Introduction
COVID-19 crisis is caused by coronavirus 2 (SARS-CoV-2), a severe acute respiratory syndrome (Jandrić 2020). Currently, India is undergoing a 4.0 phase of confinement and has 190,649 confirmed COVID-19 cases and 5406 deaths until May 31, 2020 (covid19india.org). Confinement in India or any part of the world ensures that all transportation, factories, construction work, restaurants, and other social places should be closed to follow the social distancing on a serious note. These confinement phases not only help to control the spreading of infection, but also offer improvement in planetary health.
Air pollution is a major subgroup of environmental pollution which poses a serious threat to the ecosystem. The risk of global sustainability can be reduced by controlling anthropogenic activities responsible for the emission of air pollutants in the environment. India accounts for having one of the most polluted capitals and cities within the globe (Guttikunda et al. 2019). During a study conducted by the Central Pollution Control Board (CPCB), the Ministry of Environment, India confirmed significant impact of 1-day confinement in the country (March 22, 2020), named as “Janata Curfew” of 14 h from 7 a.m. to 9 p.m., on air quality in terms of reducing pollutant level when compared with previous day data (Barkur and Vibha 2020) (source CPCB, India).
Keeping in view the above, in the present study, impact of COVID-19 confinement on air qualities among the populous site of four major metropolitan cities in India (i.e., site 1—ITO, Delhi; site 2—Worli, Mumbai; site 3—Jadavpur, Kolkata; and site 4—Manali Village, Chennai) were determined by evaluating alteration in PM2.5, PM10, NO2, NH3, SO2, CO, and ozone level from January 1, 2020 to May 31, 2020. Pearson product-moment correlation coefficient (PPMCC)-based model analysis was also proposed which determine the impact of COVID-19 pandemic confinement on air quality. Overall pandemic confinement has allowed the environment for detoxifying and renews itself in a lesser human interference phase. Environmental analysts designate it as a silver lining in terms of decreased carbon and waste emission but recognize it as a flawed perspective due to the expectation that the AQI levels to return as the coronavirus vanish and in some cases, they could come back strongly.