Covid-19: Lockdown purifies cities of noxious city air

The lockdown announced by the government to contain the spread of the novel coronavirus seems to have led to some inadvertent benefits. Air quality in most Indian cities has fallen into the categories of ‘good’ and ‘satisfactory’, with only two -- Kalyan in Maharashtra and Guwahati in Assam -- out 102 cities where air quality is continuously monitored reporting poor quality.

There has been a substantial improvement in air quality in metro cities since the 21-day lockdown began, with most industrial units temporarily shutting down operations and most vehicles keeping off the road. Almost all of 36 functioning air monitoring stations in the capital reported a drastic drop in air pollution levels. The air quality monitoring station at ITO, one of Delhi’s busiest crossroads, reported a PM2.5 (particulate matter below the size of 2.5 microns) level of 50 micrgram per cubic metre (ug/m3) on Thursday. On March 20, the value was 125 ug/m3. Similarly, the unit monitoring the busy Mathura Road reported PM2.5 levels dropping nearly 4-fold to below 25 ug/m3 on Friday. Similarly, two monitoring stations in Mumbai at Bandra and Powai reported healthy PM2.5 levels of 15 and 30 ug/m3 on Friday.

"The improvement in air quality in the capital is very significant," said Mohan P George, senior scientist in charge of air quality at Delhi Pollution Control Committee.

“We looked at air quality in four metro cities -- Delhi, Mumbai, Bengaluru and Kolkata. Before and after the Janta Curfew on March 22, we observed a sharp dip in air pollution levels in these cities,” said Anumita Roychowdhury, Deputy Director General of the New Delhi-based NGO Centre for Science and Environment, who has been on the forefront of the clean air campaign for more than three decades.

As compared to days preceding the Janata Curfew, air pollution levels dropped by 61 per cent in Mumbai and 60 per cent in Kolkata. Delhi on the other hand reported a drop of 26 per cent, Roychowdhury said. For the comparison, the CSE team took the average of three days (March 17-19 and March 20-23) for number crunching. This was because Mumbai went into the lockdown earlier than other three cities. The air pollution levels have further dropped since then as the country as a whole witnessed a complete lockdown.

Across India, among the cities that reported ‘good’ air quality are those cities that are notorious for their foul air. While air quality improved in Kanpur to 50 ug/m3, Bhiwadi, an industrial town in Rajasthan, reported one of the best numbers among Indian cities at 44 ug/m3. So was the case with many cities in Punjab, including Patiala, Ludhiana and Jalandhar. With most industrial units in its neighbourhood closed down, people in Chandigarh, too, can breathe easy with a total air pollution level of 40 ug/m3.

Even a temporary improvement in air quality has a significant health impact. It can bring down hospital admissions relating to respiratory ailments and heart problems significantly. Even though there are no proper studies, the empirical data during the 2008 Beijing Olympics has shown that, said Roychowdhury.

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