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Administrative data

Endpoint:
epidemiological data
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Well documented epidemiological study with limited number of subjects.

Data source

Reference
Reference Type:
publication
Title:
Evaluation of an Occupational Respiratory Exposure to a Zirconium-Containing Dust
Author:
Hadjimichael EC, Brubaker RE
Year:
1981
Bibliographic source:
Journal of Occupational Medicine/Vol. 23, pages 543-547

Materials and methods

Study type:
case control study (prospective)
Principles of method if other than guideline:
Case-control study
GLP compliance:
no

Test material

Constituent 1
Reference substance name:
dust containing 25% zirconium
IUPAC Name:
dust containing 25% zirconium
Details on test material:
- Name of test material (as cited in study report): dust containing 25% zirconium

Method

Type of population:
occupational
Ethical approval:
not specified
Details on study design:
A group of hand finishers of zirconium metal reactor components questioned whether the dust to which they were exposed would cause chronic lung disease or cancer or both. To investigate this possibility, the work environment was surveyed, and 32 male employees who had worked as hand finishers from one to seventeen years, were compared to a group of controls in reference to a respiratory questionnaire, chest x-ray findings, and expiratory lung function tests. The controls were matched to the hand finishers for age, sex, payroll status and smoking history.

Thirty-two hourly-paid men comprised the study group of hand finishers. Twenty-five of these were currently working as hand finishers, four had been transferred to other departments and three had left the company. None of the latter seven had been exposed subsequently to dusts or pulmonary irritants at work. Only men who had worked as hand finishers for one year or more were included in the study group. Four current workers were not included. Two of these refused participation and two were excluded because of symptomatic pulmonary disease unrelated to work. The average length of exposure was 4.9 years, with a range of one to seventeen years. Eleven men had worked as hand finishers for less than three years and 21 for more than three. The control group was chosen from among other hourly-paid workers in the plant, excluding grinders, maintenance personnel, and others who may have been exposed to dusts or respiratory irritants. There were only white males in both the study and control groups. The controls were matched for age within five years and for current and total smoking history.
Exposure assessment:
measured
Details on exposure:
The company in which this study was done manufactures nuclear fuel components fabricated primarily of zirconium metal. One production process involves the handfinishing of large metal shapes with cloth strips impregnated with aluminium oxide or silicon carbide (as abrasives), or with small rotating hand-held sanders impregnated with silicon carbide. The abrasives of the cloth and sanders are held together with small amounts of glue, rubber, cement, and phenolic resins as binding agents. Dust was produced when the rotating sanders were used, when dust from the benches was swept to the floor, and in the summer when large ventilating fans were operating. High volume total dust samples taken at the breathing zones of workers who were using the hand-held rotating sanders ranged from 5.75 to 14.7 mg/m3. Atomic absorption analysis showed that 25% of the dust was zirconium; the remainder consisted of silicon carbide, binding agent, and general shop dust. Particle size analysis of the high volume sample indicated that 64% of the particles were less than five microns in diameter, 21% between five and ten microns, and 14% greater than ten microns. Multiple breathing zone samples collected on mixed cellulose ester filters of 0.8 micron pore size varied between 0.67 and 3.2 mg/m3 of zirconium. Particle sizing of these samples showed that 60% were less than two microns and 95% less than ten microns in diameter.

Results and discussion

Results:
No excess of respiratory symptoms and no radiologic evidence of pneumoconiosis occurred among the exposed men. Comparison of the results of the various lung function measurements, for both observed and residuals, showed the values for the study group to be consistently lower than those for the controls, but the differences were not significantly different.
The comparatively lower Forced Expiratory Volume after 1 second (FEV1) and FEV1/Forced Vital Capacity (FVC) ratio and the low observed Forced Expiratory Flow in the middle 1/2 of an expiration (FEF25-75%) in the lesser-exposed group were unexpected. It would be expected that if the dust exposure had an adverse effect on the airways, it would be manifest in the longer exposed group. These findings could not be explained by differences in age or smoking habits, or by bias due to turnover.
Confounding factors:
No data
Strengths and weaknesses:
The author reports that due to limitations of the analysis imposed by the size of the group, it is reasonable to assume that the low values found in the short-term group are the result of statistical chance.

Applicant's summary and conclusion

Conclusions:
The authors were unable to show any significant adverse effects on the handfinishers from the zirconium exposure, but recognize that the study group was small, the zirconium concentration low, and the exposure time relative short.

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