EPA Seeks Vacatur of Majority of Biden-Era PFAS Regulations under the Safe Drinking Water Act - A Sign of More to Come?

On September 11, 2025, the Environmental Protection Agency (EPA) asked the D.C. Circuit to vacate regulations for four types of polyfluoroalkyls (known collectively as “PFAS”) in drinking water. The motion for partial vacatur marks a significant reversal in the agency’s policy, as the EPA had previously vigorously defended legal challenges to the first-of-their-kind standards in federal court for the past two years. See American Water Works Association, et al. v. EPA, case no. 24-1188 and consolidated cases (D.C. Cir. filed June 7, 2024). Just this month, the case was given the green light to proceed, after being held in abeyance (at the request of both parties) so that the Trump administration could determine how it wished to proceed. The change signals a willingness on the part of the administration to act on previously issued non-legally binding announcements of forthcoming changes to Biden-era rules and may also serve as a harbinger for how the new administration will tackle PFAS under other statutes, such as the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA).

Last year, the Biden EPA issued a Final Rule under the Safe Drinking Water Act (SDWA) which, for the first time ever, set nation-wide maximum contaminant levels (MCLs) for six types of PFAS as drinking water contaminants. See PFAS National Primary Drinking Water Regulation, 89 Fed. Reg. 32532 (Apr. 26, 2024). The Final Rule included six types of PFAS, but in May of 2025, the Trump EPA announced its intention to rescind its regulatory determinations for PFHxS, PFNA, and HFPO-DA (commonly known as GenX), and for mixtures of those three and a fourth, PFBS. As Crowell previously reported, EPA also announced its intention to delay compliance with the Final Rule by two years (from 2029 to 2031).

True to its announcement, EPA told the Court on September 11, 2025, that it seeks partial vacatur of the rule, which includes:

1. Vacatur of EPA’s determination to regulate PFNA, PFHxS, and Gen-X individually, and mixtures of those three plus PFBS through a “hazard index”; and
2. Vacatur of the MCLs and Maximum Contaminant Level Goals set for those four PFAS.

EPA specified that it intends to continue defending the portions of the Final Rule governing PFOA and PFOS, “because the Agency’s actions for those contaminants—in contrast to actions related to the Index PFAS—adhered to the [SDWA’s] requirements.” For PFOA and PFOS, EPA says that it properly followed the required procedures contained in the SDWA. However, for the remaining four PFAS, EPA argues that it improperly issued its regulatory determination and Final Rule in tandem, which did not allow for the public to properly comment on and participate in the rulemaking process. According to the agency, vacatur of that portion of the rule, while the remaining PFOA and PFOS standards remain in place, is the proper action that the court should take.

The decision comes on the heels of the Trump Administration’s issuance of its first Unified Agenda, a semiannual public document which generally compiles all of the agency’s proposed, ongoing, and recently completed regulatory and deregulatory actions, and can serve as a “playbook” for actions to come. The September 2025 Agenda indicated EPA’s intention to propose a rule by October 2025 to codify its two-year grant of extension for water systems to comply with the two remaining PFAS MCLs, with a final rule is expected by April 2026. The final rule withdrawing regulatory determinations for the four remaining PFAS is anticipated in February 2026.

Notably absent from the Unified Agenda was the fate of a separate Final Rule, also issued in April 2024, designating PFOA and PFOS as hazardous substances under CERCLA. Similar to the SDWA Final Rule for PFAS, the CERCLA Final Rule was also challenged in federal court and subsequently held in abeyance while the new administration determined its regulatory priorities. See Chamber of Commerce et al. v. EPA, case no. 24-1193 (D.C. Cir. filed June 10, 2024). EPA now faces a September 17 deadline to let the D.C. Circuit know how it would like to proceed.

The EPA may choose to follow the same approach in the CERCLA Final Rule litigation as in the SDWA case. Plaintiffs in the CERCLA litigation, primarily comprised of industry stakeholder groups, have argued that the agency misinterpreted the law’s threshold bar that requires a showing of “substantial danger” for first-time listings of hazardous substances, and that the agency crafted a “fundamentally flawed” cost analysis. In this case, EPA could similarly request vacatur of the Final Rule and agree with Plaintiffs that it did not follow the proper procedures for rulemaking. The CERCLA Final Rule remains effective during the pendency of the litigation, but its fate remains more uncertain than ever.

Whether EPA chooses to defend the CERCLA Final Rule or argue against itself in favor of vacatur, the decision will have immediate impacts on litigation across the country. Crowell & Moring continues to track the evolution of the new administration’s regulatory approach towards PFAS.