EPA Faces D.C. Court Oral Arguments on PFAS Drinking Water Rules
Oral arguments on EPA's PFAS drinking water rules began August 24, 2026, in D.C. Circuit.
Why it matters: Legal and compliance teams must watch these proceedings, as final EPA rules will shape toxic chemical regulation and corporate liabilities tied to PFAS contamination.
- EPA proposed keeping PFOA and PFOS Maximum Contaminant Levels (MCLs) at 4 parts per trillion on May 18, 2026.
- Public water systems can request up to two extra years until 2031 to comply with these MCLs, per EPA’s proposal.
- EPA seeks to withdraw PFHxS, PFNA, GenX chemicals, and a related Hazard Index rule citing procedural errors.
- The D.C. Circuit on August 18, 2026, upheld EPA’s authority to classify PFOA and PFOS as hazardous substances under CERCLA.
Oral arguments commenced on August 24, 2026, before the U.S. Court of Appeals for the D.C. Circuit, focusing on the Environmental Protection Agency’s (EPA) new regulatory proposal for per- and polyfluoroalkyl substances (PFAS) in drinking water. This hearing follows EPA’s May 18, 2026 announcement to retain the Maximum Contaminant Levels (MCLs) for PFOA and PFOS at 4.0 parts per trillion (ppt), concentrations considered by the agency to protect public health.
The EPA’s framework allows public water systems to apply for a compliance extension, granting up to two additional years—extending the deadline to 2031. The agency stresses the extension facilitates practical implementation without weakening standards. The term “Hazard Index” referenced by EPA measures cumulative risk from multiple PFAS chemicals combined, guiding regulatory limits for mixtures.
EPA also proposes rescinding rules for four other PFAS—perfluorohexane sulfonic acid (PFHxS), perfluorononanoic acid (PFNA), hexafluoropropylene oxide dimer acid (GenX chemicals), and the related Hazard Index—citing procedural irregularities during rulemaking, as noted in the agency’s public documents. This rescission corrects procedural defects; EPA intends to reassess these PFAS to determine appropriate future regulation.
The public comment period closed on July 20, 2026, after a July 7 virtual hearing where stakeholders provided input. The court’s August 18 ruling affirmed EPA’s authority to designate PFOA and PFOS as hazardous substances under CERCLA, solidifying federal enforcement power, per the D.C. Circuit opinion.
These developments carry substantial implications for corporate compliance related to drinking water safety. Legal teams within affected industries should monitor these ongoing court and regulatory actions closely, as they will influence environmental risk management, liability exposure, and operational adjustments tied to PFAS contamination controls.
By the numbers:
- 4 ppt — EPA’s proposed MCL for PFOA and PFOS announced May 18, 2026
- July 20, 2026 — Close of public comment period on EPA’s proposal
- August 18, 2026 — D.C. Circuit affirmed EPA’s CERCLA hazardous substance designation
Yes, but: While EPA proposes rescinding some PFAS regulations due to procedural errors, it has not abandoned regulatory oversight; review and new rulemaking remain pending.
What's next: The D.C. Circuit is expected to issue a decision on the EPA PFAS rules within the next several months, influencing future EPA regulatory actions.