Metal toxicity selenium

WhangerP. 1981. Selenium and heavy metal toxicity. Selenium Biol Med [Proc Int Symp] 2 230-255. 

Schrauzer, G.N., Effects of selenium antagonists on cancer susceptibility New aspects of chronic heavy metal toxicity, J UOEH 9, 208, 1987. 

Heavy metals stimulate or inhibit a wide variety of enzyme systems (16, 71, 72), sometimes for protracted periods (71, 73). These effects may be so sensitive as to precede overt toxicity as in the case of lead-induced inhibition of 8 ALA dehydrase activity with consequential interference of heme and porphyrin synthesis (15, 16). Urinary excretion of 8 ALA is also a sensitive indicator of lead absorption (74). Another erythrocytic enzyme, glucose-6-phosphatase, when present in abnormally low amounts, may increase susceptibility to lead intoxication (75), and for this reason, screens to detect such affected persons in lead-related injuries have been suggested (76). Biochemical bases for trace element toxicity have been described for the heavy metals (16), selenium (77), fluoride (78), and cobalt (79). Heavy metal metabolic injury, in addition to producing primary toxicity, can adversely alter drug detoxification mechanisms (80, 81), with possible secondary consequences for that portion of the population on medication. 

Heavy metal toxicity in plants is infrequent (143). In many cases, metal concentrations in plant parts show poor correlation with soil concentrations of the element (147). Plants tend to exclude certain elements and readily accept or concentrate others. Lisk (148) reported natural plant soil concentration ratios of 0.05 or less for As, Be, Cr, Ga, Hg, Ni, and V. Cadmium appears to be actively concentrated and selenium appears to be easily exchangeable. Indicator plants are capable of markedly concentrating specific elements, e.g., Astragalus spp. for selenium (138) and Hybanthus floribundus for nickel (149). Plants growing on mine wastes have been shown to evolve populations which exhibit metal-specific tolerances (150). 

Ganther HE, Wagner PA, Sunde ML, et al. 1973. Protective effects of selenium against heavy metal toxicities. Proc Univ MO Annu Conf Trace Subst Environ Health. 7 247-252. 

Whanger PD. 1976. Selenium versus metal toxicity in mammals. Proceedings of the Symposium on Selenium-Tellurium in the Environment 234-252. 

Stationary sources are the major contributors of most environmentally important metals in air. Flinn and Reimers (23) reported the annual airborne emissions of metals in the United States from stationary sources projected through 1983 based on production estimates and assuming no changes in processes or control technology. Their results, summarized in Table V, show projected increases in emissions from all environmentally important metals where data are available. Comparatively low concentrations (150-900 ton/year) of the highly toxic metals— berylhum, selenium, and mercury— were reported for the 1969-1971 period. Metals emitted in the highest concentrations are zinc (151,000 ton/year) and titanium (88,000 ton/year), although iron could be expected to exceed these levels. 

Examples showing that metal speciation is important to metal toxicity include arsenic, copper, selenium, and chromium. While ionic copper (Cu2+) and CuClj are highly toxic, Q1CO3 and Cu-EDTA have low toxicity (Morrison et al, 1989). Toxicity tests show that As(III) is about 50 times more toxic than As(VI). Trivalent chromium is much less toxic than hexavalent chromium, probably because Cr(VI) is much smaller and the chemical structure of chromate is similar to sulfate. A special channel already exists in biomembranes for sulfate transport. While modeling metal speciation is not always possible, and redox equilibrium is not achieved in all natural waters, geochemical modeling of equilibrium species distribution remains one of the methods of discerning metal speciation. 

NICKEL CYANIDE or NICKEL CYANIDE, SOLID or NICKEL(II) CYANIDE (557-19-7) Ni(CN), A thermally unstable solid. Violentreaction with fluorine, hypochlorites, nitric acid, nitrates, nitrites, magnesium + heat. Contact with acids or heat releases deadly hydrogen cyanide gas. Incompatible with sulfur, selenium, active metals, sulfur, selenium. Explosive reaction with chlorates, nitrates, and other materials in heat above 842°F/450°C. Thermal decomposition releases toxic cyanide fumes. On small fires, use dry chemical powder (such as Purple-K-Powder), foam, or COj extinguishers. 

