[Federal Register Volume 86, Number 135 (Monday, July 19, 2021)]
[Proposed Rules]
[Pages 37948-37972]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[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 (202) 564-3632 or 
email <a href="/cdn-cgi/l/email-protection#43252c31312630376d2826302b22032633226d242c35"><span class="__cf_email__" data-cfemail="4721283535223433692c22342f260722372669202831">[email protected]</span></a>. For information on microbial contaminants 
contact Nicole Tucker, Office of Ground Water and Drinking Water, 
Standards and Risk Management Division, at (202) 564-1946 or email 
<a href="/cdn-cgi/l/email-protection#0c78796f67697e2262656f6360694c697c6d226b637a"><span class="__cf_email__" data-cfemail="3f4b4a5c545a4d1151565c50535a7f5a4f5e11585049">[email protected]</span></a>.
    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

[[Page 37949]]

    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

[[Page 37950]]

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.

[[Page 37951]]

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.

[[Page 37952]]

[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.

[[Page 37953]]



                              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.

[[Page 37954]]

 
\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

[[Page 37955]]

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 Drugs@FDA 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''.

[[Page 37956]]

 
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,

[[Page 37957]]

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

[[Page 37958]]

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.
------------------------------------------------------------------------


[[Page 37959]]

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 4.2.1.1 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.

[[Page 37960]]

    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 4.2.1.1 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.

[[Page 37961]]

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

[[Page 37962]]

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.

[[Page 37963]]

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

[[Page 37964]]

 
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

[[Page 37965]]

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
     (<week)?................................................
    Does the illness require physician intervention?.........          3
    Is the illness self-limiting within 72 hours (without              2
     requiring medical intervention)?........................
    Does the illness result in mild symptoms with minimal or           1
     no impact on daily activities?..........................
------------------------------------------------------------------------

c. Health Effects Protocol
    EPA's health effects protocol evaluates the extent or severity of 
human illness produced by a pathogen across a range of potential 
endpoints. The seven-level hierarchy developed for this protocol 
(Exhibit 11) begins with mild, self-limiting illness (score of 1) and 
progresses to death (score of 7).
    The final outcome of a host-pathogen relationship resulting from 
drinking water exposure is a function of viability, infectivity, and 
pathogenicity of the microbe to which the host is exposed and the 
host's susceptibility and immune response. SDWA directs EPA to consider 
subgroups of the population at greater risk of adverse health effects 
(i.e., sensitive populations) in the selection of unregulated 
contaminants for the CCL. Sensitive populations may have increased 
susceptibility and may experience increased severity of symptoms, 
compared to the general population. The SDWA refers to several 
categories of sensitive populations including children and infants, 
elderly, pregnant women, and persons with a history of serious illness. 
Health effects for individuals with marked immunosuppression (e.g., 
primary or acquired severe immunodeficiency, transplant recipients, 
individuals undergoing potent cytoreductive treatments) are not 
included in this health effect scoring. While such populations are 
considered sensitive subpopulations, immunosuppressed individuals often 
have a higher standard of ongoing health care and protection required 
than the other sensitive populations under medical care. More 
importantly, nearly all pathogens have very high health effect scores 
for the markedly immunosuppressed individuals; therefore, there is 
little differentiation between pathogens based on health effects for 
the immunosuppressed subpopulation.
    This protocol scores the representative or common clinical 
presentation for the specific pathogen for the population category 
under consideration. Pathogens may produce a range of illness from 
asymptomatic infection to fulminate illness progressing rapidly to 
death. Scoring decisions are based upon the more common clinical 
presentation and clinical course for the population under 
consideration, rather than the extremes. EPA used recently published 
clinical microbiology manuals (Carroll et al., 2019; Murray et al., 
2011) as the primary data source for the common clinical presentation. 
These manuals took a broad epidemiological view of health effects 
rather than focusing on narrow research investigations or single cases.
    To obtain a representative characterization of health effects in 
all populations, EPA evaluated (separately) the general population and 
four sensitive populations (children, elderly, pregnant woman, and 
persons with chronic diseases) as to the common clinical presentation 
of illness for that population. EPA added the general population score 
to the highest score among the four sensitive subpopulations for an 
overall health effects score. The resulting score reflects that 
sensitive populations have increased risk for waterborne diseases.
d. Combining Protocol Scores To Rank Pathogens
    EPA scored and ranked the microbes on the PCCL using the three 
attribute scoring protocols for WBDOs, occurrence, and health effects. 
These protocols are designed in a hierarchical manner so that each 
pathogen is evaluated using the same criteria and that the criteria 
range for each protocol varies from high to low significance. The three 
attribute scores are then combined into a total score.
    EPA scored pathogens first using the WBDO and occurrence protocols, 
and then selected the higher score of the two scores. Selection of the 
higher score from the WBDO or occurrence protocol elevates pathogens 
that have been detected in drinking water or source water in the U.S. 
(occurrence score of 2 or 3) above pathogens that have caused WBDOs in 
other countries but not in the U.S. (WBDO score of 2).
    The CCL selection process placed more weight on pathogens causing 
recent WBDOs than on those detected in drinking water without 
documented waterborne disease from that exposure. Direct detection of 
pathogens indicates the potential for waterborne transmission of 
disease. Documented WBDOs provide an additional weight of evidence that 
illness was transmitted and that there was a waterborne route of 
exposure.
    Next, pathogens were scored using the Health Effects Protocol. The 
pathogen's score for the general population was added to the highest 
score among the four sensitive populations to produce a sum score 
between 2 and 14.
    Finally, EPA normalizes the Health Effects score and WBDO/
Occurrence score because these are of equal importance. The highest 
possible score for WBDO/Occurrence is 5 and the highest possible Health 
Effects score is 14. To equalize this imbalance, EPA

