In yet another damning indiction of air pollution in Delhi, a study has found that a student who travels from IIT Delhi till India Gate and back in various modes of transport, during rush hour, is exposed to 130-250 micrograms per cubic metre (µg/m3) of Particulate Matter (PM) 2.5 every month, according to a study conducted by IIT Delhi with other collaborators.
This exposure is much higher than the average of 150 µg/m3 of PM 2.5 levels seen in Delhi from 2012-2014, which is 15 times higher than the World Health Organisation’s recommended annual average.
According to the study, published in the international journal Atmospheric Environment, if the student was riding a cycle, the PM 2.5 exposure per kilometre was nine times higher, when compared to the exposure of someone travelling in an air-conditioned car. “At current level of concentrations, an hour of cycling in Delhi during the morning rush-hour period results in a PM 2.5 dose which is 40 per cent higher than what commuters are exposed to, in an entire day, in cities like Tokyo, London, and New York,” stated the study.
The particulate matter concentrations were measured along the same 8.3-km route in south and central Delhi. PM 2.5 levels were studied between January and May last year, to take into account the seasonal variations in pollutant levels. The researchers compared PM 2.5 concentrations in 11 differently modes of transport including public buses, air conditioned buses, autorickshaws, cycles, two-wheelers, air-conditioned cars and the Metro, among others. They also mapped exposure to PM 2.5 concentrations when the student was travelling on foot.
“For every mode of transport, we accounted for the exposure to access the route. For a bus ride, we also measured exposures while walking to the bus stop and waiting there. While measuring the exposure on a cycle, we took a route that routine cycle users take from IIT Delhi via Aurobindo Marg till the UPSC office,” said Rahul Goel, a PhD scholar from IIT Delhi’s Transport Research and Injury Prevention Programme who is the corresponding author of the study. The study was jointly authored by investigators from the University of Texas, IIT Mumbai, Desert Research Institute and University of California, along with IIT Delhi.
The study found that the on-road concentrations of PM 2.5 were between 10 to 40 per cent higher for different modes of transport, in comparison to the ambient air quality levels. According to the findings, the on-road PM 2.5 concentrations exceeded the ambient measures by an average of 40 per cent while walking, 10 per cent when the subject was cycling, 30 per cent for motorised two wheelers-like bikes and scooters, 30 per cent for open-windowed cars, 30 per cent for auto rickshaws, 20 per cent for air-conditioned as well as open-window buses and 30 per cent for underground metro stations.
Interestingly, the on-road concentration of PM 2.5 was lower than the ambient air quality levels by a staggering 50 per cent inside air-conditioned cars and 20 per cent inside a Metro compartment.
“It is almost as if our transport system is encouraging people to take air-conditioned vehicles, instead of making cycling or walking safer. But we have established that distance from traffic has a huge bearing on exposure, so building dedicated cycle lanes away from traffic can be a major way to control this,” said Professor Geetam Tiwari from IIT Delhi. According to the authors, this also explains why cyclists who take bylanes, away from the traffic, had a much lower exposure to particulates than other two-wheeler riders.
“Both modes are virtually the same, neither have the protection of a closed vehicle. Yet bike riders have a much higher exposure than those on cycles,” Dr Tiwari explained. In cleaner cities like London and Tokyo, where vehicles are a bigger source of pollution according to the authors, the difference between ambient and on-road air pollution levels are higher.