Document ID: EPA-HQ-OW-2018-0594-0106
Agency: epa
Document Type: Rule
Title: Drinking Water Contaminant Candidate List 5-Final
Posted Date: 2022-11-14T05:00Z

[Federal Register Volume 87, Number 218 (Monday, November 14, 2022)]
[Rules and Regulations]
[Pages 68060-68085]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-23963]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 141

[EPA-HQ-OW-2018-0594; FRL-7251-02-OW]

Drinking Water Contaminant Candidate List 5--Final

AGENCY: Environmental Protection Agency (EPA).

ACTION: Availability of list.

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SUMMARY: The U.S. Environmental Protection Agency (EPA) is issuing the 
Contaminant Candidate List (CCL) which is a list of contaminants in 
drinking water that are currently not subject to any proposed or 
promulgated national primary drinking water regulations. In addition, 
these contaminants are known or anticipated to occur in public water 
systems and may require regulation under the Safe Drinking Water Act 
(SDWA). This list is the Fifth Contaminant Candidate List (CCL 5) 
published by the agency since the SDWA amendments of 1996. CCL 5 
includes 66 chemicals, 3 chemical groups (cyanotoxins, disinfection 
byproducts (DBPs), and per- and polyfluoroalkyl substances (PFAS)), and 
12 microbial contaminants.

DATES: November 14, 2022.

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 [email protected]. 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 
[email protected].
    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. How can I get copies of this document and other related 
information?
    1. Docket
    2. Electronic Access
    C. What is the purpose of this action?
    D. Background and Statutory Requirements for CCL, Regulatory 
Determination and Unregulated Contaminant Monitoring Rule
    1. Contaminant Candidate List
    2. Regulatory Determination
    3. Unregulated Contaminant Monitoring Rule
    E. Interrelationship Between CCL, Regulatory Determination, and 
Unregulated Contaminant Monitoring Rule
    F. Summary of Previous CCLs and Regulatory Determinations
    1. The First Contaminant Candidate List
    2. The Regulatory Determinations for CCL 1 Contaminants
    3. The Second Contaminant Candidate List
    4. The Regulatory Determinations for CCL 2 Contaminants
    5. The Third Contaminant Candidate List
    6. The Regulatory Determinations for CCL 3 Contaminants
    7. The Fourth Contaminant Candidate List
    8. The Regulatory Determinations for CCL 4 Contaminants
II. What is on EPA's drinking water Contaminant Candidate List 5?
    A. Chemical Contaminants
    B. Microbial Contaminants
III. Summary of the Approach Used To Identify and Select Candidates 
for the CCL 5
    A. Overview of the Three-Step Development Process
    1. Chemical Contaminants
    2. Microbial Contaminants
    B. Summary of Nominated Candidates for the CCL 5
    1. Chemical Nominations and Listing Outcomes
    2. Microbial Nominations and Listing Outcomes
    C. Chemical Groups on the CCL 5
IV. What comments did EPA receive on the Draft CCL 5 and how did the 
Agency respond?
    A. Public Comments
    1. General Comments
    2. Chemical Process and Chemical Contaminants
    a. Chemical Data/Data Sources
    b. Chemical Groups
    i. Cyanotoxins
    ii. DBPs
    iii. PFAS
    c. Individual Chemical Contaminants
    3. The Microbial Process and Microbial Contaminants
    a. Comments on Individual Microbial Contaminants
    4. Contaminants Not on CCL 5
    5. Suggestions To Improve Future CCLs
    B. Recommendations From the EPA Science Advisory Board
    1. Overall SAB Recommendations
    2. Recommendations for Future CCLs
    3. EPA's Overall Response to SAB Recommendations
V. Data Availability for CCL 5 Contaminants
VI. Next Steps and Future Contaminant Candidate Lists
VII. References

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I. General Information

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

    The Contaminant Candidate List 5 (CCL 5) does not impose any 
requirements on regulated entities.

B. How can I get copies of this document and other related information?

    1. Docket. EPA has established a docket for this action under 
Docket ID No. EPA-HQ-OW-2018-0594. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available electronically 
through www.regulations.gov or in hard copy at the 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). For further 
information on the EPA Docket Center services and the current status, 
see: https://www.epa.gov/dockets.
    2. Electronic Access. You may access this Federal Register document 
electronically from https://www.federalregister.gov/documents/current.

C. What is the purpose of this action?

    The Safe Drinking Water Act (SDWA), as amended in 1996, requires 
EPA to publish a list every five years of currently unregulated 
contaminants that may pose risks for drinking water (referred to as the 
Contaminant Candidate List, or CCL). This list is subsequently used to 
make regulatory determinations on whether or not to regulate at least 
five contaminants from the CCL with national primary drinking water 
regulations (NPDWRs) ((SDWA section 1412(b)(1)). The purpose of this 
action is to publish the CCL 5, a summary of the major comments 
received on the draft CCL 5, and a summary of EPA's responses to those 
comments. Today's action only addresses the CCL 5. The Regulatory 
Determination (RD) process for contaminants on the CCL is a separate 
agency action.

D. Background and Statutory Requirements for CCL, Regulatory 
Determination and Unregulated Contaminant Monitoring Rule

1. Contaminant Candidate List
    SDWA section 1412(b)(1)(B)(i), as amended in 1996, requires EPA to 
publish the CCL every five years. The SDWA specifies that the list must 
include contaminants that are not subject to any proposed or 
promulgated NPDWRs, are known or anticipated to occur in public water 
systems (PWSs), and may require regulation under the SDWA. The 
unregulated contaminants considered for listing shall include, but not 
be limited to, hazardous substances identified in section 101(14) of 
the Comprehensive Environmental Response, Compensation, and Liability 
Act (CERCLA) of 1980, and substances registered as pesticides under the 
Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). The 
statute requires EPA to consult with the scientific community, 
including the Science Advisory Board (SAB) and to provide notice and 
opportunity for public comment. 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 (USEPA, 2021a).
2. Regulatory Determination
    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 (with a possible extension of 9 months).
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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 issue a new list of no more 
than 30 unregulated contaminants to be monitored in drinking water by 
PWSs. This is known as the Unregulated Contaminant Monitoring Rule 
(UCMR). Monitoring is required by all PWSs serving more than 10,000 
persons. The America's Water Infrastructure Act of 2018 expanded the 
requirements of the UCMR 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 
and non-regulatory public health protection actions for emerging 
contaminants in drinking water. EPA has issued five UCMRs; UCMR 1 was 
published on September 17, 1999 (64 FR 50556, USEPA, 1999), UCMR 2 was 
published on January 4, 2007 (72 FR 368, USEPA, 2007), UCMR 3 was 
published on May 2, 2012 (77 FR 26072, USEPA, 2012), UCMR 4 was 
published on December 20, 2016 (81 FR 92666, USEPA, 2016a), and UCMR 5 
on December 27, 2021 (86 FR 73131, USEPA, 2021b). UCMR 5 requires 
monitoring for 30 chemical

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contaminants between 2023 and 2025 using analytical methods developed 
by EPA or consensus organizations. Consistent with EPA's PFAS Strategic 
Roadmap (USEPA, 2021c), UCMR 5 will provide new data to improve the 
agency's understanding of the concentrations and the frequencies that 
29 per- and polyfluoroalkyl substances (PFAS) and lithium occur in the 
nation's PWS; PFAS (as a group) and lithium are included on CCL 5.

E. Interrelationship Between CCL, Regulatory Determination, and 
Unregulated Contaminant Monitoring Rule

    The CCL is the first step in the SDWA regulatory framework for 
screening and evaluating a subset of contaminants that may require 
future regulation. The CCL serves as the initial screening of potential 
contaminants for consideration under EPA's Regulatory Determination 
(RD) process. However, inclusion on the CCL does not mean that any 
particular contaminant will necessarily be regulated in the future. A 
decision to exclude a contaminant from a CCL may be reconsidered during 
future CCL cycles and that contaminant could potentially be listed if 
new information indicates that the contaminant meets the SDWA 
requirements for listing.
    The UCMR provides a mechanism to obtain nationally representative 
occurrence data for contaminants in drinking water. Traditionally, 
unregulated contaminants chosen by EPA for monitoring have been 
selected from the most current 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 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 
Regulatory Determination or UCMR.

