| Residential Exposure to Polychlorinated Biphenyls and Organochlorine Pesticides and Risk of Childhood Leukemia Mary H. Ward,1 Joanne S. Colt,1 Catherine Metayer,2 Robert B. Gunier,3 Jay Lubin,1 Vonda Crouse,4 Marcia G. Nishioka,5 Peggy Reynolds,3 and Patricia A. Buffler2 1Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland, USA; 2School of Public Health, University of California–Berkeley, Berkeley, California, USA; 3Northern California Cancer Center, Berkeley, California, USA; 4Children’s Hospital of Central California, Madera, California, USA;
5Battelle Memorial Institute, Columbus, Ohio, USA Abstract
Background: Incidence of childhood leukemia in industrialized countries rose significantly during 1975–2004, and the reasons for the increase are not understood. Objectives: 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 α- and γ-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. Key words: childhood cancer, dust, leukemia, organochlorine compounds, pesticides, polychlorinated biphenyls. Environ Health Perspect 117:1007–1013 (2009) . doi:10.1289/ehp.0900583 available via http://dx.doi.org/ [Online 27 January 2009]
Address correspondence to M.H. Ward, Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, NCI, NIH, 6120 Executive Blvd., Rm. 8006, Bethesda, MD 20892-7240 USA. Telephone: (301) 435-4713. Fax (301) 402-1819. E-mail: wardm@mail.nih.gov We thank clinical investigators at the collaborating hospitals for help in recruiting patients, including J. Ducore (University of California–Davis Medical Center) , M. Loh and K. Matthay (University of California–San Francisco) , V. Crouse (Children’s Hospital of Central California) , G. Dahl (Lucile Packard Children’s Hospital) , J. Feusner (Children’s Hospital Oakland) , V. Kiley (Kaiser Permanente Sacramento) , C. Russo and A. Wong (Kaiser Permanente Santa Clara) , K. Leung (Kaiser Permanente San Francisco) , and S. Month (Kaiser Permanente Oakland) . We also acknowledge the Northern California Childhood Leukemia Study staff and the Survey Research Center for their effort and dedication, and S. Merkle and N. Appel at Information Management Services for programming and data management support. This research was partially supported by the Intramural Research Program of the National Cancer Institute (NCI) , National Institutes of Health, and through NCI subcontracts 7590-S-04 (University of California–Berkeley) and 7590-S-01 (Battelle Memorial Institute) under NCI contract N02-CP-11015 (Westat Inc.) . This research was also financially supported by National Institute of Environmental Health Sciences grants R01ES009137 and P-42-ES-04705-18 (University of California–Berkeley) and NCI grant 5R01CA092683-03 (Colorado State University) . The authors declare they have no competing financial interests. Received 15 January 2009 ; accepted 27 January 2009.
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