On Sept. 11, 2025, the Environmental Protection Agency (EPA) asked the D.C. Circuit Court of Appeals to vacate the agency’s own drinking water standards (MCLs) for four PFAS chemicals: PFNA, PFHxS, HFPO-DA, and (through a “hazard index”) PFBS (referred to collectively as the “Index PFAS”). EPA is now apparently siding with the group of petitioners that are challenging the PFAS National Primary Drinking Water Regulation, which was promulgated in 2024 during the Biden administration. EPA is now claiming that the portion of the rulemaking process that resulted in the MCLs for the Index PFAS was procedurally improper, and that, as a result, the standards are invalid. EPA is continuing to defend the challenges to the portion of the rule that sets MCLs for the two most prevalent PFAS, PFOA and PFOS.
The alleged defect in the process for setting MCLs for the Index PFAS was EPA’s decision to propose goals and standards for those chemicals concurrently with its preliminary determination that they should be regulated. EPA is now alleging that Section 1412 of the Safe Drinking Water Act (SDWA), 42 U.S.C. § 300g-1, requires EPA to propose to regulate a new contaminant – and consider comments on such a proposal – before it may publish even proposed drinking water standards.
EPA’s latest pronouncement against this portion of its own rule is not a complete surprise. In May of this year, EPA issued a press release “announcing its intent to rescind the regulations and reconsider the regulatory determinations for [the Index PFAS].” The press release did not, however, indicate that EPA would attempt to use the pending court challenges as the vehicle to eliminate the Index PFAS MCLs.
EPA’s latest position in the litigation does not necessarily mean the Circuit Court will vacate the Index PFAS MCLs. A number of entities, including the Natural Resources Defense Council (NRDC), had previously intervened in the consolidated challenges to the PFAS standards on behalf of EPA. The intervenors have supported the rule separately from EPA and, according to EPA’s brief, intend to respond to EPA’s change-of-position on this issue. Furthermore, following the Supreme Court’s decision last year in Loper Bright Enters. v. Raimondo, 603 U.S. 369, 412-13 (2024), EPA may no longer be entitled to Chevron deference for its interpretation of the SDWA and what is required and prohibited by Section 1412. Accordingly, it is not clear how much EPA’s new legal interpretation will affect the outcome of the litigation.
Further, a finding that the proper procedure was not followed would not automatically compel the court to vacate the rule. EPA’s brief acknowledges that when determining whether to vacate a rule, the court should consider both “the seriousness of the order’s deficiencies…and the disruptive consequences of an interim change that may itself be changed” (Allied-Signal, Inc. v. Nuclear Regulatory Commission, 988 F.2d 146, 150-51) (D.C. Cir. 1993).) Given that the MCLs do not need to be met until 2029, vacating them at this stage is unlikely to be found to be disruptive. But there may be questions about whether the sequencing of the EPA’s actions was seriously deficient.
If EPA is unable to have the Index PFAS MCLs vacated, it could pursue the same result through a rulemaking process. Accordingly, many are now arguing that it appears increasingly unlikely that drinking water providers will ever have to comply with the Index PFAS MCLs.
For further information regarding PFAS MCLs, contact a member of Taft’s Environmental group.