F. Summary of Previous CCLs and Regulatory Determinations

1. The First Contaminant Candidate List
    The First Contaminant Candidate List (CCL 1) was published on March 
2, 1998 (63 FR 10274, USEPA, 1998). The CCL 1 was developed based on 
recommendations by the National Drinking Water Advisory Council (NDWAC) 
and reviewed by technical experts. It contained 50 chemicals and 10 
microbial contaminants/groups.
2. The Regulatory Determinations for CCL 1 Contaminants
    EPA published its final regulatory determinations for a subset of 
contaminants listed on the CCL 1 on July 18, 2003 (68 FR 42898, USEPA, 
2003). EPA identified 9 contaminants from the 60 contaminants listed on 
the CCL 1 that had sufficient data and information available to make 
regulatory determinations. The nine contaminants were Acanthamoeba, 
aldrin, dieldrin, hexachlorobutadiene, manganese, metribuzin, 
naphthalene, sodium, and sulfate. EPA determined that no regulatory 
action was appropriate or necessary for any of the nine contaminants at 
that time. EPA subsequently issued guidance on Acanthamoeba and Health 
Advisories for manganese, sodium, and sulfate.
3. The Second Contaminant Candidate List
    EPA published the Second Contaminant Candidate List (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 Third Contaminant Candidate List (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
    EPA published a positive 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 February 11, 
2011 (76 FR 7762, USEPA, 2011). EPA published final determinations not 
to regulate four additional CCL 3 contaminants--dimethoate, 1,3-
dinitrobenzene, terbufos and terbufos sulfone on January 4, 2016 (81 FR 
13, USEPA, 2016b). EPA published a proposed rulemaking for perchlorate 
on June 26, 2019 (85 FR 43990, USEPA, 2019a), and sought public input 
on regulatory alternatives for perchlorate, including withdrawal of the 
previous positive regulatory determination. Based on the evaluation of 
public comments, and review of the updated scientific data, EPA 
withdrew the 2011 positive regulatory determination and made a final 
determination not to regulate perchlorate on July 21, 2020 (85 FR 
43990, USEPA, 2020). EPA has since completed a review for the final 
determination for perchlorate in accordance with President Biden's 
Executive Order 13990 ``Protecting Public Health and the Environment 
and Restoring Science to Tackle the Climate Crisis'' (86 FR 7037, 
Executive Office of the President, 2021). On March 21, 2022, the agency 
concluded that the 2020 decision not to regulate

[[Page 68063]]

perchlorate is supported by the best available peer reviewed science. 
Additionally, EPA announced multiple integrated actions to ensure that 
public health is protected from perchlorate in drinking water.
7. The Fourth Contaminant Candidate List
    EPA published the Fourth Candidate List (CCL 4) on November 17, 
2016 (81 FR 81099, USEPA, 2016c). CCL 4 contained 97 chemicals or 
chemical groups and 12 microbial contaminants. All contaminants listed 
on 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.
8. The Regulatory Determinations for CCL 4 Contaminants
    EPA published final regulatory determinations for eight CCL 4 
contaminants on March 3, 2021 (86 FR 12272, USEPA, 2021d). EPA made 
final determinations to regulate perfluorooctanesulfonic acid (PFOS) 
and perfluorooctanoic acid (PFOA) in drinking water and to not regulate 
the six contaminants 1,1-dichloroethane, acetochlor, methyl bromide 
(bromomethane), metolachlor, nitrobenzene, and 1,3,5-Trinitro-1,3,5-
triazinane (RDX).

II. What is on EPA's drinking water Contaminant Candidate List 5?

    CCL 5 includes 81 contaminants or contaminant groups (Exhibits 1a, 
1b, and 1c). The list is comprised of 69 chemicals or chemical groups 
which include 66 chemicals, one group of cyanotoxins, one group of 
disinfection byproducts (DBPs), and one group of PFAS chemicals. The 
list also includes 12 microbes; specifically eight bacteria, three 
viruses, and one protozoa.

A. Chemical Contaminants

BILLING CODE 6560-50-P
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B. Microbial Contaminants

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III. Summary of the Approach Used To Identify and Select Candidates for 
the CCL 5

A. Overview of the Three-Step Development Process

    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 public and the 
SAB. Therefore, in developing the 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 2 illustrates a generalized 3-step process EPA applied to 
both chemical and microbial contaminants for the CCL 5. The agency 
began with a large Universe of contaminants, screened it down to a 
Preliminary CCL 5 (PCCL 5), selected the Draft CCL 5, then published 
for public comment. The specific execution of particular steps differed 
in detail for the chemical and microbial contaminants. Each step of the 
CCL 5 process and associated number of chemical and microbial 
contaminants are described in the remainder of Section III of this 
document.

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[GRAPHIC] [TIFF OMITTED] TR14NO22.020

1. Chemical Contaminants
    EPA followed the three-step process illustrated in Exhibit 2 to 
identify chemicals for inclusion on the 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. Classification of PCCL 5 chemicals to select the 
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 CCL 5.
    A detailed description of the processes used to develop the CCL 5 
of chemicals using these steps can be found in the Technical Support 
Document for the Final Fifth Contaminant Candidate List (CCL 5)--
Chemical Contaminants (USEPA, 2022a), referred to hereafter as the 
Final CCL 5 Chemical Technical Support Document.
2. Microbial Contaminants
    EPA also followed the three-step process illustrated in Exhibit 2 
to identify microbes for inclusion on the 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 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 a CCL 4 
SAB recommendation. EPA re-examined all 12 microbial exclusionary 
screening criteria used in previous CCLs and modified one criterion for 
the CCL 5. A detailed description of these steps used to select 
microbes for the CCL 5 can be found in the Technical Support Document 
for the Final Fifth Candidate List (CCL 5)--Microbial Contaminants 
(USEPA, 2022b), referred to hereafter as the Final CCL 5 Microbial 
Technical Support Document.

B. Summary of Nominated Candidates for the CCL 5

    EPA sought public nominations in a Federal Register notice (FRN) 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). EPA received nominations for 89 unique contaminants from 29 
different organizations and/or individuals for the CCL 5, including 73 
chemicals and 16 microbes. EPA compiled and reviewed the information 
from the nominations process to identify the nominated contaminants and 
any sources of supporting data submitted that could be used to 
supplement the data gathered by EPA to inform selection of the CCL 5. 
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 Exhibits 3a and 3b. 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

[[Page 68069]]

detailed summary of the nomination process is included in Section 3.6 
of the Final CCL 5 Chemical Technical Support Document (USEPA, 2022a) 
and in Section 2.1 of the Final CCL 5 Microbial Technical Support 
Document (USEPA, 2022b).
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[GRAPHIC] [TIFF OMITTED] TR14NO22.024

BILLING CODE 6560-50-C
1. Chemical Nominations and Listing Outcomes
    EPA reviewed the 73 publicly nominated chemical contaminants and 
included 47 out of the 73 on the CCL 5. Four publicly nominated 
chemicals were included on the 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 CCL 5 (i.e., the cyanotoxin, DBP, and 
PFAS groups).
    To evaluate the chemical nominations, EPA first compared the 
publicly nominated chemical contaminants with the top 250th scored 
chemicals and identified 19 chemicals which were already included in 
the top 250 chemicals of the scored CCL 5 Chemical Universe and not 
subject to proposed or promulgated NPDWRs. If a nominated chemical was 
part of the top 250 chemicals, then EPA had already identified and 
extracted health effects and occurrence data on this chemical from 
primary data sources in Step 1, Building the Chemical Universe. Some 
nominated chemicals were not included in the CCL 5 Chemical Universe; 
they would require further data collection to be evaluated for listing 
on the CCL 5. To identify additional data for these nominated 
chemicals, EPA assessed data sources cited with public nominations 
using the CCL-specific assessment factors (described in Section 2.2 of 
the Final CCL 5 Chemical Technical Support Document (USEPA, 2022a)) 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. EPA also conducted 
literature searches to identify additional health effects and 
occurrence data; more information on the literature searches can be 
found in Section 4.2 of the Final CCL 5 Chemical Technical Support 
Document (USEPA, 2022a).
    EPA could not identify occurrence data for 13 nominated chemicals 
(noted in Exhibit 3a) 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 EPA 
should not advance these chemicals further in the CCL 5 process. 
However, four of these nominated chemicals were evaluated for possible 
research needs (see Chapter 5 of the Final CCL 5 Chemical Technical 
Support Document; USEPA, 2022a). More detailed information about how 
nominated chemicals were considered for CCL 5 can be found in Section 
3.6 of the Final CCL 5 Chemical Technical Support Document (USEPA, 
2022a).

[[Page 68073]]

2. Microbial Nominations and Listing Outcomes
    EPA reviewed the nominated microbial contaminants to determine if 
the microorganisms nominated were already included as a part of the CCL 
5 Microbial Universe. EPA also collected additional data, when 
available, for the nominated microbial contaminants from data sources 
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 developed for the CCL 3. A more detailed description 
of the data sources used to evaluate microbial contaminants for the CCL 
5 can be found in the Final CCL 5 Microbial Technical Support Document 
(USEPA, 2022b).
    All microbes nominated for the CCL 5, except for Salmonella 
enterica, Aeromonas hydrophila, Hepatitis A, and Non-tuberculous 
Mycobacterium (NTM) as a group are listed on the CCL 5. Salmonella 
enterica, Aeromonas hydrophila and Hepatitis A did not produce 
sufficient composite scores to place them on the CCL 5. Although 
Salmonella enterica and Hepatitis A have numerous outbreaks reported in 
Centers of Disease Control (CDC) National Outbreak Reporting System 
(NORS), the route of exposure was not reported as waterborne in NORS. 
Non-tuberculous Mycobacterium (NTM) and Mycobacterium (species broadly 
found in drinking water) were nominated for the CCL 5 and are not 
listed on the CCL 5 as a group; instead, two species of NTM that are 
found in drinking water, Mycobacterium avium and Mycobacterium 
abscessus, are listed.

