[Federal Register Volume 86, Number 135 (Monday, July 19, 2021)]
[Proposed Rules]
[Pages 37948-37972]
[FR Doc No: 2021-15121]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 141

[EPA-HQ-OW-2018-0594; FRL-7251-01-OW]

Drinking Water Contaminant Candidate List 5--Draft

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of availability; request for comments.

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SUMMARY: The U.S. Environmental Protection Agency (EPA) is publishing a
draft list of contaminants that are currently not subject to any
proposed or promulgated national primary drinking water regulations for
public review and comment. These contaminants are known or anticipated
to occur in public water systems and may require regulation under the
Safe Drinking Water Act (SDWA). This draft list is the Fifth
Contaminant Candidate List (CCL 5) published by the agency since the
SDWA amendments of 1996. The Draft CCL 5 includes 66 chemicals, 3
chemical groups (per- and polyfluoroalkyl substances (PFAS),
cyanotoxins, and disinfection byproducts) and 12 microbial
contaminants. EPA seeks comment on the Draft CCL 5 and on improvements
implemented in the CCL 5 process for consideration in developing future
CCLs.

DATES: Comments must be received on or before September 17, 2021.

ADDRESSES: You may send comments, identified by Docket ID Number EPA-
HQ-OW-2018-0594, by any of the following methods:
    Federal eRulemaking Portal: https://www.regulations.gov (our
preferred method). Follow the online instructions for submitting
comments.
    Mail: U.S. Environmental Protection Agency, EPA Docket Center,
Water Docket, Environmental Protection Agency, Mail code: 28221T, 1200
Pennsylvania Ave. NW, Washington, DC 20460.
    Hand Delivery/Courier (by scheduled appointment only): EPA Docket
Center, WJC West Building, Room 3334, 1301 Constitution Ave. NW,
Washington, DC 20004. The Docket Center's hours of operations are 8:30
a.m. to 4:30 p.m., Monday through Friday (except federal holidays).
    Instructions: All submissions received must include the Docket ID
No. EPA-HQ-OW-2018-0594 for this rulemaking. Comments received may be
posted without change to https://www.regulations.gov, including any
personal information provided. For detailed instructions on sending
comments and additional information on the rulemaking process, see the
``Public Participation'' heading of the SUPPLEMENTARY INFORMATION
section of this document. Out of an abundance of caution for members of
the public and our staff, the EPA Docket Center and Reading Room are
closed to the public, with limited exceptions, to reduce the risk of
transmitting COVID-19. Our Docket Center staff will continue to provide
remote customer service via email, phone, and webform. We encourage the
public to submit comments via https://www.regulations.gov, as there may
be delay in processing mail. Hand deliveries and couriers may be
received by scheduled appointment only. For further information of EPA
Docket Center Services and the current status, please visit us online
at https://www.epa.gov/dockets.

FOR FURTHER INFORMATION CONTACT: For information on chemical
contaminants contact Kesha Forrest, Office of Ground Water and Drinking
Water, Standards and Risk Management Division, at<PHONE_NUMBER> or
email<EMAIL_ADDRESS>For information on microbial contaminants
contact Nicole Tucker, Office of Ground Water and Drinking Water,
Standards and Risk Management Division, at<PHONE_NUMBER> or email
<EMAIL_ADDRESS>    For more information visit https://www.epa.gov/ccl.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. General Information
    A. Does this action impose any requirements on public water
systems?
    B. Public Participation
    C. What should I consider as I prepare my comments for EPA?
II. Purpose, Background, and Statutory Requirements of This Action
    A. What is the purpose of this action?
    B. Background and Statutory Requirements for CCL, Regulatory
Determinations and Unregulated Contaminant Monitoring Rule
    1. Contaminant Candidate List
    2. Regulatory Determinations
    3. Unregulated Contaminant Monitoring Rule
    C. Interrelationship of the CCL, Regulatory Determinations, and
Unregulated Contaminant Monitoring
    D. Summary of Previous CCLs and Regulatory Determinations
    1. The First Contaminant Candidate List
    2. The Regulatory Determinations for CCL 1 Contaminants
    3. The Second Contaminant Candidate List
    4. The Regulatory Determinations for CCL 2 Contaminants

    5. The Third Contaminant Candidate List
    6. The Regulatory Determinations for CCL 3 Contaminants
    7. The Fourth Contaminant Candidate List
    8. The Regulatory Determinations for CCL 4 Contaminants
    E. Summary of the Approach Used To Identify Contaminants for the
Draft CCL 5
    1. Chemical Contaminants
    2. Microbial Contaminants
    F. What is included on the Draft CCL 5?
III. Developing the Draft CCL 5
    A. Approach Used To Identify Chemical Candidates for the Draft
CCL 5
    1. Building the Chemical Universe
    2. Screening Chemicals to a PCCL
    a. Screening the Chemical Universe
    b. Publicly Nominated Chemicals
    c. Chemicals Excluded From the PCCL
    i. Regulatory Determinations
    ii. Canceled Pesticides
    d. Summary of the PCCL
    3. Classification of PCCL Chemicals To Select the Draft CCL
    a. Supplemental Data Collection
    i. Occurrence
    ii. Health Effects
    b. Calculated Data Elements
    i. Health Reference Levels and CCL Screening Levels
    ii. Final Hazard Quotients
    iii. Attribute Scores
    c. Evaluation Team Listing Decision Process
    d. Logistic Regression
    e. Chemical Groups on the Draft CCL 5
    B. Approach Used To Identify Microbial Candidates for the Draft
CCL 5
    1. Building the Microbial Universe
    2. Screening the Microbial Universe to the PCCL
    3. The PCCL to Draft CCL Process
    a. Waterborne Disease Outbreak (WBDO) Protocol
    b. Occurrence Protocol
    c. Health Effects Protocol
    d. Combining Protocol Scores to Rank Pathogens
    e. Selection of the Draft CCL Microbes
    f. Organisms Covered by Existing Regulations
    C. Summary of Nominated Candidates for the Draft CCL 5
    1. Data Sources for the Nominated Chemical and Microbial
Contaminants
    a. Chemical Nominations
    b. Microbial Nominations
    2. Listing Outcomes for the Nominated Chemical Contaminants
    3. Listing Outcomes for the Nominated Microbial Contaminants
    D. Data Availability Assessment for the Draft CCL 5 Chemicals
IV. Request for Comments
V. EPA's Next Steps
VI. References

I. General Information

A. Does this action impose any requirements on public water systems?

    The Draft Contaminant Candidate List 5 (CCL 5) and the Final CCL 5,
when published, will not impose any requirements on regulated entities.

B. Public Participation

    Submit your comments, identified by Docket ID No. EPA-HQ-OW-2018-
0594, at https://www.regulations.gov (our preferred method), or the
other methods identified in the ADDRESSES section of this document.
Once submitted, comments cannot be edited or removed from the docket.
EPA may publish any comment received to its public docket. Do not
submit electronically any information you consider to be Confidential
Business Information (CBI) or other information whose disclosure is
restricted by statute. Multimedia submissions (audio, video, etc.) must
be accompanied by a written comment. The written comment is considered
the official comment and should include discussion of all points you
wish to make. EPA will generally not consider comments or comment
contents located outside of the primary submission (i.e., on the web,
cloud, or other file sharing system). For additional submission
methods, the full EPA public comment policy, information about CBI or
multimedia submissions, and general guidance on making effective
comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.
    EPA is temporarily suspending its Docket Center and Reading Room
for public visitors, with limited exceptions, to reduce the risk of
transmitting COVID-19. Our Docket Center Staff will continue to provide
remote customer service via email, phone, and webform. We encourage the
public to submit comments via https://www.regulations.gov/ as there may
be a delay in processing mail. Hand deliveries or couriers will be
received by scheduled appointment only. For further information and
updates on EPA Docket Center services, please visit us online at
https://www.epa.gov/dockets.
    EPA continues to carefully monitor information from the Centers for
Disease Control and Prevention (CDC), local area health departments,
and our federal partners so that we can respond rapidly as conditions
change regarding COVID-19.

C. 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 full references for any peer reviewed publication 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 Statutory Requirements of This Action

    This section briefly summarizes the purpose of this action, the
statutory requirements, previous activities related to the CCL and the
approach used to develop the Draft CCL 5.

A. What is the purpose of this action?

    The purpose of this action is to present EPA's Draft CCL 5 and the
rationale for the selection process used to make the list. This Draft
CCL 5, when finalized, is subsequently used to make regulatory
determinations on whether to regulate at least five contaminants from
the CCL with national primary drinking water regulations (NPDWRs) under
the Safe Drinking Water Act (SDWA), section 1412(b)(1)(B)(ii). This
action only addresses the Draft CCL 5. The regulatory determinations
process for contaminants on the CCL is a separate agency action. EPA
requests comment on the Draft CCL 5 and on improvements implemented in
the CCL 5 process for consideration in developing future CCLs.

B. Background and Statutory Requirements for CCL, Regulatory
Determinations and Unregulated Contaminant Monitoring

1. Contaminant Candidate List
    SDWA section 1412(b)(1)(B)(i), as amended in 1996, requires EPA to
publish the CCL every five years. The 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 the SDWA. The
unregulated contaminants considered for listing shall include, but not
be limited to, hazardous substances identified in section 101(14) of
the Comprehensive Environmental Response, Compensation, and Liability
Act (CERCLA) of 1980, and substances registered as pesticides under the
Federal Insecticide, Fungicide, and

Rodenticide Act (FIFRA). The SDWA directs EPA 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. The statute further
directs EPA to take into consideration the effect of contaminants upon
subgroups that comprise a meaningful portion of the general population
(such as infants, children, pregnant women, the elderly, and
individuals with a history of serious illness or other subpopulations)
that are identifiable as being at greater risk of adverse health
effects due to exposure to contaminants in drinking water than the
general population. EPA considers age-related subgroups as
``lifestages'' in reference to a distinguishable time frame in an
individual's life characterized by unique and relatively stable
behavioral and/or physiological characteristics that are associated
with development and growth. Thus, childhood is viewed as a sequence of
stages, from conception through fetal development, infancy and
adolescence (see http://www2.epa.gov/children/early-life-stages).
2. Regulatory Determinations
    SDWA section 1412(b)(1)(B)(ii), as amended in 1996, requires EPA,
at five-year intervals, to make determinations of whether or not to
regulate no fewer than five contaminants from the CCL. The 1996 SDWA
Amendments 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.

If, after considering public comment on a preliminary determination,
EPA makes a determination to regulate a contaminant, the agency will
initiate the process to propose an NPDWR.\1\ In that case, the
statutory time frame provides for EPA proposal of a regulation within
24 months and action on a final regulation within 18 months of
proposal.
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    \1\ An NPDWR is a legally enforceable standard that applies to
public water systems. An NPDWR sets a legal limit (called a maximum
contaminant level or MCL) or specifies a certain treatment technique
for public water systems for a specific contaminant or group of
contaminants. The MCL is the highest level of a contaminant that is
allowed in drinking water and is set as close to the MCLG as
feasible, using the best available treatment technology and taking
cost into consideration.
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3. Unregulated Contaminant Monitoring Rule
    SDWA section 1445(a)(2), as amended in 1996, requires that once
every five years, beginning in 1999, EPA issues a new list of no more
than 30 unregulated contaminants to be monitored in drinking water by
PWSs. Monitoring is required by all PWSs serving more than 10,000
persons. The SDWA, as amended by America's Water Infrastructure Act of
2018, expands the requirements of the program and specifies that,
subject to availability of appropriations and laboratory capacity, the
UCMR program shall include all systems serving between 3,300 and 10,000
persons and a nationally representative sample of PWSs serving fewer
than 3,300 persons. The program would continue to require monitoring by
PWSs serving more than 10,000 persons. The SDWA also requires EPA to
enter the monitoring data into the publicly available National
Contaminant Occurrence Database (NCOD). This national occurrence data
is used to inform regulatory decisions for emerging contaminants in
drinking water. Since the development of the UCMR program, EPA has
issued four UCMRs. The UCMR 1 was published in the Federal Register on
September 17, 1999 (64 FR 50556, USEPA, 1999), and required monitoring
for 26 contaminants from 2001 to 2005. The UCMR 2 was published in the
Federal Register on January 4, 2007 (72 FR 368, USEPA, 2007), and
required monitoring for 25 contaminants from 2008 to 2010. The UCMR 3
was published in the Federal Register on May 2, 2012 (77 FR 26072,
USEPA, 2012a), and required monitoring for 30 contaminants: 28
chemicals and two viruses from 2013 to 2015. The UCMR 4 was published
in the Federal Register on December 20, 2016 (81 FR 92666, USEPA,
2016a), and required monitoring for 30 contaminants from 2018 to 2020.
Seventeen of the contaminants being monitored under the UCMR 4 were
included on the CCL 4 and 13 chemicals or chemical groups monitored
under the UCMR 4 are included on the Draft CCL 5. EPA published the
UCMR 5 proposal in the Federal Register on March 11, 2021 (86 FR 13846,
USEPA, 2021a). The proposed UCMR 5 would require monitoring for 29 per-
and polyfluoroalkyl substances (PFAS) and lithium in drinking water
from 2023 to 2025. The Draft CCL 5 includes all of the contaminants
that are proposed for monitoring on the UCMR 5.

