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Barium and barium compounds

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Barium and barium compounds

9

during a single summer sampling event, and the authors

advise caution in extrapolating the results to terrestrial

systems in general.

There is no evidence that barium undergoes envi-

ronmental biotransformation other than as a divalent

cation (IPCS, 1990).

6. ENVIRONMENTAL LEVELS AND

HUMAN EXPOSURE

6.1

Environmental levels

The levels of barium in air are not well docu-

mented, and in some cases the results are contradictory.

Tabor & Warren (1958) detected barium concentrations

ranging from <0.005 to 1.5 mg/m

3

 in the air in 18 cities

and 4 suburban areas in the USA. No distinct pattern

between ambient levels of barium in the air and the

extent of industrialization was observed. In general,

however, higher concentrations were observed in areas

where metal smelting occurred (Tabor & Warren, 1958;

Schroeder, 1970). In a more recent survey in the USA,

ambient barium concentrations ranged from 0.0015 to

0.95 mg/m

3

 (US EPA, 1984). In three communities in New

York City, USA, barium was measured in dust fall and

household dust (Creason et al., 1975). With standard

methods (US EPA, 1974), the dust fall was found to

contain an average of 137 mg barium/g, while the house

dust contained 20 mg barium/g.

Barium is found in almost all surface waters that

have been examined (NAS, 1977). The concentrations are

extremely variable and depend on local geology, water

treatment, and water hardness (NAS, 1977). Barium

concentrations of 7–15 mg/litre and 6 mg/litre have been

measured in fresh water and seawater, respectively

(Schroeder et al., 1972). The mean barium content of

various US surface waters ranges from 43 to 57 mg/litre

(Durum, 1960; Kopp, 1969; Kopp & Kroner, 1970;

Schroeder, 1970; Bradford, 1971). The concentrations of

barium in sediments of the Iowa River, USA, were

measured to be 450–3000 mg/kg (Tsai et al., 1978),

suggesting that barium in the water is removed by

precipitation and silting.

Studies of drinking-water quality in cities in the

USA have revealed levels of barium ranging from trace

to 10 mg/litre (Durfor & Becker, 1964; Barnett et al., 1969;

McCabe et al., 1970; McCabe, 1974; Calabrese, 1977;

AWWA, 1985). Drinking-water levels of at least 1000 mg

barium/litre have been reported when the barium is 

present mainly in the form of insoluble salts (Kojola et

al., 1978). Levels of barium in Canadian water supplies

have been reported to range from 5 to 600 mg/litre

(Subramanian & Meranger, 1984), and barium

concentrations ranging from 1 to 20 mg/litre have been

measured in municipal water in Sweden (Reeves, 1986).

The concentration of barium in seawater varies

greatly among different oceans and varies with factors

such as latitude and depth within a given ocean. Several

studies have shown that the barium content in the open

ocean increases with the depth of water (Chow & Gold-

berg, 1960; Bolter et al., 1964; Turekian, 1965; Chow &

Patterson, 1966; Anderson & Hume, 1968). A Geosecs III

study of the south-west Pacific by Bacon & Edmond

(1972) found a barium profile of 4.9 mg/litre in surface

waters to 19.5 mg/litre in deep waters. Later studies by

Chow (1976) and Chow et al. (1978) corroborated these

values. Measured barium concentrations in the north-

east Pacific ranged from 8.5 to 32 mg/litre (Wolgemuth &

Broecker, 1970). Bernat et al. (1972) found that barium

concentration profiles for the eastern Pacific Ocean and

the Mediterranean Sea ranged from 5.2 to 25.2 mg/litre

and from 10.6 to 12.7 mg/litre, respectively. Anderson &

Hume (1968) reported concentrations in the Atlantic

Ocean ranging from 0.8 to 37.0 mg/litre in the equatorial

region and from 0.04 to 22.8 mg/litre in the North

Atlantic, with mean values of 6.5 and 7.6 mg/litre,

respectively. In Atlantic Ocean waters off Bermuda,

barium concentrations of 15.9–19.1 mg/litre have been

measured (Chow & Patterson, 1966).

The background level of barium in soils is consid-

ered to range from 100 to 3000 mg/kg, with an average of

500 mg/kg (Brooks, 1978). 

Various studies document concentrations of bar-

ium in Brazil nuts ranging from 1500 to 3000 mg/kg

(Robinson et al., 1950; Smith, 1971a). Barium is also

present in wheat, although most is concentrated in the

stalks and leaves rather than in the grain (Smith, 1971b).

Tomatoes and soybeans also concentrate soil barium;

the BCF ranges from 2 to 20 (Robinson et al., 1950).

Levels of barium found in other food items range from

<0.2 mg/kg in meats to 27 mg/kg in dry tea bags

(Gormican, 1970). McHargue (1913) reported that the

barium content of dry tobacco leaves was in the range of

88–293 mg/kg. Later measurements yielded 24–170 mg/

kg, with an average value of 105 mg/kg (Voss & Nicol,

1960). Most of this barium is likely to remain in the ash

during burning. The concentrations of barium in tobacco

smoke have not been reported.



