Less traffic, cool winds help city breathe easy

The city witnessed a considerable decline in air pollution on Thursday. The pollutant-measuring indicator — air quality index (AQI) — fell from 272 (poor) on Tuesday

The city witnessed a considerable decline in air pollution on Thursday. The pollutant-measuring indicator — air quality index (AQI) — fell from 272 (poor) on Tuesday to 172 (moderate) on Wednesday and 130 (moderate) on Thursday for PM2.5 pollutant — breathable particulate matter which is 2.5 microns in size or smaller — according to the System of Air Quality Weather Forecasting and Research (SAFAR).

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Temperatures dropped, with a 4 degree Celsius drop in the day temperature. The maximum temperature in the suburbs dropped from 37.5 degrees Celsius on Monday to 37 on Tuesday, 34.4 on Wednesday, and 33.1 degrees Celsius on Thursday, 0.2 degree Celsius above normal. South Mumbai recorded 36 degrees Celsius on Monday, which dropped gradually to 32.2 degree Celsius on Thursday, 0.7 degree Celsius above normal. While the city was able to enjoy cleaner air quality, neighbouring Navi Mumbai still recorded ‘very poor’ AQI at 316. Even PM2.5 and PM10 (larger coarser particles) concentration, which was almost twice the safe limit on Tuesday, increased to almost the safe limit on Thursday, according to SAFAR.

Researchers said weather factors and reduction in pollution sources in the city both witnessed a change over the past two days.

“On one hand, the wind direction over Mumbai has changed from hot and dry easterly winds to cooler, north-westerly winds, with the sea breeze setting in at the right time, reducing both temperatures and pollutant carrying capacity in the air,” said a senior researcher from SAFAR. “Secondly, pollutants from major sources like vehicles and industries have witnessed a decline due to the Covid-19 outbreak, which has had a marginal impact on air quality. An AQI of 149 (moderate) has been predicted for Friday while a clear sky with similar temperatures as Thursday can be expected.