A historical cohort study of carpenters exposed to low dose asbestos in a shipyard

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Two historical cohort studies were conducted to investigate the effect of low dose asbestos exposure on mortality in occupational settings. One cohort consisted of 153 male carpenters worked as of 1976 in a shipyard. They had been exposed to asbestos intermittently for a short period when building rooms in a ship. The other cohort enrolled 199 workers (140 males and 59 females) in an arsenopyrite mine employed at some time between 1946 and 1958, the cohort which was set for a 'positive' control group to compare the magnitude of carcinogenecity between asbestos and arsenic. The carpenters were followed from 1976 to May 31, 1999 and 145 of the 153 study subjects were identified. 20 of them had died. The SMR of overall deaths, adjusted to the mortality in 5-year age and calendar year in a 5-year period in general Japanese populations, was 1.2, whose 95 % confidence interval included the null value. Three carpenters died from malignant mesothelioma. Other causes of death, including lung ca … More ncer, did not show increased SMRs, however. These results contrasted with those among the laggers exposed to asbestos much higher than the carpenters in our previous study. The laggers showed an increased SMR of 3.2 of lung cancer but no death from mesothelioma. The miners were followed from the date of employment till Dec 31, 1998. A total of 127 of 140 males and 55 of 57 females were successfully identified. 77 males had died. Of them 11 died form lung cancer. Subcohort analysis by job revealed that eight of 34 refiners in a mine died form the cancer and this occurrence corresponded to the SMR of 19 (99 % C.I. : 6.9-44.9). The refiners refined arsenopyrite ores and collected powdered arsenic, and accordingly were exposed arsenic heavily for five years in average. No elevated SMRs of any diseases were obtained in the female workers. The present results indicated that asbestos might have a lower carcinogenecity for lung cancer compared with arsenic, and that low dose exposure of asbestos could develop malignant mesothelioma rather than lung cancer. Less