitative toxicity elements
and values available in the Universe
included the following:
• RfDs and equivalent (RfD-eq): RfDs,
Minimum Risk Levels (MRLs) from
ATSDR, Tolerable Daily Intakes (TDIs)
from the World Health Organization
(WHO), and Public Health Goals (PHGs)
from California EPA. A reference dose is
an estimate (with uncertainty spanning
perhaps an order of magnitude) of a
daily oral exposure to the human
population (including sensitive
subgroups) that is likely to be without
an appreciable risk of deleterious effects
during a lifetime. There are slight
differences among Agencies in the
methodologies used for some of the RfD
equivalents.
• NOAELs—No Observed Adverse
Effect Levels. The NOAEL is the highest
dose evaluated in a study or group of
studies that does not have a biologically
significant adverse effect on the species
evaluated as compared to controls.
• LOAELS—Lowest Observed
Adverse Effect Levels. The LOAEL is the
lowest dose evaluated in a study or
group of studies that has a biologically
significant adverse effect on the species
evaluated as compared to the controls.
• TD50s—Tumorigenic dose 50. The
dose-rate which if administered
chronically for the standard life-span of
the species will have a 50 percent
probability of causing tumors at some
point during that period.
• MRDD—Maximum Recommended
Daily Dose. Recommendations for the
maximum adult daily therapeutic doses
for pharmaceuticals.
• LD50s—Lethal dose 50; an estimate
of a single dose that is expected to cause
the death of 50 percent of the exposed
animals; it is derived from experimental
data.
EPA used descriptive cancer data to
group data elements into toxicity
categories that provide gradation based
upon the strength of the data. Sources
for the descriptive cancer data included:
• U.S. EPA Cancer Groupings.
• IARC Cancer Groupings.
• NTP weight-of-evidence findings
from cancer bioassays.
• National Cancer Institute (NCI)
weight-of-evidence findings from cancer
bioassays.
• EPA Water Disinfection By-
Products with Carcinogenicity Estimates
(DBF-CAN) groupings based on
carcinogenic potential derived from
Quantitative Structure Activity
Relationship (QSAR) projections.
EPA divided the chemicals in the
Universe into five toxicity categories for
screening based upon the distribution of
the toxicity value for each type of
quantitative data element and/or the
qualitative information on cancer
weight-of evidence. The five toxicity
categories are designated 1 through 5,
with Toxicity Category 1 containing
chemicals in the most toxic grouping
and Toxicity Category 5 the least toxic
grouping.
Based upon the distribution of the
chemicals for each quantitative data
element, EPA selected ranges of toxicity
values for each toxicity category that
differed based upon the type of data
element. For example, the range of
toxicity values that place a LOAEL in
Toxicity Category 1 differs from the
values used for a LD50. Exhibit 5
displays the ranges for each data
element and their respective Toxicity
Categories.
Additional information which
describes how EPA performed the
analyses to select the toxicity categories
is described in the document entitled,
"CCL 3 Chemicals: Screening to a
PCCL" (USEPA, 2008 b).
EXHIBIT 5.—POTENCY MEASURES FOR UNIVERSE DATA ELEMENTS PARTITIONED BASED ON TOXICITY
[mg/kg/day or mg/kg]
Toxicity Category 1
Toxicity Category 2
Toxicity Category 3
Toxicity Category 4
Toxicity Category 5
RfD
<0.0001
0 0001-<0 001
0.001 -<0.05
005-<0 1
>0.1
NOAEL
<0.01
001-c1
1—c10
10-<1000
>1000
LOAEL
<0.01
001-c1
1—e10
10-<1000
>1000
MRDD
<0.01
0.01-<1
1-<10
10-<1000
>1000
LD50
<1
1-<50
50-<500
500-5000
>5000
EPA partitioned the cancer-related
data elements in the Universe into the
Toxicity Categories as shown in Exhibit
6. The cancer data placed chemicals in
only the three highest Toxicity
Categories. EPA did not use quantitative
measures of dose-response for
Carcinogenicity in the screening criteria
because more chemicals have
categorical data and can be analyzed
using this descriptive data than by
cancer slope factors. In addition, EPA
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9637
did not use descriptors indicating lack in categorizing chemicals because those effects associated with exposure to the
of carcinogenic potential or insufficient descriptors apply only to the cancer chemical.
data to determine carcinogenic potential endpoint and do not consider noncancer
EXHIBIT 6.—PARTITIONING OF CANCER DATA BASED ON TD50 VALUES AND WEIGHT-OF-EVIDENCE DESCRIPTORS
Toxicity Category
r*.
Toxicity Category 2
Toxicity Category 3
TD5()
<0.1
0 1-100
>100
EPA
Group A; Human
Carcinogen.
Groups B1 and 82'
likely carcino-
gens.
Group C; Sugges-
tive evidence of
carcinogenicity.
IARC/HC
Group 1
Group 2A
Group 2B
NTP
CE 2 species/2
sexes; or 2 spe-
cies; or 2 sexes.
Combinations of
CE, SE, EE, and
NE.
Combinations of
SE, EE, and NE.
NCI
P 2 species/2
sexes; or 2 spe-
cies; or 2 sexes.
Combinations of P
E and N.
Combinations of E
and N.
DSS-Tox
H.
HM
M and LM
" Cancer data placed chemicals in only the three highest Toxicity Categories.
CE = clear evidence, SE = some evidence, EE = equivocal evidence, NE = no evidence.
P = positive, N = Negative, E = equivocal.
H = high probability, HM = high to medium probability, M = medium probability, LM = medium to low probability.
EPA chose a conservative approach in
the screening process to categorize each
chemical's toxicity and evaluated all the
available health effects dose-response
and categorical data elements for a given
chemical. Chemicals were assigned to
the highest toxicity category indicated
after an evaluation of all the available
data. Accordingly, if a chemical had just
one data element that places it in
Toxicity Category 1, it was categorized
as such even if some of the other data
elements for that same chemical may
place it in a lower toxicity category. For
example, if a chemical is classified as a
2A carcinogen by IARC, it was placed in
Toxicity Category 2 using the
descriptive cancer data even if a
quantified LOAEL from a different study
places it in Toxicity Category 3.
b. Occurrence Data Elements
EPA evaluated the occurrence data
elements for each chemical and placed
them on the horizontal axis of the
screening table. In assessing the data,
EPA found that the data elements that
represent a chemical's potential to occur
in drinking water vary greatly. EPA's
goal was to determine which data
elements best represented the potential
to occur in drinking water. EPA
considered and evaluated data elements
in the following categories:
• Finished Water—measures of
concentration and frequency of
detections.
• Ambient Water—measures of
concentration and frequency of
detections.
• Total Releases in the
Environment—pounds per year and
number of States.
• Pesticide Application Rates—
pounds per year and number of States.
• Production volume—pounds per
year.
In addition to evaluating quantitative
data elements listed above, EPA also
considered chemicals with descriptive
data based upon their likelihood of
occurring in drinking water. Examples
of descriptive occurrence data elements
include characterization as a
disinfection byproduct or a drinking
water treatment chemical.
EPA used the following hierarchal
approach to select the occurrence data
element used to screen a chemical:
Finished Water or Ambient Water >
Environmental Release Data >
Production Data.
The highest data elements in the
hierarchy are the finished and ambient
water data; the lowest, the production
data. Environmental release data from
the Toxics Release Inventory (TRI) and
pesticide application amounts occupy
the middle position in the hierarchy.
EPA also decided that when multiple
data values exist for the chemicals
within a given component of the
hierarchy, the most conservative data
value is used. For example, in the case
of a chemical that has finished water
data and ambient water data, EPA
selected the highest reported
concentration as the occurrence value
used in screening.
EPA obtained the finished water data
elements from the National
Contaminant Occurrence Database
(NCOD), the Unregulated Contaminant
Monitoring (UCM) Rounds 1 and 2, the
National Inorganic Radionuclides
Survey (NIRS), the Unregulated
Contaminant Monitoring Regulation
(UCMR) monitoring, the Information
Collection Rule database for disinfection
byproducts, the U.S. Department of
Agriculture (USDA) Pesticide Data
Program (PDP), and the U.S. Geological
Survey (USGS) Pesticides Pilot
Monitoring Program (PPMP). These
sources included data elements such as
percent samples with detections,
percent drinking water systems with
detections, mean and/or median
detected concentrations, and highest
observed concentrations.
EPA obtained ambient water values
from the USGS National Water Quality
Assessment Program (NAWQA), the
USGS Toxics Substances Hydrology
program's National Reconnaissance of
Emerging Contaminants (NREC) and
related studies, and the PPMP. These
sources included data elements such as
percent samples with detections,
percent sites with detections, mean and/
or median detected concentrations, and
highest observed concentrations.
The environmental release data are
those reported for 2004 from the TRI
and the National Pesticide Use
Database, developed by the National
Center for Food and Agricultural Policy
(NCFAP). The available environmental
release data elements include: total
releases to the environment (Ibs/yr),
number of States with releases,
pesticide total mass active ingredient
applied nationally (Ibs/yr), and number
of States with pesticide application.
EPA chose to use the pounds released
per year into the environment for
screening because the mass applied to
the environment was more directly
related to a potential concentration in
water than the number of States where
a chemical is released or applied.
EPA used the Toxic Substances
Control Act (TSCA) chemical
production volume ranges reported
under the Chemical Update System/
Inventory Update Rule (CUS/IUR) to
assess production volume. EPA selected
the most recent year of data available for
each particular chemical. CUS/IUR
reports chemical production volume
ranges rather than as exact values of
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release, and provides production data
for all chemicals produced in volumes
exceeding 10,000 Ibs/yr. The production
data are reported in 5 categories that
range from less than 10,000 Ibs/yr to
greater than 1 billion Ibs/yr. Therefore,
EPA chose to use those ranges as the
occurrence subdivisions for the
production data.
The occurrence data were grouped by
powers of 10 and arrayed from low to
high across the horizontal axis of the
screening table (Exhibit 4). The
document entitled "CCL 3 Chemicals:
Screening to a PCCL" (USEPA, 2008b)
describes the analyses in greater detail.
In some cases, disinfection
byproducts and water treatment
chemicals lacked quantitative data
elements in the Universe. However,
both groups have a strong potential to be
present in drinking water. EPA moved
chemicals in these two categories
forward to the PCCL for further
evaluation even when limited health
effects and/or occurrence information
were available.
c. Selection of the PCCL
The last step in the screening process
used the intersections between health
effects and occurrence data elements in
the screening table (Exhibit 4) to
establish the PCCL selection line. As
noted above, the health data elements
were grouped by the 5 toxicity
categories with the element showing the
highest potency determining placement
in the screening table. EPA selected the
highest available data element in the
occurrence hierarchy to determine
placement of a chemical on the
horizontal axis in the screening table.
Because the chemicals were evaluated
using a hierarchical approach for their
occurrence elements, EPA developed
separate criteria for each of the
occurrence elements, and used the
placement of a group of test chemicals
that had all or nearly all of the
occurrence data elements, to establish
the position of the PCCL selection line.
The test chemicals were selected from
regulated and past CCL chemicals. Each
had data to illustrate whether it was or
was not of concern as a drinking water
contaminant.
As a secondary analysis, EPA
evaluated existing Drinking Water
Equivalent Levels (DWELs) to confirm
whether they would make the PCCL.
The DWELS were derived from the
lower RfD potency for each of the RfD
Toxicity Categories. The DWEL (mg/L)
is calculated from the RfD in mg/kg/day
by multiplying the RfD by an adult body
weight of 70 kg and dividing by a
drinking water intake of 2 L/day
(rounded to one significant
figure).When comparing the position of
the set of DWELs to the PCCL selection
line, all four toxicity categories would
be put on the PCCL. This analysis
supports the position of the PCCL
selection line for chemicals with
finished or ambient water concentration
data.
EPA also used the test chemicals to
determine the PCCL selection line for
the other occurrence data elements—
total releases to the environment (i.e.,
TRI, pesticide application data) and
production data. For example, the test
chemicals were placed in Exhibit 4
based on their release data to guide the
placement of the line that separated the
"pass to the PCCL" chemicals from the
"do not pass to the PCCL" chemicals. In
general, the PCCL selection line was
positioned so that regulated and most
prior CCL chemicals would be selected
for the PCCL.
EPA also analyzed the test chemicals
with respect to occurrence, releases, and
production data. The test data fit well
for the former two categories. For the
latter, the fit was not as good so EPA
chose to set the PCCL selection line at
the point where all chemicals produced
at greater than 100 million pounds per
year pass to the PCCL even if they fall
in the lowest toxicity category.
