United States Environmental Protection Agency's Perfluorooctanoic Acid, Perfluorooctane Sulfonic Acid, and Related Per- and Polyfluoroalkyl Substances 2024 Drinking Water Maximum Contaminant Level: Part 1 - Analysis of Public Comments.

In March 2023, the EPA proposed a 4.0 ppt maximum contaminant level (MCL) for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) (each) and a hazard index approach for four other PFAS. The EPA sought public feedback on the proposed MCL in early 2023 and received 1626 comment submissions the PFAS docket website (Docket ID: EPA-HQ-OW-2022-0114). Final MCLs were promulgated on April 10, 2024. Our analysis of the PFAS docket identified 128 comments that had a reasonable degree of scientific merit, with 57 comments endorsing the regulations and 71 questioning the MCLs public health utility. Critics noted the lack of evidence for adverse health effects at low PFAS exposures, the rule's significant impact on the economy, and the EPA's selection of published papers which the Agency chose to support their views. Many well-substantiated comments highlighted that few, if any, adverse health effects were reported at doses as much as 100-1000 times above those associated with the proposed drinking water guidelines. We found that the comments which discussed the evidence linking PFAS exposures below 200 ppt in drinking water to adverse health effects were equivocal. Most of the well-documented science based comments indicated that the data did not justify setting a 4.0 ppt MCL. It was noted that the EPA MCL was quite different from drinking water standards in other countries (up to 8-140 fold lower). During the review, it became apparent that a 4.0 ppt MCL may have little effect on PFAS blood concentrations in most Americans since drinking water accounts for less than 20% of their total PFAS intake. Additionally, a significant portion of the American population consumes minimal amounts of tap water. Commenters noted that the financial burden for treatment and cleanup was much higher than what was reported in the justification for the final MCL which was submitted to the Office of Management and Budget (OMB) and eventually promulgated. It is possible that EPA underestimated the financial impact on the nation by up to 100 to 200-fold. Our analysis indicates that many, if not most, of the scientifically rigorous comments on the EPA's proposed MCL were not acknowledged or considered by the Agency. We conclude the article by offering sixteen recommendations for the EPA to consider if Congress or the courts choose to reopen the evaluation of these MCLs. These included convening an international expert panel, reevaluating the appropriateness of the LNT model for PFAS, ensuring adequate time for study quality assessment and cost-benefit analysis, considering an approach to implementing a series of MCLs, critically reevaluating scientific studies, adhering to EPA risk assessment guidelines, addressing SDWA compliance concerns, revisiting the Hazard Index approach, and ensuring thorough and transparent review of public comments.