EPA’s PFAS Drinking Water Regulation: Considerations for Congress

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EPA’s PFAS Drinking Water Regulation:

Considerations for Congress

June 23, 2026

Congressional Research Service

https://crsreports.congress.gov

R49007

SUMMARY

EPA’s PFAS Drinking Water Regulation:

Considerations for Congress

Per- and polyfluoroalkyl substances (PFAS) are a large, diverse group of fluorinated chemicals

that have been used in an array of commercial, industrial, and U.S. military applications for

decades. Some of the more common applications include nonstick coatings, food wrappers,

waterproof materials, and fire suppressants. Detections of PFAS in public water supplies have

heightened public and congressional interest in the U.S. Environmental Protection Agency’s

(EPA’s) authorities under the Safe Drinking Water Act (SDWA) to limit PFAS in drinking water.

SDWA authorizes EPA to promulgate regulations with enforceable limits for contaminants.

R49007

June 23, 2026

Elena H. Humphreys

Specialist in Environmental

Policy

As amended in 1996, SDWA outlines a stepwise process for EPA to follow when establishing drinking water regulations.

The evaluation process includes identifying contaminants of potential concern, assessing health risks, collecting occurrence

data (and developing reliable analytical methods necessary to do so), and making determinations as to whether or not a

regulation is warranted for a contaminant. For EPA to make a determination—a “positive regulatory determination (RD)”—

that regulation of a contaminant is warranted, SDWA directs EPA to find (1) the contaminant may have an adverse health

effect; (2) the contaminant is known to occur—or there is a substantial likelihood that it will occur—in water systems at a

frequency and at levels of public health concern; and (3) in the sole judgment of the EPA Administrator, regulation of the

contaminant presents a meaningful opportunity for reducing health risks.

In March 2021, EPA finalized a positive RD for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). On

March 14, 2023, EPA proposed a National Primary Drinking Water Regulation (NPDWR) for PFOA and PFOS. At the same

time, the agency proposed a positive RD for perfluorohexane sulfonic acid (PFHxS), perfluorobutane sulfonic acid (PFBS),

hexafluoropropylene oxide dimer acid (HFPO-DA) and its ammonium salt (together known as “GenX chemicals”), and

perfluorononanoic acid (PFNA) and proposed that the NPDWR also include these four PFAS. By taking two steps

simultaneously (proposing an RD while also proposing regulation), EPA effectively expedited the SDWA regulatory process

for the latter chemicals.

In April 2024, EPA finalized the PFAS National Primary Drinking Water Regulation (PFAS NPDWR), a regulation with

enforceable drinking water standards (i.e., maximum contaminant levels [MCLs]) for the following PFAS: perfluorooctanoic

acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorohexane sulfonic acid (PFHxS), hexafluoropropylene oxide dimer

acid (HFPO-DA) and its ammonium salt (together known as “GenX chemicals”), and perfluorononanoic acid (PFNA). As

part of the regulation, EPA also generated a “hazard index” of PFHxS, PFNA, GenX chemicals, and perfluorobutane sulfonic

acid (PFBS). A hazard index accounts for the potential health effects of mixtures of substances by summing their

concentrations relative to their associated health-based value. The hazard index is used as the MCL for the mixture of these

substances. EPA set the regulation’s effective date for the PFAS MCLs to April 2029.

EPA’s 2024 NPDWR establishes MCLs of 4.0 parts per trillion (ppt) for each of PFOA and PFOS. For PFHxS, PFNA, and

GenX chemicals, the regulation establishes MCLs of 10 ppt for each substance. For the hazard index, EPA’s regulation

requires water systems to assess concentrations of PFHxS, PFNA, and GenX chemicals relative to their respective MCLs, to

assess the concentration of PFBS relative to its health-based water concentration of 2,000 ppt, and to determine that their

average concentration is within the value specified by the hazard index. As such, the regulation does not regulate PFBS

individually, but only when combined with at least one other PFAS.

EPA’s promulgation of this regulation has garnered congressional and stakeholder attention. In 2024, Congress directed the

U.S. Government Accountability Office to review the cost estimates supporting the rule. Three entities filed petitions for

review of the PFAS regulation in the U.S. Court of Appeals for the D.C. Circuit. In May 2026, EPA announced proposed

regulations to rescind parts of the 2024 PFAS regulation based on procedural grounds and to delay the rule’s effective date

for an additional two years (i.e., compliance would be required by 2031). These proposals, as well as the ongoing petitions,

have created uncertainty for water systems about which elements of the drinking water regulation, if any, they will have to

comply with by April 2029.

EPA’s PFAS actions raise several considerations. These include those related to SDWA’s regulatory development process,

EPA’s 2026 proposals, and state actions to address PFAS. Congressional considerations may include how to assist systems

with compliance or more broadly address EPA’s implementation of SDWA’s regulatory development process.

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EPA’s PFAS Drinking Water Regulation: Considerations for Congress

Contents

Introduction ..................................................................................................................................... 1

Safe Drinking Water Act (SDWA) ................................................................................................... 2

SDWA Regulations.................................................................................................................... 2

SDWA Enforcement .................................................................................................................. 3

SDWA’s Regulatory Development Process ............................................................................... 4

Regulated Water Systems .......................................................................................................... 4

Evaluating PFAS Under SDWA ...................................................................................................... 6

2023 Preliminary Determination for PFHxS, PFNA, GenX Chemicals, and PFBS ................. 8

2023 Proposed Regulation ...................................................................................................... 10

PFOA and PFOS ............................................................................................................... 10

PFHxS, PFNA, GenX Chemicals, and PFBS Hazard Index ............................................. 10

Proposed Treatment Technologies and Options ................................................................ 10

2024 Final Determinations for PFHxS, PFNA, and GenX Chemicals ....................................11

2024 PFAS Regulation .............................................................................................................11

2026 Proposed Regulations ......................................................................................................11

2026 Proposed Rescission of the RD for PFHxS, PFNA, and GenX Chemicals,

and Associated Regulation ............................................................................................. 12

2026 Proposed “National Exemption” .............................................................................. 12

Considerations for Congress.......................................................................................................... 14

Compliance with SDWA Regulatory Development Process ................................................... 15

Rescinding a Final RD ............................................................................................................ 17

Implementing EPA’s Proposal for Exemptions ....................................................................... 18

When Can an Exemption Be Provided? ............................................................................ 18

State Primacy for the PFAS Regulation ............................................................................ 18

States’ Adoption of PFAS Regulation ..................................................................................... 19

Petitions for Review ................................................................................................................ 19

Compliance Assistance............................................................................................................ 20

System Support Considerations ........................................................................................ 21

Figures

Figure 1. Timeline of Selected Drinking-Water-Related PFAS Actions.......................................... 8

Contacts

Author Information........................................................................................................................ 22

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EPA’s PFAS Drinking Water Regulation: Considerations for Congress

Introduction

Per- and polyfluoroalkyl substances (PFAS) are a large, diverse group of fluorinated chemicals

that have been used in an array of commercial, industrial, and U.S. military applications for

decades. Some of the more common applications include nonstick coatings, food wrappers,

waterproof materials, and fire suppressants. Detections of PFAS in public water supplies have

heightened public and congressional interest in the U.S. Environmental Protection Agency’s

(EPA’s) authorities under the Safe Drinking Water Act (SDWA) to limit PFAS in drinking water.

SDWA authorizes EPA to promulgate regulations with enforceable limits for contaminants,

including PFAS.

In April 2024, EPA finalized the PFAS National Primary Drinking Water Regulation (PFAS

NPDWR), a regulation with enforceable drinking water standards for the following PFAS:

•

perfluorooctanoic acid (PFOA),

perfluorooctane sulfonate (PFOS),

perfluorohexane sulfonic acid (PFHxS),

hexafluoropropylene oxide dimer acid (HFPO-DA) and its ammonium salt

(together known as “GenX chemicals”), and

perfluorononanoic acid (PFNA).

As part of the 2024 PFAS regulation, EPA generated a “hazard index” of PFHxS, PFNA, GenX

chemicals, and perfluorobutane sulfonic acid (PFBS).1 A hazard index accounts for the potential

health effects of mixtures of substances by summing their concentrations relative to their

associated health-based value. The hazard index is used as the enforceable standard for the

mixture of these substances. The regulation’s compliance date for the PFAS drinking water

standards is April 2029.

EPA’s promulgation of the PFAS NPDWR has garnered congressional and stakeholder attention.2

Some stakeholders have raised concerns over the sequence of EPA’s actions to develop the 2024

PFAS regulation. SDWA outlines a process for EPA to follow while evaluating contaminants for

potential regulation and for proposing and finalizing a regulation. Some assert that EPA did not

follow SDWA’s regulatory development process and question EPA’s approach to regulating

mixtures of these substances through the hazard index.3 Three entities filed petitions for review of

the 2024 PFAS regulation in the U.S. Court of Appeals for the D.C. Circuit.4

1 U.S. Environmental Protection Agency (EPA), “PFAS National Primary Drinking Water Regulation,” 89 Federal

2 For example, in the joint explanatory statement accompanying the Consolidated Appropriations Act, 2024, P.L. 11842, Congress directed the U.S. Government Accountability Office (GAO) to review the cost estimates supporting the

rule. GAO published a report stating that “because this issue is the subject of ongoing litigation, our work focused on

whether EPA sought and published public comment on various elements of the analysis of costs, as required by

SDWA.” GAO identified that EPA did seek and published public comment on the cost estimate of the 2024 PFAS

regulation. GAO, Persistent Chemicals: Information on EPA’s Analysis of Costs for its PFAS Drinking Water

Regulation, 25-107897, July 30, 2025, https://www.gao.gov/assets/gao-25-107897.pdf.