The criteria for moving a chemical
with finished or ambient water,
environmental release, and production
data to the PCCL are displayed in
Exhibit 7.
EXHIBIT 7.—CRITERIA FOR A CHEMICAL To PASS SCREENING TO THE PCCL
Occurrence
(by data type)
Toxicity Category 1
Toxicity Category 2
Toxicity Category 3
Toxicity Category 4
Toxicity Category 5 . .,
Finished/ambient
water concentrations
All Concentrations
>1 ua/l
>10 uq/l
>100 ua/l
>1000 p.g/1
Release amount
(per year)
All Amounts
>10000 Ibs/yr
>100,000 Ibs/yr
>1 M Ibs/yr
>10 M Ibs/yr
Production volume
(per year)
All Amounts.
>500 000 Ibs/yr.
>10 M Ibs/yr.
>50 M Ibs/yr.
>1 00 M Ibs/yr.
EPA added DBFs and drinking water
additives that lacked quantitative
occurrence data but fell in the Toxicity
Category 1 or Toxicity Category 2
groupings to the PCCL because of their
high probability for being present in
disinfected and treated drinking water.
The screening process provides a
data-driven, objective, and transparent
process for selecting the PCCL from the
Universe. All Toxicity Category 1
chemicals (i.e., most toxic) were
captured regardless of their occurrence
category. The occurrence threshold
required for the PCCL selection became
less inclusive as the contaminant
toxicity decreased. The screening of the
CCL 3 Universe resulted in the selection
of 532 chemical contaminants for the
PCCL from the approximately 6,000
chemicals that were screened. The
categorical summary of chemicals that
passed the screening is illustrated in
Exhibit 8. A complete chemical PCCL
list can be found in Appendix B of the
document entitled, "CCL 3 Chemicals:
Screening to a PCCL" (USEPA, 2008b).
The 532 PCCL chemicals were further
scrutinized as part of the next key step
in the process. Some of the
contaminants on the PCCL had limited
data available for the scoring protocols
and could not be run through the
models. The 32 contaminants that had
limited data identified in the
appendixes to the "Classification of the
PCCL to the CCL" support document
(EPA 2008c) and will remain on the
PCCL until new data are identified for
further evaluation.
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9639
EXHIBIT 8.—SUMMARY OF TOTAL CHEMICALS THAT PASSED SCREENING FOR PCCL BY SCREENING CATEGORIES
Toxicity categories
Toxicity Category 1
Toxicity Category 2
Toxicity Category 3
Toxicity Category 4
Toxicity Category 5
Finished or
ambient
water con-
centration
29
33
36
5
0
Pesticide
app
4
26
31
4
0
Total re-
leases
56
32
21
10
0
Production
volume
38
61
66
63
17
Totals
127
152
154
82
17
3. Using Classification Models To
Develop the CCL 3
The 532 PCCL chemicals were further
scrutinized as part of this key step in the
process by using classification models
as tools to aid in the selection of the
draft CCL 3. As experience is gained, the
EPA expects to modify and improve the
development of the classification
process for future CCLs.
From the inception of the
development of the CCL classification
process, EPA intended to use
classification models as a decision
support tool. EPA envisioned that, after
testing and evaluation, models would be
used to process complex data in a
consistent, objective, and reproducible
manner and provide a prioritized listing
of candidate contaminants for the last
stage of the CCL process—an expert
review and evaluation. Model
application also would help EPA focus
resources for the expert review and
evaluation of the highest priority
potential contaminants.
An overview of the classification
model approach used to further evaluate
chemicals on the PCCL is described in
the following sections. A detailed
discussion of the process is provided in
a document entitled, "Contaminant
Candidate List 3 Chemicals:
Classification of the PCCL to the CCL"
(USEPA, 2008c). The development of
this classification process involves the
following steps:
• Development of the Attribute
Scoring Protocols.
• Development of the Training Data
Set.
• Application of the Classification
Models.
• Evaluation of Classification Model
Output and Selection of the CCL.
To use models to evaluate and classify
the PCCL contaminants for listing on the
CCL, EPA needed to develop methods to
interrelate the important measures (i.e.,
attributes) that represent a
contaminant's health effects and
potential for occurrence in drinking
water. Four attributes were selected:
Potency, severity, prevalence, and
magnitude. Protocols were developed
for scoring each attribute.
EPA also tested and evaluated the
results of several classification models
to determine which ones might provide
the best decision support tools. To make
this evaluation, EPA developed a
chemical data set and used the data set
to "train" the classification models. The
selected models were utilized to process
the data for the PCCL chemicals and
provide a prioritized listing of candidate
contaminants for the expert review and
evaluation.
a. Development of the Attribute Scoring
Protocols
EPA used attributes to characterize
different chemicals on the basis of
similar qualities or traits. These
qualities or traits represent the
likelihood of occurrence or potential for
adverse health effects of each
contaminant. Throughout the process of
evaluating the attributes EPA recognized
that a wide range of data elements
would have to be used for each attribute
to characterize chemicals on the PCCL.
To evaluate PCCL chemicals with
differing types of occurrence and health
effects data as potential CCL
contaminants, one must be able to
establish consistent relationships among
the different types of data that represent
measures of the attributes. If the same
data were available for all contaminants,
the comparison and prioritization of
candidates would be less complex. To
consistently apply the best available
data for PCCL chemicals, EPA
normalized the different types of data
into scales and scoring protocols that
accept a variety of input data, apply a
consistent framework, and compare
different types of data. The following
sections describe how EPA developed
the scales and scoring protocols for the
health effects and occurrence attributes.
i. Health Effects Attributes
Potency and severity are the attributes
used to describe health effects. EPA
defines potency as the lowest dose of a
chemical that causes an adverse health
effect and severity is based on the
adverse health effect associated with the
dose used to define the measure of
potency. In other words, potency was
scored on the dose that produced the
adverse effect and severity was scored
based on the health-related significance
of the adverse effect (e.g., from
dermatitis to organ effects to cancer).
These two attributes are interrelated, in
that the severity is linked to the measure
of potency.
The following toxicological
parameters were used to evaluate
potency:
• Reference Dose (RfD) or equivalent.
• Cancer potency (concentration in
water for 10~4 cancer risk).
• No-Observed-Adverse-Effect Level
(NOAEL).
• Lowest-Observed-Adverse-Effect
Level (LOAEL).
• Rat oral median Lethal Dose (LD50).
EPA developed a "learning set" of
about two hundred chemicals to
calibrate the potency scoring protocols.
Once the data for the learning set of
chemicals was collected, EPA arrayed
and graphically displayed the data to
analyze their range and distribution.
EPA selected a distribution based on
logarithms (base 10) of the toxicity
parameters rounded to the nearest
integer because it provided a spread of
the chemical toxicity parameters across
the range and the curve was roughly log-
normal.
EPA used a log-based distribution to
establish a potency scoring equation for
each toxicity parameter. This was
accomplished by assigning the most
frequent (modal) value in each
distribution a score of 5 on a 10 point
scale. When the toxicity parameter was
one log more toxic than the modal
value, a score of 6 was assigned.
Similarly, when the parameter was one
log less toxic than the modal value a
score of 4 was given, and so on. EPA
developed an equation for each toxicity
parameter that equated the modal value
to a score of 5 and calculated the
potency score. Because the modal
rounded log differed for the different
measures of toxicity, it was necessary to
use a different equation for each to
normalize the mode to a score of 5. The
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resultant equations are summarized in
Exhibit 9.
EXHIBIT 9.—SCORING EQUATIONS
FOR POTENCY
RfD Score = 10 - (Logic of RfD + 7).
NOAEL Score = 10 - (Logic of NOAEL + 4).
LOAEL Score = 10 - (Logio of LOAEL + 4).
LD50 Score = 10 - (Logio of LD50 + 2).
10~4 cancer risk Score = 10 - (Logio of the
10-4 cancer risk + 6).
For distributions that spanned more
than 5 orders of magnitude above or
below the mode, scores for the tails of
the distribution were truncated at 1 and
10. Conversely, for distributions that did
not span 5 full orders of magnitude
above and below the mode, not all
scores between 1 and 10 were used. For
example, the distribution of the 10 ~4
values for cancer risk was skewed, with
values up to 5 orders of magnitude
above the modal value (more potent
carcinogens) but only 2 orders of
magnitude below the mode (less potent
carcinogens). This meant that the lowest
potency score for this toxicity parameter
was a "3."
EPA tested the scoring process by
using a subset of contaminants with
values from multiple data elements
considered in the process. In the testing
of the potency scoring process, EPA
scored all of the chemicals in the
learning set for each toxicity parameter
to examine the consistency across scores
for the non-cancer measures of potency.
EPA evaluated the agreement of non-
cancer scores across the RfD, NOAEL,
LOAEL and LDso inputs and found the
scores for any given compound to be
generally consistent across parameters.
Because of the general consistency
among scores, EPA determined that a
hierarchy of RfD> NOAEL> LOAEL>
LDso would be used in the scoring of
potency. This hierarchy gives preference
to the potency value with the richest
supporting data set (the RfD—or
equivalent values) and gives the lowest
ranking to the LD50 because it is a
measure of acute rather than chronic
toxicity. If data are available for both the
cancer and noncancer endpoints, the
higher of the cancer or noncancer
potency is selected and the critical
effect of the higher measure of potency
is used to score the severity.
Severity refers to the relative impact
of an adverse health affect. Just as
toxicity increases with dose, the severity
of the observed effect also increases. A
low dose effect could be a simple
increase in liver weight while the same
chemical at a higher dose could cause
cirrhosis of the liver. For consistency,
the measure of severity that was used
for scoring the PCCL chemicals was the
effect or effects seen at the LOAEL.
Restricting severity scores to the effects
at the LOAEL ties them to the data used
to derive the potency score.
The severity measures used to score
the PCCL chemicals differ from those
used for potency, prevalence, and
magnitude because they are descriptive
rather than quantitative. Accordingly,
they are less amenable to automation
and often require more scientific
judgment in their application. To guide
scoring for severity, EPA developed the
nine-point scale displayed in Exhibit 10,
and a compendium of nearly 250
descriptions of critical effects grouped
by their severity scores (e.g., "Chronic
irritation without histopathology
changes" equals a score of 3).
EXHIBIT 10.—FINAL NINE-POINT SCORING PROTOCOL FOR SEVERITY
Score
Critical effect
Interpretation
No adverse effect.
Cosmetic effects ...
Reversible effects; differences in organ weights, body weights
or changes in biochemical parameters with minimal clinical
significance.
Cellular/physiological changes that could lead to disorders (risk
factors or precursor effects).
Significant functional changes that are reversible or permanent
changes of minimal toxicological significance.
Significant, irreversible, non-lethal conditions or disorders
Developmental or reproductive effects
Tumors or disorders likely leading to death
Death.
Considers those effects that alter the appearance of the body
without affecting structure or functions.
Transient, adaptive effects.
Considers cellular/physiological changes in the body that are
used as indicators of disease susceptibility.
Considers those disorders in which the removal of chemical ex-
posure will restore health back to prior condition.
Considers those disorders that persist for over a long period of
time but do not lead to death.
Considers those chemicals that cause developmental effects or
that impact the ability of a population to reproduce.
Considers chemical exposures that result in a fatal disorder and
all types of tumors.
Severity scores 1 through 6 represent
a progression in the severity of die
observed effect. Severity score 7 is used
for all studies where the effect observed
is a reproductive and/or developmental
effect allowing the Agency to track the
chemicals that pose developmental or
reproductive concerns consistent with
the 1996 SDWA. A severity score of 8
was used to track all cases where cancer
is the basis for the potency score.
ii. Occurrence Attributes
EPA used prevalence and magnitude
to describe die potential to occur in
drinking water. Prevalence measures
how widespread the occurrence of die
contaminant is in the environment or
how widely the contaminant may be
distributed. The prevalence measure
indicates the percent of public water
systems or monitoring sites across the
nation with detections, number of States
with releases, or the total pounds
produced nationally. Magnitude relates
to the quantity of a contaminant that
may be found in the environment. The
magnitude measures include the median
concentration of detections in water or
the total pounds of the chemical
released into the environment. In most
cases the same data element (e.g.,
detections in drinking water or amount
released into the environment) could be
used to determine the prevalence, based
on the spatial distribution and
magnitude based on the amounts.
However, where production data were
used to determine prevalence, there was
no corresponding direct measure of
magnitude, so persistence and mobility
data were used as surrogate indicators of
potential magnitude.
