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Fine-particulate Air Pollution from Diesel Emission Control and Mortality Rates in Tokyo: A Quasi-experimental Study

Yorifuji, Takashi; Kashima, Saori; Doi, Hiroyuki

doi: 10.1097/EDE.0000000000000546
Air Pollution

Background: Evidence linking air pollution with adverse health outcomes is accumulating. However, few studies have adopted a quasi-experimental design to evaluate whether decline in air pollution from regulatory action improves public health. We evaluated the effect of a diesel emission control ordinance introduced in 2003 on mortality rates in 23 wards of the Tokyo metropolitan area, Japan, from October 2000 to September 2012, taking into account change in mortality rates in a reference population (Osaka) with a introduction of such a regulation in 2009.

Methods: We obtained daily counts of all-cause and cause-specific mortality and concentrations of nitrogen dioxide (NO2) and particulate matter less than 2.5 μm in diameter (PM2.5) during the study period. We employed interrupted time-series analysis to analyze the data.

Results: Decline in NO2 during the study period was similar in the two areas, while decline in PM2.5 and the improvement in age-standardized mortality rates were greater in Tokyo’s 23 wards compared with Osaka. Even after adjusting for age-standardized mortality rates in Osaka, percent changes in mortality between the first 3-year interval (October 2000 to September 2003) and the last 3-year interval (October 2009 to September 2012) were −6.0% for all causes, −11% for cardiovascular disease, −10% for ischemic heart disease, −6.2% for cerebrovascular disease, −22% for pulmonary disease, and −4.9% for lung cancer. We did not observe a decline in mortality from other causes.

Conclusions: This quasi-experimental study in Tokyo suggests that emission control was associated with improvements in both air quality and health outcomes.

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From the aDepartment of Human Ecology, Graduate School of Environmental and Life Science, Okayama University, Okayama, Japan; bDepartment of Public Health and Public Policy, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan; and cDepartment of Epidemiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.

Submitted 16 September 2015; accepted 25 July 2016.

This study was supported in part by a Grant-in-Aid for Scientific Research (C) from the Japanese Ministry of Education, Culture, Sports, Science and Technology (No. 24510033) and Okayama University Top Young Researcher Award (No. 7100003281). The sponsor has had no involvement in the study design, the collection, analysis, and interpretation of data, the writing of the report, or the decision to submit the paper for publication.

The authors report no conflicts of interest.

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Correspondence: Takashi Yorifuji, Department of Human Ecology, Graduate School of Environmental and Life Science, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan. E-mail:

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