On August 18, 2026, a unanimous panel of the U.S. Court of Appeals for the D.C. Circuit upheld EPA’s designation of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) as hazardous substances under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA or Superfund). In Chamber of Commerce of the United States v. EPA, the court rejected challenges to EPA’s interpretation of CERCLA Section 102(a), the adequacy of its notice and comment process, its analysis of costs and benefits, and its decision to proceed despite uncertainty about future response actions and costs.

This decision is already being invoked in a separate D.C. Circuit challenge to EPA’s 2024 PFAS drinking water rule promulgated under the Safe Drinking Water Act (SDWA). Six days after the CERCLA decision, respondent intervenors cited it as supplemental authority in American Water Works Association v. EPA, No. 24-1188, ahead of oral argument scheduled for September 18, 2026. The Chamber of Commerce decision may assist the respondent intervenors on certain notice and comment and economic analysis arguments, but its significance should not be overstated. The principal challenges to the standards for the four PFAS subject to EPA’s Hazard Index-based maximum contaminant level (MCL) turn on requirements specific to the SDWA, and EPA itself now agrees that those provisions were promulgated through an unlawful process.

Reprinted courtesy of Ashleigh K. Myers, Pillsbury, Amanda G. Halter, Pillsbury and Jillian Marullo, Pillsbury

Ms. Myers may be contacted at ashleigh.myers@pillsburylaw.com
Ms. Halter may be contacted at amanda.halter@pillsburylaw.com
Ms. Marullo may be contacted at jillian.marullo@pillsburylaw.com