Yesterday, the United States Environmental Protection Agency (EPA) released proposed national drinking water standards for six per- and polyfluoroalkyl substances (PFAS) pursuant to the federal Safe Drinking Water Act (SDWA)—a key step towards establishing the first enforceable federal standard for PFAS. PFAS compounds have come to be known as “forever chemicals” because of their ability to indefinitely persist in the environment and toxicity at extremely low levels. EPA’s move is expected to profoundly affect treatment requirements for drinking water suppliers and remediation cleanup requirements across a wide swath of federal and state environmental programs.
If adopted, the proposed National Primary Drinking Water Regulation (NPDWR) would set legally enforceable individual Maximum Contaminant Levels (MCLs) for two of the best known PFAS compounds, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), at 4.0 parts per trillion (ppt). 4.0 ppt is understood as the current laboratory detection limit for PFOA and PFOS, and signals that EPA intends for the limits to be set at the most stringent possible level. If adopted at 4.0 ppt, the MCLs for PFOA and PFOS would be the most restrictive in the nation, and states and U.S. territories will be required to adopt MCLs at or below the same standard within two years.
EPA also proposes using a risk-based standard for mixtures of four additional PFAS compounds in drinking water: 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). For these compounds, the regulation would require use of a formula to determine if any mixture of these chemicals in drinking water, taken together, has a “Hazard Index” (HI) score of 1.0 or greater, which indicates potential risk of adverse health effects.
To understand how all three of these proposed standards would impact their operations, public water systems should immediately review past sampling results to determine whether they exceed the proposed limits. Public water systems should also begin planning and evaluating costs to comply, despite the lack of an immediate deadline to do so, with the proposed standards.
SDWA also requires the Administrator of the EPA to propose a maximum contaminant level goal (MCLG) simultaneously with the NPDWR. The MCLG is a non-enforceable public health goal that represents a level at which no known adverse health effects are expected to occur. Because EPA determined PFOA and PFOS are likely carcinogenic to humans, the agency proposes MCLGs of 0.0 ppt. The proposed MCLG for any mixture of PFNA, PFHxS, PFBS, and GenX Chemicals is HI 1.0.
The proposed rule is the latest in a series of actions EPA is taking to address PFAS pollution. In March 2021, pursuant to its “PFAS Strategic Roadmap: EPA’s Commitments to Action,” EPA issued a final determination to regulate PFOA and PFOS as contaminants under SDWA. As mandated by SDWA, the proposed rule comes 24 months after determination. Once published in the Federal Register, the public will have the opportunity to provide verbal or written comments to EPA on the proposed rule. Following the public comment period, EPA expects to issue the final regulation by the end of 2023. It is important for any entity that seeks to modify or influence the proposed standards to fully participate in EPA’s administrative process.
If adopted, in concert with EPA’s pending proposed rule to list PFOA and PFOS as hazardous substances under the federal Comprehensive Response, Compensation, and Liability Act (CERLCA), the MCLs for PFOA and PFOS may be expected to be adopted into remedial actions performed pursuant to CERCLA. In addition, in states and/or U.S. territories that employ federal and state MCLs as a driver for remediation cleanup standards, EPA’s promulgation of the MCLs for PFOA and PFOS may affect remedial activities required under state environmental remedial programs, such as state equivalents of CERCLA.
EPA is authorized to promulgate an NPDWR under SDWA based on its determination that these six PFAS may have adverse health effects, occur in public water systems with a frequency and at levels of public health concern, and that, in the sole judgment of the Administrator, their regulation presents a meaningful opportunity for health risk reduction for persons served by public water systems. EPA anticipates that, if fully implemented, the rule will prevent thousands of deaths and reduce tens of thousands of serious PFAS-attributable illnesses.
 In the proposed rule, EPA issues a preliminary regulatory determination to regulate PFNA, PFHxS, PFBS, and GenX Chemicals.
 SDWA 1412(a)(3); 42 U.S.C. 300g-1(a)(3).
 SDWA 1412(b)(1)(E); 42 U.S.C. 300g-1(b)(1)(E).
 EPA, in its proposal, specifically requests comment on whether water systems should be permitted to apply to the relevant state agency for monitoring waivers and whether the identification of possible alternatives to traditional vulnerability assessments should be considered to identify risk.
 SDWA 1412(b)(1)(A); 42 U.S.C. 300g-1(b)(1)(A).