The heavy metals most often linked to human poisoning are lead, mercury, aluminum, arsenic, nickel and cadmium. Other heavy metals, including copper, and zinc are required by the body in small amounts, but can be toxic in larger doses. Sources of heavy metals in the environment include air emissions from coal-burning plants, smelters, and other industrial facilities; waste incinerators; process wastes from mining and industry; and lead in household plumbing and old house paints. While certain types of industrial facilities are required by the EPA to report their releases of some heavy metals to the Toxics Release Inventory (TRI), other major sources - including power plants and waste incinerators - are not. Consequently, the TRI may significantly under-report actual environmental releases of some metals. For Current EPA Density Maps, click here.
Heavy metals can also enter the environment through natural processes. For example, in some parts of the U.S., naturally occurring geologic deposits of arsenic dissolve into groundwater, potentially resulting in unsafe levels of this metal in drinking water supplies. Once released to the environment, metals can remain for decades or centuries, increasing the likelihood of human exposure.
Humans are exposed to heavy metals through inhalation of air pollutants, consumption of contaminated drinking water, exposure to contaminated soils or industrial waste, or consumption of contaminated food. Food sources such as vegetables, grains, fruits, fish and shellfish can become contaminated by accumulating metals from surrounding soil and water. Heavy metals cause serious health effects, including reduced growth and development, cancer, organ damage, nervous system damage, and in extreme cases, death. Exposure to some metals, such as mercury and lead, may also cause development of autoimmunity, in which a person's immune system attacks its own cells. This can lead to joint diseases such as rheumatoid arthritis, and diseases of the kidneys, circulatory system, and nervous system. Find out more about pollution in your local area, click here.
Heavy Metals and Children
Metals are particularly toxic to the sensitive, rapidly developing systems of the fetus, infants and young children. Some metals, such as lead and mercury, easily cross the placenta and damage the fetal brain. Childhood exposure to some metals can result in learning difficulties, memory impairment, damage to the nervous system, and behavioral problems such as aggressiveness and hyperactivity. At higher doses, heavy metals can cause irreversible brain damage. Children may receive higher doses of metals from food than adults, since they consume more food for their body weight than adults.
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