Air Pollutants During COVID-19 Lockdown Period in India

Recent studies have indicated that certain atmospheric pollutants had significantly reduced in several countries during the lockdown period imposed to curb the spread of SARS-CoV-2-Virus. The Government of India declared the first lockdown from the end of March 2020, which continued till June 2020 in most Indian states. The present study compares the air quality indicators nitrogen dioxide (NO2), sulfur dioxide (SO2), carbon monoxide (CO), and ozone (O-3) across India, during the months of March-August 2020 and the same period in 2019. The application of satellite information from NASA - Ozone Monitoring Instrument and Atmospheric Infrared Sounder were used to compare the quantum of air pollutants. The temporal variation of the air pollutants was studied using satellite imagery and geo-statistics on a monthly, national average basis, to assess the overall impact of the lockdown. NO2, SO2, and O-3 showed some level of reduction during the period of study in 2020 when compared to 2019, whereas CO levels had gone up in 2020. NO2, a pollutant mainly arising from motor vehicle combustion, reduced by 3.98-12.1 % in 2020 as compared to the same study period in 2019 and in April 2020, when there was a complete lockdown, it had dropped maximally (by 12.1 %). The reduction in SO2 levels in 2020 ranged from around 0.5-9% but only during April-June 2020, whereas there was an increase in March, July, and August 2020 when compared to 2019. Despite a reduction in NO2, the O-3 levels (which are dependent on NO2 levels) saw an increase in the atmosphere during March-May 2020 by 1.9-5 % , and decreased during June-August 2020. The CO levels in the atmosphere did not reduce during lockdown; instead, it peaked in March, April, and May 2020, when compared to 2019, possibly due to incomplete combustion of materials containing carbon materials like wood, plastics, etc. This study demonstrates that it is possible to rapidly reduce atmospheric pollution in India. However, since the level of certain pollutants like O-3 are dependent on others like NO2, reducing the atmospheric pollution globally is a sustained and concerted effort by all concerned.