Study type: Medical/biological study (experimental study)

Spontaneous and nitrosourea-induced primary tumors of the central nervous system in Fischer 344 rats exposed to frequency-modulated microwave fields. med./bio.

Published in: Cancer Res 2000; 60 (7): 1857-1863

Aim of study (acc. to author)

The study was designed as a 2-year bioassay to test the hypothesis that frequency modulated field exposure might alter either survival or CNS primary tumor incidence.

Background/further details

A life-long exposure was simulated, beginning with exposures of fetal and preweanling rats. A low dose of ENU (ethylnitrosourea, a carcinogen) was selected to give maximum sensitivity for detection of a modification of tumor incidence.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 836.55 MHz
Modulation type: FM
Exposure duration: continuous for about 25 days, see add. information
Exposure 2: 836.55 MHz
Modulation type: FM
Exposure duration: repeated daily exposure, 2h/day, 4 days/week, for up to 700 days, see add. information
  • power: 2.5 W mean (± 0.1 W)
  • SAR: 1.2 W/kg average over mass (brain) (male 450 g)
  • SAR: 0.27 W/kg average over mass (whole body) (male 450 g)
  • SAR: 1 W/kg average over mass (brain) (female 236 g)
  • SAR: 0.42 W/kg average over mass (whole body) (female 236 g)

General information

Rats were assigned to six groups: sham ENU + sham field, sham ENU + field, ENU + sham field, ENU + field, ENU + cage control, sham ENU + cage control. A single dose of ENU was applied on gestation day 18 via the lateral tail vein. Buffer alone was applied to the sham-injected groups. Exposure systems have been described in [Lai et al., 1996].

Exposure 1

Main characteristics
Frequency 836.55 MHz
Type
Charakteristic
Polarization
  • circular
Exposure duration continuous for about 25 days, see add. information
Modulation
Modulation type FM
Modulation frequency 12.5 kHz
Additional info

modulation by a recorded 2-min pattern of "balanced speech"

Exposure setup
Exposure source
Chamber Far field conditions were simulated with an approx. plane wave in a large tapered horn radiator.
Setup Rat cages were positioned in a vertically oriented 3 x 3 matrix at the square aperture (2 x 2 m²) of the horn. Sham exposures were performed in a square chamber of identical dimensions and materials.
Sham exposure A sham exposure was conducted.
Additional info Far field exposure of rats in their home cages began on gestation day 19 and continued until the pups were aged 21 days (about 25 days in total).
Parameters
Measurand Value Type Method Mass Remarks
power density 2.6 mW/cm² mean - - ± 0.5 mW/cm²

Exposure 2

Main characteristics
Frequency 836.55 MHz
Type
Charakteristic
Exposure duration repeated daily exposure, 2h/day, 4 days/week, for up to 700 days, see add. information
Modulation
Modulation type FM
Modulation frequency 12.5 kHz
Additional info

modulation by a recorded 2-min pattern of "balanced speech"

Exposure setup
Exposure source
Distance between exposed object and exposure source 45 mm
Chamber Twelve carousel exposure platforms were used each with 10 rats confined in plastic tubular restraints and oriented radially around a central antenna.
Setup The distance to the antenna from the tip of the nose was 30 mm from weaning to 120 days, and 45 mm thereafter.
Sham exposure A sham exposure was conducted.
Additional info Near field exposure began at age 31 days and was performed on 4 consecutive days weekly until termination of the experiment at 731-734 days of age (384 exposures in total).
Parameters
Measurand Value Type Method Mass Remarks
power 2.5 W mean - - ± 0.1 W
SAR 1.2 W/kg average over mass calculated brain male 450 g
SAR 0.27 W/kg average over mass calculated whole body male 450 g
SAR 1 W/kg average over mass calculated brain female 236 g
SAR 0.42 W/kg average over mass calculated whole body female 236 g

Reference articles

  • Burkhardt M et al. (1997): Exposure setup to test effects of wireless communications systems on the CNS.
  • Lai H et al. (1996): Single- and double-strand DNA breaks in rat brain cells after acute exposure to radiofrequency electromagnetic radiation.

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

There were no effects on incidence of either spontaneous or ENU-induced primary tumors of the CNS associated with lifetime exposure of rats to frequency modulated microwave fields simulating electrical characteristics of hand-held mobile telephone transmissions at the head of the user.

Study character:

Study funded by

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