Pittsburgh, PA
Environmental Alert
(by Jean Mosites and Mackenzie Moyer)
On April 10, 2024, the U.S. Environmental Protection Agency (EPA) finalized the National Primary Drinking Water Regulation (NPDWR) Rule regulating six per- and polyfluoroalkyl substances (PFAS) under the Safe Drinking Water Act, 42 U.S.C. §§ 300f et seq. This final rule establishes the first-ever nationally enforceable drinking water standards for PFAS. The final rule establishes Maximum Contaminant Level Goals (MCLGs) and Maximum Contaminant Levels (MCLs) for perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorononanoic acid (PFNA), hexafluoropropylene oxide dimer acid and its ammonium salt (HFPO-DA, commonly known as GenX chemicals), and perfluorohexane sulfonic acid (PFHxS). The final rule also establishes a Hazard Index MCLG and MCL for mixtures containing two or more of PFNA, HFPO-DA, PFHxS, and perfluorobutane sulfonic acid (PFBS).
For PFOA and PFOS, the final rule sets MCLGs – non-enforceable health-based goals that represent the maximum concentration of a contaminant in drinking water at which there is no known or anticipated negative effect on a person’s health – at 0 parts per trillion (ppt). The MCLs, which are legally enforceable, are set at 4.0 ppt for PFOA and PFOS. The MCLs represent the maximum concentrations allowed in drinking water that can be delivered to users of a public water system and are informed by factors such as available treatment technologies and cost. As a change from the proposed rule, the final rule sets MCLGs and MCLs for PFNA, PFHxS, and HFPO-DA at 10 ppt.
For mixtures of two or more of PFNA, PFHxS, HFPO-DA, and PFBS, the final rule establishes a Hazard Index due to the chemicals’ likely co-occurrence. The Hazard Index is calculated by dividing the concentration of each of the four PFAS compounds by its Health-Based Water Concentration (HBWC; …