Mercury occurs widely in the biosphere and is a toxic element presenting occupational hazards associated with both ingestion and inhalation. Mercury has no essential function in the human body.
Pesticides and large fish are the most potent sources of mercury. The amount of mercury found in fish is directly proportional to the size of the fish. Mercury enters lakes, rivers, and oceans from industrial discharges. It settles into bacteria which are then eaten by algae; fish eat the algae and man eats the fish. The mercury is concentrated thousands of times as it moves up the chain.
Industrial workers are exposed to mercury-containing products they manufacture. Mercury is used in certain tooth fillings, contaminating the air (from highspeed drilling) and skin of dental workers.
Mercurous chloride preparations can be purchased over-the-counter, including some laxative preparations containing calomel (mercurous chloride). Continued I use of these products can result in mercury accumulation in body tissues, including the brain.
Mercury compounds are also added to some cosmetics to kill bacteria. These preparations can be absorbed through the skin and into the body. Contaminated grain seeds consumed by wild game can affect persons eating the animals.
About 10 percent of the mercury ingested accumulates in the brain. Two forms of mercury, methyl and phenyl mercury, deplete the brain tissues of zinc. Methyl mercury (the kind found in fish) can produce nerve, birth, and genetic defects. Studies have found chromosome damage to persons eating mercury-poisoned fish. Symptoms of methyl mercury poisoning include loss of coordination, intellectual ability, vision, and hearing. Organic mercury can produce redness, irritation, and blistering of the skin. Chest pain, fever, coughing, and chills result from inhalation of mercury vapor.
Symptoms of subacute mercury poisoning may be excessive salivation, stomatitis, and diarrhea; or they may be neurological, such as Parkinsonian tremors, vertigo, irritability, moodiness, and depression. Psychosis, loss of teeth, insomnia, fatigue, headache; numbness of lips, hands, and feet; and loss of memory can occur.
The average intake of mercury from food is estimated to be only 0.5 milligram daily. Oral ingestion of as little as 100 milligrams of mercury chloride produces toxic symptoms, and 500 milligrams is usually always fatal unless immediate treatment is given. Mercury poisoning in man has been treated by penicillamine, a chelating agent.