A high incidence of cancer of the respiratory tract has been reported among former workers in a poison gas manufacturing plant which operated on Ohkunojima from 1927 to 1945. This report provides evidence of a high incidence of chromosome abnormality and sister chromatid exchange (SCE) rate among the former workers, as well as cytogenetic changes in two patients among the former workers with chronic myelocytic leukemia (CML). A chromosome study of seven former workers with chronic bronchitis

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... ealed a stable type of aberration, the average abnormality being 10.9 +/- 4.4 percent, which is equivalent to those of atomic bomb survivors exposed at 1.2 km from the hypocenter. The SCE rate observed in 16 former workers ranged from 4.9 +/- 2.1 to 17.8 +/- 3.9, which was significantly higher than in the control group (p < 0.03). One of the CML patients showed an extremely high percentage of missing Y chromosomes along with t(9;22) translocation which is a specific chromosome aberration for the disease. Furthermore, the patient had almost a 3 times higher SCE rate compared to the control group and a high incidence of chromosome abnormality (12.1%) of the peripheral lymphocytes. These results suggest that the development of leukemia in this patient was strongly related to poison gas exposure.