After several years of per- and polyfluoroalkyl substances (PFAS) making news headlines, the United States Environmental Protection Agency (EPA) announced on April 10, 2024, its highly anticipated final National Primary Drinking Water Regulation (NPDWR) for PFAS. This final rule establishes Maximum Contaminant Levels (MCLs) for five compounds in drinking water (PFOA, PFOS, PFHxS, PFNA, and HFPO-DA) individually and uses a Hazard Index for PFAS mixtures containing at least two or more of PFHxS, PFNA, HFPO-DA, and PFBS to account for the combined (or additive) potential for toxic effects. Tuesday’s announcement comes more than a year after the proposed rule was announced on March 14, 2023.
The Federal Maximum Contaminant Levels
The final rule establishes Maximum Contaminant Levels (MCLs) for six PFAS in drinking water and a Hazard Index MCL, determined by dividing the concentration of each of the four analytes (PFHxS, PFNA, HFPO-DA, and PFBS) by the calculated health-based water concentrations for each compound individually. The summed value of the quotients is the hazard index. The following table summarizes the final MCLs.
