Man-made vitreous (silicate) fibres with random orientation with alkaline and alkali earth oxides (Na2O+K2O+CaO+ MgO+BaO) content greater than 18% by weight and fulfilling one of the CLP Regulation Annex VI Note Q conditions

Epidemiological data

Administrative data

Endpoint:

epidemiological data

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1982

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

Ophthamologic effects of man-made mineral fibers

Author:

Stokholm J., Norn M. and Schneider T.

Year:

1982

Bibliographic source:

Scandinavian Journal of Work, Environment & Health 8(3):185-190, 1982.

Materials and methods

Study type:

cross sectional study

Endpoint addressed:

eye irritation

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

- Principle of the study: The effect of man-made mineral fibres on the human eye was investigated in a cross-sectional study of 15 workers exposed to Rockwool and a matched reference group of 15 people. The number of fibres accumulated in the eye and conventional dust sampling methods were used as measures of dose.
- Parameters analysed/observed: The investigation program comprised an eye history, based upon a questionnaire and an interview, sampling of conjunctival fluid for quantitative cytology, a general medical examination of the external eye, slit lamp examination, measurement of ruptures in the precorneal film, break-up time, and vital staining of cornea and conjunctiva to reveal any microepithelial defects and dead or degenerated cells.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Reference substance 001

Test material form:

solid: fibres

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Rockwool®

Method

Type of population:

occupational

Ethical approval:

not specified

Details on study design:

HYPOTHESIS TESTED
Man-made mineral fibres have the same mechanical irritant effect on the eye as on the skin.

METHOD OF DATA COLLECTION
- Type of study: Cross-sectional study of an exposed group who had been occupied with the production, cutting, and packing of Rockwool for at least six months.
- Details: The investigation program comprised an eye history, based upon a questionnaire and an interview, sampling of conjunctival fluid for quantitative cytology, a general medical examination of the external eye, slit lamp examination, measurement of ruptures in the precorneal film, break-up time, and vital staining of cornea and conjunctiva to reveal any microepithelial defects and dead or degenerated cells.

SETTING
The exposed group went through this program on a Monday (just before resuming work after the weekend) and again four days later (this time at the end of the workday). All the examinations, including the slit lamp examinations, were carried out in a room adjacent to the work area. The reference group went through the same program once, except for the sampling of conjunctival fluid and removal of the mucous thread.

STUDY POPULATION
- Total population: 15
- Selection criteria: Workers who had been occupied with the production (control of production line), cutting, and packing of Rockwool for at least six months
- Sex/age/race: The exposed group included 15 workers (13 men and 2 women). Users of contact lenses were excluded. One woman in the exposed group was sick and absent from work on the second day of the investigation. The mean age of each group was 38 years (range 19-63 years).
- Smoker/nonsmoker: The group included 14 smokers. The average tobacco consumption was 16 g/d.

COMPARISON POPULATION
A matched (age, sex, smoking habits) non-exposed reference group was included. No member of the reference group had been exposed to dust, fibres, or solvents at work or to any large amount of fibres or dust in their spare time during the week before the start of the investigation.

HEALTH EFFECTS STUDIED
The investigation program included an eye history, based upon a questionnaire and an interview, sampling of conjunctival fluid for quantitative cytology, a general medical examination of the external eye, slit lamp examination, measurement of ruptures in the precorneal film, break-up time, and vital staining of cornea and conjunctiva to reveal any microepithelial defects and dead or degenerated cells.

Exposure assessment:

measured

Details on exposure:

TYPE OF EXPOSURE MEASUREMENT
The number of fibres accumulated in the eye and conventional dust sampling methods (traditional filter methods) were used as measures of dose.

EXPOSURE PERIOD
At least six months for the exposed group

Statistical methods:

A Fisher exact probability test was used to test the differences between and within the groups, and the Spearman rank-order correlation test was used to determine any correlation between the groups.

