Impacts of COVID-19 lockdown on ambient air quality: Statistical analyses of available data on urban West Bengal (India)

COVID-19 pandemic and consequent unavoidable lockdown left an unprecedented shock on social and economic life. Present study aimed to evaluate the impacts of COVID-19 lockdown on the ambient air quality of urban areas of eastern Indian state West Bengal. During lockdown period, Air Quality Index (AQI) was mostly found in 'Good' or 'Satisfactory' and sometimes, in 'Moderate' categories, and rarely, in 'poor' category. AQI was in 'Good' category for most of the lockdown span at Siliguri (67%) followed by Kolkata (44%), Howrah (38%) and Asansol (25%). Based on average AQI ranges: lockdown period (48.68- 62.12) < same period before 1 year (75.09-89.81) < Period 3 months before lockdown (175-206), it can be stated that AQI category was better during lockdown compared to the other two at all study areas. In Kolkata overall air pollutant levels except ozone (p>0.05) decreased significantly during lockdown. Similarly, PM2.5, PM10 and NO2 level reduced in Howrah. Beside, no significant changes observed for NH3 and SO2 concentration in Howrah compared to one year before. Apart from PM2.5, NO2, NH3 and SO2 level of previous year, mean concentration of PM10, CO, O-3 showed significant drop at Siliguri during lockdown. Ambient air quality parameters except SO2 showed remarkable decline in Asansol also during lockdown. It can be concluded that COVID-19 lockdown exerted positive effects from environmental health perspective. It improved overall ambient air quality parameters of urban areas of West Bengal. Proper planning and policy making should be given utmost priority to control air pollution in the present 'new normal' COVID-19 scenario.