PFAS Litigation Update: D.C. Circuit Upholds EPA Hazardous Substance Designation

The U.S. Court of Appeals for the District of Columbia Circuit on Aug. 18 upheld the Environmental Protection Agency’s 2024 designation of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) as “hazardous substances” under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) in Chamber of Commerce of the United States of America v. EPA, No. 24-1193 (D.C. Cir.).

Writing for a unanimous panel, Judge Patricia Millett rejected challenges brought by several industry trade associations, including the U.S. Chamber of Commerce, the American Chemistry Council, and organizations representing manufacturing and waste-management interests, which argued that EPA exceeded its statutory authority, failed to provide adequate notice regarding its cost-benefit analysis, and acted arbitrarily by proceeding despite significant uncertainty surrounding the rule’s economic impacts.

In May 2024, EPA finalized a rule designating PFOA and PFOS as CERCLA hazardous substances (See related article: 2024 CERCLA Designation; 2023 CERCLA Designation). The designation carries several regulatory consequences, including release reporting requirements, transportation-related obligations, notice requirements for contaminated federal property, and the potential for future cleanup and cost-recovery actions under CERCLA.

Shortly after the rule was promulgated, a coalition of industry groups petitioned the D.C. Circuit for review. In February 2025, the court granted EPA’s request to hold the litigation in abeyance while the incoming presidential Administration reviewed the designation. In September 2025, EPA announced that it would retain the hazardous-substance designation for PFOA and PFOS and continue defending the rule in court.

The issue central to this litigation involved CERCLA Section 102(a), which authorizes EPA to designate substances that, when released into the environment, “may present substantial danger to the public health or welfare or the environment.” The petitioners contended that EPA could designate a substance as hazardous only if substantial harm was certain or highly likely to occur. The court disagreed, holding that the ordinary meaning of the word “may” encompasses the possibility of substantial harm rather than certainty. The court emphasized that CERCLA is a preventative environmental statute intended to address risks before harm becomes inevitable, and that requiring scientific certainty would undermine Congress’s objective of protecting public health and the environment.

Additionally, the petitioners argued that EPA’s interpretation raised constitutional concerns under the nondelegation doctrine and due process principles because the statutory standard was allegedly too vague. The court rejected those arguments, finding that Congress supplied an adequate “intelligible principle” by limiting EPA’s authority to substances that may present a substantial danger to public health, welfare, or the environment. The court further noted that environmental statutes frequently require agencies to exercise scientific and risk-based judgment, and that similar statutory standards have repeatedly been upheld by the Supreme Court.

Another recurring theme throughout the challenge was the claim that EPA lacked sufficient information regarding the location and extent of PFAS contamination, the future costs of cleanup, and the scope of potential liability resulting from the designation. The court acknowledged these uncertainties but concluded that EPA had thoroughly considered them and reasonably determined that regulatory action was nevertheless warranted.

In reaching that conclusion, the court emphasized the numerous procedural safeguards built into CERCLA before any cleanup liability may be imposed. These safeguards include site investigations, risk assessments, public comment opportunities, cost-effectiveness evaluations, liability defenses, and settlement mechanisms. As a result, the court rejected the petitioners’ contention that the designation itself automatically imposes significant liability or immediate cleanup obligations. Instead, any future enforcement actions will depend on extensive site-specific analyses and multiple additional regulatory steps.

The decision confirms EPA’s authority under CERCLA Section 102(a) to designate substances as hazardous where the agency determines that their release may present a substantial danger to public health, welfare, or the environment. It also reflects the court’s willingness to uphold EPA’s reasoned decision-making in the PFAS context, particularly where the agency acknowledges regulatory uncertainty but provides a well-supported explanation for precautionary action.

For regulated industries, the ruling confirms that PFOA and PFOS remain subject to CERCLA’s hazardous-substance framework, increasing the potential for reporting obligations, investigations, cleanup actions, and liability exposure.

For additional information regarding the continuously evolving PFAS litigation landscape, explore the following PFAS-focused articles: