Silicon carbide pneumoconiosis: a radiographic assessment

Interstitial lung disease and airflow limitation have been reported in silicon carbide workers but it is uncertain whether these recent observations reflect past working conditions alone (30 years ago) or both past and present conditions even if the latter have improved. To investigate this, we analyzed pairs of chest radiographs obtained in 1977 and 1984 in 128 silicon carbide plant workers. Three indices, related to density of small opacities, profusion of opacities, and presence of pleural plaques, were obtained. Student t-tests on results obtained in each time period showed the mean density (1.02 in 1977 and 0.56 in 1984) and profusion (4.27 in 1977 and 2.13 in 1984) indices to be significantly different. However, the pleural plaque index was not different in 1984 (0.34) as compared with 1977 (0.32). There was no deterioration of the radiographic image even in groups with density ratios equal or greater than 1/1. We concluded that the actual environmental working conditions did not influence the integrity of the lung radiographic image in these workers within a time span of 6 or 7 years.