C. Interrelationship of the CCL, Regulatory Determinations, and
Unregulated Contaminant Monitoring

    The CCL is the first step in the SDWA regulatory framework for
screening and evaluating the subset of contaminants that may require
future regulation. The CCL serves as the initial screening of potential
contaminants to consider for regulatory determinations. However,
inclusion on the CCL does not mean that any particular contaminant will
necessarily be regulated in the future.
    The UCMR provides a mechanism to obtain nationally representative
occurrence data for contaminants in drinking water. Historically, most
unregulated contaminants chosen by EPA for monitoring have been
selected from the CCL. When selecting contaminants for monitoring under
the UCMR, EPA considers the availability of health effects data and the
need for national occurrence data for contaminants, as well as
analytical method availability, availability of analytical standards,
sampling costs, and laboratory capacity to support a nationwide
monitoring program. The contaminant occurrence data collected under the
UCMR serves to better inform future CCLs and regulatory determinations.
Contaminants on the CCL are evaluated based on health effects and
occurrence information and those contaminants with sufficient
information to make a regulatory determination are then evaluated based
on the three statutory criteria in SDWA section 1412(b)(1), to
determine whether a regulation is required (called a positive
determination) or not required (called a negative determination). Under
the SDWA, EPA must make regulatory determinations for at least five
contaminants listed on the CCL every five years. For those contaminants
without sufficient information to allow EPA to make a regulatory
determination, the agency encourages research to provide the
information needed to fill the data gaps to determine whether to
regulate the contaminant.
    This action addresses only the CCL 5 and not the UCMR or regulatory
determinations.

D. Summary of Previous CCLs and Regulatory Determinations

1. The First Contaminant Candidate List
    The first CCL (CCL 1) was published on March 2, 1998 (63 FR 10274,
USEPA, 1998). The CCL 1 was developed based on recommendations by the
National Drinking Water Advisory Council (NDWAC) and reviewed by
technical experts. It contained 50 chemicals and 10 microbial
contaminants/groups.

2. The Regulatory Determinations for CCL 1 Contaminants
    EPA published its final regulatory determinations for a subset of
contaminants listed on the CCL 1 on July 18, 2003 (68 FR 42898, USEPA,
2003). EPA identified 9 contaminants from the 60 contaminants listed on
the CCL 1 that had sufficient data and information available to make
regulatory determinations. The nine contaminants were Acanthamoeba,
aldrin, dieldrin, hexachlorobutadiene, manganese, metribuzin,
naphthalene, sodium, and sulfate. EPA determined that no regulatory
action was appropriate or necessary for any of the nine contaminants at
that time. EPA subsequently issued guidance on Acanthamoeba and Health
Advisories for manganese, sodium, and sulfate.
3. The Second Contaminant Candidate List
    EPA published the Final CCL 2 on February 24, 2005 (70 FR 9071,
USEPA, 2005). EPA carried forward the 51 remaining chemical and
microbial contaminants from the CCL 1 (that did not have regulatory
determinations) to the CCL 2.
4. The Regulatory Determinations for CCL 2 Contaminants
    EPA published its final regulatory determinations for a subset of
contaminants listed on the CCL 2 on July 30, 2008 (73 FR 44251, USEPA,
2008). EPA identified 11 contaminants from the 51 contaminants listed
on the CCL 2 that had sufficient data and information available to make
regulatory determinations. The 11 contaminants were boron, the dacthal
mono- and di-acid degradates, 1,1-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. EPA made a final determination that no
regulatory action was appropriate or necessary for any of the 11
contaminants. New or updated Health Advisories were subsequently issued
for: Boron, the dacthal degradates, 2,4-dinitrotoluene, 2,6-
dinitrotoluene, and 1,1,2,2-tetrachloroethane.
5. The Third Contaminant Candidate List
    EPA published the Final CCL 3 on October 8, 2009 (74 FR 51850,
USEPA, 2009). In developing the CCL 3, EPA implemented an improved,
stepwise process which built on the previous CCL process and was based
on expert input and recommendations from the National Academy of
Sciences' National Research Council (NRC), the National Drinking Water
Advisory Council (NDWAC), and the Science Advisory Board (SAB). The CCL
3 contained 104 chemicals or chemical groups and 12 microbial
contaminants.
6. The Regulatory Determinations for CCL 3 Contaminants
    On February 11, 2011, EPA published in the Federal Register (76 FR
7762, USEPA, 2011) a determination that perchlorate (a CCL 3
contaminant) met the criteria for regulating a contaminant under the
SDWA based upon the information available at that time. On January 4,
2016, EPA published in the Federal Register (81 FR 13, USEPA, 2016b)
final determinations not to regulate four additional CCL 3
contaminants--dimethoate, 1,3-dinitrobenzene, terbufos and terbufos
sulfone.
    EPA published a proposed rulemaking for perchlorate in the Federal
Register on June 26, 2019 (85 FR 43990, USEPA, 2019a), and sought
public input on regulatory alternatives for perchlorate, including
withdrawal of the previous regulatory determination. Based on the
evaluation of public comments, and review of the updated scientific
data, EPA withdrew the 2011 regulatory determination and made a final
determination not to regulate perchlorate on July 21, 2020 (85 FR
43990, USEPA, 2020). EPA is reviewing this final determination in
accordance with President Biden's Executive Order No. 13990 (86 FR
7037, Executive Office of the President, 2021).
7. The Fourth Contaminant Candidate List
    EPA published the Final CCL 4 in the Federal Register on November
17, 2016 (81 FR 81099, USEPA, 2016c). The Final CCL 4 contained 97
chemicals or chemical groups and 12 microbial contaminants. All
contaminants listed on the Final CCL 4 were carried forward from CCL 3,
except for manganese and nonylphenol, which were nominated by the
public to be included on the CCL 4. For information about publicly
nominated contaminants for the CCL 5, see Section III.C.1 of this
document.
8. The Regulatory Determinations for CCL 4 Contaminants
    On March 3, 2021, EPA published final regulatory determinations for
eight contaminants on the CCL 4 (86 FR 12272, USEPA, 2021b). EPA made
final determinations to regulate perfluorooctanesulfonic acid (PFOS)
and perfluorooctanoic acid (PFOA) in drinking water and to not regulate
six contaminants 1,1-dichloroethane, acetochlor, methyl bromide
(bromomethane), metolachlor, nitrobenzene, and 1,3,5-Trinitro-1,3,5-
triazinane (RDX).

E. Summary of the Approach Used To Identify Contaminants for the Draft
CCL 5

    In developing the Draft CCL 5, EPA followed the stepwise process
used in developing the CCL 3 and CCL 4, which was based on expert input
and recommendations from the SAB, NRC and NDWAC. Note that EPA used an
abbreviated process for the CCL 4 by carrying forward the CCL 3
contaminants (81 FR 81099, USEPA, 2016c). In each cycle of the CCL, EPA
attempts to improve the CCL development process in response to comments
from the SAB and the public. Therefore, in developing the Draft CCL 5,
EPA implemented improvements to the CCL process to better identify,
screen, and classify potential drinking water contaminants. EPA's
approach utilizes the best available data to characterize the
occurrence and adverse health risks a chemical may pose from potential
drinking water exposure.
    Exhibit 1 illustrates a generalized 3-step process EPA applied to
both chemical and microbial contaminants for the Draft CCL 5. The
agency began with a large Universe of contaminants, screened it down to
a Preliminary CCL 5, then finally selected the Draft CCL 5. The
specific execution of particular steps differed in detail for the
chemical and microbial contaminants. Each step of the Draft CCL 5
process and associated number of chemical and microbial contaminants
are described in Section III of this document.

[GRAPHIC] [TIFF OMITTED] TP19JY21.002

1. Chemical Contaminants
    EPA followed 3 three-step process illustrated in Exhibit 1 to
identify chemicals for inclusion on the Draft CCL 5. These steps
included:
    Step 1. Building a broad universe of potential drinking water
contaminants (called the CCL 5 Chemical Universe). EPA evaluated 134
data sources and identified 43 that were related to potential drinking
water chemical contaminants and met established CCL assessment factors.
From these data sources, EPA identified and extracted occurrence and
health effects data for the 21,894 chemicals that form the CCL 5
Chemical Universe.
    Step 2. Screening the CCL 5 Chemical Universe to identify a list of
chemicals that should be further evaluated (called the Preliminary CCL
5 (PCCL 5)). EPA established and applied a data-driven screening points
system to identify and prioritize a subset of chemicals with the
greatest potential for public health concern. The agency also
incorporated publicly nominated chemicals to the PCCL 5.
    Step 3. Classifying PCCL 5 chemicals to select the Draft CCL 5
chemicals. EPA compiled occurrence and health effects information for
use by two evaluation teams of EPA scientists. The evaluation teams
reviewed this information for each chemical before reaching a group
decision on whether to list a chemical on the Draft CCL 5.
    A more detailed description of the processes used to develop the
Draft CCL 5 of chemicals using these steps can be found in the
Technical Support Document for the Draft Fifth Contaminant Candidate
List (CCL 5)--Chemical Contaminants (USEPA, 2021c).
2. Microbial Contaminants
    EPA followed the 3-step process illustrated in Exhibit 1 to
identify microbes for inclusion on the Draft CCL 5. For microbial
contaminants, these steps included:
    Step 1. Building a broad universe of all microbes that may cause
human disease.
    Step 2. Screening that universe of microbial contaminants to
produce a PCCL 5.
    Step 3. Selecting the Draft CCL 5 microbial list by ranking the
PCCL 5 contaminants based on occurrence in drinking water (including
waterborne disease outbreaks) and human health effects.
    This approach is similar to that used by EPA for the CCL 3, with
updates made to the microbial screening process in response to SAB and
stakeholder comments. EPA re-examined all 12 microbial exclusionary
screening criteria used in previous CCLs and modified one criterion for
the CCL 5. More details on the screening process are presented in the
Technical Support Document for the Draft Fifth Candidate List (CCL 5)--
Microbial Contaminants (USEPA, 2021d). (Note, referred to as the
Microbial Technical Support Document thereafter.)

F. What is included on the Draft CCL 5?

    The Draft CCL 5 includes 81 contaminants or groups (Exhibits 2a,
2b, and 2c). The list is comprised of 69 chemicals or chemical groups
and 12 microbes. The 69 chemicals or chemical groups include 66
chemicals recommended for listing following an improved process to
evaluate the PCCL, one group of cyanotoxins, one group of disinfection
byproducts (DBPs), and one group of PFAS chemicals. The 12 microbes
include 8 bacteria, 3 viruses, and 1 protozoa recommended for listing
based on the scores for waterborne disease outbreaks, occurrence,
health effects, and recommendations from various experts.

