Abstract
Associations between lifetime chrysotile (12001295) asbestos exposure, asbestosis, and asbestos lung burdens in a cohort of former workers were examined. The report was part of a mortality study of the employees at an asbestos textile factory in Charleston, South Carolina, where chrysotile was the only type of asbestos used as a raw material. Information on asbestos exposure, autopsy records, and lung tissue sections were available for 54 asbestos workers who had died from asbestosis. Lung tissue samples and autopsy records from 34 deceased subjects with no occupational asbestos exposure were controls. Lung tissue sections were graded for extent and severity of asbestosis. Tissue sections were also analyzed by transmission electron microscopy combined with X-ray spectrometry to characterize fiber deposits. Associations between asbestos exposure variables and asbestos fiber lung burdens and severity of asbestosis were examined by logistic regression analysis. Median cumulative asbestos exposures for asbestos workers was 30.2 fiber years. The geometric mean (GM) total fiber concentrations in asbestos worker and control lung tissue sections were 52.46x10(6) and 16.02x10(6) fibers per gram (f/g), respectively. Chrysotile was the predominant fiber found in lungs of asbestos workers and controls, the GM concentrations being 33.45x10(6) and 6.7x10(6)f/g, respectively. Significant amounts of tremolite (77536686) were also found in asbestos workers' lungs, but not in controls, 3.56 versus 0.26f/g. The length and aspect ratios of the chrysotile fibers were greater in asbestos workers than in controls. Lifetime cumulative asbestos exposures correlated with total asbestos, chrysotile, and tremolite lung burdens in asbestos workers. Severity of asbestosis correlated with cumulative asbestos exposure and total asbestos lung burdens. Lung cancer was present in tissue samples from 18.2% of asbestos workers and 5.8% of controls. Asbestos workers with lung cancer had greater cumulative asbestos exposures, higher total asbestos lung burdens, and more severe asbestosis. The authors conclude that both cumulative asbestos exposure and total asbestos fiber lung burdens are associated with asbestosis severity. Asbestosis and lung cancer in this population resulted from exposure to chrysotile long fibers.
