Winter report card: ‘PM2.5 levels above average at 7 of city’s 10 air checkpoints’

Seven of the 10 pollution-monitoring stations in the city recorded higher PM2.5 (suspended pollutants 2.5 microns or smaller in size) than the city’s average between

Seven of the 10 pollution-monitoring stations in the city recorded higher PM2.5 (suspended pollutants 2.5 microns or smaller in size) than the city’s average between November 1, 2019 and January 31, 2020 (92 days), revealed a report by the Centre for Science and Environment (CSE). The report, which looked at Central Pollution Control Board data, revealed that five stations recorded higher concentration of nitrogen dioxide (NO2), a major component of vehicle exhaust, than the average.

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According to the study, there was an overall 32% rise in three-year averages between 2012-14 and 2016-18 of PM10 (particulate matter of 10 micron or lesser), and a 59% reduction in PM10 concentration was needed from the 2016-18 levels for cleaner air.

“Overall, annual pollution levels in Mumbai are going up, but this study has for the first time shown pollution hot spots and issues through a granular view during different seasons,” said Anumita Roychowdury, executive director (research and advocacy), CSE.

“However, air-quality data availability for Mumbai has improved. It was patchy in previous year, but this year we could find much more inputs from official monitoring stations, which helped spatially map pollution in the city, especially for seasons.”

The average PM2.5 concentration between November and February 10 was 75µg/m3 in Mumbai. The area around the international airport in Santacruz-Vile Parle was the most polluted, with levels at 85 µg/m3, followed by Sion at 82 µg/m3 for PM2.5. Colaba, Kurla, Vile Parle (West), Worli, and Vasai recorded levels much above the mean for the city.

The CSE study also found that 9 of 10 stations (except Bandra) did not meet 24-hour standards of 60 microgrammes per cubic metre (µg/m3) for PM2.5 per day over 92 days. “Bandra looked cleaner because there were data gaps,” said Roychowdury.

For NO2, against the average of 40µg/m3, Sion was the most polluted at 75 µg/m3, followed by Kurla at 64 µg/m3. Borivli had the lowest concentration of PM2.5 and NOx this winter.

According to the last available source-apportionment study by air pollution research group UrbanEmissions from 2018, industrial emissions were responsible for maximum PM2.5 (49%), followed by the transport sector (vehicular exhaust) at 19%. For NOx, industries (59%) and transport (29%) were major contributors. Dust and open-waste burning were other contributors to PM2.5 levels. Diesel generator sets and brick kilns were other NOx contributors.

“We need to know how close we are to these pollution sources and what we are inhaling daily,” said Roychowdhury. “There is an immediate need to identify and publish a latest source-apportionment study for Mumbai and level of exposure during different seasons.”

On Monday, the city recorded its most polluted air day since January 2019 with the air quality index (AQI) for PM2.5 pollutant at 281 (poor), according to the System of Air Quality Weather Forecasting and Research (SAFAR).

The Maharashtra Pollution Control Board (MPCB) said pollution levels were much lesser this winter. Cyclones in December reduced air pollution. “The state government has taken the lead to tackle air pollution as a primary environmental problem, with MPCB at the forefront. The number of ‘good’ air days are increasing as compared to previous years, even during winter, and location-wise sources are being addressed through our city-specific action plan, which is under implementation,” said VM Motghare, joint director (air quality), MPCB.