title: Traffic-related air pollution and obesity formation in children: a longitudinal, multilevel analysis.
abstract: BACKGROUND
  Biologically plausible mechanisms link traffic-related air pollution to metabolic disorders and potentially to obesity. Here we sought to determine whether traffic density and traffic-related air pollution were positively associated with growth in body mass index (BMI = kg/m2) in children aged 5-11 years.
  
  
  METHODS
  Participants were drawn from a prospective cohort of children who lived in 13 communities across Southern California (N = 4550). Children were enrolled while attending kindergarten and first grade and followed for 4 years, with height and weight measured annually. Dispersion models were used to estimate exposure to traffic-related air pollution. Multilevel models were used to estimate and test traffic density and traffic pollution related to BMI growth. Data were collected between 2002-2010 and analyzed in 2011-12.
  
  
  RESULTS
  Traffic pollution was positively associated with growth in BMI and was robust to adjustment for many confounders. The effect size in the adjusted model indicated about a 13.6% increase in annual BMI growth when comparing the lowest to the highest tenth percentile of air pollution exposure, which resulted in an increase of nearly 0.4 BMI units on attained BMI at age 10. Traffic density also had a positive association with BMI growth, but this effect was less robust in multivariate models.
  
  
  CONCLUSIONS
  Traffic pollution was positively associated with growth in BMI in children aged 5-11 years. Traffic pollution may be controlled via emission restrictions; changes in land use that promote jobs-housing balance and use of public transit and hence reduce vehicle miles traveled; promotion of zero emissions vehicles; transit and car-sharing programs; or by limiting high pollution traffic, such as diesel trucks, from residential areas or places where children play outdoors, such as schools and parks. These measures may have beneficial effects in terms of reduced obesity formation in children.
authors.affiliation: Division of Environmental Health Sciences, School of Public Health, University of California, 50 University Hall MC7360, Berkeley, CA, USA. jerrett@berkeley.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Jerrett
authors.forename: Rob
authors.initials: R
authors.lastname: McConnell
authors.forename: Jennifer
authors.initials: J
authors.lastname: Wolch
authors.forename: Roger
authors.initials: R
authors.lastname: Chang
authors.forename: Claudia
authors.initials: C
authors.lastname: Lam
authors.forename: Genevieve
authors.initials: G
authors.lastname: Dunton
authors.forename: Frank
authors.initials: F
authors.lastname: Gilliland
authors.forename: Fred
authors.initials: F
authors.lastname: Lurmann
authors.forename: Talat
authors.initials: T
authors.lastname: Islam
authors.forename: Kiros
authors.initials: K
authors.lastname: Berhane
mesh_terms: D000393:Air Pollutants / Q000633:toxicity*; D015992:Body Mass Index; D002140:California / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D004781:Environmental Exposure; D004784:Environmental Monitoring; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008962:Models, Theoretical; D055361:Multilevel Analysis; D063766:Pediatric Obesity / Q000139:chemically induced / Q000453:epidemiology*; D011446:Prospective Studies; D001335:Vehicle Emissions / Q000633:toxicity*
chemical_list: D000393:Air Pollutants; D001335:Vehicle Emissions