Assessment of Public Exposure to Radiofrequency Radiations from Mobile Phone Base Stations and Handsets

Abstract

This thesis reports the results of radio frequency exposure level in the vicinity of fifty mobile phone base stations in Ghana. The measurements showed that a power density variation of as low as 0.01 uW/m2 to as high as 10pW/m2 for the frequency of 900 MHz. At a transmission frequency of 1800MHz, the variations of power densities were from 0.01 uW/m2 to 100pW/m2. The results generally showed that level of compliance with ICNIRP limit was about 0.01%. These results are much higher than results in other countries where there are radio frequency safety regulations in place for the installation of RF antennae. The temperature rise in human head caused by absorbed power in the form of SAR from mobile phones is computed using bio-heat equation approach. The SAR was computed for fifty mobile phone handsets that radiate at 900MHz and 1800MHz. The temperature rise in the human head were calculated and the results show that average SAR values of 0.42W/kg, 0.98W/kg, 1.7W/kg, and 1.94W/kg resulted in temperature rise of 0.14°C, 0.15°C, 0.17°C and 0.18°C respectively after l0 min. Using PMMA phantom the temperature changes in the human head at different frequencies there was 0.19°C change over the initial 20°C for the 1800MHz and at the 900 MHz the temperature change was 0.18°C. The results showed that PMMA phantom can be used to estimate temperature changes within the human head. The results presented in this work will help in the further development of criteria for exposure guidelines, and technique developed may be used to assess temperature rises in the head associated with SARs for different types of RF exposure.