EPA Asks Court To Partially Vacate Rule Regulating PFAS In Drinking Water

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.