Production/persistence and mobility
data are assigned the lowest level in the
hierarchy of data available for
prevalence and magnitude. Persistence-
mobility is determined by chemical
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9641
properties that measure or estimate
environmental fate characteristics of a
contaminant and affect their likelihood
to occur and persist in the water
environment. Data sources that could
provide occurrence data ranged from
direct measure of concentrations in
water to annual measures of
environmental release or production.
EPA compiled a second subset or
learning set of 207 chemicals, with
available data for all of the occurrence
attribute data elements that measured
prevalence and each of the data
elements that measured magnitude, to
calibrate protocols for prevalence and
magnitude.
The data available for the prevalence
attribute consisted of measurements of a
contaminant's occurrence across the
United States. The prevalence measures
have finite ranges such as zero to 100
percent of samples/sites or 1 to 50 States
depending on the reporting
requirements of the available data
source. Accordingly, the scaling of
scores for prevalence focused on
establishing appropriate groupings of
the number of sites or States impacted
across the 1 to 10 scoring scale.
The relationship between production
or even environmental release data and
the actual occurrence in drinking water
is complex. Where actual water
measurements are available, they are the
preferred data element to score
prevalence because they are the most
direct measures of occurrence in
drinking water. EPA selected the
following hierarchy for scoring
prevalence:
• Percent of PWSs with detections
(national scale data).
• Percent of ambient water sites or
samples with detections (national scale
data).
• Number of States reporting
application of the contaminant as a
pesticide.
• Number of States reporting releases
(total) of the chemical.
• Production volume in Ibs/yr.
The production data provide the pounds
produced annually of a chemical
product in the United States. To some
extent, this production rate represents
the commercial importance of the
chemical, so EPA interpreted the high
production tonnage as a likely
indication of wide use of a commodity
chemical and used this information to
score prevalence. For example, a
chemical produced at a billion Ibs/yr is
more likely to be used and released
more widely than a compound
produced at only 10,000 Ibs/yr.
Magnitude represents the quantity of
a contaminant that may be in the
environment. The data sources that
provided the first four levels of the
prevalence hierarchy provided direct
measurements of water and
environmental release that could be
used to score magnitude. However, the
production categories did not supply an
appropriate measure for magnitude.
EPA used the persistence and mobility
for chemicals with only production data
as the basis of the magnitude attribute.
To keep the process straightforward,
EPA used one scale for all water
concentration data. EPA distributed
scores across the range of values so that
organic contaminants could receive high
scores as well as the inorganic
contaminants (lOCs). Comparisons and
adjustments were made until there was
a reasonable distribution of the scores
for organic and inorganic contaminants
by using a semi-logarithmic scale. EPA
selected the single scale approach and
this is discussed in more detail in the
report entitled "CCL 3 Chemicals:
Classification of the PCCL to the CCL"
(USEPA, 2008 c).
When developing the calibration
scales for the release data, the ranges of
data were similarly arrayed using a scale
based on half-log units with a
distribution of scores that reflected the
distribution of the data in the learning
set.
EPA based the persistence and
mobility scores on chemical and
physical properties combined with
environmental fate parameters.
Persistence and mobility act as
measures of potential magnitude
because both fate (i.e., persistence) and
transport (i.e., mobility) affect the
amount of a contaminant to be found in
water. The length of time a chemical
remains in the environment before it is
degraded (persistence) affects its
concentration in water. Similarly, the
mobility of a chemical, or its ability to
be transported to and in water, affects
its potential to reach and dissolve in the
source waters, and thus, the ultimate
concentration of the chemical in the
water.
EPA considered a number of data
elements to measure the mobility of a
chemical in the environment. The
physical/chemical parameters that were
chosen for the CCL process are:
• Organic Carbon Partition
Coefficient (Koc)
• Octanol/Water Partition Coefficient
(Kow)
• Soil/Water Distribution Coefficient
(Kd)
• Henry's Law Coefficient (KH)
• Solubility
The first 4 measures of mobility
represent the equilibrium ratio for the
partitioning of the contaminant from
one medium to another: Koc (soil/
sediment organic carbon: water), Kow
(octanol: water), Kd (soil/sediment:
water) and Henry's Law Coefficient (air:
water). Koc, Kow and Kd are sometimes
expressed as logs of the original
measurements. The measures of
persistence reflect the time the chemical
will remain unchanged in the
environment. Persistence is reflected in
the following measures of
environmental fate:
• Half-Life
• Measured Degradation Rate
• Modeled Degradation Rate
Each of the mobility and persistence
data elements listed above are presented
in hierarchical order, with the most
desirable at the top (i.e., the first data to
be used if available).
As was the case with prevalence, EPA
used a hierarchy in scoring magnitude.
The hierarchy uses finished water
occurrence data if available, and if not,
the highest available element in the
hierarchy of finished water data >
ambient water data > environmental
release data > persistence and mobility
data. The data elements used in scoring
magnitude follow:
• Median value of detections from
finished water systems (PWSs) (national
scale data)
• Median value of detections from
ambient water sites or samples (national
scale data)
• Amount of pesticide applied
(annual, in pounds)
• Amount of total releases (annual, in
pounds)
• Persistence and mobility data
EPA developed attribute scoring
protocols through a step-wise process of
data selection, data analysis, calibration
of scales, and evaluation of the
functionality of the scores in PCCL to
CCL decision-making. This is discussed
in more detail in the report entitled
"Contaminant Candidate List 3
Chemicals: Classification of the PCCL to
the CCL" (USEPA, 2008 c). EPA used
the attribute protocols to normalize the
data for the PCCL chemicals and
develop a set of scores for the four
attributes that are the input into the
models. By normalizing the data
elements, EPA developed a process that
can use different kinds of data and
information (e.g., quantitative and
descriptive) to develop input to the
models and provide a relative score for
potential contaminants using the
attribute scores.
b. Training Data Set for the
Classification Models
The training data set (TDS) for
chemicals is the set of data used to train
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(or teach) the classification models to
mimic EPA expert list-not list decisions
for PCCL chemicals. EPA compiled this
data set in addition to the two learning
sets to represent the types of chemicals
likely to move forward to the PCCL.
This data set also represents the range
of possible attribute Scores and listing
decisions needed to train and calibrate
the classification models. The TDS used
to train the models for CCL 3 was
comprised of 202 discrete sets of
attribute scores for chemicals and
consensus list-not list decisions made
by a team of EPA subject matter experts.
Classification models use statistical
approaches for pattern recognition and
derive mathematical relationships
among input variables (e.g.,
measurements or descriptive data) and
output from a TDS. EPA used
classification models to develop a
relationship between the contaminant
attribute scores (input variables) and the
classification of these contaminants into
list-not list categories (output). EPA
subject matter experts familiar with the
technical aspects of the attribute data
and the selection of drinking water
contaminants for listing and regulation
made the list-not list decisions for the
TDS. EPA then applied the models to
the PCCL to predict likely list-not list
decisions.
EPA considered the following key
factors in developing the training data
set:
• Selection of contaminants
representing a range of outcomes and
decisions likely to be encountered in
developing a CCL;
• A variety of input data ensuring
adequate coverage of attribute scores
and combinations of scores;
• Chemicals that, when present in
drinking water, would present a
meaningful opportunity for public
health improvement if regulated; and
• Contaminants that would likely be
selected for the PCCL.
The TDS used for training the
classification models consisted of 202
combinations of attribute scores and the
decisions made by EPA experts. The
TDS included some of the contaminants
from the learning sets used in
developing the scoring protocols for
toxicity and occurrence. It also included
additional contaminants to meet the key
factor requirements described above.
The set of known chemicals chosen for
the TDS was supplemented with a set of
attribute scores and decisions that were
selected to balance the range of scored
attributes the classification model
would need to evaluate as described
further below.
Initially, EPA selected "data rich"
contaminants from among regulated
contaminants and previous CCLs
because they had a range of readily
available occurrence and health effects
information. EPA drinking water subject
matter experts and stakeholders
reviewed the initial list of contaminants
and identified additional candidates for
the TDS. This initial selection process
identified 51 chemical contaminants.
Subsequently, EPA randomly chose 50
contaminants from chemicals in the
CCL 3 Universe with high health effects
potency values and accompanying
occurrence data because they
represented contaminants likely to make
it to the PCCL. The addition of these 50
contaminants resulted in 101
contaminants with data to score
attributes.
The performance of the classification
models using the initial TDS gave an
indication of gaps in the possible
attribute space that the set of 101 TDS
contaminants did not adequately cover.
This led EPA to add the sets of possible
attribute scores to the TDS based on
Latin hypercube sampling (NIST, 2006;
http://www.itl.nist.gov/div898/
handbook/glossary.htm#LHC). Using
this approach, EPA added 101 specific
combinations of attribute scores to fill in
gaps in the space defined by total
possible attribute scores and improve
the performance of the models. This set
of 202 scores and decisions ensured
good coverage of both "list" and "not
list" outcomes and became the TDS.
Models trained with the TDS with 202
decisions had greater agreement with
EPA subject matter experts than those
trained with the TDS of 101
contaminants.
List-not list decisions were a key
component of the TDS. EPA subject
matter experts made list-not list
decisions as individuals and as a group,
based on attribute scores and based on
data that had not been converted to
attribute scores (actual or raw data). The
development of the list-not list
decisions was an iterative process that
incorporated revisions to the attribute
scoring protocols as experience was
gained by the EPA experts. EPA
resolved differences between the
decisions based on the scored attributes
and the raw data by revising the scoring
protocols based on the EPA experts'
experience to improve the correlation of
decisions based on scores to those based
on raw data.
EPA subject matter experts reviewed
and evaluated the health effects and
occurrence data for each contaminant.
Each individual reviewer made
decisions about how to classify the
contaminant and then met as a group to
discuss their decisions. Early in the
process the reviewers recognized that
clear list or not-list decisions could
easily be made for some contaminants,
but not for other contaminants. For the
chemicals where the decision whether
to list contaminants was not clear, two
categories were added to the analyses.
The categories of List? (L?) or Not List?
(NL?) allowed the group to identify
chemicals that were close to the
boundary for a List-Not List decision.
That is L? signifies that the decision is
leaning towards listing but with some
uncertainty, and NL? signifies that the
decision is leaning towards not listing
but with some uncertainty. These
additional two categories were
incorporated into the evaluation and
model training process.
The EPA subject matter experts also
reached a consensus decision for each
contaminant. This consensus decision
was used to train the models. This is
discussed in more detail in the report
entitled "Contaminant Candidate List 3
Chemicals: Classification of the PCCL to
the CCL" (USEPA, 2008c).
c. Evaluation of Classification Models
EPA identified several different
models for possible use in selecting
contaminants from the PCCL for the
CCL: Artificial neural networks,
classification decision trees, linear
models, and multivariant adaptive
regression splines. EPA evaluated the
classification models in a two-step
process. The first step was the
evaluation and selection of models from
within each of the model classes that
best predicted the consensus decisions
of the subject matter experts. The
second step was the evaluation of the
performance of the best models selected
from each class (USEPA, 2008c).
EPA evaluated models based on the 4
attributes that the model was able to
consider, the types of relationships or
mathematical functions that the model
utilized, and the model's ability to
predict classifications of the TDS. The
iterative training process minimized the
model's predictive error, thereby
reducing incorrect model predictions.
EPA also evaluated the impact of the
attributes used by the models and the
effects of missing data on the
performance of the models during the
various stages of development.
EPA evaluated the performance of five
models. Three models, Artificial Neural
Network (ANN), Quick, Unbiased and
Efficient Statistical Tree (QUEST), and
Linear Regression demonstrated
consistent performance when trained
and evaluated with the TDS. The
classification models were assessed and
compared with respect to:
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9643
• The number of correct and incorrect
classifications for the 202 TDS
contaminants.
• The number of "large"
misclassifications (off by more than one
category).
• The weighted sum of TDS
classification errors.
• Ability to identify intermediate
classifications.
• Consistent behavior (e.g., no
decreasing classification as attribute
scores increase).
This is discussed in more detail in the
report entitled "Contaminant Candidate
List 3 Chemicals: Classification of the
PCCL to the CCL" (USEPA, 2008c).
d. Application and Use of Model Results
From the inception of the
development of the CCL classification
process, EPA intended to use
classification models as decision
support tools. It was envisioned that the
models would be used to process
complex data in a consistent, objective,
and reproducible manner and provide a
prioritized listing of contaminants,
allowing EPA to focus resources on the
expert review and evaluation of the
highest priority potential contaminants.
