title: No association between traffic density and risk of childhood leukemia: a meta-analysis.
abstract: BACKGROUND
  While many studies have concluded that local traffic density is positively associated with childhood leukemia, the results are inconsistent. We therefore performed a meta-analysis to assess the relationship between traffic density and the risk of childhood leukemia.
  
  
  METHODS
  A systematic literature review was carried out using PubMed, EMBASE, and the Cochrane Library from January 1979 to December 2013. We selected and assessed journal articles evaluating the relationship between local traffic density and the risk of leukemia in children. The analysis was carried out using STATA version 12.0.
  
  
  RESULTS
  A total of 11 articles, including 12 estimates of effect, were included in our meta-analysis. The summary effect size from the random-effects model, expressed as an odds ratio, was 1.03 (95% CI: 0.98-1.09, p=0.002). No significant association between traffic density and the risk of childhood leukemia was found. Similar conclusions were found on subgroup analysis.
  
  
  CONCLUSIONS
  The results of our meta-analysis suggested no association between traffic density and the risk of childhood leukemia. This implies that living in close proximity to roads with heavy traffic may not increase the risk of childhood leukemia. However, further high-quality prospective trials are needed to support these results.
authors.affiliation: Department of Laboratory Medicine, Anhui Provincial Hospital, Anhui Medical University, Hefei, China E-mail : xiaolingma@126.com.
authors.forename: Xiao-Xi
authors.initials: XX
authors.lastname: Sun
authors.forename: Shan-Shan
authors.initials: SS
authors.lastname: Zhang
authors.forename: Xiao-Ling
authors.initials: XL
authors.lastname: Ma
mesh_terms: D000293:Adolescent; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D004198:Disease Susceptibility / Q000209:etiology*; D004781:Environmental Exposure / Q000009:adverse effects*; D006801:Humans; D007938:Leukemia / Q000209:etiology*; D012306:Risk; D012307:Risk Factors