Metals have an impact on human health in many ways. Some elements are
essential micronutrients with a human requirement of no more than a few
milligrams per day. However, micronutrients may become harmful when
their ingestion rates are too high. Some elements are likely to be
essential micronutrients, although their positive role in human
nutrition. Trace elements are well known as toxic if their intake
through ingestion or inhalation is excessive.