MTHR - Mobile Telecommunications and Health Research

Human Volunteers Studies Workshop

Chair: Professor K Hansson Mild

The session dedicated to human volunteer studies included presentations from research groups funded by both the MTHR and Home Office TETRA programmes. These groups are using human volunteers to study the potential effects of radiofrequency fields on physiology and performance. Endpoints being investigated include memory, attention and the electroencephalogram, as well as labyrinthine function, blood pressure and effects on the cardiovascular system. Other studies are investigating neuroendocrine levels and general symptoms. The final study in this session explored the effects of mobile phone use on driving, and compared the effects of hands-free phone use with other distracting acts performed while driving.

A number of these studies include volunteers who report increased sensitivity to the fields from mobile phones. These will investigate the possibility that a sub-population of people may exist who are hypersensitive to radiofrequency fields. The majority of the human volunteer studies are still recruiting volunteers, and an important issue highlighted during this session was the difficulty in recruiting sufficient numbers of self-reporting hypersensitive individuals. There could be many reasons for this, including the perceived health risks surrounding explicit exposure to radiofrequency fields, and the difficulty in getting subjects to travel to the relevant laboratories where testing will occur.

All the human volunteer studies will use the same type of exposure system to enable direct comparisons to be made between studies. Previous studies used numerous methods to expose subjects to radiofrequency fields and this made direct intercomparison more difficult. Therefore a Standard Human Exposure System was designed and produced. This was based on a commercially available handset which should be broadly familiar to many volunteers. These handsets have been delivered to the relevant groups. The handsets are capable of generating either GSM 900 MHz or TETRA 400 MHz signals, and they can be used to produce a variety of modes, including pulsed or continuous wave signals. Finally a range of specific energy absorption rate (SAR) values can be set. Overall this flexibility allows comprehensive testing of the usual frequency and field intensities that users of mobile phones are exposed to. Due to the design of these handsets both the experimenter and the subject will remain blind to the exposures used during the experiments. The handsets are also used in a specific set position on either side of the head ensuring that there is consistent exposure across all subjects and studies. This also allows accurate dosimetry calculations to be made.

The groups working with these exposure systems have undertaken testing to assess if the exposure system interferes with other electronic equipment used during the experimental work and to assess if volunteers can dissociate between the handsets different modes. One of the groups did note a slight difference in temperature of the handset when set at different modes and new handsets were supplied to this group to rectify this problem.

All these studies are still collecting data but since they are being performed blind, no explicit results could yet be presented. However, the research group studying the effects of hands-free phone use while driving has completed its experiments and publication of the results is expected soon.

Summaries of the closed sessions of the MTHR Research Seminar - 4th of November 2003