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Mercury toxicity consists in the damage of biomembranes and combination with body proteins. This results in the impairment of many biological processes that are indispensable for keeping the body alive. The threshold dose of mercury, i.e. the concentration that is considered safe, is 0.05 mg Hg per m3 in air, therefore, spilled mercury poses a threat of poisoning.

The toxic effects of mercury on living organisms depend to a large extent on the type of its chemical compound and the period of time during which it has been accumulating in the body. Organic mercury compounds, i.e. the so-called methylmercury, are the most toxic.

Mercury accumulation in seafood and fish as well as other animal and vegetable food poses ato humans, especially when they consume fish (particularly tuna), crabs and snails. Fish absorb mercury through their gills and with food consumed. As mercury is still present in fish organisms even for a period of a few hundred days, its content in older fish is higher. When someone has eaten a fish with mercury particles in it, the particles start to accumulate in their body. 80 per cent of mercury absorbed by the respiratory system remain in the body while the portion of mercury which has penetrated into the bloodstream further penetrates into the blood-brain barrier and, in the case of pregnant women, into the placenta, causing mercury accumulation in the brain and tissues of the foetus. What is more, more than 90 per cent of inorganic mercury accumulate in the kidneys.

Mercury, however, can be found not only in food. Crude oil and coal combustion products also contain mercury that pollutes the environment (for example, in the vicinity of a coal power plant, 400 g of Hg/ha can drop annually). Mercury can also pollute the soil due to the use of fungicides (especially seed dressings) and it is a regular ingredient of municipal waste which, when used to fertilize the soil, can pose a serious risk of introducing mercury into food products.

The largest mass poisoning by industrial mercury compounds occurred between 1953 and 1970 in Japan, in the Minamata Bay area, where untreated industrial wastewater from afactory was disposed of. Mercury, present in the wastewater, accumulated in fish living in the bay which were later consumed by the inhabitants of the coast. Those people experienced poisoning symptoms: vision and hearing impairment, lack of coordination, convulsions and tremors. The most severe cases ended in paralysis, deafness, blindness and even death. In total, approximately 100,000 people suffered from the poisoning.

Mercury-containing products cannot, therefore, be disposed of as other household waste. Due to high toxicity of mercury, many countries have implemented special technological processes in order to recycle mercury and its compounds and eliminate the threat posed by mercury-containing waste disposal at landfill sites.

Despite these efforts, regrettably,of mercury-containing waste in Poland is disposed of at landfill sites and industrial waste from factories producing mercury-containing products additionally increases slag heaps.

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