EPA Proposes National Drinking Water Regulation for Six PFAS Compounds

March 17, 2023

Key Takeaways:

  • EPA has announced proposed national drinking water standards for six PFAS compounds, including PFOA and PFOS.
  • The regulation would create enforceable Maximum Contaminant Levels for these PFAS, and states would be required to implement the same or a stricter standard.
  • The regulation, which EPA expects to finalize by the end of 2023, will require public water systems to take action if PFAS levels exceed these new standards, leading to potential impacts on those who use PFAS-containing compounds.
  • Given this significant development, now is the time for companies who have used or potentially used PFAS to assess their regulatory and legal risk and plan proactive risk mitigation and compliance.

On March 14, the U.S. Environmental Protection Agency (EPA) announced a proposed National Primary Drinking Water Regulation (NPDWR) for six perfluoroalkyl substances (PFAS) including perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), which are among the more well-known PFAS compounds.1 PFAS have historically been used by a wide range of industries for their water-resistant and stain-resistant properties, as well as their stability.2 This announcement is a significant step in this administration’s 2021 PFAS Strategic Roadmap, a set of policy aims for greater monitoring and regulation of PFAS. Indeed, on the same day as the EPA’s announcement, the White House’s National Science and Technology Council released a report that outlined the numerous activities underway with respect to PFAS by a myriad of federal agencies beyond just EPA, including the Food and Drug Administration, Centers for Disease Control, National Institute of Standards and Technology, and others.3

Details of the Proposed National Primary Drinking Water Regulation for Six PFAS

The proposed regulation would set an enforceable Maximum Contaminant Level (MCL) for PFOA at 4 parts per trillion (ppt), with the same MCL for PFOS.4 Those MCLs are lower than many state clean-up standards or state-level MCLs. Additionally, EPA set health-based Maximum Contaminant Level Goals (MCLGs) for PFOA and PFOS at zero.5 EPA also issued a statement in a FAQ document “that there is no level of these contaminants that is without a risk of adverse health effects” and that “PFOA and PFOS are likely carcinogens (i.e., cancer causing).”6 In other documents released by EPA with its announcement, EPA states that the label “likely carcinogen” applies to “an agent demonstrating a plausible (but not definitively causal) association between human exposure and cancer.”7 EPA has also stated that MCLGs of zero are used for substances “for which there is insufficient information to determine that a carcinogen has a threshold below which there are no carcinogenic effects.”8 EPA has described this decision for the MCLGs as a “health-protective approach,”9 as it has long been recognized that  an “administrative agency may regulate or prohibit the use of toxic substances through rulemaking, despite a very low probability of any causal relationship.”10 EPA’s approach is consistent with courts’ commentary that such “regulatory standards often build in considerable cushion in order to ... protect the public,” and are distinct from identifying “exposure levels that actually cause harm.”11

EPA also proposed a “hazard index” for the combination of perfluorohexane sulfonic acid (PFHxS), hexafluoropropylene oxide dimer acid (HFPO-DA) and its ammonium salt (also known as a GenX chemicals), perfluorononanoic acid (PFNA), and perfluorobutane sulfonic acid (PFBS).12 Under this hazard index, the sum of the ratios of each of the four PFAS compounds as compared to a Health Based Water Concentration (HBWC), which is the level below which no health effects are expected for that PFAS, must not exceed 1.0.13 The HBWC for PFHxS, GenX chemicals, PFNA, and PFBS are 9, 10, 10, and 2000 ppt, respectively.14

The EPA distinguished these proposed regulations, which will be legally enforceable when finalized, from its drinking water health advisories issued in June 2022, which received significant attention from the regulated community but are nevertheless not enforceable.

If the proposal becomes finalized, then states will be required to have a standard for public water systems that is no less strict than the NPDWR, as required by the Safe Drinking Water Act.15 Additionally, public water systems will be required to monitor for the six PFAS and notify the public if monitoring detects PFAS above the MCLs.16 Furthermore, public water systems would be required to take remedial actions in the event of an exceedance, such as installing treatment systems or switching to an alternative water supply.17 These activities are estimated to cost water systems several hundreds of millions of dollars or even one billion dollars annually, as reflected in the EPA’s economic analysis.18

Reactions To EPA’s Proposed Regulation

EPA has now taken its most significant action to regulate PFAS.  This step has already begun to cause ripple effects across industries, state and local regulators, and litigants.

While EPA’s proposed standards have been praised by some as a long-awaited step toward formally regulating these compounds, others question the scientific basis for EPA’s proposal.  The American Chemistry Council released a statement noting its “serious concerns with the underlying science used to develop these proposed MCLs.”19 The group also criticized any regulatory scheme that would treat all PFAS as a class without recognizing their unique chemical compositions.20

Furthermore, some state officials have raised concerns not only about the scientific basis of the proposal but also with the potential financial costs.  New Hampshire Governor Chris Sununu commented that the proposed standards are “unreasonable” and “unattainable in many ways,” and “[t]here’s a question not just of the science behind it but the hundreds and hundreds of billions of dollars it would take to even try to attain the levels [EPA is] pushing."21

Import of EPA’s Proposal and Next Steps

EPA’s milestone action will result in real-world consequences for litigants, municipalities, states, water providers, companies who may have used PFAS, and other stakeholders.

