Page 39 - Curriculum Visions Dynamic Book

 Unless great care is taken, mercury used in the gold recovery process (see page 37) can get into the water used for cleaning the gold and cause mercury pollution in nearby rivers.
Methylmercury poisoning
Methylmercury is an organic compound of mercury
that is a very effective fungicide. It was first used in
the 1940s as a treatment to prevent cereal seeds from rotting before they could germinate. However, the methylmercury remained on the seeds and was eaten by birds, accumulating in their livers and causing damage to their nervous systems. The birds, in turn, were eaten by animals farther up the food chain, concentrating the mercury even more. If such animals are eaten by people, there is a risk of mercury poisoning and thus a threat to human health.
One of the more tragic examples of the careless use of mercury was the disaster at Minimata Bay in Japan in the 1950s. As in many other parts of the world, mercury salts were discharged into the sea along with other effluent from chemical factories. They settled to the bottom of the bay and were thought to be harmless. However, in the sea they were converted to poisonous methylmercury by bacteria. The methylmercury was then eaten by bottom- feeding animals (who dredge the muddy sediments), which, in turn, were eaten by fish. When the fish were caught and sold at local markets, the mercury finally reached people. It had worked its way right through the food chain. The result was a large number of children born with physical and mental abnormalities.
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