Study type: Medical/biological study (experimental study)

Effects of continuous and intermittent exposure to RF fields with a wide range of SARs on cell growth, survival, and cell cycle distribution. med./bio.

Published in: Bioelectromagnetics 2006; 27 (5): 392-400

Aim of study (acc. to author)

To study cell growth, cell survival, and cell cycle distribution following exposure to a wide range of SAR values. Furthermore, to determine whether non-thermal effects of radiofrequency irradiation influence cell proliferation at SAR levels at which the thermal effects are evident, the authors compared the effects of continuous exposure and intermittent exposure at high SAR values.

Background/further details

Temperature controls were performed at 39, 40, 41, 42, 43, and 44°C.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 2.45 GHz
Modulation type: CW
Exposure duration: continuous for 2 h
  • SAR: 0.05 W/kg maximum
  • SAR: 0.5 W/kg maximum
  • SAR: 5 W/kg maximum
  • SAR: 50 W/kg maximum
  • SAR: 100 W/kg maximum
  • SAR: 200 W/kg maximum
Exposure 2: 2.45 GHz
Modulation type: CW
Exposure duration: intermittent for 2 h, 1 s on/x s off, see exposure parameters
  • SAR: 50 W/kg mean
  • SAR: 300 W/kg peak value (5 s off)
  • SAR: 900 W/kg peak value (17 s off)
  • SAR: 1,500 W/kg peak value (29 s off)
Exposure 3: 2.45 GHz
Modulation type: CW
Exposure duration: intermittent for 2 h, 1 s on/x s off, see exposure parameters
  • SAR: 100 W/kg mean
  • SAR: 300 W/kg peak value (2 s off)
  • SAR: 900 W/kg peak value (8 s off)
  • SAR: 1,500 W/kg peak value (14 s off)

Exposure 1

Main characteristics
Frequency 2.45 GHz
Type
Exposure duration continuous for 2 h
Modulation
Modulation type CW
Exposure setup
Exposure source
  • waveguide
  • rectangular, 110 mm wide x 55 mm high x 310 mm long, operating in TE10 mode
Chamber The exposure unit was mounted in an incubator.
Setup A culture dish in which the medium stood 8 mm high was placed on two slits in the top wall of the waveguide. The slits were optimized with a pinched shape to increase the effective exposure area and enhance the uniformity of the electric field and the SAR distribution in the medium. One end of the waveguide was terminated with a short-circuiting plate to generate standing waves.
Sham exposure A sham exposure was conducted.
Additional info The temperatures of the medium at the maximum SAR position measured using a fibre optic thermometer rose to 39.1 °C, 41.0 °C, and 44.1 °C after exposure to 50, 100, and 200 W/kg, respectively, for 2 h at an ambient temperature of 37 °C. Cells for raised temperature control were incubated at 39, 40, 41, 42, 43, and 44 °C in a conventional incubator for the same time periods.
Parameters
Measurand Value Type Method Mass Remarks
SAR 0.05 W/kg maximum calculated - -
SAR 0.5 W/kg maximum calculated - -
SAR 5 W/kg maximum calculated - -
SAR 50 W/kg maximum calculated - -
SAR 100 W/kg maximum calculated - -
SAR 200 W/kg maximum calculated - -

Exposure 2

Main characteristics
Frequency 2.45 GHz
Type
Exposure duration intermittent for 2 h, 1 s on/x s off, see exposure parameters
Modulation
Modulation type CW
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
SAR 50 W/kg mean calculated - -
SAR 300 W/kg peak value calculated - 5 s off
SAR 900 W/kg peak value calculated - 17 s off
SAR 1,500 W/kg peak value calculated - 29 s off

Exposure 3

Main characteristics
Frequency 2.45 GHz
Type
Exposure duration intermittent for 2 h, 1 s on/x s off, see exposure parameters
Modulation
Modulation type CW
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
SAR 100 W/kg mean calculated - -
SAR 300 W/kg peak value calculated - 2 s off
SAR 900 W/kg peak value calculated - 8 s off
SAR 1,500 W/kg peak value calculated - 14 s off

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

When cells were exposed to a continuous radiofrequency electromagnetic field at SAR values from 0.05 to 100 W/kg for 2 h (field 1), cell growth, cell survival, and cell cycle distribution were not affected. At 200 W/kg, the cell growth was suppressed and cell survival decreased.
When the cells were exposed to an intermittent radiofrequency electromagnetic field at 300 W/kgpeak, 900 W/kgpeak and 1500 W/kgpeak (100 W/kgmean; cf. field 3), no significant differences in cell growth and cell survival were found.
Cells incubated at 43 and 44°C (temperature control) exhibited marked inhibition of cell proliferation.
When cells were exposed (continuous or intermittent) to a SAR of 50 W/kg for 2 h, the temperature of the medium rose to 39.1°C, 100 W/kg exposure increased the temperature to 41.0°C, and 200 W/kg exposure increased the temperature to 44.1°C.
Thus, exposure to radiofrequency exposure results in heating of the medium, and the thermal effect depended on the mean SAR. Hence, these results suggest that the cell proliferation disorder is caused by the thermal effect.

Study character:

Study funded by

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