Lead is a highly toxic heavy metal that acts as a nonspecific poison affecting all body systems and has no known biological requirement. Absorption of low concentrations may result in a wide range of sublethal effects in animals, and higher concentrations may result in mortality (Demayo et al. 1982).
Lead has been mined and smelted by humans for centuries, but the use of lead-based products increased greatly following the Industrial Revolution. Consequently, lead today is ubiquitous in air, water, and soil, in both urban and rural environments (Eisler 2000). Vertebrates are exposed to lead mainly via inhalation and ingestion. A proportion of lead entering the body is absorbed into the bloodstream and subsequently becomes distributed among body tissues, primarily the blood, liver, kidney, and bone. As a result of anthropogenic activities, most animals have higher tissue lead concentrations than in preindustrialized times. Although even very low tissue lead concentrations have some measurable physiological effects, the concentrations usually encountered in the wider environment (i.e., distant from lead emission sources) have not generally been considered to directly affect survival of most wildlife.