C. Chemical Groups on the CCL 5

    In addition to the 66 individual chemicals listed on the CCL 5, EPA 
is listing cyanotoxins, DBPs, and PFAS as chemical groups instead of 
listing them as individual chemicals. One of the primary goals of the 
CCL process is to identify priority contaminants for further evaluation 
under the regulatory determination process and/or additional research 
and data collection. These chemical groups meet the CCL SDWA 
requirements and were also identified as agency priorities and 
contaminants of concern for drinking water under other EPA actions. 
Therefore, EPA is listing these three groups on CCL 5. EPA's approach 
to listing cyanotoxins, DBPs, and PFAS as groups on CCL 5 as opposed to 
listing them as individual contaminants limits duplication of agency 
efforts, such as data gathering, analyses and evaluations. Listing 
these three chemical groups on the 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. When making a determination to regulate a group, 
subgroup, or individual contaminants in the group, EPA must evaluate 
the group, subgroup, or individual contaminants under the three 
criteria in SDWA Section 1412(b)(1)(A).
    Addressing the public health concerns of cyanotoxins in drinking 
water remains an agency 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''). Cyanotoxins were included on CCL 4 as an aggregate group in 
order to encompass all toxins produced by cyanobacteria (including, but 
not limited to, microcystins, cylindrospermopsin, anatoxin-a and 
saxitoxins). The reason for this decision, and as stated in CCL 4, is 
the similar sources of cyanotoxins (i.e., cyanobacteria) indicate their 
management may be similar. EPA listed cyanotoxins as a group on the CCL 
5, identical to the CCL 4 listing.
    From 2018 to 2021 under EPA's Fourth Unregulated Contaminant 
Monitoring Rule (UCMR 4) Program, EPA coordinated with public water 
systems on the collection and reporting of nationally-representative 
finished drinking water cyanotoxin occurrence data for 10 cyanotoxins/
cyanotoxin congeners. The final UCMR 4 data were published on February 
18, 2022. UCMR 4 resulted in a low percentage of detections above the 
reference concentration and/or the national drinking water health 
advisory levels for the cyanotoxins monitored under UCMR 4. However, 
there are cyanotoxins that were not monitored as a part of UCMR 4. 
Also, significant health effects data and/or occurrence data are 
lacking for many of them (e.g., euglenophycin and saxitoxins). The 
prevalence, duration and frequency of HABs in freshwater is expanding 
in the U.S. and HABs continue to present a challenge for many state and 
local drinking water programs. Therefore, cyanotoxins continue to pose 
a potential public health risk and remain listed as a group on CCL 5.
    EPA is also listing 23 unregulated DBPs (as shown in Exhibit 2b) as 
a group on the CCL 5; either these DBPs were publicly nominated, among 
the top 250 chemicals, or both. DBPs are formed when disinfectants 
react with naturally occurring materials in water. Under the Six-Year 
Review 3 (SYR 3), EPA identified 10 regulated DBPs (all but bromate) as 
``candidates for revision'' (USEPA, 2017). EPA is conducting analyses 
to further evaluate the candidates for potential regulatory revisions 
identified under SYR 3 known as the Microbial Disinfection Byproducts 
(MDBP) Rule Revisions. Additionally, under the MDBP rule revisions 
effort, EPA is also evaluating information on unregulated DBPs.
    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 may have been manufactured 
and used in a variety of industries worldwide since the 1940s (USEPA, 
2019b). Additionally, chemical intermediates, degradates, processing 
aids, and by-products of PFAS manufacturing may also meet one or more 
of the structural definitions of PFAS making the listing of PFAS 
individually on the CCL 5 difficult and challenging. Listing PFAS as a 
group is responsive to public nominations which stated that EPA should 
``include PFAS chemicals as a class on CCL 5,'' and was supported by 
many public commenters and the SAB. EPA is listing PFAS as a group 
inclusive of any PFAS that fit the revised CCL 5 structural definition 
(except for PFOA and PFOS which have a proposed national primary 
drinking water regulation planned for late 2022). For the purposes of 
CCL 5, the structural definition of per- and polyfluoroalkyl substances 
(PFAS) includes chemicals that contain at least one of these three 
structures:
    (1) R-(CF2)-CF(R')R'', where both the CF2 and CF moieties are 
saturated carbons, and none of the R groups can be hydrogen.
    (2) R-CF2OCF2-R', where both the CF2 moieties are saturated 
carbons, and none of the R groups can be hydrogen.
    (3) CF3C(CF3)RR', where all the carbons are saturated, and none of 
the R groups can be hydrogen.
    EPA is also providing a list of PFAS that meet the CCL 5 structural 
definition (WATER[verbar]EPA: Chemical Contaminants--CCL 5 PFAS subset) 
on its CompTox dashboard (https://comptox.epa.gov/dashboard/chemical-lists).
    Listing PFAS as a group on CCL 5 supports the agency's commitment 
to

[[Page 68074]]

better understand and ultimately reduce the potential risks caused by 
this broad class of chemicals. It also demonstrates the agency's 
commitment to prioritizing and building a strong foundation of science 
on PFAS while working to harmonize multiple statutory authorities to 
address the impacts of PFAS on public health and the environment.
    EPA is also aware there may be emerging contaminants such as 
fluorinated organic substances that may be used in or are a result of 
the PFAS manufacturing process (e.g., starting materials, 
intermediates, processing aids, by-products and/or degradates) that do 
not meet the structural definition. Those emerging PFAS contaminants or 
contaminant groups may be known to occur or are anticipated to occur in 
public water systems, and which may require regulation. If emerging 
PFAS contaminants or contaminant groups are identified, EPA may 
consider moving directly to the regulatory determination process or 
consider listing those contaminants for future CCL cycles. EPA will 
continue to be proactive in considering evolving occurrence and health 
effects data of these emerging contaminants.

