Concise International Chemical Assessment Document 33

Concise International Chemical Assessment Document 33

22

 Table 2: Toxicity of barium to selected aquatic organisms.

a

Organism

Static/

flow

b

Temperature

(°C)

pH

Hardness

(mg/litre)

Duration

LC

50

/EC

50

 

(mg/litre)

Reference

Water flea

(Daphnia magna)

(fresh water)

static

21–23

7.4–9.4

173

24 h

LC

50

 >530

LeBlanc (1980)

static

21–23

7.4–9.4

173

48 h 

LC

50

 410

(320–530)

7.4–8.2

44–53

48 h

LC

50

 14.5

Biesinger &

Christensen (1972)

7.4–8.2

44–53

21 days

LC

50

 13.5

c

(12.2–15.0)

static

11.5–14.5

7.2–7.8

235–260

24 h

EC

50

 52.8

d

Khangarot & Ray

(1989)

static

11.5–14.5

7.2–7.8

235–260

48 h

EC

50

 32.0

d

Crayfish (Orco-

nectes limosus)

(fresh water)

flow

15–17

7.0

96 h

LC

50

 78

Boutet & Chaisemartin

(1973)

flow

15–17

7.0

30 days

LC

50

 59

flow

15–17

7.0

30 days

LC

50

 61

c

Crayfish (Austro-

potamobius

pallipes pallipes)

(fresh water)

flow

15–17

7.0

96 h

LC

50

 46

flow

15–17

7.0

30 days

LC

50

 39

flow

15–17

7

30 days

LC

50

 43

c

Sheepshead

minnow (Cyprino-

don variegatus)

(marine water)

static

25–31

10–31

e

96 h

LC

50

 >500

Heitmuller et al. (1981)

a

Adapted from IPCS (1990).

b

static = static conditions (water unchanged for the duration of the test); flow = intermittent flow-through conditions.

c

 

Test conducted with a food source.

d

 

EC

50

 = concentration resulting in 50% immobilization.

e

 

Salinity (

0

/

00

).

weight was the most sensitive parameter measured and

showed a 50% reduction, relative to controls, at a barium

concentration of 41.2 mg/litre.

Barium sulfate is the principal constituent of

drilling muds used in oil drilling operations. These

muds also contain metals other than barium. No deaths

occurred in a number of unspecified marine fish,

crustaceans, and molluscs exposed to various levels (as

high as 7500 mg/kg) of drilling mud for an unspecified

period of time (Daugherty, 1951). Other studies reported

reduced populations of molluscs and/or annelids

exposed to barite in estuarine water, but it could not be

determined whether the results were due to larval

avoidance of barite or to barite toxicity (Tagatz & Tobia,

1978; Cantelmo et al., 1979).

10.2

Terrestrial environment

In general, barium has been shown to inhibit the

growth of bacteria, fungi, mosses, and algae (IPCS,

1990). Other relevant information was not identified.

11. EFFECTS EVALUATION

11.1

Evaluation of health effects

11.1.1

Hazard identification and dose–response

assessment

Barium enters the body primarily through the

inhalation and ingestion processes. The degree of

absorption of barium from the lungs and gastrointestinal

tract varies according to animal species, solubility of the

compound, and age of the animal. Studies in rats using a

soluble salt (barium chloride) have indicated that the

absorbed barium ions are distributed via the blood and

deposited primarily in the skeleton.

The principal route of elimination for barium

following oral, inhalation, or intratracheal administration

is in the faeces. Following introduction into the respira-

tory tract, the appearance of barium sulfate in the faeces

represents mucociliary clearance from the lungs and

subsequent ingestion.

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Barium and barium compounds

23

In humans, ingestion (accidental or intentional)

of barium compounds may cause gastroenteritis (vomit-

ing, diarrhoea, abdominal pain), hypopotassaemia,

hypertension, cardiac arrhythmias, and skeletal muscle

paralysis (IPCS, 1990; US EPA, 1990, 1998; ATSDR,

1992). The toxicity is dependent on the water solubility

of the barium compound; the lack of case reports of

systemic toxicity despite the routine oral administration

for many years of approximately 450 g barium sulfate as a

radiocontrast medium indicates that this practically

insoluble barium compound is not toxic by the oral route.

