Since the Industrial Revolution, the production of heavy metals such as lead, copper, and zinc has increased exponentially. Between 1850 and 1990, production of these three metals increased nearly 10-fold, with emissions rising in tandem . (See Heavy Metal Production has Soared Since 1850.) Heavy metals have been used in a variety of ways for at least 2 millennia. For example, lead has been used in plumbing, and lead arsenate has been used to control insects in apple orchards. The Romans added lead to wine to improve its taste, and mercury was used as a salve to alleviate teething pain in infants  .
|Heavy metal production has soared since 1850|
|Global production and consumption of selected toxic metals, 1850-1990|
|Source: J.O.Nriagu, “History of Global Metal Pollution,” Science, Vol. 272 (April 12, 1996), pp. 223-224.|
The toxicity of these metals has also been documented throughout history: Greek and Roman physicians diagnosed symptoms of acute lead poisoning long before toxicology became a science. Today, much more is known about the health effects of heavy metals. Exposure to heavy metals has been linked with developmental retardation, various cancers, kidney damage, and even death in some instances of exposure to very high concentrations. Exposure to high levels of mercury, gold, and lead has also been associated with the development of autoimmunity, in which the immune system starts to attack its own cells, mistaking them for foreign invaders . Autoimmunity can lead to the development of diseases of the joints and kidneys, such as rheumatoid arthritis, or diseases of the circulatory or central nervous systems .
Despite abundant evidence of these deleterious health effects, exposure to heavy metals continues and may increase in the absence of concerted policy actions. Mercury is still extensively used in gold mining in many parts of Latin America. Arsenic, along with copper and chromium compounds, is a common ingredient in wood preservatives. Lead is still widely used as an additive in gasoline. Increased use of coal in the future will increase metal exposures because coal ash contains many toxic metals and can be breathed deeply into the lungs. For countries such as China and India, which continue to rely on high-ash coal as a primary energy source, the health implications are ominous .
Once emitted, metals can reside in the environment for hundreds of years or more. Evidence of human exploitation of heavy metals has been found in the ice cores in Greenland and sea water in the Antarctic. The lead contents of ice layers deposited annually in Greenland show a steady rise that parallels the mining renaissance in Europe, reaching values 100 times the natural background level in the mid-1990s .
Mining itself, not only of heavy metals but also of coal and other minerals, is another major route of exposure. Despite some noted improvements in worker safety and cleaner production, mining remains one of the most hazardous and environmentally damaging industries. In Bolivia, toxic sludge from a zinc mine in the Andes had killed aquatic life along a 300-kilometer stretch of river systems as of 1996. It also threatened the livelihood and health of 50,000 of the region’s subsistence farmers . Uncontrolled smelters have produced some of the world’s only environmental “dead zones,” where little or no vegetation survives. For instance, toxic emissions from the Sudbury, Ontario, nickel smelter have devastated 10,400 hectares of forests downwind of the smelter .
170. Jerome O. Nriagu, “A History of Global Metal Pollution,” Science, Vol. 272, No. 5259 (April 12, 1996), p. 223.
171. David L. Eaton and William O. Robertson, “Toxicology,” in Textbook of Clinical Occupational and Environmental Medicine, Linda Rosenstick and Mark R. Cullen, eds. (WB Saunders Company, Philadelphia, 1994), pp. 116 -117.
172. Cheryl Simon Silver and Dale S. Rothman, Toxics and Health: The Potential Long-Term Effects of Industrial Activity (World Resources Institute, Washington, D.C., 1995), p. 7.
173. Janet Glover-Kerkvliet, “Environmental Assault on Immunity,” Environmental Health Perspectives, Vol. 103, No. 3 (March 1995), pp. 236 -237.
174. Ibid., p. 237.
175. Op. cit. 172, p. 7.
176. Op. cit. 170.
177. Rob Edwards, “Toxic Sludge Flows Through the Andes,” New Scientist (November 23, 1996), p. 4.
178. John E. Young, “Mining the Earth,” Worldwatch Paper No. 109 (Worldwatch Institute, Washington, D.C., July 1992), p. 21.