Study type: Medical/biological study (experimental study)

Partial-body exposure of human volunteers to 2450 MHz pulsed or CW fields provokes similar thermoregulatory responses med./bio.

By: Adair ER, Mylacraine KS, Cobb BL
Published in: Bioelectromagnetics 2001; 22 (4): 246-259
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Aim of study (acc. to author)

To study thermoregulatory responses of heat production and heat loss in two different groups of volunteers during exposure to 2450 MHz radiofrequency fields (continuous wave and pulsed wave) at three ambient temperatures (24, 28, and 31°C).

Endpoint

Exposure

Exposure Parameters
Exposure 1: 2,450 MHz
Modulation type: CW
Exposure duration: continuous for 45 min
Exposure 2: 2,450 MHz
Modulation type: pulsed
Exposure duration: continuous for 45 min

General information

The 2450 MHz human exposure system, field measurements, and dosimetry have been described in detail in a previous publication [Adair et al., 1999].

Exposure 1

Main characteristics
Frequency 2,450 MHz
Type
Charakteristic
Exposure duration continuous for 45 min
Modulation
Modulation type CW
Exposure setup
Exposure source
Chamber The anechoic chamber was 2.45 m x 2.45 m x 3.66 m in which a small climate-conditioned cubicle was created by a 5-cm thick Styrofoam partition.
Setup Subjects wearing a bathing suit sat on a light plastic chair, 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 27 mW/cm² maximum measured - -
SAR 5.94 W/kg maximum measured - at the surface
power density 35 mW/cm² maximum measured - -
SAR 7.7 W/kg maximum measured - 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 each experiment.

Measurement and calculation details

A broadband isotropic radiation monitor, fitted with an E-field probe, was used to map the field at the location of the subject's chair [Adair et al., 1999]. PD measurements across the central 25 x 45 cm portion of a 65 x 80 cm plane at the location of the subject's back showed a nonuniformity of ~13% at CW and ~12% at PW exposure, 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 (W/kg per mW/cm²) was calculated from the greatest temperature rise occurring at the lower back [Chou et al., 1996].

Exposure 2

Main characteristics
Frequency 2,450 MHz
Type
Charakteristic
Exposure duration continuous for 45 min
Modulation
Modulation type pulsed
Pulse width 65 µs
Repetition frequency 10 kHz
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
power density 27 mW/cm² maximum measured - -
SAR 5.94 W/kg maximum measured - at the surface
power density 35 mW/cm² maximum measured - -
SAR 7.7 W/kg maximum measured - at the surface

Reference articles

  • Adair ER et al. (1999): Human exposure at two radio frequencies (450 and 2450 MHz): similarities and differences in physiological response
  • Chou CK et al. (1996): Radio frequency electromagnetic exposure: tutorial review on experimental dosimetry

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

Mean data for each group showed minimal changes in core temperature and metabolic heat production for all test conditions and no reliable differences between continuous wave and pulsed wave irradiation. Local skin temperatures showed similar trends for continuous wave and pulsed wave irradiation that were power density-dependent. Only the skin temperature of the upper back (facing the antenna) showed a reliably greater increase during pulsed wave exposure than during continuous wave exposure.
Local sweat rate and skin blood flow were both ambient temperature and power density-dependent and showed greater variability than other measures between continuous wave and pulsed wave irradiations; this variability was attributable primarily to the characteristics of the two different subject groups. With one noted exception, no clear evidence for a differential response to continuous wave and pulsed wave fields was revealed.

Study character:

Study funded by

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