3 See, for example, American Water Works Association, “AWWA and AMWA Petition Frequently Asked Questions,”

June 7, 2024, https://www.awwa.org/AWWA-Articles/awwa-and-amwa-petition-frequently-asked-questions/.

4 Petition for Review, American Water Works Association v. EPA, No. 24-1188 (D.C. Cir. filed June 7, 2024); Petition

for Review, National Association of Manufacturers v. EPA, No. 24-1191 (D.C. Cir. filed June 10, 2024); Petition for

Review, The Chemours Company v. EPA, No. 24-1192 (D.C. Cir. filed June 10, 2024).

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EPA’s PFAS Drinking Water Regulation: Considerations for Congress

In May 2026, EPA proposed two regulations: one that would rescind the regulatory

determinations (RDs) for PFHxS, PFNA, and GenX chemicals, and parts of the 2024 PFAS

regulation; and one that would delay the 2024 PFAS regulation’s effective date for two years (i.e.,

compliance would be required by 2031).5 These proposals, as well as the ongoing petitions, have

created uncertainty for water systems about which elements of the drinking water regulation, if

any, they will have to comply with by the April 2029 compliance date.

This report outlines SDWA’s regulatory development process and provides an overview of EPA’s

implementation of these authorities regarding PFAS. The report then provides considerations for

Congress regarding EPA’s PFAS actions, as well as considerations related to assistance with

regulatory compliance.

This report focuses on the regulation and its requirements for water systems.

Safe Drinking Water Act (SDWA)

As amended in 1996, SDWA outlines a stepwise process for EPA to follow when establishing

drinking water regulations.6 The evaluation process includes identifying contaminants of potential

concern, assessing health risks, collecting occurrence data (and developing reliable analytical

methods necessary to do so), and making determinations as to whether or not a regulation is

warranted for a contaminant.

For EPA to make a determination that regulation of a contaminant is warranted, SDWA directs

EPA to find (1) the contaminant may have an adverse health effect; (2) the contaminant is known

to occur—or there is a substantial likelihood it will occur—in water systems at a frequency and at

levels of public health concern; and (3) in the sole judgment of the EPA Administrator, regulation

of the contaminant presents a meaningful opportunity for reducing health risks. SDWA directs

EPA to seek public comment on a preliminary or proposed positive RD before finalizing the

determination.7 SDWA does not require EPA to finalize an RD within a specific time frame.

SDWA Regulations

SDWA prescribes maximum time frames for EPA to promulgate a regulation once EPA has made

a positive RD. EPA is to propose a rule within 24 months of a positive RD and to promulgate a

final drinking water regulation within 18 months after the proposal.8 SDWA also allows EPA to

propose a drinking water regulation concurrent with the determination to regulate.9 Regulations

generally take effect three years after promulgation.10 EPA (or a state in the case of an individual

system) may allow up to two additional years if capital improvements are needed.11

5 EPA, “Extending the Compliance Deadline for the PFOA and PFOS Maximum Contaminant Levels,” 91 Federal

Provisions for Four PFAS Substances (PFHxS, PFNA, HFPO-DA (GenX), and the Mixture of These Three PFAS Plus

PFBS),” 91 Federal Register 29413-29425, May 20, 2026.

6 Safe Drinking Water Act (SDWA) §1412(b); 42 U.S.C. §300g-1(b). For more information about the Safe Drinking

Water Act’s (SDWA’s) regulatory development provisions, see CRS Report R46652, Regulating Contaminants Under

the Safe Drinking Water Act (SDWA), by Elena H. Humphreys.

7 SDWA §1412(b)(1)(B)(ii); 42 U.S.C. §300g-1(b)(1)(B)(ii).

8 SDWA §1412(b)(1)(E); 42 U.S.C. §300g-1(b)(1)(E).

SDWA §1412(b)(1)(E); 42 U.S.C. §300g-1(b)(1)(E).

10 SDWA §1412(b)(10); 42 U.S.C. §300g-1(b)(10).

11 SDWA §1412(b)(10); 42 U.S.C. §300g-1(b)(10).

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EPA’s PFAS Drinking Water Regulation: Considerations for Congress

For each contaminant covered by the regulation, EPA is to establish a maximum contaminant

level goal (MCLG) at a level at which no known or anticipated adverse health effects occur and

that allows an adequate margin of safety.12 Regulations also are to include a maximum

contaminant level (MCL)—an enforceable limit for a contaminant in public water supplies.13

SDWA requires EPA to set the MCL as close to the MCLG as feasible.14 Concurrent with

proposing a regulation, SDWA requires EPA to publish and seek public comment on a “health risk

reduction and cost analysis” (HRRCA) for each contaminant covered by the proposed

regulation.15 In addition, SDWA requires EPA to make a determination of whether the benefits of

the MCL justify, or do not justify, the costs based on the HRRCA when proposing the

regulation.16

For each drinking water regulation, SDWA requires EPA to identify a list of best available

technologies, treatment techniques, and other means that EPA finds feasible for meeting the

MCL. SDWA requires EPA to identify treatment technologies that achieve the MCL and are

“affordable” for small systems.17 Each regulation also is to establish monitoring and reporting

requirements.

SDWA Enforcement

SDWA authorizes states, territories, and Indian tribes to assume primary oversight and

enforcement responsibility (primacy) for public water systems when EPA determines that

statutory criteria are met.18 Currently, 55 of 57 states and territories have SDWA primacy.19 To

assume primacy, a state20 must adopt regulations at least as stringent as federal requirements,

develop adequate procedures for enforcement (including conducting monitoring and inspections),

adopt authority for administrative penalties, conduct inventories of water systems, maintain

records and compliance data, and make reports as EPA may require.

Among other provisions, SDWA authorizes states to grant public water systems temporary

exemptions from standards or treatment techniques if a system cannot comply for other

compelling reasons (including costs).21 An exemption is limited to situations where the exemption

12 SDWA §1412(b)(4)(A); 42 U.S.C. §300g-1(b)(4)(A).

13 SDWA §1412(b)(4)(B); 42 U.S.C. §300g-1(b)(4)(B). SDWA authorizes EPA to establish a treatment technique in

lieu of a maximum contaminant level (MCL) if an MCL is not feasible.

14 SDWA §1412(b)(4)(B); 42 U.S.C. §300g-1(b)(4)(B). If the treatment of a contaminant is not feasible—

technologically or economically—EPA may establish a treatment technique in lieu of an MCL (SDWA

§1412(b)(7)(A); 42 U.S.C. §300g-1(b)(7)(A)). When assessing feasibility, the law directs EPA to consider the best

available (and field-demonstrated) treatment technologies, taking cost into consideration (SDWA §1412(b)(4)(D); 42

U.S.C. §300g-1(b)(4)(D)).

15 SDWA §1412(b)(6)(C); 42 U.S.C. §300g-1(b)(6)(C).

16 SDWA §1412(b)(4)(C); 42 U.S.C. §300g-1(b)(4)(C).

17 SDWA §1412(b)(4)(E)(ii); 42 U.S.C. §300g-1(b)(4)(E)(ii). EPA considers treatment for a regulation affordable if the

costs do not exceed of 2.5% of median household income.

18 SDWA §1413; 42 U.S.C. §300g-2. SDWA Section 1401(13)(A) defines state to include the states and, for most

purposes, “the District of Columbia, Guam, the Commonwealth of Puerto Rico, the Northern Mariana Islands, the

[U.S.] Virgin Islands, American Samoa, and the Trust Territory of the Pacific Islands.” Section 1401(B) provides that

for purposes of Section 1452 (State Revolving Loan Funds), state means “each of the 50 States, the District of

Columbia, and the Commonwealth of Puerto Rico.” Tribes are defined separately at Section 1401(14).

19 All states (except Wyoming and the District of Columbia), territories, and Navajo Nation have primacy. EPA

oversees water systems in nonprimacy areas and retains oversight of primacy states.

20 Section 1451 (42 U.S.C. §300j-11) generally authorizes the EPA Administrator to treat Indian tribes as states under

SDWA.

21 SDWA §1416; 42 U.S.C. §300g-5.

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EPA’s PFAS Drinking Water Regulation: Considerations for Congress

would not result in an unreasonable health risk. States can issue exemptions to a qualified system

for up to three years beyond the regulation’s effective date. This authority is available to EPA for

Wyoming and the District of Columbia, which do not have SDWA primacy. Systems serving

3,300 or fewer persons may receive a maximum of three additional two-year extensions for a total

exemption duration of nine years.

SDWA’s Regulatory Development Process

SDWA’s regulatory development provisions support a science-based and risk-driven process to

regulate harmful contaminants in drinking water. SDWA outlines a specific process for EPA to

follow when evaluating contaminants to achieve an outcome (i.e., the regulation of harmful

contaminants). The act requires EPA to be transparent regarding the data the agency uses to

determine that the regulation of a contaminant will result in a meaningful health risk reduction for

those served by public water systems. Through the HRRCA, EPA is required to build a record to

inform the public about the risk a contaminant poses as well as the anticipated costs to regulate

it.22 To this end, the act requires EPA to use the best available peer-reviewed information. It

requires EPA to solicit comments from the Science Advisory Board,23 consult with the National

Drinking Water Advisory Council, and provide an opportunity for public comment.24 These

requirements are intended to create a transparent process demonstrating that EPA’s drinking water

regulations are derived from the best available science and that the regulatory costs are weighed

against the health risk reduction benefits.25 SDWA outlines a procedure for entities to file a

petition for review of EPA’s actions pertaining to the establishment of a NPDWR within 45 days

of promulgation.26

Once EPA finalizes a regulation, SDWA provides some degree of certainty for water systems,

because the act states that a revision of a drinking water regulation must maintain or provide for

greater public health protection.27 This provision does not, however, specify that EPA may revise

an MCL only to be more stringent; it may be revised to be less stringent if new “science” finds

that a less stringent standard would be as protective of public health.28

Regulated Water Systems

SDWA applies to public water systems. A public water system is defined as any water system that

provides water to at least 25 individuals or 15 service connections. Roughly 144,000 public water

systems operate in the United States.29

22 U.S. Congress, Senate Environment and Public Works Committee, Safe Drinking Water Amendments Act of 1995,

report to accompany S. 1316, 104th Cong., 1st sess., November 7, 1995, S.Rept. 104-169. In this report, Congress

identifies several goals for its legislation, including that “a public record must be created to educate people about the

risks they face from a particular contaminant and the costs to regulate it.”

