Particle exposure and inhaled dose while commuting in Lisbon.

While commuting, individuals are exposed to high concentrations of urban air pollutants that can lead to adverse health effects. This study aims to assess commuters' exposure to particulate matter (PM) when travelling by car, bicycle, metro and bus in Lisbon. Mass concentrations of PM2.5 and PM10 were higher in the metro. On the other hand, the highest BC and PN0.01-1 average concentrations were found in car and bus mode, respectively. In cars, the outdoor concentrations and the type of ventilation appeared to affect the indoor concentrations. In fact, the use of ventilation led to a decrease of PM2.5 and PM10 concentrations and to an increase of BC concentrations. The highest inhaled doses were mostly observed in bicycle journeys, due to the longest travel periods combined with enhanced physical activity and, consequently, highest inhalation rates.