Study type: Medical/biological study (experimental study)

Cytogenetic damage in human lymphocytes following GMSK phase modulated microwave exposure med./bio.

By: d'Ambrosio G, Massa R, Scarfi MR, Zeni O
Published in: Bioelectromagnetics 2002; 23 (1): 7-13
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Aim of study (acc. to author)

To study whether exposure to a microwave frequency used for mobile communication (unmodulated or in presence of phase only modulation) can cause modification of cell proliferation kinetics and/or genotoxic effects.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 1.748 GHz
Exposure duration: continuous for 15 min
  • SAR: 2.25 W/kg mean (± 0.87 W/kg)
  • SAR: 4.99 W/kg (± 0.24 W/kg)
Exposure 2: 1.748 GHz
Modulation type: CW
Exposure duration: continuous for 15 min
  • SAR: 2.25 W/kg mean (± 0.87 W/kg)
  • SAR: 5.02 W/kg (± 0.22 W/kg)

Exposure 1

Main characteristics
Frequency 1.748 GHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 15 min
Additional info GMSK
Modulation
Modulation type cf. additional info
Additional info

Only the GMSK (Gaussian minimum shift keying) phase modulation was applied to the signal at a modulating bit rate of 1/T = 270.833 kbit/s, and the 3 dB bandwidth was such that BT = 0.3. Voice modulation was simulated by a 9 bit pseudorandom sequence.
Exposure setup
Exposure source
Chamber The amplified microwave signal was fed through a coaxial isolator and a coaxial double bridge into the sample holder, a rectangular cavity (110 x 55 x 184 mm) made of two coax to rectangular waveguide adapters.
Setup The narrow side of the waveguide and the E field were horizontal, parallel to the culture liquid layer (10 ml contained in a 25 cm² rectangular Falcon plastic flask). Due to small differences in the volume and positioning of the samples, the incident power was adjusted at the beginning of each exposure to obtain nearly the same power loss in all 18 experiments (nine CW and nine GMSK).
Additional info A thermostated (35 ± 0.1 °C) water jacket surrounded the sample holder cavity. The sample temperature, on its own, was allowed to rise from 35 ± 0.1 °C to no more than 35.7 ± 0.1 °C at the end of the exposure. No sham exposure was performed. Unexposed control cultures were left in the incubator at 37 ± 0.2 °C.
Parameters
Measurand Value Type Method Mass Remarks
SAR 2.25 W/kg mean measured and calculated - ± 0.87 W/kg
SAR 4.99 W/kg - determined by power loss 10 g ± 0.24 W/kg
Measurement and calculation details

The incident, reflected, and transmitted RF powers were measured during the actual exposure using power sensors and power meters, and the power lost in the sample holder unit (sample included) was evaluated. From this, the power lost per unit mass of the sample (m = 10.4 g) was 5.02 ± 0.22 W/kg for the CW exposures and 4.99 ± 0.24 W/kg for the GMSK exposures. These evaluations were checked by means of calorimetric measurements, performed following the technique suggested by Allis et al. [1977]. Heating and cooling curves were recorded at nine different points of a dummy sample (culture medium alone) using point like thermocouples and temperature monitors. From the nine temperature curves, nine local SARs were calculated: the mean value was 2.25 W/kg, with an SD of 0.87 W/kg (minimum value 1.17 W/kg and maximum value 3.93 W/kg). These SAR values were considerably less than the total power lost per unit mass of the sample (see above), that included the losses of the sample holder structure. Due to the large uncertainties of SAR evaluations based on temperature measurements [Burkhardt et al., 1996], the mean value of power lost (~5 W/kg) can be assumed as an upper bound, actually never exceeded by the power absorbed by the sample.

Exposure 2

Main characteristics
Frequency 1.748 GHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 15 min
Modulation
Modulation type CW
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
SAR 2.25 W/kg mean measured and calculated - ± 0.87 W/kg
SAR 5.02 W/kg - determined by power loss 10 g ± 0.22 W/kg

Reference articles

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

A first set of experiments was performed by exposing the cultures to unmodulated (continuous wave) radiation and no significant difference was found (either in micronuclei or in cell proliferation kinetics). Other experiments were carried out by exposing the samples to phase modulated radiation, and a significant difference in micronuclei was found. This result would indicate a genotoxic effect of phase modulation.

Study character:

Study funded by

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