Per- and Polyfluoroalkyl Substances (PFAS): History, Current Concerns, and Future Outlook

Per- and polyfluoroalkyl substances (PFAS) involve multiple per- and polyfluorinated compounds that are widely used globally. Legacy PFAS, including PFOA, PFOS, and PFHxS, were manufactured before 2000 in various industrialized nations, then gradually phased out in accordance with the Stockholm Convention. Due to the substantial accumulation of these legacy PFAS compounds, their concentrations in drinking water are regulated in some countries. This review first summarizes the historical background of PFAS, followed by a description of their chemical properties. The clinical manifestations of legacy PFAS in humans, such as dyslipidemia, attenuated immune function, and chronic kidney disorders, are also summarized. Emerging PFAS involve Gen-X and F-53B as well as numerous newly developed chemicals with their associated precursors/metabolites, including volatile PFAS. Research on these emerging PFAS compounds in the environment continues to grow, building a substantial body of evidence about their effects. The chemical structure of emerging PFAS shows a wide variety: they could contain ether, ester, sulfoneamide, and other halogen atoms rather than fluorine. Volatile PFAS involve the fluorotelomer 6:2 FTOH and other short-chain PFAS compounds, which are best measured by GC-MS. This review also briefly summarizes the assay for total oxidizable precursors of PFAS, an LC-MS-based assay for an emerging assay that will be used for a quantitative estimation of total PFAS, including emerging PFAS.