Can four decades of experience with dioxins inform scientists and regulatory agencies about how to regulate PFAS chemicals?

Summary The regulatory histories of dioxins and per- and polyfluoroalkyl substances (PFAS) reveal notable parallels, both shaped by early toxicological concerns and advances in chemical detectability that preceded comprehensive epidemiological validation. This paper examines how initial risk assessments for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) relied heavily on high-dose animal studies and limited human data, leading to stringent regulations and significant remediation efforts that were later questioned by findings from long-term epidemiological studies. A similar course can be anticipated for PFAS, where regulatory actions such as the setting of extremely low safe drinking water standards have been established despite substantial scientific uncertainties about health effects at environmentally relevant exposure levels. By comparing toxicological mechanisms, dose–response relationships, and regulatory strategies, this analysis identifies important factors that put into question the reliance on precautionary principles without a full evaluation of the uncertainties surrounding each of the alleged adverse health effects. The experience with dioxin regulation provides a basis for recommending that PFAS regulatory bodies adopt a more adaptive strategy, one that emphasizes evolving scientific evidence, careful interpretation of low–dose responses, and greater reliance on relevant human epidemiological data rather than conservative extrapolations primarily from animal studies. This paper suggests that if the scientific and regulatory community reflects on the experience with dioxins, the United States and other nations can potentially save billions by not setting unnecessarily low PFAS regulatory standards while still achieving a theoretical reduction in the possible risks to public health.