title: Outdoor air pollution and term low birth weight in Japan.
abstract: BACKGROUND
  Evidence has accumulated on the association between ambient air pollution and adverse birth outcomes. However, most of the previous studies were conducted in geographically distinct areas and suffer from lack of important potential covariates. We examined the effect of ambient air pollution on term low birth weight (LBW) using data from a nationwide population-based longitudinal survey in Japan that began in 2001.
  
  
  METHODS
  We restricted participants to term singletons (n=44,109). Air pollution concentrations during the 9months before birth were obtained at the municipality level and were assigned to the participants who were born in the corresponding municipality. We conducted multilevel logistic regression analyses adjusting for individual and municipality-level variables.
  
  
  RESULTS
  We found that air pollution exposure during pregnancy was positively associated with the risk of term LBW. In the fully adjusted models, odds ratios following one interquartile range increase in each pollutant were 1.09 (95% confidence interval: 1.00, 1.19) for suspended particulate matter (SPM), 1.11 (0.99, 1.26) for nitrogen dioxide (NO2), and 1.71 (1.18, 2.46) for sulfur dioxide (SO2). Specifically, effect estimates for SPM and NO2 exposure at the first trimester were higher than those at other trimesters, while SO2 was associated with the risk at all trimesters. Nonsmoking mothers were more susceptible to SPM and NO2 exposure compared with smoking mothers.
  
  
  CONCLUSIONS
  Ambient air pollution increases the risk of term LBW in a nationally representative sample in Japan.
authors.affiliation: Department of Human Ecology, Graduate School of Environmental and Life Science, Okayama University, Okayama, Japan. Electronic address: yorichan@md.okayama-u.ac.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yorifuji
authors.affiliation: Department of Public Health and Public Policy, Institute of Biomedical and Health Sciences, Hiroshima University, Japan.
authors.forename: Saori
authors.initials: S
authors.lastname: Kashima
authors.affiliation: Department of Epidemiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Doi
mesh_terms: D000328:Adult; D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000032:analysis; D005260:Female; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D007564:Japan; D008137:Longitudinal Studies; D008297:Male; D018811:Maternal Exposure; D009585:Nitrogen Dioxide / Q000032:analysis; D052638:Particulate Matter / Q000032:analysis; D011247:Pregnancy; D011264:Pregnancy Trimesters; D013458:Sulfur Dioxide / Q000032:analysis
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D013458:Sulfur Dioxide; D009585:Nitrogen Dioxide
keywords: Air pollution; Low birth weight; Nitrogen dioxide; Particulate matter; Pregnancy outcomes; Sulfur dioxide