CLASSIFICATION OF AIR-POLLUTANTS The air pollutants may be classified in different ways as follows:- a) According to origin:- 1) Primary pollutants which are directly emitted in to the atmosphere and are found as such, e.g., CO, NO² So4, and hydrocarbons. 2) Secondary pollutants whicir are derived from the primary pollutants due to chemical or photo-chemical reactions in the atmosphere, e.g., Ozone, Peroxy-acyl nitrate (PAN), Photo-chemical smog, etc. Biochemical Effects Of Some Important Air Pollutants 1) Oxide of Sulphur (SOx) SOx comprises of SO² and So³ They are Colourless, heavy water soluble with pungent and irritating odour. SOx pollution is due to volcanic activity, combustion of fuels, Coal fired stations, transportation, Refineries, metallurgical operations, chemical plants and other naturai and human activitiesAn atmosphere oxidation of SO² in to SO³ by photolytic and Catalytic processes in presence of 0³, NOx, or hydrocarbons) giving rise to the fo...