Cadmium is a silver-white, malleable metal that exists as crystals having the hexagonal close-packed arrangement, and is usually found combined with other elements in mineral compounds (e.g., cadmium oxide, cadmium chloride, cadmium sulfate, and cadmium sulfide). Cadmium dust can ignite spontaneously in air and is both flammable and explosive when exposed to heat, flame, or oxidizing agents. Toxic fumes are emitted when cadmium metal is heated to high temperatures. Cadmium lacks a definite taste or odor. It was discovered as an impurity in zinc carbonate by Friedrich Strohmeyer in Germany in 1817. Most cadmium is obtained as a byproduct of the chemical treatment of copper, lead, and zinc ores, although it is a naturally occurring element in Earth's crust.
Industrial uses of cadmium include electroplating and the manufacture of batteries, metal coatings, and alloys . Cadmium is also used as a pigment in paints and plastics. Some fertilizers also contain cadmium.
Food and cigarette smoke are the most likely sources of cadmium exposure for the general population. The total daily intake of cadmium from food, water, and air for an adult living in North America or Europe is estimated to be between 10 and 40 micrograms (3.53 × 10−7 and 1.41 × 10−6 ounces). The U.S. Environmental Protection Agency has established oral reference doses for cadmium: 0.0005 mg/kg/day (from water) and 0.001mg/kg/day (from food). The reference dose is the level that may be consumed over a lifetime with minimal risk of adverse effects. Occupational exposure may occur in individuals who work with cadmium or in industries that produce cadmium. About 15 percent of inhaled cadmium is absorbed by the body, whereas 5 to 8 percent is absorbed from the gastrointestinal tract following cadmium ingestion. Cadmium is transported in the blood by hemoglobin, as well as by albumin and other large molecular weight proteins. The half-life for cadmium in the body is about thirty days, with most of the excess cadmium accumulating in the liver and kidneys. Cadmium is excreted primarily in the urine.
Acute toxicity may result from the ingestion of cadmium. Symptoms that follow cadmium ingestion may include abdominal pain, nausea, and vomiting; symptoms that follow inhalation include acute respiratory irritation and/or inflammation. Epidemiologic studies in humans have found associations between cadmium exposure and lung cancer, and between cadmium exposure and prostate cancer. Other evidence of the carcinogenic potential of cadmium has been found in the results of animal studies.
see also Toxicity.
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cadmium (kăd´mēəm) [from cadmia, Lat. for calamine, with which cadmium is found associated], metallic chemical element; symbol Cd; at. no. 48; at. wt. 112.411; m.p. 321°C; b.p. 765°C; sp. gr. 8.65 at 20°C; valence +2. Cadmium is a lustrous, silver-white, ductile, very malleable metal. It belongs to Group 12 of the periodic table, and resembles zinc in its chemical properties. Like zinc, it tarnishes in moist air. Cadmium oxide, a brown powder formed by burning the metal in air, is used in electroplating; it is also made by heating cadmium hydroxide. Cadmium forms a carbonate, a chloride, and several complex ions. Cadmium yellow (the sulfide) is a very durable yellow pigment used in paints. The major use of cadmium is as a coating that is electroplated on iron and steel to prevent corrosion; it is preferable to zinc for protection from alkalies. Cadmium is also used in so-called fusible metals, which are low-melting alloys such as Wood's metal, used in automatic fire sprinklers and alarm systems. Cadmium is used in alkaline nickel-cadmium electric storage cells, which have a greater storage capacity than an equal weight of lead-acid storage cells. It has also found some use in the control of nuclear reactions, since it absorbs neutrons. Cadmium does not occur uncombined in nature; greenockite, a cadmium sulfide mineral first found in Scotland, is the only commercial ore. Cadmium is obtained principally as a byproduct of the smelting and refining of ores of zinc, especially zinc sulfides, and of lead and copper. The element was discovered in 1817 by Friedrich Stromeyer.
A metallic element that occurs most commonly in nature as the sulfide, CdS. Cadmium has many important industrial applications. It is used to electroplate other metals, in the production of paints and plastics , and in nickel-cadmium batteries. The metal also escapes into the environment during the burning of coal and tobacco . Cadmium is ubiquitous in the environment, with detectable amounts present in nearly all water, air, and food samples. In high doses, cadmium is toxic. In lower doses, it may cause kidney disease, disorders of the circulatory system, weakening of bones, and, possibly, cancer .
See also Itai-Itai disease
cad·mi·um / ˈkadmēəm/ • n. the chemical element of atomic number 48, a silvery-white metal. (Symbol: Cd)
Cd (chemical symbol)
Cd, symbol for the element cadmium.