Distribution of Asbestos Bodies in the Human Lung as Determined by Bronchoalveolar Lavage

Abstract
Asbestos-related lung diseases tend to have distinct local distributions, for example, asbestosis first appears and tends to be more severe in the peripheral parts of the lower lung zones. The risk for asbestosis is related to the total asbestos burden of the lung. This suggests that the lower lobes in asbestos-exposed individuals may contain more asbestos than the other lobes. To test whether such topographic differences exist, we compared the number of retrieved asbestos bodies (AB) per ml BAL fluid in three groups of occupationally asbestos-exposed subjects who underwent BAL at different sampling sites. In Group 1 (n = 24) we performed BAL at three sites, namely in a segment of the right upper, right middle, and right lower lobe, to evaluate differences in asbestos body burden from lung apex to basis. There was a distinct increase in BAL asbestos body concentrations from the upper (21.2 ± 9.1 AB/ml BAL fluid) to the middle (30.4 ± 12.8 AB/ml BAL fluid) and to the lower lobe (56.0 ± 20.2 AB/ml BAL fluid), all differences being significant (p < 0.01). In Group 2 (n = 40), we found good interlobar correlations for asbestos body counts between the right middle lobe (21.0 ± 5.8 AB/ml BAL fluid) and the lingula (22.4 ± 5.9 AB/ml BAL fluid) (r = 0.941, p < 0.001) and, in Group 3 (n = 15), between the ventral basal segment of the right (41.2 ± 13.6 AB/ml BAL fluid) and left lung (39.0 ± 13.6 AB/ml BAL fluid) (r = 0.966, p < 0.001). This study demonstrates topographic variations in BAL asbestos body counts between lung apex and lung basis but not between corresponding segments of the right and left lung. This distribution of asbestos bodies as recovered by BAL confirms pathologic observations and correlates with the clinical observation that asbestosis is more severe in the lower lobes. If BAL is used as a bioassay of former asbestos exposure, lavage in a basal segment of a lower lobe is recommended.