‘City’s air in winter nine times more polluted than monsoon’

The weekly averages of PM2.5 levels in the city during the winter months of November and December 2019 was nearly nine times the weekly average concentration witnessed

The weekly averages of PM2.5 levels in the city during the winter months of November and December 2019 was nearly nine times the weekly average concentration witnessed during monsoon months (June to September 2019). These were among the findings of a study by city-based air quality monitoring group UrbanSciences and Indian Institute of Technology-Kanpur (IIT-K), with assistance from Delhi-based Shakti Sustainable Energy Foundation.

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The study analysed the Centre’s air quality monitoring data for 2019, for Mumbai, Lucknow, Raipur, Jaipur and Ahmedabad. In Mumbai, against the average PM2.5 concentration ranging around 100 microgrammes per cubic metre (µg/m3) in the monsoon, peak levels increased to 585 µg/m3 during the third week of November and 922 µg/m3 in the last week of December. The study also found PM2.5 levels in the city are around 30% higher at 8am (70 µg/m3) while at 2pm, they are at 50 µg/m3, which is below the daily safe standard of 60 µg/m3.

Average PM2.5 concentrations across 10 monitoring stations in Mumbai showed Sion to be the most polluted location over six months (31.5 µg/m3), followed by Kurla (29.6 µg/m3), the area around the international airport in Santacruz (28.8 µg/m3), Colaba (27.2 µg/m3) and Vile Parle (26 µg/m3). The least polluted area was Borivli (17.1 µg/m3).

While Mumbai had the lowest pollution levels of the five cities, the researchers said the data may not be representative of the city’s actual air quality. “We assessed official data for the city [Mumbai], which will be submitted in the form of an aggregate for 2019 under the Centre’s National Clean Air Programme (NCAP). The results show the air quality situation was ‘good’ for Mumbai in 2019, but the reality is different. Air quality of different hotspots in the city is not getting captured in this data,” said Ronak Sutaria, founder and director, UrbanSciences.

A scientist associated with the study, on condition of anonymity said, “Mumbai needs nearly 90 to 100 air quality monitors to get spatially accurate data of air pollution hotspots combined with biennial measurement-based source apportionment studies to track emissions.”

The most polluted days during the winter period saw PM 2.5 concentration ranging between 58 and 108 µg/m3, with the average peak PM2.5 level of 92 µg/m3. In contrast, average peak levels were at 25 µg/m3 during the monsoon months when PM 2.5 concentration ranged between 15 µg/m3 to 40 µg/m3. “This shows that the last two weeks of November and through December, air pollution was significantly unhealthy for people with sensitive breathing conditions,” said Sutaria.

City doctors confirmed this finding. “I have personally recorded a 40% rise in patients diagnosed with asthma, bronchitis, lung fibrosis etc. Owing to exposure to poor air quality during winter months in the early hours of the day, children are at twice the risk than adults to develop chronic obstructive pulmonary disease, bronchitis; hypersensitivity pneumonitis and asthma,” said Dr Sanjeev Mehta, pulmonologist, Lilavati Hospital.

On the high levels of PM 2.5 concentration at 8am, the city’s School Bus Owners’ Association (SBOA) confirmed 7am to 9am to be peak travel times. “Apart from 6,000 buses, 16,000 of the 20,000 vehicles that take children to school are illegal and are diesel or petrol-based. Despite court orders to phase out these vehicles, there has been no action, putting the lives of children at risk,” said Anil Garg, president, SBOA.