EPA Finalizes National Primary Drinking Water Regulation for Six PFAS
On April 10, 2024, the U.S. Environmental Protection Agency (EPA) finalized a National Primary Drinking Water Regulation (NPDWR) for six PFAS:
- Perfluorooctanoic acid (PFOA)
- Perfluorooctane sulfonic acid (PFOS)
- Perfluorohexane sulfonic acid (PFHxS)
- Perfluorononanoic acid (PFNA)
- Hexafluoropropylene oxide dimer acid (HFPO-DA, commonly known as GenX chemicals)
- Perfluorobutane sulfonic acid (PFBS)
MCLs and Health-Based Water Concentrations
The NPDWR established Maximum Contaminant Levels (MCLs), which are enforceable drinking water standards that consider available treatment technologies and costs. Individual MCL values were finalized for five PFAS, and a Hazard Index MCL was finalized for four PFAS. Health-based water concentrations, which are used to calculate the Hazard Index, were also established for four PFAS. MCLs and health-based water concentrations are summarized in the table below.
Hazard Index MCL
The EPA's Hazard Index uses individual measurements of PFNA, PFHxS, PFBS, and HFPO-DA to evaluate their combined risk. Measurements of the four individual PFAS are divided by their respective health-based water concentrations, which are included in the table above. The four values are then summed to calculate the Hazard Index, which is compared to the Hazard Index MCL of 1. A Hazard Index greater than 1 would be considered an MCL exceedance. While the Hazard Index is a long-established approach EPA uses to evaluate the health risk of chemical mixtures, a Hazard Index MCL has not been previously established. The EPA developed a fact sheet detailing the process of calculating the Hazard Index.
Analytical Requirements
The EPA established practical quantitation levels (PQLs) for the regulated PFAS, which are the lowest levels that constituents can be reliable quantified within specified limits of precision and accuracy during routine laboratory operating conditions. The PQLs for PFOA and PFOS were set at 4 ppt, equivalent to their MCLs. PQLs were also set at 3 ppt for PFHxS, 4 ppt for PFNA, 5 ppt for HFPO-DA, and 3 ppt for PFBS. The regulated PFAS can analyzed by EPA Method 533 or Method 537.1 for NPDWR monitoring.
Implications for Drinking Water Utilities
Public water systems must complete initial monitoring by 2027 and then begin ongoing compliance monitoring thereafter. Beginning in 2027, public water systems must include PFAS monitoring data in Consumer Confidence Reports. Starting in 2029, if public water systems have PFAS concentrations that exceed the MCLs in drinking water, they must take action to reduce levels of these PFAS to below MCL values and notify their consumers.
Drinking water utilities may need to upgrade their treatment facilities with additional treatment steps to decrease PFAS concentrations below the MCLs. The EPA identified four Best Available Technologies to treat the regulated PFAS, including granular activated carbon, anion exchange, nanofiltration, and reverse osmosis. The EPA estimates the cost of PFAS monitoring and treatment for public water systems to be $1.5 billion per year.
The EPA published a fact sheet summarizing implementation of the NPDWR and its estimated economic impact.
Additional Information
If you have questions or would like to discuss how these regulations could impact your business, please reach out to one of Geosyntec’s nationally recognized PFAS subject matter experts. PFAS practitioner biographies can be found at https://www.geosyntec.com/pfas.
