Certain changes take place when chemical reactions take place among other pollutants. These would be classified as photochemical pollutants. For example, when sunlight acts on nitrogen oxides and certain organic compounds, ozone is produced. Sulfuric acid is another common pollutant when sulfur dioxide combines with oxygen and when combined with water forms an irritating and corrosive acid. Photochemical pollutants can cause discoloration of the upper surface of leaves of many crops, trees, and shrubs. It can damage and fade textiles and cause deterioration of rubber. It also is an irritant to the lungs and irritates the eyes, nose, and throat.

Acid rain occurs when pollutant gases react in the atmosphere with water, oxygen, and other chemicals to form various acidic compounds. Sunlight increases the rate of most of these reactions. The result is a mild solution of acid like sulfuric acid and nitric acid.

Effects of acid rain