D.C. Circuit Affirms PFOA and PFOS Hazardous Substance Designation Under CERCLA

On August 18, the U.S. Court of Appeals for the District of Columbia Circuit (D.C. Circuit) issued its decision in Chamber of Commerce v. EPA, No. 24-1193 (D.C. Cir. Aug. 18, 2026), upholding the U.S. Environmental Protection Agency’s (EPA) formal designation of two per- and polyfluoroalkyl substances (PFAS)—perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS)—as “hazardous substances” under the federal Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). Pending a potential appeal to the U.S. Supreme Court, the D.C. Circuit’s opinion cements PFOA and PFOS as CERCLA hazardous substances, including for remedial and removal actions and cost recovery and contribution litigation under CERCLA.

Background

In May 2024, EPA promulgated a final rule establishing PFOA and PFOS—two of the most common PFAS—as hazardous substances under CERCLA § 102(a), 42 U.S.C. § 9602(a). See Chamber of Commerce, No. 24-1193, slip op. at 4. Prior to that designation, EPA had regulated PFOA and PFOS as “pollutants or contaminants” under CERCLA. Id. at 7. EPA used two factors to determine PFOA and PFOS were hazardous substances: (1) potential harm to humans or the environment from exposure and (2) environmental fate and transport. Id. at 8. According to EPA, its decision to designate PFOA and PFOS as hazardous substances stemmed from research on their adverse health effects as well as their tendency to persist in the environment and bioaccumulate. Id. at 9. Based on those considerations and a cost-benefit analysis, referred to as a “Regulatory Impact Analysis (RIA),” EPA determined that PFOA and PFOS satisfied CERCLA § 102(a)’s standard for designation as hazardous substances. Id. at 8–9.

Analysis

The U.S. Chamber of Commerce and other interest groups challenged the EPA’s designation, arguing that (1) EPA applied too low a threshold for deciding when a compound “may present substantial danger” by requiring only a mere possibility of serious harm, rather than the actual occurrence of such harm upon release; (2) EPA’s RIA, first disclosed with the final rule, violated the federal Administrative Procedures Act (APA) notice requirements under 5 U.S.C. § 553(b)(3); and (3) EPA’s cost-benefit analysis and decision to continue regulation of PFOA and PFOS were arbitrary and capricious in light of acknowledged uncertainty in the scientific community as to the compounds’ hazards. Id. at 12. The D.C. Circuit rejected each argument.

With respect to the “substantial danger” requirement, the court held that CERCLA permits designation of compounds as hazardous substances based on a scientifically supported possibility of substantial harm rather than absolute certainty. Applying Loper Bright, the D.C. Circuit independently interpreted and applied CERCLA § 102(a), which authorizes EPA to designate as “hazardous substances” those compounds that, when released, “may present substantial danger” to “public health, welfare, or the environment.” Id. at 4, 11–12, 15; see also 42 U.S.C. § 9602(a). The court determined that, in the context of this CERCLA provision, the term “may” only requires EPA to conclude that there is the possibility of substantial danger from a particular compound, as opposed to absolute certainty of such danger. Chamber of Commerce, No. 24-1193, slip op. at 13–15. The court reasoned that this contingency is assessed at the time of the release, meaning “the statute directs EPA to forecast the future risk of harm at the time of a release” so that harm need not be certain at the time of the release. Id. at 14.

The court also concluded that EPA’s power to designate hazardous substances is not unlimited, as the requirement that a compound present a risk of “substantial danger” requires that the potential harm be serious and real, not merely imagined or hypothetical, which limits EPA’s authority. Id. at 15–16. That said, the court declined to define the boundaries of the substantial danger standard because there was no dispute “that PFOA and PFOS qualify as substances that may pose a substantial risk to public health, welfare, and the environment if released[.]” Id. at 16. The court also rejected arguments that CERCLA does not allow for substances like PFOA and PFOS to originally qualify as pollutants or contaminants and then later be designated as hazardous substances. Id. at 19. The court further rejected arguments that EPA’s designation violated the nondelegation and void-for-vagueness doctrines. Id. at 20.

As for compliance with the APA’s notice provisions, the court held that EPA’s RIA was a logical outgrowth of the proposed rule and the Economic Assessment that accompanied it. Id. at 23–24.

Finally, the court held that, in performing its cost-benefit analysis, EPA need only complete a reasonable record-based examination of the costs and benefits of regulating a compound. Id. at 23, 35–36, 51–52. The D.C. Circuit thus upheld EPA’s economic analysis, crediting EPA’s cost estimates, industry impact assessment, and rejection of competing estimates, and accepted that shifting cleanup costs to responsible parties was a legitimate benefit. Id. at 34–35, 41–42. The court also rejected claims of arbitrary action amid uncertainty, emphasizing that designation alone triggers neither cleanup requirements nor liability. Id. at 45–46. According to the court, CERCLA response actions remain discretionary and site-specific, subject to investigation, prioritization, and statutory defenses. Id. at 46–51. Given these safeguards, the court concluded that EPA reasonably proceeded with the designation despite unpredictable future costs. Id. at 51–52.

Potential Implications

When PFOA and PFOS were designated only as CERCLA pollutants and contaminants, EPA’s ability to enforce cleanup requirements and potentially responsible parties’ (PRPs) ability to seek cost recovery and contribution under CERCLA were significantly limited. At that time, the applicable CERCLA provision was Section 104, which typically resulted in PFOA and PFOS cleanups being publicly funded. Id. at 5. EPA’s hazardous substance designation, now upheld by the D.C. Circuit, implicates CERCLA § 106, which means that EPA can now compel responsible parties to remediate PFOA and PFOS contamination, and EPA and other PRPs may institute CERCLA litigation to recover related costs under Sections 107 and 113. Id. at 5, 10; see 42 U.S.C. §§ 9606(a), 9607; see also 40 C.F.R. §§ 300.410, 300.420.

In light of state-level regulation, private entities have been dealing with the implications of PFAS and PFAS contamination for some time. But the CERCLA designation, affirmed on court review, likely invites a new deluge of litigation and federal cleanup requirements. Regulated entities would be well advised to review their portfolios and prepare for such risks to the greatest extent possible.

For more information on PFAS, CERCLA, and remediation matters, please contact the authors of this client alert.