The effects of high-frequency electromagnetic fields emitted by mobile phones on humans have been hotly debated for years. In a new study, neuroscientists from Ruhr-Universitaet-Bochum (RUB) in Germany have shed light on this question. For the first time, they provide evidence that extremely high-powered electromagnetic fields can influence learning processes on the synaptic level within the brain, independent from other factors such as stress. However, such high levels are not encountered during typical use of mobile phones, the researchers note.
"For this effect, very high values are necessary. These do not occur during the daily use of mobile phones," explains Dr. Nora Prochnow, with RUB's Medical Faculty.
Mobile phone derived non-ionizing radiation can produce heat …
High-frequency electromagnetic fields (HEFs) are not only used in mobile phones, but also in a variety of other communication systems like radio, television or cordless telephone sets. Mobile phones of the so-called third generation utilize the UMTS technology (Universal Mobile Communication System) with a frequency of 1200 MHz and a relatively weak operating range (3.8-4.8 V/m). With increasing power, electromagnetic fields (EMFs) are able to elicit local warming of body tissues, being also described as a "thermal effect." Reportedly, mobile phones can cause local warming of the brain by less than 0.1°C. The effect on function and structure of the brain during long term use of mobile phones (e.g. > 30 min) remains unexplained until now.
… and might influence cellular activity
Furthermore, findings regarding the non-thermal effects of mobile phone emitted EMFs are unclear and contradictory. These comprise, for instance, an increase in permeability and fluidity of cellular membranes, which can be implicated in changes in ion-channel integration and metabolism, even without a detectable change in temperature. This may impair synaptic learning processes in the brain. Until now, experiments could not sufficiently answer the question of whether these effects are derived from non-thermal HEFs or from stress, as it can be induced by handling of the experimental animal (e.g. placing a rat into an unknown environment).
Stress or non-thermal EMF effect -- Scientists find out for the first time
To investigate this question, a new study was performed by scientists of the Department of Neuroanatomy and Molecular Brain Research (Professor Dr. med. Rolf Dermietzel) in cooperation with the Chair of Electromagnetic Theory of the University of Wuppertal. For the experiment, rats were placed into differently powered non-thermal HEFs in the UMTS operating range. Synaptic learning and memory formation were analysed by electrophysiological methods. Furthermore, all animals were tested for stress hormone release immediately following the HEF exposure.
Mobile phone use seems to be harmless -- critical values for occupational use have to be controlled precisely
The results: Although there was daily training and effortless contact to the exposure environment, increases in blood derived stress hormone levels could be detected for all exposed groups. The stress clearly influences learning and memory formation on the synaptic level in the rat brain. High-powered EMFs (SAR 10 W/kg) also have a significant effect on learning and memory formation. In contrast to this, weak EMFs (SAR 0 and 2 W/kg) lead to no detectable changes or impairments.
"These results cannot directly be transferred to humans," says Nora Prochnow. "But in the animal model, it can be demonstrated that neuronal mechanisms of synaptic learning can serve as a target for high powered EMFs."
However, there is no need for serious concerns: humans are not exposed to such high-powered EMFs during daily mobile phone use. Nevertheless, the matter has to be regarded differently in special occupational situations, for instance during the use of body worn antenna systems as it is common for security services or military purposes. Here, critical levels for occupational exposure may be reached more easily and have to be controlled carefully.
- Nora Prochnow, Tina Gebing, Kerstin Ladage, Dorothee Krause-Finkeldey, Abdessamad El Ouardi, Andreas Bitz, Joachim Streckert, Volkert Hansen, Rolf Dermietzel. Electromagnetic Field Effect or Simply Stress? Effects of UMTS Exposure on Hippocampal Longterm Plasticity in the Context of Procedure Related Hormone Release. PLoS ONE, 2011; 6 (5): e19437 DOI: 10.1371/journal.pone.0019437
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