On June 11, 2024, the NAM filed a petition in the D.C. Circuit challenging EPA’s final rule setting individual standards for six per- and polyfluoroalkyl substances (PFOA, PFOS, PFHxS, HFPO-DA, PFNA and PFBS) in municipal water systems. PFAS are a diverse group of chemicals essential to modern life, including in the transformers used to power electric grids; in the semiconductors and solar components needed for clean energy transition; and in the aircraft, munitions, fire suppression systems and communication devices required for national security. EPA’s new rule sets a “Maximum Contaminant Level” for each of the six substances at or near zero—equivalent to a few drops in an Olympic swimming pool. The standards are so low that full compliance may never be achieved—meaning PFAS manufacturers and users will be unable to obtain discharge permits. And as municipalities face the high costs of coming into compliance (an estimated $3.8B annually), water systems, state attorneys general and other stakeholders have, and will continue to, bring litigation against manufacturers to defray those costs. Enterprising plaintiffs’ lawyers have also started using the infeasible standards to assert toxic tort and personal injury suits against manufacturers.
In our opening brief, filed on October 7, 2024, we explain that in plowing ahead with its unattainable rule, EPA violated the express requirements of the Safe Drinking Water Act and engaged in arbitrary and capricious decision making in violation of the Administrative Procedure Act. The rule’s many deficiencies include:
• A deeply flawed cost-benefit analysis that combines costs and benefits for multiple substances into a group determination, ignores substantial costs raised by commenters and improperly relies on “nonquantifiable benefits” where it lacked empirical data;
• A woefully incomplete feasibility analysis that fails to grapple with whether the technology and facilities necessary for compliance even exist;
• The novel and unlawful use of a “hazard index” (for PFHxS, HFPO-DA, PFNA, and PFBS), never before used in the SDWA’s 50-year history;
• Failure to consider reasonable alternatives or respond meaningfully to public comments that undercut its judgment; and
• Significant procedural deficiencies in regulating the hazard index substances like collapsing two distinct rulemaking steps into a single step and forgoing Science Advisory Board review along the way.
For these reasons, we asked the D.C. Circuit to vacate the rule.
On February 7, 2025, with the NAM and other petitioners' consent, the court entered an order to hold the case in abeyance for 60 days, giving the new EPA Administrator Lee Zeldin the opportunity to review the rule. After a long extension of this abeyance period, the Trump EPA took action on the rule. On September 11, 2025, it filed a motion to vacate the limits on four of the six PFAS—PFNA, PFHxS, HFPO-DA, and PFBS. In its motion, the EPA conceded that these limitations were established through a flawed rulemaking process.
On September 26, the NAM filed its response to the EPA's motion for partial vacatur, echoing and expanding upon the EPA’s arguments. Our brief delves into the substantive flaws that doom the standards for PFNA, PFHxS, HFPO-DA, and PFBS. We explain that the standards are supported by inaccurate and under representative data about nationwide levels of PFAS in drinking water, and that they target mixtures of multiple chemicals when the SDWA only permits the EPA to regulate individual substances. Our fellow petitioners also supported the EPA’s vacatur of these limits in their responsive briefs.
In their opposition to EPA’s motion for partial vacatur, the intervenor ENGOs defend the process the EPA used to establish these regulations and request that the D.C. Circuit decide the validity of the limits based on the merits, not on the EPA’s unwillingness to defend them. They further propose that the EPA’s changed position risks harm to public health and request an additional opportunity to brief the court of these alleged risks.