Chloroflourocarbons(CFC) are the ”big dog” as far as causes of ozone depletion are concerned. CFC’s are man made chemicals that are very stable in the atmosphere. They take from 20 to 120 years to break down. All the while they are destroying ozone molecules. This is what happens: CFCs do not fall back to Earth with rain, nor are they destroyed by other chemicals. Because of their relative stability, CFCs rise into the stratosphere where they are eventually broken down by ultraviolet (UV) rays from the Sun. This causes them to release free chlorine. The chlorine reacts with oxygen which leads to the chemical process of destroying ozone molecules. The net result is that two molecules of ozone are replaced by three of molecular oxygen leaving. The chlorine then reacts again with the oxygen molecules to destroy the ozone and the process repeats 100,000 times per molecule. While naturally occurring chlorine has the same effect on the ozone layer, it has a shorter life span in the atmosphere.