                              Exhibit 2a--Chemical Contaminants on the Draft CCL 5
----------------------------------------------------------------------------------------------------------------
                     Chemical name                          CASRN \1\                   DTXSID \2\
----------------------------------------------------------------------------------------------------------------
1,2,3-Trichloropropane.................................          96-18-4  DTXSID9021390
1,4-Dioxane............................................         123-91-1  DTXSID4020533
17-alpha ethynyl estradiol.............................          57-63-6  DTXSID5020576
2,4-Dinitrophenol......................................          51-28-5  DTXSID0020523
2-Aminotoluene.........................................          95-53-4  DTXSID1026164
2-Hydroxyatrazine......................................        2163-68-0  DTXSID6037807
4-Nonylphenol (all isomers)............................       25154-52-3  DTXSID3021857
6-Chloro-1,3,5-triazine-2,4-diamine....................        3397-62-4  DTXSID1037806
Acephate...............................................       30560-19-1  DTXSID8023846
Acrolein...............................................         107-02-8  DTXSID5020023
alpha-Hexachlorocyclohexane (alpha-HCH)................         319-84-6  DTXSID2020684
Anthraquinone..........................................          84-65-1  DTXSID3020095
Bensulide..............................................         741-58-2  DTXSID9032329
Bisphenol A............................................          80-05-7  DTXSID7020182
Boron..................................................        7440-42-8  DTXSID3023922
Bromoxynil.............................................        1689-84-5  DTXSID3022162
Carbaryl...............................................          63-25-2  DTXSID9020247
Carbendazim (MBC)......................................       10605-21-7  DTXSID4024729
Chlordecone (Kepone)...................................         143-50-0  DTXSID1020770
Chlorpyrifos...........................................        2921-88-2  DTXSID4020458
Cobalt.................................................        7440-48-4  DTXSID1031040
Cyanotoxins \3\........................................         Multiple  Multiple
Deethylatrazine........................................        6190-65-4  DTXSID5037494
Desisopropyl atrazine..................................        1007-28-9  DTXSID0037495
Desvenlafaxine.........................................       93413-62-8  DTXSID40869118
Diazinon...............................................         333-41-5  DTXSID9020407
Dicrotophos............................................         141-66-2  DTXSID9023914
Dieldrin...............................................          60-57-1  DTXSID9020453
Dimethoate.............................................          60-51-5  DTXSID7020479
Disinfection byproducts (DBPs) \4\.....................         Multiple  Multiple
Diuron.................................................         330-54-1  DTXSID0020446
Ethalfluralin..........................................       55283-68-6  DTXSID8032386
Ethoprop...............................................       13194-48-4  DTXSID4032611
Fipronil...............................................      120068-37-3  DTXSID4034609
Fluconazole............................................       86386-73-4  DTXSID3020627
Flufenacet.............................................      142459-58-3  DTXSID2032552
Fluometuron............................................        2164-17-2  DTXSID8020628
Iprodione..............................................       36734-19-7  DTXSID3024154
Lithium................................................        7439-93-2  DTXSID5036761
Malathion..............................................         121-75-5  DTXSID4020791
Manganese..............................................        7439-96-5  DTXSID2024169
Methomyl...............................................       16752-77-5  DTXSID1022267
Methyl tert-butyl ether (MTBE).........................        1634-04-4  DTXSID3020833
Methylmercury..........................................       22967-92-6  DTXSID9024198
Molybdenum.............................................        7439-98-7  DTXSID1024207
Norflurazon............................................       27314-13-2  DTXSID8024234
Oxyfluorfen............................................       42874-03-3  DTXSID7024241
Per- and polyfluoroalkyl substances (PFAS) \5\.........         Multiple  Multiple
Permethrin.............................................       52645-53-1  DTXSID8022292
Phorate................................................         298-02-2  DTXSID4032459
Phosmet................................................         732-11-6  DTXSID5024261
Phostebupirim..........................................       96182-53-5  DTXSID1032482
Profenofos.............................................       41198-08-7  DTXSID3032464
Propachlor.............................................        1918-16-7  DTXSID4024274
Propanil...............................................         709-98-8  DTXSID8022111
Propargite.............................................        2312-35-8  DTXSID4024276
Propazine..............................................         139-40-2  DTXSID3021196
Propoxur...............................................         114-26-1  DTXSID7021948
Quinoline..............................................          91-22-5  DTXSID1021798
Tebuconazole...........................................      107534-96-3  DTXSID9032113
Terbufos...............................................       13071-79-9  DTXSID2022254
Thiamethoxam...........................................      153719-23-4  DTXSID2034962
Tri-allate.............................................        2303-17-5  DTXSID5024344
Tribufos...............................................          78-48-8  DTXSID1024174
Tributyl phosphate.....................................         126-73-8  DTXSID3021986
Trimethylbenzene (1,2,4-)..............................          95-63-6  DTXSID6021402
Tris(2-chloroethyl) phosphate (TCEP)...................         115-96-8  DTXSID5021411
Tungsten...............................................        7440-33-7  DTXSID8052481
Vanadium...............................................        7440-62-2  DTXSID2040282
----------------------------------------------------------------------------------------------------------------
\1\ Chemical Abstracts Service Registry Number (CASRN) is a unique identifier assigned by the Chemical Abstracts
  Service (a division of the American Chemical Society) to every chemical substance (organic and inorganic
  compounds, polymers, elements, nuclear particles, etc.) in the open scientific literature. It contains up to
  10 digits, seperated by hyphens into three parts.

\2\ Distributed Structure Searchable Toxicity Substance Identifiers (DTXSID) is a unique substance identifier
  used in EPA's CompTox Chemicals database, where a substance can be any single chemical, mixture or polymer.
 \3\ Toxins naturally produced and released by some species of cyanobacteria (previously known as ``blue-green
  algae''). The group of cyanotoxins includes, but is not limited to: Anatoxin-a, cylindrospermopsin,
  microcystins, and saxitoxin.
\4\ This group includes 23 unregulated DBPs as shown in Exhibit 2b.
\5\ This group is inclusive of any PFAS (except for PFOA and PFOS). For the purposes of this document, the
  structural definition of PFAS includes per- and polyfluorinated substances that structurally contain the unit
  R-(CF2)-C(F)(R')R''. Both the CF2 and CF moieties are saturated carbons and none of the R groups (R, R' or
  R'') can be hydrogen (USEPA, 2021f).

                        Exhibit 2b--Unregulated DBPs in the DBP Group on the Draft CCL 5
----------------------------------------------------------------------------------------------------------------
                     Chemical name                            CASRN                       DTXSID
----------------------------------------------------------------------------------------------------------------
Haloacetic Acids:
    Bromochloroacetic acid (BCAA)......................        5589-96-8  DTXSID4024642
    Bromodichloroacetic acid (BDCAA)...................       71133-14-7  DTXSID4024644
    Dibromochloroacetic acid (DBCAA)...................         631-64-1  DTXSID3031151
    Tribromoacetic acid (TBAA).........................          75-96-7  DTXSID6021668
Haloacetonitriles:
    Dichloroacetonitrile (DCAN)........................        3018-12-0  DTXSID3021562
    Dibromoacetonitrile (DBAN).........................        3252-43-5  DTXSID3024940
Halonitromethanes:
    Bromodichloronitromethane (BDCNM)..................         918-01-4  DTXSID4021509
    Chloropicrin (trichloronitromethane, TCNM).........          76-96-2  DTXSID0020315
    Dibromochloronitromethane (DBCNM)..................        1184-89-0  DTXSID00152114
Iodinated Trihalomethanes:
    Bromochloroiodomethane (BCIM)......................       34970-00-8  DTXSID4021503
    Bromodiiodomethane (BDIM)..........................         557-95-9  DTXSID70204235
    Chlorodiiodomethane (CDIM).........................         638-73-3  DTXSID20213251
    Dibromoiodomethane (DBIM)..........................         557-68-6  DTXSID60208040
    Dichloroiodomethane (DCIM).........................         594-04-7  DTXSID7021570
    Iodoform (triiodomethane, TIM).....................          75-47-8  DTXSID4020743
Nitrosamines:
    Nitrosodibutylamine (NDBA).........................         924-16-3  DTXSID2021026
    N-Nitrosodiethylamine (NDEA).......................          55-18-5  DTXSID2021028
    N-Nitrosodimethylamine (NDMA)......................          62-75-9  DTXSID7021029
    N-Nitrosodi-n-propylamine (NDPA)...................         621-64-7  DTXSID6021032
    N-Nitrosodiphenylamine (NDPhA).....................          86-30-6  DTXSID6021030
    Nitrosopyrrolidine (NPYR)..........................         930-55-2  DTXSID8021062
Others:
    Chlorate...........................................       14866-68-3  DTXSID3073137
    Formaldehyde.......................................          50-00-0  DTXSID7020637
----------------------------------------------------------------------------------------------------------------

          Exhibit 2c--Microbial Contaminants on the Draft CCL 5
------------------------------------------------------------------------
               Microbial name                      Microbial class
------------------------------------------------------------------------
Adenovirus.................................  Virus.
Caliciviruses..............................  Virus.
Campylobacter jejuni.......................  Bacteria.
Escherichia coli (O157)....................  Bacteria.
Enteroviruses..............................  Virus.
Helicobacter pylori........................  Bacteria.
Legionella pneumophila.....................  Bacteria.
Mycobacterium abscessus....................  Bacteria.
Mycobacterium avium........................  Bacteria.
Naegleria fowleri..........................  Protozoa.
Pseudomonas aeruginosa.....................  Bacteria.
Shigella sonnei............................  Bacteria.
------------------------------------------------------------------------

III. Developing the Draft CCL 5

A. Approach Used To Identify Chemical Candidates for the Draft CCL 5

    The SDWA directs EPA to consider health effects and occurrence
information on unregulated contaminants to identify those that present
the greatest public health concern related to exposure from drinking
water. EPA gathered this information into a data directory that
supports the evaluation of contaminants over the three steps of the CCL
5 development process, as outlined in Section II.E.1 of this document.
1. Building the Chemical Universe
    The goal of the first step of the CCL 5 development process for
chemical candidates is to identify a broad universe of potential
drinking water contaminants. EPA began the CCL 5 development process by
compiling data sources to identify chemicals that would form a broad
CCL 5 Chemical Universe (e.g., a list of contaminants identified
through health and occurrence data sources that are relevant, complete,
retrievable, and not redundant). EPA compiled data sources identified
from the CCL 3 and the CCL 4, along with data sources recommended by
the CCL 5 EPA workgroup and subject matter experts. Information on how
EPA addressed data sources provided through the public nomination
process is described in Section III.C.1 of this document. As a result
of this effort, EPA identified 134 potential data sources and further
assessed their potential use for the CCL 5 development process. EPA
accessed each potential data source online and evaluated them using the
following assessment factors:
    Relevance: The data source contains information on demonstrated or
potential health effects, occurrence, or potential occurrence of
contaminants using surrogate information (e.g., environmental release,
environmental fate and transport properties);
    Completeness: The data source either (a) has been peer-reviewed, or
(b) provides a description of the data, information on how the data
were obtained, and contact information regarding the data source;
    Redundancy: The data source does not contain information identical
to other more comprehensive data sources also being considered; and,
    Retrievability: The data are formatted for automated retrieval
(e.g., data are stored in a tabular format) and publicly accessible.
    Out of the 134 potential data sources, 43 met all four assessment
factors and were therefore considered ``primary data sources'' that
were used to build the CCL 5 Chemical Universe. Data sources that met
the first three assessment

factors but were not retrievable were set aside as potential
supplemental sources, some of which were used as part of the CCL 5
classification process, as discussed further in this section as well as
Sections III.A.4 and III.C of this document. More information on how
data sources were assessed and extracted is provided in Sections 2.2
and 2.3, respectively, of the Chemical Technical Support Document
(USEPA, 2021c).
    EPA downloaded data from the 43 primary data sources and
categorized them as sources of health effects (Exhibit 3) or occurrence
(Exhibit 4) data. In total, 21,894 chemicals were identified from the
43 primary data sources.
    Out of the 43 primary data sources, EPA identified 17 sources of
health effects data that met the assessment factors of relevance,
completeness, redundancy, and retrievability. One additional health
effects data source, the Hazardous Substances Data Bank (HSDB), did not
meet the retrievability factor but was designated as a primary data
source. The HSDB is a data rich source, and the only source of Lethal
Dose, 50% (LD50s) for the CCL 5 development process.
    Therefore, additional effort was taken to extract this data, as was
done with the CCL 3 development process (USEPA, 2009a). These 18 data
sources, listed in Exhibit 3, include both qualitative and quantitative
data.

          Exhibit 3--CCL 5 Health Effects Primary Data Sources
------------------------------------------------------------------------
              Data source                       Agency or author 1
------------------------------------------------------------------------
Agency for Toxic Substances and Disease  Centers for Disease Control and
 Registry (ATSDR) Minimal Risk Levels     Prevention (CDC).
 (MRLs).
Cancer Potency Data Bank...............  National Library of Medicine,
                                          U.S. Department of Health and
                                          Human Services (HHS).
Drinking Water Standards and Health      EPA.
 Advisory Tables.
Guidelines for Canadian Drinking Water   Health Canada.
 Quality.
Guidelines for Drinking-Water Quality..  World Health Organization
                                          (WHO).
Hazardous Substances Data Bank.........  National Library of Medicine,
                                          HHS.
Health-Based Screening Levels (HBSLs)..  U.S. Geological Survey (USGS).
Human Health-Based Water Guidance Table  Minnesota Department of Health.
Human Health Benchmarks for Pesticides.  EPA.
Integrated Risk Information System       EPA.
 (IRIS).
International Agency for Research on     WHO.
 Cancer Classifications.
Maximum Recommended Daily Dose (MRDD)    U.S. Food and Drug
 Database.                                Administration (FDA).
National Recommended Water Quality       EPA.
 Criteria--Human Health Criteria.
National Toxicology Program (NTP)        HHS.
 Cancer Classifications.
Provisional Peer-Reviewed Toxicity       EPA.
 Values (PPRTVs).
Screening Levels for Pharmaceuticals...  FDA [email protected] database,
                                          National Institutes of Health
                                          (NIH) DailyMed Database.
Toxicity Criteria Database.............  California Environmental
                                          Protection Agency (CalEPA)
                                          Office of Environmental Health
                                          Hazard Assessment.
Toxicity Reference Database (ToxRefDB).  EPA
------------------------------------------------------------------------
\1\ References for the data sources listed in Exhibit 3 are provided in
  Appendix N of the Chemical Technical Support Document (USEPA, 2021c).

    EPA identified 25 sources of occurrence related data that met the
assessment factors of relevance, completeness, redundancy, and
retrievability. These data sources, listed in Exhibit 4, include both
qualitative and quantitative data.