IV. What comments did EPA receive on the Draft CCL 5 and how did the 
Agency respond?

A. Public Comments

    With publication of the Draft CCL 5 in a Federal Register document 
on July 19, 2021 (86 FR 37948, USEPA, 2021e), EPA sought public comment 
on the following topics:
    1. Contaminants that EPA selected for the Draft CCL 5, and any 
supporting data that could assist with developing the Final CCL 5.
    2. Existing data that EPA obtained and evaluated for developing the 
Draft CCL 5.
    3. Improvements that EPA implemented for developing the Draft CCL 
5.
    The agency received a total of 54 unique comment letters from the 
public within the allotted 60-day comment period. EPA considered all 
public comments, data and information provided by commenters related to 
finalizing the CCL 5. EPA prepared responses to all public comments and 
included them in the ``Comment Response Document for the Draft Fifth 
Drinking Water Contaminant Candidate List (CCL 5)--Categorized Public 
Comment),'' which is available in the docket for this action (USEPA, 
2022d). A summary of the public's comments for the Draft CCL 5, along 
with EPA's responses, are provided in this section.
1. General Comments
    EPA received many general comments related to the Draft Fifth 
Contaminant Candidate List (CCL 5), including comments supporting EPA's 
mission of protecting human health by continuing to regulate 
contaminants in drinking water and identifying drinking water 
contaminants that may require regulation. EPA also received multiple 
comments supporting the CCL purpose and process.
2. Chemical Process and Chemical Contaminants
    EPA received multiple comments in support of continued improvements 
to CCL documentation, with several commenters recommending specific 
steps to facilitate transparency and clear communication of the CCL 
process. Two commenters requested that EPA expand on contaminants that 
appeared on CCL 4 but were not listed on CCL 5. In response to this 
comment EPA has provided a table in Appendix O of the Final CCL 5 
Chemical Technical Support Document (USEPA, 2022a).
a. Chemical Data/Data Sources
    EPA received two comments related to chemical data and data sources 
used in developing the CCL 5. This included a comment supporting the 
agency's use of preliminary Fourth Unregulated Contaminant Monitoring 
Rule (UCMR 4) data to develop the CCL 5 and the agency's ``decision to 
no longer exclude chemicals that could pose a public health risk 
through drinking water exposure from the CCL universe solely because 
they lack health or occurrence data.'' EPA also received a 
recommendation for the agency to expand the use wastewater data and 
data collected under Federal Insecticide, Fungicide, and Rodenticide 
Act (FIFRA) and the Toxic Substances Control Act (TSCA). EPA will 
consider expanding its uses of wastewater data and data collected under 
FIFRA and TSCA for future CCL cycles.
    EPA received comments requesting clarification on EPA's effort to 
combine the health data from multiple forms of some chemical 
contaminants when constructing the CCL 5 Chemical Universe. Another 
commenter had specific concerns about the chemical information sheets 
(CIS) for cypermethrin which included data for multiple isomers of the 
contaminant. In response to these comments, EPA has updated the 
Technical Support Document for the Draft Fifth Contaminant Candidate 
List (CCL 5)--Contaminant Information Sheet (USEPA, 2022c) for five 
contaminants to clarify which data entries are associated with which 
forms of the contaminant; these include cypermethrin, lithium, 
manganese, propiconazole, and vanadium.
b. Chemical Groups
    EPA received many comments related to the inclusion of three 
contaminant groups on the CCL 5: cyanotoxins, disinfection byproducts 
(DBPs), and per- and polyfluoroalkyl substances (PFAS). Many commenters 
expressed support for listing these three groups on the CCL 5, while 
many were opposed or expressed concerns with the ways the groups were 
defined.
i. Cyanotoxins
    EPA received comments supporting listing cyanotoxins as a group on 
the CCL 5. Supportive commenters noted the increase in frequency in 
harmful algal blooms (HABs) in drinking water sources, the widespread 
occurrence of cyanotoxins and often in complex mixtures, the harmful 
effects to humans and animals, and the challenges state drinking water 
treatment facilities face with water quality changes from HABs and 
removing cyanotoxins in a safe yet cost-effective way.
    In contrast, EPA received a comment suggesting that EPA explain the 
rationale for retaining cyanotoxins on the CCL 5. The commenter pointed 
to the low occurrence results of the cyanotoxins monitored under UCMR 
4. For EPA's rationale, see section III.C of this document.
ii. DBPs
    EPA received comments supporting listing unregulated DBPs on CCL 5. 
One commenter specifically supported listing bromochloroacetic acids 
(BCAA) as one of the unregulated DBPs in the group, noting the 
contaminant causes abnormalities in laboratory animals and is commonly 
found in drinking water. Another supporting commenter of listing 
unregulated DBPs also recommends that EPA work to fill research gaps 
for these contaminants, because few DBPs have been quantitatively 
assessed for their occurrence and health effects. The commenter further 
states that occurrence and health effects as well as additional data on 
the accuracy and reliability of analytical methods for detecting 
unregulated DBPs would be beneficial as EPA considers revisions to the 
MDBP rule regulations.
    A commenter asked the agency to provide justification on the lack 
of health effects and occurrence

[[Page 68075]]

information for the DBPs listed on the CCL 5 and on the selection of 
the 23 DBPs from hundreds of known DBPs. The commenter also stated that 
EPA should present the supporting data for including DBPs as a group in 
the CCL, since there are marked differences in occurrence and health 
effects information among these DBPs. The commenter did agree with 
EPA's stated intent of evaluating DBPs in a coordinated manner to 
assure adequate disinfection. Many commenters supported EPA's decision 
that DBPs should be listed as a group and suggested DBPs should be 
considered for regulatory determination and/or under the efforts of the 
Microbial Disinfection Byproducts Rule revisions.
    For CCL 5, the group of 23 unregulated DBPs includes the DBPs that 
were publicly nominated and/or in the top 250 scored CCL 5 Universe 
chemicals (outlined in Appendix P of the Final CCL 5 Chemical Technical 
Support Document). These DBPs bypassed the evaluation teams' review due 
to the ongoing EPA actions to consider revisions to five microbial and 
disinfection byproduct (MDBP) drinking water regulations in which EPA 
is also evaluating information on unregulated DBPs. Under the third 
Six-Year Review (SYR 3), EPA identified eight National Primary Drinking 
Water Regulations (NPDWRs) covered by five Microbial and Disinfection 
Byproducts (MDBP) rules as ``candidates for revision'' (USEPA, 2017). 
EPA is currently conducting analyses and consulting with the NDWAC to 
further evaluate these candidates and several unregulated DBPs for 
regulation under the potential revisions to the Microbial Disinfection 
Byproducts (MDBP) Rules. Additional information on the group of 23 
unregulated DBPs on CCL 5 is included in Section 4.7 of the Final CCL 5 
Chemical Technical Support Document.
iii. PFAS
    Some comments supported listing chemicals as groups on the CCL 5 
and in particular listing PFAS as a group. However, EPA received 
extensive comments opposing the Draft CCL 5 PFAS structural definition 
for being too narrow and excluding PFAS such as perfluoro-2-
methoxyacetic acid (PFMOAA), detected in the Cape Fear River source 
water and drinking water. For the CCL 5, EPA maintains its decision 
that the PFAS group meets the criteria for listing, which is that they 
are not yet subject to drinking water regulation, are known or 
``anticipated'' to occur in drinking water systems and may require 
drinking water regulation. EPA's decision to retain the group of PFAS 
on CCL 5 also aligns with the agency's commitment to address PFAS, 
which was laid out in its October 2021 PFAS Strategic Roadmap (USEPA, 
2021c).
    EPA agrees with the commenters who recommended expanding the CCL 5 
PFAS definition and in response, EPA is expanding the CCL 5 PFAS 
structural definition. For the CCL 5's PFAS structural definition, see 
section III.C of this document.
    EPA's revised CCL 5 PFAS definition captures PFAS known to occur in 
drinking water and/or source water. Many of these were mentioned in the 
public comments, such as perfluoro-2-methoxyacetic acid (PFMOAA) and 
perfluoro-2-methoxy propanoic acid (PMPA). The revised definition 
maintains the draft CCL 5 PFAS structural definition but augments it to 
include additional PFAS substructures such as PFAS that are ethers or 
highly branched, persistent in water, and known to occur in drinking 
water and/or source water. This revised definition is only for the 
purposes of CCL 5. It is not meant to represent an agency-wide 
definition. The definition could be revised for future cycles as more 
information is gathered on PFAS. EPA includes additional language in 
this notice acknowledging emerging PFAS contaminants that EPA may 
consider moving directly to the regulatory determination process or 
consider listing those contaminants for future CCLs. The FRN also 
references EPA's Comptox Database which includes a CCL 5 PFAS list of 
over 10,000 PFAS substances that meet the Final CCL 5 PFAS definition.
c. Individual Chemical Contaminants
    EPA received comments from multiple commenters regarding the 
listing status or information collected for individual contaminants 
listed on the Draft CCL 5. Some commenters expressed support for the 
listing of specific contaminants while others disagreed with EPA's 
evaluation and requested EPA reconsider listing specific contaminants 
on the Final CCL 5. EPA received comments pertaining to 1,4-dioxane, 
chlorpyrifos, cobalt, manganese, molybdenum, tungsten, and vanadium.
    EPA received comments supporting the listing of 1,4-dioxane, 
chlorpyrifos, and manganese. Commenters cite the need for updated 
health assessments, concerns about new or existing health effects, 
occurrence, and use data, and potential benefits of Federal regulations 
for states as reasons for supporting the listing decision made by EPA.
    EPA received comments requesting reevaluations of the listing 
decisions for cobalt, manganese, molybdenum, tungsten, and vanadium. 
Some commenters provided resources and analyses that they recommended 
EPA consider when listing a contaminant of interest. The 
recommendations provided by commenters frequently conflicted with 
established protocols and hierarchies that EPA applied uniformly across 
all chemical contaminants during the Classification step of CCL 5 
described in Chapter 4 of the Final CCL 5 Chemical Technical Support 
Document (USEPA, 2022a). However, EPA will consider these 
recommendations and comments on the protocol's strengths and weaknesses 
when reviewing potential modifications for future CCL cycles. 
Additionally, some recommendations, though outside the scope of the CCL 
process, may be useful during the Regulatory Determination process.
    EPA maintained the listing of 1,4-dioxane, chlorpyrifos, cobalt, 
manganese, molybdenum, tungsten, and vanadium on the Final CCL 5 
because they are known or anticipated to occur in public water systems, 
may require drinking water regulations, and therefore meet the SDWA 
requirements for listing on the CCL. EPA has provided individual 
responses to each comment received for individual contaminants in the 
Response to Comments Document on the Draft Fifth Contaminant Candidate 
List (CCL 5) document.
3. The Microbial Process and Microbial Contaminants
    EPA received a comment that neither the Draft CCL 5 FRN nor the CCL 
5 Microbial Technical Support Document (Technical Support Document of 
the Draft Fifth Contaminant Candidate List--Microbial Contaminants) 
described the weight-of-evidence approach used when applying the 
modification made to the exclusionary screening criteria applied to 
screen the microbial universe to the PCCL. The modification expanded 
Criterion 9 of the screening criteria to include nosocomial pathogens 
where drinking water-related infections were implicated. The comment 
also stated that if EPA finalizes CCL 5 retaining the incorporation of 
this modified criterion, it must more clearly describe its approach to 
implementing the revised criterion given that nosocomial infections 
occur under a unique combination of exposure scenarios and involve 
individuals that are very susceptible to infection. EPA addresses this 
comment by clarifying in the Technical Support Document for the

