HUMAN HEALTH RISK ASSESSMENT OF PER- AND POLYFLUOROALKYL SUBSTANCES-CONTAMINATED DRINKING WATER SYSTEMS IN CALIFORNIA

Per- and polyfluoroalkyl substances (PFAS) are fully or partially fluorinated chemicals used in industrial and consumer products, resistant to biotic and abiotic degradation. PFAS are frequently detected in various environmental matrices, and their bioaccumulative potential adversely affects human health. While prior studies have extensively documented the occurrence of PFAS in environmental media, few have focused on exposure to PFAS and the associated human health risks. This research comprehensively documented the statewide occurrence of PFAS in public water systems (PWS) for the first time. In this study, we calculated the Hazard Indices (HI) for four commonly detected PFAS: perfluorohexane-sulfonic acid (PFHxS), perfluorononanoic acid (PFNA), perfluorobutane sulfonic acid (PFBS), and Hexafluoropropylene Oxide (HFPO-DA). Additionally, we calculated the Incremental Lifetime Cancer Risk (ILCR) for perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). Findings suggest many well sites (geolocations) in California exceeded the regulatory thresholds (HI<1 and ILCR < 1x10-6), suggesting potentially elevated health risks for residents in Los Angeles and Orange Counties. Approximately 4% of examined geolocations exceeded the ILCR threshold, while 20% of the locations exceeded the HI threshold. Geolocations containing carcinogenic and non-carcinogenic health risks were primarily located in economically disadvantaged communities. Specifically, residents of the Orange Coastal Plain and Los Angeles, who rely on groundwater from sub-basins with extensive PFAS contamination, are at higher risk. These findings underscore the need for targeted initiatives to remove PFAS from drinking water systems and protect public health.