U.S. EPA Sets Tap Water Limit of 4 ppt for PFOA and PFOS, First Legal Drinking Water Standard for PFAS

The U.S. Environmental Protection Agency (EPA) finalized its first legally enforceable drinking water standard (National Primary Drinking Water Regulation) for per- and polyfluoroalkyl substances (PFAS). Because the carbon-fluorine bond is extremely stable, PFAS do not break down easily in the environment or the human body, which is why they are called 'forever chemicals,' and they have been used in coated cookware, waterproof materials, firefighting foam and more.

The final rule sets the maximum contaminant level (MCL) for PFOA and PFOS at 4.0 ppt (4 parts per trillion) each, with a health goal (MCLG) of zero. PFHxS, PFNA and HFPO-DA (known as GenX) are each set at 10 ppt. For mixtures of PFAS, the rule introduces for the first time in drinking water regulation a hazard index approach, in which the concentrations of four substances, including PFBS, are each divided by their health-based concentration and added together, so that the sum must not exceed 1. Water utilities must monitor regularly and install treatment systems if the annual average exceeds the standard.

The Limit Is a Management Goal, Not a Danger Line

The 4.0 ppt for PFOA and PFOS is a value matched to the level that can be reliably quantified with current analytical methods, given that the health goal is zero. It does not mean that drinking water above this level immediately causes disease; it should be read as a management goal for keeping long-term exposure as low as possible. EPA has since said it will keep the PFOA and PFOS standards but extend the compliance deadline and reconsider the standards for the other substances, so the final scope of the regulation could change.