[Federal Register Volume 91, Number 65 (Monday, April 6, 2026)]
[Proposed Rules]
[Pages 17186-17195]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2026-06662]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 141
[EPA-HQ-OW-2022-0946; FRL-10773-01-OW]
Drinking Water Contaminant Candidate List 6--Draft
AGENCY: Environmental Protection Agency (EPA).
ACTION: Notice of availability; request for comments.
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SUMMARY: The U.S. Environmental Protection Agency (EPA) is publishing a
draft list of contaminants that are currently not subject to any
proposed or promulgated national primary drinking water regulations for
public review and comment. These contaminants are known or anticipated
to occur in public water systems and may require regulation under the
Safe Drinking Water Act (SDWA) in the future. The draft list provided
in this document is the sixth Contaminant Candidate List (CCL)
published by the Agency since the SDWA amendments of 1996. The draft
Sixth Contaminant Candidate List (CCL 6 or the list) includes 75
chemicals, 4 chemical groups (disinfection byproducts (DBPs),
microplastics, per- and polyfluoroalkyl substances (PFAS), and
pharmaceuticals) and 9 microbes. The EPA seeks public comment on the
draft CCL 6 and the process used to develop the draft CCL 6. The EPA
will consider all information and comments received in response to this
notice of availability for determining the final CCL 6.
DATES: Comments must be received on or before June 5, 2026.
ADDRESSES: You may send comments, identified by Docket ID Number EPA-
HQ-OW-2022-0946, by any of the following methods:
Federal eRulemaking Portal: https://www.regulations.gov
(our preferred method). Follow the online instructions for submitting
comments.
Mail: U.S. Environmental Protection Agency, EPA Docket
Center, Water Docket, Environmental Protection Agency, Mail code:
28221T, 1200 Pennsylvania Ave. NW, Washington, DC 20460.
Hand Delivery/Courier: 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.-4:30 p.m., Monday
through Friday (except Federal Holidays).
Instructions: All submissions received must include the Docket ID
No. EPA-HQ-OW-2022-0946 for this rulemaking. Comments received may be
posted without change to https://www.regulations.gov, including any
personal information provided. For detailed instructions on sending
comments and additional information on the rulemaking process, see the
``Public Participation'' heading of the SUPPLEMENTARY INFORMATION
section of this document.
FOR FURTHER INFORMATION CONTACT: Thomas Lombardi, Standards and Risk
Management Division, Office of Ground Water and Drinking Water; email:
[email protected]; telephone: (202) 564-7653.
SUPPLEMENTARY INFORMATION:
Table of Contents
I. General Information
A. Does this action impose any requirements on public water
systems?
B. Public Participation
C. What should I consider as I prepare my comments for the EPA?
II. Purpose, Background, and Statutory Requirements of This Action
A. What is the purpose of this action?
B. Background and Statutory Requirements for the CCL
C. Interrelationship of the CCL and Related SDWA Programs,
Regulatory Determinations, and Unregulated Contaminant Monitoring
Rule
D. Summary of the Most Recent CCL
E. What is included on the draft CCL 6?
III. Developing the Draft CCL 6
A. Approach Used To Identify Chemical Candidates for the Draft
CCL 6
1. Building the Chemical Universe
2. Screening the Chemical Universe to a Preliminary Contaminant
Candidate List (PCCL)
3. Classification of PCCL Chemical Contaminants To Select a
Draft CCL
a. Supplemental Data Collection Used in Classification
b. Evaluation Team Listing Recommendation Process
c. Additional Refinement for Contaminants With Previous Negative
Regulatory Determinations
d. Chemical Groups on the Draft CCL 6
i. Disinfection Byproducts
ii. Microplastics
iii. Per- and Polyfluoroalkyl Substances
iv. Pharmaceuticals
B. Approach Used To Identify Microbial Candidates for the Draft
CCL 6
1. Building the Microbial Universe
2. Screening the Microbial Universe to a Preliminary Contaminant
Candidate List (PCCL 6)
3. Review of PCCL 6 Microbial Contaminants To Select a Draft CCL
6
a. Selection of the Draft CCL 6 Microbes
C. Summary of Nominated Candidates for the Draft CCL 6
D. Data Needs for the Draft CCL 6
IV. Request for Comments
V. The EPA's Next Steps
VI. References
I. General Information
A. Does this action impose any requirements on public water systems?
The draft CCL 6 and the final CCL 6, when published, will not
impose any requirements on regulated entities.