[[Page 37966]]

multiplies the health effect score by 5/14. Combining health effects 
data with the WBDO/occurrence data by adding the scores from these 
protocols provides a system that evaluates both the severity of 
potential disease and the potential magnitude of exposure through 
drinking water. Exhibit 12 presents the scores for all the 35 PCCL 
pathogens.

                                 Exhibit 12--Scores for All the PCCL 5 Pathogens
----------------------------------------------------------------------------------------------------------------
                                                                                         Normalized
                    Pathogen                       Ranking        WBDO      Occurrence     health    Total score
                                                                                           score         \1\
----------------------------------------------------------------------------------------------------------------
Naegleria fowleri..............................            1            5            3          5.0         10.0
Legionella pneumophila.........................            2            5            3          3.6          8.6
Escherichia coli (O157)........................            3            5            3          3.2          8.2
Pseudomonas aeruginosa.........................            4            5            3          3.2          8.2
Helicobacter pylori............................            5            1            3          5.0          8.0
Campylobacter jejuni...........................            6            5            3          2.5          7.5
Mycobacterium abcessus.........................            7            4            3          3.2          7.2
Shigella sonnei................................            8            4            3          3.2          7.2
Caliciviruses..................................            9            5            3          2.1          7.1
Mycobacterium avium............................           10            4            3          2.9          6.9
Adenovirus.....................................           11            2            3          3.6          6.6
Enterovirus....................................           12            2            3          3.6          6.6
Pantoea agglomerans............................           13            4            3          2.5          6.5
Hepatitis A virus..............................           14            3            2          3.2          6.2
Arcobacter butzleri............................           15            4            3          2.1          6.1
Fusarium solani................................           16            1            3          2.9          5.9
Nontuberculous Mycobacteria (NTM)..............           17            3            3          2.9          5.9
Hepatitis E virus..............................           18            2            1          3.6          5.6
Cyclospora cayetanensis........................           19            3            3          2.5          5.5
Rotavirus......................................           20            2            3          2.5          5.5
Salmonella enterica............................           21            3            3          2.5          5.5
Toxoplasma gondii..............................           22            2            1          3.2          5.2
Aspergillus fumigatus group....................           23            1            3          2.1          5.1
Entamoeba histolytica..........................           24            3            3          2.1          5.1
Exophiala jeanselmei...........................           25            1            3          2.1          5.1
Vibrio cholerae................................           26            3            3          2.1          5.1
Aeromonas hydrophila...........................           27            1            3          1.8          4.8
Plesiomonas shigelloides.......................           28            3            3          1.8          4.8
Blastocystis hominis...........................           29            4            1          0.7          4.7
Acinetobacter baumannii........................           30            1            2          2.5          4.5
Comanonas testosteroni.........................           31            1            2          2.5          4.5
Yersinia enterocolitica........................           32            3            3          1.4          4.4
Astrovirus.....................................           33            2            2          1.4          3.4
Microsporidia..................................           34            1            2          1.4          3.4
Isospora belli.................................           35            2            1          1.1          3.1
----------------------------------------------------------------------------------------------------------------
\1\ Total Score = Normalized Health Score + the higher of WBDO or Occurrence.

e. Selection of the Draft CCL Microbes
    The 35 PCCL pathogens, listed in Exhibit 12, are ranked according 
to an equal weighting of their summed scores for normalized health 
effects and the higher of the individual scores for WBDO and occurrence 
in drinking water. EPA believes this ranking indicates the most 
important pathogens to consider for the Draft CCL 5. To determine which 
of the 35 PCCL pathogens should be the highest priority for EPA's 
drinking water program and included on the Draft CCL 5, EPA considered 
scientific factors and the opportunity to advance public health 
protection. The factors included the PCCL scores for WBDO, occurrence, 
and health effects; and comments and recommendations from the various 
expert panels, including EPA's internal workgroup and CDC subject 
matter experts. The evaluation prioritizes the pathogens that provide 
the best opportunities to advance public health protection. After 
consideration of these factors, EPA has decided to include in the Draft 
CCL 5 the 12 highest ranked pathogens shown in Exhibit 12. The 
selection of microbial pathogens for the CCL 5 was similar to the 
method used for the CCL 3 and the CCL 4 with the exception that with 
the CCL 5, there were no ``natural'' break points in the ranked scores 
for the 35 pathogens.
    EPA believes that the overall rankings strongly reflect the best 
available scientific data and high quality expert input employed in the 
CCL selection process, and therefore should be important factors in 
helping to identify the top priority pathogens for the Draft CCL 5.
f. Organisms Covered by Existing Regulations
    According to Section 1412(b)(1) of the 1996 SDWA Amendments, EPA 
must select CCL contaminants that ``at the time of publication, are not 
subject to any proposed or promulgated national primary drinking water 
regulation.'' In promulgating regulations for contaminants in drinking 
water, EPA can set either a legal limit (maximum contaminant level or 
MCL) and require monitoring for the contaminant in drinking water or, 
for those contaminants that are difficult to measure, EPA can establish 
a treatment technique requirement. The Surface Water Treatment Rule (54 
FR 27486, USEPA, 1989a) established maximum contaminant level goals 
(MCLGs) of zero for Legionella, Giardia, and viruses because any amount 
of exposure to these contaminants represents some public health risk. 
Since measuring disease-causing microbes in drinking water was not 
considered to be feasible at the time of the development of the SWTR, 
EPA established treatment