23 The 1978 Environmental Research, Development, and Demonstration Authorization Act (P.L. 95-477) directed EPA

to establish the Science Advisory Board to provide scientific advice to the Administrator (42 U.S.C. §4365).

24 SDWA §1412(d); 42 U.S.C. §300g-1(d).

25 S.Rept. 104-169.

26 SDWA §1448; 42 U.S.C. §300j-7.

27 SDWA §1412(b)(9); 42 U.S.C. §300g-1(b)(9). This provision specifies that “any revision shall maintain, or provide

for greater, protection of the health of persons.”

28 S.Rept. 104-169.

29 Water system estimates from EPA’s Safe Drinking Water Information Systems, Water System Summary report,

https://sdwis.epa.gov/ords/sfdw_pub/r/sfdw/sdwis_fed_reports_public/1?clear=1, generated on March 25, 2026. The

search parameters were “public water systems.”

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EPA’s PFAS Drinking Water Regulation: Considerations for Congress

Of these public water systems, nearly 50,000 are community water systems, which serve the same

individuals year-round.30 Roughly 17,000 are non-transient non-community water systems, which

generally serve the same individuals for more than six months but not year-round, such as

systems at schools or factories.31 Another 77,600 public water systems are transient noncommunity water systems, which generally do not serve the same individuals for more than six

months in a year; examples include systems at campgrounds and gas stations that provide water

to transitory customers.32

The full suite of SDWA regulations applies to community water systems. Most drinking water

regulations, including the PFAS regulation, apply to non-transient non-community water systems.

The PFAS regulation does not apply to transient non-community water systems; EPA’s longstanding policy is to exclude transient systems from drinking water regulations except for those

that regulate contaminants that have the potential to cause immediate adverse human health

effects resulting from short-term exposure.33 Transient systems are therefore not a focus of this

report.

The source, size, and capacity of water systems vary.34 For example, some systems may provide

their customers with treated water sourced from a well, whereas others may draw from multiple

water sources.

The majority of water systems serve a relatively small number of customers. Roughly 80% of

community water systems serve 3,300 or fewer individuals.35 Among non-transient noncommunity water systems, roughly 99% serve populations of 3,300 or fewer.36 Water systems that

serve 100,000 or more individuals make up less than 1% of the total number of community water

systems, but serve roughly 46% of those served by such systems.37

The majority (roughly 87%) of systems covered by the PFAS regulation serve fewer than 3,300

people.38 Systems that serve fewer than 3,300 individuals typically rely on groundwater as the

30 Community water system estimates from EPA’s Safe Drinking Water Information Systems, Water System Summary

report, https://sdwis.epa.gov/ords/sfdw_pub/r/sfdw/sdwis_fed_reports_public/1?clear=1, generated on March 25, 2026.

The search parameters were “community water systems.”

31 Non-transient non-community water system estimates from EPA’s Safe Drinking Water Information Systems, Water

System Summary report, https://sdwis.epa.gov/ords/sfdw_pub/r/sfdw/sdwis_fed_reports_public/1?clear=1, generated

on March 25, 2026. The search parameters were “non-transient non-community water systems.”

32 EPA, “Information about Public Water Systems,” https://www.epa.gov/dwreginfo/information-about-public-watersystems.

33 See for example, EPA, Introduction to the Public Water System Supervision Program, January 2003,

http://cfpub.epa.gov/watertrain/pdf/modules/pwss.pdf.

34 EPA, “Learn About Capacity Development,” https://www.epa.gov/dwcapacity/learn-about-capacity-development.

35 Community water system estimates from EPA’s Safe Drinking Water Information Systems, Water System Summary

report, https://sdwis.epa.gov/ords/sfdw_pub/r/sfdw/sdwis_fed_reports_public/1?clear=1, generated on March 25, 2026.

The search parameters were “community water systems.”

36 Non-transient non-community water system estimates from EPA’s Safe Drinking Water Information Systems, Water

System Summary report, https://sdwis.epa.gov/ords/sfdw_pub/r/sfdw/sdwis_fed_reports_public/1?clear=1, generated

on March 25, 2026. The search parameters were “non-transient non-community water systems.”

37 Water system estimates from EPA’s Safe Drinking Water Information Systems, Water System Summary report,

https://sdwis.epa.gov/ords/sfdw_pub/r/sfdw/sdwis_fed_reports_public/1?clear=1, generated on March 25, 2026. The

search parameters were “community water systems” and “non-transient non-community water systems.” Only one nontransient non-community water system serves more than 100,000 individuals.

38 Water system estimates from EPA’s Safe Drinking Water Information Systems, Water System Summary report,

https://sdwis.epa.gov/ords/sfdw_pub/r/sfdw/sdwis_fed_reports_public/1?clear=1, generated on March 25, 2026. The

search parameters were “community water systems” and “non-transient non-community water systems.”

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EPA’s PFAS Drinking Water Regulation: Considerations for Congress

source of their drinking water, whereas larger systems are more likely to use surface water.39

Groundwater is generally less likely to be contaminated than surface water, but when

groundwater is contaminated, its level of contamination may be higher given that it moves as a

plume (a segment of groundwater that contains contaminants released from a point source),40

rather than mixing with other water (e.g., rain) or evaporating through the air.41

Water system size also drives another difference among systems: the extent to which systems

benefit from economies of scale. Larger systems have a larger base of customers from which to

pay for infrastructure upgrades, employ advanced treatment technologies, and monitor for

regulatory compliance.

Evaluating PFAS Under SDWA

EPA finalized the PFAS NPDWR on April 26, 2024.42 The promulgation of this regulation is one

step in SDWA’s regulatory development process. This section provides an overview of EPA’s

SDWA actions to develop a PFAS regulation.43 See Figure 1 for a timeline of selected EPA

actions under SDWA to address PFAS and associated legislation.

Since at least 2009, EPA had been evaluating certain PFAS for potential regulation. SDWA’s

regulatory process involves identifying contaminants that may warrant regulation on a list called

the contaminant candidate list (CCL). EPA develops the CCL and uses it to collect information,

such as health effects information, on contaminants that are a priority for regulatory

consideration.44 EPA has published five CCLs since 1998. In 2009, EPA listed PFOA and PFOS

on the third CCL.45 Instead of adding each PFAS separately, the fifth CCL, finalized in 2022,

added PFAS as group.46

To generate national-level occurrence data for a contaminant, SDWA authorizes EPA to

promulgate a rule requiring water systems to monitor for up to 30 unregulated contaminants.47 All

water systems serving more than 10,000 individuals and a nationally representative sample of

public water systems serving 10,000 individuals or fewer are required to conduct monitoring.48

39 S.Rept. 104-169.

40 EPA, Evaluating Ground Water Plumes Under the Hazard Ranking System, Washington, DC, September 1998,

https://semspub.epa.gov/work/11/174007.pdf.

41 S.Rept. 104-169.

42 EPA, “PFAS National Primary Drinking Water Regulation,” 89 Federal Register 32532-32757, April 26, 2024.

43 For more information about EPA’s evaluation of PFAS under SDWA before 2021, see CRS Report R45793, PFAS

and Drinking Water: Selected EPA and Congressional Actions, by Elena H. Humphreys.

44 EPA, “PFAS National Primary Drinking Water Regulation Rulemaking,” 88 Federal Register 18638-18754, March

29, 2023.

45 EPA, “Drinking Water Contaminant Candidate List 3—Final,” 74 Federal Register 51850, October 8, 2009. For

more information on CCL 3, see EPA, “Contaminant Candidate List 3—CCL 3,” https://www.epa.gov/ccl/

contaminant-candidate-list-3-ccl-3.

46 EPA, “Drinking Water Contaminant Candidate List 5—Final,” 87 Federal Register 68060-68085, November 14,

2022.

47 SDWA §1445(a)(2); 42 U.S.C. §300j-4(a)(2). For more information, see EPA, “Monitoring Unregulated

Contaminants in Drinking Water,” March 16, 2026, http://water.epa.gov/lawsregs/rulesregs/sdwa/ucmr/.

48 Section 2021(a) of America’s Water Infrastructure Act of 2018 (AWIA) added SDWA Section 1445(j) to expand

unregulated contaminant monitoring requirements to include public water systems serving 3,300-10,000 individuals—

subject to the availability of appropriations for this purpose and lab capacity. The monitoring requirements entered into

effect three years after the enactment date of AWIA (i.e., they were effective October 23, 2021). Section 1445(j)

authorized $15.0 million to be appropriated for each year from FY2019 through FY2021 to support the expanded

monitoring.

