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Dallas and Williams (2001) have provided an overview of studies that investigated the effects of Ba-administration to mammals. The majority of cited studies addressed the effects of Ba on the cardiovascular toxicity or on kidneys (Borzelleca et al, 1988; Brenniman and Levy, 1984; Kopp et al, 1985; McCauley et al, 1985; NTP, 1994; Perry et al, 1983,1989; Schroeder and Mitchener, 1975a,b; Tardiff et al, 1980; Wones et al, 1990).

With regard to subchronic and chronic exposure studies with barium, the NTP (1994) study is considered as the best documented animal toxicity study available. Here, Ba chloride dihydrate was administered in drinking water to individual groups of male and female F344/N rats and B6C3F1 mice for 15d, 13wk, and for 2 year.

The main findings of the long-term exposures (13 wk, 2 yr) are summarized hereunder:

-  I3 wk study: It was concluded from the neurobehavioural data that there were no consistent effects on behaviour produced by Ba exposure. The No-observed-adverse-effect-level (NOAEL) for this subchronic study was considered to be 2000 ppm Ba chloride dihydrate; this corresponds to 110 mg Ba/kg/d for male rats, 115 mg Ba/kg/d for female rats, 205 mg Ba/kg/d for male mice, and 200 mg Ba/kg/d for female mice. These data were also reported by Dietz et al (1992).

- 13 wk study: Death in mice in the highest dose groups (450 mg Ba/kg/d for males and 495 mg Ba/kg/d for females) were associated with renal toxicity. Renal lesions in rats were much less severe at the highest dose level (200 mg Ba/kg/d for males and 180 mg Ba/kg/d for females).

- In the 2yr study, the evaluated endpoints were hematology values and increases in neoplasms; the conclusion was “no increased incidences of neoplasms or nonneoplastic lesions that could be attributed to BaCl2 dihydrate” for rats receiving average dose rates of 60 (male) and 75 (female) mg/kg/d.

- For mice (endpoints were kidneys, nephropathy, renal tubule regeneration, lymphoid depletions) the identified NOAEL was 75 mg Ba/kg/d for males, and 90 mg Ba/kg/d for females. 

Dietz et al (1992) also reported on reproductive effects of Ba: a 13 wk reproduction study based on Ba ingestion via drinking water was conducted with mice and rats.  The results of this study indicated that subchronic oral exposure to Ba chloride doses up to about 200 mg Ba/kg/d did not affect reproductive indices (anatomical effects on offspring, epididymal sperm counts, sperm motility and morphology, testes/epididymal weight, vaginal cytology). It should be noted, however, that in all groups of rats or mice a below-normal pregnancy rate was observed. As this below-normal rate was also noted in the control (40%; rati at highest dose of 4000 ppm was 65%), this low rates are not caused due to Ba-exposure