Use of hardware modified phones for exposure assessment in health studies in Australia: verification of compliance with standards.

ABSTRACT

Most epidemiological studies investigating health effects of mobile telephone use have been criticised for poor quality of exposure assessment. Most used questionnaires which have limited precision to assess exposure. Clearly more relevant and direct methods of exposure assessment are needed. We describe the calibration of hardware modified phones (HMPs) for exposure assessment and dosimetry and verified their compliance with Australian and international standards. Specific energy absorption rate (SAR) values at various tilts and rotations and their combinations were obtained for the HMPs using a 'DASY3' SAR measuring system. Calibration involved placing HMPs on human head phantoms and taking measurements at 900 and 1800 MHz bands on right and left sides of the phantom. At 900 MHz the maximum SAR obtained with HMPs at the touch position was 0.9 W/kg and 0.4 W/kg at 30 degrees tilt but at 1800 MHz, SAR at the touch and 30 degrees tilts were 1.1 W/kg and 1.3 W/kg respectively. Whilst tilt and rotation each had an effect on SAR at constant frequency, no interaction was observed with rotation and frequency, however one was observed between tilt and frequency. At 1800 MHz mean SAR at 30 degrees tilt was 0.22 W/kg higher (95% CI 0.15, 0.30) than at 0 degrees, whereas at 900 MHz mean SAR at 30 degrees tilt was 0.60 W/kg lower (95% CI 0.52, 0.67) than at 0 degrees. Our results indicated that tilts influence SAR more than rotations. SAR values obtained at both 900/1800 MHz for the HMPswere well below ICNIRP limits for the general public. The phones were compliant with both international and Australian standards.