[[Page 37967]]

technique requirements for these contaminants. The purpose of 
subsequent treatment technique requirements (Interim Enhanced Surface 
Water Treatment Rule (63 FR 69478, USEPA 1998a), Long Term 1 Surface 
Water Treatment Rule (67 FR 1813, USEPA, 2002a), and the Long Term 2 
Surface Water Treatment Rule (71 FR 654, USEPA, 2006a), which included 
an MCLG of zero for Cryptosporidium, is to reduce disease incidence 
associated with Cryptosporidium and other pathogenic microorganisms in 
drinking water. These rules apply to all public water systems that use 
surface water or ground water under the direct influence of surface 
water.
    The Ground Water Rule (GWR) (71 FR 65573; USEPA, 2006c) set 
treatment technique requirements to control for viruses (and pathogenic 
bacteria) because it was not feasible to monitor for viruses (or 
pathogenic bacteria) in drinking water. Under the GWR, if systems 
detect total coliforms in the distribution system, they are required to 
monitor for a fecal indicator (E. coli, coliphage, or enterococci) in 
the source water. If fecal contamination is found in the source water, 
the system must take remedial action to address contamination.
    EPA considered Legionella and specific viruses in CCL even though 
they are regulated under the Surface Water Treatment Rules (SWTR). In 
this draft document, EPA proposes to specifically list Legionella 
pneumophila, the primary pathogenic bacterium, on the Draft CCL 5 
because it has been identified in numerous WBDOs and is the most common 
cause of reported drinking water-associated outbreaks in the U.S. 
Furthermore, reported Legionnaires' disease has increased 10-fold in 
the last 20 years (CDC, 2020b). A recent National Academies of Science 
report estimated 52,000-70,000 cases of Legionnaires' disease annually, 
with 3-30% mortality (NASEM, 2020).
    EPA is also proposing to list certain viruses on the Draft CCL 5. 
Viruses include a wide range of taxa and different viral taxa have been 
implicated in various WBDOs for which EPA did not have dose response or 
treatment data when promulgating its treatment technique requirements.
    Even though there are MCLGs for Legionella and viruses, and these 
contaminants are subject to limitations as a class through the 
treatment techniques under the Surface Water Treatment Rules, there are 
no monitoring, treatment, or notification requirements within those 
NPDWRs that are specific to Legionella pneumophila or the specific 
viruses listed on CCL5 (although systems may use coliphage for source 
water monitoring for ground water systems). Therefore, EPA considers 
Legionella pneumophila and the specific viruses listed on CCL5 to be 
unregulated contaminants for purposes of eligibility for the CCL. 
Additionally, EPA received public nomination for viruses and Legionella 
for the Draft CCL 5, with Legionella pneumophila receiving the highest 
number of nominations.

