この研究は、携帯電話（MP）の使用時に自覚症状を経験している人を対象に含めたボランティア実験において、携帯電話様の無線周波（RF）電磁界のばく露による影響の有無を調べた。MP関連症状があると訴える20人（有症者群）と、彼らにマッチングして選抜されたMP関連症状の訴えがない20人（対照群）は、電力周波および高周波の電磁界の背景レベルが十分に低減されたばく露実験室内で、2つの実験セッション（それぞれ30分間）に参加した。1つは真のばく露セッション、もう1つは擬似ばく露で、実施順はランダムにした。GSM 900 携帯電話をばく露用信号発生器に用いた。電話機アンテナ2機は、被験者の両側に頭部からの8.5 cmの距離に置かれた（右アンテナはばく露用、左アンテナはダミー）。この距離でのファントムを用いたドシメトリにより、頭部SARは1 g平均で1 W / kg、10 g平均で0.8 W / kgであった。実験中に、心拍数、心拍変動（HRV）、呼吸、局所血流、皮膚電気活動を測定した。また、被験者の前に設置したLCDコンピュータスクリーンを用いて、フリッカー融合周波数閾値（CFFT）、認知タスクでの短期記憶および反応時間を測定した。その結果、RFばく露に関連する有意な差は検出されなかった；また、反応時間を除くベースラインデータに、被験者グループ間で差はなかった；反応時間は、最初に実施された実験において、対照群よりも有症者群の方が有意に長かったが、この差は、実験を繰り返すと消失した；周波数領域で測定されたHRVには、ばく露の有無とは無関係に、有症者群と対照群の間で異なる所見が見られた（有症者群では、ばく露と無関係に、CFFTおよび記憶テスト中に自律神経系の交感神経優位の方向へと低/高周波数比がシフトした）；これは、MPに関連した自覚症状のある人とそのような症状のない人との間の自律神経系調節の違いの兆候と解釈できるかもしれない、と報告している。
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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.
| 周波数 | 900 MHz |
|---|---|
| タイプ |
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| ばく露時間 | continuous for 30 min |
| ばく露の発生源／構造 |
|
|---|---|
| Distance between exposed object and exposure source | 8.5 cm |
| チャンバの詳細 | 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). |
| ばく露装置の詳細 | 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 information | 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.
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