Serial radiological changes in workers and residents of wittenoom, western australia previously exposed to crocidolite

BACKGROUND: Asbestos was mined at Wittenoom from 1943 to 1966. Seven thousand workers and five thousand residents are documented to have been exposed to crocidolite. 1715 joined a program of cancer prevention using vitamin A between 1990 and 1996. AIM: To examine the effects of crocidolite exposure, initial plasma level of vitamin A and smoking on the onset and progression of asbestosis and diffuse pleural thickening. METHODS: All 1715 participants had plain chest Xray performed at entry and over 600 had > 1 follow-up film after > 1 year. All films were read independently according to the ILO classification by two experienced readers. Serum vitamin A was measured at entry by HPLC. Data were analysed by generalised estimating equation methods using SAS. RESULTS: Progression of asbestosis increased with age, time in the study and (log) cumulative crocidolite exposure and was less in females. Similar results were found for progression of diffuse pleural thickening: in addition people with higher plasma -carotene were less likely to progress. CONCLUSION: Non-malignant asbestos related diseases continue to progress thirty years after closure of the industry, are dose-related, and appear to be associated with initial levels of, p-carotene.