The US Court of Appeals for the DC Circuit denied consolidated industry petitions challenging the Environmental Protection Agency’s 2024 designation of PFOA and PFOS as hazardous substances.
The ruling, handed down on 18 August 2026, leaves the designation fully in place, along with its release-reporting requirements and potential Superfund liability consequences for affected businesses.
Industry petitioners had advanced three separate grounds in support of vacating the rule, and the Court rejected all three, ultimately deferring to the EPA’s regulatory expertise.
The first challenge argued that the EPA exceeded its statutory authority in interpreting the phrase “may present substantial danger” within CERCLA’s definition of a hazardous substance.
The Court found that this language denotes uncertainty, meaning the EPA must only show a scientifically possible substantial risk of harm upon release, provided that risk remains serious and real rather than hypothetical.
The Court also noted that PFOA and PFOS have repeatedly been linked to adverse health effects in peer-reviewed studies, supporting the EPA’s authority to act under CERCLA’s plain statutory language.
On the second ground, petitioners contended that the EPA violated the Administrative Procedure Act by only disclosing its final Regulatory Impact Analysis when it issued the final designation, denying a separate public comment opportunity.
The Court applied the logical-outgrowth standard and found the notice requirement satisfied, because EPA’s proposed rule and earlier Economic Assessment had specifically sought comment on whether and how costs should be considered.
The third challenge claimed the EPA acted arbitrarily and capriciously in conducting its cost-benefit analysis, but the Court applied deferential review and held that the EPA reasonably evaluated costs, benefits, and acknowledged uncertainties on the record.
Notably, the Court found that the EPA’s conclusion that adding PFOA and PFOS to a list of more than 800 existing hazardous substances would produce only “marginal” costs was reasonable, given that infrastructure may already be in place at most National Priorities List sites.
That conclusion directly conflicts with the widely recognised understanding that the designations will add substantial investigative and remediation costs, as well as significant new liabilities for entities not previously exposed to CERCLA obligations.
The designation will also add costs to real estate and corporate transactions that must now evaluate potential liability for properties on which PFOA or PFOS have been released.
The ruling reinforces the EPA’s authority to deploy CERCLA’s existing response and cost-recovery framework to address per- and polyfluoroalkyl substances, commonly known as PFAS, across a wide range of industrial contexts.
Companies that manufacture, use, transport, recycle, manage, or dispose of materials containing PFOA or PFOS should now urgently evaluate their material management and disposal practices to mitigate and avoid further CERCLA liability.
Businesses should also review their past practices, including potential insurance claims, and consider switching to alternative substances to limit exposure to future regulatory action and litigation risk.