[[Page 68076]]

Final Fifth Contaminant Candidate List (CCL 5)--Microbial Contaminants, 
the approach to implementing the revised criterion.
a. Comments on Individual Microbial Contaminants
    EPA received comments on listing Legionella pneumophila and 
Mycobacterium. Two of the three commenters expressed support for 
listing the pathogen Legionella pneumophila on CCL 5, stating the 
burden Legionella pneumophila has on state drinking water programs. The 
third commenter recommended EPA address how the CCL 5 and MDBP rule 
revisions processes will interplay given the inclusion of the same 
contaminants, Legionella pneumophila, other pathogens, and DBPs being 
listed on CCL 5 as well as being considered in the MDBP rule revisions. 
EPA has listed Legionella pneumophila on CCL 5. The MDBP potential 
revisions are a separate agency action from CCL.
    EPA received one comment supporting the inclusion of Mycobacterium 
avium and Mycobacterium abscessus on CCL 5 and supports not listing 
Non-tuberculous Mycobacteria (NTM) as a group on the CCL. EPA has 
listed speciated Mycobacterium on the CCL 5, versus as a group.
4. Contaminants Not on CCL 5
    EPA received one comment to include two microbial contaminants, 
Hepatitis A and Salmonella enterica, on CCL 5. Hepatitis A and 
Salmonella enterica are not listed for CCL 5. Although both 
contaminants were listed on past CCLs, nominated for CCL 5, and still 
pose public health concerns, the outbreak data from CDC's NORS indicate 
that the route of exposure is not waterborne for the majority of 
infections.
5. Suggestions To Improve Future CCLs
    EPA received a comment to consider presenting CCL 5, and future 
CCLs, as an organized list that illustrates relative levels of 
potential risk and the gaps in information needed to craft risk 
management decisions. EPA does not organize CCLs based on ``relative 
levels of potential risk'' or ``gaps needed to craft risk management 
decisions'' because both of these actions require analysis and 
evaluation that is outside the scope of SDWA requirements for the CCL 
and align with the regulatory determinations and rule development 
process. However, EPA provides a table (Exhibit 4) in the FRN that 
shows the best available occurrence and health effects data for 
contaminants listed on CCL 5. Another commenter recommends that future 
CCLs be reviewed by an external expert panel in advance of the 
proposal. The commenter noted EPA prepared the Draft CCL 5 Federal 
Register notice without seeking external expert review as was 
recommended by NDWAC and has been past practice (e.g., CCLs 1 and 3). 
EPA will consider the use of an external expert panel for future CCLs.
    The commenter notes the technical support documents do not describe 
any internal process control measures, making the role of an 
independent third-party review even more important. EPA includes a 
description of the data management and quality assurance steps taken 
for the chemical CCL 5 process in Chapter 6 of the CCL 5 Final Chemical 
Technical Support Document (USEPA, 2022a).

B. Recommendations From the EPA Science Advisory Board

    On January 11, 2022, EPA held the first of five public meetings 
with the Science Advisory Board (SAB) Drinking Water Committee (DWC) 
Augmented for the CCL 5 review. During this initial meeting, EPA 
provided an overview of the process used to develop the Draft CCL 5 and 
answered questions from the Committee. EPA then requested Committee 
members to review the Draft CCL 5 materials and address the following 
charge questions:
    1. Please comment on whether the Federal Register notice and 
associated support documents are clear and transparent in presenting 
the approach used to list contaminants on the Draft CCL 5. If not, 
please provide suggestions on how EPA could improve the clarity and 
transparency of the FRN and the support documents.
    2. Please comment on the process used to derive the Draft CCL 5, 
including but not limited to, the CCL 5 improvements to assess 
potential drinking water exposure, consider sensitive populations, and 
prioritize contaminants that represent the greatest potential public 
health concern.
    3. Based on your expertise and experience, are there any 
contaminants currently on the Draft CCL 5 that should not be listed? 
Please provide peer-reviewed information or data to support your 
conclusion.
    4. Based on your expertise and experience, are there any 
contaminants which are currently not on the Draft CCL 5 that should be 
listed? Please provide peer-reviewed information or data to support 
your conclusion.
    On February 16 and February 18, 2022, EPA reconvened with the SAB 
DWC to discuss preliminary responses to the charge questions and answer 
remaining questions. The Committee met again on June 6, 2022 to discuss 
a draft of the final report, and again on July 18, 2022 to discuss 
their recommendations for CCL 5 with the Chartered SAB. The SAB's final 
recommendations were provided in their report ``Review of the EPA's 
Draft Fifth Drinking Water Contaminant Candidate List (CCL 5)'' (USEPA, 
2022e) to the EPA Administrator on August 19, 2022.

1. Overall SAB Recommendations

    The SAB commended EPA on the level of effort in developing the 
Draft CCL 5 and support documents. Overall, the SAB found the CCL 5 
development process and documentation clear and transparent. The SAB 
provided many recommendations in response to EPA's charge questions and 
emphasized the following ``key'' recommendations for CCL 5 and future 
CCLs to the Administrator.
     The SAB recommended that the EPA clarify the types of 
occurrence data that were included or rejected for consideration in 
development of the Draft CCL 5. In particular, clarifying how the 
literature review of the chemical contaminants in the Preliminary 
Contaminant Candidate List (PCCL) was conducted and used. Specifically, 
the SAB recommended providing an explicit list of the criteria used to 
screen chemical contaminants from the initial universe to form the PCCL 
before the point-based scoring is applied. The SAB suggested EPA 
explain the rationale for setting the threshold for the number of 
chemicals to be included on the Draft CCL 5 at 250.
    EPA response: In response to SAB's recommendation, the agency added 
clarification of how the occurrence literature review was conducted for 
the chemical process is described in Appendix E, Protocol of the 
Literature, of the Final CCL 5 Chemical Technical Support Document 
(2022a). The occurrence data that was considered for chemical 
contaminants can be found in the Appendix N, Data Management for CCL 5, 
of the Final CCL 5 Chemical Technical Support Document (2022a). 
Appendix N details the primary data sources that were considered for 
chemical contaminants. The information identified through the 
literature search was used to fill data gaps and provide additional 
information most relevant to drinking water exposure. This information 
was provided on the chemical CIS for the evaluators to consider when 
making their listing recommendations.

[[Page 68077]]

