Study type: Medical/biological study (experimental study, theoretical study)

Heating and pain sensation produced in human skin by millimeter waves: comparison to a simple thermal model med./bio.

By: Walters TJ, Blick DW, Johnson LR, Adair ER, Foster KR
Published in: Health Phys 2000; 78 (3): 259-267
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Aim of study (acc. to author)

1) To determine the pain threshold for 94 GHz mm-wave irradiation in human subjects; 2) to extend earlier obeservations of the perception threshold for 94 GHz mm-wave irradiation; and 3) to develop a simple thermal model, based on the heat conduction equation, that would allow the accurate prediction of pain at other millimeter-wave frequencies.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 94 GHz
Modulation type: pulsed
Exposure duration: 3 s
  • power density: 950 mW/cm² minimum (1.05 W/cm², 1.15 W/cm², 1.25 W/cm², 1.35 W/cm², 1.45 W/cm², 1.55 W/cm², 1.65 W/cm²)
  • power density: 1.75 W/cm² maximum

Exposure 1

Main characteristics
Frequency 94 GHz
Exposure duration 3 s
Modulation
Modulation type pulsed
Additional info

1 kHz rectangular wave pulse train with varying duty cycles of 90 to 50% were used.
Exposure setup
Exposure source
Chamber Exposure chamber/ 90 cm wide x 90 cm long x 180 cm high.
Additional info A dielectric lens capable of focusing the output of the horn into a 4 cm diameter beam. The lens had a focal length of 90 cm and was placed 90 cm from the antenna. The lens was situated at 188 cm from the aperture of the exposure chamber.
Parameters
Measurand Value Type Method Mass Remarks
power density 950 mW/cm² minimum measured - 1.05 W/cm², 1.15 W/cm², 1.25 W/cm², 1.35 W/cm², 1.45 W/cm², 1.55 W/cm², 1.65 W/cm²
power density 1.75 W/cm² maximum measured - -
Additional parameter details

4 cm diameter of the skin area was exposed. IR exposure was also applied with the IR camera 190 cm away from the apreture of the exposure chamber.

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

The study reports the thresholds for painful cutaneous sensation during stimulation by mm-wavelength microwaves, together with an analysis of the thermal response of skin in terms of a simple heat-conduction model. The data are in good agreement with the thermal model, with parameter values that agree well with those that have been reported in literature. The model may provide a basis for estimating the thresholds for pain and for perception of microwave energy over a large range of frequencies and exposure times.

Study character:

Study funded by

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