Population-based cohort study on health effects of asbestos exposure in Japan

Occupational asbestos exposure occurs in many workplaces and is a well-known cause of mesothelioma and lung cancer. However, the association between nonoccupational asbestos exposure and those diseases is not clearly described. The aim of this study was to investigate cause-specific mortality among the residents of Amagasaki, a city in Japan with many asbestos factories, and evaluate the potential excess mortality due to established and suspected asbestos-related diseases. The study population consisted of 143 929 residents in Amagasaki City before 1975 until 2002, aged 40 years or older on January 1, 2002. Follow-up was carried out from 2002 to 2015. Standardized mortality ratio (SMR) with its 95% confidence interval (CI) was calculated by sex, using the mortality rate of the Japanese population as reference. A total of 38 546 deaths (including 303 from mesothelioma and 2683 from lung cancer) were observed. The SMRs in the long-term residents’ cohort were as follows: death due to all causes, 1.12 (95% CI, 1.10-1.13) in men and 1.07 (95% CI, 1.06-1.09) in women; lung cancer, 1.28 (95% CI, 1.23-1.34) in men and 1.23 (95% CI, 1.14-1.32) in women; and mesothelioma, 6.75 (95% CI, 5.83-7.78) in men and 14.99 (95% CI, 12.34-18.06) in women. These SMRs were significantly higher than expected. The increased SMR of mesothelioma suggests the impact of occupational asbestos exposure among men and nonoccupational asbestos exposure among women in the long-term residents’ cohort. In addition, the high level of excess mortality from mesothelioma has persisted, despite the mixture of crocidolite and chrysotile no longer being used for three or four decades.