The problems of air pollution and acid rain in India are reviewed. Gaseous pollutants like SO2 and NO2 are high in a few large cities in India, whereas at other locations their concentrations are in the range of background levels. The concentrations of total suspended particulates in coastal Kerala and forest regions are within 100 mug m-3, but in north-west and central India they are quite high and vary between 200 and 550 mug m-3. The concentrations of soil-oriented components (Al, Fe, Mn, Ca, K and Mg). are higher in aerosols and the concentrations of components from anthropogenic sources (Pb, Ni, Cd, Zn, Cu, Sb, SO4 and NO3) are lower than those reported for western countries which are industrially more developed. There are more cations (Na, K, Ca and Mg) than anions (SO4 and NO3) in the aerosols reported from different environments. These aerosols, which are potentially basic in nature, influence the acidification of rain water. The mass size distribution of aerosols reveals that coarse particles (natural sources) dominate over the submicron particles (anthropogenic sources) in India. It is observed that precipitation in India is, by and large, alkaline. It is of interest to notice that rain water in Chembur, a highly industrialized area in Bombay region which was reported acidic from 1974 to 1980, turned alkaline in 1990. This could become possible due to proper pollution control measures taken by industries in the area. Acid rain, wherever it has occurred in India, is purely a local phenomenon and is restricted within 2 km distance in the upwind and downwind of the industrial complexes.
