Two major water industry groups are asking a federal appeals court to send the U.S. Environmental Protection Agency’s (EPA) new PFAS drinking water rule back for further review, arguing the agency overstepped both science and statutory limits.
In a reply brief filed in the U.S. Court of Appeals for the D.C. Circuit, the American Water Works Association and the Association of Metropolitan Water Agencies contend that the EPA “acted with disregard for the science and law when it promulgated the Rule.”
At the centre of the dispute is the EPA’s decision to regulate several “Index PFAS” — including PFHxS, PFNA, PFBS and HFPO-DA — and to establish maximum contaminant levels and health goals before, the groups argue, completing the formal determinations required under the Safe Drinking Water Act.
The associations say that approach “violated the Act’s carefully prescribed standard-setting processes,” noting that the EPA later sought partial vacatur of parts of the rule after filing its initial brief. They argue the alleged error is “fatal” and are asking the court to vacate both the determinations to regulate and the resulting contaminant limits.
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The brief also challenges the EPA’s justification for regulating certain PFAS compounds and mixtures on a national basis. Under federal law, the agency must find a “substantial” likelihood that a contaminant occurs in drinking water “with a frequency and at levels of public health concern.” The groups argue the EPA relied on limited state data and older federal monitoring results to meet that threshold.
Beyond the legal process, the associations take aim at the EPA’s economic analysis, arguing the agency “oversold the benefits and undersold the true costs” of the regulation. They contend the cost-benefit analysis improperly relied on non-quantifiable benefits and underestimated compliance costs for water systems.
The case now before the D.C. Circuit will determine whether the PFAS drinking water standards remain in place as written or are sent back to the EPA for further action.
In May 2025, the EPA announced that it would reevaluate regulatory drinking water limits for types of PFAS known as GenX (PFHxS, PFNA and HFPO-DA), but will maintain limits and extend compliance deadlines set for PFOA and PFOS, two of the more common forms of the “forever chemicals”.
