Toxicological profile for barium and barium compounds

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3.  HEALTH EFFECTS 

control pup body weights.  A decrease in litter size was also observed, although the difference was not 

statistically significant (Dietz et al. 1992).  No developmental effects were observed in the offspring of 

mice exposed to barium chloride prior to mating (Dietz et al. 1992).  Reduced survival and decreased 

body weight were observed in the offspring of rats exposed to barium carbonate dust (Tarasenko et al. 

1977); however, poor reporting of the study methods and results limits the interpretation of the Tarasenko 

et al. (1977) study. 

There are some data suggesting possible age-related differences in toxicokinetic properties of barium.  A 

higher rate (about 10 times higher) of absorption was found in younger rats compared to older rats 

(Taylor et al. 1962).  A study of cadmium and mercury also found higher permeability in the jejunum of 

immature rats as compared to mature animals (Foulkes and Bergman 1993).  An unpublished study by 

Della Rosa summarized by ICRP (1993) found higher barium retention in dogs aged 43 (2.3% retained) 

or 150 (2.0%) days, compared to dogs aged 250 days (0.8%) or adult dogs (0.4–0.6%).  Information on 

biomarkers, interactions, and methods for reducing toxic effects of barium (discussed in Sections 3.8, 

3.10, and 3.11) comes from studies in adults and mature animals; no child-specific information was 

identified.  In the absence of data to the contrary, it is assumed that this information will also be 

applicable to children. 

3.8 

BIOMARKERS OF EXPOSURE AND EFFECT 

Biomarkers are broadly defined as indicators signaling events in biologic systems or samples.  They have 

been classified as markers of exposure, markers of effect, and markers of susceptibility (NAS/NRC 

1989). 

Due to a nascent understanding of the use and interpretation of biomarkers, implementation of biomarkers 

as tools of exposure in the general population is very limited.  A biomarker of exposure is a xenobiotic 

substance or its metabolite(s) or the product of an interaction between a xenobiotic agent and some target 

molecule(s) or cell(s) that is measured within a compartment of an organism (NAS/NRC 1989).  The 

preferred biomarkers of exposure are generally the substance itself, substance-specific metabolites in 

readily obtainable body fluid(s), or excreta.  However, several factors can confound the use and 

interpretation of biomarkers of exposure.  The body burden of a substance may be the result of exposures 

from more than one source.  The substance being measured may be a metabolite of another xenobiotic 

substance (e.g., high urinary levels of phenol can result from exposure to several different aromatic 

compounds).  Depending on the properties of the substance (e.g., biologic half-life) and environmental 

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3.  HEALTH EFFECTS 

conditions (e.g., duration and route of exposure), the substance and all of its metabolites may have left the 

body by the time samples can be taken.  It may be difficult to identify individuals exposed to hazardous 

substances that are commonly found in body tissues and fluids (e.g., essential mineral nutrients such as 

copper, zinc, and selenium).  Biomarkers of exposure to barium are discussed in Section 3.8.1. 

Biomarkers of effect are defined as any measurable biochemical, physiologic, or other alteration within an 

organism that, depending on magnitude, can be recognized as an established or potential health 

impairment or disease (NAS/NRC 1989).  This definition encompasses biochemical or cellular signals of 

tissue dysfunction (e.g., increased liver enzyme activity or pathologic changes in female genital epithelial 

cells), as well as physiologic signs of dysfunction such as increased blood pressure or decreased lung 

capacity.  Note that these markers are not often substance specific.  They also may not be directly 

adverse, but can indicate potential health impairment (e.g., DNA adducts).  Biomarkers of effects caused 

by barium are discussed in Section 3.8.2. 

A biomarker of susceptibility is an indicator of an inherent or acquired limitation of an organism's ability 

to respond to the challenge of exposure to a specific xenobiotic substance.  It can be an intrinsic genetic or 

other characteristic or a preexisting disease that results in an increase in absorbed dose, a decrease in the 

biologically effective dose, or a target tissue response.  If biomarkers of susceptibility exist, they are 

discussed in Section 3.10, Populations That Are Unusually Susceptible. 

At present, there are no well-established biomarkers of exposure and effect for barium.  Data suggesting 

possible biomarkers are presented below. 

3.8.1 

Biomarkers Used to Identify or Quantify Exposure to Barium  

Barium can be measured in bone, blood, urine, and feces.  It has been shown to be sequestered in bone 

and teeth and excreted in feces and urine.  Background levels of barium in bone are approximately 2 μg/g 

wet weight (ICRP 1974; Schroeder et al. 1972).  Background levels of barium in blood, urine, and feces 

will vary with daily intake of barium.  However, the following levels have been reported:  bone, 2 ppm 

(ICRP 1974; Schroeder et al. 1972); feces, 690–1,215 μg/day (ICRP 1974; Schroeder et al. 1972; Tipton 

et al. 1969); and urine, 17–50 μg/day (ICRP 1974; Schroeder et al. 1972; Tipton et al. 1969).  In the 

United States, the geometric mean concentration of barium in the urine is approximately 1.5 µg/L (CDC 

2005).  There are no data correlating bone, blood, urine, or feces levels of barium with specific exposure 

levels.  For more detailed information on the toxicokinetics of barium, see Section 3.4. 

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