On April 10, the US Environmental Protection Agency (EPA) announced its final PFAS drinking water rule, setting new drinking water standards for six per- and polyfluoroalkyl substances (PFAS).

Below, we outline the primary requirements of the new Rule.

The Rule concludes the rulemaking process that started in March of 2023 with EPA’s issuance of a proposed rule which posited new extremely stringent minimum contaminant levels (MCLs) and standards under the Safe Drinking Water Act for six PFAS: perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS), perfluorononanoic acid (PFNA), hexafluoropropylene oxide dimer acid (HFPO-DA, or GenX Chemicals), and perfluorobutane sulfonic acid (PFBS). Specifically, in part, the proposed rule presented (1) MCLs of four parts per trillion (ppt) for PFOA and PFOS, (2) a new heath index-based approach for standards for the four remaining PFAs compounds, and (3) a three-year period for public water systems to achieve compliance with the new standards. The proposed rule elicited an extraordinary volume of public comments — more than 120,000.

The Rule reflects many differences from the proposed rule, including (1) MCLs of 10 ppt for PFHxS, GenX, and PFNA (while keeping the four ppt MCLs for PFOA and PFOS), (2) use of the hazard index only for mixtures of PFHxS, PFNA, GenX, and PFBS, and (3) a five-year period to achieve compliance. EPA estimates that approximately 6-10% of the nation’s 66,000 public drinking water systems subject to the Rule may have to take action to meet the new standards. Some argue that estimate to be low. The preamble to the Rule lists non-mandatory technologies that public water systems can potentially use to comply with the MCLs, including granular activated carbon (GAC), anion exchange resins (AIX), and high-pressure membranes (nanofiltration (NF) and reverse osmosis (RO)).

In addition to the above-referenced drinking water standards, the Rule includes monitoring, public notification, and reporting requirements. Public water systems must conduct initial monitoring within three years of the rule being published in the federal register. After three years, water systems must start conducing regular compliance monitoring, including the results of the monitoring in Consumer Confidence Reports and notifying the public of monitoring and testing violations.

Concurrent with the Rule, EPA also announced $1 billion of funding under the Bipartisan Infrastructure Law to help states and territories implement PFAS testing and treatment at public water systems and to help owners of private wells address PFAS contamination.

The Rule is expected to be published in the Federal Register shortly.

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