C. Summary of Nominated Candidates for the Draft CCL 5

    EPA sought public nominations in a Federal Register notice on 
October 5, 2018, for unregulated chemical and microbial contaminants to 
be considered for possible inclusion in the CCL 5 (83 FR 50364, USEPA, 
2018a). In accordance with the SDWA, which directs EPA to consider 
health effects and occurrence information when deciding whether to 
place contaminants on the CCL, EPA asked that nominations include 
responses to the following questions:
    What is the contaminant's name, CAS registry number, and/or common 
synonym (if applicable)? Please do not nominate a contaminant that is 
already subject to a national primary drinking water regulation.
    What are the data that you believe support the conclusion that the 
contaminant is known or anticipated to occur in public water systems? 
For example, provide information that shows measured occurrence of the 
contaminant in drinking water or measured occurrence in sources of 
drinking water or provide information that shows the contaminant is 
released in the environment or is manufactured in large quantities and 
has a potential for contaminating sources of drinking water. Please 
provide the source of this information with complete citations for 
published information (i.e., author(s), title, journal, and date) or 
contact information for the primary investigator.
    What are the data that you believe support the conclusion that the 
contaminant may require regulation? For example, provide information 
that shows the contaminant may have an adverse health effect on the 
general population or that the contaminant is potentially harmful to 
subgroups that comprise a meaningful proportion of the population (such 
as children, pregnant women, the elderly, individuals with a history of 
serious illness, or others). Please provide the source of this 
information with complete citations for published information (i.e., 
author(s), title, journal, and date) or contact information for the 
primary investigator.
    EPA compiled and reviewed the information from the nominations 
process to identify the contaminants nominated and any sources of 
supporting data submitted that could be used to supplement the data 
gathered by EPA to inform selection of the Draft CCL 5.
    EPA received nominations for 89 unique contaminants for the CCL 5, 
including 73 chemicals and 16 microbes. Nominated contaminants included 
chemicals used in commerce, pesticides, disinfection byproducts, 
pharmaceuticals, naturally occurring elements, biological toxins, and 
waterborne pathogens. Contaminants nominated for consideration for the 
CCL 5 are shown in Exhibit 13.
    EPA received nominations from 29 different organizations and/or 
individuals. There were three general types of nominations: specific 
individual chemicals, specific individual organisms, and groups of 
contaminants (e.g., PFAS). Seven chemicals and eight microbes were 
nominated by more than one organization or individual. Legionella 
pneumophila received the most nominations, nominated by 18 
organizations or individuals. Among chemicals, perfluorononanoic acid 
(PFNA), PFOS, and PFOA received the most nominations, each nominated by 
three organizations or individuals. In addition to individual 
contaminants, groups of contaminants were nominated, such as brominated 
haloacetic acids known as ``HAA6Br,'' cyanotoxins, GenX chemicals 
(hexafluoropropylene oxide dimer acid (HFPO-DA) and its ammonium salt), 
all the PFAS approved by the EPA Method 537.1, PFAS, and the top 200 
prescribed drugs of 2016 and their parents and metabolites. A public 
commenter also proposed that all CCL 4 contaminants be retained on the 
CCL 5.
    EPA also received recommendations for the CCL process. All public 
nominations can be viewed in the EPA docket at 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).

[[Page 37968]]



     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

[[Page 37969]]

 
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
  4.2.1.1 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).
    Four publicly nominated chemicals were included on the Draft CCL 5 
as a result of evaluation team listing decisions, including 1,4-
dioxane, chlorpyrifos, manganese, and molybdenum. In addition, 43 
nominated chemicals consisting of 7 cyanotoxins, 18 DBPs, and 18 PFAS 
chemicals were included in the three chemical groups listed on the 
Draft CCL 5 (e.g., the cyanotoxin, DBP, and PFAS groups). The PFAS 
group is inclusive of any PFAS, except for PFOA and PFOS. Although PFOA 
and PFOS were nominated, EPA has made a positive final regulatory 
determination for these two chemicals; and therefore, did not include 
them in the PFAS group.
3. Listing Outcomes for the Nominated Microbial Contaminants
    All the microbes nominated for the CCL 5, with the exception of 
Salmonella enterica, and Aeromonas hydrophila, and Hepatitis A, are 
listed on the Draft CCL 5. Salmonella enterica, Aeromonas hydrophila 
and Hepatitis A did not produce sufficient composite scores to place 
them on the Draft CCL 5.

[[Page 37970]]

Although Salmonella enterica and Hepatitis A have numerous WBDOs, the 
route of exposure was not explicitly waterborne. Non-tuberculous 
Mycobacterium (NTM) and Mycobacterium (species broadly found in 
drinking water) were nominated for the CCL 5 and are not listed on the 
Draft CCL 5 as a group; instead, they were listed as Mycobacterium 
avium and Mycobacterium abscessus, two species of NTM that are found in 
drinking water.

D. Data Availability Assessment for the Draft CCL 5 Chemicals

    In an effort to provide the current data availability of the Draft 
CCL 5 contaminants with respect to occurrence, health effects, and 
analytical methods data, EPA provides a summary table (Exhibit 14) 
depicting chemicals categorized into six groups depending upon the 
availability of their occurrence data and health assessment. EPA did 
not assess data availability for individual chemicals of the 
cyanotoxins, DBPs and PFAS groups because the availability of health 
effects and occurrence data varies with individual chemicals in each 
group. The agency is addressing these groups broadly in drinking water 
based on a subset of chemicals in these groups that are known to occur 
in public water systems and may cause adverse health effects.

