COVID-19 lockdowns cause global air pollution declines with implications for public health risk

Zander S Venter; Kristin Aunan; Sourangsu Chowdhury; Jos Lelieveld

as the difference between observed and expected pollutant concentrations given weather during 152 lockdown. 153 154 We found a net decline of about 20% (5% to 35% -95% confidence interval) across all three 155 pollutants in countries where significant anomalies were detected. There were significant declines 156 in NO2 (29 %; 13% to 44%) and O3 (11%; 2% to 20%), however our model estimates were not 157 able to control for the confounding effects of weather enough to detect significant declines in PM2.5 158 (9% decline; -10 to 28%; Fig. S5 ). Indeed, our meteorological-control models were able to explain 159 less of the variance in PM2.5 (R 2 = 0.45) compared to NO2 (R 2 = 0.54) and O3 (R 2 = 0.72; Table 160 S1). This suggests PM2.5 has a weaker coupling to land-transportation and small business activity 161 declines during lockdown compared to NO2 and O3. In Many countries PM2.5 is more strongly 162 linked to residential energy use, power generation and agriculture (7). In addition, PM2.5 is 163 significantly influenced by long-distance atmospheric transport of mineral dust and therefore the 164 local effects of economic activity may be diluted or even overwhelmed (15). 165 166