                                Exhibit 4--CCL 5 Occurrence Primary Data Sources
----------------------------------------------------------------------------------------------------------------
               Data source                                          Agency or author \1\
----------------------------------------------------------------------------------------------------------------
ATSDR Comprehensive Environmental          CDC.
 Response, Compensation, and Liability
 Act (CERCLA) Substance Priority List.
Chemical Data Reporting (CDR) Results....  EPA.
``Concentrations of prioritized            Kostich et al. 2014.
 pharmaceuticals in effluents from 50
 large wastewater treatment plants in the
 US and implications for risk
 estimation''.
Disinfection By-product Information        EPA.
 Collection Rule (DBP ICR).
``Evaluating the extent of                 Batt et al. 2016.
 pharmaceuticals in surface waters of the
 United States using a National-scale
 Rivers and Streams Assessment survey''.
``Expanded target-chemical analysis        Bradley et al. 2017.
 reveals extensive mixed-organic-
 contaminant exposure in U.S. streams''.
Federal Insecticide Fungicide, and         EPA.
 Rodenticide Act (FIFRA) List.
``Legacy and emerging perfluoroalkyl       Sun et al. 2016.
 substances are important emerging water
 contaminants in the Cape Fear River
 Watershed of North Carolina''.
National Health and Nutrition Examination  CDC.
 Survey (NHANES).
National Inorganics and Radionuclides      EPA.
 Survey (NIRS).
National Water Information System (NWIS).  Water Quality Portal, USGS.
National Water-Quality Assessment (NAWQA)  Water Quality Portal, USGS.
``Nationwide reconnaissance of             Glassmeyer et al. 2017.
 contaminants of emerging concern in
 source and treated drinking waters of
 the United States''.
``Nationwide reconnaissance of             Furlong et al. 2017.
 contaminants of emerging concern in
 source and treated drinking waters of
 the United States: Pharmaceuticals''.

Pesticide Data Program...................  U.S. Department of Agriculture (USDA).
Pesticide Use Estimates..................  USGS.
``Pharmaceutical manufacturing facility    Scott et al. 2018.
 discharges can substantially increase
 the pharmaceutical load to US
 wastewaters''.
``Predicting variability of aquatic        Kostich et al. 2010.
 concentrations of human
 pharmaceuticals''.
``Reconnaissance of mixed organic and      Bradley et al. 2018.
 inorganic chemicals in private and
 public supply tapwaters at selected
 residential and workplace sites in the
 United States''.
Surface Water Database (SURF)............  California Department of Pesticide Regulation.
``Suspect screening and non-targeted       Newton et al. 2018.
 analysis of drinking water using point-
 of-use filters''.
Toxics Release Inventory (TRI)...........  EPA.
Unregulated Contaminant Monitoring Rule    EPA.
 (UCMR) Cycles 1-3.
UCMR Cycle 4.............................  EPA.
Unregulated Contaminant Monitoring-State   EPA.
 (UCM-State) Rounds 1 and 2.
----------------------------------------------------------------------------------------------------------------
\1\ References for the data sources listed in Exhibit 4 are provided in Appendix N of the Chemical Technical
  Support Document (USEPA, 2021c).

    To ensure consistency and accuracy of the data across such a large
data directory with a multitude of sources, EPA utilized the
Distributed Structure--Searchable Toxicity Substance Identifiers
(DTXSIDs) and tools provided in EPA's CompTox Chemicals Dashboard
(Williams et al., 2017). This dashboard provides easy access to results
from several models developed by EPA and others that predict toxicity
endpoints, physicochemical properties, and environmental fate and
exposure parameters for specific chemicals, as well as tools to
efficiently and accurately match chemicals with DTXSIDs. With these
tools and identifiers, EPA was able to match a chemical that may have
been reported differently (i.e., with different names or other
identifiers) across CCL 5 data sources to one DTXSID. EPA linked these
identifiers with descriptors that characterize toxicological and
occurrence information, referred to as ``data elements,'' to ensure
that data for each chemical would be available for use in later steps
of the CCL 5 development process. EPA also considered the CompTox
Chemicals Dashboard as a supplemental data source, as described in
Section 2.4.3 of the Chemical Technical Support Document (USEPA,
2021c).
    While building the CCL 5 Chemical Universe, EPA took several steps
to ensure that the chemical identifiers were accurate, and that the
data elements gathered across sources were uniform and comparable, as
described in Section 2.4.4 of the Chemical Technical Support Document
(USEPA, 2021c). The result of the first step of the CCL 5 development
process was the CCL 5 Chemical Universe that provided a starting point
for screening chemicals for inclusion on the PCCL 5, as described in
Section III.A.2 of this document.
    At later stages in the CCL 5 development process, EPA also
collected data from supplemental data sources, which, along with data
from the 43 primary data sources, was used to aid in further evaluation
of chemicals for listing on the Draft CCL 5. As described in Section
2.2.3 of the Chemical Technical Support Document (USEPA, 2021c),
supplemental sources were used to fill data gaps as part of the CCL 5
classification step (see Section III.A.3 of this document). For
example, EPA conducted literature searches to identify peer-reviewed
studies that are considered supplemental data sources to aid in the
evaluations of chemicals of interest (see Section III.A.3.a of this
document). Supplemental data could also come from sources cited in
public nominations (see Section III.C of this document). While these
sources could most often not be efficiently or effectively incorporated
into the screening process, they were often an important source of
detail and description that supported CCL 5 listing decisions. This
effort to combine data collected from primary data sources along with
data from supplemental data sources resulted in the most comprehensive
data compilation for universe chemicals collected for any CCL iteration
to date. For more information about the specific iterative steps taken
to build the CCL 5 Chemical Universe, see Chapter 2 of the Chemical
Technical Support Document (USEPA, 2021c).
2. Screening Chemicals to a PCCL
    The goal of the second step of the CCL 5 development process was to
screen chemicals for inclusion on the PCCL 5 using the data compiled in
Step 1. The PCCL 5 is comprised of the top scoring universe chemicals
that were advanced for further evaluation and publicly nominated
chemicals. A number of top scoring chemicals and publicly nominated
chemicals were not included on the PCCL 5 because they had ongoing
agency actions or did not warrant further evaluation, such as canceled
pesticides as described in this section.
a. Screening the Chemical Universe
    EPA developed a screening process to determine which contaminants
require further consideration through the PCCL to CCL step. EPA
modified the CCL 3 screening process for this CCL cycle to accommodate
new data types and sources that have become available, but maintained
the framework of screening chemicals to the PCCL based on their
available toxicity properties and occurrence data (USEPA, 2009b). To
screen chemicals for the CCL 5, EPA developed a transparent and
reproducible scoring rubric and point-based screening system. This
point-based screening system is an improvement over the Toxicity
Categories and Occurrence Hierarchies developed for the CCL 3 (USEPA,
2009b) because it incorporates data from all the available data
elements identified for use in screening rather than relying on an
individual data element that indicates the highest toxicity or
occurrence for a chemical.
    EPA developed a scoring rubric to assign points across health
effects and occurrence data elements based on (1) the relevance of the
data element to drinking water exposure and (2) the relative toxicity
or relative occurrence indicated by the value of a chemical's data
element compared to the values of that data element for all other
chemicals, as described here and in more detail in Section 3.2 of the
Chemical Technical Support Document (USEPA, 2021c). EPA used this
scoring rubric to assign points to health effects and occurrence data
elements and calculate cumulative point scores,

called ``screening scores,'' for each chemical. EPA then used these
screening scores as a tool to prioritize chemicals along with
statistical models and analyses to inform the PCCL 5. The statistical
models and analyses are described in Section III.A.4.d of this document
and Section 4.6 of the Chemical Technical Support Document (USEPA,
2021c). During the CCL 5 development process, EPA compiled 68 different
data elements that could be assigned points or used as supplementary
data for individual chemicals. Of these 68 data elements, EPA assigned
points to 22 data elements related to health effects and 13 data
elements related to occurrence, but did not assign points to the
remaining 33 data elements. Generally, EPA did not assign points to
data elements if:

    The data element was not available for a large number of
chemicals.
    The data element was not considered highly relevant to hazards
associated with drinking water.
    The data element required chemical-specific data manipulation
(e.g., unit conversions requiring chemical molecular weight) and/or
was not comparable to others in the universe.
    Another data element extracted from the same data source and
describing the same data was assigned points.
    Or, the data element was not relevant to unregulated chemicals.

    Many of the data elements assigned points in CCL 5 are the same
data elements that were used in the CCL 3 screening and classification
processes. These data elements include health effects information such
as categories of cancer classifications and toxicity values (e.g.,
Reference Dose (RfD), No Observed Adverse Effect Level (NOAEL), Lowest
Observed Adverse Effect Level (LOAEL), and Lethal Dose, 50% (LD50)), as
well as occurrence information such as measures of chemical
concentration and frequency of detections in drinking water, production
volume, and chemical release data. There are also new data elements
related to both health and occurrence endpoints that EPA included in
the CCL 5 screening process that were not available in a retrievable
format or not used in previous CCL cycles, including National Health
and Nutrition Examination Survey (NHANES) biomonitoring data and
results from EPA's ToxCast in vitro screening assays. EPA designed the
CCL 5 screening process to accommodate quantitative, calculated, and
descriptive types of data. A full list of the data elements assigned
points for the CCL 5 screening process is described in Chapter 3 of the
Chemical Technical Support Document (USEPA, 2021c).
    EPA divided the CCL 5 health effects and occurrence data elements
that were assigned points into five categories, referred to as
``tiers,'' based on the relevance of the data to public health concerns
over drinking water exposure. Tier 1 contains data most relevant to
understanding potential drinking water risk and Tier 5 contains data
that provide indirect indication of potential risk associated with
drinking water exposure. For example, Tier 1 health effects data
elements include RfD, cancer slope factor (CSF), and chronic benchmark
value, which are generally only available for chemicals that have
relevant risk or hazard assessments from at least one health agency.
Tier 1 occurrence data element is the screening Hazard Quotient (sHQ),
a calculated data element based on the ratio of the maximum
concentration of a chemical in finished drinking water (the occurrence
element most applicable to drinking water risk) to the lowest (i.e.,
most health-protective) health screening level for a chemical (see
Section 3.2 of the Chemical Technical Support Document (USEPA, 2021c)
for more details). The list of data elements assigned points for CCL 5
screening purposes and their corresponding tier is presented in Exhibit
5.

 Exhibit 5--Tiers of Health and Occurrence Data Elements Assigned Points
                   During the CCL 5 Screening Process
------------------------------------------------------------------------
           Tier                             Data element
------------------------------------------------------------------------
                      Health Effects Data Elements
------------------------------------------------------------------------
Tier 1...................  Reference dose (RfD), cancer slope factor
                            (CSF), chronic benchmark.
Tier 2...................  Chronic no observed adverse effect level
                            (NOAEL), chronic lowest observed adverse
                            effect level (LOAEL).
Tier 3...................  Numeric cancer classification,\1\ subchronic
                            benchmark, subchronic RfD.
Tier 4...................  Acute benchmark, acute RfD, subchronic NOAEL,
                            subchronic LOAEL, MRDD, mined literature for
                            neurotoxins,\2\ human neurotoxicants,\2\
                            developmental neurotoxins,\2\ developmental
                            neurotoxins (in vivo),\2\ androgen receptor
                            chemicals.\2\
Tier 5...................  TD50, LD50, percent active in ToxCast
                            assays,\2\ PubMed articles.\2\
------------------------------------------------------------------------
                        Occurrence Data Elements
------------------------------------------------------------------------
Tier 1...................  Screening hazard quotient.
Tier 2...................  National finished water detection rates.
Tier 3...................  National ambient water detection rates, non-
                            national finished water detection rates.
Tier 4...................  Non-national ambient water detection rates.
Tier 5...................  Chemical release quantity, estimated
                            pesticide application rate, chemical
                            production volume, presence on FIFRA and
                            CERCLA lists, NHANES blood, urine, and serum
                            concentrations, OPERA model biodegradation
                            half-life.\2\
------------------------------------------------------------------------
\1\ EPA converted categorial cancer classifications to a numeric scheme
  (1-3) which were assigned screening points. See Section 2.4.4 of the
  Chemical Technical Support Document (USEPA, 2021c) for more
  information.
\2\ These data elements were extracted from the CompTox Chemicals
  Dashboard.

