title: The associations between environmental quality and preterm birth in the United States, 2000-2005: a cross-sectional analysis.
abstract: BACKGROUND
  Many environmental factors have been independently associated with preterm birth (PTB). However, exposure is not isolated to a single environmental factor, but rather to many positive and negative factors that co-occur. The environmental quality index (EQI), a measure of cumulative environmental exposure across all US counties from 2000-2005, was used to investigate associations between ambient environment and PTB.
  
  
  METHODS
  With 2000-2005 birth data from the National Center for Health Statistics for the United States (n = 24,483,348), we estimated the association between increasing quintiles of the EQI and county-level and individual-level PTB; we also considered environmental domain-specific (air, water, land, sociodemographic and built environment) and urban-rural stratifications.
  
  
  RESULTS
  Effect estimates for the relationship between environmental quality and PTB varied by domain and by urban-rural strata but were consistent across county- and individual-level analyses. The county-level prevalence difference (PD (95% confidence interval) for the non-stratified EQI comparing the highest quintile (poorest environmental quality) to the lowest quintile (best environmental quality) was -0.0166 (-0.0198, -0.0134). The air and sociodemographic domains had the strongest associations with PTB; PDs were 0.0196 (0.0162, 0.0229) and -0.0262 (-0.0300, -0.0224) for the air and sociodemographic domain indices, respectively. Within the most urban strata, the PD for the sociodemographic domain index was 0.0256 (0.0205, 0.0307). Odds ratios (OR) for the individual-level analysis were congruent with PDs.
  
  
  CONCLUSIONS
  We observed both strong positive and negative associations between measures of broad environmental quality and preterm birth. Associations differed by rural-urban stratum and by the five environmental domains. Our study demonstrates the use of a large scale composite environment exposure metric with preterm birth, an important indicator of population health and shows potential for future research.
authors.affiliation: Oak Ridge Institute for Science and Education at the U.S. Environmental Protection Agency, National Center for Environmental Assessment, U.S. Environmental Protection Agency, Research Triangle Park, NC, USA. rappazzo.kristen@epa.gov.
authors.forename: Kristen M
authors.initials: KM
authors.lastname: Rappazzo
authors.affiliation: School of Community Health; College of Urban and Public Affairs, Portland State University, Portland, OR, USA. lymesser@pdx.edu.
authors.forename: Lynne C
authors.initials: LC
authors.lastname: Messer
authors.affiliation: Division of Environmental and Occupational Health Sciences, School of Public Health, University of Illinois, Chicago, Chicago, IL, USA. jjagai2@uic.edu.
authors.forename: Jyotsna S
authors.initials: JS
authors.lastname: Jagai
authors.affiliation: Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, USA. clgray@email.unc.edu.|Oak Ridge Institute for Science and Education at the U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Chapel Hill, NC, USA. clgray@email.unc.edu.
authors.forename: Christine L
authors.initials: CL
authors.lastname: Gray
authors.affiliation: Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, USA. sgrabich@email.unc.edu.|Oak Ridge Institute for Science and Education at the U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Chapel Hill, NC, USA. sgrabich@email.unc.edu.
authors.forename: Shannon C
authors.initials: SC
authors.lastname: Grabich
authors.affiliation: National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Chapel Hill, NC, USA. lobdell.danelle@epa.gov.
authors.forename: Danelle T
authors.initials: DT
authors.lastname: Lobdell
mesh_terms: D003430:Cross-Sectional Studies; D004781:Environmental Exposure / Q000009:adverse effects*; D004785:Environmental Pollutants / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D016017:Odds Ratio; D011203:Poverty / Q000706:statistics & numerical data; D011247:Pregnancy; D047928:Premature Birth / Q000139:chemically induced* / Q000453:epidemiology; D015995:Prevalence; D012307:Risk Factors; D012424:Rural Population / Q000706:statistics & numerical data; D014481:United States / Q000453:epidemiology; D014505:Urban Population / Q000706:statistics & numerical data
chemical_list: D004785:Environmental Pollutants