B. Public Participation
Submit your comments, identified by Docket ID No. EPA-HQ-OW-2022-
0946, at https://www.regulations.gov, (our preferred method), or the
other methods identified in the ADDRESSES section of this document.
Once submitted, comments cannot be edited or removed from the docket.
The EPA may publish any comment received to its public docket. Do not
submit
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electronically any information you consider to be Confidential Business
Information (CBI) or other information whose disclosure is restricted
by statute. Multimedia submissions (audio, video, etc.) must be
accompanied by a written comment. The written comment is considered the
official comment and should include discussion of all points you wish
to make. The EPA will generally not consider comments or comment
contents located outside of the primary submission (i.e., on the web,
cloud, or other file sharing system). For additional submission
methods, the full EPA public comment policy, information about CBI or
multimedia submissions, and general guidance on making effective
comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.
C. What should I consider as I prepare my comments for the EPA?
You may find the following suggestions helpful for preparing your
comments:
--Explain your views as clearly as possible.
--Describe any assumptions that you used.
--Provide any technical information, alternative scientific analyses,
and/or data you used that support your views.
--Provide full references for any peer reviewed publication you used
that support your views.
--Provide specific examples to illustrate your concerns.
--Offer alternatives.
Make sure to submit your comments by the comment period deadline.
To ensure proper receipt by the EPA, identify the appropriate docket
identification number in the subject line on the first page of your
response. It would also be helpful if you provided the name, date, and
Federal Register citation related to your comments.
II. Purpose, Background, and Statutory Requirements of This Action
This section briefly summarizes the purpose of this action, the
statutory requirements, previous activities related to the CCL and the
approach used to develop the draft CCL 6.
A. What is the purpose of this action?
The purpose of this action is to present and seek comment upon the
EPA's draft CCL 6 and the selection process used to make the list. When
finalized, CCL 6 will be used to prioritize research and data
collection efforts for drinking water contaminants. In a future,
separate action the EPA will make regulatory determinations on whether
to regulate at least five contaminants from the CCL with National
Primary Drinking Water Regulations (NPDWRs) under the SDWA, section
1412(b)(1)(B)(ii).
B. Background and Statutory Requirements for the CCL
SDWA section 1412(b)(1)(B)(i), as amended in 1996, requires the EPA
to publish the CCL every five years. SDWA specifies that the list must
include contaminants that are not subject to any proposed or
promulgated NPDWRs, are known or anticipated to occur in public water
systems (PWSs), and may require regulation under the SDWA. The statute
provides that 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). SDWA section 1412(b)(1)(C) directs the EPA to
identify those contaminants that present the greatest public health
concern related to exposure from drinking water, and, in making such
selection, to take into consideration the human health effects after
exposure to a contaminant specifically to sensitive 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.
C. Interrelationship of the CCL and Related SDWA Programs, Regulatory
Determinations, and Unregulated Contaminant Monitoring Rule
The CCL is the first step in the SDWA regulatory framework, serving
as the initial screening of contaminants to identify those which may
require regulation under SDWA. The CCL informs future Unregulated
Contaminant Monitoring Rules (UCMR) and Regulatory Determinations. The
inclusion of a contaminant on the CCL, whether as an individual or in a
group, does not mean that any particular contaminant will necessarily
be regulated in the future. Rather, the CCL serves as a first level of
evaluation for unregulated drinking water contaminants that may need
further investigation of potential health effects and the levels at
which they are found in drinking water. Contaminants from the CCL with
sufficient health effects and occurrence information are considered for
regulatory determination and rulemaking under SDWA.
SDWA section 1445(a)(2) as amended in 1996, requires that once
every five years the EPA issues a UCMR with a list of no more than 30
unregulated contaminants to be monitored in drinking water by PWSs. The
UCMR provides nationally representative occurrence data for unregulated
contaminants in drinking water. The UCMR is related to the CCL in two
ways. First, EPA considers contaminants from the CCL in selecting
contaminants for the UCMR. Second, the contaminant occurrence data
collected under the UCMR can inform EPA's consideration of contaminants
for future CCLs.
The CCL is also related to the regulatory determinations process.
