HEALTH-EFFECTS OF REFRACTORY CERAMIC FIBERS - SCIENTIFIC ISSUES AND POLICY CONSIDERATIONS

Objectives-To review the scientific literature on the health effects o f refractory ceramic fibres (RCFs). The adverse effects of exposure to asbestos has led to concern about the potential for other fibrous mat erials to cause diseases. For this reason the human populations most h eavily exposed to synthetic mineral fibres have been examined for any adverse effects and many types of fibre have been studied in animal ex periments. One type of man made vitreous fibres (MMVFs), refractory ce ramic fibres (RCFs), are principally used in thermal insulation at hig h temperatures-up to 1400 degrees C. As manufactured RCFs exist in a g lassy, non-crystalline (sometimes called amorphous) state, they have v arious compositions, physical properties, and sized fibres. Methods-Al l reports on the health effects of RCFs available up to the end of 199 4 have been examined and the scientific literature reviewed although a ll publications have not necessarily been referenced. Conclusions-In r ecent inhalation experiments conducted with both rats and hamsters at the Research and Consulting Company, Geneva, at the highest dose teste d (30 mg/m(3)) there was an increased incidence of tumours in both spe cies. Lower doses were only examined in the rat and at these doses the re was no significant excess of lung tumours. Epidemiological investig ations of workers engaged in the manufacture of ceramic fibres have sh own a small excess of pleural plaques. This phenomenon is being furthe r investigated but could be due to confounding exposures. The populati ons available for study are small and their exposures fairly short, bu t it is considered prudent that they should remain under surveillance for some time to come. This is despite the fact that present exposures in the ceramic fibre industry are low (< 1 f/ml) and are being reduce d.