Selenium mercury exposure

Selenium lessens the toxicity of divalent mercury in animals, the protection being less at continuous mercury exposure. Selenium has been found to affect the distribution of mercuric mercury in mice [134], rats [135], rabbits [136, 137] and pigs [ 138]. Mercury forms a mercury-selenium protein complex with selenium with little biological activity [139]. Mercury is thus retained longer in the blood, liver and spleen and as a consequence lessens accumulation in the kidney. In fish, selenium pretreatment probably retarded mercury uptake rather than promoting mercury excretion [140]. 

N-acetyl-p-D-glucosaminidase (Figure 4). No significant correlation was evident for other renal parameters U-albumin, U-orosomucoid, U-p2-microglobulin, U-copper, S-creatinine, and S-p2-microglobulin. Studies on chlor-alkali workers in Scandinavia [122-124] have reported minimal and apparently reversible renal effects from mercury exposures in this occupational group as evaluated by urinary excrebon of NAG, albumin and titers of autoantibodies. These investigators noted that a small number of susceptible individuals may exist and that selenium status appears to have a major effect on urinary NAG excretion [124]. 

P. Other studies have shoivn that, at least in the case of greater mercury exposure, the molar ratio of mercury and selenium in human tissues is approximately 1 1 (Drasch et al. 2000). 

Krishnaja, A.P. and M.S. Rege. 1982. Induction of chromosomal aberrations in fish Boleophthalmus dussumieri after exposure in vivo to mitomycin C and heavy metals mercury, selenium and chromium. Mutat. Res. 102 71-82. 

The selection of the correct dissolution step in coal decomposition is vital in determining trace elements. Such elements as copper and nickel can easily be picked up as contaminants from the laboratory environment or reagents. Other elements such as mercury and selenium can be lost in the dissolution step. The dissolution procedure involving the least exposure to contamination without potential loss of volatile components should be used in for each trace element. 

Dibenzyl diselenide crystallises from alcohol in yellow needles, which are slightly deeper in colour than those of the p-nitrobenzyl compound, and melt at 92° to 93° C. Exposure to light for an hour or so causes the crystals to turn red. The selenide readily dissolves in hot alcohol, but is only sparingly soluble in ether, insoluble in water. Oxidation with fuming nitric acid converts it into benzyl seleninic acid, and boiling with copper or mercury in suspension precipitates selenium. Boiling with iodine in chloroform solution gives the tetra-iodide, M.pt. 98° C. the tetrabromide melts at 137° C.5... 

YSART G E, MILLER P F, CREWS H, ROBB P, BAXTER M, DE L ARGY C, lofthouse s, sargent c and Harrison N, 1997 UK total diet study -dietary exposures to aluminium, arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, tin and zinc, Food Additives and Contaminants, 2000 17 775-86. 

At least 11 metals are biologically toxic, as shown in Table I along with their threshold limit values (1,2,3) arsenic, beryllium, bismuth, cadmium, mercury, nickel, lead, antimony, selenium, tin, and vanadium. For these and other metals, the biological toxicity for long-term, low-level exposures is not known. Other metals such as manganese and iron are... 

Potential protective effect of selenium in fish. Selenium is known to bioconcentrate in fish, and selenium has been observed to correlate with mercury levels in the blood of fish consumed (Grandjean et al. 1992). Furthermore, there is evidence suggesting that consumption of methylmercury from fish, in conjunction with other beneficial constituents in fish (e.g., omega-3 fatty acids) may not result in the same toxicity dose-response relationship observed with methylmercury exposure from consumption of contaminated grain (as in the Iraqi population) (Davidson et al. 1998). 

Concerning interactions with other chemicals, there is an ongoing debate about the value of fish in the diet versus the risk from increased exposure to methylmercury that may be in the fish. One recent study reported a beneficial effect from increased fish consumption even though mercury body burdens were increased to some extent (Davidson et al. 1998). One possible factor in the fish that could improve health is omega 3-fatty acid. Children and adults both benefit from a healthy diet, but there may more emphasis on the benefits to growing children. Other interactions for mercury include the effect of various substances on its gastrointestinal absorption (e.g., iron, zinc) or possibly protective effects from prevention or repair of mercury related oxidative damage (e.g., interactions with selenium as an antioxidant). No information was identified that specifically addresses differences in these interactions for children compared to adults. 

Similarly, in most studies, the simultaneous administration of mercury and selenium in equimolar doses to animals has resulted in decreased toxicity of both elements in acute and chronic exposure studies. 

Bengt-Goran S, Nilsson A, Jonsson E, et al. 1995. Fish consumption and exposure to persistent organochlorine compounds, mercury, selenium and methylamines among Swedish fishermen. Scand J Work Environ Health 21(2) 96-105. 

Bjorkman L, Mottet K, Nylander M, et al. 1995. Selenium concentrations in brain after exposure to methylmercury Relations between the inorganic mercury fraction and selenium. Arch Toxicol 69 228-234. 

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