Lockdowns meant to battle the coronavirus has decreased air pollution in urban areas across Europe.
According to Reuters, new satellite images showed reductions in average levels of noxious nitrogen dioxide over March 5-25, 2020.
Cities showing such changes include Brussels, Paris, Madrid, Milan and Frankfurt.
Many European countries have curbed road transport – the largest source of nitrogen oxides - and slowed output at gas-emitting factories.
The European Public Health Alliance said people living in polluted cities may be more at risk from COVID-19.
That's because prolonged exposure to bad air can weaken the immune system, making it harder to fight infection.