A more detailed discussion on the inclusion and exclusion of data
elements for point assignment is included in Chapter 3 of the Chemical
Technical Support Document (USEPA, 2021c).
    For a specific chemical, the number of points assigned to each
individual data element depends on the relative toxicity or relative
occurrence indicated by the data element compared to values of that
data element available for all other chemicals in the universe. Further
descriptions of data element category calculations and point
assignments can be found in Section 3.3.2 of the Chemical Technical
Support Document (USEPA, 2021c). Altogether, a chemical can receive
points for each data element in every tier. The lower tiers of
information are assigned fewer points because the data elements
included in these tiers are considered less relevant

to hazards associated with chemical exposure via drinking water.
    EPA developed the screening points system to ensure the agency
considers chemicals of emerging concern in drinking water in addition
to well-studied chemicals with more robust human health and drinking
water occurrence data. The point system allows a chemical with limited
health effects data, but high occurrence, to be included on the PCCL 5.
Similarly, a chemical with limited or no drinking water occurrence data
but with health effects information potentially indicating higher
toxicity could also be included in the PCCL. The screening score for a
chemical is the sum of health effects and occurrence points assigned
for each data element. The maximum screening score a chemical could be
assigned is 14,050.
    EPA identified the 250 highest scoring chemicals for inclusion in
the PCCL 5 and further evaluation for listing on the Draft CCL 5. This
resulted in all chemicals scoring at or above 3,320 points were
advanced for further consideration for the Draft CCL 5. Because three
chemicals (2,4-Dinitrophenol, Phosmet, and 4-Androstene-3,17-dione)
have the same screening score of 3,320, a total of 252 chemicals were
advanced for further consideration and potential inclusion on the PCCL
5 (Note: The 252 chemicals are referred to as the ``top 250'' in this
document). EPA validated the selection of the top 250 highest scoring
chemicals and the screening score framework using a statistical
modeling approach. A complete description of the results of this
approach can be found in Section 4.6 of the Chemical Technical Support
Document (USEPA, 2021c).
b. Publicly Nominated Chemicals
    EPA added 53 publicly nominated chemicals to the 252 highest
scoring chemicals to be included on the PCCL. Publicly nominated
chemicals are described further in Section III.C of this document and
Section 3.6 of the Chemical Technical Support Document (USEPA, 2021c).
c. Chemicals Excluded From the PCCL
i. Regulatory Determinations
    In March 2021, under the fourth Regulatory Determination process,
EPA made final regulatory determinations for eight chemicals including:
PFOS; PFOA; 1,1-dichloroethane; acetochlor; methyl bromide
(bromomethane); metolachlor; nitrobenzene; and RDX (86 FR 12272, USEPA,
2021b). EPA also made a preliminary positive determination on strontium
under the third Regulatory Determination process (79 FR 62715, USEPA,
2014). Therefore, EPA excluded these nine chemicals from the PCCL 5.
ii. Canceled Pesticides
    EPA evaluated canceled pesticides and excluded those that are not
persistent in the environment from the PCCL 5. The persistence and
occurrence of canceled pesticides were evaluated by their
biodegradation half-life, end-of-use date, and the timeframe of
monitoring data in finished and/or ambient water. Canceled pesticides
were assigned a persistence score based on the scale described in EPA's
2012 TSCA Work Plan Chemicals: Methods Document (USEPA, 2012b).
Canceled pesticides' biodegradation half-life information was
downloaded from EPA's CompTox Chemicals Dashboard. Based on half-life
ranges, a persistence score of 1 to 3 was assigned to each canceled
pesticide with 1 indicative of lowest persistence and 3 highest
persistence. A canceled pesticide received a persistence score of 1, 2,
or 3 if its half-life was less than two months, greater than or equal
to two months, or greater than six months, respectively.
    Additionally, end-of-use dates of canceled pesticides were compared
to the dates of occurrence monitoring data in finished and/or ambient
water. Only the occurrence monitoring data collected after the end-of-
use dates were used to determine if a canceled pesticide had any
detects and/or data spikes that would pose a public health concern. A
canceled pesticide was included in the PCCL if it received a
persistence score of 3 and had detects in finished or ambient water, or
if it received a score of 1 or 2 but had detects in finished water. A
canceled pesticide was excluded from the PCCL if it received a score of
1 or 2 and had no detects in finished water or no or few detects in
ambient water.
    In total, 26 canceled pesticides were assessed for persistence.
Four pesticides, including dieldrin, aldrin, chlordecone (kepone), and
ethion, were assigned a persistence score of 3 and showed detects in
finished or ambient water; thus, they were included in the PCCL 5.
Alpha-hexachlorocyclohexane, although received a persistence score of
1, was also included in the PCCL 5 because it had detects in the UCMR 4
occurrence data (collected 2018-2019). Alpha-hexachlorocyclohexane is
an organochloride, which is one of the isomers of
hexachlorocyclohexane, and is a byproduct of the production of the
canceled insecticide lindane.
    The 21 remaining pesticides were assigned a score of 2 or 1 and
showed no or very few detections in finished or ambient water; and
therefore were excluded from the PCCL 5. Their finished or ambient
water monitoring results were consistent with the low persistence
scores, indicating that these canceled pesticides are likely of low
public health concern.
d. Summary of the PCCL
    The resulting PCCL 5 is comprised of a total of 275 chemicals. As
shown in Exhibit 6, the PCCL 5 includes 252 of the highest scoring
chemicals and 53 publicly nominated chemicals, of which 30 were
excluded because they had other ongoing agency actions or did not
warrant further evaluation. A summary of the PCCL 5 is included in
Section 3.8 of the Chemical Technical Support Document (USEPA, 2021c).

       Exhibit 6--Chemical Counts on Draft PCCL 5 and Draft CCL 5
------------------------------------------------------------------------
                                       Number of
         Counting process              chemicals         Total count
------------------------------------------------------------------------
Highest scoring chemicals                      252  275 (PCCL).
 (screened from Universe).
(+) Add public nominated chemicals              53
 (not screened).
(-) Exclude chemicals with                       9
 Regulatory Determinations.
(-) Exclude canceled pesticides...              21
(-) Exclude Disinfection                        23  214 (Reviewed by
 Byproducts (listed as a chemical                    Evaluation Teams).
 group instead).
(-) Exclude cyanotoxins (listed as               7
 a chemical group instead).
(-) Exclude PFAS (listed as a                   18
 chemical group instead).
(-) Exclude public nominated                    13
 chemicals lacking occurrence Data.
Evaluation Teams' Listing           ..............  66.
 Recommendation.
    Draft CCL 5 Chemicals.........  ..............  66 and 3 groups.
------------------------------------------------------------------------

3. Classification of PCCL Chemicals To Select the Draft CCL
    In the third step of the CCL 5 process, chemical contaminants
screened to the PCCL 5 in Step 2 passed through a classification
process. Classification is the process by which the agency incorporates
the knowledge and evaluation of EPA scientists, referred to as
``chemical evaluators,'' to narrow the PCCL down to a draft CCL. During
this process, chemical evaluators assessed health and occurrence data
on the PCCL 5 chemical contaminants and reached a consensus on whether
to recommend them for listing on the Draft CCL 5.
    To facilitate the classification process, EPA conducted health and
occurrence literature searches to gather supplemental data for the
remaining PCCL 5 chemicals. For more information, see Sections
III.A.3.i and III.C.2 of this document, and Section <IP_ADDRESS> of the
Chemical Technical Support Document (USEPA, 2021c).
    Literature searches acquired supplemental health effects and/or
occurrence data from qualifying studies that may not have been
available in a retrievable format during the identification of the
universe. The supplemental data resources encountered during the
literature searches were compiled by chemical, and relevant health
effects and occurrence data metrics were imported into a standardized
document format, called the Contaminant Information Sheet (CIS) (USEPA,
2021e).
    EPA formed two evaluation teams to review the qualifying health
effects and occurrence information provided in supplemental studies and
on the CISs to make consensus listing recommendations for the PCCL 5
chemicals. Each evaluation team was composed of seven chemical
evaluators with professional experience and expertise in relevant
technical fields, including public health, public policy, toxicology,
chemistry, biology, and pesticide exposure.
    The supplemental studies provided to the chemical evaluators during
the review process can be found in the EPA docket at https://www.regulations.gov (Docket ID No. EPA-HQ-OW-2018-0594). The CISs can
be viewed in the Technical Support Document for the Draft Fifth
Contaminant Candidate List (CCL 5)--Contaminant Information Sheets,
hereafter referred to as the CIS Technical Support Document (USEPA,
2021e).
    The following sections provide a detailed explanation of the
classification process broken down into individual components.
a. Supplemental Data Collection
    Primary data sources play a crucial role in the entire CCL process
(see Section III.A.1 of this document); however, it is often necessary
to gather and extract data from supplemental sources to aid in further
evaluation of chemicals for listing on the Draft CCL 5. As described in
Section III.A.1 of this document, EPA assessed data sources for
potential use in the CCL 5 development process and set aside, as
supplemental sources, those that met the relevance, completeness, and
redundancy assessment factors but were not retrievable. EPA utilized
these supplemental sources to fill data gaps as part of the CCL
classification process. EPA also identified supplemental sources from
data sources cited in public nominations (see Section III.C.1 of this
document) and conducted literature searches to identify further
supplemental occurrence and health effects data as described in this
section.
i. Occurrence
    For PCCL 5 chemicals that reached the classification step but
lacked national drinking water data within the last 10 years, EPA
conducted a search of peer-reviewed literature relevant to the
occurrence of contaminants in drinking water to identify studies that
provided supplemental occurrence data for drinking water or ambient
water not captured in the primary data sources. The literature review
was limited to journal articles published between 2010 and 2020.
    Each of the supplemental data sources was reviewed to determine the
availability of data for any of the PCCL 5 chemicals that required
further evaluation through the CCL 5 classification process. EPA
identified and compiled 12 supplemental literature sources for
contaminant occurrence in drinking and ambient water. All supplemental
occurrence data identified through the literature search were included
in the CISs. More information on CISs can be found in Section III.A.4.c
of this document and in the CIS Technical Support Document (USEPA,
2021e).
    EPA's occurrence literature search was conducted in a systematic
manner to fill the occurrence data gaps for contaminants on the PCCL.
For example, EPA did not conduct occurrence literature searches for
PCCL chemicals that had national drinking water occurrence data from
the UCMR 3 or UCMR 4. These chemicals were considered to already have
the best available occurrence data to inform whether a contaminant was
known to occur in public water systems and therefore supplemental
drinking or ambient water occurrence data was not needed. A full
description of the occurrence literature search protocol and a list of
supplemental occurrence literature utilized for CCL 5 can be found in
the Appendix E of the Chemical Technical Support Document (USEPA,
2021c). In addition to supplemental occurrence data extracted through a
targeted literature search, EPA compiled additional occurrence data
from the 2006 Community Water Systems Survey (CWSS) (USEPA, 2009c;
2009d), EPA's Third Six-Year Review (SYR 3) (USEPA, 2017), and modeled
concentrations from EPA's Office of Pesticide Programs (OPP).
    The 2006 CWSS gathered data on the financial and operating
characteristics of a random sample of CWSs nationwide. Systems serving
more than 500,000 people were included in the sample, and systems in
that size category were surveyed about concentrations of unregulated
contaminants in their raw and finished water. EPA supplemented the data
set by gathering additional information on contaminant occurrence at
the systems in this size category from publicly available sources. The
2006 CWSS was used as supplemental source for the CCL 5 because the
information is not statistically representative for the purpose of the
CCL evaluation. For the SYR 3, EPA requested, through an Information
Collection Request (ICR), that primacy agencies voluntarily submit
drinking water compliance monitoring data collected during 2006-2011 to
EPA. Some primacy agencies submitted occurrence data for unregulated
contaminants in addition to the data on regulated contaminants. EPA
extracted drinking water data on PCCL 5 chemicals from the SYR 3 ICR
data, and supplemented these data by downloading additional publicly
available monitoring data from state websites. These data were used as
a supplemental data source and were included on the CISs.
    Modeled concentration data were gathered for pesticides on the PCCL
5 that lack nationally representative drinking and/or nationally
representative ambient water data. The modeled concentrations, known as
estimated environmental concentrations (EECs) or estimated drinking
water concentrations (EDWCs), of pesticides in water are often included
in EPA's OPP registration and re-registration evaluation documentation,
but are not in a retrievable format that could be efficiently extracted
for all CCL 5 Chemical Universe pesticides.