Compliance with EPA’s proposed standards creates a regulatory burden and expense for many of the nation’s public entities and individuals. Testing properties at such low levels is challenging and requires significant resources.  Indeed, EPA determined that its 4 ppt MCL for PFOA and PFOS “is the lowest concentration that PFOA and PFOS can be reliably quantified” with EPA-approved methods.22 Further, mitigating potential impacts of PFAS at these low levels is a complex and costly undertaking that is likely to require, among other things, expensive and energy consuming water monitoring, testing, and potential treatment. 

While public water systems are ultimately responsible for MCL compliance, downstream companies that discharge into those systems need to prepare for an influx of new monitoring, testing, reporting, and certification requirements related to PFAS. As water providers strive to meet the new standards, these requirements are likely to be even more onerous within systems that do not currently meet the MCLs. Water providers are likely to seek cost sharing from users or potential users of PFAS whose raw materials, finished products, or waste may have contributed to the presence of PFAS in the water, which will spawn litigation over these issues. Given the ubiquity of PFAS in a wide range of materials across a variety of industries, the list of companies and other parties who may be asked to cover such costs is likely to be extensive.

These MCLs are certain to generate comments from the regulated community and other stakeholders. The comment period will last 60 days and will open once the proposed rule is published in the Federal Register.23 Subsequently, EPA will consider the comments and may issue a final rule, with or without amendment from the original proposal.  EPA anticipates finalizing the rule by the end of 2023.24 The finalized rule would require compliance within three years.25

One thing is clear: EPA is committed to its Strategic Roadmap and to regulating PFAS. The proposed MCLs provide a target upon which water systems will base future actions, including new testing and reporting requirements for downstream companies. And stakeholders should use the proposed MCLs to evaluate their own operations. Now is the time for users or potential users of PFAS to assess their legal and regulatory risk and make plans for proactive risk mitigation and compliance.


  1. EPA, Per- and Polyfluoroalkyl Substances (PFAS): Proposed PFAS National Primary Drinking Water Regulation (March 14, 2023) (“EPA, Proposed PFAS NPDWR Announcement”).
  2. Gluge et al., An Overview of the uses of per- and polyfluoroalkyl substances (PFAS) (2020) Environ. Sci.: Processes, 22:2345, 2349.
  3. National Science and Technology Council, Per- and Polyfluoroalkyl Substances (PFAS) Report (March 2023).
  4. EPA, Proposed PFAS National Primary Drinking Water Regulation: Frequently Asked Questions and Answers (March 14, 2023), at 3 (“EPA, FAQ”).
  5. EPA, Proposed PFAS NPDWR Announcement, supra.
  6. EPA, Proposed PFAS National Primary Drinking Water Regulation: FAQs for Drinking Water Primary Agencies (March 14, 2023), at 3 (“EPA, FAQ for Drinking Water Primary Water Agencies”).
  7. EPA, Toxicity Assessment and Proposed Maximum Contaminant Level Goal for Perfluorooctanoic Acid (PFOA) in Drinking Water (Public Comment Draft) (March 2023), at 3-306.
  8. Id. at 2-19, 2-20.
  9. Id. at 5-1; see also EPA, Toxicity Assessment and Proposed Maximum Contaminant Level Goal for Perfluorooctane Sulfonic Acid (PFOS) in Drinking Water (Public Comment Draft) (March 2023), at 5-1.
  10. In re Agent Orange Prod. Liab. Litig., 597 F. Supp. 740, 785 (E.D.N.Y. 1984), aff’d, 818 F.2d 145 (2d Cir. 1987).
  11. Williams v. Mosaic Fertilizer, LLC, 889 F.3d 1239, 1247 (11th Cir. 2018).
  12. EPA, FAQ, supra, at 3.
  13. EPA, PFAS National Primary Drinking Water Regulation Rulemaking (Pre-publication version), at 103-04 (“EPA, PFAS NPDWR Pre-publication version”).
  14. Id. at 7.
  15. EPA, FAQ for Drinking Water Primary Water Agencies, supra, at 1.
  16. EPA, FAQ, supra, at 3-4.
  17. Id. at 4.
  18. EPA, Economic Analysis for the Proposed Per- and Polyfluoroalkyl Substances National Primary Drinking Water Regulation (March 2023) (Draft for Public Comment), at 5-2.
  19. American Chemistry Council, ACC Comments on MCL Proposal (March 14, 2023).
  20. Id.
  21. Adam Sexton, New proposed PFAS limits applauded by activists, but NH governor skeptical, WMUR (March 15, 2023).
  22. EPA, PFAS NPDWR Pre-publication version, supra, at 106.
  23. EPA, Proposed PFAS NPDWR Announcement, supra.
  24. EPA, FAQ, supra, at 2.
  25. EPA, PFAS NPDWR Pre-publication version, supra, at 162.

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