肺癌とその環境因子

Abstract

Besides clinically recognized lung cancers, a careful histological examination of the respiratory tract of autopsied men who were previously exposed to mustard-gas revealed significantly higher frequency of abnormal lesions including dysplasia and microscopical early cancer within the bronchial epithelium. These findings were encountered in not only individuals exposed to the gas and suffered later from clinical lung cancer, but also those exposed to the gas and suffered later from various diseases other than lung cancer, and also those not exposed to the gas but suffered from clinical lung cancer. Smoking effects appeared to be also significant in lung cancer development. According to the investigation of the Radiation Effects Research Foundation, the relative risk of lung cancer increased significantly with radiation dose in A-bomb survivors in Hiroshima and Nagasaki. Small-cell type lung cancer showed somewhat greater sensitivity than other types of lung cancer. An annual relative frequency of malignant mesothelioma in the major diagnoses of all autopsy cases has been increasing dramatically during the past 2 decades in Hiroshima district. The majority of examined cases with malignant mesotheliomas showed a significant accumulation of asbestos bodies within pulmonary alveoli. Ninety-nine per cent of our recent autopsy cases showed an intraalveolar deposition of asbestos bodies and proportional distribution of cases with dense exposure to asbestos appeared to be greater than previous investigations reported by others from other districts. Aforementioned unfortunate phenomena in regard with either chemical or radiation carcinogenesis, admonish us to be wise enough to make an urgent effort for the exclusion of such an exogenous carcinogenic agent as asbestos from our living circumstances.