Study type: Medical/biological study (experimental study)

Thermophysiological responses of human volunteers to whole body RF exposure at 220 MHz med./bio.

By: Adair ER, Blick DW, Allen SJ, Mylacraine KS, Ziriax JM, Scholl DM
Published in: Bioelectromagnetics 2005; 26 (6): 448-461
Download citation in RIS format

Aim of study (acc. to author)

To study thermoregulatory responses of heat loss and heat production in six adult volunteers during 45 min whole body dorsal exposures to 220 MHz radiofrequency energy.

Background/further details

Since 1994, the authors' research has demonstrated how thermophysiological responses are mobilized in human volunteers exposed to three radiofrequencies, 100, 450, and 2450 MHz. A significant gap in this frequency range is now filled by the present study, conducted at 220 MHz.
Three power densities were tested at each of three ambient temperatures (24, 28, and 31°C).

Endpoint

Exposure

Exposure Parameters
Exposure 1: 220 MHz
Modulation type: CW
Exposure duration: continuous for 45 min

Exposure 1

Main characteristics
Frequency 220 MHz
Type
Charakteristic
Exposure duration continuous for 45 min
Modulation
Modulation type CW
Exposure setup
Exposure source
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 9 mW/cm² mean measured - -
SAR 0.41 W/kg mean measured whole body -
power density 12 mW/cm² mean measured - -
SAR 0.54 W/kg mean measured whole body -
power density 15 mW/cm² mean measured - -
SAR 0.68 W/kg mean measured whole body -
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 E-field and H-field probes, see Allen et al. [2005]. 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 0.70 W/kg per mW/cm². Dosimetric measurements on a 64.4 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 eight locations. The average normalized SAR was determined from two complete sets of measurements to be 0.045 W/kg per mW/cm². For details of the empirical and theoretical dosimetry, see Allen et al. [2005].

Reference articles

  • Allen SJ et al. (2005): Empirical and theoretical dosimetry in support of whole body radio frequency (RF) exposure in seated human volunteers at 220 MHz

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

No changes in metabolic rate occurred under any test condition, while esophageal temperature showed small changes but never exceeded 37.3°C. As with similar exposures at 100 MHz (see publication 10249), local skin temperature changed little and modest increases in local skin blood flow were recorded. At 220 MHz, vigorous sweating occurred at power densities of 12 and 15 mW/cm², with sweating levels higher than those revealed for equivalent power densities at 100 MHz.
Human exposure at both 220 and 100 MHz results in far less skin heating than occurs during irradiation at 450 MHz (see publication 2256). However, the exposed subjects thermoregulate efficiently because of increased heat loss responses, particularly sweating.

Study character:

Study funded by

Related articles