(A) Heavy metals are naturally occurring elements that have a high atomic weight and a density of at least 5 times greater than that of water.Their toxicity depends on several factors including the dose, route of exposure, and chemical species. Because of their high degree of toxicity,arsenic, cadmium, chromium,lead, and mercury rank among the priority metals that are of public health significance.These metallic elements are considered systemic toxicants that are known to induce multiple organ damage, even at lower levels of exposure.