Study type: Medical/biological study (experimental study)

Spontaneous and nitrosourea-induced primary tumors of the central nervous system in Fischer 344 rats chronically exposed to 836 MHz modulated microwaves. med./bio.

Published in: Radiat Res 1999; 152 (3): 293-302

Aim of study (acc. to author)

To evaluate whether the TDMA (Time Division Multiple Access) cellular phone met some of the defining criteria of known neurocarcinogenic agents (in this case ENU (ethylnitrosourea, a carcinogen)) in an animal model which include 1) a consistent capability to increase tumor incidence, 2) a reduction in latent period, 3) establishment of a direct dose-effect relationship, 4) a shift toward more anaplastic tumor types, and 5) an increased susceptibility of fetal tissues to neurocarcinogens compared with adult tissues.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 836.55 MHz
Modulation type: pulsed
Exposure duration: continuous for about 25 days, see add. information
-
Exposure 2: 836.55 MHz
Modulation type: pulsed
Exposure duration: repeated daily intermittent exposure, 7.5 min on/off, 2h/day, 4 days/week for up to 680 days, see add. information
  • power: 2.5 W (± 0.1 W)
  • SAR: 1.4 W/kg average over mass (brain) (male 250 g at 30 cm)
  • SAR: 1.2 W/kg average over mass (brain) (male 450 g at 45 cm)
  • SAR: 1.1 W/kg average over mass (brain) (female 150 g at 30 cm)
  • SAR: 1 W/kg average over mass (brain) (female 250 g at 45 cm)

General information

Rats were assigned to four experimental groups: Sham/Sham, Sham/Field, ENU/Sham and ENU/Field. A single dose of ENU was applied on gestation day 18 via the tail vein. Buffer alone was applied to the sham-injected groups.

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 pulsed
Duty cycle 33.33 %
Repetition frequency 50 Hz
Additional info

NADC with π/4 DQPSK

Exposure setup
Exposure source
Chamber Far field conditions were simulated with an approx. plane wave in a large tapered horn radiator of square aperture (2 x 2 m²) and 4.2 m length (about 12 wavelengths). Circular polarization was achieved using crossed dipole antennae placed in front of a ground plane at the apex of the horn and phase-shifted antenna feeds.
Setup Rat cages were positioned (not randomized daily) in a vertically oriented 3 x 3 matrix at the aperture of the horn in a "target chamber" that was 2.5 m square and 1.5 m deep, and lined with RF-absorbing foam. Sham exposures were performed in a square chamber of identical dimensions and materials, but the tapered section was truncated to 58 cm.
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

No parameters are specified for this exposure.

Exposure 2

Main characteristics
Frequency 836.55 MHz
Type
Charakteristic
Polarization
  • unspecified
Exposure duration repeated daily intermittent exposure, 7.5 min on/off, 2h/day, 4 days/week for up to 680 days, see add. information
Modulation
Modulation type pulsed
Duty cycle 33.33 %
Repetition frequency 50 Hz
Additional info

NADC with π/4 DQPSK

Exposure setup
Exposure source
  • plastic-encapsulated half-wave sleeved dipole
Chamber Twelve carousel exposure platforms were used each with 10 rats confined in PVC tubular restraints of different sizes and oriented radially around a central antenna. The antennas of adjacent carousels were spaced 1.7 m apart. Sham exposure was performed in identical carousels located in a different room.
Setup The distance to the antenna from the tip of the nose was 30 mm from weaning to 120 days, and 45 mm thereafter.
Additional info Near field exposure began at age 33 days and was performed on 4 consecutive days weekly until termination of the experiment at 709-712 days of age (376 exposures in total).
Parameters
Measurand Value Type Method Mass Remarks
power 2.5 W - - - ± 0.1 W
SAR 1.4 W/kg average over mass calculated brain male 250 g at 30 cm
SAR 1.2 W/kg average over mass calculated brain male 450 g at 45 cm
SAR 1.1 W/kg average over mass calculated brain female 150 g at 30 cm
SAR 1 W/kg average over mass calculated brain female 250 g at 45 cm

Reference articles

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

The study shows no increased tumorigenesis in the mammalian CNS from exposure to TDMA signals. Overall, the TDMA field-exposed animals exhibited trends toward a reduced incidence of spontaneous CNS tumors and ENU (ethylnitrosourea)-induced CNS tumors.

Study character:

Study funded by

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