Following the publication of a final CCL, the EPA evaluates those CCL
contaminants with sufficient information to make a regulatory
determination, using the three statutory criteria listed in SDWA
section 1412(b)(1)(A):
1. The contaminant may have an adverse effect on the health of
persons;
2. 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
3. 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.
Based upon this evaluation, the EPA determines whether a regulation
is appropriate (positive determination) or not appropriate (negative
determination). The EPA is required by SDWA to make regulatory
determinations for at least five contaminants listed on the CCL every
five years.
D. Summary of the Most Recent CCL
The EPA has published five CCLs since 1996. The EPA published its
most recent CCL, CCL 5, in the Federal Register (87 FR 68060, USEPA
2022a) on November 14, 2022. The final CCL 5 included 81 contaminants
or groups. The list is comprised of 66 chemicals, 3 chemical groups
(cyanotoxins, disinfection byproducts (DBPs), and per- and
polyfluoroalkyl substances (PFAS)) and 12 microbial contaminants.
E. What is included on the draft CCL 6?
The draft CCL 6 includes 88 contaminants (Exhibits 1a, 1b, and 1c
of this document). The list is comprised of
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75 chemicals, four chemical groups, and nine microbes.
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III. Developing the Draft CCL 6
In developing the draft CCL 6, the EPA followed a 3-step process
that is illustrated in Exhibit 2 of this document. The EPA applied this
process separately to both chemical and microbial contaminants to
develop the draft CCL 6. In the first step, the Agency developed the
CCL 6 Chemical Universe and the CCL 6 Microbial Universe by compiling
available health and occurrence data. In the second step, the EPA
developed subsets of the Chemical Universe and Microbial Universe,
called the Chemical and Microbial Preliminary Contaminant Candidate
Lists (PCCLs), by prioritizing contaminants using a
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points-based screening system. Finally in the third step, the EPA
selected the contaminants from the Chemical and Microbial PCCLs that
are most likely to occur in public water systems and that pose the
greatest potential public health concern in drinking water. Exhibit 2
of this document lists the number of chemicals, chemical groups and
microbes the EPA considered at each step of the process.
Exhibit 2--Overall Draft CCL 6 Development Process and Contaminant
Counts
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The draft CCL 6 technical support documents provide comprehensive
details about the draft CCL 6 chemical and microbial processes:
Technical Support Document for the Draft Sixth Contaminant Candidate
List (CCL 6)--Chemical Contaminants (USEPA, 2026a) and the Technical
Support Document for the Draft Sixth Contaminant Candidate List (CCL
6)--Microbial Contaminants (USEPA, 2026c), hereafter referred to as the
Chemical Technical Support Document and Microbial Technical Support
Document, respectively.
A. Approach Used To Identify Chemical Candidates for the Draft CCL 6
1. Building the Chemical Universe
In the first step of the CCL 6 development process for chemical
candidates, the EPA identified a broad universe of potential drinking
water contaminants. The EPA began the development process by compiling
data sources to identify chemicals for inclusion in the CCL 6 Chemical
Universe. The EPA identified data sources from previous CCLs, the
Science Advisory Board (SAB), and scientific literature searches.
The EPA assessed data sources for their potential use in the CCL 6
development process based on four assessment factors; relevancy,
completeness, redundancy, and retrievability. The EPA identified 20
sources of health effects data and 41 sources of occurrence data,
including 18 new data sources. In total, 25,305 chemicals were
identified from the main data sources and comprise the CCL 6 Chemical
Universe. This is the largest universe of chemicals and the greatest
number of data sources that the EPA has evaluated for any CCL. For more
information about building the CCL 6 Chemical Universe and data sources
used, see Chapter 2 of the Chemical Technical Support Document (USEPA,
2026a).
2. Screening the Chemical Universe to a Preliminary Contaminant
Candidate List (PCCL)
In the second step of the CCL 6 development process, the EPA
screened chemicals from the CCL 6 Chemical Universe to identify the
list of chemicals that should be further evaluated, namely the PCCL 6.
The EPA applied a points-based screening system to determine which
contaminants are placed onto the PCCL. The EPA assigned cumulative
points to contaminants across health effects and occurrence data
elements. The scoring is described in Section 3.2 of the Chemical
Technical Support Document (USEPA, 2026a). The EPA used these screening
scores, along with statistical models and analyses described in Section
4.6 of the Chemical Technical Support Document (USEPA, 2026a), to
prioritize chemicals to inform the PCCL 6.
