Unmasking per- and polyfluoroalkyl substances (PFAS) in facemasks: Occurrence and leaching implications

The extensive use and disposal of facemasks during the COVID-19 pandemic and its ongoing post-pandemic impacts have heightened potential risks of human exposure and environmental release of emerging contaminants, such as per- and polyfluoroalkyl substances (PFAS). This study quantifies 21 PFAS (∑₂₁PFAS), estimates unidentified PFAS precursors, and evaluates leaching under disposal-relevant conditions from prominent facemasks, extending previous research by addressing leaching behavior and expanding the dataset to Chinese-market products. We found relatively low ∑₂₁PFAS concentrations (0.68-5.3 ng/g) in facemasks, with 0.49-2.3 ng/g release to water. Notably, the tested reusable cloth facemask contained substantial amounts of unidentified precursors in both solids and leachates, as revealed by the total oxidizable precursor (TOP) assay. PFAS leaching was thermodynamically non-spontaneous, with leachability varying from 14.8 % to 84.7 %, depending on the chemical properties of PFAS. Furthermore, leachate conditions significantly impacted PFAS release, with a ∼14 % increase in leaching due to a 10℃ temperature rise and a 102-300 % increase due to the presence of dissolved organic matter. With an annual disposal of 250-480 billion facemasks, it is estimated that these facemasks release 0.72-1.4 kg of ∑₂₁PFAS and 0.50-0.98 kg of ∑₇PFCAs (seven commonly measured perfluoroalkyl carboxylic acids) into leachates, contributing only 0.1-0.2 % to the total PFAS load in leachates at disposal facilities.