Sequence of bronchoalveolar lavage and histopathologic findings in rat lungs early in inhalation asbestos exposure.

To assess the early cellular inflammatory response of the lungs, 7 rats per group were exposed nose-only to 13 mg/m3 of chrysotile asbestos, 7 h/day for 2, 4, or 6 wk. Lung histopathology and bronchoalveolar lavage (BAL) were analyzed. In exposed animals, dose-related bronchiolitis and fibrosis were found that were not seen in control rats (p less than 0.001). In exposed rats, total BAL cells were increased six-to sevenfold over matched controls, and more cells were retrieved with longer exposure (p less than 0.001). In the BAL, counts of macrophages, lymphocytes, and polymorphonuclear cells (PMNs) were each elevated in the exposed rats (each p less than 0.001). PMNs seen histologically and in the BAL may be related to the time period examined. PMNs and lymphocytes observed throughout this 6-wk study support the idea that these cells may have an important role in the early events of asbestos lung injury