Merzenich H, Schmiedel S, Bennack S, Bruggemeyer H, Philipp J, Blettner M, and Schuz J (2008) Childhood leukemia in relation to radio frequency electromagnetic fields in the vicinity of TV and radio broadcast transmitters. Am J Epidemiol 168: 1169-1178.
Background and Objective
The impetus of the present study was the conflicting evidence from past studies of leukemia and radiofrequency (RF) exposures arising from radio and TV broadcast stations. The present study also sought to extend previous results by covering both amplitude modulated (AM) and frequency modulated (FM) transmitters.
The study was a case-control design, conducted between 2005 and 2007 in West Germany. Stations identified were limited to 16 high-power AM transmitters (of at least 200 kW) and 8 FM (effective radiated power of 200 kW) and TV (500 kW) transmitters. A total of 805 municipalities surrounding these stations were defined. The study population included direct population-sampled controls and leukemia (lymphoid and myeloid) cases diagnosed between 1984 and 2003 in the complete German Childhood Cancer Registry. Three controls were matched to each case, according to date of diagnosis and transmitter area (when historical records permitted). The final study population included 1959 cases and 5848 controls less than 15 years of age. Exposure information was provided by operators, who supplied data describing the operating characteristics of their transmitters between 1983 and 2002. An additional 312 lower-powered transmitters were considered for their RF exposure contributions. Two calendar exposure periods were considered (1983–1991, 1992–2002) to assess the RF contributions from the introduction of cellular networks.
For all types of leukemia, grouping AM and FM/TV transmitters, and when comparing the upper 5% of RF exposure (0.701 - 7.742 V/m) to the lower 90% of exposure (0.004 - 0.504 V/m), the odds ratio was 0.86 (with 95% confidence limits of 0.67 and 1.11). However, no statistically significant associations were observed by transmitter type (AM
and FM/TV) or by subtype of leukemia. Analysis by calendar periods showed no difference between the two exposure periods and no statistically significant increased risk for all types of leukemia or subgroups of leukemia. The odds ratio for all types of leukemia was 1.04 (95% confidence limits of 0.65 and 1.67) among children living within 2 km of the nearest broadcast transmitter compared with those living 10 to 15 km away. Some odds ratios for lymphoid leukemia and all leukemias at distances of 2 to 10 km were statistically significantly decreased.
Discussion and Conclusion
Study results may possibly have been influenced by confounders such as social class or immune-system-related variables. The authors interpret their results as not showing any significant increase in childhood leukemia risk associated with exposure to RF emissions by broadcast towers, and hence the results weaken the evidence from earlier reports. The modulation mode and frequency range of the RF signal also had no impact on disease risk. Furthermore, during the period in which there was little major contribution from mobile phone communication technology (1983–1991), no elevated risks of leukemia were found.