CFCs have been drifting up slowly into the stratosphere, 10 miles or more above the earth's surface, since these synthetic gases were first produced in the early 1930's. Chlorofluorocarbons, (CFCs) are chemically very stable, that is, they do not readily combine or break down when exposed to other chemicals. Industry quickly utilized the stable, inert properties of these chemicals for refrigeration, spray cans, plastic foam packaging, fire extinguishers, and electronic solvents. Inert properties make CFCs non-toxic and non- combustible - there are no natural chemicals in the earth's lower atmosphere that will combine with CFCs. Production of CFCs grew each year, with the chemical industry unconcerned as to where the millions of tons of synthetic substances would ultimately end up.
Most CFC gases take an average of 50 to 100 years to reach the upper stratosphere where high-energy ultraviolet (UV) radiation is strong enough to break the CFC molecules apart. At this point each CFC-12 molecule releases two chlorine (Cl) atoms, while CFC- 113 will release three. As early as 1974, chemists Sherry Rowland and Mario Molina, University of California at Irvine, determined these free chlorine atoms would serve as catalysis in a reaction that would destroy stratospheric ozone (O3). The reaction is basically a two-step process where the chlorine breaks down ozone molecules to form ordinary oxygen, O2. The chlorine atom itself is not consumed in the reaction, but does appear in the form of chlorine monoxide (ClO) during one step in the process.
Many scientists warned government and industry that since the ozone layer is so thin, the large amounts of CFCs would have serious consequences for the stratospheric ozone. A single CFC molecule destroys many O3 molecules, due to the catalytic power of the free chlorine. The very thin ozone layer is Earth's primary shield against powerful, damaging ultraviolet radiation. ***
