Assessment of exposure to respirable particles (PM2.5) concentrations in public transportation

Background and High concentrations of respirable particles may cause high incidence of respiratory diseases and mortality. Epidemiological exposure assessment is based on fixed site measurements in ambient air. However, major studies reported good relationship between indoor fine particulate air concentrations and personal exposure. This study is focussed on personal exposure to PM2.5 in different transportation modes and factors that cause high indoor PM2.5 levels. In this study, a calibrated real time monitor (MicroDust Pro) was used to measure PM2.5 levels in 3 mode of transportation (bus, car and train) on the same route. Results were also compared with PM10 concentrations measured by fixed site monitors. A small Poly Urethane Foam (PFU) filter was designed for PM2.5 size fraction monitoring and a small personal sampling pump was used to provide a continuous airflow through the gravimetric adaptor and photo detector. The mean PM2.5 concentration measured in the train was lower than the mean fixed site PM10 concentration. However, the mean PM2.5 levels in car and bus were much higher than those mean PM10 concentrations measured by fixed site monitors. Boarding, picking up, dropping off, and movement of passengers inside the bus and train were significantly related to short-term increases in PM2.5 concentrations. However, stopping at the traffic light was the most important factor associated with peak PM2.5 concentrations inside the car. Penetration of particles that were created by road traffic and resuspension of fine particles in the vehicles were the most important factors that may increase respirable particles in transportation modes.