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EPA’s PFAS Drinking Water Regulation: Considerations for Congress

EPA calls this rule the “unregulated contaminant monitoring rule” (UCMR). Using the data it

collects through the UCMR, EPA estimates the nationwide frequency and level of occurrence of

contaminants, such as PFAS, in water systems. EPA generally selects the list of unregulated

contaminants for the UCMR based on the CCLs. In the third UCMR (UCMR 3), EPA required

systems to monitor for perfluoroheptanoic acid (PFHpA), PFOA, PFOS, PFBS, PFHxS, and

PFNA between 2013 and 2015.49 Using health effects information and the nationwide occurrence

data from UCMR 3, EPA made a preliminary determination to regulate PFOA and PFOS in 2020

and solicited public comment; EPA finalized the positive RD for these contaminants in 2021.50

The National Defense Authorization Act for Fiscal Year 2020 (P.L. 116-92), Section 7311,

required EPA to add to the fifth UCMR (UCMR 5) all PFAS or categories of PFAS with validated

test methods. In 2021, EPA issued UCMR 5, which required water systems to monitor for PFOA,

PFOS, GenX chemicals, PFHxS, PFNA, PFBS, and 19 other PFAS, between 2023 and 2025.51

For UCMR 5, EPA required systems to use analytical methods that had been developed or revised

since UCMR 3, and allowed for the detection of PFAS in treated water at levels lower than were

achievable under UCMR 3.52

As discussed above, SDWA directs EPA to propose a regulation within 24 months of a positive

RD. In March 2023, EPA proposed a regulation for PFOA and PFOS; issued preliminary

determinations to regulate PFBS, PFHxS, PFNA, and GenX chemicals; and proposed that the

regulation for PFOA and PFOS also cover these four PFAS.53 In April 2024, EPA finalized the

positive RD for PFHxS, PFNA, and GenX chemicals, did not finalize the determination to

regulate PFBS individually, and finalized the regulation covering PFOA and PFOS.54 EPA also

finalized the regulation for PFHxS, PFNA, and GenX chemicals, and a mixture of these

substances and PFBS.55

49 EPA, “Revisions to the Unregulated Contaminant Monitoring Regulation (UCMR 3) for Public Water Systems,” 77

Federal Register 26072, May 2, 2012.

50 EPA, “Announcement of Preliminary Regulatory Determinations for Contaminants on the Fourth Drinking Water

Contaminant Candidate List,” 85 Federal Register 14098-14142, March 10, 2020; EPA, “Announcement of Final

Regulatory Determinations for Contaminants on the Fourth Drinking Water Contaminant Candidate List,” 86 Federal

51 EPA, “Revisions to the Unregulated Contaminant Monitoring Rule (UCMR 5) for Public Water Systems and

Announcement of Public Meetings,” 86 Federal Register 73131, December 27, 2021.

52 These updated methods allowed for minimum reporting levels for PFOA and PFOS each at 4 parts per trillion (ppt),

GenX chemicals at 5 ppt, PFHxS at 3 ppt, PFNA at 4 ppt, and PFBS at 3 ppt.

53 EPA, “PFAS National Primary Drinking Water Regulation Rulemaking,” 88 Federal Register 18638-18754, March

29, 2023.

54 EPA, “PFAS National Primary Drinking Water Regulation,” 89 Federal Register 32532-32757, April 26, 2024.

55 EPA, “PFAS National Primary Drinking Water Regulation,” 89 Federal Register 32532-32757, April 26, 2024.

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Figure 1. Timeline of Selected Drinking-Water-Related PFAS Actions

Source: Compiled by CRS from Federal Register notices, EPA press releases, and Congress.gov.

2023 Preliminary Determination for PFHxS, PFNA, GenX

Chemicals, and PFBS

To propose a positive RD for PFNA, PFHxS, GenX chemicals, and PFBS, EPA had to (1)

determine that these chemicals have an adverse health effect; (2) find that they occur—or that

there is a substantial likelihood that they occur—in water systems at a frequency and at levels of

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concern; and (3) determine that the regulation of these substances presents a meaningful

opportunity for health risk reduction.56

To characterize the health effects associated with PFHxS and PFNA, EPA relied on a

toxicological profile of perfluoroalkyls developed by the Agency for Toxic Substances and

Disease Registry (ATSDR).57 EPA used ATDSR’s data to identify associations between PFHxS

and thyroid effects and between PFNA and developmental effects.58 For PFBS and GenX

chemicals, EPA used toxicity assessments it developed to identify associations between PFBS and

developmental, thyroid, and kidney effects, and between GenX chemicals and liver, kidney,

immune system, blood, reproductive, and developmental effects.59 In addition, EPA stated that the

mixture of these PFAS contaminants, given their similar observed health effects, is assumed to act

in a “dose additive” manner, meaning that when found together, they should be assumed to act as

an aggregate concentration.60 EPA stated that it used these data to make a preliminary

determination that these PFAS meet the first statutory criterion for regulation, which is that they

have an adverse health effect.61

Regarding occurrence, EPA determined that there is a substantial likelihood that PFBS, PFNA,

Gen X chemicals, and PFHxS occur at levels of concern in water systems.62 To identify

occurrence, EPA used data collected from UCMR 3 for PFNA, PFBS, and PFHxS (GenX

chemicals were not included in UCMR 3) as well as drinking water quality data from a subset of

states that had tested for PFAS (including GenX chemicals).63 After reviewing the available data,

the agency made a preliminary determination that these PFAS met the second statutory criterion

of occurring at levels of concern within water systems.

Using both the adverse health effects data and occurrence data, EPA proposed that PFHxS,

PFNA, GenX, and PFBS warranted regulation both individually and as a mixture, meaning that

the Administrator preliminarily determined that the regulation of these contaminants would

present a meaningful opportunity for health risk reduction.64

56 SDWA §1412(b)(1)(B)(ii); 42 U.S.C. §300g-1(b)(1)(B)(ii).

57 U.S. Agency for Toxic Substances and Disease Registry, Toxicological Profile for Perfluoroalkyls, CS274127-A,

May 2021, https://www.atsdr.cdc.gov/ToxProfiles/tp200.pdf.

58 EPA, “PFAS National Primary Drinking Water Regulation Rulemaking,” 88 Federal Register 18638-18754, March

29, 2023.

59 EPA, Human Health Toxicity Values for Hexafluoropropylene Oxide (HFPO) Dimer Acid and Its Ammonium Salt

(CASRN 13252-13-6 and CASRN 62037-80-3), Also Known as “GenX Chemicals,” 822R-21-010, October 2021,

https://www.epa.gov/system/files/documents/2021-10/genx-chemicals-toxicity-assessment_tech-edited_oct-21508.pdf; EPA, “Technical Fact Sheet: Toxicity Assessment for PFBS,” April 2021, https://ofmpub.epa.gov/eims/

eimscomm.getfile?p_download_id=542401 (automatic download).

60 EPA, “PFAS National Primary Drinking Water Regulation Rulemaking,” 88 Federal Register 18638-18754, March

29, 2023.

61 EPA, “PFAS National Primary Drinking Water Regulation Rulemaking,” 88 Federal Register 18638-18754, March

29, 2023.

62 EPA, “PFAS National Primary Drinking Water Regulation Rulemaking,” 88 Federal Register 18638-18754, March

29, 2023.

63 EPA, “PFAS National Primary Drinking Water Regulation Rulemaking,” 88 Federal Register 18638-18754, March

29, 2023.

64 EPA, “PFAS National Primary Drinking Water Regulation Rulemaking,” 88 Federal Register 18638-18754, March

29, 2023.

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2023 Proposed Regulation

PFOA and PFOS

For PFOA and PFOS, EPA proposed to set the MCLG (maximum contaminant level goal) at zero.

In drinking water regulations, EPA sets the MCLG at zero for microbial contaminants and for

other contaminants when EPA (1) has evidence that a contaminant may cause cancer, and (2)

cannot determine a dose that is considered “safe.” As mentioned above, SDWA generally requires

EPA to establish the MCL (maximum contaminant level) as close to the MCLG as feasible.65 EPA

proposed MCLs for PFOA and PFOS each at 4.0 parts per trillion (ppt), which the agency found

to be the lowest level that can be reliably measured by existing analytical methods, referred to as

the detection limit.

PFHxS, PFNA, GenX Chemicals, and PFBS Hazard Index

Instead of setting numerical MCLGs and MCLs for each of the other four PFAS in the agency’s

proposed regulation, EPA proposed to use a hazard index to evaluate the potential risks of these

chemicals in aggregate. This approach involves assessing concentrations of each substance

relative to that substance’s “health-based water concentration” (HBWC). EPA states that a

contaminant’s HBWC is derived similarly to the MCLG (i.e., the level at which no adverse health

effects are anticipated to occur), combining those relative values together to calculate the hazard

index. EPA’s proposal included HBWCs for PFHxS at 9.0 ppt; GenX chemicals at 10.0 ppt;

PFNA at 10.0 ppt; and PFBS at 2,000 ppt. Water systems would divide the sampled

concentrations of each PFAS by its respective HBWC and then sum these relative values to

calculate the aggregate hazard index value. EPA proposed an MCLG and MCL for the

combination of these four PFAS at a hazard index of 1. As such, EPA’s proposal states that a

hazard index of 1 would mean that the aggregate concentrations of these four PFAS would be

below the levels at which adverse health effects occur.66 EPA stated that the hazard index is

intended to address the combined risk of potential noncancerous health effects associated with

these PFAS.

Based on the health effects information for these PFAS (discussed above in “2023 Preliminary

Determination for PFHxS, PFNA, GenX Chemicals, and PFBS”) and PFOA and PFOS, EPA also

issued an HRRCA (health risk reduction and cost analysis) for the proposed regulation, estimating

the annualized quantifiable costs and benefits each at $1.5 billion (2022 dollars), and issued a

determination that the benefits of the proposed MCLs justified the costs.67

Proposed Treatment Technologies and Options

In addition to proposing a schedule for systems to monitor for these PFAS, the regulation noted

that conventional, and most advanced, water treatment options are ineffective at removing PFAS

from water. To meet the MCLs, EPA identified that the best available treatment technologies are

anion exchange, granular activated carbon, reverse osmosis, and nanofiltration. EPA stated that

“three technologies [granular activated carbon, anion exchange, and high-pressure membranes] ...

65 SDWA §1412(b)(4)(B); 42 U.S.C. §300g-1(b)(4)(B).

66 EPA, “PFAS National Primary Drinking Water Regulation Rulemaking,” 88 Federal Register 18638-18754, March

29, 2023.