                                       Exhibit 14--Data Availability/Information for the Draft CCL 5 Contaminants
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                   Best available      Is a health assessment    Is an analytical method
           CASRN                      DTXSID                 Common name          occurrence data            available?                available?
--------------------------------------------------------------------------------------------------------------------------------------------------------
                     A. Contaminants with Nationally Representative Finished Water Occurrence Data and Qualifying Health Assessments
--------------------------------------------------------------------------------------------------------------------------------------------------------
96-18-4...................  DTXSID9021390               1,2,3-                 National Finished      Yes.....................  Yes.
                                                         Trichloropropane.      Water.
123-91-1..................  DTXSID4020533               1,4-dioxane..........  National Finished      Yes.....................  Yes.
                                                                                Water.
319-84-6..................  DTXSID2020684               alpha-                 National Finished      Yes.....................  Yes.
                                                         Hexachlorocyclohexan   Water.
                                                         e.
7440-42-8.................  DTXSID3023922               Boron................  National Finished      Yes.....................  Yes.
                                                                                Water.
63-25-2...................  DTXSID9020247               Carbaryl.............  National Finished      Yes.....................  Yes.
                                                                                Water.
2921-88-2.................  DTXSID4020458               Chlorpyrifos.........  National Finished      Yes.....................  Yes.
                                                                                Water.
7440-48-4.................  DTXSID1031040               Cobalt...............  National Finished      Yes.....................  Yes.
                                                                                Water.
60-57-1...................  DTXSID9020453               Dieldrin.............  National Finished      Yes.....................  Yes.
                                                                                Water.
330-54-2..................  DTXSID0020446               Diuron...............  National Finished      Yes.....................  Yes.
                                                                                Water.
13194-84-4................  DTXSID4032611               Ethoprop.............  National Finished      Yes.....................  Yes.
                                                                                Water.
7439-93-2.................  DTXSID5036761               Lithium..............  National Finished      Yes.....................  Yes.
                                                                                Water.
7439-96-5.................  DTXSID2024169               Manganese............  National Finished      Yes.....................  Yes.
                                                                                Water.
7439-98-7.................  DTXSID1024207               Molybdenum...........  National Finished      Yes.....................  Yes.
                                                                                Water.
42874-03-3................  DTXSID7024241               Oxyfluorfen..........  National Finished      Yes.....................  Yes.
                                                                                Water.
52645-53-1................  DTXSID8022292               Permethrin...........  National Finished      Yes.....................  Yes.
                                                                                Water.
41198-08-7................  DTXSID3032464               Profenofos...........  National Finished      Yes.....................  Yes.
                                                                                Water.
1918-16-7.................  DTXSID4024274               Propachlor...........  National Finished      Yes.....................  Yes.
                                                                                Water.
91-22-5...................  DTXSID1021798               Quinoline............  National Finished      Yes.....................  Yes.
                                                                                Water.
107534-96-3...............  DTXSID9032113               Tebuconazole.........  National Finished      Yes.....................  Yes.
                                                                                Water.
78-48-8...................  DTXSID1024174               Tribufos.............  National Finished      Yes.....................  Yes.
                                                                                Water.
7440-62-2.................  DTXSID2040282               Vanadium.............  National Finished      Yes.....................  Yes.
                                                                                Water.
95-53-4...................  DTXSID1026164               2-Aminotoluene.......  National Finished      Yes.....................  Yes.
                                                                                Water.
51-28-5...................  DTXSID0020523               2,4-Dinitrophenol....  National Finished      Yes.....................  Yes.
                                                                                Water.
--------------------------------------------------------------------------------------------------------------------------------------------------------
                   B. Contaminants with Non-Nationally Representative Finished Water Occurrence Data and Qualifying Health Assessments
--------------------------------------------------------------------------------------------------------------------------------------------------------
2163-68-0.................  DTXSID6037807               2-Hydroxyatrazine....  Non-National Finished  Yes.....................  No.
                                                                                Water.
120068-37-3...............  DTXSID4034609               Fipronil.............  Non-National Finished  Yes.....................  No.
                                                                                Water.
121-74-5..................  DTXSID4020791               Malathion............  Non-National Finished  Yes.....................  Yes.
                                                                                Water.
36734-19-7................  DTXSID3024154               Iprodione............  Non-National Finished  Yes.....................  No.
                                                                                Water.
298-02-2..................  DTXSID4032459               Phorate..............  Non-National Finished  Yes.....................  Yes.
                                                                                Water.
27314-13..................  DTXSID8024234               Norflurazon..........  Non-National Finished  Yes.....................  Yes.
                                                                                Water.
2303-17-5.................  DTXSID5024344               Tri-allate...........  Non-National Finished  Yes.....................  No.
                                                                                Water.
139-40-2..................  DTXSID3021196               Propazine............  Non-National Finished  Yes.....................  Yes.
                                                                                Water.
1689-84-5.................  DTXSID3022162               Bromoxynil...........  Non-National Finished  Yes.....................  No.
                                                                                Water.
2312-35-8.................  DTXSID4024276               Propargite...........  Non-National Finished  Yes.....................  No.
                                                                                Water.
141-66-2..................  DTXSID9023914               Dicrotophos..........  Non-National Finished  Yes.....................  Yes.
                                                                                Water.
709-98-8..................  DTXSID8022111               Propanil.............  Non-National Finished  Yes.....................  Yes.
                                                                                Water.
153719-23-4...............  DTXSID2034962               Thiamethoxam.........  Non-National Finished  Yes.....................  No.
                                                                                Water.
10605-21-7................  DTXSID4024729               Carbendazim (MBC)....  Non-National Finished  Yes.....................  No.
                                                                                Water.
55283-68..................  DTXSID8032386               Ethalfluralin........  Non-National Finished  Yes.....................  No.
                                                                                Water.
3397624...................  DTXSID1037806               Diaminochlorotriazine  Non-National Finished  Yes.....................  No.
                                                         (DACT).                Water.
96182535..................  DTXSID1032482               Tebupirimfos.........  Non-National Finished  Yes.....................  Yes.
                                                                                Water.
114261....................  DTXSID7021948               Propoxur.............  Non-National Finished  Yes.....................  Yes.
                                                                                Water.
732116....................  DTXSID5024261               Phosmet..............  Non-National Finished  Yes.....................  Yes.
                                                                                Water.
2164-17-2.................  DTXSID8020628               Fluometuron..........  Non-National Finished  Yes.....................  Yes.
                                                                                Water.
--------------------------------------------------------------------------------------------------------------------------------------------------------
                   C. Contaminant with Nationally Representative Finished Water Occurrence Data Lacking Qualifying Health Assessments
--------------------------------------------------------------------------------------------------------------------------------------------------------
1634-04-4.................  DTXSID3020833               Methyl tert-butyl      National Finished      No......................  Yes.
                                                         ether (MTBE).          Water.
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                D. Contaminants with Qualifying Health Assessments Lacking Finished Water Occurrence Data
--------------------------------------------------------------------------------------------------------------------------------------------------------
3397-62-4.................  DTXSID1037806               6-Chloro-1,3,5-        National Ambient       Yes.....................  Yes.
                                                         triazine-2,4-diamine.  Water.
30560-19-1................  DTXSID8023846               Acephate.............  National Ambient       Yes.....................  Yes.
                                                                                Water.
84-65-1...................  DTXSID3020095               Anthraquinone........  National Ambient       Yes.....................  No.
                                                                                Water.
6190-65-4.................  DTXSID5037494               Deethylatrazine......  National Ambient       Yes.....................  No.
                                                                                Water.
3397-62-4.................  DTXSID0037495               Desisopropyl atrazine  National Ambient       Yes.....................  Yes.
                                                                                Water.
333-41-5..................  DTXSID9020407               Diazinon.............  National Ambient       Yes.....................  Yes.
                                                                                Water.
60-51-5...................  DTXSID7020479               Dimethoate...........  National Ambient       Yes.....................  Yes.
                                                                                Water.

