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Investigation of mechanisms of action in cells exposed to the high frequency electromagnetic fields of mobile telephone technology. A. demodulation / communication |
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Topic Investigation of mechanisms of action in cells exposed to the high frequency electromagnetic fields of mobile telephone technology. Start 01.07.2003 End 30.06.2007 Project Management University of Rostock Objective This project takes two different avenues to gather causal statements on the possible biological effects of electromagnetic fields. In one, sub-cellular electrical field distribution is modelled on and in the cell membrane by paying special attention to its molecular structure, and experimentally verified by single cell spectroscopy. This should result in the assessment of sub-cellular energy absorption, energy flow and the temporal behaviour of energy dissipation. The possibility of demodulating the low frequency pulsing of high frequency mobile electromagnetic fields can be clarified by using one cell module that takes into account cell and membrane structure. In the second approach, an assessment is made of the functional significance of effects observed at the sub-cellular level on the most delicate and notable structure of the central nervous system, namely the living brain. Electrophysiological measurements of single nerve cell activity and signal transduction between nerve cells within neural networks will provide statements on the functional impact of any membrane effects on neural communication. Results At the beginning of the project a literature study was provided, which summarizes current results of the modelling of the cell membrane characteristics as well as data on molecular parameters of the cytoplasm and the cell membrane. The literature study was published as a brochure. The text of the Literature study is available as PDF-file in German (1,108 KB). Further model calculations of the energy absorption due to HF exposure in simulated cells and their membranes were performed. The model system "human blood cell" was used. The model is characterized by electrically anisotropic properties of the lipid head groups within the cell membrane, which result in a so far not described unusual field distribution in the membrane and an increased local field absorption by up to a factor of 10. It could be shown that for these complicated systems a Laplace solution exists also for layered models, which agrees with the numeric results. The frequency range of the electro rotation measurements was extended up to 2 GHz in co-operation with the chair for theoretical electro-technology. In addition, measuring chambers adjusted for certain frequencies were constructed. Furthermore, rotation electrodes were adjusted to obtain a uniform rotation field. The results show GHz rotation effects in cells with a cell wall (e. g. yeasts), but not in blood cells. These differences are assigned to the presence of a larger bound water volume. Measurements on blood cells were performed in electro rotation chambers at different temperatures. In preliminary experiments an ion efflux from the cells was observed at high SAR-values in strong and inhomogeneous HF-Fields. After that, the time and temperature dependence of the ion efflux was first investigated without exposure and the test conditions were optimized. In further experiments (Attachment 1), no additional non-thermal directly field induced ion efflux from the cells has been found even at high SAR-values. Measurements on cell cultures from the brain cortex of mice on silicon chips were performed. First results with "continuous waves" as well as the UMTS signal show that there is a weak correlation between the cell activity and the effective field strength. This is accompanied by a rise in temperature of up to 0.2°C and is most likely thermal. The associated SAR values are within the range of 0.5 – 2 W/kg. Further, more detailed experiments (Attachment 2) were performed at SAR values of 0.14 W/kg, 1.3 W/kg and 2.6 W/kg. The last two exposures lead to a temperature increase of 0.12°C and 0.24°C, respectively; the exposure with 0.14 W/kg did not cause any measurable temperature increase. About 33 % of the evaluable nerve cells showed a thermally caused correlation with the power of the UMTS of signal. The neurons were not able to follow temperature changes faster than within about 10 s. It is well known from physiology that nerve cells and particularly interconnected neural networks can react to very small temperature changes. These effects are not adverse, since variation of the body temperature is substantially higher during the course of the day. No influence of the power modulation of the UMTS signal was found at 10 Hz (fading mode). Likewise no demodulation of the UMTS signal was observed at 740 Hz, which could possibly have led to changes in the form of nerve impulses. The final report as well as the Attachment 1 (Cell suspensions) and Attachment 2 (Neurochips) can be downloaded as PDF-files in German with English summary: Final Report (1,862 KB) Attachment 1 (1,066 KB) Attachment 2 (195 KB) References
Conclusions The presented study specifies some data of the microscopic filed distribution within cells and cell membranes more precisely. Due to its layered structure and the water content the cell membrane absorbs more energy than previously expected. There was no non-thermal field induced ion efflux from the cells even at high SAR-values. A demodulation of the UMTS signal in nerve cells was not found, however, it could be shown that the activity of these cells can follow slow and weak field-induced variations in temperature. Altogether new and partially unexpected physiological observations are presented. However, below the valid limit values the observed effects are minor and therefore health consequences are not anticipated. |