Key Points

• The EPA moved to partially repeal its regulation of PFNA, PFHxS, HFPO-DA, and PFBS under the Safe Drinking Water Act.
• But the EPA will continue to defend its regulation of PFOA and PFOS under the Safe Drinking Water Act.
• The EPA also announced it was retaining its designations of PFOA and PFOS as “hazardous substances” under CERCLA.

On Sept. 11, 2025, the U.S. Environmental Protection Agency announced in a court filing that it was moving to partially vacate its National Primary Drinking Water Regulation for four per- and polyfluoroalkyl substances (PFAS): PFNA, PFHxS, HFPO-DA, and PFBS. (Am. Water Works Assn. and Assn. of Metro. Water Agencies v. EPA et al., D.C. Circuit Court of Appeals Case No. 24-1188). As we previously explained, this rule set maximum contaminant levels for six PFAS, including PFOA and PFOS, which, if left in place, would lead to new monitoring, reporting, and treatment requirements for public water systems.

In its motion, the EPA conceded that it failed to provide an opportunity for public comment before issuing its regulatory determination for these four substances. At the same time, however, the EPA reiterated its intent to continue defending its drinking water regulation of PFOA and PFOS.  

A few days later, the EPA announced that it was retaining its designation of PFOA and PFOS as “hazardous substances” under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). For the last nine months, the EPA has been considering whether to repeal its “hazardous substance” regulation. As we previously explained, designating PFOA and PFOS as “hazardous substances” under CERCLA could impose strict liability for certain costs to clean up and remove PFOA and PFOS contamination. The EPA’s press release acknowledged concerns over how this designation may impose liability on “passive receivers” like water suppliers and wastewater operators, which may have neither manufactured nor generated these substances.

Once again, these recent PFAS updates further reflect the complex and developing regulatory landscape for public water suppliers, wastewater treatment operators, manufacturers, farmers, among others.