On Wednesday, May 20, the U.S. Environmental Protection Agency (EPA) proposed two rules that will once again reshape the federal regulatory landscape surrounding per- and polyfluoroalkyl substances (“PFAS”), the “forever chemicals” that have been a subject of international regulation and litigation for roughly twenty years. If finalized, these two proposed rulemakings have the potential to fundamentally alter the 2024 drinking water regulations addressing PFAS.
Background
PFAS are a class of chemicals that have extremely strong carbon-fluorine bonds, making PFAS-containing products durable, waterproof, and/or fire-retardant. As a result, PFAS are a staple in manufacturing endless consumer products worldwide, like non-stick cookware, stain-proof carpet, fabric and upholstery treatments, camping gear, raincoats, athletic wear, and firefighting foam, to name some examples. These durable properties also make PFAS exceptionally biopersistent, meaning they don’t break down in our environment and can travel long distances through air and water, leading to widespread accumulation. This includes the buildup of PFAS contamination in our food chain and drinking water sources, and in human blood. It is estimated that 98% of Americans have PFAS in their blood, likely due in part to drinking water exposure. Based on data from the EPA’s Fifth Unregulated Containment Monitoring Rule (UCMR 5), a federal program that required roughly 10,000 public water systems to monitor for several compounds from 2023-2025, PFAS were detected in approximately one‑third of tested systems nationwide, with at least one compound found in over 3,500 systems serving over 150 million Americans.
Many studies suggest that several PFAS chemicals cause various health ailments, including kidney and testicular cancer, and reproductive issues, including infertility. A 2025 study found that PFAS in drinking water was associated with increased cancer incidence in the digestive, endocrine, oral cavity/pharynx, and respiratory systems. For this reason, many states, and the federal government, have taken actions to identify and reduce PFAS concentrations in drinking water sources.
The 2024 NPDWR
The National Primary Drinking Water Regulations (“NPDWR”) were finalized in April of 2024. Promulgated under the Safe Drinking Water Act (“ SDWA”), the NPDWR set maximum contaminant levels, or MCLs, that capped the concentration of certain types of PFAS in drinking water from Public Water Systems (“PWS”). The Rule established enforceable MCLs for five PFAS and regulated a total of six through an additional “hazard index” that addresses combinations of different PFAS compounds. PWS have until April 2027 to monitor concentrations of regulated PFAS in their systems and report exceedances to regulators and consumers. All PWS must be in compliance by April 2029, meaning the levels of the regulated PFAS in their water systems must be at or below the MCLs.
The 2024 Rule has met significant pushback from PFAS manufacturing industry actors and water provider associations. This is partly because the 2029 compliance deadline is a massive undertaking for some PWS, requiring major infrastructure changes and new staff, among other action items and associated costs.
Petitions challenging the NPDWR were filed by some of these groups in the D.C. Circuit Court of Appeals in June of 2024, consolidated as National Association of Manufacturers, et al. v. EPA, et al. (No. 24-1191). The EPA initially defended the final Rule, but following the change in Administration, requested a partial vacatur of portions of the Rule that it seeks to rescind. The Court denied this motion, and then denied the EPA’s motion to sever and hold portions of the Rule in abeyance. Final briefing in the case is complete, and parties await scheduling of an oral argument.
The Proposed Rules
In May of 2025, the EPA announced that it would be relaxing the NPDWR by extending the compliance deadline from 2029 to 2031, and rescinding certain provisions of the Rule, but maintaining the MCLs for PFOA and PFOS. The agency proposed two rulemakings on May 20, 2026, to these ends. The proposed rulemakings seek to:
- De-regulate four of the six initially regulated PFAS by rescinding MCLs for PFHxS, PFNA, and HFPO-DA, and eliminate the hazard index (RIN 2040-AG53), and
- Provide a process by which PWS may be granted an extension to meet the MCLs for PFOA and PFOS (RIN 2040-AG49).
The proposed rules are now subject to a public notice and comment period, which ends on July 20, 2026. A public hearing is scheduled for July 7.
The title of RIN 2040-AG53 is “Extending the Compliance Deadline for the PFOA and PFOS Maximum Contaminant Levels,” but it is critical to note that the proposed rule would not, as the title suggests, automatically delay the compliance deadline from 2029 to 2031 if finalized. Rather, regulated PWS would need to apply for an extension within 180 days of the rule’s finalization and provide additional information. The proposed rule additionally states that PWS with any PFOA or PFOS results equal to or exceeding 12 ppt seeking an extension will need to implement at least two listed “interim control measures.”
The proposed rule also clarifies limitations on the EPA’s power to carry out an extension, given power provided to states through primacy. The framework of the SDWA requires that it be carried out through a state-federal partnership wherein states obtain primacy to enforce the Act’s provisions. Nearly all states have primacy generally to enforce the SDWA. But the 2024 NPDWR requires a special application process for states to gain enforcement ability. In addition to adopting standards at least as stringent as the federal MCLs, states had to file an application for enforcement by April 27, 2026 (subject to extensions). Some states may have applied, but there is no public list of those states. Currently, no states have yet obtained primacy to enforce the 2024 MCLs, and there are no set dates wherein primacy will be individually granted. But, as the EPA specifically notes in its proposed rule, once states obtain primacy for the MCLs, the EPA no longer has authority to grant or deny exemption requests. State agencies that have primacy are free to maintain the original compliance date for PWS within their state and/or set up their own processes for accepting extension requests.
If finalized, these rules are likely to face significant challenges in the D.C. Circuit. RIN 2040-AG49, “Rescission of Regulatory Determinations and Removal of Related Provisions for Four PFAS Substances (PFHxS, PFNA, HFPO-DA (GenX), and the Mixture of These Three PFAS Plus PFBS),” may be considered especially vulnerable to vacatur following a challenge. Environmental groups and other likely petitioners will likely argue that this proposed rule violates the SDWA’s anti-backsliding provision, as Respondent-Intervenors argued in their opposition motion to the 2024 Rule’s vacatur in National Association of Manufacturers, et al. v. EPA. The SDWA’s anti-backsliding provision is a limit on rulemaking contained in the Act that prohibits the government from weakening safety standards to make them less protective once they’ve been finalized, subject to narrow exceptions. The EPA’s reasoning for revocation of portions of the NPDWR is that these portions were impacted by a procedurally faulty rulemaking process.
This proposed rule’s impact is also subject to state action, as states are still free to maintain, enact, and enforce their own MCLs on these other PFAS regardless of whether the federal MCLs are revoked. The SDWA requires only that state standards are no less stringent than federal standards, constituting a floor, rather than a ceiling, on state drinking water policy.
The EPA’s twin proposals mark a significant—and potentially contentious—inflection point in federal PFAS regulation. By coupling a conditional pathway for extending compliance deadlines with an effort to rescind regulatory limits on several PFAS, the agency is attempting to recalibrate both the pace and scope of the 2024 NPDWR. While regulated industries may find that the proposed rules may provide needed flexibility for PWS to feasibly comply, others will take the position that they seek to impermissibly backslide and delay already-slow progress to protect Americans from PFAS chemicals in drinking water. Regardless, the practical effect of these changes will depend heavily on state action, as states retain authority to adopt and enforce more stringent standards.
As the rulemaking process unfolds and judicial review looms, regulated entities, states, and stakeholders alike should prepare for continued uncertainty in an already complex and evolving PFAS regulatory landscape.
