Study type: Medical/biological study (experimental study)

Exposure to pulse-modulated radio frequency electromagnetic fields affects regional cerebral blood flow med./bio.

By: Huber R, Treyer V, Schuderer J, Berthold T, Buck A, Kuster N, Landolt HP, Achermann P
Published in: Eur J Neurosci 2005; 21 (4): 1000-1006
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Aim of study (acc. to author)

To study the effects of radiofrequency electromagnetic fields similar to those emitted by mobile phones on waking 1regional cerebral blood flow in healthy young men.

Background/further details

A previous study restricted to "handset-like" radiofrequency electromagnetic fields (publication 9345) revealed increased relative regional cerebral blood flow in the dorsolateral prefrontal cortex ipsilateral to the side of exposure. In the present study, the effect of a "base station-like" signal (mimicked the signal modulation emitted by a GSM base station) on regional blood flow was investigated and compared with a "handset-like" signal (similar spectral content as the one emitted by GSM mobile phones).

Endpoint

Exposure

Exposure Parameters
Exposure 1: 900 MHz
Modulation type: pulsed
Exposure duration: continuous for 30 min
  • SAR: 1 W/kg maximum (10 g) (± 14% uncertainty)
  • SAR: 1.5 W/kg maximum (1 g) (± 23% uncertainty)
Exposure 2: 900 MHz
Modulation type: pulsed
Exposure duration: continuous for 30 min
  • SAR: 1 W/kg maximum (10 g) (± 14% uncertainty)
  • SAR: 1.5 W/kg maximum (1 g) (± 23% uncertainty)

General information

The experiments consisted of a double blind sham controlled cross-over design with two active conditions as described in E1 and E2. The intervals between the exposure conditions were at least one week.

Exposure 1

Main characteristics
Frequency 900 MHz
Type
Exposure duration continuous for 30 min
Additional info Reference article: R. Huber, T. Graf, K.A. Cote, L. Wittmann, E. Gallmann, D. Matter, J. Schulderer, N. Kuster, A.A. Borbely and P. Achermann (2000) Exposure to pulsed high-frequency electromagnetic field during waking affects human sleep EEG. Neuroreport, 11, 3321-3325 (see publication id 4766).
Modulation
Modulation type pulsed
Pulse width 0.576 ms
Repetition frequency 217 Hz
Additional info

A "handset-like" signal (handset ) was used which had the following characteristics: combination of basic GSM mode and discontinuous transmission mode (DTX) with one of 8 slots active. Basic frame structure of GSM consists of 8 slots (0,..,7). For the handset signal, pulses are active in every slot # 0 except in every 26th frame and, in addition, pulses are active in slots # 1-6 of the frames used in the DTX mode.
Exposure setup
Exposure source
Setup The subjects sat on a chair with their heads positioned between the antennas. The left hemisphere of the brain was exposed.
Parameters
Measurand Value Type Method Mass Remarks
SAR 1 W/kg maximum measured 10 g ± 14% uncertainty
SAR 1.5 W/kg maximum measured 1 g ± 23% uncertainty
Measurement and calculation details

The exposure conditions were well controlled and characterized by a detailed dosimetry (assessment of dosimetric measurement uncertainty, variations due to head movements, differences in anatomy, etc).

Exposure 2

Main characteristics
Frequency 900 MHz
Type
Exposure duration continuous for 30 min
Modulation
Modulation type pulsed
Pulse width 0.576 ms
Repetition frequency 217 Hz
Additional info

A "base-station like" signal (bstat) (emitted by a GSM base station in communication with 7 mobile phones) was used which had the following characteristics: basic GSM mode and discontinuous transmission mode (DTX) with 7 of 8 slots active. Basic frame structure of GSM consists of 8 slots (0,..,7). For the bstat signal, pulses are active in slots # 0-6, whereas each 26th and 104th frame are modified.
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
SAR 1 W/kg maximum measured 10 g ± 14% uncertainty
SAR 1.5 W/kg maximum measured 1 g ± 23% uncertainty

Reference articles

  • Huber R et al. (2003): Radio frequency electromagnetic field exposure in humans: Estimation of SAR distribution in the brain, effects on sleep and heart rate
  • Huber R et al. (2002): Electromagnetic fields, such as those from mobile phones, alter regional cerebral blood flow and sleep and waking EEG

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

An increase in relative regional cerebral blood flow in the dorsolateral prefrontal cortex on the side of exposure was found. The effect depended on the spectral power in the amplitude modulation of the radiofrequency carrier such that only 'handset-like' radiofrequency electromagnetic field exposure with its stronger low frequency components but not the 'base station-like' radiofrequency electromagnetic field irradiation affected regional cerebral blood flow.
This data supports the authors' previous observation that pulse modulation of radiofrequency electromagnetic field is necessary to induce changes in the waking and sleep EEG, and substantiates the notion that pulse modulation is crucial for radiofrequency electromagnetic field-induced alterations in brain physiology. However, the observed effects of the pulse modulated electromagnetic field were subtle and the underlaying mechanisms remain unknwon. Conclusions about health consequences are premature.

Study character:

Study funded by

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