Topic

Influence of high frequency electromagnetic fields of mobile telecommunications on sensory organs
B. The visual system

Start

01.07.2004

End

30.09.2006

Project Management

University of Oldenburg

Objective

There are only a few studies available on the effects of high frequency electromagnetic fields on sensory organs. The specific sensitivity of the eye to thermal effects is known. A few studies suggest possible non-thermal effects of high frequency electromagnetic fields on the retina. Their mechanism is not known in detail.

The influence of pulsed (GSM) and non-pulsed fields (UMTS) of mobile phones on delicate sensory organs, such as the eye, will be studied. The eye, respectively the retina, a multi-layered sensory tissue lining the back of the eye, will be exposed to various intensities above and below approved partial body SAR values (2 W/kg). The possible influence of high frequency fields on physiological parameters of sensory cells and interneurons and their synaptic communication can be studied, for example, using neuro-physiological methods. Threshold values of these biological effects should be determined. If possible, their mechanism of action should be explained.

The objective of this project is to describe the possible physiological effects of high frequency electromagnetic fields on the optical system and to investigate their mechanisms of action in order to evaluate their relevance to health.

Results

The researchers provided a review on possible influences of high frequency electromagnetic fields on the visual system of humans and animals. The few scientific papers concerning this topic show that thermal influences on the eye are established, but the existence of non-thermal effects still remains speculative.

The investigations were performed on isolated mice retina preparations, which were kept in a nutritive solution at constant temperature. The exposure of the preparations with the standards GSM 900, GSM 1800 and UMTS at intensities of 0.02, 0.2, 2 and 20 W/kg as well as sham exposure were applied in a blinded and fully automated fashion in a waveguide resonator. The electrical activity (nerve impulses) of the ganglion cells of the retina was measured in response to light stimuli of different intensities by extra cellular recordings using glass electrodes. The exposure duration was 30 min, the electrophysiological recordings were performed before, during and after the end of the exposure. The response latencies and nerve impulse frequencies in response to "light on" and "light off" were determined and evaluated statistically by means of Dunnet's test and "General Linear Mixed Model" (GLMM).

The statistical evaluation by means of Dunnet's test showed within 1344 multiple average comparisons per frequency band eight weakly significant differences for GSM 900 MHz and GSM 1800 MHz, respectively, and 13 weakly significant (p<0.05) differences for UMTS in comparison to control. These did not follow systematically the SAR value or any other examined parameter, and considering the high number of paired comparisons they are assumed to represent a statistical chance. No highly significant differences were found (p<0.01).

The substantially more sensitive statistic evaluation by means of GLMM showed within altogether eight evaluated parameters per frequency band one significant effect of SAR at GSM900 and two effects at GSM1800. No significant effects were found for UMTS. The significances are possibly statistic artefacts, since they concern different parameters of the cell response and do not follow a clear pattern. For the light intensity, the sequence of measurements and the temperature, which varied by maximally 0.5 °C, repeatedly significant effects arose. This indicates the high sensitivity of the method.. The multivariate statistic evaluation of the combined effects of several parameters showed a complex picture of a thermally induced significant combined effect of the parameters high frequency exposure and light intensity.

It can be downloaded as PDF-files in German can with English abstract:

Final report (2,2 MB)

Final report attachments (3,3 MB).

References

Ahlers MT, Bolz T, Bahr A, Ammermüller J (2009) Temperature-controlled exposure systems for investigating possible changes of retinal ganglion cell activity in response to high-frequency electromagnetic fields. Radiat Environ Biophys. 48(2):227-35

Conclusions

Using a very sensitive electrophysiological method as well as a highly sensitive statistic evaluation, few weakly statistically significant main effects of high frequency exposure with SAR-values within the range of 0 - 20 W/kg on the nerve impulse activity of the neural network of the retina were observed. These are most likely a statistical artefact. Further more, thermal effects occurring at certain parameter combinations were found., Temperature variations within the range of several 0.1 °C, such as occurring also in the course of the daily rhythm, may cause slight fluctuations of the activity of neural networks, which are physiologically normal. All observed effects were within the normal physiological range and represent a weak physiological influence, but no health impact. SAR values of up to 20 W/kg were examined, whereas realistic SAR values in the retina during a phone call are far below the limit value of 2 W/kg. Therefore even the minor thermal effects shown here are not expected to occur under realistic conditions.