The EPA identified the highest scoring chemicals for inclusion on
the PCCL 6 and validated the selection of the top scoring chemicals and
the screening score framework using a statistical modeling approach. As
a result of screening the CCL 6 Chemical Universe, the PCCL 6 started
with 274 chemicals. From this pool, the protocol excluded 34 chemicals
from the PCCL: nine chemicals were excluded due to
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recent regulatory determinations made for contaminants on CCL 5 (90 FR
3830, USEPA, 2025) or a pending Agency action. An additional 25
chemicals were excluded because they were canceled pesticides with no
reported alternative uses that break down quickly in the environment
and are therefore not anticipated to occur in public water systems.
The EPA also excluded chemicals from the base PCCL 6 that were
within chemical groups that the Agency had determined to list (see
Exhibit 1b and section III.A.3.d of this document). Eight chemicals
were excluded because EPA had determined to include them in the DBP
group, 15 chemicals were excluded because EPA had identified them for
inclusion under the pharmaceutical group, and four other chemicals were
excluded because EPA found they met the structural definition
requirements for inclusion within the PFAS group (see Exhibit 1b for
more details). In total, 213 chemicals remained on the PCCL 6 to be
evaluated individually in the classification step. A more detailed
summary of the PCCL 6 is included in Section 3.8 of the Chemical
Technical Support Document (USEPA, 2026a).
3. Classification of PCCL Chemical Contaminants To Select a Draft CCL
In the third step of the CCL process, the EPA narrowed down the
PCCL 6 to determine the draft CCL 6 through a classification process.
For the purposes of CCL 6, classification refers to the process by
which, first, the Agency incorporated the knowledge and evaluation by
the EPA scientists, referred to as ``chemical evaluators,'' to
recommend contaminants for listing for the draft CCL. To facilitate the
classification process, the EPA conducted literature and assessment
searches to gather supplemental health and occurrence data for the PCCL
6 chemicals. The main and supplemental data were compiled by chemical,
and relevant health effects and occurrence data metrics were imported
into a standardized document format, called the Contaminant Information
Sheet (CIS) that are provided in the Technical Support Document for the
Draft Sixth Contaminant Candidate List (CCL 6)--Contaminant Information
Sheets (USEPA, 2026b). The chemical evaluators reviewed the health
effects and occurrence information provided on the CISs to inform
consensus listing recommendations for the PCCL chemicals.
a. Supplemental Data Collection Used in Classification
During classification, the EPA gathered supplemental data to better
evaluate the PCCL 6 chemicals and determine which contaminants were
more likely to be present in drinking water at levels that may require
regulation. These supplemental data were used to inform more specific
evaluations of the PCCL 6 chemicals. For example, supplemental health
data was gathered to calculate health concentrations, which are non-
regulatory health-based toxicity values at or below which no adverse
effects are expected to occur. The EPA compares occurrence data to the
health concentrations to characterize the likelihood that the
contaminant may be in drinking water at levels of health concern that
may require regulation. Information on supplemental data used in the
draft CCL 6 is in Section 4.2 of the Chemical Technical Support
Document (USEPA, 2026a).
b. Evaluation Team Listing Recommendation Process
Chemical evaluators reviewed the health effects and occurrence data
on the CIS for each chemical, and the evaluation teams provided
consensus listing recommendations. A detailed description of the
chemical evaluation team listing process can be found in Section 4.5 of
the Chemical Technical Support Document (USEPA, 2026a).
c. Additional Refinement for Contaminants With Previous Negative
Regulatory Determinations
The Agency developed an additional step for the CCL 6 process to
further analyze a subset of the chemicals recommended for listing by
the evaluators that had previous negative regulatory determinations.
