Which pollutant is most responsible for depletion of the ozone layer?
Chlorofluorocarbons are stable in the lower atmosphere and can persist long enough to reach the stratosphere. Ultraviolet radiation there photolyses them, releasing chlorine radicals. A chlorine radical catalytically converts ozone to molecular oxygen and is regenerated, allowing one atom to destroy many ozone molecules. This mechanism produced severe polar ozone depletion and motivated international controls under the Montreal Protocol. At organismal level, respiratory surfaces are especially exposed because large volumes of air contact thin, moist epithelia designed for rapid gas exchange. Sound classification links the source, atmospheric fate, exposure route, and mechanism of toxicity rather than relying only on the pollutant's name. Effective management combines cleaner fuels, emission standards, monitoring, urban planning, and protection of populations with high exposure or physiological vulnerability. The distinction is ecologically important because emission control must target either the directly released precursor or the product formed after atmospheric transport and reaction. Exposure depends on concentration, duration, ventilation, weather, and individual susceptibility, so a pollutant's presence alone does not fully predict biological harm.
Ref: Campbell Biology, Urry et al., 12th Ed., Unit 8 Ecology