Special Issue on COVID-19 Aerosol Drivers, Impacts and Mitigation (VI)

Jasbir Singh Bedi This email address is being protected from spambots. You need JavaScript enabled to view it., Pankaj Dhaka, Deepthi Vijay, Rabinder Singh Aulakh, Jatinder Paul Singh Gill

School of Public Health and Zoonoses, College of Veterinary Science, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana 141004, India



Received: May 9, 2020
Revised: July 4, 2020
Accepted: August 12, 2020

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

Download Citation: ||https://doi.org/10.4209/aaqr.2020.05.0209  

Cite this article:

Bedi, J.S., Dhaka, P., Vijay, D., Aulakh, R.S and Gill, J.P.S. (2020). Assessment of Air Quality Changes in the Four Metropolitan Cities of India during COVID-19 Pandemic Lockdown. Aerosol Air Qual. Res. 20: 2062–2070. https://doi.org/10.4209/aaqr.2020.05.0209


  • COVID-19 lockdown reduced air pollutants in Delhi, Mumbai, Kolkata and Chennai.
  • Nearly 50% decrease in NO2, PM10 and PM2.5 concentrations was observed.
  • Significant (p < 0.05) increase in O3 levels observed in Delhi during lockdown.


In view of emerging threat of COVID-19 pandemic, stringent lockdown measures have been implemented in India since 25th March, 2020. The present study aims to assess the changes in air quality before and during lockdown in the four major metropolitan cities of India viz., Delhi, Mumbai, Kolkata and Chennai. The data on major air quality parameters and meteorological parameters was collected for 15 days before lockdown (i.e., March 10th–March 24th, 2020) and 15 days after implementation of lockdown (25th March–April 8th, 2020). The lockdown measures reflected a significant reduction in air pollutants, most significant fall was estimated for NO2 (29.3–74.4%) while the least reduction was noticed for SO2. On the contrary, levels of ground level ozone were found to be increased (except in Mumbai), could be related to the lower utilization of O3 owing to decrease of NOx in the environment. Since, the lockdown period has been extended, therefore further reduction of most pollutants is expected. Among the various metrological parameters, significant increase in diurnal temperature was observed at Delhi, Kolkata and Mumbai, however relative humidity has changed significantly only in Mumbai. In the absence of any major violent meteorological phenomena in India during recent months the significant difference in air quality parameters could be majorly attributed to the effect of lockdown measures. However, the regional differences may be because of the local emission of pollutants and the prevailing effects of secondary pollutants. These observations highlight the contribution of anthropogenic sources in air pollution, therefore, sustainable polices for mitigation of air pollution are essential in India.

Keywords: Air Pollution; Air Quality; COVID-19; India; Lockdown; Metropolitan cities.


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Aerosol Air Qual. Res. 20 :2062 -2070 . https://doi.org/10.4209/aaqr.2020.05.0209  

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