TOXICOLOGICAL PROFILE FOR BARIUM AND COMPOUNDS ...

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2. HEALTH EFFECTS
evidence from human case studies, there is the potential that individuals
exposed to barium at hazards waste sites may be at increased risk for
developing neurological effects. Because of this potential for adverse
neurological effects and because the majority of the neurotoxicity database
consists primarily of uncontrolled human case studies involving acute oral
exposure, additional neurotoxicity data derived from controlled experimental
studies and involving various routes of exposure and exposure periods would be
useful.
Epidemiological and Human Dosimetry Studies. A limited number of
epidemiological and human dosimetry studies evaluating the health effects of
barium are available (Brenniman and Levy 1985; Brenniman et al. 1979a, 1979b,
1981; Elwood et al. 1974; Schroeder and Kraemer 1974; Wones et al. 1990).
However, all of the available human studies on barium have limitations and/or
confounding variables that make it difficult to draw firm conclusions
regarding the health effects of barium (see Sections 2.2.2.1 and 2.2.2.2 for
discussions on the specific limitations associated with available
epidemiological and human dosimetry studies). Two epidemiological studies
evaluated mortality and morbidity rates in communities having elevated barium
concentrations in drinking water and communities having little or no barium in
drinking water (Brenniman and Levy 1985; Brenniman et al. 1979a, 1979b, 1981).
Results suggested that relative to low-barium communities, elevated-barium
communities had significantly higher mortality rates for all cardiovascular
disease, heart disease, arteriosclerosis, and for all causes. No differences
between these types of communities were observed with respect to blood
pressure, hypertension, stroke, or electrocardiograms. Two statistical
studies found negative correlations between barium concentrations in drinking
water and rates of cardiovascular mortality and total mortality (Elwood et al.
1974; Schroeder and Kraemer 1974). Results of one human dosimetry study
involving a small number of subjects suggested that intermediate exposure to
barium in drinking water was not associated with clinically significant
changes in blood pressure, electrocardiograms, urinalyses, or hematological
parameters (Wones et al. 1990). It is noteworthy that the available
epidemiological and human dosimetry studies provide suggestive evidence that
barium has no effect on blood pressure. In contrast, results of case studies
of humans having acute ingestion exposure (Das and Singh 1970; Diengott et al.
1964; Gould et al. 1973; Wetherill et al. 1981) and experimental studies with
animals having intermediate and chronic oral exposure (Perry et al. 1983,
1985, 1989) indicate that barium induces hypertension and increased blood
pressure. Therefore, additional epidemiological and/or human dosimetry
studies would be useful to determine the effects of barium on blood pressure
and other cardiovascular parameters. However, these additional studies may
only be useful to the extent that they can control confounding variables and
limit study deficiencies that are problematic in currently available studies.
Since there are no data or very limited human data regarding the
developmental, reproductive, immunotoxic, neurotoxic, and carcinogenic effects