Vehicular emissions in Mumbai double in five years, says study

The transport sector’s contribution to air pollution in the city has almost doubled in the last five years, reveals a new study by the System of Air Quality Weather Forecasting and Research (SAFAR), an initiative under the Indian Institute of Tropical Meteorology (IITM), Pune, which is under the Union ministry of earth sciences

The transport sector’s contribution to air pollution in the city has almost doubled in the last five years, reveals a new study by the System of Air Quality Weather Forecasting and Research (SAFAR), an initiative under the Indian Institute of Tropical Meteorology (IITM), Pune, which is under the Union ministry of earth sciences.

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The study, conducted over one year between 2019 and 2020, shows that vehicular emissions contributed 30.5% of all PM2.5 particles in Mumbai during the study period. This is up from 16% contributed by the same sector in 2016-17, as per a previous source apportionment study conducted by SAFAR.

PM2.5 refers to small, ultrafine particles less than 2.5 microns in diameter, which can enter the bloodstream via the respiratory system and travel throughout the body, causing health problems such as asthma, lung cancer and heart disease. PM2.5 is made up of hundreds of different chemicals and is emitted by a range of sources, from construction work to industrial smokestacks, power plants, open fires and automobiles.

According to SAFAR, other prominent sources of PM2.5 in Mumbai include the industries and power sector, which contributed 18% of the city’s overall PM2.5 pollution load. Another 15% came from domestic sources - such as residential cooking practices in slums, burning of garbage, wood, cow dung and other cheap fuels.

Windblown dust (referring to transboundary pollutants originating outside of the city) made up another 15% of PM2.5 pollutants, while the remaining 21.5% is estimated to have come from an amalgam of sources, including solid waste plants, brick kilns, crematoria, aviation and various miscellaneous activities.

A similar source estimation for PM2.5 pollutants by SAFAR in 2016-17 had shown transport accounted for 16% of this distribution, while industry and power was the biggest contributor at 36%. Domestic sources of PM2.5 made up 27% of the inventory, while the share of windblown dust was 21%.

Experts said this trend is indicative of the substantial threat posed by vehicles powered by conventional, non-renewable fuels like petrol and diesel. Such vehicles have exploded in number on city streets in the past decade. Gufran Beig, senior scientist and the founding project director of SAFAR, said, “This (trend) is a combination of both an increase in the number of vehicles in Mumbai and more stagnation at traffic junctions leading to congestion.”

While all major Indian cities have witnessed a significant rise in the number of vehicles over the past decade, Beig pointed out that cities like Delhi have pushed for the adoption of compressed natural gas (CNG), in both public transport and private vehicles. “The uptake of clean fuel has been very less across Mumbai. The majority of the vehicles continue to be petrol and diesel,” he said.

As per data with the Maharashtra transport department, Mumbai has already registered at least 40 lakh new vehicles, a threshold which it crossed earlier this year. Of these, 11.6 lakh are private cars and 24 lakh are two-wheelers. This is up from 30.69 lakh vehicles registered by 2016-17, and 20.28 lakh vehicles in 2011-12. A recent, state-wide economic survey estimated that there are roughly about 2,000 vehicles per kilometre of road in Mumbai. As the city gets more congested and more vehicles idle in traffic, the more emissions they generate.

That automobiles are a significant threat to clean air in the city was highlighted as early as 1982, when the Indian Journal of Environmental Protection had published a study titled Level of Air Pollution in Bombay. “The urgent task is to reduce the number of cars and their movement in the city. It should not be difficult to provide an efficient public transport system,” the study said.

Though Mumbai’s favourable position along the coastline helps in the quick dispersal of pollutants, experts have expressed concern over the SAFAR study’s findings. “We may soon approach a natural tipping point where environmental buffers will not make any difference to the overall pollution scenario. A sector-wise plan to tackle emissions at source is needed,” said Beig.

Commenting on the preliminary results, Anumita Roy Chowdhury, executive director of research and advocacy at the Centre for Science and Environment, Delhi, said, “Even though we have to see the exact numbers, the source apportionment analysis seems logical in identifying the transport sector as a rapidly growing source.” She also pointed out that the increase in vehicles coincides with a slowdown in the establishment of new industries and power plants around Mumbai, which is consistent with SAFAR’s findings.