title: Ambient air pollution and preterm birth: A prospective birth cohort study in Wuhan, China.
abstract: OBJECTIVE
  Although studies in western countries suggest that ambient air pollution is positively associated with adverse pregnancy outcomes, the upper levels of pollutant exposures have been relatively low, thus eroding confidence in the conclusions. Meanwhile, in Asia, where upper levels of exposure have been greater, there have been limited studies of the association between air pollution and adverse pregnancy outcomes.
  
  
  OBJECTIVE
  The primary objective was to evaluate whether high levels of pollution, including particulate matter pollution with a mass median aerodynamic diameter of less than 2.5 μm (PM2.5) and 10 μm (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), ozone (O3), and carbon monoxide (CO) are related to increased occurrence of preterm birth (PTB).
  
  
  METHODS
  We conducted a population-based study in Wuhan, China in a cohort of 95,911 live births during a two-year period from 2011 to 2013. The exposure was estimated based on daily mean concentrations of pollutants estimated using the pollutants' measurements from the nine closest monitors. Logistic regressions were performed to determine the relationships between exposure to each of the pollutants during different pregnancy periods and PTB while controlling for key covariates.
  
  
  RESULTS
  We found 3% (OR=1.03; 95% CI: 1.02, 1.05), 2% (OR=1.02; 95% CI: 1.02, 1.03), 15% (OR=1.15; 95% CI: 1.11, 1.19), and 5% (OR=1.05; 95% CI: 1.02, 1.07) increases in risk of PTB with each 5-μg/m(3) increase in PM2.5 and PM10 concentrations, 100-μg/m(3) increase in CO concentrations, and 10-μg/m(3) increase in O3 concentrations, respectively. There was negligible evidence for associations for SO2 and NO2. The effects from two-pollutant models were similar to the estimated effects from single pollutant models. No critical exposure windows were identified consistently: the strongest effect for PTB was found in the second trimester for PM2.5, PM10, and CO, but for SO2 it was in the first trimester, second month, and third month. For NO2 it was in the first trimester and second month, and for O3, the third trimester.
  
  
  CONCLUSIONS
  Findings reveal an association between air pollutants and PTB. However, more toxicological studies and prospective cohort studies with improved exposure assessments are needed to establish causality related to specific pollutants.
authors.affiliation: College for Public Health and Social Justice, Saint Louis University, Salus Center/Room 473, 3545 Lafayette Avenue, Saint Louis, MO 63104, USA. Electronic address: zqian2@slu.edu.
authors.forename: Zhengmin
authors.initials: Z
authors.lastname: Qian
authors.affiliation: Wuhan Environmental Monitoring Center, 422 Xinhua Road, Jianghan District, Wuhan 430015, China.
authors.forename: Shengwen
authors.initials: S
authors.lastname: Liang
authors.affiliation: Wuhan Medical and Health Center for Women and Children, 100 Hongkong Road, Jiangan District, Wuhan 430015, China.
authors.forename: Shaoping
authors.initials: S
authors.lastname: Yang
authors.affiliation: College for Public Health and Social Justice, Saint Louis University, Salus Center/Room 473, 3545 Lafayette Avenue, Saint Louis, MO 63104, USA.
authors.forename: Edwin
authors.initials: E
authors.lastname: Trevathan
authors.affiliation: Wuhan Environmental Monitoring Center, 422 Xinhua Road, Jianghan District, Wuhan 430015, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Huang
authors.affiliation: Wuhan Medical and Health Center for Women and Children, 100 Hongkong Road, Jiangan District, Wuhan 430015, China.
authors.forename: Rong
authors.initials: R
authors.lastname: Yang
authors.affiliation: College for Public Health and Social Justice, Saint Louis University, Salus Center/Room 473, 3545 Lafayette Avenue, Saint Louis, MO 63104, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.affiliation: Wuhan Environmental Monitoring Center, 422 Xinhua Road, Jianghan District, Wuhan 430015, China.
authors.forename: Ke
authors.initials: K
authors.lastname: Hu
authors.affiliation: Wuhan Medical and Health Center for Women and Children, 100 Hongkong Road, Jiangan District, Wuhan 430015, China.
authors.forename: Yiming
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: College for Public Health and Social Justice, Saint Louis University, Salus Center/Room 473, 3545 Lafayette Avenue, Saint Louis, MO 63104, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Vaughn
authors.affiliation: Wuhan Environmental Monitoring Center, 422 Xinhua Road, Jianghan District, Wuhan 430015, China.
authors.forename: Longjiao
authors.initials: L
authors.lastname: Shen
authors.affiliation: Wuhan Medical and Health Center for Women and Children, 100 Hongkong Road, Jiangan District, Wuhan 430015, China.
authors.forename: Wenjin
authors.initials: W
authors.lastname: Liu
authors.affiliation: Wuhan Environmental Monitoring Center, 422 Xinhua Road, Jianghan District, Wuhan 430015, China.
authors.forename: Pu
authors.initials: P
authors.lastname: Li
authors.affiliation: College for Public Health and Social Justice, Saint Louis University, Salus Center/Room 473, 3545 Lafayette Avenue, Saint Louis, MO 63104, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Ward
authors.affiliation: Wuhan Medical and Health Center for Women and Children, 100 Hongkong Road, Jiangan District, Wuhan 430015, China.
authors.forename: Li
authors.initials: L
authors.lastname: Yang
authors.affiliation: Wuhan Medical and Health Center for Women and Children, 100 Hongkong Road, Jiangan District, Wuhan 430015, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Wuhan Medical and Health Center for Women and Children, 100 Hongkong Road, Jiangan District, Wuhan 430015, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.affiliation: School of Public Health, Sun Yat-sen University, 74 Zhongshan 2nd Road, Yuexiu District, Guangzhou 510080, China.
authors.forename: Guanghui
authors.initials: G
authors.lastname: Dong
authors.affiliation: School of Public Health, Brown University, 121 South Main Street, Providence, RI 02912, USA.
authors.forename: Tongzhang
authors.initials: T
authors.lastname: Zheng
authors.affiliation: School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, 13 Hangkong Road, Qiaokou District, Wuhan 430030, China.
authors.forename: Shunqing
authors.initials: S
authors.lastname: Xu
authors.affiliation: Wuhan Medical and Health Center for Women and Children, 100 Hongkong Road, Jiangan District, Wuhan 430015, China. Electronic address: mchwhzb@163.com.
authors.forename: Bin
authors.initials: B
authors.lastname: Zhang
mesh_terms: D000328:Adult; D000393:Air Pollutants / Q000009:adverse effects / Q000032:analysis; D000397:Air Pollution / Q000009:adverse effects* / Q000032:analysis; D002248:Carbon Monoxide / Q000009:adverse effects / Q000032:analysis; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D009585:Nitrogen Dioxide / Q000009:adverse effects / Q000032:analysis; D016017:Odds Ratio; D010126:Ozone / Q000009:adverse effects / Q000032:analysis; D052638:Particulate Matter / Q000009:adverse effects / Q000032:analysis; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology*; D011446:Prospective Studies; D013458:Sulfur Dioxide / Q000009:adverse effects / Q000032:analysis; D055815:Young Adult
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D013458:Sulfur Dioxide; D010126:Ozone; D002248:Carbon Monoxide; D009585:Nitrogen Dioxide
keywords: Air pollution; Birth cohort; Preterm birth; Wuhan