mercury poisoning

mercury poisoning, harmful effects of various mercury compounds on body tissues and functions. Certain modern industrial and biological processes concentrate mercury compounds to dangerous levels. Mercury is used on a substantial scale in numerous industries, such as the manufacture of chemicals, paints and various household items, pesticides, and fungicides. In addition to the danger from many consumer goods that contain potentially harmful levels of mercury, the air may be contaminated by mercury vapours, fumes, and dusts and the waters by effluent wastes containing mercury in various forms. The latter may then be converted by bacteria in the muddy sediments into organic mercurials, which may in turn be concentrated by the fishes and other aquatic forms of life that are foods for man.

Depending on the type of mercury compound and the mode of contact, the symptoms of intoxication in man vary. Acute mercury poisoning usually results from the accidental or suicidal ingestion of soluble mercury salts, such as mercuric chloride. The effect is severe inflammation of the digestive tract. Abdominal cramps with nausea and vomiting and bloody diarrhea commonly occur within hours. The absorbed mercury is concentrated in the kidneys, where it poisons the blood-filtering structures; as a result, there is first a decrease and then complete cessation of urine output, causing the accumulation of toxic substances in the blood (uremia) and death.

Chronic mercury poisoning may result from the occupational inhalation of mercury vapours, dusts, or volatile organic mercurials or from the absorption through the skin of various mercury salts (such as mercuric nitrate, used in making felt for hats). Symptoms may include a metallic taste and excessive production of saliva; inflammation of the membranes of the mouth; loosening of the teeth; the formation of a blue line on the gums; pain, numbness, and tremor in the extremities; loss of weight and appetite; and mental and personality changes marked by depression and a tendency to withdraw.

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Certain mercurial compounds are used as diuretics; that is, are used to promote the production of urine. Sensitivity reactions to these diuretics may cause asthma, hives, other skin lesions, and sudden death. The use of ointments containing mercury or the long-term ingestion of calomel (mercurous chloride, a cathartic) may produce fever, rash, and enlargement of the spleen and lymph nodes. In infants and young children, a disorder known as acrodynia, or “pink disease,” is believed to be caused by an organic mercury compound, phenylmercuric propionate, which is incorporated into house paints to prevent the growth of mold. Symptoms of acrodynia include irritability, insomnia, loss of appetite, loosening of teeth, inflammation of the mouth, and redness of the skin.

Poisoning with organic mercurial compounds is characterized by lesions of the central nervous system. This form of mercury poisoning became known as Minamata disease because of a dramatic outbreak that occurred in Minamata, Japan, in the early 1950s. There was progressive weakening of the muscles, loss of vision, impairment of the cerebral functions, eventual paralysis, and, in some cases, coma and death. Minamata seabirds and household cats, which, like the fishermen and their families, subsisted mainly on fish, showed signs of the same disease. This led to the discovery of high concentrations of methyl mercurials in fish and shellfish taken from the bay. The source of mercury was traced to the effluent from a factory. Other outbreaks of this disease involving large numbers of persons have taken place where farmers who received grain seeds treated with an organic mercury compound ate the seeds instead of planting them.