Imagine a typical Hollywood "gotcha" film. The plot involves
the discovery that the apparent "bad guy" is in fact the "good
guy," and that the seemingly nice guy is in fact a fiendishly
evil genius. This is the case with ozone and
chlorofluorocarbons.
Ozone is a molecule consisting of three oxygen- atoms. Its
chemical notation is O3. Ozone is a "bad guy" in that breathing
it is lethal at dosage levels of a few molecules per million air
molecules. This is why ozone at the surface is referred to as a
pollutant. Yet ozone high in the atmosphere screens out
biologically harmful solar ultraviolet radiation, keeping it
from reaching the surface. Such ultraviolet radiation is
destructive of genetic cellular material in plants and animals,
as well as human beings. Without the "ozone layer" high up in
the atmosphere, life on the surface of the Earth would not be
possible as we know it.
