Forschungsgemeinschaft Funk e.V.

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Edition No. 12a December 1996
Cerebro-Biological Effects in Low-Frequency Pulsed RF Fields

J. F. Spittler, P. Calabrese, W. Gehlen, M. Heidrich, Neurologische Universitäsklinik, Knappschafts-Krankenhaus, Bochum-Langendreer, Germany

Possible effects of the transmitting field of mobile telephones on brain function have been predominantly reported in small numbers of cases. The EEG served as the basic parameter in most cases. However it cannot always be established wether observed alterations are biological electro-magnetic effects on the brain and wether they are detrimental.
Methods: We investigated 52 normal volunteers, age 20-38 years, by means of EEG and neurological testing. According to their medical reports and neurological examination the individuals were healthy, without medication or sleep deficits. The examination was carried out in a room equipped with RF absorbers; external parasitic fields were measured and recorded in the frequency range 5 Hz to 3 GHz. For the 11th-20th minute of the 30 minute-EEG recording 25 test subjects were exposed to the transmitting field of a commercial mobile telephone, 27 served as controls without field exposure. The transmitted power was 8 W, the frequency was 914,2 MHz (GSM-test modus). The antenna was set up at a distance of 45 cm above the subjects’ heads. The field strength in the heads’ area was approximately 40 V/m (assuring that the limit value according to DIN/VDE 0848 was not exceeded). The EEG was recorded with a digital facility (electrode positions according to the international 10/20 system, Ag/ AgCl electrodes, impedances (10kOhm). In order to control vigilance the volunteers repetitively had to count to 10 and then press a key. For further evaluation the spectral power (V2) was used. Aliasing resulting from the modulation frequency of the mobile telephone (217 Hz) projecting into the EEG frequency range (0,5-30 Hz) could be avoided by using a scanning frequency of 500 Hz. Artifact elimination was carried out by mathematical means cutting off the measured values >2 standard deviations. With regard to neuropsychology the normal adult subjects were examined on two subsequent days in a crossover-design with paralles tests and were all exposed to the transmitting field at random, either in the first or in the second examination phase. General intellectual capacities and learning performance were examined using paper-pencil tests, different functions of attention were examined with computer-based procedures.
Results: The visual evaluation of color-coded diagrams of the spectral power in the frequency range under observation (0,5-30 Hz) showed no effects of field exposure (11th-20th minute) over time compared with the preceeding and subsequent 10 minutes as well as in comparison between exposed and non-exposed individuals. For usual frequency bands the mean power values were calculated in the three measurement phases for selected electrode positions (Cz, T3, T4, P3, P4, O1, O2). In a multivariate analysis of variance the average values showed no significant differences (F=1,78576; df=42; p=0,178). By neuropsychological testing no significant differences of cognitive performance were seen between the test phases with or without field exposure.

Conclusion: In a controlled comparative study with 52 normal adult subjects no significant impact of the transmitting field generated by a mobile telephone on the human electroencephalogram as well as on cognitive performance could be observed.

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