Abstract

The bioheat equation is solved for an anatomically based model of the human head with a resolution of 2.5 × 2.5 × 2.5 mm to study the thermal implications of exposure to electromagnetic (EM) fields typical of cellular telephones at 900 MHz.Attention has first been posed on a particular phone model, and a comparison between the absorbed power distribution and steady-state temperature increases has been carried out. The antenna output power was set to be consistent with the portable telephones of 600 mW, maximum SAR values, averaged over 1 gm, from 2.1 to 3.6 W/kg depending on the considered phone. The maximum temperature increases are obtained in the ear and vary from 0.22°C to 0.39°C, while the maximum temperature increases in the brain lie from 0.07°C to 0.17°C. These steady-state temperature increases are obtained after about 48 min of exposure, with a time constant of approximately 6 min. Application of the ANSI/IEEE safety guidelines restricting the 1 gm averaged spatial peak SAR to 1.6 W/kg results in the maximum temperature rise in the brain from 0.07°C to 0.15°C at 900 MHz. Finally, considerations about the exposure limits in the considered studied frequency are made.

Key words: Electromagnetic wave polarization, electromagnetic heating, finite-difference time-domain method, mobile phone, specific absorption rate, temperature increase.