Heavy metals

Heavy metals are a group of metals with relatively high densities, atomic weights, or atomic numbers. The criteria used, and whether metalloids are included, vary depending on the author and context. In metallurgy, for example, a heavy metal may be defined on the basis of density, whereas in physics the distinguishing criterion might be atomic number, while a chemist would likely be more concerned with chemical behaviour.

Definition

The term heavy metal refers to any metallic chemical element that has a relatively high density and is toxic or poisonous at low concentrations. Examples of heavy metals include mercury (Hg), gold (Au), platinum (Pt), copper (Cu), and lead (Pb).

Health effects

Heavy metals are dangerous because they tend to bioaccumulate. Bioaccumulation occurs when an organism absorbs a substance at a rate faster than that at which the substance is lost or eliminated by catabolism and excretion. Thus, even a small exposure over a long period of time can lead to a build up of heavy metals in the body, leading to heavy metal poisoning. This can result in damage to the central nervous system, cardiovascular system, gastrointestinal system, and other bodily organs.

Heavy metal poisoning

Heavy metal poisoning could result, for instance, from drinking-water contamination (e.g. lead pipes), high ambient air concentrations near emission sources, or intake via the food chain. Heavy metals are dangerous because they tend to bioaccumulate. Bioaccumulation means an increase in the concentration of a chemical in a biological organism over time, compared to the chemical's concentration in the environment.

See also

• Lead poisoning
• Mercury poisoning
• Copper toxicity
• Iron poisoning
• Metal toxicity

References

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