To study the effect of exposure to a mobile phone-like radiofrequency electromagnetic field on persons experiencing subjective symptoms when using mobile phones.
20 subjects with mobile phone-related symptoms were recruited and matched with 20 controls without mobile phone-related symptoms.
|Exposure duration||continuous for 30 min|
|Distance between exposed object and exposure source||8.5 cm|
|Chamber||The provocation experiments were performed in a specially designed exposure chamber where background levels of both power frequency and radio frequency fields were low enough. The subjects were seated in a semi-reclining chair in front of an LCD computer screen. The antennas were mounted on an adjustable wooden framework surrounding the subject's chair. The antennas were placed one on each side of the subject's head at a distance of 8.5 cm. The head was positioned between two wooden bars in order to ensure a well-defined location during the provocation (exposure/sham).|
|Setup||A test GSM 900 mobile phone was used as signal generator. The RF signal was power amplified and fed to a power attenuator unit to adjust the signal level. The signal was further directed to a power divider allowing the signal to reach a power meter and the left or right antenna or a dummy load via a remotely controlled selector. Only the right antenna was used for the RF exposure; the left antenna served solely as a dummy.|
|Additional info||The subjects were tested on two separate days, one day with sham exposure and one with true exposure in random order.|
No significant differences related to radiofrequency exposure conditions were detected. Also no differences in baseline data were observed between the groups, except for the reaction time, which was significantly longer among the subjects with mobile phone-related symptoms (cases) than among the controls the first time the test was performed. This difference disappeared when the test was repeated.
However, the cases differed significantly from the controls with respect to heart rate variability. The cases displayed a shift in low/high frequency ratio towards a sympathetic dominance in the autonomic nervous system during the memory tests and the critical flicker fusion threshold, regardless of exposure condition (a higher activity in the low frequency band, as well as a lower activity in the high frequency band). This might be interpreted as a sign of differences in the autonomic nervous system regulation between persons with mobile phone-related subjective symptoms and persons with no such symptoms.
In conclusion the data do not support the hypothesis that exposure to mobile phone-like radiofrequency fields can explain perceived mobile-phone-attributed symptoms, nor that exposure affects memory functions. However, a difference between the cases and control group with respect to their autonomic nervous system regulation and working memory functions was demonstrated.