Per- and polyfluoroalkyl substances (PFAS) in Portuguese primary schools: Occurrence in air and implications for children's inhalation exposure.
BACKGROUND Per- and polyfluoroalkyl substances (PFAS) are persistent environmental pollutants increasingly detected in indoor environments, yet information on PFAS in school settings remains scarce. OBJECTIVE We characterized PFAS levels in primary school indoor air and estimated inhalation exposure among children and school staff. METHODS We collected 36 indoor and 8 outdoor air samples from 8 primary schools in Porto (the second-largest city in Portugal) and analyzed them for 64 PFAS, including perfluoroalkyl acids (PFAAs) and PFAA precursors. RESULTS PFAA precursors predominated over terminal PFAAs, accounting for 66.5% and 64.6% of total PFAS in indoor and outdoor air, respectively. Among PFAAs, perfluoroalkyl carboxylic acids (PFCAs) were the dominant class in both indoor and outdoor air (median: 3822.3 and 495.1 pg/m3, respectively), whereas polyfluoroalkyl phosphate esters (PAPs; median: 2811.6 and 732.0 pg/m3) and fluorotelomer alcohols (FTOHs; median: 1436.6 and 313.5 pg/m3) were the predominant PFAA precursors. Trifluoroacetic acid (TFA), perfluorooctane sulfonate (PFOS), nonafluoro-3,6-dioxaheptanoic acid (NFDHA), di-sulfonamido polyfluoroalkyl phosphate (diSAmPAP), and 8:2 fluorotelomer alcohol (8:2 FTOH) were the major individual PFAS detected indoors. All PFAS classes showed indoor enrichment relative to outdoor air. Children had higher body-weight-normalized inhalation exposure than adults. Under the low-exposure scenario, FTOHs contributed most to total EDI, whereas PFCAs predominated under the high-exposure scenario. CONCLUSION Primary schools constitute important indoor microenvironments for PFAS exposure. Although PFAA precursors predominated in indoor air, PFAAs accounted for the largest share of estimated inhalation exposure under the high-exposure scenario, highlighting the importance of considering both PFAA precursors and PFAS in comprehensive exposure assessments.