Mercury:
Mercury
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This page is maintained by: Dr Rick Leah, Jones Building, School of Biological SciencesAny feed back or comment would be welcome. Please emailNB: The HTML has not yet been 'verified' - apologies to any disabled users - I will try to attend to this during this academic yearOriginal material is Copyright University of Liverpool, 2003,
2004, 2005
| Metals occur in varying amounts in sea water and since the sea is the final repository of soluble elements from the terrestrial part of the planet all metals are present to some degree. Some of the so-called Heavy Metals, such as iron, copper, cobalt and zinc are essential in small quantities for the healthy growth of marine organisms. Others, such as mercury, lead and cadmium have no known biological role. All of these metals are toxic if present in excess but the most important marine contaminants are generally considered to be those non-essential heavy metals. Of all of the heavy metals, most attention is currently paid to Mercury by environmental managers because it still poses the greatest threat to human health from pollution of the environment . There are continuing efforts to tighten environmental restrictions on this element as new research reveals that it may be causing neurological damage to unborn and young children. Mercury has been an important industrial material used, for example, in the chlor-alkali industry and in the manufacture of small batteries but is now being phased out. In aquatic sediments bacteria may convert the less toxic, inorganic form of the metal to the more toxic, organic form of methyl mercury. This chemical form is relatively mobile in the environment and tends to accumulate in fish. Consumption of marine (or other) food containing methyl mercury over an extended period may lead to the onset of Minamata disease. This disease, first observed in Minamata Bay in Japan where the local fish-eating community received large doses of mercury derived from a local chemical factory manufacturing acetaldehyde and vinyl chloride, has neurological symptoms which include, mental disturbance, ataxia and impairment of gait, speech and hearing. In the original incident a considerable number of fatalities (43, a number which has increased over the years) were caused with many more people (>700, perhaps as many as 3000) being irreversibly affected. Mercury is a natural contaminant of the marine system and since methyl mercury moves up the food chain easily (in some circumstances actually biomagnifying) some large predatory fish such as tuna and swordfish have naturally high levels which may approach or even exceed acceptable limits for human consumption in large, older specimens. There are normally no apparent adverse health effects in the fish themselves, the risk is to the next level of consumer in this case humans. (However, wildlife such as birds can be adversely affected directly) Mercury in the news Sources Chloralkali industry Toxicological Assessment of Health Risks International Forums etc Activist Organisations Mercury related Links |
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