American Journal of Epidemiology Advance Access originally published online on August 16, 2007
American Journal of Epidemiology 2007 166(7):859-860; doi:10.1093/aje/kwm227
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LETTERS TO THE EDITOR |
THE AUTHORS REPLY
1 Institute of Cancer Epidemiology, Danish Cancer Society, DK-2100 Copenhagen, Denmark
2 Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD 20892
3 British Columbia Cancer Agency, Vancouver V5Z 4E6, British Columbia, Canada
4 Epidemiology and Genetics Unit, Department of Health Sciences, University of York, York YO10 5DD, United Kingdom
5 Institute of Environmental Medicine, Karolinska Institute, SE-171 77 Stockholm, Sweden
6 Department of Epidemiology, School of Public Health, University of California, Los Angeles, Los Angeles, CA 90095
7 Electric Power Research Institute, Palo Alto, CA 94304
(e-mail: joachim{at}cancer.dk)
We thank O'Carroll et al. for their comments (1) and reiterate our opinion that our analysis provides little support for the hypothesis that nighttime extremely low frequency electromagnetic field exposure explains the association between magnetic field exposure and childhood leukemia risk (2). Following the initial pooled analysis (3), a subsequent German analysis demonstrated a strong association with nighttime exposure and a linear dose-response relation (4, 5), irrespective of the high correlation between daytime and nighttime exposure. This led to the suggestion that nighttime exposure might be a better exposure metric than the widely used 24-/48-hour average exposure, due either to reduced exposure misclassification or, in light of the melatonin hypothesis, to the exposure occurring in a biologically more meaningful time window. Had this been confirmed using the pooled data set, it would have supported the suggestion that the association between magnetic fields and childhood leukemia is actually stronger than previously described (3). Instead, however, our main finding was that the 24-/48-hour average exposure and nighttime exposure metrics gave virtually the same results (2).
It was not the purpose of our paper to discuss biologic plausibility further than the melatonin hypothesis, which was not supported by our findings. Importantly, the recent comprehensive reports by the World Health Organization (6) and the European Union (7) are in line with our assessment that there is currently no established mechanism explaining the observed association between magnetic fields and childhood leukemia risk.
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ACKNOWLEDGMENTS |
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Conflict of interest: none declared.
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References |
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 TOP References |
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- O'Carroll MJ, Henshaw D, Ward J, et al. Re: "Nighttime exposure to electromagnetic fields and childhood leukemia: an extended pooled analysis." (Letter). Am J Epidemiol (2007) 166:859.
[Free Full Text] - Schüz J, Svendsen AL, Linet MS, et al. Nighttime exposure to electromagnetic fields and childhood leukemia: an extended pooled analysis. Am J Epidemiol (2007) 166:263–9. [Epub 2007 May 7].
[Abstract/Free Full Text] - Ahlbom A, Day N, Feychting M, et al. A pooled analysis of magnetic fields and childhood leukaemia. Br J Cancer (2000) 83:692–8.[CrossRef][Web of Science][Medline]
- Michaelis J, Schüz J, Meinert R, et al. Childhood leukemia and electromagnetic fields: results of a population-based case-control study. Cancer Causes Control (1997) 8:167–74.[CrossRef][Web of Science][Medline]
- Schüz J, Grigat JP, Brinkmann K, et al. Residential magnetic fields as a risk factor for childhood acute leukaemia: results from a German population-based case-control study. Int J Cancer (2001) 91:728–35.[CrossRef][Web of Science][Medline]
- World Health Organization. Extremely low frequency fields. (Environmental Health Criteria monograph no. 238). (2007) Geneva, Switzerland: World Health Organization. (http://www.who.int/peh-emf/publications/elf_ehc/en/index.html). (Accessed June26, 2007).
- Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR), European Commission. Possible effects of electromagnetic fields (EMF) on human health. (2007) Brussels, Belgium: European Commission. (http://ec.europa.eu/health/ph_risk/committees/04_scenihr/docs/scenihr_o_007.pdf). (Accessed June 26, 2007).
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