Global assessment of tropospheric and ground air pollutants and its correlation with COVID-19

Highlights

• Significant reductions observed in the global tropospheric and ground-level AP post-lockdown.

• Countries with the worst air pollution exhibit remarkable improvement in the air quality.

• Transient reduction in AP followed by restoration towards pre-lockdown levels.

• NO₂ and O₃ positively correlated with SARS-CoV-2 cases and mortalities.

Abstract

The declaration of COVID-19 pandemic by the WHO initiated a series of lockdowns globally that varied in stringency and duration; however, the spatiotemporal effects of these lockdowns on air quality remain understudied. This study evaluates the global impact of lockdowns on air pollutants using tropospheric and ground-level indicators over a five-month period. Moreover, the relationship between air pollution and COVID-19 cases and mortalities was examined. Changes in the global tropospheric (NO₂, aerosols, and O₃) and ground-level (PM_2.5, PM₁₀, NO₂, and O₃) pollutants were observed, and the maximum air quality improvement was observed immediately after lockdown. Except for a few countries, a decline in air pollutants correlated with a reduction in Land Surface Temperature (LST). Notably, regions with higher tropospheric NO₂ and aerosol concentrations were also COVID-19 hotspots. Our analysis showed moderate positive correlation for NO₂ with COVID-19 cases (R² = 0.33; r = 0.57, P = 0.006) and mortalities (R² = 0.40; r = 0.63, P = 0.015), while O₃ showed a weak-moderate positive correlation with COVID-19 cases (R² = 0.22; r = 0.47, P = 0.003) and mortalities (R² = 0.12; r = 0.35, P = 0.012). However, PM_2.5, and PM₁₀ showed no significant correlation with either COVID-19 cases or mortality. This study reveals that humans living under adverse air pollution conditions are at higher risk of COVID-19 infection and mortality.