    Specific information on the systematic occurrence literature
review, SYR 3 ICR, and state occurrence monitoring data sets, 2006 CWSS
data set, and OPP modeled concentrations used in the Draft CCL 5 can be
found in Section 4.2.1 of the Chemical Technical Support Document
(USEPA, 2021c).
    The data search efforts did not yield occurrence data for 13
publicly nominated chemicals that were lacking occurrence data in the
CCL 5 Chemical Universe. As a result, these chemicals were not
evaluated for listing on the Draft CCL 5 (Exhibit 6). More information
is provided on this decision in Section III.C.2 of this document and
Section <IP_ADDRESS> of the Chemical Technical Support Document (USEPA,
2021c).
ii. Health Effects
    EPA developed the rapid systematic review (RSR) protocol to
identify supplemental health effects data for PCCL 5 chemicals. The RSR
process encompassed the identification of health effects information,
including epidemiological and toxicological data, as well as
physiologically-based pharmacokinetic models, and subsequent extraction
of relevant data elements (i.e., NOAELs and LOAELs) that could be used
to derive toxicity values and CCL Screening Levels, further described
in Section III.A.4.b.i of this document. The CCL 5 RSR process was
designed to allow for screening and data synthesis of a large number of
chemicals in a relatively short time frame. As such, the RSR process
was comprised of:
    A targeted chemical-specific literature search;
    Machine learning-based screening to identify relevant literature;
    A streamlined full-text review and study quality evaluation of
relevant literature; and,
    Data extraction components of traditional systematic reviews.
    Studies targeted by the RSR literature search included those deemed
relevant to health effects found in animal models after repeated oral
exposure lasting at least 28 days. Epidemiological studies were also
identified and catalogued for future use (i.e., for Regulatory
Determination). If available, NOAELs and LOAELs, along with their
corresponding health effects, were extracted from all relevant studies.
These toxicity values were populated on the CISs and were used as a
supplemental source of information for chemical evaluators to
understand potential health effects that could result from chronic
exposure to PCCL 5 chemicals. A detailed description of the RSR process
can be found in Section 4.2.1 of the Chemical Technical Support
Document (USEPA, 2021c).
b. Calculated Data Elements
i. Health Reference Levels and CCL Screening Levels
    Health Reference Levels (HRLs) and CCL Screening Levels are
referred to collectively as ``health concentrations.'' Health
concentrations are non-regulatory health-based toxicity values,
expressed as concentrations of a contaminant in drinking water (in
[mu]g/L), which a person could consume over a lifetime and be unlikely
to experience adverse health effects. HRLs are based on data elements
(toxicity values including RfD, population-adjusted dose (PAD), CSF,
etc.) extracted from ``qualifying'' health assessments, peer-reviewed,
publicly available health assessments published by EPA and other health
agencies. Assessments used to derive HRLs generally follow methodology
that is consistent with EPA's current guidelines and guidance
documents, are externally reviewed by experts in the field, and have
been used during EPA regulatory efforts in the past. CCL Screening
Levels are based on data elements (toxicity values including RfD
equivalents, CSF equivalents, etc.) extracted from ``non-qualifying''
health assessments, publicly available assessments that are published
by health agencies and provide valuable health information, but do not
necessarily follow standard EPA methodologies and/or are not externally
peer-reviewed. Alternatively, CCL Screening Levels can be based on data
elements (NOAEL or LOAEL) extracted from peer-reviewed studies
identified through the CCL 5 RSR process previously described.
    The process for determining the toxicity value most appropriate for
use in deriving the health concentration is similar to the process EPA
uses for Regulatory Determination. Generally, EPA relies on its most
recently published health assessment as the source of these toxicity
values unless a qualifying assessment from another source incorporates
new scientific information published after the publication date of the
most recent EPA health assessment. If no qualifying health assessments
are available, EPA extracts toxicity values from the most recently
published non-qualifying health assessment. If no qualifying or non-
qualifying health assessments are available, EPA relies on toxicity
values extracted from studies identified through the health effects RSR
process.
    For carcinogens, the derived health concentration is the one-in-a-
million cancer risk expressed as a drinking water concentration. For
non-carcinogens, health concentrations are obtained by dividing the RfD
(or equivalent) by an exposure factor, also known as the drinking water
intake (DWI), and multiplying by a 20% relative source contribution
(USEPA, 2000). All health concentrations were converted to units of
[mu]g/L to compare with CCL 5 occurrence concentrations and for use in
derivation of the final Hazard Quotient. If a chemical had no available
qualifying or non-qualifying health assessments or studies identified
through the RSR process, or the available health assessments did not
provide toxicity values, EPA did not derive a health concentration.
    The health concentration used to derive the hazard quotient is
presented on the summary page of the CIS alongside the critical effect
and data element from which it was derived. EPA also provides health
concentrations derived from supplementary assessments on the second
page of the CIS as additional resources. Refer to Section 4.3.1 of the
Chemical Technical Support Document (USEPA, 2021c) for more information
about the sources and process for derivation of CCL 5 health
concentrations.
ii. Final Hazard Quotients
    Final hazard quotients (fHQ) are an important metric used in the
evaluation of PCCL chemicals during the classification step. The fHQ is
the ratio of a chemical's 90th percentile (of detections) water
concentration over its health concentration (HRL or CCL screening
level) at which no adverse effects are expected to occur. The fHQ
serves as a benchmark for chemical evaluators to gauge the potential
level of concern posed by the exposure to each chemical in drinking
water.
    A relatively higher fHQ value for a given chemical can generally be
interpreted as an increase to the level of concern for exposure to the
chemical in drinking water; as the ratio increases beyond 0, the
expected exposure concerns also increase; an fHQ value equal to or
greater than 1.0 indicates a chemical with water concentration
exceeding its health concentration.
    EPA followed the CCL 3 and CCL 4 protocol to select the
concentration input values for the ratio as closely as possible while
incorporating newly available data sources. Depending on data
availability, the fHQ was calculated by first using the 90th percentile
of detections from national drinking water monitoring data sources,
such as UCMR.

If the 90th percentile was not available, EPA used the next highest
percentile (95th or 99th) or maximum reported concentration value. For
contaminants that lacked finished water data but had robust ambient
water monitoring data from sources such as NAWQA, the ratio was
developed by using the ambient water concentration. Similarly, if the
90th percentile was not available, the next highest percentile or
maximum reported concentration was used. If no measured water data were
available, EPA used modeled water data for pesticides developed by
EPA's OPP to calculate the fHQ. For contaminants with no water data
(either measured or modeled), the occurrence to health concentration
ratio could not be calculated and the entry for the fHQ was left blank
on the CIS.
    Similarly, HRLs were the preferred health concentration used to
derive the fHQ. If a chemical did not have data available to calculate
an HRL, a CCL screening level was used to derive the fHQ. For chemicals
with no relevant health effects data (i.e., no HRL or CCL screening
level), the occurrence to health concentration ratio could not be
calculated and the entry for the fHQ was left blank on the CIS.
    A more detailed description of the protocol used to calculate the
final hazard quotients for CCL 5 can be found in Section 4.3.2 the
Chemical Technical Support Document (USEPA, 2021c).
iii. Attribute Scores
    During the CCL process, EPA evaluates relatively new and emerging
contaminants not currently subject to EPA drinking water regulations.
Some of these contaminants do not have readily available information on
their health effects in humans and animal models and/or their
occurrence in water. Recognizing the need to establish consistent
relationships and enable comparison among different types of data, EPA
developed a scaling system of attribute scores for the CCL 3 based on
recommendations from the National Academy of Science's National
Research Council (NRC, 2001) and the National Drinking Water Advisory
Council (NDWAC, 2004). Attributes are defined as the properties used to
categorize contaminants based on their potential to cause adverse
health effects and occur in drinking water. The associated scores for
these attributes provide a consistent, comparative framework for
evaluation purposes that accommodate a variety of input data.
    The health effects of a contaminant are categorized using the
attributes of potency and severity, while the actual or potential
occurrence of a contaminant is categorized using the attributes of
prevalence and magnitude.
    Potency reflects the potential for a chemical to cause adverse
health effects based on the dose required to elicit the most sensitive
adverse effect. Severity is a descriptive measure of the adverse health
effect associated with the potency score. Unlike the other attributes,
which are numerical, severity is categorical; contaminants are assigned
to one of eight severity categories (non-cancer effects, no adverse
effects, cosmetic effects, carcinogen with a linear mode of action,
carcinogen with a mutagenic mode of action, carcinogen with a non-
linear mode of action, reproductive and developmental effects, or
reduced longevity) depending on the reported health endpoint.
    Prevalence provides some indicator of how widespread the occurrence
of the contaminant is in the environment, such as the percentage of
public water systems or sample locations in a study reporting
detections.
    Magnitude describes the quantity of a contaminant that may be in
the environment (e.g., median concentration of detections or pounds
applied annually). When direct occurrence data are not available, EPA
uses Persistence-Mobility data as surrogate indicators of potential
occurrence of a contaminant. Persistence-Mobility is defined by
chemical properties that measure or estimate environmental fate
characteristics of a contaminant and affect their likelihood to occur
in water.
    EPA used the attribute scoring developed for CCL 3 to evaluate PCCL
5 chemicals, with some adjustments made to the calibrations for potency
and descriptions for severity. Those adjustments, along with the
scoring scales and categories, are explained in detail in the Chemical
Technical Support Document (USEPA, 2021c).
c. Evaluation Team Listing Decision Process
    The EPA scientists on the two evaluation teams shared a broad range
of professional experience and expertise across the agency and with the
CCL process. These ``chemical evaluators'' were provided training,
which included a detailed overview of the goals and general principles
of the CCL process, types of data, and materials compiled to aid in
evaluating chemicals for listing, the evaluation process steps, and the
format of the discussion meetings. Of the 275 PCCL 5 chemicals, the
evaluation teams reviewed 214 chemicals (Exhibit 6). The evaluation
teams did not review 7 cyanotoxins, 23 DBPs, and 18 PFAS chemicals
because they were listed as three chemical groups on the Draft CCL 5
(as discussed further in Section III.A.3.e of this document).
Additionally, the evaluation teams did not evaluate the 13 publicly
nominated chemicals due to lack of occurrence data.
    The chemical evaluators on the two evaluation teams met over 20
times between March 19 and July 2, 2020, to discuss their individual
reviews and reach consensus listing decisions as a group for batches of
approximately 10-20 chemicals per batch. To prepare for these
discussion meetings, the chemical evaluators independently reviewed the
relevant health effects and occurrence information on CISs for each
chemical in a batch. For each chemical on the PCCL 5 that was evaluated
for potential listing, a CIS was developed to summarize the data and
assist the chemical evaluators in making listing recommendations for
the Draft CCL 5. Each CIS presents the health and occurrence data
gathered from primary and supplemental data sources, as well as health
and occurrence statistical measures described in Section III.A.4.b of
this document. CISs also include additional information about the
contaminant, such as the identity of the contaminant and its usage,
whether it was subject to past negative regulatory determinations,
listed on past CCLs, and publicly nominated for the CCL 5. Due to the
inclusion of more data in the CCL 5 process, CISs for the Draft CCL 5
contain more information than those of past CCLs. CISs for contaminants
evaluated for the Draft CCL 5 and further information on what data the
CISs provide can be found in the CIS Technical Support Document (USEPA,
2021e).
    Upon completing their independent reviews, the chemical evaluators
submitted their listing decisions along with written justifications
through a survey tool. The results from the survey were collected and
tabulated before each facilitated group discussion. Numerical values
were assigned to the individual evaluator's listing decision for each
chemical (i.e., 1 = No List, 2 = No List?, 3 = List?, and 4 = List) so
that an average listing decision could be calculated. A question mark
(?) signified that the chemical evaluator was leaning toward listing
(List?) or toward not listing (No List?) but had some uncertainty.
These average listing decisions helped inform the facilitator and the
chemical evaluators of their collective decisions and guided the teams
towards making the final listing recommendations for each chemical. In
total, the evaluation teams recommended 66 chemicals for listing on the
Draft CCL 5. A more detailed

