A. moved to reduce surface ozone, a form of pollution caused, in part, by emissions from oil refineries.

NEWYORKER: Covert Operations

While the ozone layer in the upper atmosphere plays an important role in limiting harmful ultraviolet light reaching the Earth's surface, low-level ozone is a pollutant that is harmful, causing respiratory problems in animals as well as well-documented cases in humans.

BBC: Invasive plant 'increases ozone pollution'

But the increased ultra-violet (UV) solar radiation which the damaged ozone allows through to the surface of the earth is a threat to all living things.

BBC: By Environment Correspondent Alex Kirby

And it's believed that the high chemical reactivity of the surface is due to the deposition of chemically active gases from the atmosphere onto the surface, gases like hydrogen peroxide and ozone.

NPR: Revisiting the Viking Missions to Mars

The ozone layer protects living things on the Earth's surface from the Sun's ultra-violet radiation.

BBC: Ill wind 'killed dinosaurs'