Abstract
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.
Highlights
Air pollution remains one of the most important public health concerns across the globe, contributing substantial premature mortality with greater impact in developing nations (Mannucci and Franchini, 2017; Barzeghar et al, 2020)
The present study aims to assess the changes in air quality parameters during the implementation of the lockdown measures in the four major metropolitan cities of India, viz., Delhi, Mumbai, Kolkata and Chennai for a one-month period (15 days before lockdown and 15 days after the implementation of lockdown)
After two weeks of lockdown, air pollution has significantly decreased with considerable differences in concentration of major pollutants
Summary
Air pollution remains one of the most important public health concerns across the globe, contributing substantial premature mortality with greater impact in developing nations (Mannucci and Franchini, 2017; Barzeghar et al, 2020). As per World Health Organization (WHO), it has been estimated that 4.2 million premature deaths globally are linked to ambient air pollution. The pollutants with the strongest evidence for public health concern include particulate matter (PM2.5 and PM10), nitrogen dioxide (NO2), sulphur dioxide (SO2) and ozone (O3) (WHO, 2020a). India being the second most populous country of the world, is severely burdened with the hazardous effects of air pollution. Owing to increasing industrialization across the country, progressive worsening of ambient air pollution remains a great challenge for sustainable development and public health reforms (Gordon et al, 2018)
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