Study type: Medical/biological study (experimental study)

Thermophysiological consequences of whole body resonant RF exposure (100 MHz) in human volunteers med./bio.

By: Adair ER, Mylacraine KS, Allen SJ
Published in: Bioelectromagnetics 2003; 24 (7): 489-501
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Aim of study (acc. to editor)

To measure thermophysiological responses of heat production and heat loss in adult volunteers during exposures.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 100 MHz
Modulation type: CW
Exposure duration: continuous for 45 min

General information

The RF exposure system, field measurements, and dosimetry are described in detail elsewhere [Allen et al., 2003].

Exposure 1

Main characteristics
Frequency 100 MHz
Type
Charakteristic
Exposure duration continuous for 45 min
Modulation
Modulation type CW
Exposure setup
Exposure source
Distance between exposed object and exposure source 2.25 m
Chamber The electrically shielded anechoic chamber was 6.7 x 6.7 x 9.8 m³ and contained a horizontal Fiberglas™ grid deck allowing placement of an antenna (tuneable dipole in a vertical 90° corner reflector) and a chair.
Setup Subjects wearing a bathing suit sat on a light plastic chair, elevated 53.8 cm above the grid floor, facing the rear chamber wall.
Sham exposure A sham exposure was conducted.
Additional info After 30 min of equilibration to the prevailing temperature (24, 28, or 31 °C), the subjects were exposed or sham exposed for 45 min.
Parameters
Measurand Value Type Method Mass Remarks
power density 4 mW/cm² mean measured - -
power density 6 mW/cm² mean measured - -
power density 8 mW/cm² mean measured - -
Additional parameter details

whole body SAR = 0.065 (or 0.068?) W/kg per mW/cm²

Measurement and calculation details

The RF field encompassing the total volume of the seated subject was mapped across three 80 x 80 cm planes (located 2.0, 2.25, and 2.5 m from the antenna) using both a calibrated isotropic survey meter and E-field and H-field probes. The FDTD method applied to a seated version of the 3-D Brooks AFB human dosimetry model resulted in a normalized whole body SAR for a 70 kg man of 0.13 W/kg per mW/cm². Dosimetric measurements on a 70 kg soft plastic man model filled with muscle equivalent material and seated in the plastic chair were made with non-perturbing temperature probes inserted to several depths at six locations. The SAR was determined separately for head, arm, leg, and trunk. From the sum of these individual SARs, the normalized whole body SAR was determined to be 0.065 (or 0.068?) W/kg per mW/cm², and the normalized peak SAR of 0.60 W/kg per mW/cm² was located in the center of the head.

Reference articles

  • Allen SJ et al. (2003): Empirical and theoretical dosimetry in support of whole body resonant RF exposure (100 MHz) in human volunteers

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • during exposure

Main outcome of study (acc. to author)

Local skin temperatures, even those on the back that were irradiated directly, changed little or not during 100 MHz exposures. The sole exception was the temperature of the ankle skin, which increased by 3-4°C in some subjects (power density = 8 mW/cm²). Thermoregulation was controlled by appropriate increases in sweating and by skin blood flow. Because of the deep penetration of resonant radiofrequency energy at this frequency (100 MHz), these changes must have been stimulated by thermal receptors deep the body rather than those located in the skin.

Study character:

Study funded by

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