[[Page 37971]]

 
142459-58-3...............  DTXSID2032552               Flufenacet             National Ambient       Yes.....................  No.
                                                         (Thiaflumide).         Water.
22967-92-6................  DTXSID9024198               Methylmercury........  National Ambient       Yes.....................  No.
                                                                                Water.
13071-79-9................  DTXSID2022254               Terbufos.............  National Ambient       Yes.....................  Yes.
                                                                                Water.
126-73-8..................  DTXSID3021986               Tributyl phosphate     National Ambient       Yes.....................  No.
                                                         (TNBP).                Water.
103476-24-0...............  DTXSID5021411               Tris(2-chloroethyl)    National Ambient       Yes.....................  No.
                                                         phosphate (TCEP).      Water.
7440-33-7.................  DTXSID8052481               Tungsten.............  National Ambient       Yes.....................  No.
                                                                                Water.
107-02-8..................  DTXSID5020023               Acrolein.............  National Ambient       Yes.....................  Yes.
                                                                                Water.
95-63-6...................  DTXSID6021402               Trimethylbenzene       National Ambient       Yes.....................  Yes.
                                                         (1,2,4-).              Water.
80-05-7...................  DTXSID7020182               Bisphenol A..........  National Ambient       Yes.....................  No.
                                                                                Water.
143-50-0..................  DTXSID1020770               Chlordecone            Non-national Ambient   Yes.....................  Yes.
                                                         (Kepone)\2\.           Water.
741-58-2..................  DTXSID9032329               Bensulide............  Non-national Ambient   Yes.....................  Yes.
                                                                                Water.
16752-77-5................  DTXSID1022267               Methomyl.............  Non-National Finished  Yes.....................  Yes.
                                                                                Water.
--------------------------------------------------------------------------------------------------------------------------------------------------------
                   E. Contaminants Lacking Nationally Representative Finished Water Occurrence Data and Qualifying Health Assessments
--------------------------------------------------------------------------------------------------------------------------------------------------------
104-40-5..................  DTXSID3021857               4-Nonylphenol (all     Non-National Finished  No......................  Method in review.
                                                         isomers).              Water.
86386-73-4................  DTXSID3020627               Fluconazole..........  Non-National Finished  No......................  No.
                                                                                Water.
93413628..................  DTXSID40869118              Desvenlafaxine.......  Non-National Finished  No......................  No.
                                                                                Water.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Key to Exhibit
National = Occurrence data that are nationally representative are available
Non-National = Occurrence data that are not nationally representative are available
Note: Data availability was not assessed for cyanotoxins, DBPs and PFAS.

    Contaminants in Group A have nationally representative finished 
drinking water occurrence data and qualifying health assessments. 
Contaminants in Group B have finished drinking water occurrence data 
that is not nationally representative and qualifying health 
assessments. Contaminants in groups C, D, and E lack either a 
qualifying health assessment or finished water occurrence data and have 
more substantial data needs.
    In addition, EPA assessed the data availability of the PCCL 5 
chemicals that are not included on the Draft CCL 5. For more 
information on EPA methodology to identify data availability and 
summary tables, see Section 5.3 of the Chemical Technical Support 
Document (USEPA, 2021c).

