Estimated Influent PFAS Loads to Wastewater Treatment Plants and Ambient Concentrations in Downstream Waterbodies: Case Study in Southern and Central California

Per- and polyfluoroalkyl substances (PFAS) have received increased scrutiny from environmental and public health protection agencies, with focus placed on phased-out “legacy” PFAS such as perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). However, recent studies highlight the need to also evaluate the risks of replacement and breakdown products such as perfluorobutanesulfonic acid (PFBS) and hexafluoropropylene oxide dimer acid (HFPO-DA). Thus, the objective was to evaluate the ecological risks of legacy and newer PFAS, using monitoring and predictive models. Here, PFBS, PFOA, PFOS, and other PFAS were detected in samples collected downstream from 16 Southern and Central California wastewater treatment plants (WWTPs). PFBS, PFOA, and PFOS were sometimes detected at concentrations above experimentally determined lowest observed effect concentrations. Additionally, ChemFate, a fate and transport model, was used to estimate daily loads to the upstream WWTPs. Population size and urban land use were the best predictors of PFAS loads to WWTPs. The sum of influent loads of selected PFAS was estimated to be 61,000 ± 40,000 kg/year for California. Additionally, the sum of PFAS totaled annually in evaluated regions correlated well with the overall pollution burden. Here, the practicality of using predictive models in conjunction with field sampling to predict PFAS inputs and their ecological risks to the environment was demonstrated.