title: Residential exposure to polychlorinated biphenyls and organochlorine pesticides and risk of childhood leukemia.
abstract: BACKGROUND
  Incidence of childhood leukemia in industrialized countries rose significantly during 1975-2004, and the reasons for the increase are not understood.
  
  
  OBJECTIVE
  We used carpet dust as an exposure indicator to examine the risk of childhood leukemia in relation to residential exposure to persistent organochlorine chemicals: six polychlorinated biphenyl (PCB) congeners and the pesticides alpha- and gamma-chlordane, p,p'-DDT (dichlorodiphenyltrichloroethane), p,p'-DDE (dichlorodiphenyldichloroethylene), methoxychlor, and pentachlorophenol.
  
  
  METHODS
  We conducted a population-based case-control study in 35 counties in northern and central California in 2001-2006. The study included 184 acute lymphocytic leukemia (ALL) cases 0-7 years of age and 212 birth certificate controls matched to cases by birth date, sex, race, and Hispanic ethnicity. We collected carpet dust samples from the room where the child spent the most time before diagnosis (similar date for controls) using a specialized vacuum.
  
  
  RESULTS
  Detection of any PCB congener in the dust conferred a 2-fold increased risk of ALL [odds ratio (OR) = 1.97; 95% confidence interval (CI), 1.22-3.17]. Compared with those in the lowest quartile of total PCBs, the highest quartile was associated with about a 3-fold risk (OR = 2.78; 95% CI, 1.41-5.48), and the positive trend was significant (p = 0.017). Significant positive trends in ALL risk were apparent with increasing concentrations of PCB congeners 118, 138, and 153. We observed no significant positive associations for chlordane, DDT, DDE, methoxychlor, or pentachlorophenol. The associations with PCBs were stronger among non-Hispanic whites than among Hispanics despite similar distributions of PCB levels among controls in each racial/ethnic group.
  
  
  CONCLUSIONS
  Our findings suggest that PCBs, which are considered probable human carcinogens and cause perturbations of the immune system, may represent a previously unrecognized risk factor for childhood leukemia.
authors: Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892-7240, USA. wardm@mail.nih.gov
authors: Mary H
authors: MH
authors: Ward
authors: Joanne S
authors: JS
authors: Colt
authors: Catherine
authors: C
authors: Metayer
authors: Robert B
authors: RB
authors: Gunier
authors: Jay
authors: J
authors: Lubin
authors: Vonda
authors: V
authors: Crouse
authors: Marcia G
authors: MG
authors: Nishioka
authors: Peggy
authors: P
authors: Reynolds
authors: Patricia A
authors: PA
authors: Buffler
mesh_terms: D002648:Child; D002675:Child, Preschool; D004781:Environmental Exposure; D004785:Environmental Pollutants / Q000633:toxicity*; D005260:Female; D006630:Hispanic or Latino; D006801:Humans; D006843:Hydrocarbons, Chlorinated / Q000633:toxicity*; D007223:Infant; D007231:Infant, Newborn; D007938:Leukemia / Q000139:chemically induced* / Q000453:epidemiology / Q000208:ethnology; D008297:Male; D010575:Pesticides / Q000633:toxicity*; D011078:Polychlorinated Biphenyls / Q000633:toxicity*; D012307:Risk Factors; D044465:White People
chemical_list: D004785:Environmental Pollutants; D006843:Hydrocarbons, Chlorinated; D010575:Pesticides; D011078:Polychlorinated Biphenyls