American Journal of Epidemiology Advance Access originally published online on February 28, 2008
American Journal of Epidemiology 2008 167(7):883-884; doi:10.1093/aje/kwn014
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LETTERS TO THE EDITOR |
RE: "RADIO-FREQUENCY RADIATION EXPOSURE FROM AM RADIO TRANSMITTERS AND CHILDHOOD LEUKEMIA AND BRAIN CANCER"
1 Institute of Cancer Epidemiology, Danish Cancer Society, DK-2100 Copenhagen, Denmark
2 Südwestrundfunk, 70190 Stuttgart, Germany
3 Institute of Medical Biostatistics, Epidemiology, and Informatics, University of Mainz, 55101 Mainz, Germany
4 Lower Saxony Water Management, Coastal Defence and Nature Conservation Agency, 31135 Hildesheim, Germany
(e-mail: joachim{at}cancer.dk)
Ha et al. (1) report results from a Korean study that was a major improvement compared with previous studies on the possible association between radiofrequency electromagnetic field (RF-EMF) exposure and cancer risk. The case-control approach with sizeable numbers of subjects using individual exposure estimation was clearly superior to previous ecologic studies in the vicinity of television and radio broadcast transmitters (2–9). We are, however, concerned about some methodological issues.
First, while in figure 2 Ha et al. (1) demonstrate a good overall correlation between RF-EMF exposure and distance of the child's residence to the nearest transmitter, it can also be seen that distance is a good proxy for each single transmitter but not necessarily for all transmitters combined. Figure 2 shows that, for example, a RF-EMF exposure level of about 1 V/m is obtained in a distance of 2 km of the weakest transmitter but in >10 km of the strongest transmitters. Hence, the rationale of the distance-based analysis approach across all transmitters needs to be further justified.
Second, a categorization of RF-EMF exposure into quartiles is likely to dilute any possible effect as, because of the highly skewed distribution of the exposure, a separate categorization of the highest percentiles would have been more appropriate. Furthermore, in table 2, Ha et al. (1) present results for RF-EMF exposure and childhood leukemia risk, displaying elevated risk estimates for all exposure categories for lymphocytic leukemia (70 percent of cases), as well as myelocytic leukemia (24 percent of cases), some of them statistically significantly increased, but combining all leukemia subtypes yielded decreased risk estimates, some of them statistically significant, for all exposure categories. This is unexpected and needs to be explained.
Last, a clarification on the exposure calculation method is needed, as the units for neither the distance d nor the field E in the applied corrections are given. For E, it is even unclear whether E is a linear measure of field strength (suggested by the formula that specifies total RF-EMF exposure as the root of the sum of Ei2) or a logarithmic one (suggested by the fact that the value of the correction does not depend on the transmitter power). It would be valuable if the benefit in accuracy from use of the corrections obtained from an undisclosed number of measurements could be better described.
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ACKNOWLEDGMENTS |
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Johannes Philipp is employed by the Südwestrundfunk, one of Germany's largest public television and radio channels and broadcast tower operators. The views expressed in this letter are his personal views and do not necessarily reflect the views of the Südwestrundfunk.
Conflict of interest: none declared.
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- Ha M, Im H, Lee M, et al. Radio-frequency radiation exposure from AM radio transmitters and childhood leukemia and brain cancer. Am J Epidemiol (2007) 166:270–9.
[Abstract/Free Full Text] - Selvin S, Schulman J, Merrill DW. Distance and risk measures for the analysis of spatial data: a study of childhood cancers. Soc Sci Med (1992) 34:769–77.[CrossRef][Web of Science][Medline]
- Maskarinec G, Cooper J, Swygert L. Investigation of increased incidence in childhood leukemia near radio towers in Hawaii: preliminary observations. J Environ Pathol Toxicol Oncol (1994) 13:33–7.[Medline]
- Hocking B, Gordon JR, Grain HL, et al. Cancer incidence and mortality and proximity to TV towers. Med J Aust (1996) 165:601–5.[Web of Science][Medline]
- Dolk H, Elliot P, Shaddick G, et al. Cancer incidence near radio and television transmitters in Great Britain. II. All high power transmitters. Am J Epidemiol (1997) 145:10–17.
[Abstract/Free Full Text] - Cooper D, Hemmings K, Saunders P. Re: "Cancer incidence near radio and television transmitters in Great Britain. I. Sutton Coldfield transmitter; II. All high power transmitters." (Letter). Am J Epidemiol (2001) 153:202–4.
[Free Full Text] - Michelozzi P, Capon A, Kirchmayer U, et al. Adult and childhood leukemia near a high-power radio station in Rome, Italy. Am J Epidemiol (2002) 155:1096–103.
[Abstract/Free Full Text] - Ha M, Lim HJ, Cho SH, et al. Incidence of cancer in the vicinity of Korean AM radio transmitters. Arch Environ Health (2003) 58:756–62.[CrossRef][Medline]
- Park SK, Ha M, Im HJ. Ecological study on residences in the vicinity of AM radio broadcasting towers and cancer death: preliminary observation in Korea. Int Arch Occup Environ Health (2004) 77:387–94.[Web of Science][Medline]
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