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March 16, 2023

EPA Proposes First-Ever National Drinking Water Standard for Six PFAS

The ACTA Group

On March 14, 2023, the U.S. Environmental Protection Agency (EPA) announced that it will propose the first-ever national drinking water standard for six per- and polyfluoroalkyl substances (PFAS) in the latest action under EPA’s PFAS Strategic Roadmap. The proposed National Primary Drinking Water Regulation (NPDWR) would regulate perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) as individual contaminants and will regulate four other PFAS — perfluorononanoic acid (PFNA), perfluorohexane sulfonic acid (PFHxS), perfluorobutane sulfonic acid (PFBS), and hexafluoropropylene oxide dimer acid (GenX chemicals) — as a mixture. Publication of the proposed rule in the Federal Register will begin a 60-day comment period. EPA held an informational webinar on March 16, 2023, and will hold another on March 29, 2023, and a public hearing on May 4, 2023.

EPA’s fact sheet states that EPA will propose:

  • An enforceable maximum contaminant level (MCL) for PFOA and PFOS: EPA will propose to regulate PFOA and PFOS at a level that “can be reliably measured, which is 4 parts per trillion” (4.0 nanograms/liter (ng/L));
  • An enforceable limit on a combination of PFNA, PFHXs, PFBS, and GenX chemicals: The proposed rule would place limits on any mixture containing one or more of PFNA, PFHxS, PFBS, and/or GenX chemicals. According to EPA, for these PFAS, water systems would use an approach called a hazard index, defined in the proposed rule and described later in this document, to determine if the combined levels of these PFAS pose a potential risk. EPA states that this approach protects communities from the additive effects of multiple PFAS when they occur together;
  • Monitoring: EPA will propose requirements for monitoring the six PFAS that build upon EPA’s long-established monitoring frameworks where monitoring frequency depends on previous results. EPA notes that its proposal also includes “flexibilities allowing systems to use some previously collected data to satisfy initial monitoring requirements”;
  • Public notification: Public water systems would be required to notify the public if monitoring detects these PFAS at levels that exceed the proposed regulatory standards; and
  • Treatment: Public water systems would be required take actions to reduce the levels of these PFAS in drinking water if they exceed the proposed regulatory standards. EPA states that “[t]his could include removing these chemicals through various types of treatment or switching to an alternative water supply that meets the standard.”

EPA has posted a pre-publication version of the proposed rule, as well as additional supporting materials and technical materials, on its web page for the proposed NPDWR. EPA held an informational webinar about the proposed PFAS NDPWR on March 16, 2023, and will hold another on March 29, 2023. EPA notes that the webinars will be similar, with each intended for specific audiences. Registration is required to attend.

EPA will make the webinar recordings and presentation materials available. EPA will also be holding a public hearing on May 4, 2023, where members of the public can provide verbal comments to EPA on the proposed rule. Registration is required to attend, and the last day to register to speak at the hearing is April 28, 2023.


The Acta Group (Acta®) applauds Administrator Michael S. Regan’s vision and leadership in addressing the PFAS challenges it faces. The issuance of the six PFAS national drinking water standards will ultimately assist with ensuring public health benefits to all individuals impacted by these substances in their water. We note that the proposed NPDWR also provides some insight on the direction EPA may take on cumulative risk assessment in other offices (e.g., the Office of Pollution Prevention and Toxics or OPPT), as well as on how EPA’s data collection authority under the Toxic Substances Control Act (TSCA) may aid with Agency-wide decision-making on PFAS. Below, we have provided some representative examples.

EPA stated that it “is proposing to use a Hazard Index (HI) approach to protecting public health from mixtures of PFHxS, HFPO-DA and its ammonium salt, PFNA, and PFBS because of their known and additive toxic effects and occurrence and likely co-occurrence in drinking water.” EPA also noted that it considered “the relative potency factor (RPF) approach, which represents the relative difference in potency of an effect/endpoint between an index chemical and other members of the mixture.” It opted against this approach, however, because of information gaps that may have precluded EPA from ensuring “that the MCLG [MCL goal] is sufficiently health protective.”

EPA’s policy choice, that is, to use the HI approach with PFAS under the Safe Drinking Water Act (SDWA), may shed some light on the direction from which OPPT receives comments, and toward which it may move, with its draft proposed principles of cumulative risk assessment under TSCA. OPPT noted that the Office of Pesticide Programs (OPP) “often uses the RPF” approach, whereas the Office of Land and Emergency Management (OLEM) “regularly uses the HI approach when evaluating multiple chemical substances in Superfund site risk assessments.”

The above distinction is no doubt related to the statutory data requirements placed on OPP registrants under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) versus the limited data available to OLEM when administering the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and to OPPT when administering TSCA. We recognize that OPPT has test order authority under TSCA Sections 4(a)(1)-(2), but OPPT’s use of this authority has been mired with legal challenges of late because of its ordering of testing that appears to be focused on data gaps, rather than data needs.

Moving forward, we anticipate more cross-office activities within EPA in a manner consistent with EPA’s PFAS Strategic Roadmap. For example, OPPT estimated that it will initiate “approximately 75 test orders per year … between [fiscal year] FY2023 and FY2025 … [a]pproximately 45 of these test orders are expected to be associated with the Agency’s actions on PFAS.” We expect that ordered testing under TSCA may ultimately inform EPA’s decisions on future revisions to the NPDWR and possibly expanding the category of PFAS regulated as a mixture. Further, the test orders may end up having requirements that go beyond EPA’s National PFAS Testing Strategy and include, for example, requirements for measuring releases from facilities that use PFAS.

The above examples illustrate the importance of tracking EPA’s proposed regulations across media, given the potential for cross-programmatic impacts. The proposed national drinking water standards may also provide a legal litmus test on whether EPA used the best available science when deriving these values, as required under SDWA, which may inform future interpretations of the scientific standards under TSCA. We mention this because of the anticipated lofty costs associated with ensuring compliance with the national drinking water standards, as well as the near certainty of litigation that will ensue.