Mumbai’s daily peak air pollution falls 80% amid coronavirus lockdown: CSE study

The pollutant-measuring indicator — air quality index (AQI) — in the city has remained in the ‘satisfactory’ category for the past one week now due to the lockdown

The pollutant-measuring indicator — air quality index (AQI) — in the city has remained in the ‘satisfactory’ category for the past one week now due to the lockdown in view of coronavirus pandemic, but researchers have now assessed improvements using a more focused approach.

The Centre for Science and Environment (CSE), Delhi, analysed the hourly trend in particulate matter (PM2.5) and nitrogen dioxide (NO2) for Mumbai and Navi Mumbai on regular days (average of March 18 and 19), during lockdown (March 25 and 26), and also last Sunday (March 22) — the one-day Janta Curfew.

The daily peak NO2 concentration fell by 85% during lockdown and 83% on the Janta Curfew day in Mumbai, and 72% and 86% in Navi Mumbai. The sharp drop in levels was attributed to lack of vehicles, industrial and construction activities.

“The drop in NO2 shows the hourly pollution trend is greatly influenced by traffic peaks on regular days, which nearly flattened out after the lockdown. This analysis brings out the pronounced effect of traffic on air quality trends and on exposures to toxic vehicular pollution. With less traffic, hourly trends have plummeted,” said Anumita Roy Chowdhury, executive director (research and advocacy), CSE.

A similar evaluation was done for PM2.5, which showed a similar pattern but with more variability as it is also influenced by other sources, the study said. The data showed daily peak during lockdown fell by 52% compared to a regular day, 65% during Janta Curfew for Mumbai, and for Navi Mumbai 59% and 76%.

Overall, CSE calculated the 24-hour average before and after lockdown fell by 61% for PM2.5 and 68% for NO2 from March 9 to March 25.