In the 1980s laws were passed to reduce the amount of certain chemicals used by companies and individuals. According to these laws, the use of chlorofluorocarbons, or CFCs, should be reduced and eventually eliminated. These compounds contain chlorine and cause problems when released into the Earth’s atmosphere.

CFCs release chlorine-containing compounds into the atmosphere. Chlorine reacts with and breaks down ozone molecules in the stratosphere, thinning the ozone layer. Therefore, the correct choice is ozone layer depletion; the other choices describe different environmental problems.

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