title: Residential traffic exposure and childhood leukemia: a systematic review and meta-analysis.
abstract: BACKGROUND
  Exposure to elevated concentrations of traffic-related air pollutants in the near-road environment is associated with numerous adverse human health effects, including childhood cancer, which has been increasing since 1975. Results of individual epidemiologic studies have been inconsistent. Therefore, a meta-analysis was performed to examine the association between residential traffic exposure and childhood cancer.
  
  
  METHODS
  Studies published between January 1980 and July 2011 were retrieved from a systematic search of 18 bibliographic databases. Nine studies meeting the inclusion criteria were identified. Weighted summary ORs were calculated using a random effects model for outcomes with four or more studies. Subgroup and sensitivity analyses were performed.
  
  
  RESULTS
  Childhood leukemia was positively associated (summary OR=1.53, 95% CI=1.12, 2.10) with residential traffic exposure among seven studies using a postnatal exposure window (e.g., childhood period or diagnosis address) and there was no association (summary OR=0.92, 95% CI=0.78, 1.09) among four studies using a prenatal exposure window (e.g., pregnancy period or birth address). There were too few studies to analyze other childhood cancer outcomes.
  
  
  CONCLUSIONS
  Current evidence suggests that childhood leukemia is associated with residential traffic exposure during the postnatal period, but not during the prenatal period. Additional well-designed epidemiologic studies that use complete residential history to estimate traffic exposure, examine leukemia subtypes, and control for potential confounding factors are needed to confirm these findings. As many people reside near busy roads, especially in urban areas, precautionary public health messages and interventions designed to reduce population exposure to traffic might be warranted.
authors.affiliation: Office of Public Health Scientific Services, Division of Epidemiology, Analysis, and Library Services, Analytic Tools and Methods Branch, CDC, Atlanta, Georgia. Electronic address: veb6@cdc.gov.
authors.forename: Vickie L
authors.initials: VL
authors.lastname: Boothe
authors.affiliation: National Center for Environmental Health, Division of Environmental Hazards and Health Effects, Air Pollution and Respiratory Health Branch, CDC, Atlanta, Georgia.
authors.forename: Tegan K
authors.initials: TK
authors.lastname: Boehmer
authors.affiliation: National Center for Environmental Health, Division of Emergency and Environmental Health Services, Healthy Community Design Initiative, CDC, Atlanta, Georgia.
authors.forename: Arthur M
authors.initials: AM
authors.lastname: Wendel
authors.affiliation: National Center for Environmental Health, Division of Environmental Hazards and Health Effects, Air Pollution and Respiratory Health Branch, CDC, Atlanta, Georgia.
authors.forename: Fuyuen Y
authors.initials: FY
authors.lastname: Yip
mesh_terms: D000293:Adolescent; D000393:Air Pollutants / Q000633:toxicity*; D002648:Child; D002675:Child, Preschool; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D006798:Housing; D006801:Humans; D007223:Infant; D007938:Leukemia / Q000139:chemically induced / Q000453:epidemiology*; D018986:Motor Vehicles; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000453:epidemiology; D018570:Risk Assessment
chemical_list: D000393:Air Pollutants