If you live in an urban area, and are breathing easier of late, it may be because levels of nitrogen dioxide emitted largely from vehicle exhausts are down 45-50% when compared with the same period last year. The data confirming this reduction in air pollution come from the European Space Agency’s Copernicus Sentinel-5P Earth observation satellite.
Nitrogen dioxide levels over France in 2019 and 2020 respectively. (© ESA)
Nitrogen dioxide in the atmosphere is produced when fossil fuels are burned, and much of it comes from the catalytic converters fitted to diesel engines. The gas creates the brown haze seen on the horizon mainly in urban environments, and is responsible for many deaths due to respiratory illness. The EU sets legal limits on the amount of NO2 in the atmosphere, but the level is often exceeded in areas with high traffic volumes.
Researchers analysing the Copernicus data have observed a large variability in NO2 levels due to changing weather conditions, but the measurements display a clear correlation with low traffic volumes following the coronavirus lockdown.