CAS No. 7440-39-3
Elemental barium is a silver-white metal which comprises approximately 0.05% of the earth’s crust.In nature, it combines with other chemicals such as sulfur or carbon and oxygen. Some barium salts are freely soluble in water, whereas others are practically insoluble (e.g., barium sulfate and barium carbonate). Barium compounds are used by the oil and gas industries to make drilling muds. Barium compounds are also used commercially in paint, bricks, tiles, glass, rubber, depilatories, fireworks, and ceramics. Medically, barium sulfate is used as a contrast medium for taking radiographs of the gastrointestinal tract. Barium salts have also been available as rodenticides.
The general population can be exposed to low amounts of barium in air, water, and food. Certain foods, such as brazil nuts, are high in barium (Genter, 2001). Small amounts of barium can be released into the air during mining and other industrial processes. Workers employed by industries that make or use barium compounds can be exposed to barium dust. In single dose animal studies, soluble forms of barium, such as barium chloride, were relatively well absorbed following inhalation (60-80% of a dose) or ingestion (11-32 % of a dose).Ingested soluble barium was eliminated primarily in feces and to a lesser extent, in urine.Following intravenous injection in animals, about 75 % of a dose of soluble barium was eliminated within 3 days (Reeves, 1986). Insoluble barium salts, such as those used in medical radiographic procedures, are not absorbed when administered.
Human health effects from barium at low environmental doses or at biomonitored levels from low environmental exposures are unknown. The health effects of exposure to barium compounds depend on the dose, chemical form, water solubility, and route of exposure. Toxicity from soluble barium salts is rare, but can occur after intentional or accidental ingestion of barium carbonate in rodenticides (Genter, 2001). Barium blocks cellular efflux of potassium resulting in profound hypokalemia. Symptoms following acute high dose include perioral paresthesias, vomiting, diarrhea, weakness, paralysis, hypertension, and cardiac dysrhythmias. Chronic accumulation of inhaled barium dust in the lung tissue may cause baritosis, a benign condition that may occur among barite ore miners. Chronic exposures to natural low levels of barium in drinking water have not produced general health effects or evidence of cardiovascular risk (Brenniman and Levy, 1984; Wones et al., 1990). Chronic high doses in animals resulted in kidney damage (McCauley et al., 1985; NTP 1994; Perry et al., 1989). Barium is not rated for human carcinogenicity.
Workplace standards for external air exposure to various barium salts have been established by OSHA, and a drinking water standard has been established by U.S. EPA. Information about external exposure (i.e., environmental levels) and health effects is available from ATSDR at https://www.atsdr.cdc.gov/toxprofiles/index.asp.
Levels of urinary barium reflect recent exposure. Studies reporting urinary levels of barium in general populations have found values generally similar to those reported in NHANES 1999-2010 (CDC, 2012; Minoia et al., 1990; Paschal et al., 1998). Barium levels determined in clinically submitted specimens were broadly comparable (Komaromy-Hiller et al., 2000) to levels in NHANES 1999-2000 and 2001-2002. Welders of barium-containing electrodes had median urinary levels of barium that were 60 times higher than median levels in the National Report on Human Exposure to Environmental Chemicals; the welders had no obvious adverse clinical effects (CDC, 2012; Zschiesche et al., 1992). Urinary concentrations in acute poisonings are often hundreds to thousands of times higher than in the U.S. population (CDC, 2012).
Finding a measurable amount of barium in urine does not imply that the level of barium causes an adverse health effect. Biomonitoring studies of levels of barium provide physicians and public health officials with reference values so that they can determine whether people have been exposed to higher levels of barium than are found in the general population. Biomonitoring data can also help scientists plan and conduct research on exposure and health effects.
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