NEW DELHI: If you wish to reduce your exposure to polluted air, travelling by the Delhi Metro or an air-conditioned car may be your safest bet, a study analysing the inhalation and exposure of PM 2.5 in various modes of travel across the city has found. Exposure to PM 2.5 was highest in an autorickshaw.
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The study, carried out by researchers from Northumbria University (Newcastle), IIT Madras, CSIR-NEERI and Central Road Research Institute (CRRI) among others, recorded real-time data monitored through an 11-km long stretch from IIT Delhi to Connaught Place. It used a portable TSI SidePak Aerosol Monitor AM520 and collected the ambient air quality readings of the area as well as the possible exposure inside the vehicle. It found walking to be the most dangerous, with the highest respiratory deposition per kilometre occurring while walking, followed by a rickshaw ride.
The study states the highest PM 2.5 exposure was recorded through autorickshaws, which resulted in a mean PM 2.5 concentration of 266 g/m3 (± 159 g/m3), followed by walking 259 g/m3 (± 102 g/ m3). The lowest readings were recorded in the Metro (72 ± 11 g/m3), followed by an air-conditioned car (89 ± 30 g/m3). Exposure was moderate in buses (113 ± 14 g/m3 ) and non-AC cars (149 ± 13 g/m3 ), however, open windows and local factors caused a surge in PM2.5 concentration for both these modes of transport, the study says. All readings were collected in February 2018.
“Closed, air-conditioned transport modes were shown to be the best modes for avoiding high concentrations of PM2.5, however, other factors
(e.g. time of the day, window open or closed in the vehicles) affected exposure levels significantly,” said the study.
Per kilometre, the study said, the highest respiratory deposition doses (RDDs) were highest for walking, followed by a rickshaw. While the RDD value for walking was estimated at 84.7 ± 33.4 g/ km, it was 15.8 ± 9.5 g/km for rickshaw, followed by 9.7 ± 0.9 g/km for a non-AC car.
“Different modes of transport were analysed during the winter period when pollution levels are at their peak and their impact on the respiratory system is much more. While closed environments are considered equally challenging, we found air-conditioned cars and the Delhi Metro to both be faring extremely well and the airconditioning here plays a key role in reducing the impact of PM 2.5, while also allowing ventilation,” said Kamal Jyoti Maji, co-author and researcher at Northumbria University.
The study noted slight route deviations were taken for rickshaw and buses. “The region from Prithviraj Road to Janpath Road is less populated and comprises key government offices and embassies. The area between Janpath Road to Connaught Place is mainly of government authorities’ structures, small retail infrastructures with a large hotel. The final part of the route, Connaught Place, is a series of ring roads. It is surrounded by a central park and markets and is often congested due to large number of rickshaws and cars using the area,” said the study.
Maji says the PM 2.5 exposure during walking and rickshaws was also much higher than the ambient PM 2.5 concentration in the surrounding, which was around 146 ± 53 micrograms per cubic metre.
Anil Namdeo, another coauthor, says the study aims to encourage the implementation of integrated and intelligent transport systems while also educating commuters on ways to reduce exposure levels. “The impact on the health of a commuter and the exposure levels, especially during winters, can create both short-term and long-term problems,” said Namdeo.