Study type: Medical/biological study (experimental study)

Metabolic and vasomotor responses of rhesus monkeys exposed to 225-MHz radiofrequency energy med./bio.

By: Lotz WG, Saxton JL
Published in: Bioelectromagnetics 1987; 8 (1): 73-89
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Aim of study (acc. to author)

A previous study (Publikation 2260) showed a substantial increase in the colonic temperature of rhesus monkeys exposed to radiofrequency fields at a frequency near whole body resonance and specific absorption rates of 2-3 W/kg. The present study was conducted to determine the metabolic and vasomotor responses during exposures to similar radiofrequency fields.

Background/further details

The monkeys were exposed at two ambient temperatures, either cool (20°C) or thermoneutral (26°C).

Endpoint

Exposure

Exposure Parameters
Exposure 1: 225 MHz
Modulation type: CW
Exposure duration: intermittent, 10 min on / 10-60 min off (until skin temperature returned to within 0.3°C of its pre-exposure value)
Exposure 2: 225 MHz
Modulation type: CW
Exposure duration: continuous for 120 min
  • SAR: 400 µW/g mean (whole body)
  • SAR: 700 µW/g mean (whole body)
  • SAR: 1.4 mW/g mean (whole body)
  • SAR: 2.1 mW/g mean (whole body)
  • SAR: 2.9 mW/g mean (whole body)
  • power density: 12 W/m² minimum (at 26°C ambient temperature)
  • power density: 50 W/m² unspecified (at 20°C and 26°C ambient temperature)
  • power density: 100 W/m² unspecified (at 20°C ambient temperature)
  • power density: 25 W/m² unspecified (at 20°C and 26°C ambient temperature)
  • power density: 75 W/m² unspecified (at 20°C and 26°C ambient temperature)

Exposure 1

Main characteristics
Frequency 225 MHz
Type
Charakteristic
Polarization
Exposure duration intermittent, 10 min on / 10-60 min off (until skin temperature returned to within 0.3°C of its pre-exposure value)
Additional info First series of experiments. E-orientation.
Modulation
Modulation type CW
Exposure setup
Exposure source
Distance between exposed object and exposure source 2.4 m
Chamber Anechoic chamber/ 3.3 m x 3.3 m x 6.7 m; Styrofoam microchamber maintained at 26°C, 50% relative humidity or 20°C, 65% relative humidity
Setup Monkeys restrained in a foamed polystyrene chair and the whole setup was enclosed in a Styrofoam microchamber.
Additional info The electric field parallel to the long axis of the body.
Parameters
Measurand Value Type Method Mass Remarks
power density 12 W/m² minimum measured - -
power density 50 W/m² unspecified measured - -
power density 75 W/m² unspecified measured - -
power density 100 W/m² unspecified measured - -
power density 125 W/m² maximum measured - -
power density 25 W/m² unspecified measured - -
Additional parameter details

Average whole body SAR calculated over the region occupied by the monkey: 0.285 (W/kg)/(mW/cm²).

Exposure 2

Main characteristics
Frequency 225 MHz
Type
Charakteristic
Polarization
Exposure duration continuous for 120 min
Additional info Second series of experiments. E-orientation.
Modulation
Modulation type CW
Exposure setup
Exposure source
Distance between exposed object and exposure source 2.4 m
Parameters
Measurand Value Type Method Mass Remarks
SAR 400 µW/g mean calculated whole body -
SAR 700 µW/g mean calculated whole body -
SAR 1.4 mW/g mean calculated whole body -
SAR 2.1 mW/g mean calculated whole body -
SAR 2.9 mW/g mean calculated whole body -
power density 12 W/m² minimum measured - at 26°C ambient temperature
power density 50 W/m² unspecified measured - at 20°C and 26°C ambient temperature
power density 100 W/m² unspecified measured - at 20°C ambient temperature
power density 25 W/m² unspecified measured - at 20°C and 26°C ambient temperature
power density 75 W/m² unspecified measured - at 20°C and 26°C ambient temperature

Reference articles

  • Lotz WG (1985): Hyperthermia in radiofrequency-exposed rhesus monkeys: a comparison of frequency and orientation effects

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

Metabolic and vasomotor adjustments in the animals exposed to 225 MHz occurred during brief (10 min) or sustained (120 min) exposures at SARs at or above 1.4 W/kg. The SAR required to produce a given response varied with ambient temperature; metabolic and vasomotor responses were coordinated effectively to produce a stable deep body temperature.
The data show that the thermoregulatory response of the rhesus monkey to a radiofrequency exposure at a resonant frequency limits storage of heat in the body. However, substantial increases in colonic temperature were not prevented by such responses, even in a cool environment.

Study character:

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