The ANN, Linear, and QUEST models
are three different classes of models,
with three different mathematical
approaches, yet they all provided
similar results and logical
determinations. EPA explored simple
ways to combine the results of all three
models, to capture both agreement
among models and unique results. Both
a straightforward, additive approach,
and a collective, rank-order approach
were utilized to provide a prioritized
listing of contaminants to be considered
further and evaluated for possible
inclusion on the draft CCL 3.
e. Model Outcome and Expert
Evaluation
In the last step of the process, the
chemicals on the PCCL were scored for
their attributes and evaluated by the
three models. Some of the contaminants
on the PCCL had limited data available
for the scoring protocols and could not
be run through the models. The 32
contaminants that had limited data are
identified in the appendixes to the
"Classification of the PCCL to the CCL"
support document (EPA 2008c) and will
remain on the PCCL until new data are
identified for further evaluation. As part
of the evaluation of model output, EPA
formulated several post-model
refinements that were added to the CCL
selection process. Exhibit 11 illustrates
the results of the model output for the
PCCL contaminants. The PCCL
consisted of chemicals with variable
health effects data, ranging from
reference doses (RfD) to Lethal Dose 50s
(LD50), and occurrence data ranging
from measured water concentration data
from Public Water Systems (PWS) to
production volume data.
EXHIBIT 11.—MODEL RESULTS FOR THE PCCL CHEMICALS
3-Models decision
L
L-L'
L?
NL'-L' ...
ML?
NL'-NL
NL
N (all) ...
% of PCCL
9
12
33
6
28
4
9
100
Total #
PCCL
44
58
163
30
139
20
46
500
Finished or
ambient
water
3
9
26
6
29
7
21
101
Release
24
29
64
11
28
9
7
172
Production
17
20
73
13
82
4
18
227
Four of the seven decision categories,
L, L?, NL?, NL, in the first column of
Exhibit 11 signify that all of the models
were in unanimous agreement with the
listing decision. The other categories
(e.g., NL?—L?) represent varied
agreement where one or two of the
models chose one category and the other
model(s) resulted in a different category.
Note that none of the models placed a
contaminant in a category more than
one category higher or lower than the
other models. That is, no contaminants
were categorized as "L" by one model
and as "NL?" by one of the other
models, or visa versa. The models
categorized approximately one-half of
the chemicals on the PCCL as L? or
above. When analyzed by data type, the
majority of chemicals in the List
category used LD50 data for health
effects. This was a concern and became
an important issue for consideration.
The role LD50 played in the health
effects scoring was discussed
extensively during the post-model
evaluation process.
As part of the last stage in the CCL
classification process, the model output
was reviewed by a group of internal
EPA experts representing several offices.
This step involved a detailed review of
the data used for the models and the
available supplemental data for the
chemicals. The EPA experts also
deliberated on the method of using the
model data to produce a draft proposal
for CCL 3. The function of this review
was to critically compare the results
from the model to the data for the
chemicals for a cross section of the
modeled contaminants.
Based upon issues identified by the
evaluators, several post model
refinements were added to the CCL
process. Three major issues and
refinements are described below.
The relationship between potency and
concentration was important when
deciding whether to list a chemical.
However this ratio could only be
developed when water concentration
data were available. Accordingly,
calculation of the ratio between the
health-based value and the 90th
percentile concentration in finished or
ambient water was added as a post-
model process. The potency/
concentration ratio serves as a
benchmark that suggests a greater
concern for a contaminant if the ratio is
low and a lesser concern when it is
high.
The addition of modeled occurrence
data for pesticides and estimated
concentration in surface and ground
water was obtained from the EPA Office
of Pesticide Programs (OPP). The
modeled estimates of concentration in
water for pesticides are part of the EPA's
pesticide registration and re-registration
evaluations. Once the availability of the
OPP data for some of the pesticides was
confirmed, the data were extracted from
OPP documents and used to generate a
potency/concentration ratio similar to
that used with the water concentration
data.
Data certainty was factored into the
decision process by characterizing
health effect and occurrence data
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elements and their relative certainty
based upon the type of data that was
used to score the attribute for the model
classification. This characterization
tagged data elements with high certainty
and low certainty. The combined
certainty measure for a single
contaminant (i.e., health effects and
occurrence tags) was used to place
contaminants in bins of high, medium
and low certainty.
The high certainty bin consisted of
chemicals with direct occurrence
measured in water and well-studied
data for health effects. Such
contaminants are expected to be good
candidates for regulatory determination
because they provide information that
can be considered in that process and
have minimal research needs. Examples
of the data used to characterize
chemicals in the high certainty bin
include chemicals with RfDs, LOAELs,
and NOAELs, and water concentration
data. The medium bin consists of
chemicals that will need further
occurrence and/or health effects
research. For example, chemicals with
well studied health effects that only
have environmental release data are
included in the medium bin. Chemicals
that are released to the environment and
need further health effects research are
also included in the medium bin. The
low certainty bin consists of chemicals
that have limited data, yet these data
suggest that further evaluation should
be pursued. These chemicals may need
extensive health effects and occurrence
research that may require significant
resources before regulatory
determinations can be made. Examples
include chemicals with only LD50 and/
or production volume data. The CCL
should consist both of chemicals that
provide sufficient data to support
regulatory determinations as well as
chemicals that are of concern and need
to be targeted for additional drinking
water research. Contaminants from each
bin were scrutinized separately in
selecting which ones should be listed on
the CCL 3.
4. Selection of the Draft CCL 3—
Chemicals
The chemicals for the draft CCL 3
were selected from within the three
certainty bins with the emphasis placed
on the source of the occurrence data
(e.g., measured concentrations, release,
and production). Four groups of
chemicals were placed on the CCL
based on their modeled scores, the
potency-concentration ratios, where
available, and the estimate of data
certainty. They included:
• 36 chemicals in the high certainty
bin with finished or ambient water data
and a potency/90th percentile
concentration ratio <10.
• 24 pesticide chemicals in the
medium certainty bin with modeled
surface and/or ground water data that
yielded a potency/concentration ratio
<10.
• 27 chemicals in the medium
certainty bin with release data that gave
modeled L or L-L? rankings.
• 8 chemicals in the low certainty bin
that were added to the CCL as
recommended by the public in response
to EPA's Federal Register notice (71 FR
60704, USEPA, 2006b). The notice
requested that the public submit
chemical and microbial contaminant
nominations that should be considered
for CCL 3. This process is discussed in
section III.C.l.
The potency and concentration were
compared to develop a ratio that was
used to select contaminants 'for the draft
CCL 3 from the high certainty bin. A
ratio between the health-based value
and the 90th percentile was taken for
chemicals with measurements in
finished and ambient water.
Contaminants for this bin were selected
for the draft CCL 3 when the ratio was
<10, representing occurrence in water at
a level of concern related to its health
effects data.
The pesticides in the medium bin,
where modeled data was obtained from
OPP, were selected for the draft CCL 3
based on their potency/concentration
ratios. Similar to the chemicals in the
high certainty bin, pesticides were
selected for the draft CCL 3 when the
potency/concentration ratio was <10,
representing potential occurrence in
water at a level of concern related to its
health effects data. The other chemicals
in the medium bin were selected for the
draft CCL 3 based on a review of their
data and their prioritization from the
classification models.
Chemicals in the low certainty bin
were selected for the draft CCL 3 based
on a review of their supplemental data
and the data submitted through the
nominations process. Some of the
chemicals identified through the
nominations process were already on
the draft CCL 3 based on the data EPA
collected for the universe. The
supplemental data provided with the
nominations were used to screen the
nominated chemicals and score the
attributes for those that passed the
screen. The scored attributes were then
processed through the models and the
post-model evaluations. Those that were
listed demonstrated adverse health
effects and a potential to occur in PWSs.
Chemicals not selected for the draft CCL
3 will remain on the PCCL until
additional occurrence or health effects
data become available to support their
reevaluation.
B. Classification Approach for Microbial
Contaminants
As discussed in CCL 2 (USEPA,
2005b), the Agency evaluated the
NDWAC, NRC and other
recommendations, and used the
information to develop a pragmatic
approach for classifying the
microorganisms on the draft CCL 3. The
CCL 3 approach for microbes, like the
approach used for chemicals, uses the
attributes of occurrence and health
effects to select the microbial
contaminants. EPA's objective is to
target microorganisms with the highest
potential for human exposure and the
most serious adverse health effects.
Parallel to the chemical selection
process, the Agency considers a broad
universe of microbial contaminants and
systematically narrows that universe
down to develop the draft CCL 3 in a
transparent and scientifically sound
CCL process. The first step of the CCL
3 approach for microbes identifies a
universe of potential drinking water
contaminants. The second step screens
that universe of microbiological
contaminants to a Preliminary
Contaminant Candidate List (PCCL).
Lastly, EPA selects the draft CCL 3
microbial list by ranking the PCCL
contaminants based on occurrence in
drinking water (including waterborne
disease outbreaks) and human health
effects.
1. Developing the Universe
EPA defined the microbial Universe
for the draft CCL 3 as all known human
pathogens. The Universe process began
with the list of 1,415 recognized human
pathogens compiled by Taylor et al.
(2001). The Agency added organisms to
the Universe and updated nomenclature
in Taylor et al. (2001) to account for
emerging pathogens and new taxonomy
research.
As EPA reviewed Taylor et al. (2001),
additional pathogens were also
identified. EPA surveyed fungi in
drinking water and identified six fungi
reported to occur in drinking water
distribution systems that did not appear
on the Taylor list. The added fungi are
shown in Exhibit 12. EPA also added
reovirus to the Universe based on
additional health effects information
(Tyler, et al., 2004).
In October 2006, EPA published a
notice (71 FR 60704 (USEPA, 2006b))
requesting chemical and microbial
contaminant nominations as part of the
process to identify emerging
contaminants that should be considered
for the CCL. As a result of the
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9645
nominations process, 24 microbial
contaminants were nominated by the
public. Twenty-two of the microbes
were previously identified by Taylor et
al. (2001) and are already in the
Universe. The two additional pathogens
nominated were Methylobacterium
(with two species) and Mimivirus.
These two bacterial species, two viral
groups and six fungal species were
added to the Microbial Universe which
brings the Microbial Universe list to
1,425 pathogens. The full Universe list
is available in the document,
"Contaminant Candidate List 3
Microbes: Identifying the Universe"
(USEPA, 2008d).
EXHIBIT 12.—FUNGI ADDED TO THE
MICROBIAL UNIVERSE
Pathogen
Arthrographis kelrae
Chryosporium zontatum
Geotrichum candidum
Sporotrichum pruinosum
Stachybotrys chartarum
Stemphylium macrosporoldeum
2. The Universe to PCCL
EPA developed screening criteria to
reduce the Universe of all human
pathogens to just those pathogens that
could be transmitted through drinking
water. For example, pathogens
transmitted solely by animals, such as
the virus that causes rabies, were
screened out of the Universe and are not
included on the PCCL. Screening is
based on a pathogen's epidemiology,
geographical distribution, and biological
properties in their host and in the
environment. EPA moved pathogens
forward to the PCCL if there was any
evidence linking a pathogen to a
drinking water-related disease. The
screening criteria restrict the microbial
PCCL to human pathogens that may
cause drinking water-related diseases
resulting from ingestion of, inhalation
of, or dermal contact with drinking
water. EPA used 12 screening criteria
(Exhibit 13) to reduce the pathogens in
the microbial CCL universe to the PCCL.
EXHIBIT 13.—CCL SCREENING CRITERIA FOR PATHOGENS
1. All anaerobes.
2. Obligate intracellular fastidious pathogens.
3. Transmitted by contact with blood or body fluids.
4. Transmitted by vectors.
5. Indigenous to the gastrointestinal tract, skin and mucous membranes.
6. Transmitted solely by respiratory secretions.
7. Life cycle incompatible with drinking water transmission.
8. Drinking water-related transmission is not implicated.
9. Natural habitat is in the environment without epidemiological evidence of drinking water-related disease.
10. Not endemic to North America.
11. Represented by a pathogen for the entire genus or species (that are closely related).
12. Current taxonomy changed from taxonomy used in Universe.
Pathogens meeting any single
criterion of the 12 criteria were removed
from further consideration and not
moved forward to the PCCL. Based upon
this screening exercise, 1,396 of the
1,425 pathogens were excluded and 29
pathogens moved on to the PCCL. The
results of the screening process are
summarized in Exhibit 14. The
screening criteria and results of the
screening process are discussed in
greater detail in the supporting
document titled "Contaminant
Candidate List 3 Microbes: Screening to
the PCCL" (USEPA, 2008 e).