    For past CCLs, EPA has received many comments about CCLs consisting 
of too many contaminants. With over 20,000 chemicals in the CCL 5 
Universe and in response to past feedback, EPA used the screening 
scores to select and advance the top 250th scored chemicals for 
evaluation teams to review for potential inclusion on the CCL 5. 
Limiting the PCCL 5 to the top 250th scored chemicals, plus 53 
nominated chemicals that were not already included in the top scored 
chemicals, focuses EPA's resources on those contaminants with 
sufficient data to evaluate whether they are known, or anticipated to 
occur in public water systems and those that pose the greatest 
potential public health concern. EPA conducted statistical analyses and 
developed a logistic regression model to validate selection of the top 
250th scored chemicals for the PCCL 5. The results of those analyses 
are in Section 4.6 of the Final CCL 5 Chemical Technical Support 
document (USEPA, 2022a).
     The SAB supported the use of contaminant groups being 
listed on the CCL, but recommended transparency about the reasoning for 
listing contaminants as a group, and clarifying whether individual 
contaminants or subgroups within the groups should be prioritized. SAB 
also recommended EPA provide information on the criteria for grouping 
individual per- and polyfluoroalkyl substances (PFAS) and disinfection 
byproducts (DBPs) within the CCL 5. The SAB also recommended clarifying 
the justification for inclusion of cyanotoxins as a group despite 
relatively low occurrence data in the UCMR 4. In addition, the SAB 
recommended EPA elaborate on how listing contaminants as groups impacts 
the regulatory process.
    EPA response: In response to SAB's recommendations, EPA has 
provided additional rationale for listing contaminants as groups on CCL 
5 in Section III.C of this document. The objective of CCL is to 
identify priority contaminants for potential regulation. As described 
in Section III.C. of this document and also described in Section 4.7 of 
the Final CCL 5 Chemical Technical Support Document, cyanotoxins, DBPs, 
and PFAS are chemical groups that have already been identified as 
agency priorities and contaminants of concern for drinking water under 
other agency actions, including the 2015 Algal Toxin Risk Assessment 
and Management Strategic Plan for Drinking Water, EPA's decision to 
identify a number of microbial and disinfection byproducts (MDBPs) 
drinking water regulations as candidates for revision in the third Six-
Year Review (SYR 3) of the NPDWRs, and the 2021 PFAS Strategic Roadmap.
    EPA is listing cyanotoxins on CCL 5 as an aggregate group in order 
to encompass all toxins produced by cyanobacteria. For EPA's rationale 
see section III.C of this document.
    As information is available, EPA will evaluate the scientific data 
on the listed groups, including evaluating subgroups and/or individual 
contaminants within the groups to inform any regulatory determinations 
for the group, subgroup, or individual contaminants in the group.
     The SAB suggested that EPA elaborate on how sensitive 
populations were evaluated for chemical contaminant risks, clarify why 
immunosuppressed individuals are not considered sensitive populations 
and specify terminology regarding chronic disease and serious illness 
as risk factors when assessing microbial contaminant risks.
    EPA response: As described in Final CCL 5 Chemical Technical 
Support Document section 4.3.1, sensitive populations were evaluated 
based on calculating health concentrations. For carcinogens, the health 
concentration is the one-in-a-million (10-6) cancer risk 
expressed as a drinking water concentration. EPA applied age-dependent 
adjustment factors (ADAFs) to chemicals identified as having a 
mutagenic mode of action to account for risks associated with early 
life exposure to mutagenic carcinogens. For non-carcinogens, the 
toxicity value (RfD or equivalent) was divided by an exposure factor 
(i.e., body weight-adjusted drinking water intake; USEPA, 2019) 
relevant to the target population and critical effect and multiplied by 
a 20% relative source contribution (USEPA, 2000b). Target populations 
considered for CCL 5 include sensitive subpopulations such as bottle-
fed infants, pregnant women, and lactating women. If a chemical has 
toxicity values based on both cancer and non-cancer data, EPA selected 
the endpoint that resulted in the most health protective value as the 
final health concentration.
    As described in the FRN for the Draft CCL 5, EPA states ``The SDWA 
refers to several categories of sensitive populations including 
children and infants, elderly, pregnant women, and persons with a 
history of serious illness.'' Additionally, in the FRN for Draft CCL 5, 
EPA states ``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.'' EPA clarifies that 
the Agency does view immunocompromised individuals as a sensitive 
population, and immunocompromised populations are considered regardless 
of marked suppression of immune system and/or quality of health care 
when weighing health risks and when scoring the microbes' severity for 
CCL. See the Final CCL 5 Microbial Technical Support Document CIS 
sheets for supporting information. EPA has clarified the terms 
``chronic disease'' and ``serious illness'' in the Final CCL 5 
Microbial Technical Support Document (USEPA, 2022b).
     The SAB recommended EPA provide clarification of the 
difference in approach used by the chemical and microbial processes in 
regard to weighing expert opinion on contaminants to be included on the 
CCL 5.
    EPA response: For CCL 5, the microbial process relied on expert 
opinion for inclusion of contaminants on the CCL 5 due to the composite 
scores of the microbial PCCL 5 contaminants varying slightly (i.e., 0.1 
difference) of each other and having no natural break in scores, as was 
the case with CCL 3 and CCL 4. To ensure CCL 5 was capturing the 
microbial contaminants with the greatest public health risk, EPA 
consulted with CDC microbial experts. For the CCL 5 chemical process, 
EPA relied on two evaluation teams, internal subject matter experts, to 
evaluate 214 PCCL 5 chemicals and provide listing recommendations for 
CCL 5.
     The SAB recommended expanding the CCL 5 definition of PFAS 
to be more inclusive of a broad range of compounds of potential health 
risk, recommending a definition that captures all relevant fluorinated 
compounds and degradates in commercial use or entering the environment.
    EPA response: EPA revised the CCL 5 PFAS definition to be more 
inclusive. This revised definition maintains the Draft CCL 5 structural 
definition but is augmented to include additional PFAS substructures to 
address PFAS known to

[[Page 68078]]

occur in drinking water and/or source water, such as Perfluoro-2-
methoxyacetic acid (PFMOAA) and Perfluoro-2-methoxy propanoic acid 
(PMPA). This revised definition is only for the purposes of CCL 5. It 
is not meant to represent an agency-wide definition. The definition 
could be revised for future cycles as more information is gathered on 
PFAS. For more information on the CCL 5 PFAS group and structural 
definition, see Section IV.A.2.b.iii of this document.
     The SAB suggested that the definition and discussion of 
waterborne disease outbreaks (WBDO) as a criterion for microbial 
contaminant selection be expanded and relocated to earlier in the final 
FRN. The SAB further clarified that the discussion about WBDOs should 
include a clear outline of the definition, the limitations associated 
with the underlying data, how the data were used in the selection 
process, and how sensitive populations were considered. The SAB also 
recommended renaming ``health effects'' to ``health risks'' throughout 
the CCL 5 documents for both microbial and chemical contaminants.
    EPA response: In the Final CCL 5 Microbial Technical Support 
Document, EPA defines WBDOs, and further clarifies how WBDO data are 
used in the selection process, and how sensitive populations were 
considered for microbial contaminants. EPA acknowledges there are 
limitations to the use of WBDO outbreak data and has expanded the 
discussion of WBDO criteria to include the limitations associated with 
WBDO data in the Final CCL 5 Microbial Technical Support Document 
(USEPA, 2022b).
    EPA agrees that the term ``health risk'' rather than ``health 
effects'' is a more appropriate term to use in some instances. EPA 
considers risk to be the chance of harmful effects to human health or 
to ecological systems resulting from exposure to an environmental 
stressor (USEPA, 2022f). An endpoint may be associated with a risk of a 
disease which is determined after evaluating the health effects, 
occurrence, and potential exposure data. There are instances in the CCL 
5 process when EPA identifies an adverse health endpoint (or effect) 
from a health assessment but does not go further to analyze the risk of 
disease in humans and therefore the term ``health effects'' is 
appropriate. EPA has reviewed the use of the terms throughout the CCL 5 
documents and made the appropriate changes.
     The SAB recommended including additional bisphenols, 
bisphenol F (BPF) and bisphenol S (BPS) on the Final CCL 5. In addition 
to saxitoxin (STX), the EPA should include other saxitoxins including 
neo-STX and dc-STX on the Final CCL.
    EPA response: EPA reviewed the references provided by the SAB to 
support their recommendations for including Bisphenol S and F on CCL 5. 
However, there are still substantial health effects and occurrence data 
gaps for Bisphenol S and Bisphenol F to determine whether they are 
known, or anticipated to occur in public water systems and pose the 
greatest potential public health concern. Therefore, EPA is not listing 
them at this time. EPA will consider additional Bisphenols for future 
CCLs.
    Cyanotoxins is listed as a group on CCL 5. The group of cyanotoxins 
on CCL 5 includes, but is not limited to: Anatoxin-a, 
cylindrospermopsin, microcystins, and saxitoxin. As information is 
available, EPA will evaluate scientific data on the listed groups, 
subgroups, and/or individual contaminants included in the group to 
inform any regulatory determinations for the group, subgroup, or 
individual contaminants in the group.
     The SAB questioned how microbial organisms covered under 
existing regulations were listed on the CCL, for example Legionella and 
viruses covered by the Surface Water Treatment Rules (SWTRs) and Ground 
Water Rule (GWR). The SAB recommended that the EPA provide greater 
clarity on the process used to establish the list of microbial 
contaminants, as well as a rationale for carrying over most of the 
microbial contaminants from prior CCLs.
    EPA response: Despite the MCLGs for Legionella and for viruses, 
these contaminants have limitations as a class under the SWTRs and GWR, 
and therefore lack contaminant-specific monitoring and filtration or 
treatment requirements. Because Legionella and viruses have known 
public health risks associated in water systems and do not have 
specific regulatory requirements, EPA believes it is appropriate to 
list these as unregulated contaminants for purposes of inclusion on the 
CCL.
    For clarification, the microbial contaminants listed on CCL 5 that 
were listed on prior CCLs were not ``carried-over''; these contaminants 
did not receive positive determinations through the regulatory 
determination process, and therefore are placed back into the microbial 
universe. After evaluating these contaminants through the CCL microbial 
process, their composite scores consisting of health effects and 
occurrence data supported listing them for CCL 5. EPA has provided 
additional clarity on the process and justification for each microbial 
contaminant included on the Final CCL 5 Microbial Technical Support 
Document (USEPA, 2022b).
     The SAB suggested providing a table containing the 
considered PFAS, similar to the table for DBPs.
    EPA response: EPA is providing a list of PFAS chemicals included in 
the CCL 5 PFAS group (WATER[bond]EPA: Chemical Contaminants--CCL 5 PFAS 
subset) on the EPA's CompTox Dashboard website under List of Chemicals 
(https://comptox.epa.gov/dashboard/chemical-lists).
     The SAB suggested that EPA consider grouping other 
compounds, such as organophosphate esters and triazines.
    EPA response: EPA will take this recommendation into consideration 
for future CCLs.
     The SAB advised EPA to ensure that the CCL 5 microbial 
process incorporates the most up-to-date version of the Control of 
Communicable Diseases Manual.
    EPA response: EPA used the most up-to-date version of the Manual of 
Clinical Microbiology (MCM) and where the Control of Communicable 
Disease Manual is cited, a newer citation from either the MCM or CDC is 
also cited. EPA will ensure the most up-to-date version of the Control 
of Communicable Diseases Manual be used in future CCLs.
     The SAB proposed that EPA clarify the process of selecting 
contaminants for monitoring under the UCMR when contaminants had only 
health effects or occurrence data.
    EPA response: For each UCMR cycle, the UCMR program coordinates 
with the CCL program in establishing the list of contaminants for 
monitoring. UCMR considers contaminants listed on the CCL, other 
priority contaminants, and the opportunity to use multi-contaminant 
methods to collect occurrence data in an efficient, cost-effective 
manner.
    EPA evaluates candidate UCMR contaminants using a multi-step 
prioritization process. The first step includes identifying 
contaminants that: (1) were not monitored under prior UCMR cycles; (2) 
may occur in drinking water; and (3) are expected to have a completed, 
validated drinking water analytical method in time for rule proposal. 
The next step considers the following: availability of health 
assessments or other health-effects information (e.g., critical health 
endpoints suggesting carcinogenicity); public interest (e.g., PFAS); 
active use (e.g., pesticides that are registered for use); and 
availability of occurrence data.

