An introduction to the Alliance for Risk Assessment Beyond Science and Decisions XIV: PFAS Limits: How Did We Get So Far Apart?

Summary This paper presents a summary of presentations at the Alliance for Risk Assessment (ARA) Workshop XIV held on October 17–19th, 2023, in Washington, DC, focusing on the health risk-assessment and regulation of perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS), and other per- and polyfluoroalkyl substances (PFAS). The main topics were as follows: Toxicological understanding and safe dose: Workshop participants felt that efforts by different regulatory agencies to derive a safe dose for PFOA and other PFAS should be harmonized. Currently, the acceptable daily intakes estimated by various expert-groups differ by up to 1,000-fold. Over time, mechanistic insights in understanding PFAS toxicity may better inform estimates of safe doses. Regulatory concerns: The United States Environmental Protection Agency (EPA) finalized drinking water regulations for PFOA, PFOS, and four other PFAS. The Agency selected maximum contaminant levels (MCLs) as low as 4 parts per trillion (ppt). Many participants believed that EPA’s precipitous drop from the recommended health advisory limit (in 2016) for PFOA and PFOS in drinking water of 70 ppt, to a maximum contaminant level of 4 ppt, was unjustified. Legal aspects of regulatory decision making: Participants noted that the proposed PFAS MCLs, if challenged in court, were likely to be upheld due to judicial deference to EPA’s scientific and regulatory expertise. Overall, the meeting participants felt that diverse scientific perspectives should be better incorporated into US EPA’s assessments of risks to public health from PFOA, PFOS, and other PFAS.