Pollution is a negative effect of industrialisation. It adversely affects the environment and degrades it. Air pollution is caused by the presence of high proportion of undesirable gases, such as sulphur dioxide and cabon monoxide, dust sprays, mist and smoke in the atmosphere due to emission from industrial units. Smoke is emitted by chemical and paper factories, brick kilns, refineries and smelting plants and burning of fossil fuels in big and small factories that ignore pollution norms. These cause respiratory diseases among the people working or living in such areas. Toxic gas leaks as during the Bhopal Gas Tragedy can be hazardous with long-term ill effects. Water pollution is caused by organic and inorganic industrial wastes and effluent discharged into rivers. The main culprits in this regard are paper, pulp, chemical textile and dyeing, petroleum refineries, tanneries and electroplating industries. These let out dyes, detergents, acids, salts and heavy metals like lead and mercury, pesticides, fertilisers, synthetic chemicals with carbon, plastics and rubber, etc., into water bodies. They turn big and small rivers into toxic streams. Iron and steel slags are dumped into water bodies, especially rivers, destroying aquatic life and making the water unfit for use. The pollution of the Ganga and the Yamuna are examples of water pollution caused by industries. Thermal pollution of water occurs when hot water from factories and thermal plants are drained into rivers or other water bodies.