title: Decline of ambient air pollution levels due to measures to control automobile emissions and effects on the prevalence of respiratory and allergic disorders among children in Japan.
abstract: BACKGROUND
  In Japan, air pollution due to nitrogen oxides (NOx) and particulate matter (PM) has been gradually reduced since control measures based on the Automobile NOx/PM law were enforced beginning in 2001. The effects of decrease in air pollutants due to the control measures during the past decade on the prevalence of respiratory and allergic disorders such as asthma in children were evaluated.
  
  
  METHODS
  Using data of 618,973 children collected in 28 regions of Japan from 1997 to 2009, we evaluated whether reductions in the concentrations of nitrogen dioxide (NO2) and suspended particulate matter (SPM) contribute to the decrease in the prevalence of asthma, wheezing, bronchitis, allergic rhinitis, and atopic dermatitis by multiple linear regression analysis, including adjustments for related factors.
  
  
  RESULTS
  The annual rates of decrease in air pollution in the PM-law-enforced areas were 2.0 and 2.5 times higher for NO2 and SPM, respectively, compared with those in the non-enforced areas. The prevalence of asthma decreased significantly at -0.073% per year in the areas in which measures based on the Automobile NOx/PM law were taken but not in area where such measures were not applied. Multiple linear regression analysis showed a reduction in the ambient air pollution was significantly associated with a reduction in the prevalence of asthma, with a rate of 0.118% [95% confidence interval (CI): 0.012-0.225] per 1 ppb for NO2, and 0.050% [95% CI: 0.020-0.080] per 1 μg/m(3) for SPM. An increase in the ambient air pollution was associated with an increase in the prevalence of atopic dermatitis of 0.390% [95% CI: 0.107-0.673] per 1 ppb for NO2, 0.141% [95% CI: 0.058-0.224] per 1 μg/m(3) for SPM. The changes in the prevalence of wheezing and allergic rhinitis were not significantly correlated with changes in air pollutant concentrations.
  
  
  CONCLUSIONS
  The enforcement of measures to control automobile emissions based on the Automobile NOx/PM law was shown to have reduced air pollution and contributed to decreases in the prevalence of respiratory and allergic disorders in 3-year-old children.
authors.affiliation: Department of Public Health, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo 663-8501, Japan; Center for Environmental Information Science, Tokyo, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Hasunuma
authors.affiliation: Center for Environmental Information Science, Tokyo, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Ishimaru
authors.affiliation: Department of Public Health, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo 663-8501, Japan.
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Yoda
authors.affiliation: Department of Public Health, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo 663-8501, Japan. Electronic address: shima-m@hyo-med.ac.jp.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Shima
mesh_terms: D000397:Air Pollution / Q000009:adverse effects / Q000331:legislation & jurisprudence* / Q000517:prevention & control; D002675:Child, Preschool; D006801:Humans; D006967:Hypersensitivity / Q000453:epidemiology* / Q000209:etiology; D007564:Japan / Q000453:epidemiology; D009585:Nitrogen Dioxide / Q000633:toxicity*; D052638:Particulate Matter / Q000633:toxicity*; D015995:Prevalence; D012120:Respiration Disorders / Q000453:epidemiology* / Q000209:etiology; D001335:Vehicle Emissions / Q000331:legislation & jurisprudence* / Q000517:prevention & control / Q000633:toxicity
chemical_list: D052638:Particulate Matter; D001335:Vehicle Emissions; D009585:Nitrogen Dioxide
keywords: Air pollution; Allergic disorder; Asthma; Automobile emissions; Health surveillance