Wastewater pre-treatment processes as a potential source of atmospheric per- and polyfluoroalkyl substances (PFAS)...

Per- and polyfluoroalkyl substances (PFAS) or "forever chemicals" have been increasingly detected in the atmosphere across urban, rural, and remote areas, raising the possibility of atmospheric exposure to humans. However, their exact emission sources to the atmosphere are poorly understood. Here, we investigated the atmospheric particulate matter (PM) associated emissions of restricted and new generation PFAS from the pre-treatment (grit chamber) and secondary settling steps of a wastewater treatment plant (WWTP). 12 PFAS including restricted perfluorooctanoic acid (PFOA) and perfluoroocatnesulfonic acid (PFOS), were detected in the PM samples. PFOS was the most abundant PFAS detected at all sampling points, with mean concentrations of 5.7 ± 1.7 pg/m³, 0.42 ± 0.42 pg/m³, and 0.60 ± 0.25 pg/m³, in the grit-chamber, secondary settler, and staff building samples, respectively. The presence of PM bound PFOS and PFOA, which have been restricted for several years, raises concerns about their possible continued use and input into sewage systems. The complementary non-targeted analysis (NTA) of the grit-chamber samples and suspect screening of secondary settler and staff building samples revealed 14 additional tentatively identified organic compounds, including insecticides, metabolites, and industrial chemicals. Among these, 4-nitrophenol (confirmed with the authentic standard), a key brown carbon component linked to adverse health effects and cloud condensation activity, was detected in PM for the first time in both pre-treatment and secondary settling steps. These findings reveal a previously unrecognised source of atmospheric PFAS and 4-nitrophenol, with important implications for exposure and risk assessment.