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A heavy metal is any of a number of higher atomic weight elements, which normally presents as a metallic substance at room temperatures. There are several different definitions of which elements fall in this class designation:
Relationship to living organisms Living organisms require trace amounts of some heavy metals, including cobalt, copper, manganese, molybdenum, vanadium, strontium, and zinc, but excessive levels can be detrimental to the organism. Other heavy metals such as mercury, lead and cadmium have no known vital or beneficial effect on organisms, and their accumulation over time in the bodies of mammals can cause serious illness. The pathway for toxic effects on humans is normally: (i) for the entry of heavy metals into the atmosphere as industrial stack gas; (ii) or to enter the soil as a soil contaminant; (iii) or to enter groundwater as a water pollutant; or to be deposited in ocean bottoms or bay mud, which materials at a later time be dredged to the surface. In medical usage, the definition is considerably looser, and heavy metal poisoning can include excessive amounts of iron, manganese, aluminium, or beryllium (the second-lightest metal) as well as the true heavy metals. Sources See also | ||||||||
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