TOXICOLOGICAL PROFILE FOR BARIUM AND COMPOUNDS ...

40
2. HEALTH EFFECTS
system were reported in an intermediate oral study with rats (Tardiff et al.
1980). The findings from human case reports suggest that humans having acute
oral or inhalation exposure to barium may develop musculoskeletal effects.
No data on musculoskeletal involvement in cases of barium exposure by
other than oral or inhalation modes have been reported for humans. In animals
receiving acute doses of barium compounds parenterally, both muscle twitching
and paralysis have been reported. Muscle twitching usually occurred within
minutes of injection with flaccid paralysis following (Roza and Berman 1971;
Schott and McArdle 1974). Parenteral administration is a very rare route of
barium exposure, but once barium has entered the bloodstream and has been
systemically distributed, it will have the same effects on the same organ.
Similar symptoms are expected to occur in humans acutely exposed to barium via
inhalation and oral routes.
Barium induced smooth muscle contractions in a variety of in vitro
mammalian systems (Antonio et al. 1973; Breuing et al. 1987; Clement 1981;
Ebeigbe and Aloamaka 1987; Ehara and Inazawa 1980; Karaki et al. 1967; Mishra
et al. 1988; Munch et al. 1980; Saeki et al. 1981; Saito et al. 1972; Slavicek
1972). Contraction appears to be calcium dependent (Antonio et al. 1973;
Breuing et al. 1987; Clement 1981; Karaki et al. 1967; Saito et al. 1972),
although the exact mechanism is unknown (Breuing et al. 1987; Clement 1981;
Mishra et al. 1988).
Hepatic Effects. No reliable human or animal data were available
regarding hepatic effects following inhalation or dermal exposure.
Degeneration of the liver following acute oral exposure to barium has been
noted in one human case report (McNally 1925). Increased liver/brain weight
ratio and darkened liver were observed in rats following acute oral exposure
to barium (Borzelleca et al. 1988). Decrease blood urea nitrogen, a potential
sign of altered hepatic activity, was also noted in this study (Borzelleca et
al. 1988). The available data are too limited to conclusively determine
whether or not oral exposure to barium is associated with increased risk of
hepatic effects in humans.
Renal Effects. No dermal studies evaluating renal effects in humans or
animals were available. Renal failure was reported in one case study of a
human exposed by acute inhalation to barium (Shankle and Keane 1988). Case
studies of humans developing renal failure, renal insufficiency, and renal
degeneration following acute oral barium poisoning have been reported (Gould
et al. 1973; Lewi and Bar-Khayim 1964; McNally 1925; Phelan et al. 1984;
Wetherill et al. 1981). Increased kidney/body weight ratio has been observed
in rats following acute oral exposure to barium (Borzelleca et al. 1988).
Renal effects have not been observed in intermediate or chronic oral studies
with rats (Schroeder and Mitchener 1975a; Tardiff et al. 1980). Together, the
findings from human case reports and animal studies suggest that individuals
exposed to barium by acute inhalation or ingestion may be at increased risk of
developing minor renal effects.