IV. Request for Comments

    The purpose of this document is to present the Draft CCL 5. EPA 
seeks comments on the following:
    A. Contaminants selected for the Draft CCL 5, including any 
supporting data that can be used in developing the Final CCL 5.
    B. Data that EPA obtained and evaluated for developing the Draft 
CCL 5 may be found in the Chemical Technical Support Document and 
Microbial Technical Support Document located in the docket for this 
document.
    C. The improvements EPA implemented in the CCL 5 process.
    EPA will take these comments into consideration when developing 
future CCLs. EPA will consider all information and comments received in 
determining the Final CCL 5, in the development of future CCLs, and in 
the agency's efforts to set drinking water priorities in the future.

V. EPA's Next Steps

    Between now and the publication of the Final CCL 5, EPA will 
evaluate comments received during the public comment period for this 
document, consult with EPA's Science Advisory Board, and prepare the 
Final CCL 5 considering this input.

VI. References

American Association for the Advancement of Science (AAAS). 2020. 
Per- and Polyfluoroalkyl Substances (PFAS) in Drinking Water. 
Available on the internet at: https://www.aaas.org/programs/epi-center/pfas.
Carroll, K.C., Pfaller, M.A., Landry, M.L., McAdam, A.J., Patel, R., 
Richter, S.S. and Warnock, David W. (ed). 2019. Manual of Clinical 
Microbiology, Twelfth Edition.
CDC. 2008. Surveillance for Waterborne Disease and Outbreaks 
Associated with Drinking Water and Water not Intended for Drinking--
United States, 2005-2006. MMWR 57 (SS-9).
CDC, 2020a. National Outbreak Reporting System (NORS)--United 
States, 2009-2017.
CDC, 2020b. Legionella (Legionnaires' Disease and Pontiac Fever). 
https://cdc.gov/legionella/about/history.html.
Executive Office of the President. 2021. Protecting Public Health 
and the Environment and Restoring Science To Tackle the Climate 
Crisis; Federal Register. Vol. 86, E.O. 13990. p. 7037, January 20, 
2021.
Murray, P.R., E.J. Baron, J.H. Jorgensen, M.L. Landry, and M.A. 
Pfaller (ed.). 2011. Manual of Clinical Microbiology, 10th Edition, 
ASM Press, Washington, DC.
National Academies of Sciences, Engineering, and Medicine (NASEM). 
2020. Management of Legionella in Water Systems. The National 
Academies Press, Washington, DC.
National Drinking Water Advisory Council (NDWAC). 2004. National 
Drinking Water Advisory Council Report on the CCL Classification 
Process to the U.S. Environmental Protection Agency. Available on 
the internet at: https://www.epa.gov/sites/production/files/2015-11/documents/report_ccl_ndwac_07-06-04.pdf.
National Research Council (NRC). 2001. Classifying Drinking Water 
Contaminants for Regulatory Consideration. National Academy Press, 
Washington, DC.
USEPA. 1998. Announcement of the Drinking Water Contaminant 
Candidate List; Notice. Federal Register. Vol. 63, No. 40. p. 10274, 
March 2, 1998.
USEPA. 1999. Revisions to the Unregulated Contaminant Monitoring 
Regulation for Public Water Systems. Federal Register. Vol. 64, No. 
180, p. 50556, September 17, 1999.
USEPA. 2000. Methodology for Deriving Ambient Water Quality Criteria 
for the Protection of Human Health (2000). https://www.epa.gov/sites/production/files/2018-10/documents/methodology-wqc-protection-hh-2000.pdf.
USEPA. 2003. Announcement of Regulatory Determinations for Priority 
Contaminants on the Drinking Water Contaminant Candidate List. 
Federal Register. Vol. 68, No. 138. p. 42898, July 18, 2003.
USEPA. 2005. Drinking Water Contaminant Candidate List 2; Final 
Notice. Federal Register. Vol. 70, No. 36. p. 9071, February 24, 
2005.
USEPA. 2007. Unregulated Contaminant Monitoring Regulation (UCMR) 
for Public Water Systems Revisions; Correction. Federal Register. 
Vol. 72, No. 19, p. 4328, January 30, 2007.

