Bismuth (BioDeep_00000014455)

描述信息

Bismuth is a brittle metal with a white, silver-pink hue. Of all the metals, it is the most naturally diamagnetic, and only mercury has a lower thermal conductivity. It is generally considered to be the last naturally occurring stable, non-radioactive element on the periodic table, although it is actually slightly radioactive, with an extremely long half-life. Bismuth compounds are used in cosmetics, medicines (as antacids), and in medical procedures. As a result trace levels of bismuth are found in almost all humans. Physiologically, it exists as an ion in the body. The normal concentration of bismuth in blood is between 1 and 15 ug/L, but absorption from oral preparations produces a significant rise. Distribution of bismuth in the organs is largely independent of the compound administered or the route of administration: the concentration in kidney is always highest and the substance is also retained there for a long time. It is bound to a bismuth-metal binding protein in the kidney, the synthesis of which can be induced by the metal itself. Elimination from the body takes place by the urinary and faecal routes, but the exact proportion contributed by each route is still unknown. Elimination from blood displays multicompartment pharmacokinetics, the shortest half life described in humans being 3.5 minutes, and the longest 17 to 22 years. A number of toxic effects have been attributed to bismuth compounds in humans: nephropathy, encephalopathy, osteoarthropathy, gingivitis, stomatitis and colitis. Whether hepatitis is a side effect, however, is open to dispute. Each of these adverse effects is associated with certain bismuth compounds. Bismuth encephalopathy occurred in France as an epidemic of toxicity and was associated with the intake of inorganic salts including bismuth subnitrate, subcarbonate and subgallate. In the prodromal phase patients developed problems in walking, standing or writing, deterioration of memory, changes in behaviour, insomnia and muscle cramps, together with several psychiatric symptoms.
Bismuth is a chemical element with symbol Bi and atomic number 83. Bismuth compounds are used in cosmetics, pigments, and a few pharmaceuticals, notably Pepto-Bismol. Bismuth has unusually low toxicity for a heavy metal. As the toxicity of lead has become more apparent in recent years, there is an increasing use of bismuth alloys (presently about a third of bismuth production) as a replacement for lead. [Wikipedia]

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