Nitric oxide, plays a major part in photochemical smog. Nitrous oxide stays in the troposphere for about 150 years and every molecule of NO2 is 230 times more effective than a carbon dioxide molecule in greenhouse warming. Nitrous oxide, is also one of the pollutants that depletes ozone in the stratosphere. Sulfur dioxide is produced by combustion of sulfur-containing fuels, such as coal and fuel oils. Also, in the process of producing sulfuric acid and in metallurgical process involving ores that contain sulfur.
Sulfur oxides can injure man, plants and materials.
At sufficiently high concentrations, sulfur dioxide irritates the upper respiratory tract of human beings because potential effect of sulfur dioxide is to make breathing more difficult by causing the finer air tubes of the lung to constrict. As emissions of sulfur dioxide and nitric oxide from stationary sources are transported long distances by winds, they form secondary pollutants such as nitrogen dioxide, nitric acid vapor, and droplets containing solutions of sulfuric acid, sulfate, and nitrate salts. These chemicals descend to the earth's surface in wet form as rain or snow and in dry form as a gases fog, dew, or solid particles. This is known as acid deposition or acid rain. Since 1978 the use of CFCs in aerosol cans has been banned in the United States, Canada, and most Scandinavian countries.