Due to its limited absorption by the dermal route,

systemic toxicity is not anticipated.

Medium- and long-term oral exposure animal

studies (McCauley et al., 1985; NTP, 1994) provide

evidence that the kidney is a sensitive target of barium

toxicity in rats and mice fed a nutritionally adequate diet.

Hypertension has been observed in studies in which rats

were fed a marginally adequate diet, particularly one with

inadequate calcium levels (Perry et al., 1983, 1985, 1989). 

Although limited due to the small population size

(2000) and lack of individual measurements of exposure,

longer-term human studies (Brenniman & Levy, 1984;

Wones et al., 1990) have not found adverse effects

following oral exposure to relatively low concentrations

of barium in drinking-water.

Inhalation of barium carbonate powder was

associated with hypopotassaemic paralysis in a male

worker (Shankle & Keane, 1988).

Several case reports (Pendergrass & Greening,

1953; Seaton et al., 1986) and a cross-sectional exami-

nation of workers at a barite grinding facility reported by

Doig (1976) indicated reversible baritosis in workers

exposed to airborne barite ore or barium sulfate. Upon

exposure termination, there was an apparent decrease in

barium levels in the lung (Doig, 1976); the barium-related

lesions were also potentially reversible (ACGIH, 1992). A

NIOSH (1982) survey indicated prevalence of

hypertension in workers exposed to an unspecified

concentration of barium; these results should be

interpreted cautiously, because it is likely that the

workers were also exposed to other metals, including

lead, which has a known hypertensive effect.

Data on the toxicity of inhaled barium to animals

are limited; studies have deficiencies that preclude their

usefulness for hazard identification or dose–response

assessment.

A reproductive/developmental toxicity study did

not find any significant alterations in reproductive end-

points or in gestation length, pup survival, or occurrence

of external abnormalities in rats and mice exposed to

barium chloride in drinking-water (Dietz et al., 1992). The

low pregnancy rates in all groups, including controls,

limit the usefulness of this study.

Oral exposure studies in rats and mice (Schroeder

& Mitchener, 1975a,b; McCauley et al., 1985; NTP, 1994)

did not find significant increases in tumour incidence

following long-term exposure. The design of the

McCauley et al. (1985) and Schroeder & Mitchener

(1975a,b) studies was inadequate for carcinogenicity

evaluation. In the McCauley et al. (1985) study, small

numbers of animals of one sex were exposed to relatively

low concentrations of barium chloride for less than a

lifetime. The absence of adverse effects suggests that

the maximum tolerated dose (MTD) may not have been

achieved in this study. In the Schroeder & Mitchener

(1975a) rat study, only the incidence of total gross

tumours was reported; the lack of adverse effects

suggests that the only dose used was lower than the

MTD. The decrease in longevity in the mouse study by

Schroeder & Mitchener (1975b) suggests that the MTD

may have been achieved in this study. However, it

appears that only two types of cancer were examined

(leukaemia and lung tumours).

The design of the rat and mouse NTP (1994) oral

studies was adequate to assess carcinogenicity. These

studies used an adequate number of animals per group,

exposed animals for 2 years, tested several dosage

levels, and examined an extensive number of tissues. The

decreased survival and histological alterations in the

kidneys of the mice and the increased kidney weights in

the rats suggest that the MTD was achieved in both of

these studies. No carcinogenic effects were observed in

either species. In fact, significant negative trends in the

incidence of leukaemia, adrenal tumours, and mammary

gland tumours were observed in the rats.

Available data indicate that barium salts would not

be expected to have genotoxic potential, and the weight

of evidence from in vitro studies is negative.

Topical and ocular applications of barium nitrate

caused skin and eye irritation in rabbits. Barium

hydroxide and barium oxide irritate the eye, skin, and

respiratory tract. Physicochemical properties of barium

sulfate and the lack of reports of skin or eye irritation in

humans despite its widespread use, particularly for X-ray

purposes, suggest that barium sulfate is not irritating or

corrosive to either skin or eyes. Similarly, there is a lack

of reports of either skin or respiratory tract sensitization,

suggesting that barium sulfate is not a sensitizer.

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