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EPA also considers stakeholder input; looks at the cost-effectiveness 
of the potential monitoring approaches; considers implementation 
factors (e.g., laboratory capacity); and further evaluates health 
effects, occurrence, and persistence/mobility data.
     The SAB recommended that EPA further describe the validity 
of the health effects linear scoring system for microbial contaminants.
    EPA response: When the CCL microbial process was developed, it was 
recognized that pathogens may produce a range of illnesses, from 
asymptomatic infection to fulminate illness progressing rapidly to 
death. The health effect protocol scores are representative of common 
clinical presentation for specific pathogens for the population 
category under consideration. EPA believes the linear scoring system 
enables the reproducibility of the scores for health risks.
     The SAB suggested clarifying the reasons for calculating 
the Pathogen Total Score for microbial contaminants.
    EPA response: EPA uses the composite pathogen score, which factors 
in the microbe's three attribute scoring protocols for occurrence, 
waterborne disease outbreaks, and health effects to score and the rank 
contaminants on the PCCL. The composite score normalizes the health 
effects (for the general population and for sensitive populations) and 
occurrence because the agency believes they are of equal importance. 
This scoring system also prioritizes and restricts the number of 
pathogens on the CCL to those that are strongly associated with water-
related diseases.
     SAB recommended EPA clarify the reason for using a 10-year 
timeframe for the supplemental literature review for the chemical 
contaminants' occurrence data.
    EPA response: For CCL 5, EPA's goal was to conduct a targeted 
occurrence literature search for the chemical contaminants to identify 
supplemental data that would be more recent or provide more information 
on potential exposure from drinking water than information from primary 
data sources used to compile the CCL 5 Universe. For future CCLs, EPA 
will consider expanding the timeframe for occurrence literature 
searches for chemical contaminants.
     The SAB suggested that EPA compare the CCL 5 list to the 
European-based data to identify overlooked compounds of high concern.
    EPA response: For CCL 5, EPA incorporated the use of several 
European data sources in the CCL 5 process. Appendix B of the Final CCL 
5 Chemical Technical Support Document (USEPA, 2022a) list those data 
sources that were used as supplemental sources for CCL 5. For example, 
EPA searched for toxicity values such as derived no effect levels 
(DNELs) from European Chemicals Agency (ECHA) Registration Dossiers to 
derive CCL Screening Levels for chemicals of interest.
     The SAB recommended that EPA incorporate speciation 
information into the scoring system to aid in the justification for 
inclusion or exclusion of Vanadium in the Final CCL.
    EPA response: Based upon the data collected for CCL 5, including 
occurrence data collected for UCMR 3 and the available health 
assessments, EPA concludes that vanadium is known or anticipated to 
occur in public water systems and may require drinking water regulation 
and therefore meets the criteria for listing under the SDWA. EPA 
recognizes the value of data on vanadium speciation, both in terms of 
potential differences in health effects resulting from oral exposures 
and occurrence in water from public systems. EPA is aware that the 
National Toxicology Program (NTP) is currently conducting toxicity 
studies on vanadyl sulfate (+4) and sodium metavanadate (+5) to fill 
data gaps. When NTP publishes their subchronic study results, it will 
contribute to the vanadium health effects database to be considered for 
the Regulatory Determination Process and/or future CCL cycles.
     The SAB recommended removing Shigella sonnei, 
Campylobacter and Helicobacter pylori from the Final CCL 5. In 
addition, before finalizing CCL 5, the SAB also suggested that EPA 
conduct further evaluation of caliciviruses and provide further 
justification for including enteroviruses and Human Adenovirus on CCL 
5.
    EPA response: Shigella sonnei, Campylobacter jejuni, caliciviruses, 
enteroviruses, and adenovirus remain a concern for vulnerable water 
systems such as undisinfected (i.e., undisinfected ground water 
systems) or inadequately disinfected systems. EPA has provided 
additional supporting evidence and justification of inclusion of each 
microbial organism on the CCL 5 in the Final CCL 5 Microbial Technical 
Support Document.
     The SAB recommended that EPA clearly communicate the 
relative levels of potential risk and gaps in information needed to 
craft risk management decisions for PFAS.
    EPA response: The SDWA requires EPA to follow a process to identify 
unregulated contaminants for potential regulation. The CCL is one of 
the many integral components of EPA's coordinated risk management 
process. The objective of CCL is to identify contaminants of concern in 
drinking water to inform and assist in priority-setting efforts for 
potential regulatory determination. The process of Regulatory 
Determination examines in depth if there is sufficient data for EPA to 
make a decision on whether EPA should initiate a rulemaking process to 
develop an NPDWR for a specific contaminant.
2. Recommendations for Future CCLs
    For future CCLs, the SAB suggested that EPA bring the processes for 
selecting the chemical contaminants and the microbial contaminants into 
better alignment with each other, noting that currently the two 
processes differ in detail and technique. EPA recognizes the 
differences between the chemical and microbial processes due to 
differing metrics and data availability for contaminant assessment. 
Although the chemical and microbial processes differ, the overarching 
steps of the CCL process of building the universe, screening, and 
classification of contaminants are followed in parallel. However, for 
future CCLs, EPA will re-examine both the chemical and microbial 
processes to determine if there are benefits to aligning the two 
processes.
    Specifically, for the CCL chemical process, the SAB recommended 
future CCLs consider evaluating contaminants such as: shorter lived 
pesticides that transform into longer-lived metabolites or degradates, 
urban runoff occurrence data in parallel with wastewater occurrence 
data, assess data gathered in Europe during the implementation of the 
REACH system, the NORMAN network, and IP-CHEM databases to assess 
contaminants in surface or drinking water, identify and assess by-
products, impurities, and transformation products (including 
metabolites and degradates), persistent and mobile organic compounds 
(PMOCs), antimicrobials, microplastics, nanoparticles, and weigh 
whether to include manganese and tungsten on future CCLs.
    To improve the CCL chemical processes, the SAB suggested the 
following for future CCLs: consider employing machine learning to 
identify whether there may be other compounds of concern within the 
baseline of compounds, report the range and median method detection 
limit and reporting limit for each occurrence dataset listed in the CIS 
and using this information to inform the prevalence score for chemical 
contaminants, ensure that data cited in secondary sources are

[[Page 68080]]

from qualifying primary sources, observe anticipated speciation of 
metals in drinking water and potential source waters including 
groundwater. In addition, the SAB recommended that EPA develop a 
strategy to address the gap in occurrence data that will arise when the 
U.S. Geological Survey (USGS) discontinues its contaminants monitoring 
program.
    For future CCLs EPA will consider evaluating the data sources that 
the SAB referenced for the groups of contaminants in their CCL 5 
recommendations, including additional European-based data sources, to 
determine if those sources are appropriate to use as primary data 
sources when developing the chemical universe or supplemental data 
sources when filling data gaps for future CCLs. EPA will also consider 
evaluating the contaminants SAB has referenced. In addition, EPA will 
reconsider the use of machine learning in the future rounds of CCL. 
Also, EPA intends to continue to use the USGS compiled for CCL 5 for 
future CCLs but will consider other strategies to address the gap in 
occurrence data that will arise when the USGS ends its contaminant 
monitoring program.
    For the microbial process, the SAB suggested future CCLs consider 
adding a group of pathogenic mycobacteria to focus research and public 
health protection on a more identifiable and actionable group of 
opportunistic pathogens in comparison to the nondescript NTM 
designation. EPA will take this recommendation into consideration for 
future CCLs.
3. EPA's Overall Response to SAB Recommendations
    EPA has considered all SAB's comments and incorporated 
recommendations, where applicable, for the Final CCL 5 to increase the 
scientific concepts, clarity, and transparency of the decisions 
relative to the contaminants included on CCL 5. These updates/changes 
are reflected in the Final CCL 5 Chemical and Microbial Technical 
Support Documents (USEPA, 2022a and USEPA, 2022b, respectively). Other 
recommendations made by SAB in their final report (2022e) will be 
considered for future CCLs.

