RADIOLOGICAL CHANGES IN ASBESTOS-CEMENT WORKERS

Objective-To explore associations between exposure to asbestos cement dust and radiographic findings in lung parenchyma and pleura. Methods- Radiographs from 174 blue collar workers and 29 white collar workers f rom an asbestos cement plant formed one part of the study. Progression of small opacities was further studied in those 124 blue collar worke rs, for whom two radiographs taken after the end of employment were av ailable. The median readings from five readers who used the full ILO 1 980 classification were used. As exposure indices, time since start of employment, duration of employment, cumulative exposure, and average intensity of asbestos exposure were used. The influence of age and smo king was also considered in multiple logistic regression analyses. Res ults-Small opacities (profusion greater than or equal to 1/0) were clo sely correlated with time related exposure variables, and showed weake r association with intensity based exposure variables. The odds ratio (OR) for small opacities was equal to 2.8 (90% CI 1.2, 6.7) in the >30 f(fibre)-y/ml group, compared with those in the 0-10 f-y/ml group. Pr ogression of at least two minor ILO categories after the end of employ ment was seen in 20%. Also, pleural thickening was closely related to time. By contrast, costophrenic angle obliterations were not associate d with the time related variables, but closely associated with the int ensity of asbestos exposure, and tended to occur during employment. Th e OR was 4.5 (90% CI 1.3, 15) in the >2 f/ml group, compared with thos e in the 0-1 f/ml group. Conclusions-In these workers, exposed mainly to chrysotile but also to small amounts of amphibole, the risk of radi ographically visible parenchymal abnormality was substantially increas ed and strongly dependent on time related exposure variables. Progress ion was found long after the end of exposure. The findings on costophr enic angle obliterations, supposed to be sequelae of benign pleural ef fusions, were consistent with an immediate reaction triggered by inten se asbestos exposure.