description of the team listing process can be found in Section 4.5 of
the Chemical Technical Support Document (USEPA, 2021c).
d. Logistic Regression
    EPA conducted statistical analyses and developed a simple logistic
regression model to validate the selection of the top 250 highest
scoring chemicals for inclusion on the PCCL 5 and provide diagnostic
feedback on the screening system during the evaluation team meetings.
EPA hypothesized that screening scores have a positive association with
listing decisions, and that the higher the screening score of a PCCL 5
chemical, the higher the probability of the chemical being recommended
for listing by the evaluation teams. Additional analyses and logistic
regression models were developed to further examine the efficacy of the
screening scores and to determine additional factors, such as fHQs and
health and occurrence attribute scores, associated with listing
decisions.
    The simple logistic regression models the statistical relationship
between screening scores and the evaluation teams' list or not list
decision. The model was used to obtain probabilities of listing at the
highest screening score (top of the PCCL 5) and screening score
directly below the PCCL 5 top 250. Results of this analysis indicate
chemicals with higher screening scores are more likely to be listed
than chemicals with lower screening scores. The predicted mean
probability of listing at the top of the PCCL 5 is 0.90 and at the
screening score directly below the PCCL 5 top 250 is 0.12. A full
description of the modeling approach and results can be found in
Section 4.6.2 of the Chemical Technical Support Document (USEPA,
2021c).
    Following the evaluation team decisions, EPA explored other factors
that may have impacted listing decisions and further evaluated how well
the screening scores performed as a predictor of listing decisions. To
accomplish this, EPA compiled a dataset that contained the chemical
screening scores, health effects and occurrence attribute scores, fHQs,
and other information. See Section 4.6.1 of the Chemical Technical
Support Document (USEPA, 2021c) for details on the compiled dataset
used in the statistical analyses. The first step of the analysis was to
calculate descriptive statistics for each variable stratified by
listing decision. Next, several simple logistic regression models were
explored to obtain odds ratios (OR) and establish statistical
significance of the predictor variables. Lastly, an area under the
curve-receiver operator characteristic (AUC-ROC) curve analysis was
conducted to examine the performance of simple logistic regression
models and multivariable logistic models as predictors of listing
decisions. The results of the simple logistic regression found the
screening scores, attributes scores, and fHQs (adjusted for outliers)
to be statistically significant predictors of listing decisions. The
AUC-ROC analysis provided further evidence that the screening scores
were a moderate-to-good predictor of listing decisions (AUC = 0.72) and
led to the discovery of a multivariable logistic regression model that
was a very good-to-excellent predictor of listing decisions (AUC =
0.89). A complete description of the results of the statistical
analyses conducted for the Draft CCL 5 can be found in Section 4.6 of
the Chemical Technical Support Document (USEPA, 2021c).
e. Chemical Groups on the Draft CCL 5
    In addition to the 66 chemicals recommended for listing on the
Draft CCL 5 by the evaluation teams (Exhibit 6), EPA proposes to list
three chemical groups (cyanotoxins, DBPs, and PFAS) instead of listing
them as individual chemicals. These chemical groups have been
identified as agency priorities and contaminants of concern for
drinking water under other EPA actions. Listing these three chemical
groups on the Draft CCL 5 does not necessarily mean that EPA will make
subsequent regulatory decisions for the entire group. EPA will evaluate
scientific data on the listed groups, subgroups, and individual
contaminants included in the group to inform any regulatory
determinations for the group, subgroup, or individual contaminants in
the group. Addressing the public health concerns of cyanotoxins in
drinking water remains a priority as specified in the 2015 Algal Toxin
Risk Assessment and Management Strategic Plan for Drinking Water
(USEPA, 2015). Cyanotoxins are toxins naturally produced and released
by some species of cyanobacteria (previously known as ``blue-green
algae''), were listed on the CCL 3 and CCL 4 as a group. EPA is listing
a cyanotoxin group on the Draft CCL 5, identical to the CCL 3 and CCL 4
listing. The group of cyanotoxins includes, but is not limited to:
Anatoxin-a, cylindrospermopsin, microcystins, and saxitoxin.
Cyanotoxins were also monitored under the UCMR 4.
    EPA is also proposing to list 23 unregulated DBPs (as shown in
Exhibit 2b) as a group on the Draft CCL 5. DBPs are formed when
disinfectants react with naturally-occurring materials in water. Under
the Stage 2 Disinfectants and Disinfection Byproducts Rule, there are
currently 11 regulated DBPs from three subgroups that include four
trihalomethanes, five haloacetic acids, and two inorganic compounds
(bromate and chlorite). Under the Six-Year Review 3 (SYR 3), EPA
identified 10 regulated DBPs (all but bromate) as ``candidates for
revision'' (USEPA, 2017). For the Draft CCL 5, the group of 23
unregulated DBPs were either publicly nominated or among the top 250
chemicals. Listing these unregulated DBPs as a group on the Draft CCL 5
would be consistent with the decision that EPA has identified a number
of microbial and disinfection byproduct (MDBP) drinking water
regulations as candidates for revision in the agency's SYR 3 .
    PFAS are a class of synthetic chemicals that are most commonly used
to make products resistant to water, heat, and stains and are
consequently found in industrial and consumer products like clothing,
food packaging, cookware, cosmetics, carpeting, and fire-fighting foam
(AAAS, 2020; USEPA, 2018b). Over 4,000 PFAS have been manufactured and
used globally since the 1940s (USEPA, 2019b), which would make listing
PFAS individually on the Draft CCL 5 difficult and challenging. EPA
proposes to list PFAS as a group inclusive of any PFAS (except for PFOA
and PFOS). For the purposes of this document, the structural definition
of PFAS includes per- and polyfluorinated substances that structurally
contain the unit R-(CF2)-C(F)(R')R''. Both the CF2 and CF moieties are
saturated carbons and none of the R groups (R, R' or R'') can be
hydrogen (USEPA, 2021f). This proposal is responsive to public
nominations which stated that EPA should ``include PFAS chemicals as a
class on CCL 5.'' This action is in keeping with the agency's
commitment to better understand and ultimately reduce the potential
risks caused by this broad class of chemicals. Including the broad
group of PFAS on the Draft CCL 5 demonstrates the agency's commitment
to prioritizing and building a strong foundation of science on PFAS
while working to harmonize multiple authorities to address the impacts
of PFAS on public health and the environment. EPA is also committed to
a flexible approach and working collaboratively with states, tribes,
water systems, and local communities that have been impacted by PFAS.

B. Approach Used To Identify Microbial Candidates for the Draft CCL 5

1. Building the Microbial Universe
    EPA defined the microbial Universe for the CCL 5 as all known human
pathogens. The microbial Universe was built on the CCL 3 and the CCL 4
Universe of 1,425 pathogens. EPA conducted a literature search, sought
input from subject matter experts, and reviewed nominations for
additional microbes to add to the Universe. As a result, 14 organisms
were added to the CCL 5 Microbial Universe (Exhibit 7).
    Changes to nomenclature of the microbes were made as necessary (in
most cases combining two species into one organism group), making the
total number of organisms in the microbial Universe 1,435. The full CCL
5 microbial Universe list is available in the Technical Support
Document for the Draft fifth Contaminant Candidate List (CCL 5)--
Microbial Contaminants (USEPA, 2021d).

  Exhibit 7--Microbial Contaminants Added to the Microbial Universe for
                                the CCL 5
------------------------------------------------------------------------
           Microbial contaminant                    Microbe class
------------------------------------------------------------------------
Alloscardovia omnicolens...................  Bacteria.
Elizabethkingia anophelis..................  Bacteria.
Neoehrlichia mikurensis....................  Bacteria.
Parachlamydia acanthamoebae................  Bacteria.
Waddia chondrophila........................  Bacteria.
Human bocavirus............................  Virus.
Human coronavirus SARS-CoV-2...............  Virus.
KI polyomavirus............................  Virus.
Kobuvirus..................................  Virus.
Lujo virus.................................  Virus.
Parovovirus 4..............................  Virus.
WU polyomavirus............................  Virus.
Botrytsis cinerea..........................  Fungi.
Epiccocum purpurascens.....................  Fungi.
------------------------------------------------------------------------

2. Screening the Microbial Universe to the PCCL
    During the CCL 3 process, EPA developed 12 screening criteria
(Exhibit 8) to focus the Universe of all human pathogens to only those
pathogens that could be transmitted through drinking water. Screening
is based on a pathogen's epidemiology, geographical distribution, and
biological properties in their host and in the environment. All
pathogens that are not excluded by any screening criteria are moved to
the PCCL. In addition, any pathogen documented to cause disease
transmitted through drinking water regardless of the screening
criteria, is also considered for the PCCL. 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. For the Draft CCL 5, EPA re-
evaluated the screening criteria for applicability to microbes and
reviewed certain criterion in depth per recommendations received from
the SAB and stakeholders during the development of the CCL 3 and the
CCL 4. In particular, Criterion 1 (anaerobes), Criterion 9 (natural
habitat is in the environment without epidemiological evidence of
drinking water-related disease) and Criterion 10 (not endemic to North
America) were closely re-evaluated based on previous comments for the
CCL 3 and the CCL 4 from NDWAC, SAB, and the public. Upon further
evaluation, EPA did not find supporting evidence to modify Criterion 1
and Criterion 10.
    EPA modified the screening Criterion 9 to include pathogens on the
PCCL with nosocomial infections where drinking water is implicated due
to recent increases in and recognition of antimicrobial resistance and
nosocomial infections. Modifying Criterion 9 addresses a SAB comment
that the screening criteria for the CCL 4 microbial process were too
restrictive. As a result, Criterion 9 was modified to include pathogens
that cause nosocomial infections where drinking water is implicated so
that it is less restrictive.

               Exhibit 8--Screening Criteria for Pathogens
------------------------------------------------------------------------

-------------------------------------------------------------------------
All anaerobes.
Obligate intracellular fastidious pathogens.
Transmitted by contact with blood or body fluids.
Transmitted by vectors.
Indigenous to the gastrointestinal tract, skin and mucous membranes.
Transmitted solely by respiratory secretions.
Life cycle incompatible with drinking water transmission.
Drinking water-related transmission is not implicated.
Natural habitat is in the environment without epidemiological evidence
 of drinking water-related disease and without evidence of drinking
 water-related nosocomial infection.
Not endemic to North America.
Represented by a pathogen for the entire genus or species (that are
 closely related).
Current taxonomy changed from taxonomy used in Universe.
------------------------------------------------------------------------
 Bolded text indicates the modification made to Criterion 9.

    Based upon the screening criteria, 1,400 of the 1,435 pathogens
were excluded; therefore 35 pathogens advanced to the PCCL. The results
of the screening process are summarized in Exhibit 9. The criteria and
results of the screening process are discussed in greater detail in the
Technical Support Document for the Draft Fifth Contaminant Candidate
List (CCL 5)--Microbial Contaminants (USEPA, 2021d).

                                                   Exhibit 9--Application of 12 Screening Criteria to Pathogens in the Microbial CCL Universe
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Screening criteria and number of pathogens screened out per criterion               Pathogens
              Pathogen class                            Total            ------------------------------------------------------------------------------------------------   screened    On PCCL
                                                                             1       2       3       4       5       6       7       8       9      10      11      12        out
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Bacteria..................................  545.........................     121      16      10      38     121       7       0      29     150       2      28       5          527     \1\ 18
Viruses...................................  225.........................       0       0      29     104       0      20       1      20       0      36       8       0          218          7
Protozoa \2\..............................  66..........................       0       0       1      29       3       0       4       7       7       0       6       0           59          7
Helminths.................................  286.........................       0       0       0      25       0       0     105       0       0     156       0       0          286          0

Fungi.....................................  313.........................       0       0       0       0      12       3       0       0     295       0       0       0          310          3
                                           -----------------------------------------------------------------------------------------------------------------------------------------------------
    Total.................................  1,435.......................     121      16      40     196     136      30     110      56     452     194      42       5        1,400         35
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ NTM are included on the PCCL as a group.
\2\ Cryptosporidium and Giardia (both protozoa) are considered to be regulated by the Long Term Surface Water Treatment Rule (LT-2); even though counted in the Microbial universe, they were
  not evaluated for screening.

3. The PCCL to Draft CCL Process
    Pathogens on the PCCL were scored for placement on the Draft CCL 5.
In developing the CCL 3, EPA devised a scoring system to assign a
numerical value to each pathogen on the PCCL. Each pathogen 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
was 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 had equal weight in determining the ranking of the Draft
CCL. The equal weighting of occurrence and health effects information
closely mirrors the risk estimate methods used by EPA in 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 reevaluation. It is important to note that
pathogens for which there are no documented WBDO in drinking water earn
a low score under the protocols. Pathogens that have caused a WBDO and
have health effects data are rank higher than pathogens that only have
health effect data but no evidence of a WBDO. The following sections
describe the three protocols used to score the pathogens on the PCCL
and the process by which the scores are combined.
a. Waterborne Disease Outbreak (WBDO) 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 occurrence and causes of WBDOs since 1971. In
recent years, CDC has developed National Outbreak Reporting System
(NORS) (CDC, 2020a) for WBDO reporting, in collaboration with CSTE and
EPA, to improve the quality, quantity, and availability of data
submitted to the Waterborne Disease and Outbreak Surveillance System
(WBDOSS). For the Draft CCL 5, EPA used CDC's NORS as the primary data
source for the WBDO protocol. Reports from the CDC system were
published periodically in Morbidity and Mortality Weekly Report (MMWR)
until 2017. For the CCL 3 and the CCL 4, EPA used MMWRs for the WBDO
protocol.
    For the Draft CCL 5, EPA used CDC's NORS for more recent outbreak
information due to the most recent MMWR being published in 2014. For
the WBDO protocol (Exhibit 10), 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., on NORS from 2009-
2017). Outbreaks that occurred in 2009 and after were used to capture
microbes causing concern since the publication of the CCL 3. A pathogen
with multiple WBDOs listed by CDC was given the highest score under
this protocol. In addition, EPA scored non-CDC reported WBDOs and WBDOs
outside the U.S. with lower scores. WBDOs outside the U.S. were scored
when information was available from World Health Organization 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, 2008). 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 the non-CDC
data as indicating a WBDO (even though CDC did not list it in their
NORS) if the data showed a link between human illness defined by a
common water source, a common time period of exposure and/or similar
symptoms. Additionally, EPA considered the use of molecular typing
methods to link patients and environmental isolates.

