Seed dressings mercury

North America Feather From areas with mercury-treated seed dressing ... 

Mercury is consumed in the manufacture of organomercurials, which are used in agriculture as fungicides, e.g., for seed dressing. 

C.-G. Ros6n, H. Ackefors, and R. Nilsson, Seed Dressing Compounds Based on Organic Mercury—Economic Aspects and Health Hazards, Svensk Kemisk Tidskrift7, no. 8 (1966) 8-19. 

Other applications. Phenylmercuric acetate has been used in aqueous preparations such as inks, adhesives, and caulking compounds, as a catalyst for the manufacture of certain polyurethanes, and as a fungicide in seed dressings and interior and exterior paints (IARC 1993 Reese 1990). Dimethylmercury is used to prepare mercury nuclear magnetic resonance standards (Blayney et al. 1997) and mass spectrometer mercury calibration standards (Toribara et al. 1997). 

Later investigations by Terenyi (1931) showed that a potent seed dressing is formed when dilute, 0.2% copper sulfate solution reacts with 0.09% potassium mercury(II) chloride, inactive itself. He presumed that a complex compound is formed by the interaction of the two compounds which, like copper(II)tetrammine sulfate, was able to penetrate the fungal cell membrane. 

TCMTB efficiently replaces mercury-containing seed dressings, mainly on cotton (Pulido et al., 1973 Pulido and Bolton, 1974). 

Finally, we note that mercury released to the environment, as metal, e.g., by losses from electrolytic cells used for NaOH and Cl2 production, or as compounds such as alkylmercury seed dressings or fungicides, constitutes a serious hazard.50 This is a result of biological methylation to give (CH3)2Hg or CH3Hg+. It is known that models for vitamin B12 such as methylcobaloximes or methylpentacyanocobaltate (Section 25-F) which have Co—CH3 bonds will transfer the CH3 to Hg2 +. There are a number of microorganisms that can perform the same function, possibly by similar routes. 

In addition, some occupational exposure to organic mercury compounds may occur in some countries, where alkyl- (mainly methyl-) and alkoxy- (mainly methoxyethyl-) mercury salts are used as seed dressings (Skerfving and Copplestone, 1976), and phenylmercury is sometimes used as a fungicide. 

C. Mercury The main source of inorganic mercury as a toxic hazard is through the use of materials in dental laboratories and in the manufacture of wood preservatives, insecticides, and batteries. Organic mercury compounds are used as seed dressings and fungicides. 

Organic mercury compounds are equally soluble in lipids, and the rate of breakdown varies according to their derivatization. Due to their good solubility in lipids, they are easily absorbed and mainly accumulated in the central nervous system which is the main target for toxic effects. The compounds mersalyl, phenyl-mercuric acetate, mercuric acetate, and thiomersal, which are all used in the medical world, are of little environmental importance. In contrast, dimethyl mercury and diethyl mercury, which are used as fungicides and seed dressings, are most important. 

Organomercury compounds such as phenylmercuric acetate were widely used as seed dressings but their high toxicity has led to the deaths of birds and other animals which ate the treated seed. This, coupled with the generally strong public feeling against heavy metals such as lead and mercury in the environment, has led to their replacement. 

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