Cadmium (BioDeep_00000872158)

描述信息

Cadmium (group IIB of the periodic table of elements) is a heavy metal posing severe risks to human health. Physiologically, it exists as an ion in the body. Up to this day, it could not be shown that cadmium has any physiological function within the human body. Interest has therefore risen in its biohazardous potential. As first described by Friedrich Stromeyer (Gottingen, Germany) in 1817, cadmium intoxication can lead to kidney, bone, and pulmonary damages.; Cadmium is regularly found in ores together with zinc, copper and lead. Therefore volcanic activity is one natural reason for a temporary increase in environmental cadmium concentrations. Cadmium is widely used in industrial processes, e.g as an anticorrosive agent, as a stabilizer in PVC products, as a colour pigment, a neutron absorber in nuclear power plants, and in the fabrication of nickel cadmium batteries. Phosphate fertilizers also show a big cadmium load. Although some cadmium containing products can be recycled, a large share of the general cadmium pollution is caused by dumping and incinerating cadmium polluted waste. In Scandinavia for example, cadmium concentration in agricultural soil increases by 0.2 percent per year. Total global emission of cadmium amounts to 7000 t/year.; The maximum permissible value for workers according to German law is 15 ug/l. For comparison: Non-smokers show an average cadmium blood concentration of 0.5 ug/l.; Basically there are three possible ways of cadmium resorption: Gastrointestinal, pulmonary and dermal. The uptake through the human gastrointestinal is approximately 5 percent of an ingested amount of cadmium, depending on the exact dose and nutritional composition. The major source of inhalative cadmium intoxication is cigarette smoke. The human lung resorbes 40 to 60 percent of the cadmium in tobacco smoke. Little research has been done on dermal absorption of cadmium. Two mechanisms facilitate cadmium absorption by the skin: binding of a free cadmium ion to sulfhydryl radicals of cysteine in epidermal keratins, or an induction and complexing with metallothionein. Once taken up by the blood, the majority of cadmium is transported bound to proteins, such as Albumin and Metallothionein.; The first organ reached after uptake into the GI-blood is the liver. Here cadmium induces the production of Metallothionein. After consecutive hepatocyte necrosis and apoptosis, Cd-Metallothionein complexes are washed into sinusoidal blood. From here, parts of the absorbed cadmium enter the entero-hepatical cycle via secretion into the biliary tract in form of Cadmium-glutathione conjugates. Enzymatically degraded to cadmium-cysteine complexes in the biliary tree, cadmium reenters the small intestines. The main organ for long-term cadmium accumulation is the kidney. Here the half life period for cadmium is approx. 10 years. A life long intake can therefore lead to a cadmium accumulation in the kidney, consequently resulting in tubulus cell necrosis. The blood concentration of cadmium serves as a reliable indicator for a recent exposition, while the urinary concentration reflects past exposure, body burden and renal accumulation. Excretion of Cadmium takes place via faeces and urine. (PMID: 16961932); Cadmium (pronounced /?kædmi?m/, KAD-mee-?m) is a chemical element with the symbol Cd and atomic number 48. The soft, bluish-white transition metal is chemically similar to the two other metals in group 12, zinc and mercury. Similar to zinc it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low melting point for a transition metal. Cadmium is a relatively abundant element. Cadmium was discovered in 1817 by Friedrich Strohmeyer as an impurity in zinc carbonate.; Cadmium is a common impurity in zinc ores, and it is most often isolated during the production of zinc. Some zinc ores concentrates from sulfidic zinc ores contain up to 1,4\\% of cadmium. In 1970s the output of cadmium was 6.5 pounds per ton of zinc. Z...

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