Laboratoire de physiologie cardio‐vasculaire, Avenue Kennedy, 30907 Nimes cedex 2, France <ggpina1aol.com>. CHU Gui‐de‐Chauliac, 2, avenue Émile Bertin Sans, 34 060 Montpellier cedex, France. Institut national de l‘environnement industriel et des risques (INERIS), Parc technologique ALATA, BP 2, 60550 Verneuil‐en‐Halatte, France <Rene.De‐Sezeineris.fr>
- Key words: temperature ; cellular phone ; electromagnetic fields.
- Page(s) : 279-83
- Published in: 2003
Cellular telephone use can be accompanied by a sensation of heat. Part of the radiofrequency radiation is absorbed by the user‘s head (40‐50%), with absorption highest in the skin. Calculation of temperature changes when the telephone is in contact with the ear shows that skin temperature rises by a maximum of 0.16°C at an average emitted power of 250 mW (SARmax over 10 g of 1.66 W\kg ‐‐ SARmax over 1 g of 2.22 W\kg). In comparison, the heating of the brain at that power ranges from 0.05°C to 0.11°C (SARmax over 1 g of 0.34 W\kg). We used a Luxtron 790 F optical‐fiber thermometer to measure the temperature increase of the skin at exposure to GSM 900 (900 MHz‐‐radiated power 250 mW) and GSM 1800 (1800 MHz‐‐radiated power 125 mW) signals. The sensors were placed in very precise positions directly across from one another, one on the telephone and the other on the volunteer‘s skin. The volunteer held the telephone by hand in a normal position of use. Temperature was recorded until a steady state was reached, with the battery on but the telephone not emitting ; this took 30 min. The steady‐state temperatures were 36.9 ± 0.3°C for GSM 900 and 37.4 ± 0.4°C for GSM 1800. The temperature of the telephone alone increased when it changed from this stabilized reception mode to a stabilized emission mode (measured at 18°C) by 4.4°C for GSM 900 and 2.8°C for GSM 1800. The difference in skin temperature between these modes (emission at full power, i.e., 250 mW for GSM 900 and 125 mW for GSM 1800) was 0.93 ± 0.24°C for GSM 900 and 0.66 ± 0.18°C for GSM 1800. Calculations showed that skin warming due to the electromagnetic field was approximately 0.16°C for an emitted power of 250 mW. Accordingly, about half the temperature difference measured is due to heat exchanges between telephone and skin. Further experiments will help quantify more precisely the amount of skin warming due to the electromagnetic field.