D.C. Circuit Upholds EPA Rule Designating PFOA and PFOS as CERCLA Hazardous Substances

What Happened

On August 18, 2026, the U.S. Court of Appeals for the D.C. Circuit denied petitions for review of a 2024 U.S. Environmental Protection Agency (EPA) rule designating perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) as “hazardous substances” under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). Chamber of Com. of the U.S. v. EPA, No. 24-1193 (D.C. Cir. Aug. 18, 2026). The decision leaves EPA’s designation in place.

Background

CERCLA Section 102(a) directs EPA to designate as hazardous substances those "elements, compounds, mixtures, solutions, and substances" that, when released into the environment, "may present substantial danger to the public health or welfare or the environment." 42 U.S.C. § 9602(a).

In May 2024, EPA issued a final rule designating PFOA and PFOS as hazardous substances under Section 102(a). The designation triggers certain reporting and other regulatory requirements and can also support CERCLA response and cost-recovery actions, as well as related contribution litigation among potentially responsible parties, depending on site-specific circumstances.

Seven industry groups petitioned for review, arguing that EPA misinterpreted Section 102(a)’s “may present substantial danger” standard, failed to provide adequate notice under the Administrative Procedure Act, and acted arbitrarily and capriciously in its cost-benefit analysis and in proceeding despite uncertainties concerning the designation’s costs and other consequences.

The D.C. Circuit's Decision

The D.C. Circuit rejected those challenges. Applying Loper Bright Enterprises v. Raimondo, the court independently interpreted CERCLA Section 102(a), without deferring to EPA’s reading. It concluded that the statutory term “may” refer to the possibility of substantial danger, not a requirement for certainty that substantial danger will result from a release. However, the court emphasized that “substantial danger” limits EPA’s authority by requiring that the risk be “serious and real, not hypothesized.” The court also noted that petitioners did not dispute EPA’s finding that PFOA and PFOS may pose a substantial risk to public health, welfare, or the environment if released.

The court also rejected petitioners’ nondelegation and vagueness arguments. It concluded that Section 102(a) provides an intelligible principle by requiring EPA to determine that a substance may present “substantial danger” to public health, welfare, or the environment, and that the statute gives regulated parties a reasonable opportunity to predict whether a substance may be designated hazardous.

Turning to EPA’s cost-benefit analysis, the court held that EPA provided adequate notice. Although EPA issued a more detailed Regulatory Impact Analysis with the final rule, the court concluded that it was a logical outgrowth of EPA’s earlier Economic Assessment and the notice-and-comment process. The court also found that EPA reasonably explained its quantitative analyses and rejected petitioners’ challenges to EPA’s treatment of potential cleanup costs and industry impacts.

Finally, the court rejected petitioners’ argument that uncertainties concerning future cleanup costs and potential CERCLA liability rendered the designation arbitrary and capricious. The court emphasized that CERCLA response actions are “discretionary, contingent, and site-specific determinations” and that the designation itself does not determine whether cleanup will be required at a particular site or whether a particular party will face liability. On that basis, the court concluded that EPA reasonably proceeded with the designation despite those uncertainties and therefore denied the petitions for review.