Nitrogen oxides are produced in automobile engines and other devices where combustion takes place. Chemical reactions between nitrogen oxides and hydrocarbon pollutants in sunlight produce ozone, a major constituent of an irritating mixture of pollutants and fog known as smog. Nitrogen oxides are cause acid rain.
Chlorofluorocarbons (CFC's) are chemically stable synthetic substances that have had a variety of industrial uses. Some scientists believe that CFC can contribute to a “greenhouse effect” because Chlorofluorocarbons (CFC's) are destroying ozone that absorbs potentially harmful ultraviolet radiation from the sun.