In soil, fertilizers containing inorganic nitrogen and wastes containing organic nitrogen are first decomposed to give ammonia, which is then oxidized to nitrite and nitrate. The nitrate is taken up by plants during their growth and used in the synthesis of organic nitrogenous compounds. Surplus nitrate readily moves with groundwater (2, 3). Under aerobic conditions, it percolates in large quantities into the aquifer because of the small extent to which degradation or denitrification occurs. Under anaerobic conditions, nitrate may be denitrified or degraded almost completely to nitrogen. The presence of high or low water tables, the amount of rainwater, the presence of other organic material, and other physicochemical properties are also important in determining the fate of nitrate in soil ( 4). In surface water, nitrification and denitrification may also occur, depending on the temperature and pH. The uptake of nitrate by plants, however, is responsible for most of the nitrate reduction in surface water. Nitrogen compounds are formed in the air by lightning or discharged into it from industrial processes, motor vehicles, and intensive agriculture. Nitrate is present in air primarily as nitric acid and inorganic aerosols, as well as nitrate radicals and organic gases or aerosols. These are removed by wet and dry deposition.

WHO guidelines for drinking-water quality.

International programme on chemical safety

Publisher Summary This chapter discusses the role of glutathione (GSH) and glutathione s-transferases in metabolism of chemical carcinogens and other electrophilic agents. GSH is a tripeptide (I) that is present in nearly all living cells and is the most abundant sulfhydryl compound present in animal tissues, mainly in the cytosol. The chapter illustrates the wide range of electrophilic agents, including several known mutagens and carcinogens, which conjugate with GSH, a process usually catalyzed by the GSH S-transferases. This conjugation is probably a protective mechanism and is the initial stage in mercapturic acid biosynthesis for the elimination of foreign compounds from the body. GSH S-transferases provide protection not only by catalyzing the conjugation of a potential toxicant with GSH, but also by preferentially binding, even covalently, that toxicant. The reactive electrophiles that conjugate with GSH also bind to DNA, RNA, and protein and identification of GSH conjugates provide information on the nature of these biologically active intermediates or even their immediate precursors. Thus, the knowledge of the way in which mutagens and carcinogens are metabolized is essential to a better understanding of their mode of action and of the processes for their detoxication.

The role of glutathione and glutathione S-transferases in the metabolism of chemical carcinogens and other electrophilic agents.

Guidelines for Canadian Drinking Water Quality

s, 61: 4784 (1964). 5. MONIER-WILLIAMS, G. W. A/umimum in food. London, Ministry of Health, 1935 (Reports on Public Health and Medical Subjects). 6. SYLVESTER, R. 0. ET AL. Factors involved in the locatiOn and operation of an aluminium reduction plant. Proceedings of the 22nd Industrial Waste Conference. Lafayette, IN, Purdue University, 1967, pp. 441-454. 7. RIDGWAY, J. ET AL. Water quality changes-chemical and microbiological studies. In: Water distrzbution systems. Medmenham, England, Water Research Centre, 1979. 8. AINSWORTH, R. G. ET AL. Deposits, corrosion products and corrosion mechanisms in iron mains. In: Water distribution systems. Medmenham, England, Water Research Centre, 1979. 9. AINSWORTH, R. G. ET AL. The introduction of new water mto old distribution systems. Medmenham, England, Water Research Centre, 1980 (TR 146). 10. VozAR, L. Content of aluminium in the diet and its biological action. Voprosy pitanija, 21: 28 (1962). II. ZooK, E. G. & LEHMANN, J. Total diet study: content of ten minerals-aluminium, calcium, phosphorus, sodium, potassium, boron, copper, iron, manganese and magnesium. Journal of the AssociatiOn of Official Agricultural Chemists, 48: 850 (1965). 12. GABOVICH, R. D.

https://www.jstage.jst.go.jp/article/jhs1956/35/5/35_5_307/_pdf

Z. Radwan

Papers

Mutagenicity in vitro and potential carcinogenicity of chlorinated ethylenes as a function of metabolic oxirane formation