Cities including Brussels, Paris, Madrid, Milan and Frankfurt showed a reduction in average levels of noxious nitrogen dioxide over March 5-25, compared with the same period last year, according to the Sentinel-5 satellite images.
That coincides with lockdowns in many European countries which have curbed road transport – the largest source of nitrogen oxides – and slowed output at gas-emitting factories.
The new images, released by the European Space Agency (ESA) and analyzed by the non-profit European Public Health Alliance (EPHA), show the changing density of nitrogen dioxide, which can cause respiratory problems and cancer, like heat maps.
Daily weather events can influence atmospheric pollution, so the satellite pictures took a 20-day average and excluded readings where cloud cover reduced the quality of the data.
Data from the European Environment Agency (EEA) showed a similar trend over March 16-22. In Madrid, average nitrogen dioxide levels decreased by 56% week-on-week after the Spanish government banned non-essential travel on March 14.