May 15, 2025
In a May 14 news release, the U.S. Environmental Protection Agency (EPA or Agency) announced that it plans to make changes to the drinking water regulations finalized under the Biden Administration to address per- and polyfluoroalkyl substance (PFAS). While presented as the agency keeping drinking water standards for two of the regulated PFAS, the agency is actually announcing its intention to roll back requirements established in the existing Safe Drinking Water Act (SDWA) regulations.
In April 2024, the Biden EPA finalized regulations (National Primary Drinking Water Regulations, or NPDWRs) requiring sampling, monitoring, and reporting and setting legally enforceable drinking water limits (Maximum Contaminant Levels, or MCLs) for six PFAS compounds as follows:
| Compound | Final MCL |
| Perfluorooctanoic acid (PFOA) | 4.0 parts per trillion (ppt) (also expressed as ng/L) |
| Perfluorooctane sulfonic acid (PFOS) | 4.0 ppt |
| Perfluorohexanesulfonic acid (PFHxS) | 10 ppt |
| Perfluorononanoic acid (PFNA) | 10 ppt |
| Hexafluoropropylene oxide dimer acid (HFPO-DA; commonly known as GenX Chemicals) | 10 ppt |
| Mixtures containing two or more of PFHxS, PFNA, HFPO-DA, and perfluorobutanesulfonic acid (PFBS) | 1 (unitless) Hazard Index |
In this year’s May 14 news release, the Trump EPA stated that it plans to maintain the 4 ppt MCL for PFOA and PFOS, including defending those standards in the ongoing litigation American Water Works Association, et al. v. EPA.
The EPA did announce, however, that it plans to propose a rule this fall (to be finalized in spring 2026) to extend the compliance deadline for water systems to meet the PFOA and PFOS MCLs from the current 2029 deadline to 2031. The Agency also said it will establish a federal exemption framework and initiate outreach to water systems through a new PFAS OUTreach Initiative (PFAS OUT). According to the Agency, these measures are intended to address the most significant compliance challenges EPA has heard from public water systems, members of Congress, and other stakeholders.
Unlike its plans to maintain PFOA and PFOS drinking water standards, EPA announced that it intends to rescind and reconsider the regulatory determinations for PFHxS, PFNA, HFPO-DA and the Hazard Index for mixtures of these three PFAS and PFBS.
EPA’s plans for amending the PFAS NPDWRs are subject to two vulnerabilities arising from SDWA’s statutory language.
First, the Agency’s plan to extend the MCL compliance deadline for PFOA and PFOS from 2029 to 2031 goes beyond the statute’s five year maximum compliance date (SDWA § 1412(b)(10), 42 U.S.C. § 300g-1(b)(10)). Section 1412(b)(10) mandates that the effective date of a NPDWR be set for three years (or earlier) from the rule’s promulgation date, except that the EPA Administrator “may allow up to 2 additional years to comply . . . if the Administrator . . . determines that additional time is necessary for capital improvements.”
EPA already applied the flexibility permitted by this two year extension in setting the MCL compliance date for April 2029. In fact, in a November 7, 2024 memorandum discussing state primacy requirements for the PFAS regulation, EPA stated, “SDWA section 1412(b)(10) does not provide the authority for EPA or a primacy agency to grant an additional two-year extension to comply with the NPDWR’s MCL(s).”
Second, the SDWA contains what is commonly referred to as an “anti-backsliding” provision that requires any revisions that EPA makes to NPDWRs to “maintain, or provide for greater, protection of the health of persons.” (SDWA § 1412(b)(9), 42 U.S.C. § 300g-1(b)(9)). The Agency will have a difficult task in justifying why the rescission of the drinking water standards for PFHxS, PFNA, HFPO-DA, and PFBS would not violate this provision of the statute, which has yet to be litigated.
To effectuate its plan to revise the PFAS NPDWRs, EPA will need to identify SDWA provisions to support its authority to amend the existing regulations as proposed, especially to overcome the apparent limitations discussed above. While EPA’s announcement and stated intentions are significant developments in the regulation of PFAS in drinking water, whether or not the Agency will succeed in its planned efforts remains to be seen.