Occurrence and fate of legacy and novel per- and polyfluoroalkyl substances (PFASs) in freshwater after an industrial fire of unknown chemical stockpiles.

An industrial warehouse illegally storing a large quantity of unknown chemical and industrial waste ignited in an urban area in Melbourne, Australia. The multiday fire required firefighters to use large amounts of fluorine-free foam that carried contaminated firewater runoff into an adjacent freshwater creek. In this study, the occurrence and fate of 42 per- and polyfluoroalkyl substances (PFASs) was determined from triplicate surface water samples (n = 45) from five locations (upstream, point-source, downstream; 8 km) over three sampling campaigns from 2018 to 2020. Out of the 42 target PFASs, perfluorocarboxylates (PFCAs: C4-C14), perfluoroalkane sulfonates (PFSAs: C4-C10), and perfluoroalkyl acid precursors (e.g. 6:2 fluorotelomer sulfonate (6:2 FTSA)) were ubiquitously detected in surface waters (concentration ranges: <0.7-3000 ng/L). A significant difference in ΣPFAS concentration was observed at the point-source (mean 5500 ng/L; 95% CI: 4800, 6300) relative to upstream sites (mean 100 ng/L; 95% CI: 90, 110; p ≤ 0.001). The point-source ΣPFAS concentration decreased from 5500 ± 1200 ng/L to 960 ± 42 ng/L (-83%) after two months and to 430 ± 15 ng/L (-98%) two years later. 6:2 FTSA and perfluorooctanesulfonate (PFOS) dominated in surface water, representing on average 31% and 20% of the ΣPFAS, respectively. Emerging PFASs including a cyclic perfluoroalkanesulfonate (PFECHS) and a C4 perfluoroalkane sulfonamide (FBSA) were repeatedly present in surface water (concentration ranges <0.3-77 ng/L). According to the updated Australian PFAS guidelines for ecological conservation, the water samples collected at the time of monitoring may have posed a short-term risk to aquatic organisms in regard to PFOS levels. These results illustrate that acute high dose exposure to PFASs can result from industrial fires at sites storing or stockpiling PFAS-based waste products. Continued monitoring will be crucial to evaluate potential long-term risk to wildlife in the region.