Barium oxide, obtained by calcining witherite

Health surveillance data

Administrative data

Endpoint:

health surveillance data

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study conducted on human test subjects which welded barium-containing metals, however the representation of different barium components was not given and the cohort was quite small.

Data source

Reference

Reference Type:

publication

Title:

Exposure to soluble barium compounds: an interventional study in arc welders

Author:

Zschiesche et al

Year:

1992

Bibliographic source:

International Archives of Occupational and Environmental Health

Materials and methods

Study type:

biological effect monitoring

Remarks:

Biokinetic surveillance

Endpoint addressed:

basic toxicokinetics

repeated dose toxicity: inhalation

Test guideline

Qualifier:

no guideline available

Principles of method if other than guideline:

Healthy test persons (arc welders) were monitored while welding barium-containing metal (stick electrodes or self-shielded flux wires) for 5 days. Plasma, urine and air barium levels were measured. Baseline levels for the investigated parameters were obtained 2 workdays prior to start of the study and test subjects were monitored for one workday after the last barium exposure, with a week-end inbetween.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Barium-containing stick electrodes

IUPAC Name:

Barium-containing stick electrodes

Constituent 2

Reference substance name:

barium-containing self-shielded flux wires

IUPAC Name:

barium-containing self-shielded flux wires

Test material form:

other: fumes

Details on test material:

Fumes contained a mixture of barium compounds to about 31.7%, of which 15.8% were soluble in water (at room temperature) within 1 hour and 99% were soluble in 0.07N HCl

Method

Type of population:

occupational

Ethical approval:

confirmed, but no further information available

Details on study design:

Test subjects: 18 welders, health, no medical history of any symptoms associated with barium exposure, none of them had been in contact with barium for at least 10 days
They were split into 3 groups performing arc welding with different barium-containing metals and tools, leading to different exposure levels.
Barium levels in the air were measured by sensors attached to the inside of the face shield, monitoring the air directly breathed by the welders.
Week 1: Thursday, Friday: Welding of barium-free metal and establishing of baseline values
Week 2: Monday-Friday: Welding of barium-containing metals for 4h a day, average of 80% arc time. Daily assessment of clinical parameters
Week 3: Monday: Welding of barium-free metal and determination of remaining barium levels

Results and discussion

Results:

Exposure of welders to 4.4 mg/m3 barium fumes for 4 hours a day did not lead to any symptoms associated with barium. The plasma and urine barium levels were increased after the shift and decreased again the next morning; over time the baseline barium levels increased. After the free weekend, the barium concentrations in plasma and urine were in the range of the starting values.

Any other information on results incl. tables

External exposure surveillance revealed an average of 4.4 mg/m3 barium fumes in stick electrode welding and 2.0 mg/m3 barium fumes in flux cored wire welding.

Urine samples taken from the workers showed great baseline variations, between 1 ug/l up to 72.3 ug/l. Of 106 urine samples taken, only 12 showed barium concentrations of more than 20 ug/l. Upon exposure to barium-containing fumes, renal excretion of barium was increased to median concentrations of 101.7 ug/l (Group A, Wednesday after shift), 113.1 ug/l (Group B, Friday after shift), and 44.3 ug/l (Group C, Friday after shift).

Barium plasma levels were more homogenous than urine levels, with 97% of the samples showing a value of or below 8 ug/ml. Upon barium exposure, the barium levels in plasma increased similarly to the urine levels, median concentrations of 24.7 ug/l (Group A), 16.6 ug/l (Group B), and 4.4 ug/l (Group C).

Both plasma and urine levels were increased after the shifts in which the welders worked with barium-containing materials, and they decreased again until the following morning. Baseline barium levels steadily increased over the course of one week, but over the weekend they returned to the the total range of values found before exposure.

An elimination rate for Ba could be determined considering those individuals with urine concentrations of greater than 40 ug/l on Friday after the shift. The biological half-time of barium in plasma and urine was calculated to be between 10 and 18 hours, and the corresponding elimination curve followed first-order kinetics.

The clinical investigation of the welders did not reveal symptoms that could be directly correlated with barium exposure; all ailings reported could be traced back to pre-existing conditions. Further, no exposure-related trend in the pulse rate was observed; a group of welders showed a slight decrease in blood pressure, which was withing the range of normal values. Auscultation of the lungs did not reveal any irregularities and also the neurological examination did not yield any extraordinary findings.

Barium had been reported to result in hypokalemia, however the potassium levels of the welders remained within a normal range.

Applicant's summary and conclusion

Conclusions:

Exposure of healthy adults to 4.4 mg/m3 barium fumes for 4h per day over the course of one week did not lead to any adverse findings.

Executive summary:

18 welders in 3 groups were arc welding barium-containing materials for one week, releasing on average up to 4.4 mg/m3 barium fumes. Biomonitoring showed increased plasma and urine barium levels after welding, but also demonstrated rapid elimination over night. Over the course of the week, an increase of the baseline barium levels was observed, suggesting that repeated exposure might lead to accumulation of barium in the body. However, one free weekend (equaling 2 days of non-exposure to barium) was sufficient to obtain values in the range of baseline levels after. The clinical symptoms observed could not be correlated with barium exposure but were traced back to pre-existing conditions. On the basis of this data, exposure to 4.4 mg/m3 barium for 4 hours a day over the course of one week can be considered safe.