Toxicological profile for barium and barium compounds

60 

BARIUM AND BARIUM COMPOUNDS 

3.  HEALTH EFFECTS 

Table 3-2.  Genotoxicity of Barium and Barium Compounds In Vitro 

Species (test system)  End point 

Results  Reference 

Compound 

Prokaryotic organisms: 

Salmonella typhimurium

 

Gene mutation 

– 

Monaco et al. 1990, 

Barium chloride 

frequency 

1991; NTP 1994 

(with or without S9 

activation) 

Escherichia coli 

Gene mutation 

– 

Rossman et al. 1991 

Barium chloride 

WP2s(

λ

) 

frequency 

Bacillus subtilis 

DNA damage 

– 

Kanematsu et al. 1980; 

Barium chloride, 

(rec assay) 

Nishioka 1975 

barium nitrate 

Eukaryotic organisms: 

Fungi 

Saccharomyces 

Meiosis  

– 

Sora et al. 1986 

Barium chloride 

cerevesiae 

Avian myeloblastosis 

DNA synthesis 

– 

Sirover and Loeb 1976a,  Barium chloride, 

virus DNA polymerase  

1976b 

barium acetate 

 Mammalian cells: 

CHO cells 

Sister chromatid 

– 

NTP 1994 

Barium chloride 

exchange 

(with or without S9 

activation) 

CHO cells 

Chromosome 

– 

NTP 1994 

Barium chloride 

aberration 

(with or without S9 

activation) 

Mouse lymphoma cells 

Gene mutation at TK 

NTP 1994 

Barium chloride 

locus  

With S9 activation 

+ 

Without S9 activation  – 

– = negative result; + = positive result; CHO = Chinese hamster ovary 

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BARIUM AND BARIUM COMPOUNDS 

3.  HEALTH EFFECTS 

3.4 

TOXICOKINETICS 

3.4.1 

Absorption 

3.4.1.1  Inhalation Exposure 

No studies were located regarding absorption of barium in humans following inhalation exposure.  

Several animal studies have investigated the absorption of barium chloride or barium sulfate following 

inhalation, intratracheal injection, or nasal deposition.  The results of these studies suggest that the rate 

and extent of absorption of barium from the respiratory tract depend on the exposure level, how much 

barium reaches the alveolar spaces, the clearance rate from the upper respiratory tract, and the solubility 

of the particular form of barium that was administered.  Approximately 50–75% of inhaled barium 

chloride or barium sulfate is absorbed from the respiratory tract (Cuddihy and Griffith 1972; Morrow et 

al. 1968); approximately 65% of the barium chloride deposited in the nose is absorbed (Cuddihy and 

Ozog 1973b).  Most of the barium absorption occurs within the first 24 hours (Cuddihy and Griffith 1972; 

Cuddihy et al. 1974).  Barium chloride appears to be more rapidly absorbed than barium sulfate (Cuddihy 

et al. 1974), although the differences in particle size (AMADs of 2.3 and 1.0 µm for barium chloride and 

barium sulfate, respectively) may have influenced the absorption rate.  In contrast to the rapid absorption 

of barium following inhalation or nasal deposition, most of the barium sulfate that is injected directly into 

the trachea of rats can be taken up into the epithelium membranes and remains in these membranes for at 

least a few weeks (Gore and Patrick 1982; Takahashi and Patrick 1987), suggesting that clearance in the 

upper respiratory tract is more efficient than in the trachea.  Following intratracheal injection, the 

clearance of barium sulfate from the lungs was independent of lung burden over the range of 23.3– 

2,330 µg (Cember et al. 1961); this is consistent with the lack of evidence of lung overload following 

intermediate-duration inhalation exposure to 37.5 or 75 mg/m

3

 barium sulfate (MMAD 4.3 µm, σg 1.7) 

(Cullen et al. 2000).  Species differences in the retention of intratracheally administered radiolabelled 

(

133

Ba) barium sulfate have been found.  The percentages of 

133

Ba retained in the trachea 1 week after 

administration were 0.41, 0.145, 0.044, and 0.043% in rats, rabbits, dogs, and monkeys, respectively 

(Takahashi and Patrick 1987; Takahashi et al. 1993). 

3.4.1.2  Oral Exposure  

The absorption of barium from the gastrointestinal tract is compound dependent.  Barium sulfate is 

extremely insoluble and very little, if any, ingested barium sulfate is absorbed.  Acid-soluble barium 

compounds, such as barium chloride and barium carbonate, are absorbed through the gastrointestinal 

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BARIUM AND BARIUM COMPOUNDS 

3.  HEALTH EFFECTS 

tract, although the amount of barium absorbed is highly variable.  Older human studies estimated that 

barium was poorly absorbed; approximately 1–15% of the ingested dose was estimated to be absorbed 

(Harrision et al. 1956; LeRoy et al. 1966; Schroeder et al. 1972; Tipton et al. 1969).  A re-examination of 

the methods used in these studies found a number of flaws; Leggett (1992) estimated that barium 

absorption in these studies was approximately 3–60%.  Studies in adult rats and dogs estimated fractional 

absorption at 7% (Cuddihy and Griffith 1972; Taylor et al. 1962).  Several unpublished animal studies 

discussed by Leggett (1992) found absorption rates of 1–50%.  Experiments in rats have shown that 

younger animals (22 days old or less) absorb about 10 times more barium chloride from the 

gastrointestinal tract (63–84%) than do older animals (about 7%) (Taylor et al. 1962).  Absorption was 

higher in fasted adult rats (20%) as compared to fed rats (7%).  The International Commission for 

Radiation Protection (ICRP) estimates that the gastrointestinal absorption of barium is 20% in adults, 

30% for children aged 1–15 years, and 60% in infants (ICRP 1993). 

3.4.1.3  Dermal Exposure  

No studies were located regarding absorption of barium in humans after dermal exposure.  One animal 

study showed that barium applied to the skin of piglets was found in the various layers of the skin 

(Shvydko et al. 1971).  Barium is not expected to cross the intact skin because of the high polarity of the 

forms in which it is most commonly encountered. 

3.4.2 

Distribution  

3.4.2.1  Inhalation Exposure 

Shortly after dogs were exposed to radiolabelled (

140

Ba) barium chloride, elevated activity was found in 

the upper respiratory tract, stomach, and small intestine (30% of initial burden), lungs and 

tracheobronchial tissue (6%), and various internal organs (64%) (Cuddihy and Griffith 1972).  One day 

post-exposure, 44% of the label was detected in the skeleton, 1% in blood, and 4% in muscle; 26% of the 

dose was excreted.   

3.4.2.2  Oral Exposure  

In humans, barium is predominantly found in bone; approximately 90% of the barium in the body was 

detected in the bone (Schroeder et al. 1972).  Approximately 1–2% of the total body burden was found in 

muscle, adipose, skin, and connective tissue.  This information is supported by a number of studies 

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