Heavy metals are metals or chemical compounds containing metals, which are a concern to the environment. This definition was made, when the effects of cadmium, mercury and lead became known. All of these are denser than iron. The definition has since been applied to any other similarly toxic metal, or metalloid such as arsenic, regardless of density. Commonly encountered heavy metals are chromium, cobalt, nickel, copper, zinc, arsenic, selenium, silver, gold, cadmium, antimony, mercury, thallium, tungsten, platinum and lead. The heaviest metal by density is osmium. Although most heavy metals are toxic, not all of them are. For example, gold, which is one of the heaviest metals, is non-toxic and inert to all body chemistry. Some gold compounds are toxic, however. More specific definitions of a heavy metal have been proposed; none have obtained widespread acceptance.
References[change | change source]
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