Draft Sixth Contaminant Candidate List for Drinking Water Regulation

Content

ACTION:

Notice of availability; request for comments.

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: lombardi.thomas@epa.gov; 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

  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

  75 chemicals, four chemical groups, and nine microbes.

BILLING CODE 6560-50-P

BILLING CODE 6560-50-C

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

  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

BILLING CODE 6560-50-P

BILLING CODE 6560-50-C 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

  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

  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

  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.

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Jessica L. Kramer, Assistant Administrator. [FR Doc. 2026-06662 Filed 4-3-26; 8:45 am] BILLING CODE 6560-50-P

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