Results and discussion

Results:

FINDINGS
- Questionnaire: Of those in the exposed group, five reported previous eye infections diagnosed by a doctor in comparison with two in the reference group, and four exposed workers reported eye damage needed to be seen by a doctor in comparison with two in the reference group. Whereas none of the reference group used eye medication at the time of the investigation, three people in the exposed group did. Two of these three people used eye medication almost constantly. The third had visited a firstaid
station because of eye irritation, just before the investigation was conducted.
- Interview: From the medical interview it appeared that the itching sensation was first and foremost located in the medial bulbar part of the eye. Symptoms were reported to disappear after work, and had usually disappeared by the next morning.
-Slit lamp examination: There was no significant difference between break-up times in the two groups, and the mean values were comparable to other findings. Neither was any significant change in break-up time in the exposed group from Monday morning to Thursday at the end of the workday observed. The number of epithelial defects, depicted by the fluorescein staining, increased significantly (p = 0.009) for the medial bulbar conjunctiva after 4 d of exposure in comparison with those in the reference group. Vital staining did not show any other significant differences between and within the groups. However, a slight increase in the number of rose bengal-stained dead or degenerated cells was observed after 4 d of work.
- Conjunctival fluid cytology: In one conjunctival fluid sample an increased number of neutrophils (11,300) and Lymphocytes (1,100) was found before exposure to man-made mineral fibres. One person had a marginally increased number of neutrophils. The other findings were entirely within the normal range. After exposure, only samples from 12 workers were suitable for further examination. A pathologically increased neutrophil count was found in six cases (p = 0.06, range 116-1,530). One sample was accompanied by a pathological increase in the number of columnar epithelial cells, nucleated squamous cells, and keratinized nucleated cells. In no case did the lymphocyte count increase after exposure, and no esinophilic granulocytes were found. There was significant correlation between the number of neutrophils and lymphocytes and the number of rose bengal-stained degenerated and dead cells (rs = 0.85) but not between the number of neutrophils and lymphocytes and the number of fluorescein-stained epithelial defects (rs = 0.12). An increased amount of mucus was found in 10 of the 15 conjunctival fluid samples taken on Monday morning and in 8 of the 12 samples taken after exposure. In some of the samples, this increase in mucous content was not accompanied by any subsequent increase in the neutrophilic count.

Strengths and weaknesses:

The observations are based upon a small study population and should therefore be repeated.

Any other information on results incl. tables

Dose-effect relationship:

There was a significant correlation between the number of fluorescein-stained epithelial defects on the medial bulbar conjunctiva and the number of fibres accumulated in the opposite eye. There was also a significant correlation between the number of fluorescein-stained epithelial defects and the total airborne dust dose determined by filter sampling. A non-significant correlation was found between the number of rose bengal-stained cells and the number of fibres accumulated in the eye.

Applicant's summary and conclusion

Conclusions:

It was concluded that observed effects and cellular changes can be explained by the assumption that man-made mineral fibres have the same mechanical and reversible effect on the eye as on the skin.

Executive summary:

In this study, the effect of man-made mineral fibers on the human eye was investigated in a cross-sectional study of 15 workers exposed to Rockwool and a matched reference group of 15 people. Eye symptoms, changes in the cellular and mucous content of the conjunctival fluid, break-up time of the precorneal film, the number of microepithelial defects, and the number of dead and degenerated cells on the cornea and bulbar conjunctiva were used as measures of effect. The number of fibers accumulated in the eye and conventional dust sampling methods were used as measures of dose. A significantly higher frequency of eye symptoms related to work conditions was found among exposed workers. The number of microepithelial defects on the medial bulbar conjunctiva increased significantly after 4 days of exposure. Six exposed workers had a pathological increase in the neutrophil count of the conjunctival fluid after 4 days of exposure, and an increase was seen in only one worker after a weekend free from exposure. Significant correlation was found between microepithelial defects on the medial bulbar conjunctiva and measures of dose. Thus, it was concluded that these symptoms and cellular changes can be explained by the assumption that man-made mineral fibres have the same mechanical and reversible effect on the eye as on the skin.