Worst to best: How this Bengaluru area's pollution levels dropped during lockdown

The city's Bellandur area, infamous for the heavily contaminated lake nearby, was unsurprisingly Bengaluru's most polluted before this year's lockdown was imposed on March 21. But the Air Quality Index (AQI) of over 160 dropped dramatically in June to less than 40, turning the area into the city's least polluted.

Disclosed by Ambee, an environmental firm that supplies hyper-local air quality data in real time, the findings also threw more light on why Madanayakanahalli and Nelakadiranahalli gained notoriety as the city's most polluted areas in June: Stubble burning, as some of these areas are on the outskirts and close to agricultural farms.

The positive eco-impact of the lockdown was perceptible even in July, when many areas recorded AQI below 40. However, once the unlock process gathered steam, the gains were reversed. Once the lockdown was lifted, areas such as Peenya recorded AQI in excess of 60 due to resumption of industrial activity, the study found.

RR Nagar, Kumbalgodu Gollahalli, Kumbalgodu area, Jalahalli West and Singanayakanahalli were the five least polluted areas in the city in July. All these areas had an AQI of less than 35. Among the most polluted during the month were Madanayakanahalli, Dasanapura area, Chikkabidarakallu and Peenya Small Industries.

In June, besides Bellandur, adjoining areas, Panathur, Yemalur and Marathahalli Colony, and Basaveswaranagar also recorded low AQI, below 35.

As the Ambee study notes, in Bengaluru, Delhi and Chennai, the apparent temperature (temperature that is felt) was 40% lower than usual due to reduced heat trapping and improved air quality during the lockdown period. "In this period between March and July, India has had the cleanest air in the last decade."

Other cities, too, experienced a similar trend. "Between March and July, Mumbai’s AQI significantly reduced from 100 to below 60. In June, Mumbai’s AQI was as low as 40 due to rain, the shutting down of industries, manufacturing and public transport."

Prior to the lockdown in March, Delhi had an average monthly AQI of 200, which went up to 300. "During the 15-day lockdown that started in March, Delhi’s average AQI came down to 120 due to lesser vehicular movement and minimal human activities. In July, Delhi's average AQI level was below 80 mainly due to rains," the study noted.

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