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Nitrate in surface & ground water originates from the atmosphere, natural sources, sewage and industrial effluents; but the main source causing recent concern is from agriculture. Levels of nitrate in drinking water are increasing as a result of changes in land use and artificial nitrogenous fertilizers. The importance of nitrates in the environment is mainly because of two reasons, Firstly, nitrates when consumed by infants in large amount during first six months of their life, result in a disease called 'BLUE BABY' of 'METHAEMOGLOBINEMIA' which is a form of CYANOSIS. Scragg at al (1982), observed a doubling of the risk of congenial malformation mainly neural tube defects when water containing 1.1-3 3 mg/1 nitrate was consumed during pregnancy and a threefold increase when water containing 3.3 mg/1 nitrate was consumed. Secondly, under certain conditions nitrate reacts chemically with a a wide range of secondry and tertiary amines and amides leading to the formation of N notroso compounds known as NITROSAMINES. These nitrosamines produce potentially carcinogenic, teratogenic and mutagenic effects.

Several suggestive epidemiological

correlations have been found, in 1979 the UK Royal Commission on Environmental Pollution and Fraser et al (1980) examined the result of the studies relating gas. tric cancer risk to nitrate fertilizer used in Chile, water borne nitrate level in Columbia and the Nottinghamshire town of Worcester in UK, and concluded no evidence unambiguously associated nitrates or N-nitroso compounds with cancer in any organ in man. However, the N-nitroso conjugated acids are potent mutagens for bacteria and human cells in culture and potent carcinogen when give orally to rats.

Nitrates generally reach water from the following routes;

1. Inorganic nitrogenous fertilizers are of late extensively used in agriculture. Large quantities of these are washed away resulting in contamination of water

sources.

2. The Industrial wastes, particularly from factories manufacturing nitrogenous fertilizers, processed foods, daily and meat products, contain large quantities of nitrates and many a times nitrites also.

3. The recent trend of confining large number of catties, pigs & poultry in a limited area, has created a new pointsource ofnitrates.

4. Good secondry treatment of sewage and organic wastes produce considerable amount of nitrates and some nitrites.

5. Refuse dumps release nitrate which may seep into ground water or contaminate surface water over prolonged period.

6. Seepage and run off from septic tanks, cesspools.

7. Decomposition of decaying organic matter buried underground,

In India there is extensive use of fertilizers. Synthetic nitrogenous fertilizers like Ammonium sulfate, Amm. nitrate, Urea, Amm. chloride, Calcium Ammonium nitrate, Nitrophosphates, Amm. Phosphates, Di Amm. phosphate, etc. are the most important nitrogenous fertilizers being used in our country, as sources of nitrogen. The use of nitrogen fertilizers has grown in India over the last decade is evident as below;

Year 1969-70 1.358 million tonnes
Year 1979-80 3.498
Year 1989-90 9.853

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As we have seen above that since 1969 70 the increase in use of fertilizers escalated about nine folds in 1689.90,