The advantages and limitations of an in vivo test system for investigating the cytotoxicity and fibrogenicity of fibrous dusts.

The acute response of the rat lung to a range of fibrous materials has been investigated by bronchopulmonary lavage, at dose levels of 0.5 and 1.0 mg, 1 and 7 days after their administration by intratracheal instillation. The materials chosen for study included UICC chrysotile A, amosite, crocidolite and anthophyllite, and samples of S. African "long" amosite and glass fiber. In addition, the subacute response to 1, 2 and 3 mg of chrysotile and amosite has been studied at 50 and 100 days after instillation. In the acute phase at 1 day after instillation, the response to chrysotile was greater than that to any of the other materials, but by 7 days there was no gradation in the response to different dusts. In the subacute phase, cell recoveries were low, and it was not possible to assess the long-term cytotoxic or fibrogenic effects of amosite and chrysotile by analyses of lung washes, even though biochemical and histological methods indicated gross changes in lung pathology.