PROTECTING THE OZONE

Chlorofluorocarbons (CFCs) are ideal compounds for refrigerators and air conditioners because they are nontoxic and noncorrosive. However, the chemical inertness of these substances, once thought to be their major virtue, turns out to be their fatal flaw. When these compounds leak into the atmosphere, as they inevitably do, they are so unreactive they persist there for decades. Eventually these CFCs reach altitudes where ultraviolet light causes them to decompose, producing chlorine atoms that promote the destruction of the ozone in the stratosphere (see discussion above). Because of this problem, the world’s industrialized nations have signed an agreement (called the Montreal Protocol) that banned CFCs in 1996 (with a 10-year grace period for developing nations). So we must find substitutes for the CFCs—and fast.

In fact, the search for substitutes is now well under way. Worldwide production of CFCs has already decreased to half of the 1986 level of 1.13 million metric tons. One strategy for replacing the CFCs has been to switch to similar compounds that contain carbon and hydrogen atoms substituted for chlorine. atoms. For example, the United States appliance industry has switched from Freon-12 (CF₂Cl₂) to the compound CH₂FCH₃ (called HFC-134a) for home refrigerators, and most of the new cars and trucks sold in the United States have air conditioners that employ HFC-134a. Converting the 140 million autos currently on the road in the United States that use CF₂Cl₂ will pose a major headache, but experience suggests that replacement of Freon-12 with HFC- 134a is less expensive than was originally feared.

The chemical industry has responded amazingly fast to the ozone depletion emergency. It is encouraging that we can act rapidly when an environmental crisis occurs. Now we need to get better at keeping the environment at a higher priority as we plan for the future.

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