title: Traffic density and the risk of childhood leukemia in a Los Angeles case-control study.
abstract: OBJECTIVE
  To investigate the relationship between traffic density and the risk of childhood leukemia.
  
  
  METHODS
  The study group consisted of 212 cases and 202 controls from the London et al. (1991) study of childhood leukemia conducted in the Los Angeles area during 1978 to 1984. Using GIS methods, traffic counts on all streets within 1500 feet of each subject's residence of longest duration were determined. From these counts, an integrated distance-weighted traffic density measure was calculated for each subject for use as the analytic variable. Additional information, including magnetic fields and wire-code, was obtained from the original case-control study. Association between traffic density and leukemia, and confounding and effect modification by other variables, were assessed using standard matched case-control analyses.
  
  
  RESULTS
  Although the unadjusted traffic density-childhood leukemia rate ratios were slightly elevated, this weak association was explained by confounding by wire code. Wire code remained associated with leukemia after controlling for traffic density. There was little evidence of effect modification between traffic density and magnetic fields, wire code or other variables.
  
  
  CONCLUSIONS
  There is no evidence of an association of traffic density with childhood leukemia in the Los Angeles case-control study.
authors.affiliation: Department of Preventive Medicine, University of Southern California, Los Angeles, CA 90089-9011, USA. langholz@hsc.usc.edu
authors.forename: Bryan
authors.initials: B
authors.lastname: Langholz
authors.forename: Kristie L
authors.initials: KL
authors.lastname: Ebi
authors.forename: Duncan C
authors.initials: DC
authors.lastname: Thomas
authors.forename: John M
authors.initials: JM
authors.lastname: Peters
authors.forename: Stephanie J
authors.initials: SJ
authors.lastname: London
mesh_terms: D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007938:Leukemia / Q000453:epidemiology / Q000209:etiology*; D015141:Los Angeles / Q000453:epidemiology; D018986:Motor Vehicles / Q000706:statistics & numerical data*; D012307:Risk Factors; D001335:Vehicle Emissions / Q000009:adverse effects
chemical_list: D001335:Vehicle Emissions