A comparison of the pathological effects in rats of the UICC reference samples of amosite and chrysotile with those of amosite and chrysotile collected from the factory environment.

Inhalation studies were undertaken in rats to compare the pathogenic effects of samples of UICC amosite and chrysotile with those of amosite and chrysotile samples collected from the factory environment. Fibre length and diameter studies on the four dust samples showed that the UICC chrysotile cloud contained more long fibres than factory chrysotile, although the factory fibres tended to be thicker. The factory amosite cloud contained more long fibres than UICC amosite, but again the factory fibres were thicker. The factory dusts contained considerable amounts of impurities; in spite of this, the lung dust content of asbestos at the end of 12 months' dusting was higher with factory dusts than with UICC material. The UICC chrysotile and factory chrysotile produced similar levels of interstitial fibrosis, but the factory dust produced fewer malignant lung tumours. The factory amosite produced much more interstitial fibrosis than UICC amosite, but neither amosite cloud produced any malignant pulmonary tumours. These results are discussed in relation to current theories on the importance of fibre dimensions in the pathogenesis of lung disease.