毒理性
识别:钡是一种淡黄色的白色软金属,具有强烈的电正性。在自然界中,钡以化合态存在,主要形式为硫酸钡(重晶石)和碳酸钡(钡白云石)。钡也以少量存在于火成岩中,如长石和云母。它也可能作为化石燃料的自然组成部分,并存在于空气、水和土壤中。人类暴露:人类可以通过空气、水或食物接触钡。另一个钡的来源是核辐射尘埃。普通人在骨骼中积累了91%的钡。在各种组织中可以发现微量的钡,如主动脉、大脑、心脏、肾脏、脾脏、胰腺和肺。人体内钡的总含量随着年龄的增长而增加,体内水平取决于个人的地理位置/SRP:一些来源说钡随年龄增长而减少。在所有死胎样本中都发现了钡,这表明它能够穿过胎盘。吸入的钡可以通过肺部或直接从鼻腔膜进入血液。钡通过尿液和粪便排出,排出速率因给药途径而异。在24小时内,大约20%的钡剂量(注入人体)通过粪便排出,大约5%通过尿液排出。血浆中的钡在24小时内几乎从血液中排出。动物/植物研究:通常,钡不会在常见植物中积累到足以对动物产生毒性的量。大量钡(高达1260 mg/kg)积累在豆类、紫花苜蓿和大豆中。动物摄入的钡主要通过粪便而不是尿液排出。估计大鼠钡的生物半衰期为90-120天。动物摄入钡的急性效应包括流涎、恶心、腹泻、心动过速、低钾血症、抽搐、骨骼肌弛缓性瘫痪、呼吸肌麻痹和心室纤颤可能导致死亡。各种研究表明,钡对心室自动性和心脏起搏电流有不利影响。给麻醉狗静脉注射钡表明,这些急性效应是由于迅速且严重的低钾血症。钡会引起轻微的皮肤和眼睛刺激。饮用水中钡含量与出生缺陷发生率之间没有明确的关联。没有证据表明钡是致癌的。在大鼠饮用水中给予10或100 mg钡/L,16个月后出现高血压,但在1 mg/L时并未引起任何血压变化。16个月时(100 mg钡/L)对心肌功能的分析显示心脏收缩性和兴奋性显著改变,心肌代谢紊乱,心血管系统对戊巴比妥钠的敏感性增加。钡具有化学和生理学特性,使其能够与钙竞争并取代钙,特别是与肾上腺儿茶酚胺和神经递质(如乙酰胆碱和去甲肾上腺素)释放相关的特性。钡影响发芽细菌孢子的发育,并对不同微生物产生多种特定影响,包括抑制细胞过程。关于钡对水生生物的影响的信息很少。在30天的暴露后,对鱼的存活没有影响。然而,在21天的研究中,水蚤的繁殖受损和生长减少。海洋植物以及无脊椎动物可能会从海水中积极积累钡。
IDENTIFICATION: Barium is a yellowish white soft metal that is strongly electropositive. In nature barium occurs in a combined state, the principal forms being barite (barium sulfate) and witherite (barium carbonate). Barium is also present in small quantities in igneous rocks such as feldspar and micas. It may also be found as a natural component of fossil fuel and is present in the air, water and soil. HUMAN EXPOSURE: Exposure to barium can occur through the air, water or food. Another souce of barium is nuclear fallout. The average person accumulates 91% of barium in bones. Trace quantities are found in various tissues such as the aorta, brain, heart, kidney, spleen, pancreas and lung. Total barium in human beings tends to increase with age and the levels in the body depend on the geographical location of the individual /SRP: Some sources say barium decreases with age/. Barium has also been found in all samples of stillborn babies, suggesting it can cross the placenta. Inhaled barium can be absorbed through the lung or directly from the nasal membrane into the blood. Barium is eliminated in the urine and feces, the rates varying with the route of administration. Within 24 hr approximately 20% of the barium dose, injected into humans was eliminated in the feces and approxinately 5% in the urine. Plasma barium is almost eliminated from the blood stream within 24 hr. ANIMAL/PLANT STUDIES: In general, barium does not accumulate in common plants in sufficient quantities to be toxic to animals. Large quantities of barium (as high as 1260 mg/kg) accumulated in legumes, alfalfa and soybeans. The elimination of ingested barium in animals occurs mainly in the feces rather than in the urine. An estimated of the biological half-life for barium in the rat is 90-120 days. The acute effects of barium ingestion in animals includes salivation, nausea, diarrhea, tachycardia, hypokalaemia, twitching, flacid paralysis of skeletal muscle, respiratory muscle paralysis and ventricular fibrillation may lead to death. Various studies have demonstrated the detremental effect of barium upon ventricular automaticity and pacemaker current in the heart. IV barium injections to anesthetized dogs indicated that these acute effects were due to prompt and substantial hypokalemia. Barium causes mild skin and eye irritation. No conclusive association was found between the level of barium in the drinking water and the incidence of congenital malformations. There is no evidence that barium is carcinogenic. Rats given 10 or 100 mg barium/L in their drinking water for 16 months experienced hypertension, but at a level of 1 mg/L did not induce any blood pressure changes. Analysis of myocardial function at 16 months (100 mg barium/L) revealed significantly altered cardiac contractility and excitability, myocardial metabolic disturbances and hypersensitivity of the cardiovascular system to sodium pentobarbital. Barium posesses chemical and physiological properties that allow it to compete with and replace calcium, particularly those relating to the release of adrenal catecholamines and neurotransmitters such as acetylcholine and norepinephrine. Barium affects the development of germinating bacterial spores and has a variety of specific effects on different microorganisms including the inhibition of cellular processes. Little information is available on the effects of barium on aquatic organisms. There were no effects on survival of fish following exposure for 30 days. However, in a 21 day study, impairment of reproduction and reduction in growth in daphnids. Marine plants as well as invertebrates may actively accumulate barium from sea water.
来源:Hazardous Substances Data Bank (HSDB)