Abstract
Various countries across the globe have been affected by different COVID-19 waves at different points in time and with varying levels of virulence. With the backdrop of the two COVID-19 waves that broke out in Delhi, this study examines the variations in the concentrations of criteria pollutants, air quality, and meteorological variables across the waves and their influence on COVID-19 morbidity/mortality. Descriptive statistics, violin plots, and Spearman rank correlation tests were employed to assess the variations in environmental parameters and investigate their associations with COVID-19 incidence under the two waves. The susceptible-infected-recovered model and multiple linear regression were used to assess the wave-wise basic reproduction number (R0) and infection spreading trajectory of the virus. Our results show that the first wave in Delhi had three successive peaks and valleys, and the first peak of the second wave was the tallest, indicating the severity of per-day infection cases. During the analysed period (April 2020 and April 2021), concentrations of criteria pollutants varied across the waves, and air pollution was substantially higher during the second wave. In addition, the results revealed that during the second wave, NO2 maintained a significant negative relationship with COVID-19 (cases per day), while SO2 had a negative relationship with COVID-19 (cumulative cases) during the first wave. Our results also show a significant positive association of O3 with COVID-19 deaths during the first wave and cumulative cases and deaths during the second wave. The study indicates that a higher relative humidity in Delhi had a negative relation with COVID-19 cumulative cases and mortality during the first wave. The study confirms that the estimated R0 was marginally different during the two waves, and the spread of COVID-19 new cases followed a cubic growth trajectory. The findings of this study provide valuable information for policymakers in handling COVID-19 waves in various cities.
Highlights
Countries worldwide are facing the resurgence of COVID-19 disease caused by the severe acute respiratory syndrome coronavirus 2 (SARSCOV-2) in the form of different waves at different points in time and with varying levels of virulence (Iftimie et al, 2021; Soriano et al, 2021; Jassat et al, 2021)
The first COVID-19 wave began in Delhi on 4 March 2020, when the first COVID-19 case was detected in the city
The number of SARS-CoV-2 infection cases increased rapidly, and the first peak of the first COVID-19 wave in the city was reached on 23 June 2020, with 3947
Summary
Countries worldwide are facing the resurgence of COVID-19 disease caused by the severe acute respiratory syndrome coronavirus 2 (SARSCOV-2) in the form of different waves at different points in time and with varying levels of virulence (Iftimie et al, 2021; Soriano et al, 2021; Jassat et al, 2021). Jalali et al (2020) reported lower disease mortality during the second wave than the first wave in Iran, which struck during the relatively warm months (February–May). Lockdown measures brought a significant reduction in air pollution across different cities worldwide (Rume and Didar-Ul Islam, 2020; Gautam, 2020; Zambrano-Monserrate et al, 2020; Venter et al, 2020; Liu et al, 2021). Kumari and Toshniwal (2020) reported reductions in PM2.5, PM10, and NO2 concentrations by 20–34%, 24–47%, and 32–64%, respectively, in 12 major world cities due to lockdown measures. Fu et al (2020) noted similar findings for PM2.5, PM10, NO2, SO2, and CO concentrations in 20 major world cities due to the lockdown effect. Rathod et al (2021) found reductions in three crucial air pollutants, namely, NO2, CO, and volatile organic compounds (VOCs), in Delhi by 50%, 37%, and 38%, respectively, during the
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