CFCs were first synthesized in the United States by a joint Du Pont-General Motors operation in 1930. The distinctive chemical properties of CFCs quickly found widespread use as coolants in air conditioners and refrigerators, solvents for cleaning circuit boards, and as a gas for putting the puff into insulating foams and packing materials. Within CFCs, the key ingredient that degrades ozone is thought to be chlorine. 3 Other industrial chemicals that can break down ozone include methyl chloroform and carbon tetrachloride. Some natural processes, including chlorine released from oceans, large volcanic eruptions such as Mount Pinatubo, and burning of trees, also destroy the ozone in the stratosphere.
Nature contributes about one fifth of the chlorine released into the atmosphere.
Thus, concern in the past decade has centered on the effects of the additional chlorine added to the atmosphere by human beings. The most widely accepted explanation for the shrinkage of the ozone layer arose from work in the early 1970s by Mario J. Molina, now at the Massachusetts Institute of Technology, and F. Sherwood Rowland of the University of California at Irvine. Molina and Rowland suggested that chlorine compounds from CFCs might live long enough in the atmosphere to destroy ozone. A 1975 National Oceanic and Atmospheric Administration investigation demonstrated that a small depletion of the ozone layer had occurred earlier in that decade. Following a governmental task force's recommendation in 1975, most companies stopped using CFCs in aerosol spray cans.