Deficiency effects arsenic

This chapter has outlined the main effects of arsenic and selenium on human and animal health, their abundance and distribution in the environment, sampling and analysis, and the main factors controlling speciation and cycling. Such information should help to identify aquifers, water resources and soils at risk from high concentrations of arsenic and selenium, and areas of selenium deficiency. Human activity has had, and is likely to continue to have, a major role in releasing arsenic and selenium from the geosphere and in perturbing the namral distribution of these and other elements over the Earth s surface. 

In the transitional zones between deficient and sufficient supply, as well as between normal and toxic supply, adaptation reactions occur as described for copper in sheep (Wiener and Field 1970) and for manganese in goats and cattle (Anke et al. 1973). As a consequence, breeds of farm animals which adapted themselves to the local trace element offer came into being. Depending upon the species and the elements involved, there is a pharmacodynamic or therapeutic range between the optimum and toxic element offers of some elements. Well-known examples of the effect of inorganic components in the diet are arsenical compounds in the... 

Anke M, Krause U and Groppel B (1987a) The effect of arsenic deficiency on growth, reproduction, life expectancy and disease symptoms in animals. In Hemphill DD, ed. Trace Substances in Environment Health — 21. University of Missouri, USA, pp. 533-550. 

Some trace metals are classified as toxic. There is, perhaps, justification for this classification for such metals as arsenic, lead, and mercury. In addition, extended exposure of mammals to small amounts of cadmium, lead, selenium, antimony, and nickel carbonyl can shorten life or cause cancer, and lead, nickel, antimony, cadmium, and mercury in small amounts cause human health problems. However, all metals are toxic if ingested at sufficiently high levels. Frequently, the effects of a toxic metal are increased by nutritional deficiencies. ... 

Studies in experimental species demonstrate that methyl donor availability affects the methylation of iAs. In mice exposed to arsenite (As ), depletion of the intracellular pool of 5-adomet by treatment with periodate-oxidized adenosine (PAD), an inhibitor of 5-adomet synthesis (Hoffman 1980), results in reduced urinary excretion of DMA (Marafante and Vahter 1984). Marafante and Vahter (1986) showed that consumption of choline-deficient diet decreased the urinary excretion of DMA and increased tissue As retention in rabbits given 0.4mg arsenate (As )/kg i.v. The same effect of a diet deficient in choline, methionine, and protein was observed in rabbits after administration of 0.4mg As Vkg i.v. (Vahter and Marafante 1987). 

Marafante E, Vahter M (1986) The effect of dietary and chemically induced methyla-tion deficiency on the metabolism of arsenate in the rabbit. Acta Pharmacol Toxicol 59 [Suppl 7] 35-38... 

A number of other selenium proteins have been discovered in biological materials, but their function is not yet sufficiently known. For example, a selenium protein (17kDa) was found in rat sperm. It is interesting that high concentrations of selenium in male sexual organs are maintained in animals with selenium deficiency therefore, selenium compounds are likely to be important for reproductive function. Some anticarcinogenic effects are also attributed to this element. Selenium also reduces the toxic effects of arsenic, cadmium, mercury, thallium and tellurium. With arsenic, the mechanism of this protective effect is the formation of selenobis(S-glutathionyl)arsinium anion, which is formed in erythrocytes and excreted in bile (6-36). 

Systematic reviews Arsenic enters human food chain possibly by arsenic accumulations in edible plants and crops, from contaminated soils and irrigation water that further reach livestock meat, animal products like milk and egg [9 ]. However in regions like Latin America, despite its long history of arsenic contamination, are rather poorly reported for arsenic toxicity. A systematic review revealed that at least 4.5 million people in Latin America are chronically exposed to high arsenic levels (>50 ng/L) with increased risks of adverse health effects like internal and external cancers, reproductive toxicity and childhood cognitive deficient function [10 ]. 

Only following such a way, it is possible to establish the optimum traee metal level for the diet and the concentration boundary line between essentiality and non-essentiality. It is also true that the concept essential/non-essential is applicable to several metals, but other elements, i.e. lead, cadmium, mercury, arsenic, antimony, are toxic at very low concentration level of intake and there are not known deficiency symptoms showing also cumulative effects, and for this reason they are extremely harmful on health. 

Thus, in the modified Lewis (or Lux-Flood) concept, pure alkali halides represent the highest degree of basicity as the solvent composition changes from alkali halide-rich to alkali halide-deficient melts, the solvent becomes acidic. Acid-base properties of molten halides may be used to explain stabilization of unusually low (or high) oxidation states, the differences in stability of the same oxidation state in related melts, and the effects on coordination observed spectrally for certain metal ions. Or, restating the idea in other terms, the redox potentials depend on melt basicity. Thus, the systematic variation of melt composition is a useful technique in the arsenal of the molten salt electrochemist who is interested in the chemistry of solute species in molten salt solvents. In this respect, it is important to note that variation of temperature may be used to serve the same purpose for example, it has been shown that in neutral chloro-aluminates C1- decreases with temperature. 

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