EXHIBIT 14.—APPLICATION OF TWELVE SCREENING CRITERIA TO PATHOGENS IN THE MICROBIAL CCL UNIVERSE
Pathogen class
Protozoa
Helminths
Total
Total
540
219
66
287
313
1,425
Screening Criteria
1
125
0
0
0
0
125
2
14
0,
0
0
0
14
3
10
26
1
0
0
37
4
37
104
29
25
0
195
5
117
0
3
0
12
132
6
7
19
0
0
1
27
7
0
1
4
106
0
111
8
29
18
7
0
0
54
9
154
0
7
0
297
458
10
2
36
0
156
0
194
11
28
8
6
0
0
42
12
5
0
0
0
0
5
Pathogens
screened
out
528
212
57
287
310
1,394
On PCCL
12
7
7*
0
3
29'
'Two additional protozoa,Cryptosporidium and Giardia were not considered for CCL 3 and they are discussed in more detail later.
3. The PCCL to Draft CCL Process
Pathogens on the PCCL were scored
for placement on the draft CCL. EPA
devised a scoring system to assign a
numerical value to each pathogen on the
PCCL.
Each of the pathogens on the PCCL
was scored using three scoring
protocols, one protocol each for
waterborne disease outbreaks (WBDO),
occurrence in drinking water, and
health effects. The higher of the WBDO
score or the occurrence score is added
to the normalized health effects score to
produce a composite pathogen score.
Pathogens receiving high scores were
considered for placement on the CCL.
EPA normalized the health effects
score so that occurrence and health
effects have equal value in determining
the ranking of the CCL. The equal
weighting of occurrence and health
effects information closely mirrors the
risk estimate methods used by EPA
during drinking water regulation
development. This scoring system
prioritizes and restricts the number of
pathogens on the CCL to only those that
have been strongly associated with
drinking water-related disease.
Pathogens that scored low will remain
on the PCCL until additional occurrence
data, epidemiological surveillance data,
or health effects data become available
to support their revaluation. It is
important to note that pathogens for
which there are no data documenting a
waterborne disease outbreak in drinking
water earn a low score under the
protocols. EPA believes that pathogens
that have caused a WBDO and have
health effects data should rank higher
than pathogens that have only data on
health effects but no evidence of a
WBDO. The following sections describe
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Federal Register/Vol. 73, No. 35/Thursday, February 21, 2008/Notices
the three protocols used to score the
pathogens on the PCCL and the process
by which the scores are combined.
a. Waterborne Disease Outbreak
Protocol
The Centers for Disease Control and
Prevention (CDC), EPA and the Council
of State and Territorial Epidemiologists
(CSTE) have maintained a collaborative
surveillance system for collecting and
periodically reporting data related to
occurrences and causes of WBDOs since
1971. EPA used the CDC surveillance
system as the primary source of data for
the waterborne disease outbreaks
protocol. Reports from the CDC system
are published periodically in Morbidity
and Mortality Weekly Report (MMWR).
For this protocol (Exhibit 15), a
pathogen is scored as having a WBDO(s)
in the U.S. if that pathogen is listed in
a CDC waterborne disease drinking
water surveillance summary (i.e., in the
MMWR). A pathogen with multiple
WBDOs listed by CDC is given the
highest score under this protocol. EPA
also scored non-CDC reported WBDOs
and WBDOs outside the U.S. as well;
however these were given lower scores.
WBDOs outside the U.S. were scored
when information was available from
World Health Organization publications
or other peer-reviewed publications.
In addition, CDC and EPA
acknowledge that the WBDOs reported
in the surveillance system represent
only a portion of the burden of illness
associated with drinking water exposure
(CDC, 2004). The surveillance
information does not include endemic
waterborne disease risks, nor are
reliable estimates available of the
number of unrecognized WBDOs and
associated cases of illness. Therefore,
EPA also considered data as indicating
a WBDO (even though CDC does not list
a WBDO in their MMWR) if the non-
CDC data showed a link between human
illness defined by a common water
source, a common time period of
exposure and/or similar symptoms. EPA
also considered the use of molecular
typing methods to link patients and
environmental isolates.
Only two pathogens were given a
WBDO score on this basis,
Mycobacterium avium and Arcobacter
butzlerei. They are discussed in greater
detail in the "Contaminant Candidate
List 3 Microbes: PCCL to CCL Process"
(USEPA, 2008 f).
EXHIBIT 15.—WATERBORNE DISEASE
OUTBREAK SCORING PROTOCOL
. Category
Has caused multiple (2 or
more) documented WBDOs
in the U.S. since CDC sur-
veillance initiated in 1973
Has caused at least one docu-
mented WBDO in the U.S.
since CDC surveillance initi-
ated in 1973
Has caused documented
WBDOs at any time in the
U.S
Has caused documented
WBDOs in countries other
than the U.S
Has never caused WBDOs in
any country, but has been
epidemiologically associated
with water-related disease ....
Score
5
4
3
2
1
b. Occurrence Protocol
The second attribute of the scoring
process evaluates the occurrence of a
pathogen in drinking water. Because
water-related illness may also occur in
the absence of recognized outbreaks,
EPA scored the occurrence (direct
detection) of microbes using cultural,
immunochemical, or molecular
detection of pathogens in drinking water
under the Occurrence Protocol (Exhibit
16). Occurrence characterizes pathogen
introduction, survival, and distribution
in the environment. Occurrence implies
that pathogens are present in water and
that they may be capable of surviving
and moving through water to produce
illness in persons exposed to drinking
water by ingestion, inhalation, or
dermal contact.
Pathogen occurrence is considered
broadly to include treated drinking
water, and all waters using a drinking
water source for recreational purposes.
This attribute does not characterize the
extent to which a pathogen's occurrence
poses a public health threat from
drinking water exposure. Because
viability and infectivity cannot be
determined by non-cultural methods,
the public health significance of non-
cultural detections is unknown.
EXHIBIT 16.—OCCURRENCE
SCORING PROTOCOL FOR PATHOGENS
Category
Detected in drinking water in
the U S
Detected in source water in the
U.S
Not detected in the U.S
Score
3
2
1
c. Health Effects Protocol
EPA's health effects protocol
evaluates the extent or severity of
human illness produced by a pathogen
across a range of potential endpoints.
The seven-level hierarchy developed for
this protocol (Exhibit 17) begins with
mild, self-limiting illness and progresses
to death.
The final outcome of a host-pathogen
relationship resulting from drinking
water exposure is a function of viability,
infectivity, and pathogenicity of the
microbe to which the host is exposed
and the host's susceptibility and
immune response. SDWA directs EPA to
consider subgroups of the population at
greater risk of adverse health effects
(i.e., sensitive populations) in the
selection of unregulated contaminants
for the CCL. Sensitive populations may
have increased susceptibility and may
experience increased severity of
symptoms, compared to the general
population. SDWA refers to several
categories of sensitive populations
including the following: children and
infants, elderly, pregnant women, and
persons with a history of serious illness.
Health effects for individuals with
marked immunosuppression (e.g.,
primary or acquired severe
immunodeficiency, transplant
recipients, individuals undergoing
potent cytoreductive treatments) are not
included in this health effects scoring.
While such populations are considered
sensitive subpopulations,
immunosuppressed individuals often
have a higher standard of ongoing
health care and protection required than
the other sensitive populations under
medical care. More importantly, nearly
all pathogens have very high health
effect scores for the markedly
immunosuppressed individuals;
therefore there is little differentiation
between pathogens based on health
effects for the immunosuppressed
subpopulation.
This protocol scores the
representative or common clinical
presentation for the specific pathogen
for the population category under
consideration. EPA used recently
published clinical microbiology
manuals as the primary data source for
the common clinical presentation.
These manuals take a broad
epidemiological view of health effects
rather than focusing on narrow research
investigations. The one exception to this
approach was EPA's scoring of health
effects for Helicobacter pylori. H. pylori
is discussed in greater detail in section
IV.C as well as in the support document,
"CCL 3 Microbes: PCCL to CCL Process"
(USEPA, 2008 f).
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9647
To obtain a representative
characterization of health effects in all
populations, EPA evaluated separately
the general population and these four
sensitive populations as to the common
clinical presentation of illness for that
population. EPA added the general
population score to the highest score
among the four sensitive subpopulations
for an overall health effects score. The
resulting score acknowledges that
sensitive populations have increased
risk for waterborne diseases.
EXHIBIT 17.—HEALTH EFFECTS SCORING PROTOCOL FOR PATHOGENS
Outcome category
Does the organism cause significant mortality (> 1/1,000
cases)?.
Does the organism cause pneumonia, meningitis, hepatitis,
encephalitis, endocarditis, cancer, or other severe mani-
festations of illness necessitating long term hospitalization
(> week)?.
Does the illness result in long term or permanent dysfunction
or disability (e.g., sequelae)?.
Does the illness require short term hospitalization? (< week)?
Does the illness require physician intervention'
Is the illness self-limiting within 72 hours (without requiring
medical intervention)?.
Does the illness result in mild symptoms with minimal or no
impact on daily activities?.
Score
7
6
5
4
3
2
1
Manifestation in population class
General
population
Children/
infants
Elderly
Pregnant
women
Chronic
disease
d. Combining Protocol Scores to Rank
Pathogens
EPA scored and ranked the PCCL
using the three attribute scoring
protocols, occurrence, waterborne
disease outbreaks, and health effects.
These protocols are designed in a
hierarchical manner so that each
pathogen is evaluated using the same
criteria and the criteria range for each
protocol varies from high significance to
low significance. The three attribute
scores are then combined into a total
score.
EPA scored pathogens first using the
WBDO and occurrence protocols, and
then selected the highest score.
Selection of the higher score from the
WBDO or occurrence protocol elevates
pathogens that have been detected in
drinking water or source water in the
U.S. (occurrence score of 2 or 3) above
pathogens that have caused WBDOs in
other countries but not in the U.S.
(WBDO score of 2).
The CCL selection process considered
pathogens causing recent waterborne
outbreaks more important than
pathogens detected in drinking water
without documented disease from that
exposure. Direct detection of pathogens
indicates the potential for waterborne
transmission of disease. Documented
waterborne disease outbreaks provide
an additional weight of evidence that
illness was transmitted and that there
was a waterborne route of exposure.
EPA developed protocols to define a
hierarchy of the relevance that each of
these types of data provide in evaluating
microbes for the CCL. Combining these
two sources of occurrence information
enabled EPA to consider both emerging
pathogens, which are detected in water
and should be considered, yet are not
tracked by public health surveillance
programs, and those pathogens with
WBDO data. This hierarchy also
acknowledges that organisms identified
as agents in WBDO are a higher priority
for the CCL.
Next, pathogens were scored using the
Health Effects Protocol. All five
population categories were scored for
each pathogen using the most common
clinical presentation for the specific
pathogen for the population category
under consideration. Because it is
recognized that pathogens may produce
a range of illness from asymptomatic
infection to fulminate illness
progressing rapidly to death, scoring
decisions are based upon the more
common clinical presentation and
clinical course for the population under
consideration, rather than the extremes.
EXHIBIT 18.—PATHOGENS ON THE PCCL
The pathogen's score for the general
population is added to the highest score
among the four sensitive populations to
produce a sum score between 2 and 14.
Finally, EPA normalizes the Health
Effects and WBDO/Occurrence score
because the Agency believes they are of
equal importance. The highest possible
score for WBDO/Occurrence is 5 and the
highest possible Health Effect score is
14. To equalize this imbalance, the
Agency multiplies the health effects
score by 5/i4. Combining health effects
data with the WBDO/occurrence data by
adding the scores from these protocols
provides a system that evaluates both
the severity of potential disease and the
potential magnitude of exposure
through drinking water.
Exhibit 18 presents the scores for all
the PCCL pathogens with the exception
of Giardia and Cryptosporidium. These
two protozoan pathogens made it
through the screening protocol,
however, EPA chose not to score or
include them on the PCCL because EPA
has recently published a national
primary drinking water regulation that
specifically addresses these pathogens
(January 4, 2006, 71 FR 388 (USEPA,
2006 a) and is discussed in more detail
later.
Pathogen
Naegleria fowleri
Legionella pneumophila
Escherichia co//(0157)
WBDO
4
5
5
Occurrence
3
3
3
Normalized
health score
5 0
3 6
3.2
Total1 score
9 0
8 6
8.2
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EXHIBIT 18.—PATHOGENS ON THE PCCL—Continued
Pathogen
Hepatitis A virus
Shigella sonnei
Helicobacter pylori
Campylobacter jejuni
Salmonella enterica
Caliciviruses
Entamoeba histolytica
Vibrio cholerae ....
Adenovirus
Enterovirus
Cyclospora cayetanensis
Mycobacterium aviunt
Rotavirus
Yersinia enterocolitica
Arcobacter butzleri
Fusariufn solani
Plesiomonas shigelloides
Hepatitis E virus
Toxoplasma gondii .
