When the sun’s UV rays come in contact with CFCs, the chlorine atoms come loose. These chlorine atoms wander around the atmosphere until they meet up with ozone molecules. The chlorine atom and one of the oxygen atoms of ozone combine, leaving behind diatomic, or molecular, oxygen. When a free oxygen atom contacts this chlorine-oxygen compound, the two oxygen atoms combine to form molecular oxygen, and the chlorine goes off to devastate more ozone molecules. Molecular oxygen, unlike ozone molecules, cannot keep UV rays from reaching the Earth's surface. The U.S. Environmental Protection Agency estimates that one atom of chlorine can destroy as many as 100,000 molecules of ozone. In 1974, M. J. Molina and F. S. Rowland published a paper outlining how CFCs broke down ozone molecules in the atmosphere.