This was done to provide clarity regarding chemicals that have
previously received decisions not to regulate under SDWA as well as to
be consistent with the purpose of CCL as an iterative process that aims
to improve each time. The CCL 6 chemical evaluators recommended twelve
chemicals for listing that EPA had previously determined not to
regulate under the separate SDWA regulatory determination process,
which like CCL, occurs in 5-year cycles. For this subset of chemicals,
the EPA examined whether any new health and/or occurrence information
available since the time of the original determinations indicate the
contaminant is of greater public health concern now and could
potentially result in a different (i.e., positive) decision under a
future cycle of regulatory determination. For nine of these
contaminants the currently available data do not indicate a greater
public health concern at this time and these chemicals were
consequently removed from consideration for the draft CCL 6. A
description of the refinement can be found in Section 4.7 of the
Chemical Technical Support Document (USEPA, 2026a).
d. Chemical Groups on the Draft CCL 6
In addition to the 75 chemicals proposed for listing on the draft
CCL 6, the EPA proposes listing four chemical groups (disinfection
byproducts, microplastics, PFAS, and pharmaceuticals) (see Exhibit 1b).
These chemical groups have been identified as Agency priorities and
contaminants of concern for drinking water by public stakeholders and
under other EPA actions. Listing these four chemical groups on the
draft CCL 6 does not mean that the EPA will make subsequent regulatory
decisions for the entire group. The EPA will evaluate available
scientific data on the listed groups, subgroups, and individual
contaminants, as appropriate, included in the group to inform any
regulatory determinations for the group, subgroup, or individual
contaminants in the group.
i. Disinfection Byproducts
DBPs are formed when disinfectants, used for purposes of
antimicrobial treatment in drinking water, react with naturally
occurring or man-made materials in water. The EPA is proposing to list
DBPs as a group on the draft CCL 6, acknowledging this as an Agency
priority for drinking water. The DBP group includes 27 unregulated
DBPs, twenty-three of these were listed under the DBP chemical group
published under the CCL 5 process (87 FR 68060, USEPA, 2022a); the
other four unregulated DBPs (bromochloroacetonitrile, chloral hydrate,
chloronitramide anion, and trichloroacetonitrile) are being added to
the group based on consultation with the Agency microbial and
disinfection byproduct subject matter experts.
ii. Microplastics
The EPA acknowledges the concern for microplastics in sources of
drinking water and also received a public nomination for including
microplastics on CCL 6 that was accompanied by three data sources
(Miller et al., 2021; Ragusa et al., 2021; and Zarus et al., 2021), all
indicating potential concern for exposure to microplastics. In the
Science Advisory Board's
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recommendations for the draft CCL 5, the SAB also encouraged the EPA to
consider the assessment and inclusion of microplastics on future CCLs
(USEPA, 2022b). Therefore, the Agency is including microplastics as a
group on the draft CCL 6 as a first step toward defining and better
understanding potential public health risk from exposure via drinking
water.
As of the publication of the draft CCL 6, there remain significant
data gaps for microplastics that will require further research before
the Agency can fully understand the risks associated with microplastics
in drinking water. The known data gaps requiring further research
include (but are not limited to) the following:
1. A health-based definition: the need to determine the
characteristics of the microplastics (i.e., colors, polymers, shapes,
sizes, etc.) most associated with adverse health effects in humans from
exposure in drinking water.
2. Detection technology: the need for a validated analytical method
with the proper quality control data, accuracy, and precision that will
allow the EPA to be able to detect and analyze the concentrations of
microplastics occurring in drinking water reliably.
3. Microplastics combined with other substances: the need to better
understand how microplastics occurring in mixtures may impact detecting
specific microplastics and identifying their associated health risks.
4. Sources: the need to better understand all potential sources of
plastic pollution that contribute to the formation of microplastics in
sources of drinking water.
In summary, research is needed to determine the adverse health
effects from ingesting microplastics and to determine the
characteristics of the microplastics (i.e., size, type of plastic,
etc.) that are associated with the adverse health effects posing the
greatest potential health risk from exposure via drinking water. This
research will also assist in the development of robust and validated
analytical methods for microplastics in drinking water that may be used
to standardize data collection and analysis in the future.
iii. Per- and Polyfluoroalkyl Substances
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
(Cohen, 2020; USEPA, 2018). Over 4,000 PFAS have been manufactured and
used globally since the 1940s (USEPA, 2019), and data are scarce for
the majority of the PFAS, which would make evaluating PFAS individually
for the draft CCL 6 impractical. The Agency is proposing to list a PFAS
group to the draft CCL 6 inclusive of all PFAS that meet the structural
definition developed for the final CCL 5 (87 FR 68060, USEPA, 2022a),
excluding those that are subject to national drinking water regulations
at the time of publication of final CCL 6 (National Primary Drinking
Water Regulations, 40 CFR part 141 subpart Z--Control of Per- and
Polyfluoroalkyl Substances (PFAS), n.d.)). For the purposes of CCL, the
structural definition of PFAS remains the same as the definition
utilized in CCL 5 and 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; and
3. CF3C(CF3)RR', where all the carbons are saturated, and none
of the R groups can be hydrogen.