Concise International Chemical Assessment Document 33

10

6.2

Human exposure

The most important route of exposure to barium

appears to be ingestion of barium through drinking-

water and food. Particles containing barium may be

inhaled into the lung, but little is known regarding the

absorption of barium by this route.

Schroeder et al. (1972) estimated that the mean

daily intake of barium is 1.24 mg in food. Hamilton &

Minski (1972) estimated the total intake of barium from

the diet to be 603 µg/day. The ICRP (1974) estimated

barium intake from dietary sources to be approximately

0.67 mg/day. WHO (1996) reported daily dietary intake of

barium for adults for the period 1970–1991 as 0.18

(minimum), 0.30 (median), and 0.72 (maximum) mg/person.

In a number of dietary studies, the average intake of

barium ranged from 0.3 to 1.77 mg/day (Tipton et al.,

1966, 1969; Gormican, 1970; ICRP, 1974). This is

equivalent to 0.004–0.025 mg barium/kg body weight per

day, assuming a 70-kg adult body weight. The barium

content in school lunches from 300 schools in 19 states

in the USA ranged from 0.09 to 0.43 mg/lunch, with a

mean of 0.17 mg/lunch (Murphy et al., 1971).

The barium content in drinking-water seems to

depend on regional geochemical conditions. In a study

of the water supplies of the 100 largest cities in the USA,

a median value of 0.43 mg/litre was reported; 94% of all

determinations were <0.100 mg/litre (Durfor & Becker,

1964). Assuming daily water consumption

of 2 litres/person, this represents an average intake of <0.200 mg barium/day. More recent studies by Letkie-

wicz et al. (1984) indicated that approximately 214 million

people in the USA using public water supplies are

exposed to barium levels ranging from 0.001 to

0.020 mg/litre. In certain regions of the USA, however,

barium levels may reach 10 mg/litre, and the average

intake could be as high as 20 mg/day (Calabrese, 1977).

Levels of barium in municipal water in Sweden as high as

20 mg/litre have been reported (Reeves, 1986).

Due to the paucity of information on the levels of

barium in ambient air, it is difficult to estimate the intake

from this source. The levels of barium in air rarely exceed

0.05 mg/m

3

 (Tabor & Warren, 1958). This value can be

used to estimate daily barium intake via the lungs.

Assuming that the average lung ventilation rates for

newborn babies, male adults undergoing light activity,

and male adults undergoing heavy activity are 0.5, 20,

and 43 litres/min, respectively (ICRP, 1974; IPCS, 1994),

the intake via inhalation would range from 0.04 to 3.1

mg/day. Other age groups and females are included in

this range. Earlier, the ICRP (1974) reported that intake of 

barium through inhalation ranges from 0.09 to 26 mg/day.

Using 0.95 mg/m

3

 (the upper-end estimate of ambient

barium concentrations from US EPA, 1984) and the

ventilation rates of ICRP (1974) for babies and adult

males, a range of intakes via inhalation of 0.68–59

mg/day can be estimated.

The ICRP (1974) reported the total dietary intake of

barium to be 0.75 mg/day, including both food and

fluids. Schroeder et al. (1972) estimated a total of

1.33 mg/day, including food, water, and air (0.001 mg)

intake.

Available data from industry in the United King-

dom indicate that airborne exposure to barium sulfate

can range from 3.5 to 9.1 mg/m

3

 (8-h time-weighted

average [TWA], total inhalable dust) during the manual

addition of barite to mixing hoppers in the oil drilling

industry, with short-term (10-min TWA, total inhalable

dust) exposures as high as 34.1 mg/m

3

. During the

processing of barite ore, in industries that typically use

enclosed processes and local exhaust ventilation (LEV),

exposures usually ranged between 1.3 and 3.7 mg/m

3

(total inhalable dust), with highest values in one factory

reaching 55.4 mg/m

3

. Exposure levels in the formulation

of plastics and coatings, where the process is usually

enclosed and LEV is used, are in the region of 1–

3.5 mg/m

3

 (Ball et al., 1997).

The wiring used in some speciality arc welding

processes has been shown to contain 20–40% soluble

barium compounds, and fumes produced during these

processes contain 25% barium (Dare et al., 1984).

Welders using such wire are exposed to estimated air-

borne concentrations of 2.2–6.2 mg soluble barium/m

3

(NIOSH, 1978).

Personal air sampling in the vicinity of oven-

charger and batch-mixer workers in art glass manufac-

turing plants revealed median ambient air concentrations

of 0.041 and 0.0365 mg barium/m

3

, respectively (Apostoli

et al., 1998). Mean concentrations of barium measured by

personal sampling methods in various locations within

ceramic factories in Spain ranged from 0.0012 to 0.0758

mg/m


3

 (Roig-Navarro et al., 1997).

Data from industry in the United Kingdom and

predictions made using the Estimation and Assessment

of Substance Exposure (EASE)

1

 model suggest that

1

 EASE is a general-purpose predictive model for

workplace exposure assessments. It is an electronic,

knowledge-based, expert system that is used where

measured exposure data are limited or not available. The

(continued...)



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