Air pollution spikes to dangerous levels as firecrackers go off across city

Mumbai: As firecrackers went off across the city on Sunday night, air pollution also touched dangerous levels, with particulate matter concentrations settling at their highest since January.

Though Mumbai’s overall Air Quality Index (AQI) on Monday morning was in the moderate category at 145, hourly data from 19 continuous ambient air quality monitoring stations (CAAQMS) across the city operated by the Maharashtra Pollution Control Board (MPCB) and SAFAR, showed that the immediate, localised impact of bursting firecrackers was much more significant.

“The AQI is calculated as a 24-hour average. Given the significant variations in concentration of pollutants that can happen within a single day, this average tends to mask the very high spikes that are seen within the permissible window of time for bursting crackers,” said Gufran Beig, project director and meteorologist at SAFAR. “These pollutants then linger on due to lower temperatures at night and slower wind speeds.”

At Navy Nagar, the southernmost AQI monitor in the city, the concentration of PM2.5 touched 256ug/m3 at 3am, more than four times the daily safe limit of 60ugm/m3, settling at 144ug/m3 by Monday afternoon. At Colaba, PM2.5 levels began climbing around 12am, touching 238ug/m3 at 4am.

In Mazgaon, PM levels entered the ‘very poor’ level between 4am and 12pm, touching a maximum of 326ug/m3. The highest spike in air pollution happened around Santacruz airport, where PM2.5 levels touched a whopping 419ug/m3, in the ‘severe’ category. Similar spikes were also seen at Vile Parle (W), Powai, Bandra Kurla Complex, Worli, Deonar, Mulund (W) and Chakala, as per data from stations run by the MPCB and IITM.

“There is a noticeable spike in both PM2.5 and PM10 levels soon after 10pm, which happens every year on Diwali. This year, the festival has coincided with a change in weather with the monsoon withdrawing from over Maharashtra. So there is dry, cool air blowing at night which is actually not favourable for dispersal. The pollutants accumulated in the early morning hours and were dispersed by warmer, faster winds during the morning and afternoon,” an environment engineer working with an accredited environmental consultancy in Mumbai, who asked not to be named, said.

In 2019, Mumbai had recorded its cleanest Diwali and post-Diwali air in five years (AQI 75) owing to high wind speed under the influence of Cyclone Kyarr in the Arabian Sea. The year 2020 was the second cleanest post-Diwali air since 2015, with an AQI of 107. In 2021, the city’s post-Diwali AQI was the highest in the last four years, touching 215, in the ‘poor’ category. This is as per data only from 10 stations operated by SAFAR.

In January, a dust storm led to Mumbai’s worst-ever air quality index (AQI) on record, pushing it to ‘severe’ category with an index value of 502.