Study type: Medical/biological study (experimental study)

Skin temperature increase caused by a mobile phone: A methodological infrared camera study med./bio.

By: Straume A, Oftedal G, Johnsson A
Published in: Bioelectromagnetics 2005; 26 (6): 510-519
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Aim of study (acc. to author)

The main aim of the study was to use experimental methods and an infrared camera to study how much the radiofrequency fields, the insulation (mobile phone was switched off) and the "electrical heating" (radiofrequency energy was absorbed) contribute to the rise in skin temperature during a mobile phone call.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 902.4 MHz
Modulation type: pulsed
Exposure duration: repeated exposure for 30 min, 6 times per day, on 5 consecutive days, see add. information
  • power: 0.21 W mean (maximum output power)
  • SAR: 0.81 W/kg average over mass (1 g) (in the cheek area)
  • SAR: 0.7 W/kg average over mass (1 g) (in the ear area)
  • power: 2 mW mean (minimum output power)

Exposure 1

Main characteristics
Frequency 902.4 MHz
Type
Exposure duration repeated exposure for 30 min, 6 times per day, on 5 consecutive days, see add. information
Modulation
Modulation type pulsed
Additional info

DTX mode was not activated.
Exposure setup
Exposure source
Chamber Faraday cage constructed of aluminium plates
Setup The subject held the phone in soft contact with the pinna with the phone touching only the uppermost part of the cheek, hence there was a small gap between the phone and most of the cheek. The display of the phone was masked, and a plastic bag, taped to the top of the phone, covered the load and the cable.
Additional info The following power conditions were used: mobile phone switched off, mobile phone switched on at minimum and at maximum output power. All three conditions were applied both with the phone in the normal configuration and with the antenna being replaced by a 50 Ohm load to absorb the RF energy. When the 50 Ohm load was used, the SAR did not exceed the background level. The study was conducted on five consecutive days, each with six 30 min exposure sessions. The order of the different exposure conditions was changed (double-blind) from day to day. After five days, each condition had been presented at all the different times of the day. In addition, each condition had been preceded by each of the other conditions.
Parameters
Measurand Value Type Method Mass Remarks
power 0.21 W mean measured - maximum output power
SAR 0.81 W/kg average over mass measured 1 g in the cheek area
SAR 0.7 W/kg average over mass measured 1 g in the ear area
power 2 mW mean measured - minimum output power
Additional parameter details

SAR values indicated are spatial peak values at maximum output power.

Measurement and calculation details

The average output power was measured by a power meter in series with a power sensor coupled to the antenna gate of the phone. SAR measurements have been made by Wilen et al. (see reference article) using the same test phone as in this study.

Reference articles

  • Wilen J et al. (2003): Subjective symptoms among mobile phone users - A consequence of absorption of radiofrequency fields?

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • before exposure
  • after exposure

Main outcome of study (acc. to author)

The insulation of the mobile phone and the electrical heating of the phone caused by power dissipation lead to statistically significant rises in the skin temperature, while the radiofrequency exposure did not.

Study character:

Study funded by

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