Effect of modes of transportation on commuters' exposure to fine particulate matter (PM2.5) and nitrogen dioxide (NO2) in Chennai, India

Daily commuting increases level of contaminants inhaled by urban community and it is influenced by mode and time of commuting. In this study, the commuters' exposure to ambient particulate matter (PM2.5) and nitrogen dioxide (NO2) was assessed during three modes of travel in six different road stretches of Chennai. The mean distance of road stretches was 25 km and the exposure to pollutants was assessed during peak hours and off-peak hours. The average travel duration was in the range of 39 to 91 min in motorbike, 83 to 140 min in car and 110 to 161 min in bus. Though there was variation on exposure to concentration in modes of transportation, the maximum exposure concentration of PM2.5 was observed as 709 mu g/m3 in bus and the minimum exposure concentration was 29 mu g/m(3) in closed car. Similarly, the maximum exposure concentration of NO2 was observed to be 312 mu g/m(3) in bus and the minimum exposure concentration was 21 mu g/m(3) in car. The concentration of elements in PM2.5 was in the order of Si > Na > Ca > Al >= K > S >= Cd, with Si and Cd concentration as 60% and < 1% of the PM2.5 concentration