TOXICOLOGICAL PROFILE FOR BARIUM AND COMPOUNDS ...

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2. HEALTH EFFECTS
exposure studies, additional acute oral studies that focus on mechanisms of
toxicity useful.and that further establish and/or refine effect thresholds would be
Additional studies of barium following inhalation and dermal exposure
would be useful because the potential adverse effects of these two routes have
not been thoroughly studied. This information is important because
populations exposed to barium from hazardous waste sites may be exposed for a
similar duration.
Intermediate-Duration Exposure. The majority of available intermediate-duration
studies have focused on oral exposure of experimental animals (McCauley et al. 1985;
Perry et al. 1983, 1985, 1989; Tarasenko et al. 1977; Tardiff et al. 1980). Several
intermediate oral studies with rats have evaluated mortality and systemic effects
(McCauley et al. 1985; Tardiff et al. 1980). Systemic effects were evaluated by
monitoring body weight, selected organ weights, food consumption, clinical signs of
toxicity, and a variety of hematological and blood chemistry parameters, and by
performing gross and microscopic examinations on a wide variety of organs and
tissues. Generally, no toxicologically significant adverse effects were noted in any
of these parameters. Other intermediate oral studies (Perry et al. 1983, 1985, 1989)
have provided evidence that barium induces increased blood pressure. The
mechanism of action of this cardiovascular effect has not been established.
Various renal lesions have been observed in two intermediate oral experiments
with rats (McCauley et al. 1985); however, these studies were of limited value
because control rats were not used. Nonsignificant increases in retinal
dystrophy have been observed in several intermediate oral experiments with
rats (McCauley et al. 1985). It is particularly noteworthy that when these
various experiments are combined, a dose-related increase in this ocular
lesion is observed. No intermediate dermal studies were available. In the
only available intermediate inhalation study (Tarasenko et al. 1977), barium
exposure was associated in rats with decreased body weight, altered
hematological and blood chemistry parameters, impaired hepatic detoxifying
function, and pulmonary lesions. However, this study was of limited value
because the number of rats evaluated was not specified. Given the available
data, additional intermediate oral studies focusing on the association between
barium exposure and hypertension in animals ingesting a normal diet, the
mechanism by which barium increases blood pressure, and the potential of
barium to induce renal lesions, ocular lesions and various cardiovascular
effects would be useful. Because the potential adverse effects of barium
following inhalation exposure have not been well characterized and dermal
exposure have not been studied, additional intermediate-duration exposure
studies involving these two routes of exposure would also be useful. This
information is important because there are populations surrounding hazardous
waste sites that may be exposed to barium for an intermediate duration.
Chronic-Duration Exposure and Cancer. Chronic studies in which rats and
mice were exposed to barium in drinking water for lifetime have evaluated both
mortality and systemic effects (Schroeder and Mitchener 1975a, 1975b).