[A comparative study on the prevalence of pleural thickness related with asbestos exposures. A comparison between urban and rural districts using miniature X-ray films (author's transl)].

Using miniature films for mass tuberculosis examination of inhabitants, a comparison was made of the prevalence of pleural thickening between urban and rural districts in Japan. The classification of pleural thickening mostly followed the criteria of Askergren and Szamosi. Age adjusted prevalences for male adults were 2.7% (Ys city) and 5.3% (Yk city) in urban districts, and 0.7% (Hokuriku district) in rural districts. In addition to the survey of these inhabitants, workers of a ship building factory in the urban district were examined. Age adjusted prevalence in this case was 7.3%. On the other hand, the prevalence for female adults were 0.2% (Ys city) and 0.4% (Yk city) in the urban districts, and 0.09% in the rural districts. The prevalence of pleural thickening showed a sharp increase after 60 years of age in male adults but not in female adults. It was confirmed that pleural calcification was a better diagnostic feature for distinguishing the difference of prevalence by areas.