What to Expect in Key EPA Cases on PFAS and Lead in Drinking Water

This case, filed by the water utility trade association the American Water Works Association, challenges the Biden administration EPA’s October 2024 Lead and Copper Rule Improvements, the famous rule that will require virtually all lead service lines to be removed within a 10-year period (American Water Works Association v. EPA, Case No. 24-1376).

NRDC and our allies have intervened in this case to defend the rule. The briefs on the legality of the rule have been filed by the EPA and all parties, including the industry challengers of the rule and NRDC and our partners (key briefs are available here). Several health organizations and other groups, among them the American Academy of Pediatrics and 17 state attorneys general, filed amicus briefs supporting the rule. The Trump administration has also filed a brief defending the rule. Oral arguments in the case are expected later in 2026, and a decision is likely 6 to 12 months after oral arguments.

This case was filed by the chemical industry that is polluting the nation’s drinking water with PFAS forever chemicals. It is joined by the trade associations American Water Works Association and Association of Metropolitan Water Agencies, which are representing the water utilities that are supposed to be protecting their customers’ health from these toxic chemicals in their tap water.

The suit challenges the Biden administration EPA’s April 2024 drinking water standards (“maximum contaminant levels,” or MCLs) for six PFAS (American Water Works Association et al. v. EPA, Case No. 24-1188). The EPA has estimated that this rule will protect up to 105 million Americans from drinking water that is contaminated with these forever chemicals at levels exceeding the agency’s new standards. NRDC and our allies are intervenors in this case and defending the rule. And along with industry groups, the Biden administration’s EPA, and several partners, NRDC has filed substantive briefs in the case.  

But now the Trump administration’s EPA reversed course and is no longer defending four of the six PFAS standards (for GenX, PFHxS, PFNA, and PFBS). Instead, it joined industry in asking the court to throw out those rules. The court refused requests from the EPA and the chemical and water industries to “vacate” the four standards that the agency has now announced it intends to repeal, instead waiting to evaluate all of the attacks on the 2024 rule together. The EPA is defending the other two standards (for PFOA and PFOS) but has said it wants to delay its enforcement by two years. Key briefs in the case, including amicus briefs supporting the rule by several leading PFAS scientists and by 19 state attorneys general are available here. Oral arguments in the case are expected later in 2026, and a decision is likely 6 to 12 months after oral arguments.  

On May 18, 2026, the EPA proposed to rescind the maximum contaminant levels (MCLs) for four PFAS (GenX, PFHxS, PFNA, and PFBS) and said it will delay by two years the compliance deadline for two of the PFAS MCLs (for PFOA and PFOS).  

This is another case in which the chemical industry, U.S. Chamber of Commerce, and other industry representatives are challenging the Biden administration EPA’s designation of two forever chemicals, PFOA and PFOS, as “hazardous substances” under the Superfund law. This designation will enhance the EPA’s ability to clean up sites contaminated with these toxic forever chemicals (Chamber of Commerce et al. v. EPA, Case No. 24-1193).

NRDC and our allies are intervenors defending the rule, represented by Earthjustice; the EPA is defending the rule. All briefs have been filed, and an oral argument was held on January 20, 2026. A decision generally would be expected about 6 to 12 months after the argument.

• While the Biden administration EPA already filed their briefs defending the PFAS MCLs and PFAS Superfund designations, it is possible that the Trump administration EPA might now ask the court for permission to reverse its position and no longer defend the rules, possibly even filing a brief saying the rule shouldn’t be upheld. Other parties could oppose such an EPA request, and the court would have to decide whether to allow the EPA to file a new brief.
• In theory, the Trump administration EPA could ask the court to “remand” any of these rules back to the agency for reconsideration. However, the courts don’t automatically grant such requests.
• It’s also possible that if the EPA initiates a new rulemaking process related to an existing rule, the court might keep the existing litigation in abeyance while the EPA goes through the new rulemaking process.
• In sum, if the Trump administration EPA were to ask the court to remand any of these rules, the court would then need to decide whether to: (a) approve the remand request; (b) leave the case in abeyance while the EPA conducts a new rulemaking; or (c) allow the case to proceed.  

• The SDWA includes a measure informally referred to as the “anti-backsliding” provision that prohibits the EPA from weakening any drinking water standard once it’s set. It says any revision of a drinking water standard “shall maintain, or provide for greater, protection of the health of persons” (SDWA §1412(b)(9)).
• If the rule is remanded back to the EPA, or if the agency initiates a new rulemaking process to change existing drinking water standards, the SDWA’s anti-backsliding provision would apply. 

• Rules that are in effect and have not been lawfully withdrawn cannot be invalidated without a court finding that they violate the law.
• If the EPA were to change its position and no longer defend a rule, the court would still have to decide whether the rule was lawful before striking it down. NRDC and our allies will be there to argue that the rule should not be struck down, even if the EPA changes positions. 

• In certain circumstances, the court may grant the EPA a remand without vacatur, in which case the rule remains in effect while the EPA reconsiders its provisions. The EPA could initiate a new rulemaking to revise the rule through the standard notice and comment process, with the important caveat that the SDWA includes the anti-backsliding provision that prohibits a drinking water standard from being weakened. If the agency initiates a new rulemaking process related to an existing rule, the court might keep the existing litigation in abeyance while the EPA goes through the new rulemaking process.
• If the court considers a substantive challenge to a rule in the litigation, it could uphold the rule or it could throw out some or all of the rule. If the EPA wants to issue a replacement rule, or the applicable statute requires the agency to issue a new rule, it would have to go through a new rulemaking process to adopt a new rule. The EPA might be required to start a new rulemaking process, but it would depend on exactly what the court decides and what the applicable statute requires.