Toxicity assessment of airborne ultrafine particles: Role of transport emissions.

Airborne quasi-ultrafine particle samples were collected from different outdoor sites in Barcelona (NE Spain, 35 samples) and the Valencia subway (about 400 km south of Barcelona, 3 samples). Locations and schedules were designed to cover cold and warm seasons and to represent the impact of different types of transport (cars, trains, ships, and planes). Extracts from PTFE filters (methanol:dichloromethane 1:2) were used to test toxic effects in human cell lines (Induction of reactive oxygen species, inflammatory response) and in zebrafish embryos (expression of xenobiotic response-related genes, cyp1a1, gsa1 and hao1). We observed distinct toxic effects related to different forms of oxidative stress and to inflammatory response, the two types of negative outcomes more closely related to the known epidemiological impacts of air pollution. The highest toxicity values were detected in sites receiving car and/or ship emissions, with maximums during the cold season. Chemical analysis followed by correlation and source apportionment analyses identified PAHs, combustion engines, and biomass burning emissions as the main drivers of the observed toxic effects. Therefore, traffic restrictions, car emission limits, and reduction of combustion processes are necessary to eliminate or at least to limit airborne toxicity in urban environments.