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

[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] med./bio.

Human exposure at two radio frequencies (450 and 2450 MHz): similarities and differences in physiological response

著者: Adair ER, Cobb BL, Mylacraine KS, Kelleher SA
掲載誌: Bioelectromagnetics 1999; 20 Suppl 4: 12-20
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この研究は、450MHzまたは2450MHzの連続波の無線周波（RF）電磁界への45分間の全身ばく露をそれぞれ異なる7人の男女成人ボランティアグループに与え、熱産生と熱損失の体温調節反応を測定した。実験は、それぞれの周波数で、2つの電力密度（PD）のばく露を、それぞれ3種の環境温度（Ta＝24、28、31℃）で行った他、対照として3つのTaでRFなしで実験した。PDが同じ場合、被験者の背中中央表面のSARの標準化ピーク値に周波数による大きな違いはなかった（例えば、SAR = 6.0 および7.7 W/kg）。その結果、どちらの周波数においても、どのばく露条件でも、代謝的な熱産生に変化はなかった；照射面の皮膚温の増加の大きさは周波数に関連したが、背中と胸部の発汗速度はTaおよびPDにより強く関連した；発汗と皮膚血流増大が、深部体温(食道部)の調節（正常レベルの0.1℃以内）に貢献した；この2つの周波数では､ANSI/IEEE C95.1ガイドラインを超過する標準化ピークSAR値でも､通常の体温調節メカニズムにより難なく対処されることが示された、と報告している。

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研究目的（著者による）

To study thermoregulatory responses of heat production and heat loss in seven volunteers during exposure to 2450 MHz continuous wave radiofrequency fields.
The results of this study were compared to results of an earlier study at 450 MHz (publication 2256).

詳細情報

Two power densities were tested at each of three ambient temperatures (24, 28, and 31°C).

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

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
Additional information A report on the comparable earlier 450 MHz study (using identical procedures) can be found in the reference article.
Modulation
Modulation type CW
ばく露装置
ばく露の発生源／構造
Distance between exposed object and exposure source 1 m
チャンバの詳細 The electrically shielded anechoic chamber was 2.45 m x 2.45 m x 3.66 m. A small climate-conditioned cubicle of 1.47 m x 2.00 m x 2.06 m was created by a 5-cm thick Styrofoam partition.
ばく露装置の詳細 Subjects wearing a bathing suit sat in a light plastic chair with their back towards the 15-dB standard-gain horn antenna. The electric field vector was aligned with the long axis of the subject's body (E-polarization).
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 27 mW/cm² maximum 測定値 - -
SAR 5.94 W/kg maximum 測定値 - at the surface
電力密度 35 mW/cm² maximum 測定値 - -
SAR 7.7 W/kg maximum 測定値 - at the surface
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 few weeks during the course of the study.

測定および計算の詳細

Forward and reflected powers were monitored by power meters with the power sensors located in the waveguide between transmitter and antenna. Field uniformity at the subject's location was determined over two 65 x 80 cm planes centered on the boresight and at 1 and 1.5 m from the leading edge of the antenna using a broadband isotropic radiation detector fitted with an E-field probe. PD across the central 25 x 45 cm portion of each plane showed a 13% nonuniformity with the chair absent. Dosimetric evaluations were conducted on a 70-kg soft plastic mannequin model filled with simulated muscle tissue and placed on the chair [Adair et al., 1998]. After equilibration, the model was irradiated for 10 min at three PD values. The 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. (1998): [450 MHz無線周波への管理的全身ばく露を受けたヒトボランティアの熱生理学的反応]

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 alteration in metabolic heat production occurred under any irradiation conditions at either frequency (450 and 2450 MHz). The magnitude of increase in those skin temperatures under direct exposure was directly related to frequency, but local sweating rates on back and chest were related more to ambient temperature and SAR. Both efficient sweating and increased local skin blood flow contributed to the regulation of the deep body temperature to within 0.1°C of the baseline level.

研究の種別:

研究助成

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