ScHRAUZER GN (1987) Effects of interactions of lead, cadmium and other metals with selenium on the genesis and growth of malignant tumors a new aspect of chronic metal toxicity. J UEOH (Univ Occup Environ Health Jpn) 9 208 - 215. 

It may be noted that many toxic metals are also essential for the body, at trace levels. Their absence from the diet can produce various deficiency syndromes and adverse health effects. Such essential metals include selenium, copper, cobalt, zinc, and iron. On the other hand, excessive intake can produce serious adverse reactions. Also, a number of metals, such as aluminum, bismuth, lithium, gold, platinum, and thallium, have been used in medicine. Despite their beneficial effects, excessive intake of these metals and their salts can cause serious poisoning. 

Vitamin E and selenium have roles in the immune system and protect against heavy metal toxicity. Other mutual functions and effects of deficiency in farm animals are discussed in the section on vitamin E (see pp. 81-86). 

Various proposals have been presented to explain the interaction of selenium with heavy metals. However, no single one appears to explain the mechanism of interaction with all heavy metals. It appears that there are several mechanisms involved in this interaction and that more than one could be involved with a particular metal. It is clear that selenium does not protect animals against heavy metal toxicity by increasing their excretion instead, it causes an increased retention of metals (Parizek et al, 1971 Wagner et al., 1975 Diplock, 1976 Ganther, 1978 Whanger, 1981). A summary of the proposed interactions of selenium with cadmium, mercury, and silver is presented in Fig. 1. 

Whanger, P. D., 1976, Selenium versus metal toxicity in animals, in Proc. Symp. on Sele nium-Tellurium in the Environ., pp. 234-252, Industrial Health Foundation Inc., 5231 Centre Avenue, Pittsburgh, Pennsylvania. 

Whanger, P. D., 1981, Selenium and heavy metal toxicity, in Second International Symposium on Selenium in Biomedicine (J. Martin, ed.), Avi Press, Westport, Connecticut (in press). 

This chapter is an attempt to present the important results of studies of the synthesis, reactivity, and physicochemical properties of this series of compounds. The subject was surveyed by Bulka (3) in 1963 and by Klayman and Gunther (4) in 1973. Unlike the oxazoles and thiazoles. there are few convenient preparative routes to the selenazoles. Furthermore, the selenium intermediates are difficult to synthesize and are often extremely toxic selenoamides tend to decompose rapidly depositing metallic selenium. This inconvenience can be alleviated by choice of suitable reaction conditions. Finally, the use of selenium compounds in preparative reactions is often complicated by the fragility of the cycle and the deposition of metallic selenium. 

The most common toxic metals in industrial use are cadmium, chromium, lead, silver, and mercury less commonly used are arsenic, selenium (both metalloids), and barium. Cadmium, a metal commonly used in alloys and myriads of other industrial uses, is fairly mobile in the environment and is responsible for many maladies including renal failure and a degenerative bone disease called "ITA ITA" disease. Chromium, most often found in plating wastes, is also environmentally mobile and is most toxic in the Cr valence state. Lead has been historically used as a component of an antiknock compound in gasoline and, along with chromium (as lead chromate), in paint and pigments. 

About 100 gal of process wastewater is typically generated from 1 t of coke produced.15 These wastewaters from byproduct coke making contain high levels of oil and grease, ammonia nitrogen, sulfides, cyanides, thiocyanates, phenols, benzenes, toluene, xylene, other aromatic volatile components, and polynuclear aromatic compounds. They may also contain toxic metals such as antimony, arsenic, selenium, and zinc. Water-to-air transfer of pollutants may take place due to the escape of volatile pollutants from open equalization and storage tanks and other wastewater treatment systems in the plant. 

Coprecipitation is a partitioning process whereby toxic heavy metals precipitate from the aqueous phase even if the equilibrium solubility has not been exceeded. This process occurs when heavy metals are incorporated into the structure of silicon, aluminum, and iron oxides when these latter compounds precipitate out of solution. Iron hydroxide collects more toxic heavy metals (chromium, nickel, arsenic, selenium, cadmium, and thorium) during precipitation than aluminum hydroxide.38 Coprecipitation is considered to effectively remove trace amounts of lead and chromium from solution in injected wastes at New Johnsonville, Tennessee.39 Coprecipitation with carbonate minerals may be an important mechanism for dealing with cobalt, lead, zinc, and cadmium. 

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