Aspergillus fumigatus group . ...
Exophiala jeanselmei
Aeromonas hydrophila
Astrovirus
Microsporidia
Isospora belli
Blastocvstis hominis
WBDO
5
5
1
5
5
5
5
5
2
2
4
4
4
5
4
1
4
2
2
1
1
1
2
1
2
1
Occurrence
2
3
3
3
3
3
3
3
3
3
1
3
2
3
3
3
3
1
1
3
3
3
2
2
0
0
Normalized
health score
32
32
50
2.5
25
2.1
2 1
2 1
3.6
36
2.5
25
2.5
1 4
2.1
29
1.8
3.6
32
2 1
2 1
1.8
1.4
1.4
1.1
0.7
Total1 score
82
82
80
7.5
75
7.1
7 1
7 1
6.6
66
65
65
6.5
64
6.1
5 9
58
5.6
5.2
5 1
5 1
4.8
3.4
3.4
3.1
1.7
1. Total Score = Normalized Health Score + the higher of WBDO or Occurrence scores.
e. Other Criteria Considered for Listing
and Scoring Microbes on the Draft
CCL3
i. Organisms Covered by Existing
Regulations
EPA considered an additional
screening criterion based upon
contaminants that might be controlled
through drinking water monitoring
requirements under the Total Coliform
Rule (TCR) (54 FR 27544, June 29, 1989
(USEPA, 1989b)). Many of the bacteria
in the CCL Universe, including the
Enterobacteriaceae and members of the
genera Campylobacter and Vibrio, are
associated with fecal contamination and
as such their presence could be signaled
by the total coliform monitoring
requirements under current drinking
water regulations. In the TCR, EPA
chose to require monitoring for
Escherichia coli or fecal coliform (and
total coliforms) in finished drinking
water because it provides a broad
indication of the potential presence of
fecal pathogens in drinking water,
though more so for bacteria than for
viruses and protozoa.
EPA chose not to exclude common
enteric bacterial pathogens from the
PCCL even though they may be
indicated by the TCR. Numerous
waterborne disease outbreaks have
occurred in systems that were in
compliance with drinking water
monitoring requirements under the
TCR. EPA recognizes the frequency of
total coliform monitoring under the TCR
may be limited, especially for smaller
systems, thus transitory fecal
contamination could go undetected. The
recognition of these bacterial pathogens
on the CCL list will provide additional
understanding of the risks posed by
distribution systems.
The Agency is currently revising the
TCR and considering distribution water
quality issues (because of the pathways
of potential fecal contamination).
Including these pathogens on the CCL
emphasizes their importance in
protecting public health. EPA believes
that enteric pathogens should be
included for further specific regulatory
consideration in the CCL.
ii. Organisms Covered by Treatment
Technique Regulations
According to SDWA (section
1412(b)(l), as amended in 1996), EPA
must select CCL contaminants that "at
the time of publication, are not subject
to any proposed or promulgated
national primary drinking water
regulation* * *." In promulgating
regulations for contaminants in drinking
water, EPA can set either a legal limit
(MCL) and require monitoring for the
contaminant in drinking water or, for
those contaminants that are difficult to
measure, EPA can establish a treatment
technique requirement. The Surface
Water Treatment Rule (SWTR) (54 FR
27486, June 29,1989 (USEPA, 1989a))
included MCLGs for Legionella, Giardia,
and viruses at zero because any amount
of exposure to these contaminants
represents some public health risk.
Since measuring disease-causing
microbes in drinking water is not
considered to be feasible, EPA
established treatment technique
requirements for these contaminants.
The purpose of subsequent treatment
technique requirements (Interim
Enhanced Surface Water Treatment Rule
(63 FR 69478; USEPA 1998a), Long
Term Surface Water Treatment Rule 1
(67 FR 1813; USEPA, 2002a) and the
Long Term Surface Water Treatment
Rule 2 (71 FR 654; USEPA, 2006a))
which included an MCLG of zero for
Cryptosporidium, is to reduce disease
incidence associated with
Cryptosporidium and other pathogenic
microorganisms in drinking water.
These rules apply to all public water
systems that use surface water or ground
water under the direct influence of
surface water.
The Ground Water Rule (71 FR 65573,
(USEPA, 2006c)) set treatment
technique requirements to control for
viruses (and pathogenic bacteria)
because it was not feasible to monitor
for viruses (or pathogenic bacteria) in
drinking water. Under the GWR, if
systems detect total coliforms in the
distribution system, they are required to
monitor for a fecal indicator (E. coli,
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9649
coliphage, or enterococci) in the source
water. If fecal contamination is found in
the source water, the system must take
remedial action to address
contamination.
While Cryptosporidium and Giardia
have been implicated in WBDOs, there
is a substantial amount of research
regarding health effects and sensitivity
to various treatment control measures.
More importantly, as noted above, EPA
has recently published a National
Primary Drinking Water Regulation, The
Long Term 2 Surface Water Treatment
Rule that specifically addresses these
pathogens (71 FR 654 (USEPA, 2006a)).
Therefore, they are excluded from the
CCL.
EPA did not exclude specific viruses
and Legionella from consideration for
the CCL even though they have broad
category MCLGs and treatment
technique requirements. Viruses include
a wide range of taxa. The treatment and
health effects information for different
viral taxa was very limited when setting
the treatment technique requirements
for surface water and ground water
systems. Also, different viral taxa have
been implicated in various waterborne
disease outbreaks for which EPA did not
have dose response or treatment data
when promulgating its treatment
technique requirements. Legionella has
recently been identified in numerous
WBDOs (e.g., CDC MMWR reports,
2006). Additionally EPA received
additional information on the
occurrence of Legionella in distribution
systems as part of the nominations
process (USEPA 2008g). Therefore EPA
included viruses and Legionella on the
draft CCL 3.
iii. Applying Genomic and Proteomic
Data to Microbes
The Agency and NDWAC workgroup
evaluated the possibility of using
genomics and proteomics as data to
identify emerging waterborne
pathogens, opportunistic
microorganisms, and other newly
identified microorganisms. While the
application of these data in identifying
genetic properties that may be
pathogenic is a powerful tool for the
elucidation of pathogenic mechanisms,
the technology is yet largely unproven
and the Agency has decided at this time
not to use these techniques for CCL
application. However, the Agency is
monitoring the progress of these
technologies and as the data improve
and genomics progresses the Agency
may consider them for future CCL
development.
4. Selection of the Draft CCL 3 Microbes
From the PCCL
The 29 PCCL pathogens in Exhibit 18
are ranked according to an equal
weighting of their summed scores for
normalized health effects and the higher
of the individual scores for WBDO and
occurrence in drinking water. EPA
believes this ranking indicates the most
important pathogens to consider for the
draft CCL 3. To determine which of the
29 PCCL pathogens should be the
highest priority for EPA's drinking
water program and included on the draft
CCL 3, the Agency considered both
scientific and policy factors. The factors
included the PCCL scores for WBDO,
occurrence, and health effects;
comments and recommendations from
the various expert panels; the specific
intent of SDWA; and the need to focus
Agency resources on pathogens to
provide the most effective opportunities
to advance public health protection.
After consideration of these factors, EPA
has determined that the draft CCL 3 will
include the 11 highest ranked pathogens
shown in Exhibit 18.
Additionally, the Agency notes that,
and as can be observed in Exhibit 18,
there are a few "natural" break points in
the ranked scores for the 29 pathogens,
with the top 11 forming the highest
ranked group of pathogens. EPA does
believe that the overall rankings
strongly reflect the best available
scientific data and high quality expert
input employed in the CCL selection
process, and therefore should be
important factors in helping to identify
the top priority pathogens for the draft
CCL 3.
C. Public Input
1. Nominations and Surveillance
On October 16, 2006, EPA published
a Federal Register notice (71 FR 60704
(USEPA, 2006 b)) requesting the public
to submit chemical and microbial
contaminant nominations that should be
considered for CCL 3. EPA evaluated
nominated contaminants to identify the
data supporting their nomination. This
section describes EPA's request for
contaminants and summarizes the
nominations received by EPA. A more
detailed discussion of the contaminants,
including a list of the specific
contaminants nominated, can be found
in the CCL 3 Nominations Summary in
EPA's Water Docket (USEPA, 2008 g).
The Agency sought CCL nominations
for contaminants by framing the SDWA
requirements in a series of questions to
document the anticipated or known
occurrence in PWS(s) and adverse
health effects of potential contaminants.
The Agency requested that the public
respond to these questions and provide
the documentation and rationale for
including a contaminant for
consideration in the CCL process. The
questions posed to the public were:
—What are the contaminant's name,
CAS number, and/or common synonym
(if applicable)?
—What factors make this contaminant
a priority for the CCL 3 process (e.g.,
widespread occurrence; anticipated
toxicity to humans; potentially harmful
effects to susceptible populations (e.g.,
children, elderly and
immunocompromised); potentially
contaminated source water (surface or
ground water), and/or finished water;
releases to air, land, and/or water;
contaminants manufactured in large
quantities with a potential to occur in
source waters)?
—What are the significant health
effects and occurrence data available,
which you believe supports the CCL
requirement(s) that a contaminant may
have an adverse effect on the health of
persons and is known or anticipated to
occur in public water systems?
The Agency compiled the information
from the nominations process to
identify the contaminants nominated
and the rationale for the nomination and
to compare the supporting data to
information already gathered by EPA.
The nominations process identified
150 chemical and 24 microbial
contaminants from 11 organizations and
individuals. The organizations that
nominated contaminants are:
—American Society of Microbiology
(ASM),
—American Water Works Association
(AWWA),
—Association of Metropolitan Water
Agencies (AMWA),
—Association of State Drinking Water
Administrators (ASDWA),
—Mothers Against Acanthamoeba
Disease,
—Natural Resources Defense Council,
(NRDC),
—Ri verkeepers,
—State of New Jersey Department of
Environmental Protection,
—State of New York Department of
Health, and
—State of Texas Commission on
Environmental Quality.
Exhibit 19 summarizes the types of
nominated contaminants and who
nominated them. The complete list of
chemical and microbial contaminants
nominated can be found in EPA's Water
Docket. Some of the nominations
identified categories of contaminants
that the Agency should consider for the
CCL. There were 23 chemical groups
identified from the 150 chemical
contaminants that were nominated. For
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example, several organizations
identified pesticides that are not
currently regulated under the SDWA as
candidates for consideration. Other
groups identified by the public are
listed in Exhibit 19.
EXHIBIT 19.—SUMMARY OF CCL 3 NOMINATIONS
Nominator
ASM
AMWA
ASDWA
AWWA
Mothers Against Acanthamoeba Disease
New Jersey DEP
New York DOH
NRDC
Riverkeeper
Texas DEQ
Number of in-
dividual con-
taminants or
specific exam-
ples from
nominated
groups
2
3
14
38
1
4
24
26
52
3
Types and groups of contaminants
Mimivirus, Naegleria fowleri
Nitrosoamines and other DBPs
Disinfection byproducts (DBPs), unregulated pesticides, solvents, total petroleum
hydrocarbons, cyanotoxins, 3 perfluorinated contaminants (PFCs), viruses,
phthalates, nitrite, nitrate; endocrine disrupters.
DBPs, pesticides, 1 6 specific microbes, cyanotoxins, radium, 1 ,4-dioxane.
Acanthamoeba.
PFOS PFOA trichloropropane tertiary butyl alcohol
Pharmaceuticals personal care products, DBPs fuel oxygenates 1 4-dioxane her-
bicides, bio-monitoring data.
Alkylphenolpolyethoxylates (APEs that may be endocrine disrupter compounds
(EDC)), all unregulated pesticides, perchlorate, Mycobacterium avium complex
(MAC), phthalates, managanese, bisphenol A.
Pharmaceuticals, sodium, chloride.
Viruses nitrite nitrate
The Agency evaluated the
nominations to identify contaminants
not previously considered for the CCL
and new pertinent information provided
by the public. Nominated contaminants
were evaluated to identify and compare
supporting information provided to that
used in the CCL process. Of the 174
chemical and microbial contaminants
nominated, 152 contaminants were
already being considered by the Agency.
Seven of the nominated contaminants
are currently regulated in PWSs and
will not be included in the CCL 3
process. Most of the data sources cited
in the nominations process were already
identified for the CCL 3 process. The
nominations process did identify
recently published specialized studies
from scientific literature dial were
subsequently incorporated in the CCL 3
evaluation process.
Where new supplemental data was
provided for contaminants that had not
been identified for the draft CCL 3, EPA
used the supplemental data to screen
the nominated chemicals and score the
attributes for those that passed the
screen. EPA then processed the
nominated contaminants through the
models and the post-model evaluations.
