Bengaluru's air quality vastly improved during lockdown: ISEC study

Delhi and Bengaluru topped the five mega cities of the country in the decline of air pollution during the lockdown, a study by researchers at the Institute of Social Economic Change (ISEC) has found.

Four researchers looked into four major contaminants in air: nitrogen dioxide (NO2), sulphur dioxide, carbon monoxide and aerosol optical depth. Spatio temporal data from Sentinel 5P and MODIS imagery was used to analyse the quality of the air during the lockdown and compare it with the previous year.

A comparison of mean values showed that both Bengaluru and Delhi saw a decline of about 42 per cent in NO2 in April 2020 compared to the same month in the previous year. They were followed by Mumbai (35 per cent), Chennai (26 per cent) and Kolkata (10 per cent). When it comes to Sulphur Dioxide, Chennai saw the biggest reduction in percentage terms (81 per cent), followed by Bengaluru (57 per cent) and Delhi (42 per cent) although the improvement in the national capital was huge in terms of molecules of light per square metre.

An analysis of carbon monoxide for the same period also showed a significant improvement. However, Bengaluru and Kolkata had increased aerosol optical depth compared to the previous year for which researchers cited local emission sources as the reason. Aerosol optical depth refers to how much direct sunlight is prevented from reaching the ground by dust, smoke and pollution.

Prof Sunil Nautiyal from the ISEC said the research paper was part of an ongoing study and sought to push for structural changes in the policy to ensure the "unprecedented improvement in air quality" were not lost due to Unlock.

"There is an urgent need to shift to a low-emission economy. That not only requires changes in policies but also structural changes in the economy to complement such measures. From decisions on work-from-home to large-scale infrastructure, the government has to weigh the long-term benefits of its decisions," he said.