Study type: Medical/biological study (experimental study)

The effect of ambient temperature on the reduction of microwave energy absorption by mice med./bio.

By: Monahan JC, Ho HS
Published in: Radio Sci 1977; 12 (6S): 257-262
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Aim of study (acc. to author)

To examine the relationship between environmental temperature and 2.45 GHz continuous wave (CW) exposure on "avoidance" behavior of the mouse (the term "avoidance" is employed to indicate a behavior that results in a decreased rate of energy absorption).
If environmental temperature does influence the response to microwave irradiation, then the amount of irradiation that is necessary to produce "avoidance" should be altered as a function of changes in ambient temperature.

Background/further details

Mice were exposed by 2450 MHz CW microwaves in an environmentally controlled waveguide at temperatures of 20, 24, 30, or 35°C.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 2.45 GHz
Modulation type: CW
Exposure duration: 20 min
  • SAR: 63.8 mW/g maximum (30.7 mW/g - 63.8 mW/g at 20°C)
  • power: 3.84 W maximum (1.62 W - 3.84 W at 20°C)
  • power: 3.11 W maximum (1.12 W - 3.11W at 24°C)
  • SAR: 51.3 mW/g maximum (20.6 m W/G - 51.3 mW/g at 24°C)
  • power: 2.45 W maximum (0.415 W -2.45 W at 30°C)
  • SAR: 40.2 mW/g maximum (7.3 mW/g - 40.2 mW/g at 30°C)
  • SAR: 6.7 mW/g maximum (0.06 mW/g - 6.7 mW/g at 35°C)
  • power: 0.401 W maximum (0.004 W - 0.401 W at 35°C)

Exposure 1

Main characteristics
Frequency 2.45 GHz
Type
Exposure duration 20 min
Modulation
Modulation type CW
Exposure setup
Exposure source
  • circular waveguide
  • WR-430 10.0 cm x 5.5 cm, operated in TE10 mode
Setup Mouse was placed in a 2 mm Plexiglas container 10.3 cm x 4.4 cm x 14.7 cm, which was inserted into the waveguide
Parameters
Measurand Value Type Method Mass Remarks
SAR 63.8 mW/g maximum cf. remarks - 30.7 mW/g - 63.8 mW/g at 20°C
power 3.84 W maximum measured - 1.62 W - 3.84 W at 20°C
power 3.11 W maximum measured - 1.12 W - 3.11W at 24°C
SAR 51.3 mW/g maximum - - 20.6 m W/G - 51.3 mW/g at 24°C
power 2.45 W maximum measured - 0.415 W -2.45 W at 30°C
SAR 40.2 mW/g maximum - - 7.3 mW/g - 40.2 mW/g at 30°C
SAR 6.7 mW/g maximum - - 0.06 mW/g - 6.7 mW/g at 35°C
power 0.401 W maximum measured - 0.004 W - 0.401 W at 35°C

Reference articles

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

The results are consistent with the notion that microwave energy can serve as a noxious stimulus at low dose rates and will cause an animal to adopt a behavior to reduce the intensity of stimulation. The data also indicate that an increase in ambient temperature is associated with a reduction in the level of microwave irradiation that is necessary to produce "avoidance". The mice were decreasing their rate of absorbing microwave energy by orienting their bodies relative to the source of irradiation. The threshold level of power at which decreases in percent absorption were revealed was found to decrease with an increase in the environmental temperature. The results suggest that the animals were capable of detecting or otherwise reacting to microwave energy at dose rates as low as 0.6 mW/g when the environmental temperature was 35°C.

Study character:

Study funded by