[Federal Register Volume 87, Number 218 (Monday, November 14, 2022)]
[Rules and Regulations]
[Pages 68060-68085]
[FR Doc No: 2022-23963]

-----------------------------------------------------------------------

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.

-----------------------------------------------------------------------

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<PHONE_NUMBER> 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<PHONE_NUMBER> 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

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).
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

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

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

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
[GRAPHIC] [TIFF OMITTED] TR14NO22.015

[GRAPHIC] [TIFF OMITTED] TR14NO22.016

[GRAPHIC] [TIFF OMITTED] TR14NO22.017

[GRAPHIC] [TIFF OMITTED] TR14NO22.018

B. Microbial Contaminants

[GRAPHIC] [TIFF OMITTED] TR14NO22.019

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.

[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

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).
[GRAPHIC] [TIFF OMITTED] TR14NO22.021

[GRAPHIC] [TIFF OMITTED] TR14NO22.022

[GRAPHIC] [TIFF OMITTED] TR14NO22.023

[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).

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

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

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

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.

    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

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.

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

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.
BILLING CODE 6560-50-P

[GRAPHIC] [TIFF OMITTED] TR14NO22.025

[GRAPHIC] [TIFF OMITTED] TR14NO22.026

[GRAPHIC] [TIFF OMITTED] TR14NO22.027

[GRAPHIC] [TIFF OMITTED] TR14NO22.028

BILLING CODE 6560-50-C
    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.

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]
BILLING CODE 6560-50-P