Barium, Elemental

CAS RN:7440-39-3

Toxicity Summary

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.
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