Satellite data map of the average nitrogen dioxide (NO2) levels in France between 14th and 25th March 2020 (right), during the 2019-20 Covid-19 outbreak, compared to the the monthly average of concentrations from 2019 (left). Nitrogen dioxide is a pollutant gas produced during industrial fossil fuel combustion and by road traffic. Quarantines to stop the spread of the new coronavirus, SARS-Cov-2, that is the cause of Covid-19 have lead to a reduction in NO2 emissions from both industry and traffic. Data obtained by the Tropospheric Monitoring Instrument (TROPOMI) on ESA's Sentinel-5 satellite.