Enhanced retention of asbestos fibers in the airways of human smokers.

To determine whether cigarette smoke increases the pulmonary retention of asbestos, we compared the asbestos-fiber burden in the airway mucosa of six cigarette smokers who had received heavy occupational asbestos exposure with that in a group of six subjects with similar exposure who were never smokers. The groups were matched in terms of age, sex, years of exposure, and mean parenchymal amosite burden. We found that the concentration of amosite in airway mucosa was significantly elevated (by approximately sixfold) in smokers (p < 0.02). Chrysotile parenchymal burdens were statistically similar in both groups, but the chrysotile airway burden was again higher (by approximately 50-fold) in smokers (p < 0.006). There were no differences in airway or parenchymal tremolite burdens between the two groups. Fibers of all three types of asbestos recovered from the airway mucosa or parenchyma of smokers were shorter than fibers recovered from nonsmokers, an observation in accord with experimental data suggesting that cigarette smoke leads to retention of shorter fibers. These findings indicate that cigarette smoking causes enhanced accumulation of both amosite and chrysotile in the airway mucosa. This process may play a role in potentiating the pathologic effects of asbestos.