This proposal to list PFAS as a chemical group is responsive to
public nominations and is consistent with the approach taken for CCL 5
and is in keeping with the Agency's commitment to better understand and
ultimately reduce the potential risks caused by this broad class of
chemicals. Including the group of PFAS on the draft CCL 6 demonstrates
the Agency's commitment to prioritizing and building a strong
foundation of science on PFAS.
iv. Pharmaceuticals
For over a decade, public concern about the presence of
pharmaceutical substances in sources of drinking water has been a
recurring topic of discussion for the Agency's prioritization of
contaminants under SDWA. Since 2012, the EPA has led a Federal
workgroup on pharmaceuticals in water alongside USDA, FDA, and USGS to
exchange information on pharmaceuticals in the environment and to
support the coordination of joint studies.
The EPA committed to understanding contaminants in drinking water
and has identified pharmaceuticals as an Agency priority. This priority
is further reinforced by feedback received through the public
nominations process. For CCL 6, the Agency incorporated new data
sources (Schaider et al., 2014 and Battaglin et al., 2018) that
provided additional information about the occurrence of pharmaceutical
products in water; for health data on pharmaceuticals, the EPA added a
source used to help identify chemicals with estrogenic activity (USEPA,
2023b). The Agency also completed the Human Health Benchmarks for
Pharmaceuticals (HHB-Rx) in Drinking Water (visit the EPA website for
more information at https://www.epa.gov/sdwa/human-health-benchmarks).
Human health benchmarks are non-enforceable drinking water levels that
provide information about adverse health effects from drinking water
exposure to contaminants that have no drinking water standards or
health advisories. The benchmarks, based on potential health effects
from exposure via drinking water, informed the screening of
pharmaceuticals and identification of the top scoring pharmaceuticals.
Furthermore, the application of the benchmarks for pharmaceuticals in
the CCL screening process informed the EPA about the current research
needs for this broad class of chemicals.
The Agency is proposing the inclusion of a pharmaceuticals group on
the draft CCL 6 to further prioritize research and information needed
to identify which specific pharmaceuticals are occurring in drinking
water and may be of greatest public health concern. For the purposes of
the draft CCL 6, the EPA considers pharmaceuticals to include any
substances defined as a ``drug'' under the Federal Food, Drug, And
Cosmetic Act (1938).
B. Approach Used To Identify Microbial Candidates for the Draft CCL 6
1. Building the Microbial Universe
The EPA defines the CCL Microbial Universe as microbial
contaminants known to cause human disease. For CCL 6, the EPA conducted
a literature search for newly identified microbes and reviewed the
public nominations for additional pathogens to add to the CCL 6
Microbial Universe. The full CCL 6 Microbial Universe list is available
in Appendix B of the Microbial Technical Support Document (USEPA,
2026c).
2. Screening the Microbial Universe to a Preliminary Contaminant
Candidate List (PCCL 6)
The EPA uses screening criteria to narrow the Microbial Universe to
only those pathogens that have the potential to be transmitted through
drinking water. The pathogens that are not excluded by any of the
screening criteria are moved to the microbial PCCL 6. The screening
criteria restricts the microbial PCCL 6 to human pathogens that may
cause drinking water-related diseases resulting from ingestion,
inhalation, or dermal contact with drinking water. In
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addition, any pathogen documented to cause disease transmitted through
drinking water, regardless of the screening criteria, is also
considered for the PCCL.
After applying the screening criteria to the CCL 6 Microbial
Universe, 36 pathogens advanced to the PCCL 6. The screening criteria
and results of the screening process are discussed in greater detail in
Chapter 3 of the Microbial Technical Support Document (USEPA, 2026c).
3. Review of PCCL 6 Microbial Contaminants to Select a Draft CCL 6
Each pathogen on the PCCL 6 is evaluated for their occurrence in
water and their ability to produce adverse health effects in humans.
