EPA’s PFAS Hazardous Substance Designation Survives Challenge

In the latest step of federal regulation of so-called “forever chemicals” known as per- and polyfluoroalkyl substances (PFAS), the U.S. Court of Appeals for the D.C. Circuit has denied industry challenges to EPA’s 2024 designation of PFOA (perfluorooctanoic acid) and PFOS (perfluorooctanesulfonic acid) as “hazardous substances” under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). The decision affirms EPA’s authority to regulate these chemicals based on their link to serious health conditions and persistence in the environment but also helps set the stage for other regulatory actions addressing PFAS.

Background

PFOA and PFOS are human-made chemicals that have been used in the United States since the 1940s to create water- and oil-resistant products like cookware, rain-repellent clothing, and firefighting foam. Given their wide-ranging uses, they are fairly ubiquitous in many environmental media, even if at low concentrations. 

EPA issued a final rule designating PFOA and PFOS as hazardous substances in May 2024, triggering additional reporting requirements, cleanup obligations, and cost-recovery mechanisms under CERCLA associated with their releases into the environment. Industry groups then petitioned the D.C. Circuit for review of EPA’s final regulation, arguing that EPA (1) misinterpreted CERCLA’s “may present substantial danger” standard, (2) failed to provide adequate notice of its cost-benefit analysis, and (3) acted arbitrarily by regulating despite uncertainties about future cleanup costs.

The Court’s Analysis

Quoting CERCLA, the court noted that “CERCLA authorizes EPA to designate as additional ‘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.’” The court then rejected petitioners’ argument that the clause “may present substantial danger” requires certainty of harm upon release, holding that “may” carries its plain meaning of contingency or possibility and that requiring absolute scientific certainty “would have been to legislatively paralyze CERCLA.” In addition, the court found compelling the scientific evidence of such risk of substantial danger supporting EPA’s regulatory action.

The court also held that EPA’s final Regulatory Impact Analysis was a “logical outgrowth” of the Economic Assessment published with the proposed rule and so was duly noticed to the public. It found that EPA’s cost-benefit methodology was reasonable, giving deference to the agency’s technical expertise in estimating cleanup costs. The court also upheld EPA’s treatment of cost-shifting from taxpayers to polluters as an “advantage” of the designation, consistent with CERCLA’s core purpose to ensure cleanup costs are “borne by those responsible for the contamination.”

The court summarily rejected petitioners’ nondelegation and void-for-vagueness arguments, holding that Congress provided an “intelligible principle” by requiring EPA to regulate substances that may present “substantial danger” to public health – a standard satisfied by linking agency decisions to scientific findings. 

Key Takeaways

As we have discussed in our prior articles addressing this EPA action (linked here and here), the designation of PFOA and PFOS as hazardous substances means CERCLA’s liability of potential responsible parties for releases of hazardous substances is applicable to PFOA and PFOS. As the court noted, however, CERCLA’s narrow defenses to such liability still remain where applicable. In addition, under CERCLA, parties releasing more than one pound of either PFOA or PFOS must report such a release to national authorities.

Beyond CERCLA’s immediate scope, though, designation as a hazardous substance can also trigger obligations under other regulatory programs. For example, such designation yields labelling and other duties under the Hazardous Materials Transportation Act for shipments of PFOA and PFOS in amounts exceeding one pound. As we reported in May 2024, EPA has already included certain PFAS compounds in the list of chemicals subject to Toxic Release Inventory reporting under the Emergency Planning and Community Right to Know Act. It could also lead to regulation of PFOA and PFOS as pollutants under the Clean Water Act (CWA). Indeed, certain states are already leaning into studies and regulation of certain PFAS as pollutants under CWA and state wastewater discharge permits, including monitoring of PFAS in industrial wastewater discharges to publicly owned treatment works (POTWs). (See, for example, North Carolina’s efforts and Virginia’s efforts in this regard.) As a hazardous substance, PFOA and PFOS may also qualify as hazardous waste under the Resource Conservation and Recovery Act. Despite these regulatory program implications presented by the hazardous substance designation, EPA has nonetheless proposed certain exemptions for PFAS under the Toxics Substances Control Act, as we discussed in a prior article.

Given the D.C. Circuit’s decision, EPA’s designation of PFOA and PFOS as hazardous substances will stand, barring reversal on rehearing before the full D.C. Circuit panel or on appeal to the U.S. Supreme Court. The decision also supports the increasing trend of regulation of certain PFAS in different regulatory programs. Affected industry should therefore evaluate their reporting obligations and potential exposure under CERCLA’s liability framework for past and present PFOA and PFOS uses and releases. They should also consider other regulatory obligations for any new or ongoing management, releases or discharges of PFOA and PFOS arising from this designation.

Chamber of Commerce of the United States of America v. EPA, No. 24-1193 (D.C. Cir. August 18, 2026)