Pleural plaques and cigarette smoking in asbestos workers.

In a survey of 45 men aged 40 or over who had worked five years or more in an asbestos manufacturing plant, the prevalence of pleural plaques was studied with respect to age, duration of asbestos exposure, estimated cumulative asbestos dose, and smoking habit. Plaques were found in 38 to 53% of the men, depending on the interpretation of the chest film reader. Cigarette habit appeared to be the most important factor; the prevalence was lowest in non-smokers, intermediate in current smokers, and particularly high in exsmokers. There was some confounding of this relationship by estimated cumulative asbestos dose but such confounding did not seem to be sufficient to explain fully the relationship between the prevalence of plaques and smoking habit. Both factors must be considered in studies of the risk of pleural plaques in asbestos workers.