Development of radiographic abnormality in chrysotile miners and millers.

has been known for 50 years that inhalation of asbestos dust can lead to appearances on chest roentgenograms that are different from those associated with silicosis and coal workers’ pneumoconiosis.1 However, only the latest international classifications of the radiographic appearances of the pneumoconioses allow the recording of such shadows.2’3 These include what are now called small irregular opacities together with a variety of pleural changes. It is thought that small irregular opacities appearing first in the lower lung zones are characteristic of asbestos exposure.2 Descriptions of the “typical” radiographic appearances of asbestosis have not come, however, from epidemiologic surveys of representative samples of exposed subjects because such surveys have included neither sufficient numbers with intrapulmonary abnormalities nor detailed reviews of the many different types of radiographic features.4 Further, most epidemiologic studies have been concerned with a single film for each subject; none known to the author has attempted to describe the first appearance of radiographic abnormality. An opportunity to examine the natural history of radiographic signs of asbestos exposure arose from an epidemiologic study whose primary objectives were a comparison of reading methods for assessing radiographic progression in asbestos workers5 and an investigation of the relationship between radiographic progression and measures of asbestos exposure.6 Data from this study have been used in the present report to describe the first pneumoconiotic appearances.