67 EPA, “PFAS National Primary Drinking Water Regulation Rulemaking,” 88 Federal Register 18638-18754, March

29, 2023.

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have all been demonstrated to be effective in removing all six PFAS.”68 Operation of these

technologies would require water systems to dispose of either a stream of waste or treatment

residuals generated from the treatment. Nontreatment options available to water systems to

achieve compliance include (1) replacing a water source with a new water source that meets the

MCLs or (2) buying water that meets the MCLs from another system.

As required by SDWA, EPA’s proposal identifies technologies that are “affordable” for small

systems. EPA finds that anion exchange and granular activated carbon are affordable for systems

that serve 10,000 or fewer individuals. For systems serving more than 3,300 individuals, reverse

osmosis and nanofiltration are considered affordable under future circumstances.69

2024 Final Determinations for PFHxS, PFNA, and GenX Chemicals

In April 2024, EPA finalized the determination to regulate PFHxS, GenX chemicals, and PFNA

individually and as mixture, and to regulate PFBS as mixture. EPA did not finalize the

determination to regulate PFBS individually.70

2024 PFAS Regulation

EPA’s final regulation in 2024 kept the 2023 proposed MCLGs and MCLs for PFOA and PFOS.71

EPA altered its approach for PFHxS, PFNA, and GenX chemicals. The agency established

MCLGs of 10 ppt for each substance and finalized MCLs at the same levels. For the hazard

index, EPA’s regulation requires water systems to assess concentrations of PFHxS, PFNA, and

GenX chemicals relative to their respective MCLs, to assess the concentration of PFBS relative to

its health-based water concentration of 2,000 ppt, and to sum two or more of these relative

concentrations to determine if the value exceeds the hazard index of 1. As such, the regulation

does not regulate PFBS individually, but only when combined with at least one other PFAS.

In addition, EPA’s regulation requires water systems to complete initial PFAS monitoring by

2027. Based on the results of the initial monitoring, water systems then have another two years to

continue monitoring, notify their customers of the monitoring results, and, if needed, take steps to

address PFAS detections above the MCLs or hazard index. These steps could include installing

advanced treatment or replacing a contaminated water source. Water systems are required to

comply with the MCLs by 2029 and to provide public notification for any MCL or monitoring

violation.

2026 Proposed Regulations

In May 2026, EPA proposed two regulations that pertain to the 2024 PFAS RD and regulation.

One proposes to rescind the RDs for the three PFAS (PFHxS, PFNA, and GenX chemicals) and to

rescind part of the PFAS regulation covering these PFAS and PFBS. The other proposes to delay

the compliance with the PFOA and PFOS MCLs for two years (i.e., compliance would be

68 88 Federal Register 18638, 18686, March 29, 2023.

69 For systems serving 3,300 individuals or fewer, EPA finds that reverse osmosis or nanofiltration would be affordable

when reverse osmosis or nanofiltration point-of-use devices that treat to the MCLs and meet the National Sanitation

Foundation (NSF) International/American National Standards Institute certification standard become available.

70 EPA, “PFAS National Primary Drinking Water Regulation,” 89 Federal Register 32532-32757, April 26, 2024.

71 EPA, “PFAS National Primary Drinking Water Regulation,” 89 Federal Register 32532-32757, April 26, 2024.

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required by 2031 rather than 2029) via a “national exemption.”72 EPA is accepting public

comment on each proposed regulation until July 20, 2026, and is planning a public hearing on

July 7, 2026.73

2026 Proposed Rescission of the RD for PFHxS, PFNA, and GenX Chemicals,

and Associated Regulation

EPA states that its proposal to rescind the RD and regulation for PFHxS, PFNA, and GenX

chemicals is based on the agency using an “unlawful procedure” to support EPA’s actions

associated with the 2024 PFAS regulation.74 In the 2026 proposal, EPA argues that SDWA

requires EPA to finalize an RD after public comment on the preliminary RD, and, only once an

RD is finalized, can EPA propose a regulation.75 As such, EPA states that the agency erred by

proposing an RD and a regulation at the same time in 2023, and now concludes that the soonest

that SDWA allows for the agency to propose a regulation is at the same time as a final RD. EPA

finds that the proposal to rescind the 2024 RD and the regulation for the other PFAS is solely

based on this misinterpretation of the statute.76 The agency states that its 2026 proposal is not

based on a change in the agency’s previous findings with regard to these contaminants’ health

effects, occurrence, or whether their regulation presents a meaningful opportunity for health risk

reduction.77

EPA’s economic analysis for the proposed rescission finds that it would result in cost savings

from reduced monitoring and avoided treatment and reporting.78 EPA estimates that its 2026

proposal would reduce the annualized costs of the 2024 PFAS regulation by $11.6 million (2022

dollars), less than 1% of the total annualized cost of the regulation.79 With regard to quantified

benefits, EPA estimates that the lack of MCLs for these PFAS would result in $6.7 million (2022

dollars) of annualized forgone benefits, less than half-a-percent of the total annualized benefits.80

2026 Proposed “National Exemption”

EPA proposed a framework to exempt water systems from the 2029 deadline for compliance with

the PFOA and PFOS MCLs prior to a state being granted primacy for the regulation.81 EPA

anticipates that nearly all water systems would be required to make capital improvements to

comply with the PFOA and PFOS MCLs. EPA states in its proposal that this national framework

72 EPA, “Extending the Compliance Deadline for the PFOA and PFOS Maximum Contaminant Levels,” 91 Federal

Provisions for Four PFAS Substances (PFHxS, PFNA, HFPO-DA (GenX), and the Mixture of These Three PFAS Plus

PFBS),” 91 Federal Register 29413-29425, May 20, 2026.

73 91 Federal Register 29413-29448, May 20, 2026.

74 91 Federal Register 29413, 29415, May 20, 2026.

75 91 Federal Register 29413, 29415, May 20, 2026.

76 91 Federal Register 29413, 29417, May 20, 2026.

77 91 Federal Register 29413, 29417, May 20, 2026.

78 91 Federal Register 29413, 29417, May 20, 2026.

79 91 Federal Register 29413, 29417-29419, May 20, 2026. The 2024 PFAS regulation estimated annualized

compliance costs at $1.548 billion (2022 dollars).

80 91 Federal Register 29413, 29420, May 20, 2026. The 2024 PFAS regulation estimated annualized benefits at

$1.549 billion (2022 dollars).

81 91 Federal Register 29425-29448, May 20, 2026

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is intended to “streamline the exemptions process and manage the potentially large number of

exemption requests.”82

EPA proposes an “exemption by rule” process that would require individual systems to request a

two-year exemption until April 26, 2031. EPA states that exemptions

•

would be granted only due to compelling factors, including costs, preventing the

system from complying with the MCLs or developing an alternative source of

water supply,

would be limited to systems in operation at the time of the effective date of the

PFOA and PFOS MCLs (i.e., June 25, 2024),

would be limited to cases where granting the exemption would not result in

unreasonable risk to health, and

would be limited to cases where “management or restructuring changes (or both)

cannot reasonably be made that will result in compliance... ”83

EPA provides several examples of relevant “compelling factors.” In addition to financial

limitations, EPA identifies uncertainty of procurement as a compelling factor, citing the increased

cost of construction materials, “ongoing volatility in global steel markets,” and supply chain

disruptions that may create delays in procurement.84 EPA also cites the challenge of hiring and

retaining a water system operator as another compelling factor, though this factor is not specific

to PFOA or PFOS.

In addition, EPA outlines potential benefits for systems seeking an exemption. EPA identifies that,

in the intervening years, additional treatment technology may be developed to treat PFOA and

PFOS to the MCLs. Further, EPA states that UCMR 5 results would give systems a better

understanding of their PFAS detections. EPA also notes that other EPA actions under different

statutory authorities (i.e., the Clean Water Act) may affect source water quality for water systems

that rely on surface water.

Regarding what constitutes an “unreasonable risk to health,” EPA proposes the threshold of 12

ppt of PFOA or PFOS in public water supplies. EPA’s proposal seeks comment on whether risk is

not “unreasonable” for systems with concentrations below 12 ppt for both PFOA and PFOS.85

This level would not replace the 2024 PFAS regulation’s MCLs of 4.0 ppt for PFOA and PFOS,

but, under EPA’s 2026 proposal, would require the system to take other actions while operating

under an exemption. Systems with detections above 12 ppt could obtain an exemption if the

system took other measures to control these substances in drinking water. EPA lists these

measures as “installation, operation, and maintenance of point-of use and/or point-of-entry (POU

and/or POE) devices, providing alternative water sources, making water filtration pitchers

available, implementing source water controls, providing public education materials on reducing

PFAS from various sources including drinking water, and conducting community outreach

activities.”86

EPA proposes that all systems apply for an exemption prior to their state receiving primacy for

the PFOA and PFOS MCLs. In the application, EPA proposes that systems provide initial

information (e.g., system identification number and most recent PFOA and PFOS sampling

82 91 Federal Register 29425, 29428, May 20, 2026.

83 91 Federal Register 29425, 29428, May 20, 2026.

91 Federal Register 29425, 29429, May 20, 2026.

85 91 Federal Register 29425, 29431, May 20, 2026.

86 91 Federal Register 29425, 29431, May 20, 2026.

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results) and statements that attest there are compelling factors that prevent a system from

complying, and the system is taking all steps possible to meet the MCLs. For systems with

detections of PFOA and PFOS above 12 ppt, EPA requires the water system submit information

on two “control measures” that would be implemented during the years the exemption is

provided.87 Water systems would have 180 days after this proposal is finalized to submit an

exemption application.

