Organomercury poisoning

Another major incident concerning methyl mercury was the severe pollution of Minamata bay in Japan (see Box 8.1). Here fish, fish-eating and scavenging birds, and humans feeding upon fish all died from organomercury poisoning. There may have been localized declines of marine species in this area due to methyl mercury, but there is no clear evidence of this. 

Al-Tikriti, K. and Al-Mufti, A.W. (1976). An outbreak of organomercury poisoning among Iraqi farmers, Bull. WHO, 53, 15-21. 

A1-Mufti AW, Copplestone JF, Kazanitzis G, et al. 1976. Epidemiology of organomercury poisoning in Iraq I. Incidence in a defined area and relationship to the eating of contaminated bread. Bull World Health Organ 53(suppl) 23-36. 

A1-Saleem T, Clinical Committee on Mercury Poisoning. 1976. Levels of mercury and pathologic changes in patients with organomercury poisoning. Bull World Health Organ 53(suppl) 99-104. 

Al Damluji SF (1976) Organomercury poisoning in Iraq history prior to the 1971—72 outbreak. Bull WHO 53 (suppl) 11-13. 

The elemental form of mercury was used as a catalyst to make acetaldehyde at an industrial plant near Minamata Bay in Japan. Acetaldehyde is used in the manufacturing of perfumes, plastics, synthetic rubber, and other products. In the 1950s some people developed a specific set of neurotoxic symptoms (effects on the nervous system). Effects included speech impairment, narrowing of the visual field, and ataxia (loss of coordination). In 1963 the disease was identified as organomercurial poisoning, and later became known as Minamata s Disease. 

Then he swiftly produced as many different varieties of the compounds as possible, including dimethylzinc, which convinced other scientists to accept Avogadro s theory, a foundation of atomic chemistry and methyl-mercury iodide, the first of many organomercury compounds known to poison people who eat mercury-contaminated fish. Despite his skill at synthesis, Frankland did not discover tetraethyl lead, the gasoline additive that became one of the most important industrial compounds of the mid-twentieth century (Chapter 6). 

In order to understand the picture of events in the USSR more fully, we should recall similar events in Japan. There, the first signs of poisoning by organomercury compounds were noted in 1956 12 years later all OMPs were banned without exception. 

Many human tragedies have been caused by organomercury compounds in food. In the twentieth century, mercury compounds, usually the most toxic types, were applied as fungicides to seeds. Large-scale poisoning occurred in Iraq in 1971-1972 as a result of an appalling error, when seeds contaminated with Hg compounds were sold for consumption. After that event, the application of Hg compounds in farming practice declined, but a fair amount of the element remains in the soil. 

Mercury can exist in several forms and all of them are toxic. Thus the element itself is poisonous because hquid mercury vaporizes and the vapour can be inhaled and absorbed. It can enter the brain in this state and cause damage there. The salts of mercury (inorganic mercury) can also be absorbed from the gut and can damage the kidneys. Finally, mercury can exist as organomercury in which it is part of an organic compound. These are also very toxic and damage the brain and nervous system. Mercury is... 

Inorganic mercury, such as occurs in mercury salts, is mostly soluble or dispersible in water and therefore would disperse in the environment. At high levels it would certainly be poisonous to wildlife and humans alike but, dispersed in large volumes of water, it would be less of a risk. Under certain conditions, however, inorganic mercury may give rise to organomercury (see below). Inorganic mercury has been used in medicine as a laxative and to treat syphilis in the form of calomel (mercurous chloride) (see case notes). Corrosive sublimate (mercuric chloride) was used as a disinfectant and some traditional Chinese medicines stHl contain it. 

Various forms of inorganic mercury are used in industry in battery production and as catalysts. Mercuric nitrate was previously used in tanneries and the fur trade (see pp. 166-7). Clearly these can cause both pollution and human poisoning. However, the form of mercury most likely to be associated with environmental pollution and to cause problems is organomercury. This is because in this form mercury is soluble in fat and can accumulate in animals in the food chain. The cases of serious environmental mercury pollution and poisoning illustrate this well. 

Ever since they were first reported, organometallic compounds have been known to have biological effects. The experiences of Frankland and Bunsen have already been mentioned. Two workers were poisoned, both fatally, by dimethylmercury in 1866 (H5). Industrial development of metal carbonyls and tetraethyllead caused a number of deaths 188, 265). In general, organoarsenic compounds have been most investigated for their toxic effects, with organomercury compounds a close second. Table V outlines the chronology of these developments, and Fig. 2 shows some representative compounds studied. 

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