Silicon carbide

Epidemiological data

Administrative data

Endpoint:

epidemiological data

Type of information:

other: epidemiological study

Adequacy of study:

other information

Reliability:

2 (reliable with restrictions)

Materials and methods

Study type:

cohort study (retrospective)

Endpoint addressed:

repeated dose toxicity: inhalation

carcinogenicity

Method

Type of population:

occupational

Details on study design:

The study was of a cohort design with a comparison of the cancer morbidity and mortality with that of the general population. Complete personnel files were available from about 1955. These files were used to identify a cohort of men with at least five years employment some time between 1955 and 1983. A total of 911 individuals were enrolled; 211 were women, both in administration and production, and of the 700 men, 521 were blue collar workers. All individuals were traced through the official registers and followed up until 31 December 1983 if not dead or emigrated before that date. Seven men had emigrated and eight could not be traced; all were blue collar workers. The loss to follow up was thus about 2% in total or 3% for the blue collar workers.
Information about mortality and cancer morbidity was collected through the National Death Register and the National Cancer Register, respectively. Only the underlying cause of death was considered and a restriction was made by excluding ages above 74 as the diagnostic validity is likely to decrease at higher ages. The observation periods were 1958-83 for mortality and 1958-81 for cancer morbidity, the reason for the difference in the observation period being the lack of cancer incidence data after 1981. Expected incidences were calculated with the person-year method using incidence rates for the general population, stratified for age, calendar year, and gender, for which procedure the EPILIN program was used.

Exposure assessment:

estimated

Details on exposure:

The company principally manufactured grinding wheels using aluminium oxide and silicon carbide as abrasives. The abrasives were bound with clay or phenol formaldehyde resins; fillers were also used. Dust measurements had been undertaken since the early 1970s and the exposure of the workers could be divided into heavy or low exposure to abrasives. Heavy exposure refers to an estimated total dust exposure of 5 mg/m³ or more; low means less than 5 mg/m³. The concentrations were often about 1mg/m³ in the jobs with low exposure. ln a few operations there was also exposure to silica at about 0.1 mg/m³. During the manufacture of grinding wheels bound by formaldehyde resins, there was a moderate exposure to formaldehyde (0.1-1 mg/m³). Fifty nine workers had manufactured abrasive belts. They had had a low exposure to abrasives but an intermittent, heavy exposure to formaldehyde with peaks up to 20-30 mg/m³.

Results and discussion

Results:

No significant increase was found in mortality or in cancer morbidity among the blue collar workers.
Among the blue collar workers were four cases of non-malignant respiratory diseases (pneumonia (1), chronic bronchitis (2), and asthma (1)), whereas 3.2 cases of respiratory diseases would have been expected for the general population.
No case of silicosis was found.

Applicant's summary and conclusion

Executive summary:

The cancer morbidity and the total mortality pattern was studied among 521 men manufacturing abrasive materials who had been exposed to aluminium oxide, silicon carbide, and formaldehyde. Total dust levels were in the range of 0.1 -1.0 mg/m³. The cohort was followed up from 1958 until December 1983. No significant increase was found in total mortality, cancer mortality, or incidence of non-malignant respiratory diseases.