Study type: Medical/biological study (experimental study)

Can exposure to a terrestrial trunked radio (TETRA)-like signal cause symptoms? A randomised double-blind provocation study. med./bio.

Published in: Occup Environ Med 2011; 68 (5): 339-344

Aim of study (acc. to author)

To test whether exposure to a continuous wave signal at 385.25 MHz or a TETRA-like signal resulted in acute symptoms among regular TETRA users reporting sensitivity to TETRA compared to users not reporting sensitivity to TETRA.

Background/further details

60 sensitive and 60 non-sensitive participants were exposed to three 50 minutes conditions: a signal with a 16 Hz component, a continuous wave condition and a sham exposure. Questionnaires were completed before exposure and after 5, 15, 30 and 50 minutes during the exposure. After a resting period of 30 minutes, the participant was asked whether he thought the radio had emitted a signal and how confident he was about this.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 385.25 MHz
Modulation type: CW
Exposure duration: continuous for 50 min
  • power: 250 mW mean
  • SAR: 1.3 W/kg maximum (10 g) (close to the antenna)
  • SAR: 0.3 W/kg average over mass (10 g) (from the handset body)
Exposure 2: 385.25 MHz
Modulation type: pulsed
Exposure duration: continuous for 50 min
  • power: 250 mW mean
  • SAR: 1.3 W/kg maximum (10 g) (close to the antenna)
  • SAR: 0.3 W/kg average over mass (10 g) (from the handset body)
  • power: 1 W peak value

Exposure 1

Main characteristics
Frequency 385.25 MHz
Type
Exposure duration continuous for 50 min
Modulation
Modulation type CW
Exposure setup
Exposure source
Setup handset attached to the test person's head via a headband so that the antenna was positioned above and slightly behind the left ear within a few millimeters of the head
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
power 250 mW mean - - -
SAR 1.3 W/kg maximum - 10 g close to the antenna
SAR 0.3 W/kg average over mass - 10 g from the handset body

Exposure 2

Main characteristics
Frequency 385.25 MHz
Type
Exposure duration continuous for 50 min
Modulation
Modulation type pulsed
Repetition frequency 16 Hz
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
power 250 mW mean - - -
SAR 1.3 W/kg maximum - 10 g close to the antenna
SAR 0.3 W/kg average over mass - 10 g from the handset body
power 1 W peak value - - -

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated material:
Time of investigation:
  • before exposure
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

Exposure to the continuous wave signal increased ratings of headache in all participants, fatigue in non-sensitive participants and difficulty concentrating in sensitive participants. Paradoxically, exposure reduced sensations of itching in sensitive participants. These effects were not observed in the condition with 16 Hz pulsing (TETRA-like), except for those relating to concentration. Statistical analysis (multiple comparisons) removed most significant effects, but not those relating to itch.
Neither sensitive nor non-sensitive participants could discriminate between the exposures during the experiment, nor could they tell which session was most likely to have been sham exposure or which was most likely to have been TETRA.
In conclusion, these data suggest that exposure to TETRA signals is not responsible for symptoms reported by some users, although exposure to a continuous wave signal may affect symptoms.

Study character:

Study funded by

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