These industrial chemicals all share two characteristics they are very stable at ground level, and they contain chlorine or bromine.
Chlorine atoms have a voracious appetite for ozone.
A single chlorine atom is capable of destroying thousands of molecules of ozone, and bromine is even more destructive. Ozone depletion over Canada Since the late 1970's, industrial chemicals have caused a thinning of about 6 per cent in the ozone layer over southern Canada.