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Long-term exposure to traffic-related air pollution and mortality in Shizuoka, Japan
  1. Takashi Yorifuji1,
  2. Saori Kashima2,
  3. Toshihide Tsuda2,
  4. Soshi Takao1,
  5. Etsuji Suzuki1,
  6. Hiroyuki Doi1,
  7. Masumi Sugiyama3,
  8. Kazuko Ishikawa-Takata4,
  9. Toshiki Ohta5
  1. 1Department of Epidemiology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
  2. 2Okayama University Graduate School of Environmental Science, Okayama, Japan
  3. 3Shizuoka Health Institute, Shizuoka, Japan
  4. 4Program of Health Promotion and Exercise, National Institute of Health and Nutrition, Tokyo, Japan
  5. 5National Hospital for Geriatric Medicine, National Center for Geriatrics and Gerontology, Aichi, Japan
  1. Correspondence to Takashi Yorifuji, Department of Epidemiology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama city, Okayama Pref. 700-8558, Japan; yorichan{at}


Objectives The number of studies investigating the health effects of long-term exposure to air pollution is increasing, however, most studies have been conducted in Western countries. The health status of Asian populations may be different to that of Western populations and may, therefore, respond differently to air pollution exposure. Therefore, we evaluated the health effects of long-term exposure to traffic-related air pollution in Shizuoka, Japan.

Methods Individual data were extracted from participants of an ongoing cohort study. A total of 14 001 older residents, who were randomly chosen from all 74 municipalities of Shizuoka, completed questionnaires and were followed from December 1999 to March 2006. Individual nitrogen dioxide exposure data, as an index for traffic-related exposure, were modelled using a land use regression model. We assigned participants an estimated concentration of nitrogen dioxide exposure during 2000–2006. We then estimated the adjusted HR and their CI for a 10 μg/m3 increase in exposure to nitrogen dioxide for all-cause or cause-specific mortality.

Results The adjusted HR for all-cause mortality was 1.02 (95% CI 0.96 to 1.08). Regarding cause-specific mortality, the adjusted HR for cardiopulmonary mortality was 1.16 (95% CI 1.06 to 1.26); in particular the adjusted HR for ischaemic heart disease mortality was 1.27 (95% CI 1.02 to 1.58) and for pulmonary disease mortality it was 1.19 (95% CI 1.02 to 1.38). Furthermore, among non-smokers, a 10 μg/m3 increase in nitrogen dioxide was associated with a higher risk for lung cancer mortality (HR 1.30, 95% CI 0.85 to 1.93).

Conclusion Long-term exposure to traffic-related air pollution, indexed by nitrogen dioxide concentration, increases the risk of cardiopulmonary mortality, even in a population with a relatively low body mass index and increases the risk of lung cancer mortality in non-smokers.

  • Air pollution
  • nitrogen dioxide
  • environmental exposure
  • myocardial ischaemia
  • lung neoplasms

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  • Funding This work was supported by a Health and Labour Sciences Research Grant for Comprehensive Research on Ageing and Health.

  • Competing interests None declared.

  • Ethics approval This study was conducted with the approval of the Institutional Review Board of Okayama Graduate School of Medicine, Dentistry and Pharmaceutical Sciences.

  • Provenance and peer review Not commissioned; externally peer reviewed.