Twenty of the contaminants identified
in the nominations process are on the
draft CCL 3.
2. External Expert Review and Input
EPA actively sought external advice
and expert input for the draft CCL 3. In
addition to their own recommendations,
the NRC and NDWAC recommended
that the Agency seek opportunities to
incorporate additional expert input in
the development of the draft CCL 3. EPA
convened several external expert panels
at integral stages during the
development of the draft CCL 3. EPA
incorporated expert judgment and input
from the scientific community into the
CCL process for both chemicals and
microbes. The Agency has requested a
consultation with the Science Advisory
Board that will take place in 2008.
For each expert panel, EPA sought
panel members that provided a variety
of disciplines and expertise. Panel
members were encouraged to provide
comments as individuals based upon
their expertise and background, not as
representatives of their respective
organizational affiliations. Expert panel
members were also encouraged to
present individual comments if
consensus comments were not
developed. Separate panels were
convened to review the draft chemical
and microbial CCL 3 lists and the
processes used to develop them. A more
detailed discussion of the chemical and
microbial expert review and input is
provided in the support documents in
the EPA Water Docket. A brief overview
of the chemical and microbial expert
review and stakeholder involvement
follows.
a. Chemical Expert Input Panels
In September of 2006, EPA formed
two external expert panels to provide
specific input into the chemical CCL 3
process. In the first panel, experts
reviewed the data sources and the
process used to identify the chemical
universe. EPA convened the second
panel for a 3-day workshop to review
the data and information used to
develop screening criteria, the data and
methodology for the classification
approach, and to provide overall input
into the CCL process. In summary, the
panels recommended that EPA consider
additional data sources in the process.
They also commented on ways to
improve and clarify the presentation of
EPA efforts, thereby ensuring that the
CCL 3 process for chemicals is more
transparent. The expert panel reviewing
the classification approach identified
additional analyses and approaches to
train and validate the models. The panel
specifically commented on the varied
nature of data elements and sources
considered in the classification process.
The panel recommended that to account
for these varied data sources,
contaminants be flagged based upon
data certainty, and that uncertainty be
considered in making a listing decision.
The Agency applied their
recommendations in the development of
the draft CCL 3. In addition, the expert
panels acknowledged the Agency's
efforts to transparently present a
complex process and noted that many of
the questions posed by .the panels were
previously considered by EPA. They
recommended that additional
discussion and information in the
support documents would add to the
clarity of the process.
In March 2007, EPA convened a panel
to review the preliminary draft CCL 3
list for the chemical contaminants in a
two-day workshop. Panelists provided
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9651
comments on a preliminary draft list of
contaminants after receiving supporting
materials and presentations from EPA
staff. The panel's review focused mainly
on the chemicals on the draft CCL 3.
They provided comments on
contaminants considered for the draft
CCL 3 and commented on the
supporting data and methods EPA used
to identify the contaminants selected.
They also provided general comments
on the classification model output and
the processes used to select chemical
contaminants for CCL 3. In addition,
they recommended EPA consider a
strong outreach process to highlight the
significant modeling and decision
making processes used in its
development.
The panel recognized the level of
effort and detail that went into the
development of the modeling process
used to create the draft list and
complimented EPA on these efforts.
Comments from all the panels were
considered by EPA and appropriate
changes were incorporated into the
process/protocols to formulate the draft
CCL 3. (Specific recommendations and
comments are further described in
USEPA, 2008h.)
b. Microbial Expert Input Panels
EPA convened three workshops to
review, discuss, and comment on the
microbes considered and selected for
the draft CCL 3. In December 2005, a
group of expert microbiologists
reviewed and commented on the
universe of human pathogens and the
screening criteria used to develop the
PCCL. This panel agreed that focusing
on human pathogens is a reasonable and
pragmatic way to identify potential
drinking water contaminants. While the
panel suggested that animal pathogens
may develop the ability to infect
humans, they noted that these emerging
contaminants should not be listed on
the CCL based on the theoretical
potential to become zoonotic pathogens.
They also identified additional criteria
and methods to apply those criteria to
the Microbial Universe, which EPA
incorporated into the CCL process.
In June 2006, a panel of experts met
for three days to review EPA's
implementation of recommendations by
NRC and NDWAC to select microbes for
the CCL. EPA implemented the NDWAC
recommendation to develop a process
that paralleled the chemical process yet
still accounted for the different types of
data and information that are uniquely
available for microbial contaminants.
Panel members agreed that health
effects and occurrence of microbes
should be evaluated to identify
pathogens of the greatest health
importance. The panel recommended
that EPA use a decision tree approach
for microbes rather than the
classification approach suggested by
NRC and NDWAC.
The panel further recommended that
the Agency consider a different
selection process than the one used for
chemical contaminants, related to the
different information available for
microbes. Based on this
recommendation, the Agency evaluated
options to consolidate the potency and
severity attributes for microbes into a
single health effect attribute, developed
a waterborne disease outbreak protocol,
and considered occurrence as a single
attribute. The Agency considered these
and other recommendations as it
developed the current three attribute
selection process discussed in Section
III.B. The panel also recommended that
the Agency consider drinking water
treatment and removing microbes from
further consideration if conventional
drinking water treatment protects public
health. The Agency's considerations of
these and other recommendations are
discussed in the Microbial Expert
Review support document (USEPA,
2008i).
In March 2007, EPA convened a third
workshop to review the preliminary
draft CCL 3 list of microbial
contaminants. EPA provided the panel
with background materials and staff
presentations. The panel's review
focused mainly on the draft CCL 3 for
microbes. The panel also provided
comments on the processes used to
select the microbial contaminants. Panel
members commented on specific
microbes considered for the draft CCL 3
and commented on the data and
processes EPA used to identify the
contaminants selected. The panel noted
that the Agency considered a
comprehensive list of microbes and
thought the draft CCL 3 was reasonable.
The panel also recommended that the
Agency consider adding a frequency of
disease parameter to the health effects
scoring protocol for future CCLs. For
example, while the panel agreed with
EPA that the health effects for Naegleria
fowleri are severe, the health effects
scoring protocol should consider the
limited occurrence of disease. The panel
also noted that this would help balance
the consideration of less severe adverse
health effects such as gastrointestinal
illness that are more prevalent with
consideration of more severe responses
that are less prevalent, such as N.
fowleri. The panel recommended that
EPA provide further discussion of the
rationale to evaluate waterborne disease
and health effects equally in the
protocol. The discussion of the Agency's
rationale is included in Section III.B and
addresses the importance of
documented waterborne disease
outbreaks to identify potential microbial
contaminants for the CCL. (A more
detailed summary of the expert
comments is provided in USEPA, 2008
i.)
3. How are the CCL and UCMR
Interrelated for Specific Chemicals and
Groups?
EPA promulgated UCMR 2 on January
4, 2007 (72 FR 367 (USEPA, 2007 a; see
also USEPA, 2007 b and c)j. The UCMR
program was developed in coordination
with the CCL. Both programs consider
the adverse health effects a contaminant
may pose through drinking water
exposures. Sixteen contaminants on the
UCMR 2 monitoring list are also on the
draft CCL 3. The draft CCL 3 includes
acetochlor and its degradates, alachlor
degradates, dimethoate, 1,3-
dinitrobenzene, metolachlor and its
degradates, RDX, terbufos sulfone, and
four of the nitrosamines. In addition to
the health effects data and potential
occurrence, the UCMR 2 also considers
analytical methods, availability of
analytical standards, and laboratory
capacity to conduct a nationwide
monitoring program in selecting
contaminants. The UCMR 2 includes
nine contaminants that are not on draft
CCL 3. The five polybrominated flame
retardants can be measured by the same
analytical method used for terbufos
sulfone. The polybrominated flame
retardants lacked sufficient occurrence
information to be listed on draft CCL 3
(USEPA 2008 b). The polybrominated
flame retardants are listed on UCMR2
because of recent concern that these
have become more widespread
environmental contaminants (e.g.,
Darnerud et al, 2001) and this
monitoring data will provide
information for future CCLs. Similarly,
2,4,6-trinitrotoluene (TNT) and two of
the nitrosamines also use an analytical
method in the UCMR 2. The Agency
will also use the results from UCMR 2
as a source of occurrence information
during the selection of CCL 4, as well as
for CCL 3 regulatory determinations.
Alachor was listed on UCMR 2, but was
removed from consideration for CCL 3
because there is an existing MCL.
IV. Request for Comment
The purpose of this notice is to
present the draft CCL 3 and seek
comment on various aspects of its
development. The Agency requests
comment on the approach used to
develop the draft CCL 3 and also
requests comments on the contaminants
selected, including any supporting data
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that can be utilized in developing the
final CCL 3. A number of contaminants
considered for the draft CCL 3 may be .
of particular current interest. The
following sections provide information
for a few of the contaminants that are of
most interest. Data obtained and
evaluated for developing the draft CCL
3 and referred to in the following
sections may be found in the docket for
this notice. Specifically, the Agency is
also asking for public comments on
Pharmaceuticals and perfluorinated
compounds to identify any additional
data and information on their
concentrations in finished or ambient
water and requests comment on how
they have been considered in the CCL
3 process. The Agency is also seeking
additional data and information on the
occurrence and health effects of H.
pylori and how this pathogen was
considered in the CCL 3 process.
Information and comments submitted
will be considered in determining the
final CCL 3, as well as in the
development of future CCLs and in the
Agency's efforts to set drinking water
priorities in the future.
A. Pharmaceuticals
The Agency evaluated data sources to
identify pharmaceuticals and personal
care products that have the potential to
occur in PWSs. The primary source of
health effects information on
pharmaceuticals in the universe was the
Food and Drug Administration Database
on Maximum Recommended Daily
Doses (MRDD). This database includes
the recommended adult doses for over
1,200 pharmaceutical agents.
Occurrence information from USGS
Toxics Substances Hydrology program's
National Reconnaissance of Emerging
Contaminants, and related efforts,
provided ambient water concentration
data for 123 contaminants, which
include pharmaceuticals. Other data
sources included TRI and high
production volume chemical data. From
this analysis, EPA included 287
pharmaceuticals in the Chemical
Universe. These pharmaceuticals had
maximum recommended daily dose
information that EPA used to evaluate
adverse health effects. EPA considered
those pharmaceuticals for which MRDD
values and occurrence information were
available and pharmaceuticals that were
in Toxicity Category 1, using the same
criteria discussed in Section III.A.2.a.
EPA found that less than two percent of
the pharmaceuticals included in the
MRDD database fell into this category.
EPA applied the LOAEL screening
protocols to contaminants with MRDD
values. The LOAEL protocol was used
because pharmaceutical agents,
although used for their beneficial
effects, have associated side-effects that
may be adverse. Chemicals evaluated
with these data had similar modal
values and distributions to the toxicity
values from IRIS. The range of toxicity
values in this database covered 9 orders
of magnitude when evaluated based on
their rounded logs. They had the same
modal value as the LOAELs from IRIS
and a very similar distribution. Thirty-
five percent of the IRIS LOAELS and 38
percent of the MRDDs had the modal
rounded log. Thirty-three percent of the
LOAELs and 19 percent MRDDs had
rounded logs that were lower than the
mode, while 31 percent of the LOAELs
and 44% of the MRDDs had rounded
logs that were above the modal log
value.
The screening process moved
approximately 10 percent of the
pharmaceuticals in the Universe to the
PCCL. All toxicity data on those
chemicals were included in the
screening with the most serious
qualitative or quantitative measure of
toxicity determining placement in a
toxicity category. Only one of the PCCL
chemicals (diazinon, a veterinary
product as well as a pesticide) had
water concentration data. Two other
pharmaceuticals: phenytoin (an
anticonvulsant) and nitroglycerin
(treatment of angina), had release data.
The remainder were scored for
occurrence based on production
information, which meant that they fell
into the low certainty bin for their
occurrence parameters. Nitroglycerin is
the only pharmaceutical that is included
on the draft CCL 3. EPA is aware of
concerns regarding the potential
presence of pharmaceuticals in water
supplies. The Agency is seeking
additional data and information on the
concentrations of pharmaceuticals in
finished or ambient water and requests
comment on how pharmaceuticals have
been considered in the CCL 3 process.
B. Perfluorooctanoic Acid and
Perfluorooctane Sulfonic Acid
EPA evaluated perfluorinated
compounds in the CCL 3 process and
requests comment on its decisions to
include perfluorooctanoic acid (PFOA)
and not to include perfluorooctane
sulfonic acid (PFOS) on the draft CCL 3.