Considerations for Congress

Discussed above, SDWA’s regulatory development process contains steps intended to identify

health risks and gather occurrence data to support a regulation using the best available peerreviewed information. For water systems subject to regulation, the act’s process is intended to be

transparent both in the data EPA uses to support a regulation and in how EPA establishes the

MCLs to account for the health risk reduction benefits and costs. Once EPA finalizes a regulation,

SDWA does not allow EPA to revise that regulation to be less protective of public health, often

referred to as the anti-backsliding provision.88 Though, as stated above, SDWA does not require

that each revision of a regulation includes a more stringent MCL, if science is available that a less

stringent MCL would be just as protective. Further, SDWA does not provide EPA with the

authority to revise a regulation to be less stringent based on other aspects, such as compliance

costs.

Due to the anti-backsliding provision, a final drinking water regulation has broad effects,

particularly when water systems are required to make capital improvements to comply. Some may

contend that the anti-backsliding provision encourages EPA to take a particularly cautious

approach during the rulemaking process. Some may argue this caution is warranted; others may

argue any additional time results in a process that is unnecessarily delayed, and that may result in

more time for individuals to be exposed to a contaminant in drinking water.

EPA’s PFAS actions may be among several financial and regulatory issues faced by water

systems. These include water main breaks and other aging infrastructure issues and associated

potential contamination, compliance challenges with other regulations (e.g., regulation to control

lead and copper), and threats from cyberattacks that could disrupt or contaminate public water

supplies. The text box “Other Actions That May Affect Water Systems” discusses other PFASrelated considerations for water systems.

Other Actions That May Affect Water Systems

Outside of the Safe Drinking Water Act, water systems may face other requirements based on other federal

statutes. In 2024, EPA announced a final rule designating perfluorooctanoic acid (PFOA) and

perfluorooctanesulfonic acid (PFOS) as hazardous substances under the Comprehensive Environmental Response,

Compensation, and Liability Act (CERCLA).89 CERCLA imposes liability on certain parties responsible for the

presence of hazardous substances at a site. CERCLA establishes financial liability for four categories of potentially

responsible parties: (1) the current owner or operator of a facility; (2) former owners or operators of a facility at

the time hazardous substances were disposed of there; (3) generators and parties that arranged for the transport,

disposal, or treatment of hazardous substances; and (4) transporters of hazardous substances to a facility. Water

87 91 Federal Register 29425, 29434, May 20, 2026.

88 SDWA §1412(b)(9); 42 U.S.C. §300g-1(b)(9).

89 For questions on the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) liability,

congressional offices may contact Kate Bowers, CRS Supervisory Attorney. For questions on CERCLA, congressional

offices may contact Lance Larson, CRS Analyst in Environmental Policy. The rule designation was announced on

April 19, 2024, and published on May 8, 2024. EPA, “Designation of Perfluorooctanoic Acid (PFOA) and

Perfluorooctanesulfonic Acid (PFOS) as CERCLA Hazardous Substances,” 89 Federal Register 39124, May 8, 2024.

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systems that meet one of the above designations may be considered liable under CERCLA where there has been a

release or threatened release of a hazardous substance that causes the incurrence of response (or cleanup)

costs.90

Also in 2024, EPA issued an enforcement discretion and settlement policy explaining how the agency would

exercise its enforcement discretion under CERCLA in matters involving PFAS.91 EPA identified that community

water systems are among the entities against which it generally did not intend to pursue PFAS response actions or

costs under CERCLA, subject to some limitations. Given that enforcement policy is subject to the discretion of

the agency and does not shield covered entities from all potential liability, water system associations have

supported legislation that would exempt water systems from CERCLA liability under certain circumstances.92

This section identifies several issues that pertain to EPA’s PFAS actions and provides selected

trade-offs and considerations. Specifically, the topics covered by this section include

•

compliance with SDWA’s regulatory development process,

rescinding a final RD,

implementing EPA’s proposal to provide exemptions,

states’ adoption of a PFAS regulation

petitions for review, and

compliance assistance.

Compliance with SDWA Regulatory Development Process

Some have questioned whether EPA’s PFAS actions have followed SDWA’s regulatory

development process.93 In 2023, EPA performed two steps of SDWA’s regulatory development

process simultaneously by proposing both an RD for the four PFAS and a regulation that covered

those PFAS. (The 2023 proposed regulation also included PFOA and PFOS, which were

addressed by a 2021 RD.) In 2026, EPA stated that it acted in error when doing so.94

EPA’s 2024 approach to expediting SDWA’s steps may lead to questions and concerns from

policymakers and stakeholders, as Congress established SDWA’s regulatory development process

and the Biden Administration’s actions may not have followed it. In contrast, some may defend

EPA’s 2024 approach, viewing the consolidated actions as having resulted in the reduction of

health risks more quickly,95 and pointing out that the need for the regulation was not changed

because of the additional data from UCMR 5, as discussed in the text box “Data Availability and

Sufficiency.”

90 The scope of CERCLA liability is detailed in CRS In Focus IF11790, Liability Under the Comprehensive

Environmental Response, Compensation, and Liability Act (CERCLA), by Kate R. Bowers.

91 Memorandum from David M. Uhlmann, Assistant Administrator for Enforcement and Compliance Assurance, EPA,

to regional administrators, deputy regional administrators, regional counsels, and deputy regional counsels, “PFAS

Enforcement Discretion and Settlement Policy Under CERCLA,” April 19, 2024, https://www.epa.gov/system/files/

documents/2024-04/pfas-enforcement-discretion-settlement-policy-cercla.pdf.

92 American Water Works Association, “AWWA Extends Support for Bipartisan Introduction of Water Systems PFAS

Liability Protection Act,” press release, February 12, 2025, https://www.awwa.org/AWWA-Articles/awwa-extendssupport-for-bipartisan-introduction-of-water-systems-pfas-liability-protection-act/. See, for example, Water Systems

PFAS Liability Protection Act, H.R. 1267 (119th Congress).

93 Petition for Review, American Water Works Association v. EPA, No. 24-1188 (D.C. Cir. filed June 7, 2024).

94 91 Federal Register 29413, 29415, May 20, 2026.

95 See for example, Natural Resources Defense Council, “NRDC Seeks to Defend Biden EPA Restrictions on Forever

Chemicals in Drinking Water Water Utilities, Chemical Industry Challenging PFAS Rule,” press release, July 1, 2024,

https://www.nrdc.org/press-releases/nrdc-seeks-defend-biden-epa-restrictions-forever-chemicals-drinking-water-water.

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Data Availability and Sufficiency

Determining whether the available data are sufficient to make a regulatory determination often involves judgment

and discretion by the EPA Administrator. In the past, some stakeholders have regarded SDWA science-based and

risk-driven process as too slow, postponing the risk reduction benefits of limiting contaminants in public water

supplies.96 EPA’s 2023 PFAS actions demonstrate how condensing regulatory steps creates a trade-off between

developing sufficient data and acting promptly to regulate a contaminant. SDWA’s stepwise process allows EPA to

consider new information after the agency has proposed an RD. Some may argue this new information could help

EPA develop a more effective regulatory approach than would otherwise have occurred. Others may argue that

EPA may already have sufficient information to make both an RD and a regulation and additional data would not

significantly change the outcome.

An example of the trade-off regarding data availability involves the occurrence data EPA used for PFHxS, PFNA,

and GenX chemicals. EPA stated that it acted on the best-available information at the time of occurrence (from

UCMR 3 data and data from selected states), instead of waiting for UCMR 5 data. This demonstrates the trade-off

between waiting to obtain complete data and acting promptly to regulate these contaminants. For the preliminary

RD and the proposed rule, EPA relied upon occurrence data for PFNA, PFHxS, and PFBS from UCMR 3. As

discussed above, the method used for UCMR 3 was unable to detect PFAS at the lower levels EPA required for

testing under UCMR 5. As such, when detections occurred in UCMR 3, they were at higher levels than the

proposed PFAS MCLs.

EPA used a model to estimate occurrence of GenX chemicals, as well as to estimate the occurrence of PFNA,

PFHxS, and PFBS at lower levels than were measured in UCMR 3. To do so, EPA relied on finished water data

from selected states.97

Between the proposed regulation in 2023 and the final regulation in 2024, EPA’s estimates of the number of

systems that would require treatment increased. EPA published its 2023 cost model for HRRCA that roughly

4,300 systems would need to take steps to comply with the PFAS regulation, based on the model of state data and

UCMR 3 results.98 In the final regulation, EPA updated the HRRCA and increased the estimated number of

systems to roughly 5,100. EPA attributed this increase to findings from the portion (i.e., 24%) of UCMR 5 results

that had been reported by February 2024.99

One question may be whether it would have been feasible for EPA to use more recent UCMR 5 data.100 Sample

collection under UCMR 5 began in January 2023, two months before EPA proposed the RD for the four other

PFAS in March 2023. If EPA had followed the same time frame between the preliminary and final RD for PFOA

and PFOS, the agency would have had access to occurrence data for the four PFAS (PFNA, PFHxS, PFBS, and

GenX) at lower levels. For example, about a year after March 2023, the agency reported that roughly 35% of the

UCMR 5 sampling was completed, and EPA reported on the detections of PFAS above the MCLs.101 While some

UCMR 5 data were available, monitoring under UCMR 5 was not complete until the end of 2025.

Another question is whether waiting to obtain UCMR 5 data might have led EPA to make different estimates, and

therefore, whether it might have made a difference in EPA’s determination to regulate these other PFAS. As of

January 2026, EPA reports that UCMR 5 data indicate that roughly 8% of water systems subject to the

regulation—about 5,300—would have PFAS detections above the regulation’s MCLs.102 This figure is comparable

to EPA’s HRRCA estimate of roughly 5,100 systems that would require treatment, though the proportion of

smaller and larger systems may have changed. Given this, some stakeholders may question whether waiting for the

results of UCMR 5 would have resulted in any meaningful change to EPA’s actions. Further, delaying regulatory

96 In the 117th and 118th Congresses, Members introduced legislation regarding SDWA’s regulatory development

provisions primarily intended to expedite the regulation of PFAS. See, for example, Senate Committee on Environment

and Public Works, “Stakeholder Comment on Draft PFAS Legislation,” press release, June 22, 2023.

