Exposure to used ceramic fiber product
Product which has been at service in elevated temperatures (greater than 932 °C/1800 °F)
may undergo partial conversion to cristobalite, a form of crystalline silica which can cause
severe respiratory disease (pneumoconiosis). The amount of cristobalite present will
depend on the temperature and length of time in service. (See Section A.2.3 for permissible
exposure levels).
Special toxic effects
The existing toxicology and epidemiology data bases for RCFs are still prelimnary.
Information will be updated as studies are completed and reviewed. The following is a
review of the results to date:
Epidemiology
At this time, there are no known published reports demonstrating negative health
outcomes of workers exposed to refractory ceramic fiber (RCF). Epidemiologic
investigation of RCF production workers are ongoing.
1. There is no evidence of any fibrotic lung disease (interstitial fibrosis) whatsoever on
x-ray.
2. There is no evidence of any lung disease among those employees exposed to RCF
that had never smoked.
3. A statistical trend was observed in the exposed population between the duration of
exposure to RCF and a decrease in some measures of pulmonary function. These
observations are clinically insignificant. In other words, if these observations were
made on an individual employee, the results would be interpreted as being within
the normal range.
4. Pleural plaques (thickening along the chest wall) have been observed in a small
number of employees who had a long duration of employment. There are several
occupational and non-occupational causes for pleural plaque. It should be noted
that plaques are not pre-cancer, nor are they associated with any measurable effect
in lung function.
Toxicology
A number of studies on the health effects of inhalation exposure of rats and hamsters are
available. Rats were exposed to RCF in a series of life-time nose-only inhalation studies. The
animals were exposed to 30, 16, 9, and 3 mg/m
3
, which corresponds with approximately
200, 150, 75, and 25 fibers/cc.
Animals exposed to 30 and 16 mg/m
3
were observed to have developed a pleural and
parenchymal fibrosis; animals exposed to 9 mg/m
3
had developed a mild parenchymal
fibrosis; animals exposed to the lowest dose were found to have the response typically
observed any time a material is inhaled into the deep lung. While a statistically significant
increase in lung tumors was observed following exposure to the highest dose, there were
no excess lung cancers at the other doses. Two rats exposed to 30 mg/m3 and one rat
exposed to 9 mg/m3 developed masotheliomas.
Safety data
268 OCX 8800
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