The effects of chrysotile and crocidolite asbestos on the lower respiratory tract: analysis of bronchoalveolar lavage constituents.

This study was designed to evaluate the effects of amphibole and serpentine asbestos inhalation on the constituents of the lower respiratory tract. Bronchoalveolar lavage (BAL) analyses were performed on three groups of rats: one group was exposed to chrysotile (serpentine) asbestos, another group was exposed to crocidolite amphibole asbestos, while a third group was sham-exposed. Intermittent inhalational exposures lasted three months. The total BAL cell yields and the macrophage content of BAL cells were significantly lower after asbestos exposure, especially in the chrysotile-exposed group. These effects persisted for as long as 1 year after the cessation of exposure. Multinucleated macrophages were seen in BAL cells from both asbestos-exposed groups. Striking ultrastructural alterations of macrophage morphology were noted in BAL cells from both groups of asbestos-exposed rats. Chrysotile fibers were not seen in any BAL cells from chrysotile-exposed animals. However, 15 months after terminating the exposure regimen, a sizeable proportion of BAL macrophages from crocidolite-exposed rats contained phagocytosed asbestos fibers. Significantly higher beta-glucuronidase and lactate dehydrogenase activity was found in BAL fluids from both asbestos-exposed groups and was detected 17-18 months after exposure had ceased. These observations have served as useful correlates of asbestos-mediated injury to the lower respiratory tract. They have also provided evidence of continual pathological sequelae occurring long after withdrawal from asbestos exposure.