Pleural plaques in a health survey material. Frequency, development and exposure to asbestos

All cases of pleural plaques discovered at mass X-ray screening in Uppsala County during 1970-1976 were collected. Case histories, including the history of exposure to asbestos and smoking habits, were taken. A total of 508 cases, 492 males and 16 females, were found. Eighty per cent were smokers, which was more than expected, and 80% confirmed exposure to asbestos. The frequency of pleural plaques was found to increase steadily with the years parallel to the increase in the use of asbestos which had started 30 years earlier. The pleural plaques showed gradual development and many finally calcified.