THis and oxides of nitrogen give the air above L.A. its red-brown color. All of these chemicals are very irritating and reactive so that they oxidize materials as well as lungs. A temperature inversion is an instance in which cold air is covered by warmer air. These have occured in Donora Penna. and London. The stratosphere is 12-50 km above the earth's surface.
Air is thin, but radiation is intense causing molecules to break apart and free radical formation.
Ozone is normally in concentrations of a few ppm in the atmosphere. It is measured by the amount of radiation that gets through to the earth. It has been measured since about 1880. There is also now a slight seasonal decrease in ozone in the northern hemisphere. These are used as solvents, refrigerants, foam blowing agents, etc.