        Exhibit 10--Waterborne Disease Outbreak Scoring Protocol
------------------------------------------------------------------------
                           Category                              Score
------------------------------------------------------------------------
Has caused multiple (2 or more) documented WBDOs in the U.S.           5
 as reported by CDC surveillance between 2009-2017...........
Has caused at least one documented WBDO in the U.S. as                 4
 reported by CDC surveillance 2009-2017......................
Has caused documented WBDOs at any time in the U.S...........          3
Has caused documented WBDOs in countries other than the U.S..          2
Has never caused WBDOs in any country, but has been                    1
 epidemiologically associated with water-related disease.....
------------------------------------------------------------------------

b. Occurrence Protocol
    The second attribute of the scoring process evaluates the
occurrence of a pathogen in drinking water and source 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 11). 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 cause

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, ground water, and surface water bodies. This
attribute does not characterize the extent to which a pathogen's
occurrence poses a public health threat from drinking water exposure.

     Exhibit 11--Occurrence and Health Effects Scoring Protocols for
                                Pathogens
------------------------------------------------------------------------
                           Category                              Score
------------------------------------------------------------------------
Occurrence Scoring Protocol:
    Detected in drinking water in the U.S.                             3
    Detected in source water in the U.S.                               2
    Not detected in the U.S.                                           1
Health Effects Scoring Protocol:
    Does the organism cause significant mortality (>1/1,000            7
     cases)?.................................................
    Does the organism cause pneumonia, meningitis, hepatitis,          6
     encephalitis, endocarditis, cancer, or other severe
     manifestations of illness necessitating long term
     hospitalization (>week)?................................
    Does the illness result in long term or permanent                  5
     dysfunction or disability (e.g., sequelae)?.............
    Does the illness require short term hospitalization?               4
     (https://www.regulations.gov (Docket ID No. EPA-HQ-OW-2018-0594). A more
detailed summary of the nomination process is included in Section 3.6
of the Chemical Technical Support Document (USEPA, 2021c) and in
Section 2.1 of the Microbial Technical Support Document (USEPA, 2021d).

     Exhibit 13--Contaminants Nominated for Consideration on the Draft CCL 5: Nominated Chemical Contaminant
----------------------------------------------------------------------------------------------------------------
                     Chemical name                            CASRN                       DTXSID
----------------------------------------------------------------------------------------------------------------
1,1-Dichloroethane.....................................          75-34-3  DTXSID1020437
1,4-Dioxane............................................         123-91-1  DTXSID4020533
1-Phenylacetone \1\....................................         103-79-7  DTXSID1059280
2-(N-Methylperfluorooctane sulfonamido)acetic acid (Me-        2355-31-9  DTXSID10624392
 PFOSA-AcOH).
2-(N-Ethyl perfluorooctane sulfonamido) acetic acid (Et-       2991-50-6  DTXSID5062760
 PFOSA-AcOH).
2-[(8-Chloro-1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8-                763051-92-9  DTXSID40892507
 Hexadecafluorooctyl)oxy]-1,1,2,2-tetrafluoroethane-1-
 sulfonic acid (11Cl-PF3OUdS).
3-Hydroxycarbofuran....................................       16655-82-6  DTXSID2037506
3-Monoacetylmorphine \1\...............................       29593-26-8  DTXSID30183774
4,8-Dioxa-3H-perfluorononanoic acid (ADONA)............      919005-14-4  DTXSID40881350
6-Monoacetylmorphine \1\...............................        2784-73-8  DTXSID60182154
Ammonium perfluoro-2-methyl-3-oxahexanoate.............       62037-80-3  DTXSID40108559
Anatoxin A.............................................       64285-06-9  DTXSID50867064
Azinphos-methyl........................................          86-50-0  DTXSID3020122
Benzoic acid \1\.......................................          65-85-0  DTXSID6020143
Benzoic acid glucuronide \1\...........................       19237-53-7  DTXSID90940901
Bromochloroacetic acid (BCAA)..........................        5589-96-8  DTXSID4024642
Bromochloroiodomethane (BCIM)..........................       34970-00-8  DTXSID9021502
Bromodichloroacetic acid (BDCAA).......................       71133-14-7  DTXSID4024644
Bromodichloronitromethane (BDCNM)......................         918-01-4  DTXSID4021509
Bromodiiodomethane (BDIM)..............................         557-95-9  DTXSID70204235
Chlorate...............................................       14866-68-3  DTXSID3073137
Chlorodibromoacetic acid (CDBAA).......................        5278-95-5  DTXSID3031151
Chloro-diiodo-methane (CDIM)...........................         638-73-3  DTXSID20213251
Chloropicrin (trichloro-nitromethane; TCNM)............          76-06-2  DTXSID0020315
Chlorpyrifos...........................................        2921-88-2  DTXSID4020458
Cylindrospermopsin.....................................      143545-90-8  DTXSID2031083
Dibromochloronitromethane (DBCNM)......................        1184-89-0  DTXSID00152114
Dibromoiodomethane (DBIM)..............................         593-94-2  DTXSID60208040
Dichloroiodomethane (DCIM).............................         594-04-7  DTXSID7021570
Fluoxetine.............................................        5491-89-3  DTXSID7023067
Gemfibrozil............................................       25812-30-0  DTXSID0020652
Heroin.................................................         561-27-3  DTXSID6046761
Hippuric acid \1\......................................         495-69-2  DTXSID9046073
Hydromorphone \1\......................................         466-99-9  DTXSID8023133
Hydromorphone-3-glucuronide \1\........................         No CASRN  NO_DTXSID
Hydroxyamphetamide \1\.................................         103-86-6  DTXSID3023134
Isodrin (Pholedrine, 4-Hydroxymethamphetamine) \1\.....         465-73-6  DTXSID7042065
Manganese..............................................        7439-96-5  DTXSID2024169
Methamphetamine \1\....................................         537-46-2  DTXSID8037128
Microcystin LA.........................................       96180-79-9  DTXSID3031656
Microcystin LR.........................................      101043-37-2  DTXSID3031654
Microcystin LW.........................................         No CASRN  DTXSID70891285
Microcystin RR.........................................      111755-37-4  DTXSID40880085
Microcystin YR.........................................      101064-48-6  DTXSID00880086
Molybdenum.............................................        7439-98-7  DTXSID1024207
Morphine...............................................          57-27-2  DTXSID9023336
Morphine-3-glucuronide.................................       20290-09-9  DTXSID80174157
Morphine-6-glucuronide \1\.............................       20290-10-2  DTXSID40174158
N-Nitrosodiethylamine (NDEA)...........................          55-18-5  DTXSID2021028
N-Nitrosodimethylamine (NDMA)..........................          62-75-9  DTXSID7021029
N-Nitroso-di-n-propylamine (NDPA)......................         621-64-7  DTXSID6021032
N-Nitrosodiphenylamine (NDPhA).........................          86-30-6  DTXSID6021030
N-Nitrosopyrrolidine (NPYR)............................         930-55-2  DTXSID8021062
Perfluoro(2-((6-chlorohexyl)oxy)ethanesulfonic acid)         756426-58-1  DTXSID80892506
 (9Cl-PF3ONS).
Perfluoro-2-methyl-3-oxahexanoic acid..................       13252-13-6  DTXSID70880215
Perfluorobutane sulfonic acid (PFBS)...................         375-73-5  DTXSID5030030
Perfluorobutyric acid (PFBA)...........................         375-22-4  DTXSID4059916
Perfluorodecanoic acid (PFDeA/PFDA)....................         335-76-2  DTXSID3031860
Perfluorododecanoic acid (PFDoA).......................         307-55-1  DTXSID8031861
Perfluoroheptanoic acid (PFHpA)........................         375-85-9  DTXSID1037303
Perfluorohexane sulfonic acid (PFHxS)..................         355-46-4  DTXSID7040150
Perfluorohexanoic acid (PFHxA).........................         307-24-4  DTXSID3031862
Perfluoronononanoic acid (PFNA)........................         375-95-1  DTXSID8031863
Perfluorooctanesulfonamide (PFOSA).....................         754-91-6  DTXSID3038939
Perfluorooctane sulfonic acid (PFOS)...................        1763-23-1  DTXSID3031864
Perfluorooctanoic acid (PFOA)..........................         335-67-1  DTXSID8031865
Perfluorotetradecanoic acid (PFTA).....................         376-06-7  DTXSID3059921
Perfluorotridecanoic acid (PFTrDA).....................       72629-94-8  DTXSID90868151
Perfluoroundecanoic acid (PFUA/PFUnA)..................        2058-94-8  DTXSID8047553
Phenylpropanolamine \1\................................       37577-28-9  DTXSID4023466

Strontium..............................................        7440-24-6  DTXSID3024312
Tribromoacetic acid (TBAA).............................          75-96-7  DTXSID6021668
Triiodomethane (TIM)...................................          75-47-8  DTXSID4020743
----------------------------------------------------------------------------------------------------------------
\1\ Thirteen nominated chemicals did not have available water occurrence data, even after a systematic
  literature search was conducted, and therefore were not evaluated for listing on the Draft CCL 5. See Section
  <IP_ADDRESS> of the Chemical Technical Support Document for more information.

                    Nominated Microbial Contaminants
------------------------------------------------------------------------
                             Microbial name
-------------------------------------------------------------------------
Adenovirus.
Aeromonas hydrophila.
Caliciviruses.
Campylobacter jejuni.
Enterovirus.
Escherichia coli (0157).
Helicobacter pylori.
Hepatitis A virus.
Legionella pneumophila.
Mycobacterium species predominantly found in drinking water.
Mycobacterium avium.
Naegleria fowleri.
Non-tuberculous Mycobacterium (NTM).
Pseudomonas aeruginosa.
Salmonella enterica.
Shigella sonnei.
------------------------------------------------------------------------

1. Data Sources for the Nominated Chemical and Microbial Contaminants
a. Chemical Nominations
    EPA reviewed the public nominations for the 73 chemicals and
determined which nominated chemicals were already included in the CCL 5
Chemical Universe and which ones were not. If a chemical was already
part of the CCL 5 Chemical Universe, this meant that EPA had identified
and extracted health effects and occurrence data on this chemical from
primary data sources in Step 1, Building the Chemical Universe.
However, most of these chemicals did not have sufficiently high
screening scores and therefore required additional data to evaluate
them. For the nominated chemicals that were not included in the CCL 5
Chemical Universe, they would require further data collection to be
evaluated for listing on the Draft CCL 5. To identify additional data
for these nominated chemicals, EPA assessed data sources cited with
public nominations using the assessment factors described in Section
III.A.1 of this document and extracted health effects and occurrence
data from sources that were relevant, complete, and not redundant.
Sources that met these three assessment factors were considered
supplemental data sources and could serve as references to fill any
data gaps for particular chemical contaminants during Step 3 of the CCL
5 process (see Section III.A.3 of this document). EPA also conducted
literature searches to identify additional health effects and
occurrence data; more information can be found on the literature
searches in Section III.A.3.a of this document and in Chapter 4 of the
Chemical Technical Support Document (USEPA, 2021c). A complete list of
supplemental sources can be found in Appendix B of the Chemical
Technical Support Document (USEPA, 2021c).
b. Microbial Nominations
    EPA reviewed the nominated microbial contaminants and the
supporting information provided by nominators to determine if any new
data were provided that had not been previously evaluated. EPA also
collected additional data for the nominated microbial contaminants,
when available, from both the CCL 3 and CCL 4 data sources that had
been updated and from literature searches covering the time between the
CCL 4 and the CCL 5 (2016-2019). If new data were available, EPA
screened and scored the microbial contaminants nominated for CCL 5
using the same process that was used for the CCL 3 and the CCL 4. There
were no new publicly nominated microbial data sources for the CCL 5. A
more detailed description of the data sources used to evaluate
microbial contaminants for the Draft CCL 5 can be found in the
Microbial Technical Support Document (USEPA, 2021d).
2. Listing Outcomes for the Nominated Chemical Contaminants
    EPA reviewed the nominated chemical contaminants and identified
which chemicals were (i) not already on the PCCL 5, and (ii) not
subject to proposed or promulgated NPDWRs, and needed to be considered
for further analysis. EPA did not add publicly nominated groups like
``the top 200 most prescribed drugs in 2016 and their parents and
metabolites'' to the PCCL 5 because health effects and occurrence data
must be linked to specific individual contaminants in order to be
evaluated. However, individual chemicals in a nominated group could
still be listed on the PCCL if they were also nominated individually or
if they were part of the CCL 5 Chemical Universe and screened to the
PCCL.
    EPA could not identify occurrence data for 13 nominated chemicals
(Exhibit 13) from either primary or supplemental data sources nor was
data provided in the public nominations. Without available data
regarding measured occurrence in water or relevant data provided by the
nominators, the two evaluation teams agreed that they could not
determine whether these chemicals were likely to present the greatest
public health concern through drinking water exposure and therefore
should not advance further in the CCL 5 process. However, some were
evaluated for possible research needs (see Chapter 5 of the Chemical
Technical Support Document; USEPA, 2021c). More detailed information
about how nominated chemicals were considered for the Draft CCL 5 can
be found in Section 3.6 of the Chemical Technical Support Document
(USEPA, 2021c).