Early lung events following low-dose asbestos exposure

A conscious sheep model recently developed to study sequentially the bronchoalveolar milieu was applied to the investigation of the early lung events following very low dose asbestos exposure. UICC Canadian chrysotile fibers were administered in three monthly intratracheal injections of a suspension of 0 (controls), 1, 2, 4, 8, and 16 mg of asbestos in 50 ml saline. Three sheep per dose were repeatedly exposed to the same monthly doses and all were studied by serial pulmonary function (PF) tests, transbronchial lung biopsies (LB), and bronchoalveolar lavages (BAL). These low-dose exposures did not change the PF tests; routine lung histopathology was not altered except for the observation of occasional fibers in the alveoli, but there was a significantly higher yield in the total BAL cellular due to a marked increase in the macrophage and a small rise in the lymphocyte populations. These changes in the BAL cells occurred without significant changes in the biochemical analyses of the BAL supernatant. These data establish that very low dose asbestos exposure induces migration of macrophages and lymphocytes into the bronchoalveolar milieu. These cells have a major role in the lung defense and have been implicated in the development of asbestos-related diseases.