[[Page 37972]]

USEPA. 2008. Drinking Water: Regulatory Determinations Regarding 
Contaminants on the Second Drinking Water Contaminant Candidate 
List. Federal Register. Vol. 73, No. 174. p. 44251, July 30, 2008.
USEPA. 2009a. Final Contaminant Candidate List 3 Chemicals: 
Identifying the Universe. EPA 815-R09-006. August 2009.
USEPA. 2009b. Final Contaminant Candidate List 3 Chemicals: 
Screening to a PCCL. EPA. 815-R09-007. August 2009.
USEPA. 2009c. Community Water System Survey 2006. Volume 1: 
Overview. EPA 815-R-09-001. February 2009.
USEPA. 2009d. Community Water System Survey 2006. Volume II: 
Detailed Tables and Survey Methodology. EPA 815-R-09-002. May 2009.
USEPA. 2009e. Drinking Water Contaminant Candidate List 3--Final. 
Federal Register. Vol. 74, No. 194. p. 51850, October 8, 2009.
USEPA. 2011. Drinking Water: Regulatory Determination on 
Perchlorate. Federal Register. Vol. 76, No. 29. p. 7762, February 
11, 2011.
USEPA. 2012a. Revisions to the Unregulated Contaminant Monitoring 
Regulation (UCMR 3) for Public Water Systems. Federal Register. Vol. 
77, No. 85. p. 26071, May 2, 2012.
USEPA. 2012b. TSCA Work Plan Chemicals: Methods Document. February 
2012. Available on the internet at: https://www.epa.gov/sites/production/files/2014-03/documents/work_plan_methods_document_web_final.pdf.
USEPA. 2014. Announcement of Preliminary Regulatory Determination 
for Contaminants on the Third Drinking Water Contaminant Candidate 
List. Federal Register. Vol. 79, No. 202, p. 62716, October 20, 
2014.
USEPA. 2015. Algal Toxin Risk Assessment and Management Strategic 
Plan for Drinking Water, Strategy Submitted to Congress to Meet the 
Requirements of P.L. 114-45. EPA 810-R-04-003.
USEPA. 2016a. Revisions to the Unregulated Contaminant Monitoring 
Regulation (UCMR 4) for Public Water Systems. Federal Register. Vol. 
81, No. 244. p. 92666, December 20, 2016.
USEPA. 2016b. Final Regulatory Determinations on the Third Drinking 
Water Contaminant Candidate List. Federal Register. Vol. 81, No. 1. 
P. 13-19, January 4, 2016.
USEPA. 2016c. Drinking Water Contaminant Candidate List 4-Final. 
Federal Register. Vol. 81, No. 222. P. 81099, November 17, 2016.
USEPA. 2017. Analysis of Occurrence Data from the Third Six-Year 
Review of Existing National Primary Drinking Water Regulations: 
Chemical Phase Rules and Radionuclides Rules. EPA-810-R-16-014. 
December 2016.
USEPA. 2018a. Request for Nominations of Drinking Water Contaminants 
for the Fifth Contaminant Candidate List. Notice. Federal Register. 
Vol. 83, No. 194. p. 50364, October 5, 2018.
USEPA. 2018b. Basic Information on PFAS. Available at: https://www.epa.gov/pfas/basic-information-pfas.
USEPA. 2019a. Drinking Water: Final Action on Perchlorate. Federal 
Register. Vol. 84, No. 123, p. 30524. June 26, 2019.
USEPA. 2019b. EPA's Per- and Polyfluoroalkyl Substances (PFAS) 
Action Plan. EPA 823-R-18-004, February 2019. Available at: https://www.epa.gov/sites/production/files/2019-02/documents/pfas_action_plan_021319_508compliant_1.pdf.
USEPA. 2020. Drinking Water: Perchlorate. Federal Register. Vol. 85, 
No. 140, p. 43990, July 2020. EPA-HQ-OW-2018-0780-0302.
USEPA. 2021a. Revisions to the Unregulated Contaminant Monitoring 
Regulation (UCMR 5) for Public Water Systems. Federal Register. Vol. 
86, No. 46. p. 13846, March 11, 2021.
USEPA. 2021b. Announcement of Final Regulatory Determinations for 
Contaminants on the Fourth Drinking Water Contaminant Candidate 
List. Federal Register. Vol. 86, No. 40, p. 12272, March 3, 2021. 
EPA-HQ-OW-2019-0583.
USEPA. 2021c. Technical Support Document for the Draft Fifth 
Contaminant Candidate List (CCL 5)--Chemical Contaminants. EPA 815-
R-21-005, July 2021.
USEPA. 2021d. Technical Support Document for the Draft Fifth 
Contaminant Candidate List (CCL 5)--Microbial Contaminants. EPA 815-
R-21-007, July 2021.
USEPA. 2021e. Technical Support Document for the Draft Fifth 
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EPA 815-R-21-006, July 2021.
USEPA. 2021f. TSCA Section 8(a)(7) Reporting and Recordkeeping 
Requirements for Perfluoroalkyl and Polyfluoroalkyl Substances. 
Proposed Rule. 86 FR 33926. June 28, 2021.
Williams, A.J., C.M. Grulke, J. Edwards, A.D. McEachran, K. 
Mansouri, N.C. Baker, G. Patlewicz, I. Shah, J.F. Wambaugh, R.S. 
Judson, and A.M. Richard. 2017. The CompTox Chemistry Dashboard: a 
community data resource for environmental chemistry. Journal of 
Cheminformatics. 9:61. doi:10.1186/s13321-017-0247-6.

Radhika Fox,
Assistant Administrator, Office of Water.
[FR Doc. 2021-15121 Filed 7-16-21; 8:45 am]
BILLING CODE 6560-50-P


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