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

[携帯電話基地局シグナルへの短期ばく露によって、電磁過敏症者の症状は増すか？二重ブラインド無作為化誘発研究] med./bio.

Does short-term exposure to mobile phone base station signals increase symptoms in individuals who report sensitivity to electromagnetic fields? A double-blind randomized provocation study

著者: Eltiti S, Wallace D, Ridgewell A, Zougkou K, Russo R, Sepulveda F, Mirshekar-Syahkal D, Rasor P, Deeble R, Fox E
掲載誌: Environ Health Perspect 2007; 115 (11): 1603-1608
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【背景】電磁界に起因する特発性環境疾患(IEI-EMF)の人は、携帯電話基地局など日常的な物からの電磁界にばく露した時、自分は健康にネガティブな影響に苦しむと信じている。【目的】この研究は、オープン誘発テストおよび二重盲検法テストを用いて、基地局に似た信号にばく露された場合、擬似ばく露と比較して、過敏症グループおよび対照グループが健康悪影響をより多く受けるかどうかを明らかにするために行われた。【方法】過敏症と自己報告した56人と対照参加者120人にオープン誘発テストが実施された。このうち過敏症12人と対照6人が最初のセッション後、テストを辞退した。残りの人は一連の二重盲検法テストを完了した。脈拍、心拍、皮膚コンダクタンスの生理的測定値とともに、安寧度と症状についての主観的測定値が得られた。【結果】オープン誘発テストでは、過敏症グループはグローバル・システム・フォー・モバイル・コミュニケーションズ(GSM)とユニバーサル・モバイル・テレコミュニケーション・システム(UMTS)の両方において、擬似ばく露と比較してより低レベル安寧度を報告し、一方、対照グループはUMTSばく露においてより多くの症状を報告した。二重盲検法テストでは、GSM信号はいずれのグループにも影響を与えなかった。過敏症者はUMTSばく露では覚醒レベルの上昇を報告したが、体験した症状の数と重症度は増えなかった。生理的測定値はいずれのグループでも3つのばく露状態にわたって差異はなかった。【結論】典型的なGSM基地局の特徴をもつ信号への短期ばく露は、過敏症グループまたは対照グループにおいて、その安寧度や生理的機能に影響を及ぼさなかった。過敏症グループはUMTSばく露で覚醒レベルの上昇を報告した。しかし、さらに分析してみると、この差異はばく露そのものよりもばく露の順番の影響によるものらしいことが示された。

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研究目的（著者による）

This in vivo study was performed to determine whether the short-term exposure to base station-like signals causes negative health effects in humans.

詳細情報

56 participants in the so called "electrosensitive group" (self-reported experience of negative health effects from electromagnetic field exposure) and 120 participants in the control group were tested in the open provocation study (both participants and experimenters knew the base station status). Of these, 44 electrosensitive and 115 controls completed also the double-blind study.
The study was carried out in four sessions: first session both open and double-blind, second to fourth session only double-blind.

影響評価項目

ばく露

ばく露 パラメータ
ばく露1: 886.8–1,879 MHz
Modulation type: pulsed
ばく露時間: continuous for 5, 15, and 50 min
ばく露2: 2,020 MHz
ばく露時間: continuous for 5, 15, and 50 min

General information

Each participant attended four testing sessions at least one week apart. Sessions 2, 3, and 4 each used a single exposure condition (GSM, UMTS, or sham) double-blind, random, and counterbalanced. Session 1 took about 3 hours to complete while sessions 2, 3, and 4 each took about 1.5 hours.

ばく露1

主たる特性
周波数 886.8–1,879 MHz
タイプ
  • electromagnetic field
ばく露時間 continuous for 5, 15, and 50 min
Additional information combined signal of both 900 and 1800 MHz bands containing both broadcast and traffic channels at 886.8, 888.8, 1877, and 1879 MHz
Modulation
Modulation type pulsed
Additional information

GSM signal consisting of 8 timeslots, each with a duration of 576.875 µs resulting in a total frame duration of 4.615 ms, and interslot guard intervals of 32 µs duration with a drop in power level of around 50 dB. The 8 time slots on the broadcast channels were always occupied, while changes in the power level of the traffic channels were simulated using two first order, two state Markov processes, assuming a blockage rate of 1% and call activity of 40%.
ばく露装置
ばく露の発生源／構造
  • 基地トランシーバ局
  • simulated
Distance between exposed object and exposure source 5 m
チャンバの詳細 The testing room was 7 m x 4 m x 2.4 m and had a shielding effectiveness > 60 dB at the tested frequency range.
ばく露装置の詳細 Participants were seated 5 m from the base station antenna, which was hidden by a screen at 2.8 m, upon which instructions were projected from outside the testing room through a screened window.
Sham exposure A sham exposure was conducted.
Additional information In session 1, wash-out periods of 2 min were inserted between exposures.
パラメータ
測定量 値 種別 Method Mass 備考
電力密度 10 mW/m² - - - combined signal (2x 5 mW/m²)
Additional parameter details

A PC controlled all the exposures, thus making the tests repeatable.

測定および計算の詳細

All base station signals and field uniformity were independently tested and verified by the National Physical Laboratory. The stability of the exposure system was checked and calibrated every 6 months and was found to remain within ± 3 dB at each of the three frequency bands. The power into the antenna was continuously checked using a through line power meter.

ばく露2

主たる特性
周波数 2,020 MHz
タイプ
  • electromagnetic field
ばく露時間 continuous for 5, 15, and 50 min
Modulation
Modulation type cf. additional information
Additional information

UMTS signal with traffic modelling using Test Model 1, as defined by the 3GPP standard, with high peak to average ratio power changes.
ばく露装置
ばく露の発生源／構造
  • E1と同じ装置
パラメータ
測定量 値 種別 Method Mass 備考
電力密度 10 mW/m² - - - -

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:
  • ばく露後

研究の主なアウトカム（著者による）

During the open provocation, electrosensitive individuals reported lower levels of well-being in both the GSM and UMTS exposures compared to sham exposure, while the control group reported more symptoms during the UMTS exposure.
During double-blind tests the GSM exposure did not have any effect on either group. The electrosensitive group reported elevated levels of arousal during the UMTS exposure, while the number or the severity of symptoms experienced did not increase.
The short-term exposure to a GSM base station-like signal did not affect well-being or physiological functions in electrosensitive or normal individuals.

研究の種別:

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