Photochemical Smog:
Photochemical smog, a secondary Pollutant, results when the two pollutants, nitrogen oxide and hydrocarbons found in automobile exhausts, react with one another in the presence of sunlight to produce nitrogen dioxide (N02), ozone (03) and a compound called PAN (Peroxylacetyl nitrate), which then appear as a yellowish brown haze. Breathing ozone affects the respiratory and nervous system. It causes respiratory distress, affects eye membranes and stimulates tears. It also causes headache. Ozone also damages rubber articles, textiles and discolours paintings. It has been recently found that smog is harmful to timber. PAN is especially damaging to plants. Plants exposed to PAN exhibit leaf mottling and