Chemists Mario Molina (above left) and Sherwood Rowland, shown in 1976, calculated that CFCs used in aerosols, refrigeration, and air conditioning were destroying the ozone layer. Credit: Associated Press

Until the early 1970s, it could be said that, like politics, all chemistry was local. That changed in dramatic fashion with a series of discoveries concerning the global effects of a family of chemicals called chlorofluorocarbons, or CFCs. These compounds had played a key role in the midcentury chemical revolution, allowing such innovations as safe refrigeration, cheap aerosol deodorants, and widespread air conditioning. First commercialized by ­DuPont in the early 1930s under the trade name Freon, CFCs appeared to be the perfect industrial chemical: nontoxic, nonflam­mable, and odorless. But in 1973, a pair of chemists at the University of California, Irvine--Sherwood Rowland and his postdoctoral fellow Mario Molina--began to explore the fate of the CFC gases that were being emitted into the atmosphere. Molina began the investigation of CFCs in October of that year, and by Christmas, the researchers had their answer: the CFCs were breaking down in the atmospheric ozone layer, which begins 15 kilometers above the earth, ends roughly 30 kilometers later, and absorbs much of the sun's deadly ultraviolet radiation.

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