|Arsenic, cadmium, chromium, copper, nickel, lead and mercury are the most common heavy metal pollutants, and mercury and cadmium are of the greatest concern. Living organisms, including marine species, concentrate heavy metals in their tissues, becoming highly toxic in the process. Hot spots for heavy metals are operational and former mining sites, industrial production ? particular foundries and smelters ? untreated sewage sludge and diffuse sources such as metal piping, traffic and combustion by-products from coal-burning power stations.|
In 1996, the OECD agreed to phase out many uses of lead, and in June 1998, the ECE added a protocol on heavy metals to the Convention on Long-range Transboundary Air Pollution.