Ozone is an invisible gas composed of three atoms of oxygen.
Miles above the earth's surface, ozone forms naturally and shields us from cancer-causing ultraviolet rays. At ground level, however, the same substance is harmful. Ground-level ozone is an air pollutant that causes damage to the environment and poses a significant health risk for many people. Volatile organic compound emissions include automobile exhaust, chemical cleaners, paint, and gasoline vapors. The burning and combustion of gasoline, coal, diesel, and other fuels in automobile engines and industrial plants produce nitrogen oxide emissions.