EPA identified potential health effects
and occurrence information for these
compounds from the data sources
discussed in Section III. The data used
for these compounds are discussed in
the support documents in more detail.
Available analytic methods for these
chemicals limited the occurrence data
for these compounds. The Agency
identified data on the annual
production from CUS/IUR indicating
limited production and possible release
to the environment. Several
organizations nominated PFOS and
PFOA for consideration in the CCL
process. The nominations noted that
these chemicals are persistent in the
environment and have been detected at
varying levels in drinking water and
ambient water in smaller specialized
studies. EPA collected the information
cited in the nominations and evaluated
each of these chemicals. The Agency
included PFOA on the draft CCL 3
because it met the criteria for inclusion
on draft CCL 3 based on drinking water
occurrence studies in Ohio and West
Virginia (Emmett, et al., 2006) and on
health effects data indicated through
animal studies (USEPA, 2005 a).
The Agency did not include PFOS on
the draft CCL 3. Occurrence data for
PFOS characterized detections in
several States (Boulanger, et al., 2004,
Hansen, et al., 2002, Goeden and Kelly,
2006). These data showed that levels of
detection for PFOS in ambient water
ranged from 20 to approximately 100
parts per trillion. Data identified in the
nominations process detected PFOS at
higher concentrations in areas
surrounding landfills known to be
contaminated with industrial waste
containing PFOS. The CCL process did
not consider occurrence data from
targeted studies of contaminated waste
sites, however. Such studies are usually
developed to identify and characterize
hazardous waste cleanup efforts and
may not be representative of occurrence
in drinking water not in close proximity
to the study site. PFOS was phased out
of production in the U.S. between 2000
and 2002, and regulation limits its
importation to a very small number of
controlled, very low release uses, (67 FR
72854; December 9, 2002 (USEPA, 2002
c)). Based on the general absence of
occurrence data, combined with the
phase out, effectively eliminating most
future releases, PFOS did not meet the
criteria for CCL 3.
The Agency is evaluating data related
to PFOA in a formal risk assessment
process under the Toxic Substance
Control Act. EPA's Science Advisory
Board (SAB) completed a review of a
draft risk assessment in 2006 and SAB
made recommendations for the further
development of the risk assessment. A
final risk assessment may not be
completed for several years, as a number
of important studies are underway. The
Agency is also participating in
additional research regarding the
toxicity and persistence of related
perfluorochemicals, as well as research
to help identify where these chemicals
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9653
are coming from and how people may
be exposed to them.
C. Helicobacter pylori
Helicobacter pylori is a pathogen that
causes gastric cancer in addition to
acute gastric ulcers. EPA placed this
pathogen on the draft CCL. However,
the analysis for H. pylori differs from the
other pathogens due to the long term
and/or chronic nature of its health
effects rather than the more common
acute effects of most waterborne
pathogens. This organism is an
emerging pathogen whose impact has
only recently begun to be understood.
Given the slow development of adverse
health effects due to infection by H.
pylori, it is more difficult to link
contamination of drinking water and
show a waterborne disease outbreak.
Therefore, given the long timeframe of
cancer and ulcer development (as
opposed to the commonly acute
gastrointestinal illness of nearly all the
other pathogens on the PCCL) as well as
the ongoing nature of the research, EPA
used peer-reviewed scientific papers to
score the health effects of Helicobacter
pylori. EPA request comment on the
process of selection of microbial
contaminants that cause chronic rather
than acute health effects.
V. EPA's Next Steps
Between now and the publication of
the final CCL, the Agency will evaluate
comments received during the comment
period for this notice, consult with the
SAB, and re-evaluate the criteria used to
develop the draft CCL and revise the
CCL, as appropriate.
VI. References
Boulanger, B., J. Vargo, J.L. Schnoor and K.C.
Hornbuckle. 2004. Detection of
Perfluorooctane Surfactants in Great
Lakes Water. Environmental Science and
Technology, Vol. 38, No. 15. pp 4064-
4070.
CDC. 2004. Surveillance for Waterborne-
Disease Outbreaks Associated with
Drinking Water—United States, 2001-
2002. MMWR Surveillance Summaries,
53(SS08); 23-45.
CDC. 2006. Surveillance for Waterborne-
Disease Outbreaks Associated with
Drinking Water—United States, 2003-
2004. MMWR Surveillance Summaries,
55{SS12); 31-58.
Darnerud, P.O., G.S. Erickson, T.
Johannesson, P.B. Larson, and M.
Viluksela. 2001. Polybrominated
Diphenyl Ethers: Occurrence, Dietary
Exposure, and Toxicology.
Environmental Health Perspectives
Supplements. Vol. 109, No. SI. Available
on the Internet at: http://
ehp.niehs.nih.gov/members/2001/suppl-
1 /4 9-68dam erudtdarn eru d-full.h tml.
Eramett, E.A., F.S. Shofer, H. Zhang, D.
Freeman, C. Desai, L.M. Shaw. 2006.
Community Exposure to
Perfluorooctanoate: Relationships
Between Serum Concentrations and
Exposure Sources, Journal of
Occupational and Environmental
Medicine, Vol. 48, No. 8, pp. 759-770.
Goeden, H. and J. Kelly. 2006.
Perfluorochemicals in Minnesota,
Minnesota Department of Health, Senate
Environment and Natural Resources
Committee, February 27. Available on
the Internet at: http://
www.health.state.mn.us/divs/eh/
hazardous/sites/washington/pfcsmn.pdf.
Hansen, K.J., H.O. Johnson, J.S. Eldridge, J.L.
Blutenhoff and L.A. Dick. 2002.
Quantitative Characterization of Trace
Levels of PFOS and PFOA in the
Tennessee River. Environmental Science
and Technology, Vol. 36, No. 8, pp.
1681-1685.
National Drinking Water Advisory Council
(NOWAC). 2004. National Drinking
Water Advisory Council Report on the
CCL Classification Process to the U.S.
Environmental Protection Agency, May
19, 2004.
National Research Council (NRC). 2001.
Classifying Drinking Water
Contaminants for Regulatory
Consideration. National Academy Press,
Washington, DC.
NIST. 2006. NIST/SEMATECH e-Handbook
of Statistical Methods. Available on the
internet at: http://www.itl.nist.gov/
div898/handbook/, (used on May 3,
2007).
Taylor, L.H., S.M. Latham, and M.E.
Woolhouse. 2001. Risk factors for human
disease emergence (Appendix A). Phil.
Trans. R. Soc. Lond. B. Vol. 256, pp.
983-989.
Tyler, K.T., E.S. Barton, M.L. Ibach, C.
Robinson, J.A. Campbell, S.M.
O'Donnell, T. Valyi-Nagy, P. Clarke, J.D.
Wetzel, T.S. Dermody. 2004. Isolation
and Molecular Characterization of a
Novel Type 3 Reovirus from a Child with
Meningitis. Jour. Infect. Dis. Vol. 189,
No. 9, pp. 1664-75.
USEPA. 1989a. National Primary Drinking
Water Regulations; Filtration,
Disinfection; Turbidity, Giardia Lamblia,
Viruses, Legionella, and Heterotrophic
Bacteria; Final Rule. Part 2. Federal
Register. Vol. 54, No. 124, p. 27486, June
29, 1989.
USEPA. 1989b. Drinking Water; National
Primary Drinking Water Regulations;
Total Coliforms (Including Fecal
Coliforms and E. Coli). Federal Register.
Vol. 54, No. 124, p. 27544, June 29, 1989.
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. 1997. Announcement of the Draft
Drinking Water Contaminant Candidate
List; Notice. Federal Register. Vol. 62,
No. 193, p. 52193, October 6, 1997.
USEPA. 1998a. Interim Enhanced Surface
Water Treatment; Final Rule. Federal
Register. Vol. 63, No 241, p. 69478,
December 16, 1998.
USEPA. 1998b. Announcement of the Draft
Drinking Water Contaminant Candidate
List; Notice. Federal Register. Vol. 63,
No. 40, p. 10273, March 2, 1998.
USEPA. 1999. Revisions to the Unregulated
Contaminant Monitoring Regulation for
Public Water Systems. Federal Register.
Vol. 64, No. 180, p. 50556, September 17,
1999.
USEPA. 2002a. Long Term 1 Enhanced
Surface Water Treatment Rule; Final
Rule. Federal Register. Vol. 67, No. 9, p.
1813. January 14, 2002.
USEPA. 2002b. Announcement of
Preliminary Regulatory Determinations
for Priority Contaminants on the
Drinking Water Contaminant Candidate
List. Federal Register. Vol. 67, No. 106,
p. 38222, June3, 2002.
USEPA. 2002c. Perfluoroalkyl Sulfonates;
Significant New Use Rule. Federal
Register. Vol 67, No. 236, p. 72854,
December 9, 2002.
USEPA. 2003a. Announcement of Regulatory
Determinations for Priority
Contaminants on the Drinking Water
Contaminant Candidate List. Federal
Register. Vol. 68, No. 138, p. 42898, July
18, 2003.
USEPA. 2004. Drinking Water Contaminant
Candidate List 2; Notice. Federal
Register. Vol. 69, No. 64, p. 17406, April
2, 2004.
USEPA. 2005a. Draft Risk Assessment of the
Potential Human Health Effects
Associated with Exposure to
Perfluorooctanoic Acid and its Salts.
OPPTS, SAB Draft. January 4, 2005.
USEPA. 2005b. Notice—Drinking Water
Contaminant Candidate List 2; Final
Notice. Federal Register. Vol. 70, No. 36,
p. 9071, February 24, 2005.
USEPA. 2006a. Long Term 2 Enhanced
Surface Water Treatment Rule; Final
Rule. Federal Register. Vol. 71, No. 3, p.
654, January 5, 2006.
USEPA. 2006b. Request for Nominations of
Drinking Water Contaminants for the
Contaminant Candidate List; Notice.
Federal Register. Vol. 71, No. 199, p.
60704, October 16, 2006.
USEPA. 2006c. National Primary Drinking
Water Regulations: Ground Water Rule;
Final Rule. Federal Register. Vol. 71, No.
216, p. 65573, November 8, 2006.
USEPA. 2007 a. Unregulated Contaminant
Monitoring Regulation (UCMR) for
Public Water Systems Revisions; Final
Rule. Federal Register. Vol. 72, No. 2, p.
367, January 4, 2007.
USEPA. 2007 b. Unregulated Contaminant
Monitoring Regulation (UCMR) for
Public Water Systems Revisions;
Correction. Federal Register. Vol. 72, No.
17, p. 3916, January 26, 2007.
USEPA. 2007 c. Unregulated Contaminant
Monitoring Regulation (UCMR) for
Public Water Systems Revisions;
Correction. Federal Register. Vol. 72, No.
19, p. 4328, January 30, 2007.
USEPA. 2007 d. Drinking Water: Regulatory
Determinations Regarding Contaminants
on the Second Drinking Water
Contaminant Candidate List—
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Preliminary Determinations; Proposed
Rule. Federal Register. Vol. 72, No. 83,
p. 24016, May 1,2007.
USEPA. 2008 a. Contaminant Candidate List
3 Chemicals: Identifying the Universe.
EPA 815-R-08-002. Draft. February,
2008.
USEPA. 2008 b. Contaminant Candidate List
3 Chemicals: Screening to a PCCL. EPA
815-R-08-003. Draft. February, 2008.
USEPA. 2008 c. Contaminant Candidate List
3 Chemicals: Classification of the PCCL
to the CCL, EPA 815-R-08-004. Draft.
February, 2008.
USEPA. 2008 d. Contaminant Candidate List
3 Microbes: Identifying the Universe,
EPA 815-R-08-O05. Draft. February,
2008.
USEPA. 2008 e. Contaminant Candidate List
3 Microbes: Screening to the PCCL, EPA
815-R-08-006. Draft. February, 2008.
USEPA. 2008 f. Contaminant Candidate List
3 Microbes: PCCL to CCL Process, EPA
815-R-08-007. Draft. February, 2008.
USEPA. 2008 g. Summary of Nominations for
the Third Contaminants Candidate List.
EPA 815-R-08-008. Draft. February,
2008.
USEPA. 2008 h. Chemical Expert Input and
Review for the Third Contaminant
Candidate List, EPA 815-R-08-009.
Draft. February, 2008.
USEPA. 2008 i. Microbial Expert Input and
Review, EPA 815-R-08-010. Draft.
February, 2008.
Dated: February 6, 2008.
Benjamin H. Grumbles,
Assistant Administrator, Office of Water.
[FR Doc. E8-3114 Filed 2-20-08; 8:45 am]
BILLING CODE 6560-5O-P
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