The EPA used a scoring system to assign a numerical value to each
pathogen on the PCCL 6. Each pathogen on the PCCL 6 was scored based
upon protocols developed to consider waterborne disease outbreaks,
occurrence, and health risks. For details on the three protocols used
to score the PCCL 6 microbial contaminants and the process by which the
scores are combined see Chapter 4 in the Microbial Support Document
(USEPA, 2026c).
a. Selection of the Draft CCL 6 Microbes
For CCL 6, the CCL selection process for listing placed emphasis on
the PCCL 6 microbial contaminants with confirmed (versus suspected)
outbreak(s) that have occurred in U.S. PWSs during the timeframe
evaluated for CCL 6. This approach to select contaminants for the CCL 6
prioritizes the pathogens that provide the best opportunities to
advance public health protection through potential regulation.
C. Summary of Nominated Candidates for the Draft CCL 6
The EPA sought public nominations in a Federal Register publication
on February 17, 2023 for chemicals, microbes, or other substances that
are not currently regulated to be considered for possible inclusion in
the CCL 6 (88 FR 10316, USEPA, 2023a).
The EPA received nominations for six chemicals and/or chemical
groups (lithium, manganese, microplastics, perchlorate, PFAS,
pharmaceutical waste (specifically estrogenic compounds)) and five
microbes and/or microbial groups (Legionella pneumophila, Listeria
monocytogenes, Nontuberculous Mycobacteria (NTM), pathogenic waterborne
mycobacteria group, Pseudomonas aeruginosa). All public nomination
letters and supporting information can be viewed in the EPA docket at
https://www.regulations.gov (Docket ID No. EPA-HQ-OW-2022-0946). A
detailed summary of the nomination process, including how each
nominated contaminant was considered for inclusion on the draft CCL 6,
is provided in Section 3.6 of the Chemical Technical Support Document
(USEPA, 2026a) and in Section 2.2 of the Microbial Technical Support
Document (USEPA, 2026c).
D. Data Needs for the Draft CCL 6
In previous CCLs, the SAB and other commenters have recommended
additional prioritization of contaminants to communicate research needs
and inform future regulatory decision-making. The EPA acknowledges that
multiple contaminants on the draft CCL 6 (and considered in the PCCL 6)
have 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 additional research and information needs, the EPA is
communicating to stakeholders both research priorities and gaps for
these contaminants. The EPA provides summary tables in Chapter 5 of the
Chemical Technical Support Document (USEPA, 2026a) and Chapter 6 in the
Microbial Technical Support Document (USEPA, 2026c) identifying
chemicals and microbial contaminants (respectively) categorized into
four groups depending upon the availability of occurrence data and
health assessments. This list is a starting point for identifying the
data needs of the CCL 6 contaminants.
IV. Request for Comments
The EPA is seeking comment and supporting data on the following:
A. The chemical and microbial contaminants selected for the draft
CCL 6.
B. The data sources the EPA obtained and evaluated for identifying
the CCL 6 Chemical Universe and the CCL 6 Microbial Universe, that are
provided in the Chemical Technical Support Document (USEPA, 2026a) and
Microbial Technical Support Document (USEPA, 2026c) located in the
docket for this document and also on the EPA's website for CCL 6
(https://www.epa.gov/ccl/draft-contaminant-candidate-list-6-ccl-6).
C. The process the EPA used to screen the CCL 6 Chemical Universe
and the CCL 6 Microbial Universe and develop the PCCL 6, that are
described in the Chemical Technical Support Document (USEPA, 2026a) and
Microbial Technical Support Document (USEPA, 2026c).
D. The process and supplemental data sources the EPA used for
classification to select individual chemicals and microbes for the CCL
6 from the PCCL 6, that are described in the Chemical Technical Support
Document (USEPA, 2026a) and Microbial Technical Support Document
(USEPA, 2026c).
E. The listing of the disinfection byproducts group on the draft
CCL 6.
F. The listing of the microplastics group on the draft CCL 6.
G. The listing of the PFAS group on the draft CCL 6.
H. The listing of the pharmaceuticals group on the draft CCL 6.
V. The EPA's Next Steps
The EPA will evaluate comments received during the public comment
period for this document. The EPA also plans to consult with the EPA's
SAB. The EPA will consider the public comments and the SAB input to
prepare the final CCL 6.