97 88 Federal Register 18638, 18675, March 29, 2023.

98 88 Federal Register 18638, 18701, March 29, 2023.

99 89 Federal Register 32532, 32533, April 26, 2024.

100 EPA, “Revisions to the Unregulated Contaminant Monitoring Rule (UCMR 5) for Public Water Systems and

Announcement of Public Meetings,” 86 Federal Register 73131, December 27, 2021.

101 EPA, The Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) Data Summary: April 2024, EPA 815-S-24007, April 2024, https://web.archive.org/web/20240714211637/https://www.epa.gov/system/files/documents/2023-08/

ucmr5-data-summary_0.pdf.

102 EPA, The Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) Data Summary: January 2026, EPA 815-S24-007, January 2026, https://www.epa.gov/system/files/documents/2023-08/ucmr5-data-summary_0.pdf.

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action to wait for better data would seem to also delay the health risk reduction benefits of regulating a

contaminant in drinking water.

Amending SDWA to stipulate the order of specific regulatory development steps (e.g., whether

EPA is required to propose an RD before it proposes a regulation) and time frames for specific

regulatory development steps (e.g., within how many months EPA is required to finalize an RD)

might create additional certainty for water systems and the public. In contrast, prescribing the

order and time frames for each step may not be warranted for contaminants with sufficient

available data other than the complete UCMR data that EPA collects for the regulatory process,

could result in the agency delaying a regulation, and could result in harmful contaminants

continuing to be in public water supplies for a longer time period. Also, depending on their

stringency or cadence, EPA may have difficulty meeting specific statutory time frames, and

missed time frames may give rise to legal challenges about whether the regulatory process was

properly completed.

As such, one consideration for Congress may involve the relative priority of creating a

transparent and certain process, as compared to providing the Administrator more discretion

about the timing of the process to regulate contaminants. In its current form, SDWA’s key

authority is the regulation of harmful contaminants in drinking water and the resulting protection

of public health. Prescribing a schedule may inhibit EPA’s ability to issue regulations in a timely

manner, leading to continued exposure to contaminants in public water supplies. Adding

discretion for EPA to determine when to take specific regulatory development steps, based on

available data or whether to take two steps at the same time, may increase (or decrease) the speed

by which EPA regulates contaminants, and it could lead to more questions if it is unclear what

information EPA is using, and what steps it is taking, to support its actions.

Rescinding a Final RD

EPA’s 2026 proposal to rescind the 2024 RD raises questions related to the finality of positive

RDs. EPA’s actions with regard to another drinking water contaminant, perchlorate, demonstrate

an earlier example of EPA changing an RD. In 2008, EPA made a preliminary negative

determination (a determination not to regulate) for perchlorate, but did not finalize the

determination.103 In 2011, EPA reversed the proposed negative determination and published a

final regulatory determination that perchlorate warranted regulation, noting that the agency would

begin the process of proposing a drinking water regulation for perchlorate.104 In 2020, after

proposing a perchlorate regulation in 2019,105 EPA published a “Notice of Final Action” in

the Federal Register, withdrawing the 2011 positive regulatory determination for

perchlorate.106 In 2023, the U.S. Court of Appeals for the D.C. Circuit vacated EPA’s 2020

withdrawal of its regulatory determination.107 The court determined that SDWA did not provide

103 EPA, “Drinking Water: Preliminary Regulatory Determination on Perchlorate,” 73 Federal Register 60262-60282,

October 10, 2008.

104 EPA, “Drinking Water: Regulatory Determination on Perchlorate,” 76 Federal Register 7762-7767, February 11,

2011.

105 EPA, “National Primary Drinking Water Regulations: Perchlorate,” 84 Federal Register 30524-30569, June 26,

2019.

106 EPA, “Drinking Water: Final Action on Perchlorate,” 85 Federal Register 43990-44002, July 21, 2020.

107 Natural Resources Defense Council (NRDC) v. Michael S. Regan, Administrator, U.S. Environmental Protection

Agency, No. 20-1335 2023 (D.C. Cir.).

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EPA with the authority to withdraw a final RD,108 “despite new and additional data and analyses

that changed the scientific underpinnings of the original regulatory determination.”109 As such,

EPA is required under SDWA to finalize a drinking water regulation for perchlorate.110 Given this,

one question may involve whether EPA may rescind an RD for procedural reasons rather than a

change in the understanding of a contaminant’s occurrence or health effects, or whether EPA’s

2024 RD finalization would mean that the agency would have to propose and finalize a regulation

for PFHxS, GenX chemicals, and PFNA.

Implementing EPA’s Proposal for Exemptions

Regarding SDWA’s federal-state arrangement, EPA’s 2026 proposal to provide a “national

framework” for exemptions raises several questions for consideration, including those that pertain

to the role of the state and the role of EPA in providing exemptions.

When Can an Exemption Be Provided?

A key question may be at what time an exemption can be provided, whether at the effective date

of a regulation, the compliance date for an MCL, or sometime in between (e.g., after states have

received primacy for a regulation). EPA’s 2026 proposal relies on its interpretation of SDWA

Section 1416, which authorizes states to grant public water systems temporary exemptions from

drinking water regulations if a system cannot comply for specific reasons, which includes

compliance costs.111 The legislative history of Section 1416 details the conditions under which

EPA could grant an exemption. It states that “water systems in States which do not have primary

enforcement responsibility may obtain exemptions from EPA in the same manner and under the

same conditions as they could from the State, if it had primary enforcement responsibility.”112

This implies that some states have been granted primacy for a regulation.

As such, one question may be whether exemptions can be granted before any state is granted

primacy for MCLs that are not enforceable for several more years. Another question is the extent

to which EPA providing exemptions via a national framework aligns to SDWA’s legislative intent

to have the states assess whether to provide an individual system with an exemption on a limited

basis. Another consideration pertains to EPA’s capacity to evaluate and validate exemption

applications from water systems, and how that would compare to state oversight of the same

systems.

State Primacy for the PFAS Regulation

Relatedly, in 2025, EPA issued a memorandum to “strongly encourage” states to apply for

extensions for primary enforcement of the 2024 PFAS regulation.113 SDWA regulations allow

108 Natural Resources Defense Council (NRDC) v. Michael S. Regan, Administrator, U.S. Environmental Protection

Agency, No. 20-1335 2023 (D.C. Cir.).

109 EPA, “Perchlorate in Drinking Water,” https://www.epa.gov/sdwa/perchlorate-drinking-water.

110 EPA proposed a regulation for perchlorate in January 2026. See EPA, “National Primary Drinking Water Regulation

for Perchlorate,” 91 Federal Register 398-444, January 6, 2026. EPA proposed that the MCLG for perchlorate be 20

parts per billion (ppb), and took comment on possible MCLs of 20 ppb, 40 ppb, 60 ppb, and 80 ppb.

111 42 U.S.C. §300g-5.

112 H.Rept. 93-1185.

113 EPA, Primacy Extension Request Documents for the 2024 Control of Per- and Polyfluoroalkyl Substances National

Primary Drinking Water Regulation, Washington, D.C., September 30, 2025, https://www.epa.gov/system/files/

documents/2025-09/memorandum-for-primacy-extension-request-documents-for-the-2024-pfas-npdwr.pdf.

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states to apply for a two-year extension to submit their application for primacy for a regulation.114

For the 2024 PFAS regulation, if a state did not request an extension by April 27, 2026, then the

state is required to submit a primacy application package by that date or not be considered for

SDWA primacy. EPA reports that Idaho and Illinois have applied for primacy for the 2024 PFAS

regulation, and that 47 states, the territories, and the Navajo Nation applied for an extension.115

(EPA retains primacy for Wyoming and District of Columbia.) States that did request an extension

would have until April 26, 2028, to submit their application for primacy over the 2024 PFAS

regulation. EPA states that its proposal to extend the compliance time frame to 2031 is based on

the agency retaining primacy for PFOA and PFOS MCLs, which would become enforceable in

2029.116 One question is whether any of the 47 states, territories, and the Navajo Nation applying

for an extension would not submit a primacy application for the PFAS regulation. Another

question may be whether a state that gains primacy after EPA provided exemptions for systems

operating in that state would continue those EPA-provided exemptions.

States’ Adoption of PFAS Regulation

No SDWA provision prohibits states from adopting more stringent drinking water regulations

than federal regulations. Some states prohibit the adoption of more stringent standards than those

promulgated by EPA. In the SDWA legislative history, Congress stated its intent is “that States

and public water systems take the primary responsibility for assuring the safety of the Nation’s

drinking water supplies.”117 At the time, Congress was “hopeful that State and Federal

cooperation will be the rule and that the States will take the lead in adopting standards, reviewing

compliance strategies, and where necessary bringing enforcement actions.”118 EPA states that

Idaho and Illinois have submitted applications for primacy of the 2024 PFAS regulation.119 States

may move ahead and choose to adopt and implement the 2024 PFAS regulation or more stringent

PFAS standards under their own state laws, regardless of EPA’s 2026 proposals to change the

regulation’s scope or compliance time frames.

Petitions for Review

The U.S. Court of Appeals for the D.C. Circuit is reviewing three petitions for review of specific

aspects of the 2024 PFAS regulation. Among the contested actions, some views challenge the

concept of regulating a mixture of substances through a “hazard index,” arguing that this concept

is not aligned with the act or not appropriate given the characteristics of specific PFAS.120 Some

arguments pertain to EPA’s HRRCA (health risk reduction and cost analysis), stating that, since

one HRRCA was issued for the PFAS covered by the regulation, the benefits and costs of

regulating each individual substance are obscured.121 Others may argue that there is precedent for

this approach: under other regulations, including the Radionuclides Rule and the Stage 2

Disinfectants and Disinfection Byproducts Rule, EPA developed one HRRCA that considered the

114 40 C.F.R. §142.12(b).

