On August 18, 2026, the U.S. Court of Appeals for the D.C. Circuit issued its decision in Chamber of Commerce of the United States of America v. EPA, denying all petitions for review and upholding EPA’s designation of PFOA and PFOS as hazardous substances under CERCLA.
As we previously reported, the petitioners argued that the designations should be overturned because EPA applied an overly expansive interpretation of “may present substantial danger” (a finding needed to designate a new hazardous substance), asserting that EPA’s cost-benefit analysis was inaccurate and was significantly modified without giving stakeholders an opportunity to comment on the revised version, and that EPA improperly proceeded despite significant scientific and regulatory uncertainty. The Court of Appeals rejected these arguments, finding that the phrase “may present substantial danger” was properly interpreted by EPA (applying the Loper Bright standard). It further held that the revised cost benefit analysis was not arbitrary and capricious and did not require additional notice and comment because it was a “logical outgrowth” of the prior version. The court also concluded that EPA reasonably explained its decision making in light of the scientific and regulatory uncertainties raised by the petitioners.
Petitioners may seek a rehearing en banc or file a petition for certiorari to the U.S. Supreme Court. Given the breadth of the industry coalition and the stakes involved, further appellate proceedings would not be surprising. In the meantime, the designations of PFOA and PFOS as hazardous substances remain in effect.