Study type: Medical/biological study (experimental study)

Expression of the proto-oncogene Fos after exposure to radiofrequency radiation relevant to wireless communications. med./bio.

Published in: Radiat Res 2005; 164 (4): 420-430

Aim of study (acc. to author)

To determine whether there was a dose-response relationship of radiofrequency irradiation on c-Fos expression by exposing cells to higher SARs.

Background/further details

This study was undertaken to confirm a previous work (see publication 3649) where CDMA and FDMA irradiation caused small but statistically significant increases in Fos levels as cells entered plateau phase during exposure. If radiofrequency irradiation increases Fos expression during transition from exponential to plateau phase, such a response should be dependent on the energy delivered.
In the present study, analyses were restricted to Fos expression during the transition from exponential growth to plateau phase. The effect of TDMA signal modulation in addition to those of CDMA and FDMA was also determined.
Serum-stimulated cells were used as a positive control.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 847.74 MHz
Exposure duration: continuous for 4 days
  • SAR: 5.2 W/kg average over time (± 2.2 W/kg)
  • SAR: 10 W/kg average over time (± 4.1 W/kg)
Exposure 2: 835.62 MHz
Exposure duration: continuous for 4 days
  • SAR: 5.2 W/kg average over time (± 2.2 W/kg)
  • SAR: 10 W/kg average over time (± 4.1 W/kg)
Exposure 3: 836.55 MHz
Exposure duration: continuous for 4 days
  • SAR: 5.2 W/kg average over time (± 2.2 W/kg)
  • SAR: 10 W/kg average over time (± 4.1 W/kg)

Exposure 1

Main characteristics
Frequency 847.74 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 4 days
Additional info CDMA
Modulation
Modulation type cf. additional info
Additional info

CDMA

Exposure setup
Exposure source
Chamber The exposure system consisted of an environmentally enclosed room containing nine radial transmission lines (RTL). A detailed description of the RTL irradiator and its environmental controls has been given in several publications (see reference articles). Each RTL was formed by two horizontal parallel conductive plates 4.3 cm apart, with a lightweight composite top plate hinged to the bottom aluminium plate (6 mm thick) providing mechanical support and minimizing temperature gradients among flasks. A central conical aluminium antenna emitted TEM waves radially outward that were terminated by an annulus of RF-absorbing foam braced by a thin lamina of perforated aluminium located 53.3 cm from the antenna's center.
Setup A total of 16 T-75 culture flasks each containing 40 ml of medium (5 mm deep) were distributed angularly around the antenna with their centers located at a radius of 29.2 cm. The nominal distances of the cell layer from the antenna's center were between 24.7 and 33.8 cm. To boost and homogenize the SAR distribution, each flask was dielectrically loaded with a 3-mm-thick shim of alumina (Al2O3) ceramic that fit snugly under the skirt of the flask.
Sham exposure A sham exposure was conducted.
Additional info The flasks were separated into four groups: RTL shams, RTL exposed, start-of-run incubator controls (day 0), and end-of-run incubator controls (day 4). The flasks for simultaneous sham exposure were handled in the same way as the flasks exposed to RF radiation but RTLs were not connected to an RF field source. The mean temperature of the culture medium was maintained at 37 ± 0.3°C with the temperature of each RTL being monitored continuously. However, thermometric measurements revealed bell-shaped temperature profiles along orthogonal axes on the bottom of a flask exposed at 10.0 W/kg with thermal gradients as large as 0.5°C/cm, implying that the cell layer sustained a temperature distribution over a range of ± 1°C which must be taken into consideration in the experimental design and/or interpretation of results.
Parameters
Measurand Value Type Method Mass Remarks
SAR 5.2 W/kg average over time measured - ± 2.2 W/kg
SAR 10 W/kg average over time measured - ± 4.1 W/kg

Exposure 2

Main characteristics
Frequency 835.62 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 4 days
Additional info FDMA
Modulation
Modulation type cf. additional info
Additional info

FDMA

Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
SAR 5.2 W/kg average over time measured - ± 2.2 W/kg
SAR 10 W/kg average over time measured - ± 4.1 W/kg

Exposure 3

Main characteristics
Frequency 836.55 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 4 days
Additional info TDMA
Modulation
Modulation type cf. additional info
Additional info

TDMA

Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
SAR 5.2 W/kg average over time measured - ± 2.2 W/kg
SAR 10 W/kg average over time measured - ± 4.1 W/kg

Reference articles

  • Pickard WF et al. (2000): Experimental and numerical determination of SAR distributions within culture flasks in a dielectric loaded radial transmission line.
  • Moros EG et al. (1999): The radial transmission line as a broad-band shielded exposure system for microwave irradiation of large numbers of culture flasks.
  • Moros EG et al. (1998): A compact shielded exposure system for the simultaneous long-term UHF irradiation of forty small mammals: I. Electromagnetic and environmental design.

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

Expression of Fos mRNA in the cells was not significantly different from that found after sham exposure at either SAR level for any signal modulation. Therefore, the data of Goswami et al. could not be confirmed.

Study character:

Study funded by

Replicated studies

Related articles