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Name: donna
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how does mercury get into fish in rivers. what is the ecological process involved which could produce toxic levels of mercury in fish and eventually get into humans?

Hi Donna!

Nowadays mercury or its compounds are used at a high scale in many industries as the manufacture of chemicals, paints, household itens, pesticides and fungicides. These products can contaminate humans (and mamals) by direct contact, ingestion or inhalation. Besides the air can become contaminated also, and since mercury compounds produce harmful effects in body tissues and functions, that pollution is very dangerous.

Now for your question: Efluent wastes containing mercury in various forms sometimes are dropped in sea water or in rivers or lakes. There the mercury may be converted by bacteria, that are in the muddy sediments, into organic mercurial compounds particularly the highly toxic alkyl mercurials ( methyl and di-methyl mercury), which may in turn be concentrated by the fishes and other aquatic forms of life that are used as food by men. The fishes dont seem to be affected but they are able to concentrate mercury in high poisoning levels, and if human beings, mamals or birds eat these containing mercury fishes, algae, crabs or oysters they will be contaminated and poisoned.

By the middle of last century that danger was not quite known and some mass disaster killed many people poisoned by that way.

Hopefully now ecology has its turn and laws or recommendations all over the world prevents (or try to prevent) the careless disposition of these dangerous wastes.

Thanks for asking NEWTON!

(Dr. Mabel Rodrigues)

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