Methylmercurials

Microbial processes can also detoxify mercury ions and organic compounds by reducing the mercury to the elemental form, which is volatile (86). This certainly reduces the environmental impact of compounds such as methylmercury, however, such a bioprocess would have to include a mercury capture system before it could be exploited on a large scale with pubHc support. 

Alkyl mercury compounds in the blood stream are found mainly in the blood cehs, and only to a smah extent in the plasma. This is probably the result of the greater stabhity of the alkyl mercuric compounds, as well as their pecuflar solubiUty characteristics. Alkyl mercury compounds affect the central nervous system and accumulate in the brain (17,18). Elimination of alkyl mercury compounds from the body is somewhat slower than that of inorganic mercury compounds and the aryl and alkoxy mercurials. Methylmercury is eliminated from humans at a rate indicating a half-life of 50—60 d (19) inorganic mercurials leave the body according to a half-life pattern of 30—60 d (20). Elimination rates are dependent not only on the nature of the compound but also on the dosage, method of intake, and the rate of intake (21,22). 

Metals and metalloids that form alkyl compounds, eg, methylmercury and methylarsenic acid, tributjltin, deserve special concern because these compounds are volatile and accumulate in cells they are poisonous to the central nervous system of higher organisms. Because methylmercury or other metal alkyls may be produced at a rate faster than it is degraded by other organisms, it may accumulate in higher organisms such as fish. Hg species are also reduced to elementary Hg which is soluble in water but lost by volatilization to the atmosphere (40). 

The methylmercury(I)-imidazole system in solution contains [MeHg(Him)], [MeHg(im)] and [(McHgl Im] species (77JA8106). In the latter the imidazo-late ligand fulfils a bridging function and is coordinated via both nitrogen heteroatoms. 

Mercury phthalocyanine (PcHg) is prepared by lithium-metal exchange between Li2Pc and mercury(II) chloride.59 A different kind of phthalocyanine, bis(methylmercury) phthalocyanine [Pc(HgX)2], can be obtained by the reaction of phthalocyanine and methylmercury bis(trimethylsilyl)azide in benzene293 or by heating phthalocyanine with methylmercury(II)... 

Source Data from Environmental Health Criteria 101 Methylmercury. 

Craig, PJ. (Eid.) (1986). Organometallic Compounds in the Environment—collection of detailed chapters on the environmental chemistry and hiochemistry of organometallic compounds. Environmental Health Criteria 18 Arsenic Environmental Health Criteria 85 Lead Environmental Aspects Environmental Health Criteria 86 Mercury, Environmental Aspects Environmental Health Criteria 101 Methylmercury Environmental Health Criteria 116 Tributyltin... 

Behavioral effects of OP insecticides have also been shown in birds (see review by Grue et al. 1991). Behavioral effects of OCs, OPs, and methylmercury on birds have been reviewed by Peakall (1985,1996). A remarkably wide range of behavioral tests were used in these studies. Tests employed included the following ... 

Heinz, G.H. and Hoffman, D.J. (1998). Methylmercury chloride and selenomethione interactions on health and reproduction in mallards Environmental Toxicology and Chemistry 17, 139-145. 

Kenow, K.P., Grasman, K.A., and Hines, R.K. et al. (2007). Effects of methylmercury exposure on the immune function of common loons. Environmental Toxicology and Chemistry 26, 1460-1469. 

O Connor, D.J. and Nielsen, S.W. (1981). Environmental survey of methylmercury levels in wild mink and otter from the North Eastern USA and experimental pathology of meth-ylmercurialism in the otter. Proceedings, Worldwide Furbearer Conference, Frostburg, MD, USA August 3-11 1981 1728-1745. 

The in vivo formation of toxic methylmercury compounds probably involves methylation by methylcorrinoids [see Section VII,D and Chapter 17 of ref. 136)1... 

Besides thermolysis, the photochemical decomposition of solid trihalo-methylmercury compounds RHgCCli, CF3HgOCOCF3 and Hg(OCOCF3)2 has been studied (Scheme 2). The irradiation of samples placed in an evacuated quartz tube, which was connected to a helium cryostat, was carried out at -50 to +10°C. Thus, a desorption into the gas phase of the primary products of the photolysis occurred, and consequent low-temperature matrix stabilization of them was made. As a result, the formation of only the radicals CCI3 (1 3 898 cm" ) and CF3 (vi 1084, V2 702, P2+ V4 1205, r>3 1249 cm ) or of products of their secondary reactions was observed (Mal tsev et al., 1974, 1975, 1977b). 

In Hg-resistant bacteria that are resistant to organic forms of Hg such as phenylmercuric acetate and methylmercury chloride, lyases are involved in the fission of the C-Hg to form Hg + and benzene or methane, and the enzyme has been partly purified (Schottel 1978). The Hg + may then be reduced to nontoxic Hg°. The situation under anaerobic conditions for sulfate-reducing bacteria is complicated by the possibility of both methylation and demethylation in the same strain (Pak and Bartha 1998), plausibly by operation of the acetyl-CoA pathway (Choi et al. 1994 Ekstrom et al. 2003). Under anaerobic conditions, demethylation, though not methylation, has been reported for a methanogen (Pak and Bartha 1998). 

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