BARIUM IN DRINKING-WATER - Who/sde/wsh/03. 04/76
BARIUM IN DRINKING-WATER
concentrations in municipal drinking-water derived from groundwater were reportedto be between 700 and 1160 µg/litre (Lanciotti et al., 1992). In the Cambrian-Vendian
aquifer in Estonia, which is low in sulfate, barium concentrations ranged from 0.07 to
6.37 mg/litre, with a median value of 0.8 mg/litre. However, there was a significant
variation in concentration over the aquifer; in one anomalous area, the median
concentration was 2.41 mg/litre (A. Marandi, personal communication, 2003).
If an average daily water consumption of 2 litres is assumed, intake from drinking-water will range from about 2 to 1200 µg. The great majority of intakes will be below
200 µg, and most will be below 100 µg.
Most foods contain less than 0.002 mg of barium per g (Gormican, 1970). Somecereal products and nuts may contain high levels: e.g., bran flakes, 0.0039 mg/g;
pecans, 0.0067 mg/g; and Brazil nuts, up to 4 mg/g (Mertz, 1986).
The long-term mean dietary barium intake for adults has been found to be 0.75mg/day (range 0.44–1.8 mg/day), including food and fluids (ICRP, 1975); 0.6 mg/day
from total diet (IPCS, 1990); and 1.24 mg/day (range 0.65–1.8 mg/day) for food only
(Schroeder et al., 1972).
Barium sulfate is the major barium compound used medicinally. Often called abarium “meal,” this very poorly soluble compound is employed as an opaque contrast
medium for X-ray studies of the gastrointestinal tract.
3.4 Estimated total exposure and relative contribution of drinking-water
On the basis of the above considerations, the mean daily intake of barium from food,
water and air is estimated to be slightly more than 1 mg/day, food being the primary
source for the non-occupationally exposed population. However, where barium levels
in water are high, drinking-water may contribute significantly to barium intake.
4. KINETICS AND METABOLISM IN LABORATORY ANIMALS AND
Soluble barium salts are most readily absorbed, although insoluble compounds mayalso be absorbed to a significant extent (McCauley & Washington, 1983; Clavel et al.,
1987). The degree of absorption of barium from the gastrointestinal tract also depends
on the animal species, the contents of the gastrointestinal tract, diet and age (Taylor et
al., 1962; McCauley & Washington, 1983; Clavel et al., 1987). Data on
gastrointestinal absorption in humans are limited to a study conducted by Lisk et al.
(1988); in this mass balance study of one man consuming a single dose of 179.2 mg
of barium in 92 g of Brazil nuts, it was estimated that at least 91% of the dose was
absorbed (List et al., 1988; US EPA, 1999).
BARIUM IN DRINKING-WATER
Barium is rapidly transported in blood plasma, principally to bone (US NRC, 1977).
Approximately 91% of the total body burden of barium is in the bone (IPCS, 1990).
Elevated barium/calcium ratios were found in the teeth of children exposed to
drinking-water containing 10 mg of barium per litre (Miller et al., 1985). It has been
reported that barium crosses the placental barrier in humans (Schroeder et al., 1972).
The faecal route of excretion of barium is the most important in humans and animals(Ohanian & Lappenbusch, 1983); in humans, 20% of an ingested dose is excreted in
the faeces and 7% in the urine within 24 h (US NRC, 1977; IPCS, 1990).
5. EFFECTS ON LABORATORY ANIMALS AND IN VITRO TEST SYSTEMS
5.1 Acute exposure
Acute oral LD
values in rats for barium chloride, barium carbonate and bariumsulfide range from 118 to 800 mg/kg of body weight (NIOSH, 1989; IPCS, 1990;
5.2 Short-term exposure
No effects on blood pressure were seen in Sprague-Dawley rats exposed to 100 mg of
barium per litre as barium chloride in drinking-water (equivalent to 1.5 mg/kg of body
weight per day) for up to 20 weeks (McCauley et al., 1985). In the same series of
studies, no changes were seen in blood pressure in hypertension-susceptible Dahl and
uninephrectomized rats exposed for 16 weeks to up to 1000 mg of barium per litre in
distilled water or 0.9% saline. At 1000 mg/litre, however, ultrastructural changes in
the glomeruli of the kidney were discernible by electron microscopy. In addition, no
significant electrocardiographic changes during (-)-norepinephrine challenge were
observed in Sprague-Dawley rats ingesting drinking-water containing 250 mg of
barium per litre for 5 months (McCauley et al., 1985).
Groups of 10 male and 10 female mice were administered barium chloride dihydratein drinking-water for 13 weeks at concentrations of 0, 125, 500, 1000, 2000 or 4000
mg/litre for 13 weeks, corresponding to average daily doses of 0, 15, 55, 100, 205 and
450 mg of barium per kg of body weight in males and 0, 15, 60, 110, 200 and 495 mg
of barium per kg of body weight in females. Complete histopathological examinations
were performed on all mice in the control, 2000 mg/litre and 4000 mg/litre groups,
and histopathological examinations of the kidneys were performed on the male mice
in the 1000 mg/litre group. Cardiovascular studies and haematological and serum
electrolyte analyses were not performed on the mice. A NOAEL of 2000 mg/litre was
derived based on significant mortality at the 4000 mg/litre dose and on the incidence
of chemical-related nephropathy. Although decreased absolute and relative liver
weights were observed at the 1000, 2000 and 4000 mg/litre doses in females, no
histopathological effects on the liver were observed at any dose level, and so the
effect was deemed to be non-adverse (US NTP, 1994).
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