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BARIUM AND BARIUM COMPOUNDS
3. HEALTH EFFECTS
3.1
INTRODUCTION
The primary purpose of this chapter is to provide public health officials, physicians, toxicologists, and
other interested individuals and groups with an overall perspective on the toxicology of barium. It
contains descriptions and evaluations of toxicological studies and epidemiological investigations and
provides conclusions, where possible, on the relevance of toxicity and toxicokinetic data to public health.
A glossary and list of acronyms, abbreviations, and symbols can be found at the end of this profile.
When evaluating the health effects of barium compounds, it is important to keep in mind that different
barium compounds have different solubilities in water and body fluids and therefore serve as variable
sources of the Ba
2+
ion. The Ba
2+
ion and the soluble compounds of barium (notably chloride, nitrate, and
hydroxide) are generally highly toxic to humans and experimental animals. The insoluble barium
compounds (notably sulfate) are inefficient sources of the Ba
2+
ion and therefore are generally nontoxic.
Although barium carbonate is insoluble in water, barium ions would be released from ingested barium
carbonate in the acid milieu of the stomach. Throughout the following section (3.2), the health effects by
route of exposure of both soluble and insoluble barium compounds are discussed.
3.2
DISCUSSION OF HEALTH EFFECTS BY ROUTE OF EXPOSURE
To help public health professionals and others address the needs of persons living or working near
hazardous waste sites, the information in this section is organized first by route of exposure (inhalation,
oral, and dermal) and then by health effect (death, systemic, immunological, neurological, reproductive,
developmental, genotoxic, and carcinogenic effects). These data are discussed in terms of three exposure
periods: acute (14 days or less), intermediate (15–364 days), and chronic (365 days or more).
Levels of significant exposure for each route and duration are presented in tables and illustrated in
figures. The points in the figures showing no-observed-adverse-effect levels (NOAELs) or lowest
observed-adverse-effect levels (LOAELs) reflect the actual doses (levels of exposure) used in the studies.
LOAELs have been classified into "less serious" or "serious" effects. "Serious" effects are those that
evoke failure in a biological system and can lead to morbidity or mortality (e.g., acute respiratory distress
or death). "Less serious" effects are those that are not expected to cause significant dysfunction or death,
or those whose significance to the organism is not entirely clear. ATSDR acknowledges that a
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BARIUM AND BARIUM COMPOUNDS
3. HEALTH EFFECTS
considerable amount of judgment may be required in establishing whether an end point should be
classified as a NOAEL, "less serious" LOAEL, or "serious" LOAEL, and that in some cases, there will be
insufficient data to decide whether the effect is indicative of significant dysfunction. However, the
Agency has established guidelines and policies that are used to classify these end points. ATSDR
believes that there is sufficient merit in this approach to warrant an attempt at distinguishing between
"less serious" and "serious" effects. The distinction between "less serious" effects and "serious" effects is
considered to be important because it helps the users of the profiles to identify levels of exposure at which
major health effects start to appear. LOAELs or NOAELs should also help in determining whether or not
the effects vary with dose and/or duration, and place into perspective the possible significance of these
effects to human health.
The significance of the exposure levels shown in the Levels of Significant Exposure (LSE) tables and
figures may differ depending on the user's perspective. Public health officials and others concerned with
appropriate actions to take at hazardous waste sites may want information on levels of exposure
associated with more subtle effects in humans or animals (LOAELs) or exposure levels below which no
adverse effects (NOAELs) have been observed. Estimates of levels posing minimal risk to humans
(Minimal Risk Levels or MRLs) may be of interest to health professionals and citizens alike.
A User's Guide has been provided at the end of this profile (see Appendix B). This guide should aid in
the interpretation of the tables and figures for Levels of Significant Exposure and the MRLs.
3.2.1
Inhalation Exposure
Studies evaluating the effects of barium following acute, intermediate, and chronic inhalation exposure
are limited to several case reports of humans exposed occupationally (Doig 1976; Essing et al. 1976;
Seaton et al. 1986; Shankle and Keane 1988), an experimental exposure to barium in welding fumes
(Zschiesche et al. 1992), and three experimental studies with animals (Cullen et al. 2000; Hicks et al.
1986; Tarasenko et al. 1977). These case reports and animal studies are not adequate for firmly
establishing the health effects of barium by inhalation because of a number of significant study
limitations. The case reports are generally inadequate because data were available for a limited number
of exposed subjects and because exposure conditions (duration, frequency, dose) were not well
characterized (Doig 1976; Essing et al. 1976; Seaton et al. 1986; Shankle and Keane 1988). One of the
animal studies was limited in that apparently no control animals were used, an inhalation chamber
providing a controlled dose and environment was not used, and there was a lack of information regarding