Current Status of Toxic Metals Addition to Environment and Its Consequences

Abstract

“Heavy metals” are the chemical elements which, in their standard state, have a specific gravity of more than about 5 g cm−3 i.e. their densities are five times greater than water. These constitute a very heterogeneous group of elements greatly varied in their chemical properties and biological functions. Heavy metals are kept under environmental pollutant category due to their toxic effects in plants, human and food particularly in areas with high anthropogenic pressure. Heavy metal pollution is one of the most important environmental problems today. Various industries produce and discharge wastes containing different heavy metals into the environment, such as mining and smelting of metalliferous, surface finishing industry, energy and fuel production, fertilizer and pesticide industry and application, metallurgy, iron and steel, electroplating, electrolysis, electro-osmosis, leatherworking, photography, electric appliance manufacturing, metal surface treating, aerospace and atomic energy installation etc. They are widely used in all fields of life i.e. batteries, dyes, alloys, chemical compounds, pharmaceutical and cosmetic products thus suggesting that the risk of pollution is very high. Thus, metal as a kind of resource is becoming shortage and also brings about serious environmental pollution, threatening human health and ecosystem. Three kinds of heavy metals are of concern, including toxic metals (such as Hg, Cr, Pb, Cd, As, etc.), precious metals (such as Pd, Pt, Ag, Au, Ru etc.) and radionuclides (such as U, Th, Ra, Am, etc.). The presence of heavy metal in atmosphere, soil and water, even in traces represent a severe risk to all organisms for their long term toxicological effects. Heavy metal bioaccumulation and biomagnifications in the food chain can be extremely dangerous to human health.