115 Email communication between CRS and EPA, June, 6, 2026.

116 91 Federal Register 29425-29448, May 20, 2026.

117 U.S. Congress, House Interstate and Foreign Commerce Committee, Safe Drinking Water Act, 93rd Cong., 2nd sess.,

July 10, 1974, H.Rept. 93-1185.

118 H.Rept. 93-1185.

119 Email communication between CRS and EPA, June 6, 2026.

120 Petition for Review, American Water Works Association v. EPA, No. 24-1188 (D.C. Cir. filed June 7, 2024);

Petition for Review, The Chemours Company v. EPA, No. 24-1192 (D.C. Cir. filed June 10, 2024).

121 Petition for Review, National Association of Manufacturers v. EPA, No. 24-1191 (D.C. Cir. filed June 10, 2024).

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costs and benefits of the regulation’s MCLs.122 These questions before the court are beyond the

scope of this report. One option for policymakers is to wait for the U.S. Court of Appeals for the

D.C. Circuit to determine the outcome of the petitions to review EPA’s 2024 PFAS regulation.

The court’s decision may provide more clarity for EPA’s implementation of SDWA’s regulatory

development provisions going forward.

Compliance Assistance

Some Members of Congress may be interested in assisting systems with treatment projects

needed for compliance with the regulation’s MCLs. For the 2024 PFAS regulation, the HRRCA

estimates that water systems that need treatment technology to comply with the MCLs will have

to invest—in aggregate—$14.4 billion (in 2022 dollars) in 2029 for such capital improvements.123

EPA’s 2026 proposal to rescind the MCLs for PFHxS, PFBS, and PFNA, and the hazard index for

these substances and PFBS, estimates that these costs would not significantly change as PFOA

and PFOS would still be regulated.124 Based on EPA’s estimate that 5,139 systems would need to

take steps to comply, the average per system investment equates to about $2.8 million.125 EPA’s

HRRCA further estimates that the ongoing operations and maintenance of the treatment

technology would be $1.2 billion (in 2022 dollars) in aggregate per year.126 This would not be

included in the $625 billion estimated by EPA for infrastructure needs that systems are expected

to face between 2023 and 2043.127 The Congressional Budget Office (CBO) estimates that 96% of

public spending on this type of infrastructure comes from state and local sources,128 meaning that

some communities may face budgetary and affordability challenges as water systems cover the

costs of such projects. Typically, these costs are spread across the system’s customer base as

water rates, which may have to be increased to support such investments.129

The Infrastructure Investment and Jobs Act (IIJA; P.L. 117-58) provided significant increases in

appropriations for the primary federal program that supports this type of infrastructure, the

Drinking Water State Revolving Fund (DWSRF).130 IIJA provided an average of $3.14 billion per

fiscal year for FY2022 through FY2026 to the DWSRF that could be used for projects, such as

122 EPA, “National Primary Drinking Water Regulations: Stage 2 Disinfectants and Disinfection Byproducts Rule;

National Primary and Secondary Drinking Water Regulations: Approval of Analytical Methods for Chemical

Contaminants,” 68 Federal Register 49548-49681, August 18, 2003. EPA, “Preliminary Health Risk Reduction and

Cost Analysis for the Revised National Primary Drinking Water Regulation for Radionuclides,” January 2000,

https://www.epa.gov/sites/default/files/2015-09/documents/

2009_04_16_radionuclides_regulation_radionuclides_rulemaking_prelimaryhrcca.pdf.

123 89 Federal Register 32532, 32639, April 26, 2024.

124 91 Federal Register 29413, 29417-29419, May 20, 2026.

125 Individual systems’ installation and maintenance costs are likely to vary significantly based on systems’ location,

size, and other factors. For more information about water systems’ costs and affordability, see CRS Report R48271,

Paying for Drinking Water: Background and Issues for Congress, by Elena H. Humphreys.

126 EPA, Economic Analysis for the Final Per- and Polyfluoroalkyl Substances National Primary Drinking Water

Regulation Appendices, EPA-815-R-24-002, April 2024, https://www.epa.gov/system/files/documents/2024-04/pfasnpdwr_final-rule_ea_appendices.pdf.

127 EPA, 7th Drinking Water Infrastructure Needs Survey and Assessment, April 2023, https://www.epa.gov/system/

files/documents/2023-04/Final_FAQ_DWINSA_4.4.23.v1.pdf.

128 Congressional Budget Office, Public Spending on Transportation and Water Infrastructure, 1956 to 2023, February

2025, https://www.cbo.gov/system/files/2025-02/60874-InfrastructureSpending.pdf.

129 For more information about water rates, see CRS Report R48271, Paying for Drinking Water: Background and

Issues for Congress, by Elena H. Humphreys.

130 For more information about the Infrastructure Investment and Jobs Act (IIJA; P.L. 117-58), see CRS Report

R46892, Infrastructure Investment and Jobs Act (IIJA): Drinking Water and Wastewater Infrastructure, by Elena H.

Humphreys and Jonathan L. Ramseur.

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those to install treatment technology that would address PFAS. Further, IIJA dedicated DWSRF

appropriations specifically for grants to address emerging contaminants, with an emphasis on

PFAS. At the time of enactment, these IIJA appropriations represented almost a threefold increase

in prior years’ average annual appropriations for the DWSRF.

An implementation consideration for policymakers involves the types of systems that may require

treatment to comply with the regulation. UCMR 5 results indicate that a higher proportion of

larger water systems may have detections of PFOA and PFOS above the MCL:

•

12% of water systems serving more than 10,000 individuals had detections of

PFOA above the MCL, whereas 4.4% of sampled systems serving 3,300 or fewer

individuals had PFOA detections above the MCL, and

11% of systems serving more than 10,000 individuals had detections of PFOS

above the MCL, whereas 6.0% of sampled systems serving 3,300 or fewer

individuals had PFOS detections above the MCL.

When larger systems need to install treatment technology to comply with the regulation’s MCLs,

the capital improvements and associated compliance costs would be spread across a larger

customer base. Spreading costs over a larger number of customers typically would result in less

of a burden for each individual customer as compared to a system with a very small customer

base.131

System Support Considerations

Congress may consider oversight options regarding the extent to which systems have already

received assistance funding via the IIJA or found other financing to address infrastructure

upgrade needs. In addition, capital improvement projects require time to commence and

complete; thus, systems may already be in the process of securing financing for needed projects.

If systems have already secured funding for the needed infrastructure, providing additional

appropriations specifically for such projects may lead to unused funding or funding advanced

treatment projects for systems that do not need it for regulatory compliance. Understanding the

extent to which systems that need to install treatment to comply with the regulation have accessed

federal assistance may be a first step in determining whether additional funds would assist

systems with such projects.

Another consideration regards the framework for providing funds. Congress could provide

support in several different ways: through broad funding programs, such as the DWSRF, or by

limiting project eligibility for funding programs to PFAS compliance. Providing appropriations

for a more general set of water infrastructure projects may result in fewer dollars going to support

projects needed specifically for PFAS compliance. Given that an estimated $625 billion is needed

for water infrastructure projects between 2023 and 2043, systems may seek assistance for other

high-priority projects unrelated to PFAS. Funding provided for projects needed to comply with

the regulation would help offset systems’ specific costs due to this regulation, but, depending on

budgetary conditions, may come at the expense of resources to assist systems with compliance

with other drinking water regulations.

131 CRS Report R48271, Paying for Drinking Water: Background and Issues for Congress, by Elena H. Humphreys,

contains additional information about water system costs.

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In addition, as CBO estimated, federal support makes up about 4% of total public spending for

this type of infrastructure; some may question the incremental impact of more federal funding

when the majority of public spending comes from state and local sources. As discussed above,

UCMR 5 data indicate that a higher proportion of larger systems may have to take steps to

comply with the MCLs, and that such systems benefit from economies of scale. Others may

question whether the balance between federal and state and local spending is appropriate. If

Congress decides to maintain the current ratio of spending between levels of governments,

policymakers could further tailor federal support to communities facing the greatest affordability

concerns as a result of the PFAS regulation.

Congress may also consider the balance between technical assistance and financial assistance.

Some systems, particularly smaller ones, may face challenges accessing federal assistance. On the

one hand, given the varying technical capacity of water systems, providing additional financial

assistance through federal programs may be less cost-effective than increasing technical

assistance to smaller water systems through other SDWA authorities. On the other hand, given the

occurrence data from UCMR 5, a greater percentage of larger water systems appear to have

detected PFAS above the regulation’s MCLs. As such, increasing technical assistance for smaller

systems may not be as impactful to larger water systems that may have sufficient technical

capacity.

Author Information

Elena H. Humphreys

Specialist in Environmental Policy

Acknowledgments

Amber Hope Wilhelm, Visual Information Specialist, provided graphics support for this report. Michael M.

McCarthy, CRS Editorial and Review Office Editor, provided formatting and editorial support.

Disclaimer

This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan

shared staff to congressional committees and Members of Congress. It operates solely at the behest of and

under the direction of Congress. Information in a CRS Report should not be relied upon for purposes other

than public understanding of information that has been provided by CRS to Members of Congress in

connection with CRS’s institutional role. CRS Reports, as a work of the United States Government, are not

subject to copyright protection in the United States. Any CRS Report may be reproduced and distributed in

its entirety without permission from CRS. However, as a CRS Report may include copyrighted images or

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copy or otherwise use copyrighted material.

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R49007 · VERSION 1 · NEW

This is a copy of a public record, reproduced as it was published. It is not legal advice, and it may not be the version a court would rely on. Check the official source before you cite it.