Barium and barium compounds
21
compared with results for 25 workers who stated that
they had never worked in barium process areas. No
statistically significant differences in mean age, number
of years employed, number of current or past smokers,
prevalence of subjective symptoms, mean FEP levels,
mean haematocrit levels, mean urine cadmium levels,
mean
$
-2-microglobulin levels, or the prevalence of
workers with elevated serum creatinine, BUN, or urine
protein levels were observed between the two groups.
The number of workers with elevated blood pressure
(defined as systolic pressure >140 mmHg [>18.7 kPa] or
diastolic pressure >90 mmHg [>12 kPa] or taking
medication for hypertension) was significantly higher in
the barium-exposed group than in the comparison group.
The number of workers in the barium group with blood
lead levels of >39 mg/dl was lower than in the
comparison group; however, the difference was not
statistically significant. Additionally, there was no sig-
nificant difference between mean blood lead levels in the
barium-exposed workers (24 mg/dl) and the comparison
group (32 mg/dl).
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 was divided into three
groups: group A (n = 8, mean age 30.4 years) performed
arc welding with barium-containing stick electrodes,
group B (n = 5, mean age 43.6 years) performed arc
welding with barium-containing self-shielded flux-cored
wires, and group C (n = 5, mean age 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 h/day. The average barium concentrations
in the breathing zones were 4.4 (range 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 adverse
health symptoms or neurological signs were found. No
significant differences between pre- and post-shift
electrocardiogram, pulse rate, whole-blood pH, base
excess and standard bicarbonate, or plasma concen-
trations 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 barium
exposure level similar to that of group A.
10. EFFECTS ON OTHER ORGANISMS IN
THE LABORATORY AND FIELD
10.1
Aquatic environment
Toxicity of barium to selected aquatic organisms is
summarized in Table 2. A 48-h no-observed-effect level
(NOEL) of 68 mg/litre was calculated for water fleas
(Daphnia magna) exposed to various concentrations of
barium (LeBlanc, 1980). In contrast, Biesinger &
Christensen (1972) reported 48-h and 21-day LC
50
values
of 14.5 and 13.5 mg/litre, respectively, a 16% impairment
of reproduction at 5.8 mg/litre, and a 50% impairment at
8.9 mg/litre during the 21-day tests. Khangarot & Ray
(1989) reported 24- and 48-h EC
50
(the concentration
resulting in 50% immobilization) values of 52.8 and 32.0
mg/litre, respectively, for daphnids exposed to barium
sulfate. A reported 48-h EC
50
value for developmental
effects in the mussel
Mytilus californianus was 0.189
mg/litre (Spangenberg & Cherr, 1996). For two aquatic
amphipod species (Gammarus pulex and
Echinogammarus berilloni), Vincent et al. (1986)
reported 24-, 48-, 72-, and 96-h LC
50
values of 3980, 395,
255, and 238 mg/litre and 336, 258, 162, and 122 mg/litre,
respectively, in eucalcic water; LC
50
values in oligocalcic
water were 1260, 533, 337, and 227 mg/litre and 308, 197,
151, and 129 mg/litre, respectively. The 30-day LC
50
values for two species of crayfish ranged from 39 to 61
mg/litre; the 96-h values were comparable (Boutet &
Chaisemartin, 1973). Heitmuller et al. (1981) reported a
NOEL in the sheepshead minnow (Cyprinodon
variegatus) of 500 mg/litre.
Growth of Anacystis nidulans (a cyanobacterium)
in an environment containing 50 mg barium chloride/litre
was similar to that of controls. Higher concentrations of
barium resulted in a concentration-related increase in
growth inhibition; almost complete inhibition was
reported at barium chloride concentrations
$
750 mg/litre
(Lee & Lustigman, 1996). Wang (1986) reported a 96-h
EC
50
(growth) of 26 mg barium/litre in duckweed (
Lemna
minor) in deionized water. However, in river water,
barium showed no toxic effect on growth of duckweed.
The lack of an adverse effect in the river water was
shown to be due to precipitation of barium from the river
water as sulfate. Stanley (1974) investigated the toxic
effects of barium on the growth of Eurasian watermilfoil
(Myriophyllum spicatum). Root