Comparison of Particulate Matter Inhalation for Users of Different Transport Modes in Lisbon

Daily commutes can contribute to high exposure to urban air pollutants, such as particulate matter (PM10 and PM2.5). Since individuals are inevitably exposed to PM concentrations, it is crucial to study which transport modes present highest health impacts on users in order to provide different and healthier options for daily commutes.For the purpose of estimating PM inhaled doses, this research relates pedestrians’ ventilation rate and ambient PM concentration. The methodology consists on collecting data regarding PM concentrations on a second-by-second basis, using a portable laboratory, which is comprised by a PM analyzer and a laptop. The ventilation rates were found in the literature and adapted according to the intensity of the physical effort during the measurements.PM10 and PM2.5 concentrations were measured and compared across different microenvironments, such as walking, train, bus, mini-bus, tram and subway modes during off-peak hours based on a pre-selected round trip route in Lisbon, Portugal. Air quality data was also collected close to a fixed air quality monitoring station which is part of the round trip route, in order to have a reference PM concentration. A comparison of the different microenvironments based on the values obtained close to the fixed air quality station was made for PM concentrations and PM inhalation (which combines PM concentration with the physical effort).For this case study, results showed that the tram had higher PM10 concentrations and inside the subway higher PM2.5 concentrations, whilst the train ride had the lowest for both parameters. When considering the inhalation, the results were similar. The tram microenvironment had the highest PM10 inhalation while inside the subway train presented the highest PM2.5 inhalation. Even though the pedestrian microenvironment is the one with the highest ventilation rate, its low PM concentration leads to a low inhalation value, which proves the importance of considering both concentrations and ventilation.