title: Childhood cancer and traffic-related air pollution exposure in pregnancy and early life.
abstract: BACKGROUND
  The literature on traffic-related air pollution and childhood cancers is inconclusive, and little is known on rarer cancer types.
  
  
  OBJECTIVE
  We sought to examine associations between childhood cancers and traffic-related pollution exposure.
  
  
  METHODS
  The present study included children < 6 years of age identified in the California Cancer Registry (born 1998-2007) who could be linked to a California birth certificate (n = 3,590). Controls were selected at random from California birthrolls (n = 80,224). CAlifornia LINE Source Dispersion Modeling, version 4 (CALINE4) was used to generate estimates of local traffic exposures for each trimester of pregnancy and in the first year of life at the address indicated on the birth certificate. We checked our findings by additionally examining associations with particulate matter (≤ 2.5 μm in aerodynamic diameter; PM2.5) pollution measured by community-based air pollution monitors, and with a simple measure of traffic density.
  
  
  RESULTS
  With unconditional logistic regression, a per interquartile range increase in exposure to traffic-related pollution during the first trimester (0.0538 ppm carbon monoxide, estimated using CALINE4) was associated with acute lymphoblastic leukemia [ALL; first trimester odds ratio (OR) = 1.05; 95% CI: 1.01, 1.10]; germ cell tumors (OR = 1.16; 95% CI: 1.04, 1.29), particularly teratomas (OR = 1.26; 95% CI: 1.12, 1.41); and retinoblastoma (OR = 1.11; 95% CI: 1.01, 1.21), particularly bilateral retinoblastoma (OR = 1.16; 95% CI: 1.02, 1.33). Retinoblastoma was also associated with average PM2.5 concentrations during pregnancy, and ALL and teratomas were associated with traffic density near the child's residence at birth.
  
  
  CONCLUSIONS
  We estimated weak associations between early exposure to traffic pollution and several childhood cancers. Because this is the first study to report on traffic pollution in relation to retinoblastoma or germ cell tumors, and both cancers are rare, these findings require replication in other studies.
authors.affiliation: Department of Epidemiology, School of Public Health, University of California, Los Angeles, Los Angeles, California, USA.
authors.forename: Julia E
authors.initials: JE
authors.lastname: Heck
authors.forename: Jun
authors.initials: J
authors.lastname: Wu
authors.forename: Christina
authors.initials: C
authors.lastname: Lombardi
authors.forename: Jiaheng
authors.initials: J
authors.lastname: Qiu
authors.forename: Travis J
authors.initials: TJ
authors.lastname: Meyers
authors.forename: Michelle
authors.initials: M
authors.lastname: Wilhelm
authors.forename: Myles
authors.initials: M
authors.lastname: Cockburn
authors.forename: Beate
authors.initials: B
authors.lastname: Ritz
mesh_terms: D000393:Air Pollutants / Q000032:analysis / Q000633:toxicity*; D002140:California / Q000453:epidemiology; D002675:Child, Preschool; D004781:Environmental Exposure / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D016015:Logistic Models; D009369:Neoplasms / Q000453:epidemiology* / Q000209:etiology*; D016017:Odds Ratio; D011247:Pregnancy; D012307:Risk Factors; D001335:Vehicle Emissions / Q000032:analysis / Q000633:toxicity*
chemical_list: D000393:Air Pollutants; D001335:Vehicle Emissions
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