Impact of lockdown on air quality during COVID-19 pandemic: A case study of India.

Abstract

It is crucial to study air quality and its impact on human health, as it can leave not only short-term effects but also have long-term effects, especially on people suffering from cardiovascular and lung diseases. During the COVID-19 pandemic, a major lockdown of almost 70 days in four different phases was announced in India. Due to this exercise, many visually observed a drastic change in air quality; however, actual quantifications were limited. Therefore, there is a need to quantify how air quality changed from before to during and post-lockdown scenarios. This study quantifies the COVID-19 India lockdown impact on air quality by analyzing the change in major air pollutants such as SO2, NO2, CO, O3, PM2.5, and PM10. The major objectives of this study are to quantify the change in major air pollutants across India during the lockdown and to identify their trends and respective hotspots. In order to achieve these objectives, air quality estimates are obtained from Sentinel 5P satellite, while PM2.5 and PM10 values are taken from Central Pollution Control Broad’s ground monitoring stations. For temporal analysis, different time intervals starting from before the lockdown (i.e., March 1, 2020) till the end of the fourth lockdown (i.e., May 31, 2020) were analyzed across India. Results state that (1) There was a significant decline of − 48.11% and − 11.56% in concentrations of SO2 and NO2, respectively, after averaging values at their respective hotspots (2) A decrease of − 6.78% and − 0.42% was observed in O3 and CO concentration during the lockdown period in the year 2020 compared with the same period in the year 2019. (3) For PM2.5, Kolkata had the maximum drop of − 83.28%, while Bengaluru had the least drop of − 38.86%, whereas, for PM10, Kolkata had the maximum drop again of − 80.53%, while Delhi, on the other hand, had an increment of 13.42% at the end of the fourth lockdown. The results indicate the indirect benefit of the COVID-19 lockdown on air quality. It also provides a better understanding of hotspots and trends that can aid the government and the policy-makers to identify precautionary measures to reduce air pollution and prioritize hotspots.