On September 11, 2025, the U.S. Environmental Protection Agency (EPA) asked the United States Court of Appeals for the D.C. Circuit in American Water Works Ass'n v. EPA, Case No. 24-1188 (D.C. Cir.), to partially vacate its 2024 Rule regulating six per- and polyfluoroalkyl substances (PFAS) as drinking water contaminants. Although EPA initially defended the rule, the agency now asserts that portions of the rulemaking process violated the Safe Drinking Water Act (SDWA), rendering those parts of the rule invalid. Specifically, EPA requested that the court vacate its decisions to regulate three PFAS individually—PFNA, PFHxS, and HFPO-DA—and to regulate those three PFAS, along with PFBS, as mixtures through a hazard index (collectively, the Index PFAS). EPA also seeks to vacate the associated Maximum Contaminant Level Goals (MCLGs) and Maximum Contaminant Levels (MCLs). Notably, EPA is not asking the court to vacate the portions of the Rule related to PFOA and PFOS.
EPA's motion for vacatur presents a question of statutory interpretation. The agency contends that its process for setting MCLs for the Index PFAS was unlawful because it proposed MCGLs and MCLs for the Index PFAS concurrently with its preliminary decision to regulate the Index PFAS. According to EPA, this procedural shortcut violated Section 1412 of the Safe Drinking Water Act, 42 U.S.C. § 300g-1, by bypassing a statutorily required notice-and-comment period.
But EPA's new position does not necessarily control the outcome of the litigation. Several groups have intervened and will respond to EPA's motion by September 26, 2025. And in the wake of Loper Bright Enterprises v. Raimondo, 603 U.S. 369 (2024), it is unclear how much weight the court will afford EPA's interpretation of Section 1412. Further, as EPA recognizes in its brief, the court must also consider the seriousness of the agency's error and the disruptive consequences of an interim change in deciding whether to vacate the Rule. See Allied–Signal, Inc. v. Nuclear Regulatory Commission, 988 F.2d 146, 150–51 (D.C. Cir. 1993). It is unclear how the court may balance these considerations in the event it determines EPA's rulemaking process for the Index PFAS was unlawful.
That said, as noted in the June 2025 issue of Material Concerns, EPA previously announced plans to withdraw federal regulations concerning the Index PFAS. Accordingly, even if the court denies EPA's motion, the agency may pursue alternative avenues—such as new rulemaking—to eliminate these standards. As a result, uncertainty surrounding the regulation of the Index PFAS is likely to persist for the foreseeable future.
As mentioned, EPA is not seeking to vacate MCLs for PFOA and PFOS. Relatedly, on September 17, 2025, in Chamber of Commerce v. EPA, Case No. 24-1193 (D.C. Cir.), EPA stated that it will defend a 2024 Rule designating PFOA and PFOS as hazardous substances under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). In a news release that same day, EPA Administrator Lee Zeldin reaffirmed the agency's commitment to regulating PFOA and PFOS. Zeldin went further in calling for "new statutory language from Congress to fully address [EPA's] concerns with passive receiver liability." The news release also stated that EPA will adopt a "Framework Rule" to provide a "uniform approach to guide future hazardous substance designations." Accordingly, manufacturers, users, and dischargers of PFOA and PFOS should expect ongoing compliance obligations under the SDWA and CERCLA. Moreover, if Congress acts on EPA's request, these entities may face heightened liability risks under an updated statutory framework.
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