Toxicological Review of Barium and Compounds

the barium-exposed workers (24 

:

g/dL) and the comparison group (32 

:

g/dL).  Although the 

results of this study suggest an association between exposure to barium and hypertension, the 

results should be interpreted cautiously because (1) a small number of workers were examined, 

(2) it appears that blood pressure was measured only once, and (3) the workers were exposed to a 

number of other chemicals, including lead, which is associated with an increase in blood 

pressure. 

The health effects associated with occupational exposure to barium during arc welding 

with barium-containing stick electrodes and flux-cored wires were investigated by Zschiesche et 

al. (1992).  A group of 18 healthy welders not using barium-containing consumables in the past 

10 days were divided into three groups:  group A (n = 8, mean age of 30.4 years) performed arc 

welding with barium-containing stick electrodes, group B (n = 5, mean age of 43.6 years) 

performed arc welding with barium-containing self-shielded flux-cored wires, and group C (n = 

5, mean age of 32.0 years) performed arc welding with barium-containing self-shielded flux-

cored wires using welding guns with built-in ventilation systems.  All welders performed 

welding with barium-free consumables on Thursday and Friday of the first week of the study. 

Barium-containing consumables were used during week 2 of the study and on Monday of week 

3.  The subjects welded for an average of 4 hours per day.  The average barium concentrations in 

the breathing zones were 4.4 (range of 0.1-22.7), 2.0 (0.3-6.0), and 0.3 (0.1-1.5) mg/m

3

 for 

groups A, B, and C, respectively.  No exposure-related subjective symptoms of health or 

neurological signs were found.  No significant differences between pre- and post-shift EKG, 

pulse rate, whole blood pH, base excess and standard bicarbonate, and plasma concentrations of 

sodium, magnesium, and total and ionized calcium were observed.  During week 2, decreases in 

plasma potassium concentrations were observed in groups A and C; the levels returned to the 

normal range under continuation of barium exposure and were not statistically different from 

levels during week 1 (no barium exposure).  This drop in serum potassium levels was not 

observed in group B, which had a similar barium exposure level as group A. 

4.2.  PRECHRONIC/CHRONIC STUDIES AND CANCER BIOASSAYS IN 

ANIMALS—ORAL AND INHALATION 

4.2.1.  Oral Studies 

The National Toxicology Program (NTP) conducted a series of toxicity and 

carcinogenicity studies with barium chloride dihydrate (BaCl

2

×2H

2

O).  The chemical was 

15

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administered in drinking water to mice and rats for 13 weeks or 2 years (NTP, 1994).  A 

preliminary report of the 13-week subchronic studies was published by Dietz et al. (1992). 

4.2.1.1.  NTP (1994) Subchronic Mouse Study 

In subchronic mouse studies, male and female B6C3F1 mice (10 animals/group/sex) 

received BaCl

2

×2H

2

O in their drinking water at concentrations of 0, 125, 500, 1000, 2000, and 

4000 ppm for 13 weeks.  Using weekly water consumption and body weight data, the authors 

estimated the doses of barium were 15, 55, 100, 205, and 450 mg/kg-day for the males and 15, 

60, 110, 200, and 495 mg/kg-day for the females, respectively.  The animals were fed NIH-07 

pellets.  Barium concentration of the diet was not reported.  Complete histopathologic 

examinations were performed on all mice in the control, 2000 ppm, and 4000 ppm treatment 

groups, and histopathologic examinations of the kidneys were performed on the male mice in the 

1000 ppm treatment group.  Organ and body weights were measured and neurobehavioral 

assessments (at 0, 45, and 90 days) were performed on animals of all groups.  Hematology and 

clinical chemistry analyses were not performed. 

In the 4000 ppm treatment group, 6/10 male and 7/10 female mice died; survivors were 

debilitated.  In the 125 ppm treatment group, one of the ten male mice died.  No mortalities were 

observed in any of the other treatment groups.  Water consumption for the male mice in the 4000 

ppm treatment group was 18% lower than that of controls.  In all other treatment groups water 

consumption was similar to that of controls.  In the 4000 ppm treatment group, body weights of 

both sexes were significantly reduced, with final body weights 30%-50% lower than those for 

controls.  Absolute kidney weights were decreased 23%, relative kidney weights increased 12% 

in the males, while in the females absolute kidney weights were decreased 21%, but relative 

kidney weights were increased 40%.  Absolute and relative thymus weights were decreased in 

both sexes.  Decreased absolute and relative liver weights were seen in animals receiving 

drinking water concentrations of 1000 ppm BaCl

2

×2H

2

O or greater.  Relative liver weights were 

decreased by 25% in males receiving 4000 ppm, but only 10% in females, when compared to 

controls. 

Chemical-related nephropathy occurred in 10/10 male and 9/10 female mice in the 4000 

ppm treatment group.  The lesions were characterized by tubule dilatation, renal tubule atrophy, 

tubule cell regeneration, and the presence of crystals primarily in the lumen of the renal tubules. 

Atrophy of the thymus and spleen was observed in a significant number of males and females 

that received 4000 ppm.  NTP (1994) described the thymic lesions as necrotic or moderate to 

marked depletion of thymic lymphocytes.  In some cases, only remnants of stromal cells were 

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