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Mercury Definition


Mercury can be extremely toxic, especially to infants and children. Mercury occurs in three forms: the elemental form (also referred to as metallic), inorganic salt, and organic compounds called methylmercury. Each form has characteristic pathways of exposure and unique health effects. Mercury affects the nervous system, causing brain, nerve, kidney, and lung damage. Though symptoms may be absent or non-specific, a fact that will hinder diagnosis, they frequently include skin rashes, particularly redness and peeling of the hands and feet in children; tremors; muscular weakness; inability to walk; convulsions; personality changes; memory loss; and in extreme cases, death. The developing fetus is the most sensitive to the effects of mercury, and so women of child-bearing age are the population of greatest concern. Children of women exposed to relatively high levels of methylmercury during pregnancy (and through breast feeding) have exhibited a variety of abnormalities, including delayed onset of walking and talking and reduced neurological test scores.

Elemental mercury, such as that which was once found in thermometers, slowly evaporates when exposed to the air. Nevertheless, small amounts spilled can reach contamination levels with exposure to room temperature air. Vacuuming, even with specially designed vacuums, can exacerbate the problem by increasing levels of mercury vapor. From there, mercury vapor is easily absorbed in the lungs and is toxic at low concentrations in air. Elemental mercury can also be absorbed through the skin and cause allergic reactions.

According to the National Institutes of Health, ingestion of inorganic mercury compounds can cause severe renal and gastrointestinal toxicity. Organic compounds of mercury such as methylmercury are considered the most toxic forms of the element, with exposures resulting in neurological damage and even death.

Mercury in the Environment
Releases of mercury to the environment are usually in the form of elemental or inorganic forms. Mercury is a naturally occurring element released when volcanoes erupt and rocks erode. It can also be released into the air through industrial pollution, including fossil fuel combustion, metal sulfide ore smelting, gold refining, cement production, refuse incineration, and industrial applications of metals.

Mercury concentrations in air are usually low and of little direct concern, but when mercury enters water, biological processes change the chemical form to methylmercury, which is the organic, more toxic form found in fish. Methylmercury bioaccumulates through the food chain and, once in the body, can affect the fetal and adult nervous systems.

For more information about NACCHO’s projects that address mercury, click here.