Barium
描述
Barium is a dense alkaline earth metal that occurs in nature as a divalent cation in combination with other elements. Physiologically, it exists as an ion in the body. In addition to its natural presence in the Earth's crust, and therefore its natural occurrence in most surface waters, barium is also released to the environment via industrial emissions. The residence time of barium in the atmosphere may be up to several days. Barium sulfate exists as a white orthorhombic powder or crystals. Barite, the mineral from which barium sulfate is produced, is a moderately soft crystalline white opaque to transparent mineral. The most important impurities are iron(III) oxide, aluminium oxide, silica, and strontium sulfate.Barium sulfate has a low toxicity and relatively high density of about 4.5 g*cm-3 (and thus opacity to X-rays). For this reason it is used as a radiocontrast agent in X-ray imaging of the digestive system (barium meals and barium enemas). Lithopone, a pigment that contains barium sulfate and zinc sulfide, is a permanent white that has good covering power, and does not darken when exposed to sulfides. (Wikipedia). Barium hydroxide is strongly alkaline and therefore corrosive. Barium nitrate caused mild skin irritation and severe eye irritation in rabbits. The lack of reports of skin or eye irritation in humans, despite its widespread use, suggests that barium sulfate, often used as a contrast medium, is not a strong irritant. Useful information on the sensitization potential of barium compounds was not identified. Oral intake from drinking water and food is the most prevalent route of exposure to barium compounds for the general population. For the occupational environment, data from industry in the United Kingdom and predictions made using the Estimation and Assessment of Substance Exposure (EASE) model suggest that exposures can be controlled to less than 10 mg/m3 8 hours time weighted average (total inhalable dust). In some situations, control will be to levels significantly below this value. Short term exposures may be higher than 10 mg/m3 for some tasks.The critical end points in humans for toxicity resulting from exposure to barium and barium compounds appear to be hypertension and renal function. Using a no observed adverse effect level (NOAEL) in humans of 0.21 mg barium/kg body weight per day, a tolerable intake value of 0.02 mg/kg body weight per day for barium and barium compounds has been developed in this document.Dissolved barium in aquatic environments may represent a risk to aquatic organisms such as daphnids, but it is apparently of lesser risk to fish and aquatic plants, although data are limited. No adverse effects have been reported in ecological assessments of terrestrial plants or wildlife, although some plants are known to bioaccumulate barium from the soil.(Concise international chemical assessment document 33; http://www.inchem.org/documents/cicads/cicads/cicad33.htm).
类别
"Industrial/Workplace Toxin", "Food Toxin", "Natural Toxin"
同义词
"Ba(2+)", "Ba2+", "Barium ion", "Barium(2+)", "Barium(2+) ion", "Barium(II)", "Barium(II) cation", "Barium(II) ion"
InChI 标识符
InChI=1S/Ba/q+2
键
InChIKey=XDFCIPNJCBUZJN-UHFFFAOYSA-N
化合物类型
Inorganic compounds
大分类
Homogeneous metal compounds
类型
Homogeneous alkaline earth metal compounds
直接大类
Homogeneous alkaline earth metal compounds
取代基
"Homogeneous alkaline earth metal"
外部描述符
"a cation", "barium cation", "divalent metal cation", "monoatomic dication"
地位
Detected and Not Quantified
蜂窝位置
"Cytoplasm", "Extracellular"
暴露途径
Oral (L214) ; inhalation (L214)
毒性机制
Barium is a competitive potassium channel antagonist that blocks the passive efflux of intracellular potassium, resulting in a shift of potassium from extracellular to intracellular compartments. The intracellular translocation of potassium results in a decreased resting membrane potential, making the muscle fibers electrically unexcitable and causing paralysis. (L214)
代谢
Barium compounds are absorbed via ingestion and inhalation. Barium is principally found in the bone, while small amounts exists in the muscle, adipose tissue, skin, and connective tissue. Barium is not metabolized, but may be transported and incorporated into complexes or tissues. Barium is excreted in the urine and faeces. (L214)
致死剂量
1 to 15 grams for an adult human (barium salts). (T48)
致癌性
No indication of carcinogenicity to humans (not listed by IARC).
用途/来源
Barium compounds are used by the oil and gas industries to make drilling muds, and can also be used in the production of paint, bricks, ceramics, glass, and rubber. They are also often used in pyrotechnics, as they emit a green light when burned. (L214, L215)
最低风险等级
Intermediate Oral: 0.2 mg/kg/day (Barium salts) (L134)
Chronic Oral: 0.2 mg/kg/day (Barium salts) (L134)
健康影响
The health effects of the different barium compounds depend on how well the compound dissolves in water or the stomach contents. At low doses, barium acts as a muscle stimulant, while higher doses affect the nervous system, causing cardiac irregularities, tremors, weakness, anxiety, dyspnea, paralysisand possibly death. Barium may also cause gastrointestinal disturbances, damage the kidneys and cause decreases in body weight. (L214)
症状
Ingesting excess barium may cause vomiting, abdominal cramps, diarrhea, difficulties in breathing, increased or decreased blood pressure, numbness around the face, and muscle weakness. High levels may result in changes in heart rhythm or paralysis and possibly death. (L214)
治疗
Intravenous infusion of potassium often relieves many of the symptoms of barium toxicity. (L214)
维基百科链接
http://en.wikipedia.org/wiki/Barium
创建于
2009-03-06 18:58:05 UTC
更新于
2014-12-24 20:21:07 UTC