Pleuropulmonary disease among asbestos workers in relation to smoking and type of exposure

The chest roentgenograms of employees aged 40 and over in two asbestos manufacturing plants were read by consensus without knowledge of the plant or smoking habits. Plant A used only chrysotile asbestos throughout its history and Plant B used amosite as well as chrysotile, the amosite being limited to the period 1950-64. The prevalence of pulmonary disease was 25% in Plant A and 33% in Plant B. The prevalence of pleural thickening was 18% in Plant A and 35% in Plant B. Neither age nor work duration were factors in these differences. In Plant A there was no obvious relationship between smoking and pleuropulmonary disease. In Plant B there was a definite relationship of smoking to pulmonary disease and perhaps to pleural thickening. Both type of asbestos and smoking habits appear to be determinants of pleuropulmonary disease in asbestos workers.