PUNE: Confined to home over Covid-19 fears and social distancing may not be ideal for everyone, but it definitely has a silver lining — a sharp drop in pollution levels in many parts of the country.

Air quality data from Pune-based Institute of Tropical Meteorology’s (IITM) System of Air Quality Forecasting and Research (SAFAR) show that there was a 45-50% dip in the pollutant, Oxides of Nitrogen (NOx), in Pune, Mumbai and Ahmedabad from March 5-19.

While the data do not show any significant drop in NOx in Delhi in the past week, PM2.5 was on the decline.

NOx is mainly produced by vehicles. NOx levels during this period were lower by 45% in Pune and Mumbai, and over 50% in Ahmedabad when compared to the same period last year.

In Pune, NOx levels in Hadapsar reduced by 70%. In Pashan and Katraj, there was a significant drop in NOx, but no change in PM2.5. Shivajinagar saw a negligible reduction in both NOx and PM2.5 levels. In the Lohegaon airport area, there has been a reduction in PM2.5 levels from March 1.

IITM sources said individual locations in all cities were showing a significant change in NOx levels. “Generally, fossil fuel emissions, mainly from vehicules, are a major source of NOx (60-80%) and PM2.5 (35-50%) in four SAFAR cities — Delhi, Mumbai, Pune and Ahmedabad,” the source said.

After the Covid-19-related shutdown in the cities, the impact of reduction in vehicular traffic was analyzed for March, comparison with the same period in 2019 and 2018.

Social distancing causes 50% plunge in pollution

The source said, “In fair weather conditions, NOx levels are mainly controlled by vehicular emissions, though weather changes cannot be ruled out.”

Sources said that vehicular traffic also increases PM2.5 levels via fossil fuel and resuspended dust emissions. “Although reduced vehicular traffic has lowered PM2.5 levels, this may have been balanced out by higher resuspended dust emissions caused by faster speed of vehicles on almost empty roads,” the source said.

Hence the slight-to-no reduction in PM2.5 levels in some locations.

According to data, there’s a significant (50%) reduction in NOx levels (fluctuating) in PMC and PCMC limits from March 6 to 19. In Ahmedabad, there is a significant reduction in NOx pollution, while PM2.5 levbels have been dropped since March 7.

In Mumbai, NOx levels have dropped by 30% from March before increasing again from March 16 with no change in PM2.5.

In Delhi NCR, there appears to have been a reduction in PM2.5 levels from March 5and a slight dip in NOx between March 8-13.