The beginning of the CFC(chlorofluorocarbons) era started in 1928, when CFC' were invented by a Du Pont chemist. CFC' were best known as "freons" and became famous as a safe, nonflammable refrigerant. It's invention became a great triumph when Freon took the place of sulfur dioxide or ammonia which was used as the working liquid in refrigerators. It eventually became widely used in automobile air conditioners and nontoxic propellants in aerosol cans. It's insulating properties also was used for blowing agents for plastics and foam cups.
Thus CFCs became used all over the world and its business got bigger and bigger until late in 1973. Sherwood Rowland and Mario Molina, two distinguished chemists, came up with a surprising result in his calculations concerning the CFCs and ozone layer. CFCs are basically inactive in the troposphere(around the altitude of 50,000 feet) so it would gradually drift upward until they reached the mid-stratosphere.(about 100,000 feet) At this point CFCs would be broken down by short-wavelength ultraviolet radiation from the sun. This radiation is the one which would not reach the lower atmosphere in large amounts because of the ozone layer. When these CFCs do brake down, they released atomic chlorine which then would react with the ozone and convert it back into plain oxygen. The even worse part of all this is that these chlorine molecules do not become inactive after the first reaction with the ozone and would be available to destroy more ozone molecules. Thus this process would be the function of a catalyst; a single chlorine atom involved in a chain reaction to destroy many ozone molecules.
Rowland and Molina eventually agreed that this thinning of the ozone shield can cause a catastrophe for Earth's living beings, including humans, by allowing large amounts of the deadly ultraviolet-B radiation to reach to Earth's surface. Rowland and Molina checked their calculations again and again to make sure that these figures had not a single mistake in it because this conclusion was likely to destroy an $8 billion industry already in the United States. However, the lives of the living beings were far more important than businesses so in 1974 Rowland and Molina, having their calculations checked by their colleagues, explained their theory in a paper in the eminent scientific journal Nature. Later the only reasonable conclusion they drew out was that the use of CFCs be banned.
When these calculations were released to the public, Du Pont, the major CFC manufacturer, did everything they can to convince the people that the calculations were unproven and theoretical.