V. Data Availability for CCL 5 Contaminants

    In an effort to provide current data availability of the CCL 5 
contaminants with respect to occurrence and health effects data and EPA 
approved analytical methods, EPA has provided a summary table in 
Exhibit 4, depicting the CCL 5 chemicals categorized into five groups 
depending upon the availability of their occurrence data and peer-
reviewed health assessment(s) containing oral toxicity values at the 
time of the Draft CCL 5 publication. The status of health effects data 
availability for the CCL chemical contaminants, as of the date by which 
each chemical was evaluated for placement on the Draft CCL 5 (February 
to July 2020) and for analytical methods (September 2020) is presented 
in Exhibit 4.
    For individual chemicals of the cyanotoxins, DBPs and PFAS groups, 
the availability of health effects and occurrence data varies with 
individual chemicals in each group. The agency is addressing these 
groups broadly, instead of individually, 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.
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    As shown in Exhibit 4, Group A are contaminants that have 
nationally representative finished drinking water data and a peer 
reviewed health assessment deriving an oral toxicity value and are 
likely to have sufficient data available to be placed on a short list 
for further assessment under RD 5. The contaminants in Group B have 
finished drinking water data that is not nationally representative and 
peer reviewed health assessments. Group B contaminants may have 
sufficient data to be placed on a short list for further assessment 
under RD 5, particularly if the non-nationally representative 
occurrence data shows detections at levels of public health concern. 
Contaminants in groups C, D, and E of Exhibit 4 are those that lack 
either a peer reviewed health assessment or finished water data have 
more substantial data needs and are unlikely to have sufficient 
information to allow further assessment under RD 5. For Groups C, D, 
and E, EPA plans to identify them as research priorities and work to 
fill their research needs such as evaluating the potential for 
monitoring under the UCMR program or identifying those contaminants as 
priorities for health effects research. In addition, EPA assessed the 
data availability of the PCCL 5 chemicals that are not included on CCL 
5. For more information on EPA methodology to identify data 
availability and summary tables, see Chapter 5 of the Final CCL 5 
Chemical Technical Support Document (USEPA, 2022a).
    The SAB and other commenters have recommended additional 
prioritization of the CCL 5 contaminants to communicate research needs, 
help focus efforts for researchers, and inform future regulatory 
decision-making. EPA acknowledges that multiple contaminants on the CCL 
5 have substantial data and information needs to fulfill in order for 
the agency to make a regulatory determination in accordance with SDWA 
1412 (b)(1)(A). By identifying those contaminants that need additional 
research and information, EPA is communicating to stakeholders both 
research priorities and gaps for these contaminants.

VI. Next Steps and Future Contaminant Candidate Lists

    The CCL process is critical to shaping the future direction of 
drinking water regulations. The agency will continue to examine 
relevant research studies and gather additional data to prioritize CCL 
5 contaminants to make regulatory determinations on at least five 
contaminants for Regulatory Determination 5. The agency will also 
continue to refine the CCL process, gather and examine the best 
available data, and identify contaminants for the CCL 6. EPA expects to 
complete the CCL 6 in late 2026.

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VII. 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.
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.
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. Docket ID No. W-97-11
USEPA. 1999. Revisions to the Unregulated Contaminant Monitoring 
Regulation for Public Water Systems. Federal Register. Vol. 64, No. 
180, p. 50556, September 17, 1999. Docket No. FRL-6433-1
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. Docket 
ID No. OW-2002-0021
USEPA. 2005. Drinking Water Contaminant Candidate List 2; Final 
Notice. Federal Register. Vol. 70, No. 36. p. 9071, February 24, 
2005. Docket ID No. OW-2003-0028
USEPA. 2007. Unregulated Contaminant Monitoring Regulation (UCMR) 
for Public Water Systems Revisions; Correction. Federal Register. 
Vol. 72, No. 19, p. 4328, January 30, 2007. Docket ID No. OW-2004-
0001
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. 
Docket ID No. EPA-HQ-OW-2007-0068
USEPA. 2009. Drinking Water Contaminant Candidate List 3--Final. 
Federal Register. Vol. 74, No. 194. p. 51850, October 8, 2009. 
Docket ID No. EPA-HQ-OW-2007-1189
USEPA. 2011. Drinking Water: Regulatory Determination on 
Perchlorate. Federal Register. Vol. 76, No. 29. p. 7762, February 
11, 2011. EPA Docket ID No. EPA-HQ-OW-2009-0297
USEPA. 2012. Revisions to the Unregulated Contaminant Monitoring 
Regulation (UCMR 3) for Public Water Systems. Federal Register. Vol. 
77, No. 85. p. 26071, May 2, 2012. Docket ID No. EPA-HQ-OW-2009-0090
USEPA. 2015. Algal Toxin Risk Assessment and Management Strategic 
Plan for Drinking Water, Strategy Submitted to Congress to Meet the 
Requirements of Public Law 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. Docket ID No. EPA-HQ-OW-
2015-0218
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. Docket ID No. EPA-HQ-OW-2012-0155
USEPA. 2016c. Drinking Water Contaminant Candidate List 4-Final. 
Federal Register. Vol. 81, No. 222. P. 81099, November 17, 2016. 
Docket ID No. EPA-HQ-OW-2012-0217
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. Docket ID No. EPA-HQ-
OW-2018-0594
USEPA. 2018b. Basic Information on PFAS. Available at: https://www.epa.gov/pfas/basic-information-pfas.
USEPA. 2019a. Drinking Water: Perchlorate Proposed Rule. Federal 
Register. Vol. 84, No. 123, p. 30524, June 26, 2019. EPA Docket No. 
EPA-HQ-OW-2018-0780
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: Final Action on Perchlorate. Federal 
Register. Vol. 85, No. 140, p. 43990. July 21, 2020. EPA Docket No. 
EPA-HQ-OW-2018-0780; EPA-HQ-OW-2008-0692; EPA-HQ-OW-2009-0297
USEPA. 2021a. Childhood Lifestages relating to Children's 
Environmental Health. Available at https://www.epa.gov/children/childhood-lifestages-relating-childrens-environmental-health.
USEPA. 2021b. Revisions to the Unregulated Contaminant Monitoring 
Rule (UCMR 5) for Public Water Systems and Announcement of Public 
Meetings. Federal Register. Vol. 86, No. 245. p. 73131, December 27, 
2021. Docket ID No. EPA-HQ-OW-2020-0530
USEPA. 2021c. PFAS Strategic Roadmap: EPA's Commitments to Action, 
2021-2024. EPA 100-K-21-002. October 2021.
USEPA. 2021d. 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. 
Docket ID No. EPA-HQ-OW-2019-0583.
USEPA. 2021e. Drinking Water Contaminant Candidate List 5--Draft. 
Federal Register. Vol. 86, No. 135, p. 37948, July 19, 2021. Docket 
ID No. EPA-HQ-OW-2018-0594
USEPA. 2022a. Technical Support Document for the Final Fifth 
Contaminant Candidate List (CCL 5)--Chemical Contaminants. EPA 815-
R-22-002, September 2022.
USEPA. 2022b. Technical Support Document for the Final Fifth 
Contaminant Candidate List (CCL 5)--Microbial Contaminants. EPA 815-
R-22-004, September 2022.
USEPA. 2022c. Technical Support Document for the Final Fifth 
Contaminant Candidate List (CCL 5)--Contaminant Information Sheets. 
EPA 815-R-22-003, September 2022.
USEPA. 2022d. Comment Response Document for the Draft Fifth Drinking 
Water Contaminant Candidate List (CCL 5)--Categorized Public 
Comment. EPA 815-R-22-001, September 2022.
USEPA. 2022e. Review of the EPA's Draft Fifth Drinking Water 
Contaminant Candidate List (CCL 5). EPA-SAB-22-007, August 19, 2022.
USEPA. 2022f. About Risk Assessment. Available at https://www.epa.gov/risk/about-risk-assessment.

Radhika Fox,
Assistant Administrator.
[FR Doc. 2022-23963 Filed 11-10-22; 8:45 am]
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