U.S. EPA Outlines Next Steps to Vacate, Reconsider PFAS Drinking Water Rules?

The U.S. Environmental Protection Agency (EPA) is taking legal steps to address how it regulates certain per- and polyfluoroalkyl substances (PFAS). The action, initially announced on September 17, 2025, came after the agency asked the U.S. Court of Appeals for the D.C. Circuit on September 11, 2025, to partially vacate its 2024 drinking water PFAS maximum contaminant levels (MCLs) set by the rule for perfluorononanoic acid (PFNA), perfluorohexane sulfonic acid (PFHxS), and hexafluoropropylene oxide dimer acid (HFPO-DA), as well as for mixtures of these substances with perfluorobutane sulfonic acid (PFBS).

According to the EPA, the agency under the Biden administration used the wrong sequence to create the MCLs for PFAS under the Safe Drinking Water Act. The agency argues the statute requires a preliminary regulatory determination followed by a comment period before a final determination is made and a regulation is proposed. Claiming it proposed and finalized the PFAS rules at the same time it proposed the standards, the EPA, under Administrator Lee Zeldin, is now urging a federal court to strike down the PFAS regulations on these procedural grounds.

In a statement to 3E, the EPA explained its position, stating, “[The agency] is committed to protecting public health by addressing PFAS in drinking water while following the law and ensuring that regulatory compliance is achievable for drinking water systems.”

The EPA added that its court filing represents its intent to defend the drinking water regulations for perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), which the agency says were developed according to the statute’s proper sequence.

If the court vacates the rules, the EPA told 3E it would move forward with a proposed rulemaking to reconsider the regulations. While the agency said it cannot predetermine the outcome of this effort, it noted that the action “could result in a different outcome, including the potential for more stringent drinking water regulations for these PFAS in the future.”