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Mustard gas exposure and mortality among retired workers at a poisonous gas factory in Japan: a 57-year follow-up cohort study
  1. Kenichi Mukaida1,
  2. Noboru Hattori1,
  3. Hiroshi Iwamoto1,
  4. Yojiro Onari2,
  5. Yoshifumi Nishimura3,
  6. Keiichi Kondoh3,
  7. Tomoyuki Akita4,
  8. Junko Tanaka4,
  9. Nobuoki Kohno1
  1. 1Department of Molecular and Internal Medicine, Institute of Biomedical Sciences, Hiroshima University, Hiroshima, Japan
  2. 2Department of Respiratory Medicine, Mazda Hospital, Hiroshima, Japan
  3. 3Tadanoumi Branch Hospital, Kure Kyosai Hospital, Takehara, Japan
  4. 4Department of Epidemiology, Infectious Disease Control and Prevention, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
  1. Correspondence to Dr Noboru Hattori, Department of Molecular and Internal Medicine, Institute of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-Ku, Hiroshima 734-8551, Japan; nhattori{at}hirsohima-u.ac.jp

Abstract

Objectives Mustard gas (MG) has been the most widely used chemical warfare agent in the past century. However, few but conflicting data exist on the effects of MG exposure on long-term mortality. We investigated MG-related mortality in retired workers at a poisonous gas factory.

Methods We assessed mortality rates among 2392 male and 1226 female workers, whose vital status could be determined through 31 December 2009, at a poisonous gas factory operating from 1929 to 1945 in Okuno-jima, Japan. The analysis employed standardised mortality ratios (SMRs) calculated using national and prefectural references and a Cox proportional hazard regression model. Applying the Kaplan-Meier method, we compared cumulative death rates in the study cohort stratified by an ‘Okuno-jima MG Index’ which represented the product of HRs derived for job category and length of service.

Results Among male workers, we found significant excesses in mortality from upper respiratory tract cancer (SMR 3.06), liver cancer (1.67), lung cancer (2.01) and chronic bronchitis/emphysema (4.84) compared with the national population, as well as stomach cancer (1.20) versus the Hiroshima Prefecture population. When stratified into 3 subgroups by the Okuno-jima MG Index, those with a higher Okuno-jima MG Index had significantly higher cumulative rates of death from respiratory cancer and chronic bronchitis/emphysema.

Conclusions MG exposure significantly increases the long-term risk of death from respiratory cancer and chronic bronchitis/emphysema. The Okuno-jima MG Index may be a useful indicator for estimating cumulative MG exposure.

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