Commuter exposure to particle-bound polycyclic aromatic hydrocarbons in Thessaloniki, Greece

Commuters are exposed to high air pollution levels daily, especially in areas with dense traffic. This study examines the commuter's exposure to polycyclic aromatic hydrocarbons (PAHs) in the city of Thessaloniki, Greece, under three different commuting modes: biking, travelling by private car, and riding public transportation means (buses). The study was carried out from 2015 to 2018 including 43 volunteers (15 cyclists, 17 car drivers/passengers, and 11 bus passengers). The personal exposure concentrations to particles smaller than 4-μm aerodynamic diameter (PM₄), constituting the respirable fraction of total airborne particles, and the associated PAHs were assessed for each commuting mode during the cold and the warm period of the year. Whereas the exposure of bus and car passengers to in-cabin PM₄ were higher in the cold season, the exposure of cyclists exhibited the opposite seasonality. In all commuting modes, exposure to PAHs was higher in the cold season. In both seasons, exposure concentration followed the order: cyclists > bus passengers > car passengers. The carcinogenic and mutagenic potencies of the exposure PAH concentrations were calculated using Benzo[a]pyrene (BaP) carcinogenic and mutagenic equivalency factors. The inhalation cancer risk (ICR) associated to PAHs was further estimated and compared between the different commuting modes. Our data can provide relevant information for transport decision-making and increase environmental awareness for a more rational approach to urban travelling.