EPA finalizes first drinking water standard for PFAS

On April 10, 2024, the U.S. Environmental Protection Agency (EPA) finalized a National Primary Drinking Water Regulation (NPDWR) establishing legally enforceable Maximum Contaminant Levels (MCLs) for six PFAS in drinking water.  EPA established individual MCLs for PFOA, PFOS, PFHxS, PFNA, and HFPO-DA (i.e., GenX), and a Hazard Index MCL for PFAS mixtures containing at least two or more of PFHxS, PFNA, PFBS, and HFPO-DA.

  • For PFOA and PFOS, the individual MCL is 4.0 parts per trillion (ppt).
  • For PFHxS, PFNA, and HFPO-DA, the individual MCL is 10 ppt.
  • For mixtures containing two or more of PFHxS, PFNA, PFBS, and HFPO-DA, the Hazard Index MCL is 1 (unitless)

Under the final rule, regulated public water systems have three years to complete the initial PFAS monitoring of their system.  Based on the system size and source water, the initial monitoring requires sampling for the regulated PFAS on a semi-annually or quarterly basis during a 12-month period.  Beginning in 2027, regulated systems will be required to begin quarterly compliance monitoring at all entry points.  Once compliance monitoring begins, public water systems will be required to report detections of the regulated PFAS in their Consumer Confidence Report (CCR).

The PFAS MCLs become enforceable in 2029, giving public drinking water systems currently in violation of the MCLs five years to plan, fund and implement solutions to comply with the MCLs before the deadline.  EPA estimates the costs for public water systems to implement this regulation will be significant and has announced that $1 billion in funding from the Bipartisan Infrastructure Law will be available to support state and territories in implementing PFAS testing and treatment.  A more comprehensive overview of the regulation and its implications can be found on EPA’s website.

Although the rule is directed toward public water systems, the national primary drinking water standards are utilized widely in groundwater investigations and cleanups.  Despite the fact that the PFAS MCLs will not become enforceable for public water systems until 2029, you can expect that other regulatory programs will quickly adopt them as the default groundwater standards.

A more comprehensive overview of the regulation and its implications can be found on EPA’s website.