2 column measurements from the ESA SENTINEL-5 satellite ( 40) from 1 May 2018 to 17 June 2020. The satellite-based dataset allows us to include countries where ground monitor data are not available and provides a second set of results in regions where ground monitor data are available. Surface-level NO 2 concentrations are estimated from column measurements using two different methods for robustness (see Materials and Methods). This dataset of air quality measurements is combined with population density data provided by the Center for International Earth Science Information Network ( 41) to quantify population-weighted average exposure in each region before and during the lockdown restrictions. These air quality measurements are combined with the indicator of the stringency of lockdown measures developed by Hale