研究のタイプ: 医学／生物学の研究 (experimental study)

[陸上基盤無線（TETRA）信号へのばく露で症状が起きるか？ 無作為化二重ブラインド誘発研究] med./bio.

Can exposure to a terrestrial trunked radio (TETRA)-like signal cause symptoms? A randomised double-blind provocation study

著者: Nieto-Hernandez R, Williams J, Cleare AJ, Landau S, Wessely S, Rubin GJ
掲載誌: Occup Environ Med 2011; 68 (5): 339-344
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この研究は、公共保安用無線通信の欧州統一規格であるTETRA様信号（16Hzパルス化無線周波電磁界）へのばく露時に主観的症状が生じるか否かを調べたボランティア実験である。被験者（TETRA使用者でEHS者60名と非EHS者60名）に3通りの実験セッション（16Hzパルス波信号ばく露、連続波信号ばく露、擬似ばく露）をいずれも50分間を行った。16Hzパルス波と連続波の平均出力は250mWであった。各セッションの実施順序は無作為、実験は二重ブラインドであった。ばく露中およびばく露終了後に8症状の重症度、ばく露終了時の気分、自分に作用する信号がどのセッションに含まれていたかを報告させた。その結果、連続波ばく露では、全被験者で頭痛の評点上昇、非EHS群で疲労感の評点上昇、EHS群で集中力の評点低下と皮膚掻痒感の評点低下が見られた；16Hzパルス波ばく露では、集中力以外の影響は示されなかった；多重比較を補正すると大半の影響は排除されたが、皮膚掻痒感に関する影響は排除されなかった、と報告している。

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研究目的（著者による）

To test whether exposure to a continuous wave signal at 385.25 MHz or a TETRA-like signal resulted in acute symptoms among regular TETRA users reporting sensitivity to TETRA compared to users not reporting sensitivity to TETRA.

詳細情報

60 sensitive and 60 non-sensitive participants were exposed to three 50 minutes conditions: a signal with a 16 Hz component, a continuous wave condition and a sham exposure. Questionnaires were completed before exposure and after 5, 15, 30 and 50 minutes during the exposure. After a resting period of 30 minutes, the participant was asked whether he thought the radio had emitted a signal and how confident he was about this.

影響評価項目

ばく露

ばく露 パラメータ
ばく露1: 385.25 MHz
Modulation type: CW
ばく露時間: continuous for 50 min
  • 電力: 250 mW mean
  • SAR: 1.3 W/kg maximum (10 g) (close to the antenna)
  • SAR: 0.3 W/kg average over mass (10 g) (from the handset body)
ばく露2: 385.25 MHz
Modulation type: pulsed
ばく露時間: continuous for 50 min
  • 電力: 250 mW mean
  • SAR: 1.3 W/kg maximum (10 g) (close to the antenna)
  • SAR: 0.3 W/kg average over mass (10 g) (from the handset body)
  • 電力: 1 W peak

ばく露1

主たる特性
周波数 385.25 MHz
タイプ
  • electromagnetic field
ばく露時間 continuous for 50 min
Modulation
Modulation type CW
ばく露装置
ばく露の発生源／構造
  • UK Mobile Telecommunications and Health Research programme's TETRA exposure system
ばく露装置の詳細 handset attached to the test person's head via a headband so that the antenna was positioned above and slightly behind the left ear within a few millimeters of the head
Sham exposure A sham exposure was conducted.
パラメータ
測定量 値 種別 Method Mass 備考
電力 250 mW mean - - -
SAR 1.3 W/kg maximum - 10 g close to the antenna
SAR 0.3 W/kg average over mass - 10 g from the handset body

ばく露2

主たる特性
周波数 385.25 MHz
タイプ
  • electromagnetic field
ばく露時間 continuous for 50 min
Modulation
Modulation type pulsed
Repetition frequency 16 Hz
ばく露装置
ばく露の発生源／構造
  • E1と同じ装置
Sham exposure A sham exposure was conducted.
パラメータ
測定量 値 種別 Method Mass 備考
電力 250 mW mean - - -
SAR 1.3 W/kg maximum - 10 g close to the antenna
SAR 0.3 W/kg average over mass - 10 g from the handset body
電力 1 W peak - - -

ばく露を受けた生物:

方法 影響評価項目／測定パラメータ／方法

研究対象とした生物試料:
調査の時期:
  • ばく露前
  • ばく露中
  • ばく露後

研究の主なアウトカム（著者による）

Exposure to the continuous wave signal increased ratings of headache in all participants, fatigue in non-sensitive participants and difficulty concentrating in sensitive participants. Paradoxically, exposure reduced sensations of itching in sensitive participants. These effects were not observed in the condition with 16 Hz pulsing (TETRA-like), except for those relating to concentration. Statistical analysis (multiple comparisons) removed most significant effects, but not those relating to itch.
Neither sensitive nor non-sensitive participants could discriminate between the exposures during the experiment, nor could they tell which session was most likely to have been sham exposure or which was most likely to have been TETRA.
In conclusion, these data suggest that exposure to TETRA signals is not responsible for symptoms reported by some users, although exposure to a continuous wave signal may affect symptoms.

研究の種別:

研究助成

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