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

[IEEE C95.1基準を上回るレベルの2450 MHzCWエネルギーへの人体ばく露は深部体温を上昇させない] med./bio.

Human exposure to 2450 MHz CW energy at levels outside the IEEE C95.1 standard does not increase core temperature

著者: Adair ER, Mylacraine KS, Cobb BL
掲載誌: Bioelectromagnetics 2001; 22 (6): 429-439
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この研究は、局所的人体ばく露のIEEE C95.1ガイドライン値を大きく超えるレベルの2450MHzで、ボランティアによるばく露実験を、倫理審査会の許可を得て実施した。局所ばく露実験に用いたのは、50および70mW/cm2である（70mW/cm2では、全身SAR推定値はおよそ1.0W/kgとなる）。7人のボランティア（男性4人、女性3人）は、3つの環境温度（Ta=24、28、31℃）管理下で、2つのPDへばく露した（30分間ベースライン、45分間RFばく露または擬似ばく露、10分間ベースライン）。熱産生と熱損失の体温調節反応（食道および皮膚6部位の温度、代謝熱産生、局所皮膚血流、局所発汗速度）を測定した。同様の方法で1999年に測定した、PD=0,27、35mW/cm2の結果と合わせて、PDについての反応関数を作成した。その結果、PD=70mW/cm2では、背中上部（直接の照射面）の皮膚温度が、Ta=24℃で4.0℃、Ta=28℃で2.6℃、Ta＝31℃で1.8℃上昇した；これらの違いは主に局所発汗速度上昇（Ta＝31℃で最高）による；背中の局所皮膚血流も、PD=70mW/cm2では、Ta=31℃でベースライを65％上回り、Ta＝24℃では40％の上昇だった；RFばく露がC95.1ガイドライン値を超えると、Taが重要な変数になるものの、血流と発汗により体温恒常性は効果的に維持される、と報告している。

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研究目的（著者による）

To study human thermoregulatory effciency in radiofrequency environments.
Permission was received to exceed the peak power density (35 mW/cm²) the authors had previously studied during partial body exposure of human volunteers at 2450 MHz (publication 2287).

詳細情報

Two additional peak power densities were tested (50 and 70 mW/cm²) at each of three ambient temperatures (24, 28, and 31°C). The thermophysiological data were combined with comparable data at power densities of 0, 27, and 35 mW/cm² from the previous study to generate response functions across power densities.

影響評価項目

ばく露

ばく露 パラメータ
ばく露1: 2,450 MHz
Modulation type: CW
ばく露時間: continuous for 45 min
  • 電力密度: 50 mW/cm² maximum
  • SAR: 11 W/kg maximum (at the surface)
  • 電力密度: 70 mW/cm² maximum
  • SAR: 15.4 W/kg maximum (at the surface)
  • SAR: 1 W/kg average over mass (whole body)

General information

Details of the exposure system, field measurements, and dosimetry appear in two earlier publications [Adair et al., 1999].

ばく露1

主たる特性
周波数 2,450 MHz
タイプ
  • electromagnetic field
特性
  • far field
ばく露時間 continuous for 45 min
Modulation
Modulation type CW
ばく露装置
ばく露の発生源／構造
チャンバの詳細 The subject's immediate environment was climate controlled for temperature, relative humidity, and air movement.
ばく露装置の詳細 Subjects wearing a bathing suit sat on a light plastic chair, facing the rear chamber wall.
Sham exposure A sham exposure was conducted.
Additional information After 30 min of equilibration to the prevailing temperature (24, 28, or 31 °C), the subjects were exposed or sham exposed for 45 min.
パラメータ
測定量 値 種別 Method Mass 備考
電力密度 50 mW/cm² maximum 測定値 - -
SAR 11 W/kg maximum 測定値 - at the surface
電力密度 70 mW/cm² maximum 測定値 - -
SAR 15.4 W/kg maximum 測定値 - at the surface
SAR 1 W/kg average over mass 推定値 whole body -
Additional parameter details

Power densities (PD) specified above were determined with the E-field probe placed on the antenna boresight at the location of the subject's center back. These PDs were verified every 2-3 weeks as the study progressed.

測定および計算の詳細

The PD was mapped extensively in the vicinity of the subject's chair [Adair et al., 1999]. A central 25 x 45 cm portion of a 65 x 80 cm plane at the location of the subject's back showed a 13% nonuniformity, with the chair absent. Dosimetric measurements were conducted on a 70-kg soft plastic mannequin filled with muscle equivalent material. The normalized maximum surface SAR of 0.22 W/kg per mW/cm² was calculated from the greatest temperature rise occurring at the lower back [Chou et al., 1996, publication 1466].

Reference articles

  • Adair ER et al. (1999): [2つの無線周波（450および2450 MHz）への人体のばく露：生理学的反応の類似と差異]

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）

No change in deep body core temperature or metabolic heat production was recorded at any power density in any ambient temperature.
At a power density of 70 mW/cm², skin temperature on the upper back (irradiated directly) increased 4.0°C in ambient temperature of 24°C, 2.6°C in ambient temperature of 28°C, and 1.8°C in ambient temperature of 31°C. These differences were primarily due to the increase in local sweat rate, which was greatest in ambient temperature of 31°C.
Also at a power density of 70 mW/cm², local skin blood flow on the back increased 65% over baseline levels in ambient temperature of 31°C, but only 40% in ambient temperature of 24°C.
Although ambient temperature becomes an important variable when radiofrequency exposure exceeds the IEEE C95.1 guideline partial body exposure limits, vigorous heat loss responses of blood flow and sweating maintain thermal homeostasis efficiently.

研究の種別:

研究助成

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