Assessment of human exposure to particle-associated organic pollutants in home environments of Lisbon, Portugal.

Indoor environments pose significant health implications due to the presence of pollutants, particularly fine particles (PM2.5), which are associated with adverse respiratory and cardiovascular outcomes. This study quantified particle-borne legacy and emerging organic pollutants in PM2.5 collected from 29 homes in Lisbon, Portugal, including polychlorinated biphenyls (PCBs), the insecticide dichlorodiphenyltrichloroethane (DDT) and its degradation products, the flame retardants polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDD) and organophosphate esters (OPEs), as well as per- and polyfluoroalkyl substances (PFAS). Mean PM2.5 concentrations were 15.4 μg/m3 indoors and 14.4 μg/m3 outdoors, with tobacco smoking leading to a marked increase in indoor levels. Concentrations of all target compounds were consistently higher indoors than outdoors, with OPEs dominating the chemical profile (43.0 ng/m3 indoors versus 5.9 ng/m3 outdoors). Although banned decades ago, legacy contaminants such as PCBs and DDT were still present in indoor particles, at concentrations exceeding those measured outdoors. Estimated daily intakes indicated higher exposures for infants than for children and adults, but all values remained below the available reference doses. These findings provide the first systematic characterization of PM2.5-bound organic pollutants in Portuguese homes and demonstrate that indoor particulate matter can act as a significant exposure pathway to multiple toxic chemicals, even when PM2.5 mass concentrations are comparable to those observed outdoors.