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

[マウスでのX線誘発腫瘍形成に対する携帯電話放射の影響] med./bio.

Effects of mobile phone radiation on X-ray-induced tumorigenesis in mice

著者: Heikkinen P, Kosma VM, Hongisto T, Huuskonen H, Hyysalo P, Komulainen H, Kumlin T, Lahtinen T, Lang S, Puranen L, Juutilainen J
掲載誌: Radiat Res 2001; 156 (6): 775-785
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この研究は、マウスでの電離放射線誘発がんの成長に対する低レベルの高周波電磁界（RF）の影響を評価した。3 - 5週齢のメスのCBA/Sマウス200匹を、同数からなる4群に無作為に分け、それぞれケージ対照群、疑似ばく露群、２つのばく露群に割り当てた。ケージ対照群を除くすべての群のマウスに、まず電離放射線ばく露を与え、次いで1日1.5時間、週5日、78週間、RFばく露または疑似ばく露を与えた。ばく露群の１つには、NMT（Nordic Mobile Telephones）タイプの902.5 MHz周波数変調RF（連続波、SAR：1.5 W / kg）、もう１つには、GSM（Global System for Mobile）タイプの902.4 MHzパルス変調RF（パルス周波数217 Hz、SAR：0.35 W / kg）を用いた。体重、臨床徴候、ならびに食物と水の摂取量を定期的に記録した。また、全マウスの全ての病変および主要組織について血液学的検査および組織病理学的分析を行った。その結果、RFばく露は、いかなる新生物病変の発生率も有意には増加させなかった；これら知見は、携帯電話のRF放射によるがんのプロモート作用の証拠を提供していないと考える、と報告している。

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研究目的（著者による）

To evaluate the effect of low-level radiofrequency radiation on the development of cancer initiated in mice by ionizing radiation.

影響評価項目

ばく露

ばく露 パラメータ
ばく露1: 902.5 MHz
Modulation type: FM, CW
ばく露時間: repeated daily exposure, 1.5 h/day, 5 days a week for 78 weeks
  • 電力: 6.1 W average over time (± 0.8 W)
  • SAR: 1.5 W/kg average over time (whole body) (± 15%)
ばく露2: 902.4 MHz
Modulation type: pulsed
ばく露時間: repeated daily exposure, 1.5 h/day, 5 days a week for 78 weeks
  • 電力: 1.3 W average over time (± 0.1 W)
  • SAR: 0.35 W/kg average over time (whole body) (± 15%)

ばく露1

主たる特性
周波数 902.5 MHz
タイプ
  • electromagnetic field
特性
  • guided field
ばく露時間 repeated daily exposure, 1.5 h/day, 5 days a week for 78 weeks
Modulation
Modulation type FM, CW
Additional information

modulated with a random sequence of bytes
ばく露装置
ばく露の発生源／構造
チャンバの詳細 Three identical rectangular waveguide chambers made of aluminium were used in the study. The exposure chamber consisted of a straight rectangular section (24.8 cm x 20 cm) and of two waveguide-to-coaxial adapters. The total length of the chamber with the adapters was 190 cm. The mice were kept in small cylindrical acrylic restrainers (i.d. 32 mm, length adjustable) preventing them from aligning their longitudinal axis parallel to the electric field. The restrainers were placed 25 at a time on a Styrofoam holder so that each mouse was in the center of the cross section of the waveguide with its longitudinal axis perpendicular to the electric field and the direction of propagation. The distance between adjacent mice was 5 cm. The mice that were missing were replaced with mouse phantoms made of plastic cylinders partly filled with a solution simulating the dielectric properties of muscle at 900 MHz.
ばく露装置の詳細 Modified and computer-controlled mobile phones were used as signal sources. The signals were amplified by boosters manufactured for vehicle use. RF power meters were used for measuring the input, reflected and output power of the exposure chamber. The output power was absorbed by a coaxial 10 W termination. The SAR was controlled daily by adjusting the input power.
Additional information The animals were randomized into four equal groups: NMT exposure, GSM exposure, sham exposure and cage control. The sham exposed group was kept in an unenergised waveguide chamber. The mice in all groups except the cage-control group were exposed to ionizing radiation at the beginning of the study. The total-body dose was 4 Gy delivered as three equal fractions of 1.33 Gy at 1-week intervals with linear accelerators. The dose rate was 0.51 Gy/min. To ensure a uniform irradiation of the whole body, a Plexiglas scatterer was placed 15 cm above the animals.
パラメータ
測定量 値 種別 Method Mass 備考
電力 6.1 W average over time 測定値 - ± 0.8 W
SAR 1.5 W/kg average over time 測定値および計算値 whole body ± 15%
Additional parameter details

ELF background MF < 0.09 µT; static earth MF 41-54 µT (inclination 80-90°)

測定および計算の詳細

The whole-body-averaged SAR of mice was determined by the measurement of RF power absorbed in mice and a corrected conventional absorption equation. The SAR based on the power measurements was verified by measurements of the temperature increase of the phantoms for each phantom location. The two methods agreed within 2%. The spatial variation of the SAR due to reflections and power attenuation in the waveguide was estimated by electric-field measurements with a dipole probe. The maximum variation from the average SAR was about ± 30% for a 27-g mouse, and it decreased with the mass of the mouse. To ensure identical long-term average exposure, the order of animals in the Styrofoam holder was randomized for each exposure session. The estimated uncertainty of the whole-body-averaged SAR of an individual mouse during the whole exposure period was ± 15%. The measured SARs were compared with values obtained from FDTD calculations revealing that the ratio of the local maximum SAR inside the mouse to the whole-body-averaged SAR was from 4 to 8 and decreased with increasing mass of the mouse.

ばく露2

主たる特性
周波数 902.4 MHz
タイプ
  • electromagnetic field
特性
  • guided field
ばく露時間 repeated daily exposure, 1.5 h/day, 5 days a week for 78 weeks
Modulation
Modulation type pulsed
Duty cycle 12.5 %
Repetition frequency 217 Hz
Additional information

modulated with a random sequence of bytes
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 1.3 W average over time 測定値 - ± 0.1 W
SAR 0.35 W/kg average over time 測定値および計算値 whole body ± 15%

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:
研究対象とした臓器系:
調査の時期:
  • ばく露中
  • ばく露後

研究の主なアウトカム（著者による）

The results did not reveal any obvious effects of low-level radiofrequency radiation on X-ray-induced tumorigenesis.

研究の種別:

研究助成

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