VI. References
Battaglin, W.A., Bradley, P.M., Iwanowicz, L., Journey, C.A., Walsh,
H.L. and Blazer, V.S. ``Pharmaceuticals, hormones, pesticides, and
other bioactive contaminants in water, sediment, and tissue from
Rocky Mountain National Park, 2012-2013.'' Science of the Total
Environment, Volume 643, 1 December 2018.
Cohen, A.D. ``Summit briefs policy-makers on drinking water
safety.'' American Association for the Advancement of Science--
Sciencemag.org, Volume 368 Issue 6489, 24 April 2020.
Federal Food, Drug, and Cosmetic Act. 21 U.S.C 321. 1938.
Miller E., Sedlak, M., Lin, D., Box, C., Holleman, C., Rochman,
C.M., and Sutton, R. ``Recommended best practices for collecting,
analyzing, and reporting microplastics in environmental media:
Lessons learned from comprehensive monitoring of San Francisco
Bay.'' Journal of Hazardous Materials, Volume 409, 5 May 2021.
National Primary Drinking Water Regulations. Subpart Z--Control of
Per- and Polyfluoroalkyl Substances (PFAS), 40 CFR 141.900 through
141.905. Available on the internet at: https://www.ecfr.gov/current/title-40/chapter-I/subchapter-D/part-141/subpart-Z.
Ragusa, A., Svelato, A., Criselda, S., Catalano, P., Notarstefano,
V., Carnevali, O., Papa, F., Rongioletti, M.C.A., Baiocco, F.,
Draghi, S., D'Amore, E., Rinaldo, D., Matta, M., and Giorgini, E.
``Plasticenta: First evidence of microplastics in human placenta.''
Environment International, Volume 146, January 2021.
Schaider, L.A., Rudel, R.A., Ackerman, J.M., Dunagan, S.C., and
Brody, J.G. ``Pharmaceuticals, perfluorosurfactants, and other
organic wastewater compounds in public drinking water wells in a
shallow sand and gravel
[[Page 17195]]
aquifer.'' Science of the Total Environment, Volumes 468-469, Pages
384-393, 15 January 2014.
USEPA. 2018. Basic Information on PFAS. Available at: https://www.epa.gov/pfas/basic-information-pfas.
USEPA. 2019. 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. 2022a. Drinking Water Contaminant Candidate List 5-Final.
Federal Register. Vol. 87, No. 218. P. 68060, November 14, 2022.
USEPA. 2022b. Review of the EPA's Draft Fifth Contaminant Candidate
List (CCL 5). EPA-SAB-22-007, August 19, 2022.
USEPA. 2023a. Drinking Water Contaminant Candidate List 6-
Nominations. Federal Register. Vol. 88, No. 33. P. 10316, February
17, 2023.
USEPA. 2023b. Endocrine Disruptor Screening Program (EDSP) Estrogen
Receptor Bioactivity. https://www.epa.gov/endocrine-disruption/endocrine-disruptor-screening-program-edsp-estrogen-receptor-bioactivity. Accessed June 2023.
USEPA. 2025. Announcement of Preliminary Regulatory Determinations
for Contaminants on the Fifth Drinking Water Contaminant Candidate
List. Federal Register Vol 90 Number 9 Page 3830. January 15, 2025.
USEPA. 2026a. Technical Support Document for the Draft Sixth
Contaminant Candidate List (CCL 6)--Chemical Contaminants. EPA 815-
R-26-004, February 2026.
USEPA. 2026b. Technical Support Document for the Draft Sixth
Contaminant Candidate List (CCL 6)--Contaminant Information Sheets.
EPA 815-R-26-005, February 2026.
USEPA. 2026c. Technical Support Document for the Draft Sixth
Contaminant Candidate List (CCL 6)--Microbial Contaminants. EPA 815-
R-26-006, February 2026.
Zarus, G.M., Muianga, C., Hunter, C.M., and Pappas, R.S. ``A Review
of Data for Quantifying Human Exposures to Micro and Nanoplastics
and Potential Health Risks.'' Science of the Total Environment,
Volume 756, 20 February 2021.
Jessica L. Kramer,
Assistant Administrator.
[FR Doc. 2026-06662 Filed 4-3-26; 8:45 am]
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