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

[GSM様信号（携帯電話）への慢性ばく露は、ラットのDMBA誘発乳腺腫瘍の成長を刺激しない：３つの連続研究の結果] med./bio.

Chronic exposure to a GSM-like signal (mobile phone) does not stimulate the development of DMBA-induced mammary tumors in rats: results of three consecutive studies

著者: Bartsch H, Bartsch C, Seebald E, Deerberg F, Dietz K, Vollrath L, Mecke D
掲載誌: Radiat Res 2002; 157 (2): 183-190
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この研究は、51日齢の雌SDラットに7,12-ジメチルベンズアントラセン（DMBA）を投与した後、最大3年間、GSM様信号(217Hzパルス変調した900MHz、パルス幅577μs)のばく露を継続し、ばく露群と擬似ばく露群での乳腺腫瘍の発生を観察した。同じ実験を、1997年（実験1）、1998年（実験2）、1999年（実験3）のそれぞれ同日に開始し、全部で120匹のSDラットを用いた。1ケージに12匹のラットを入れ、自由行動状態でばく露し、ケージでのレベルは100μW/cm2±3dBであった。ばく露期間中の体重により変化する全身平均SARは17.5-70W/kgであった。各個体を週1回触診し、悪性と良性サブタイプが信頼性高く組織病理学的に区分できる直径1-2cmの病変に達した時に、屠殺して病理標本を作成し、検査した。その結果、3つの実験の全体では、RFばく露群での腫瘍潜伏期間に有意な影響は見られず、各実験の終了時の累積腫瘍発生率にも影響はなかった；良性、悪性腫瘍のリスク比はそれぞれ1.08（95%信頼区間：0.91?1.29）、0.96 （同：0.85?1.07）であった；ただし、実験1では、各個体に最初に発生する悪性腫瘍の潜伏期の中央値がばく露群は278日、擬似ばく露群は145日と有意差があった；そのような差は、実験2、3では見られなかった、と報告している。

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研究目的（著者による）

To analyse the effect of radiofrequency fields on 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary cancers in female Sprague-Dawley-rats, which is an accepted model for human breast cancer.

影響評価項目

ばく露

ばく露 パラメータ
ばく露1: 900 MHz
Modulation type: pulsed
ばく露時間: nearly continuous until the largest tumour reached a diameter of 1-2 cm
  • 電力密度: 100 µW/cm² mean (± 3 dB)
  • SAR: 130 mW/kg average over mass (whole body) (32.5-130 mW/kg for young rats of 150 g)
  • SAR: 70 mW/kg average over mass (whole body) (17.5-70 mW/kg at 300 g)
  • SAR: 60 mW/kg average over mass (whole body) (15-60 mW/kg for older rats of 400 g)

ばく露1

主たる特性
周波数 900 MHz
タイプ
  • electromagnetic field
特性
  • far field
偏波
  • circular
ばく露時間 nearly continuous until the largest tumour reached a diameter of 1-2 cm
Modulation
Modulation type pulsed
Pulse width 577 µs
Repetition frequency 217 Hz
ばく露装置
ばく露の発生源／構造
  • flat spiral antenna
Distance between exposed object and exposure source 130 cm
チャンバの詳細 The animals in the RF-field-exposed and sham-exposed groups were kept in identical chambers. The five chambers used for sham and RF exposure, respectively, were placed in two separate air-conditioned, adjacent rooms of the same dimensions. Exposure chambers (90 x 90 x 187 cm) were made from sheet steel and had a lining of absorbing material on the walls and the bottom. Each chamber contained in its bottom part a Plexiglas cage of 0.4 m² x 20 cm equipped with three stainless steel nipples for drinking and covered by a perforated Plexiglas lid. The top as well as the lower front and back sides of the chamber underneath the animal cage were kept open for ventilation but covered with wire netting to suppress leakage of the EMF.
ばく露装置の詳細 Within the exposure chamber, the animal cage was located in the far field of a flat spiral antenna which was at a distance of 130 cm from the bottom of the cage and emitted a clockwise circularly polarized RF signal.
Additional information Exposure was interrupted once daily for about 10 to 20 min for feeding and inspection of animals, 3 to 4 h once weekly for tumour palpation, 1 to 2 h three times weekly for cleaning of cages, and 4 to 5 h once per month for servicing the exposure devices.
パラメータ
測定量 値 種別 Method Mass 備考
電力密度 100 µW/cm² mean 測定値 - ± 3 dB
SAR 130 mW/kg average over mass 測定値および計算値 whole body 32.5-130 mW/kg for young rats of 150 g
SAR 70 mW/kg average over mass 測定値および計算値 whole body 17.5-70 mW/kg at 300 g
SAR 60 mW/kg average over mass 測定値および計算値 whole body 15-60 mW/kg for older rats of 400 g
Additional parameter details

SAR values might have shown larger variations if instead of calculations for a standard rat model they had been based on actual phantom measurements of individual rats of different sizes and ages.

測定および計算の詳細

The mean power flux density of the field at the bottom of the cage measured with a small isotropic electric probe exhibited a variation of ± 3 dB between the center and the corners of the cage. The SAR values were determined by means of computer simulations with MAFIA software using an anatomically correct model of the body of a rat. The varying dielectric properties of the animal tissues lead to an uncertainty of less than 20%. Because of a resonance effect due to the body length (excluding the tail) of young animals being approx. half the wavelength of the RF signal, the amount of energy absorbed by them is higher than that for older animals, and the SAR for the whole body was bound to decline continuously during the course of the experiment.

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:
  • milk line
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 radiofrequency field did not affect the development of DMBA-induced mammary tumors, but a statistically significantly delayed median latency was found for malignant tumors in one of three experiments.

研究の種別:

研究助成

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