A historical cohort study on mortality of shipyard workers exposed to asbestos.

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To investigate the effect of occupational asbestos exposure on causes of deaths among shipyard workers, 190 male employees, who worked as boiler mechanics or insulators for more than six months after entering a shiphard company in Yokosuka, Japan in the period between 1947 and 1971, were followed. The employees themselves or their bereaved families were traced and 182 of them (95.8%) were successfully located ; 114 of 120 boiler mechanics and 68 of 69 insulators. On average 182 employees initiated the job at the age of 34.9 (SD 10.2) and their employment duration was 14.1 (SD 10.3) years. In-person interviews with structured closed-ended questionnaires found that 17.6% of the respondents never smoked, 37.2% quitted smoking and 45.2% currently smoked. Till the end of 1995 ninety-seven workers had died and we classified their underlying causes reported in death certificates into the codes ruled by ICD 10. Deaths from all cancers showed the highest frequency of 27 including 10 cases of lu … More ng cancer. Cause-specific standardized mortality ratios (SMRs) were calculated using tables of five-age-specific mortality rates of the causes for all Japanese men and the sum of person-years of the subjects tabulated into five-age and five-calendar year subgroups between 1947 and 1995. We also calculated confidence intervals (C.I.) of SMRs based on Poisson distribution. A total of 3918 person-years were obtained from the boiler mechanics. SMRs of mesothelium, malignant neoplasm of peritoneum, heart diseases other than ischemic and rheumatic origin, and pneumoconiosis for the mechanics showed statistically higher values than unity, 58.8 [95%C.I. : 3.0-338.6], 24.4 [1.2-140.4], 2.2 [1.1-4.2] and 65.2 [17.8-191.5], respectively. We obtained 2230 person-years from the insulators and their SMRs of lung cancer and pneumoconiosis were 3.0 [1.2-7.1] and 38.5 [2.0-221.4], respectively, which were significantly higher than unity. These results indicated that occupational asbestos exposure increased the risk of developing lung cancer, mesothelium and pneumoconiosis. Less