PFOS dominates PFAS composition in ambient fine particulate matter (PM_2.5) collected across North Carolina nearly 20 years after the end of its US production

Contamination of drinking water by per- and polyfluoroalkyl substances (PFASs) emitted from manufacturing plants, fire-fighting foams, and urban waste streams has received considerable attention due to concerns over toxicity and environmental persistence; however, PFASs in ambient air remain poorly understood, especially in the United States (US). We measured PFAS concentrations in ambient fine particulate matter (PM2.5) at 5 locations across North Carolina over a 1 year period in 2019. Thirty-four PFASs, including perfluoroalkyl carboxylic, perfluoroalkane sulfonic, perfluoroalkyl ether carboxylic and sulfonic acids were analyzed by UHPLC/ESI-MS/MS. Quarterly averaged concentrations ranged from <0.004-14.1 pg m(-3). Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) ranged from <0.18 to 14.1 pg m(-3), comparable to previous PM2.5 measurements from Canada and Europe (<0.02-3.5 pg m(-3)). Concentrations above 1 pg m(-3) were observed in July-September at Charlotte (14.1 pg m(-3), PFOA), Wilmington (4.75 pg m(-3), PFOS), and Research Triangle Park (1.37 pg m(-3), PFOS). Notably, PM2.5 has a short atmospheric lifetime (<2 weeks), and thus, the presence of PFOS in these samples raises questions about their sources, since PFOS production was phased out in the US similar to 20 years ago. This is the first US study to provide insights into ambient PFAS concentrations in PM2.5.