Measurement and analysis of temperature rise caused by handheld mobile telephones using infrared thermal imaging

With the increase in the number of commercial mobile phones available and the longer periods these products are used in close proximity to the human body, concern has grown about the possible health hazard from exposure to RF electromagnetic radiation (EMR). Mobile phone users often complain about burning sensations or heating of the ear region. The increase in temperature may due to thermal insulation by the phone, conduction of the heat produced in the phone by battery currents and running of the radio frequency (RF) electronic circuits, and electromagnetic field (EMF) energy absorbed by the user's head. This study investigates local heating effects of the skin region including ear-skull area that handheld mobile phones can cause in humans. The goal is to visualize, quantify, and compare these thermal effects in various parameters condition and subjects using different commercial mobile phones in the normal contact position during standardized conversations. Infrared thermal imaging was used in this measurement and investigation. It is well suited to investigate temperature rises of the side of the face or the ear-skull region when using handheld mobile phones because it is able to accurately measure two-dimensional (2D) temperature fields with high thermal, temporal, and spatial resolutions Thermal imaging camera is capable of measuring local temperatures directly, as opposed to other methods, which can only derive temperatures if the electromagnetic near-field pattern of the phone, the energy-absorbing tissue properties, and the blood-flow situation are exactly known. The strength of local temperature rises is an indicator of the total exposure related to radiofrequency electromagnetic radiation from the mobile phone. Group of female subjects were used as samples. These subjects were requested to make a phone call on a standardized tone. Two different time durations were allocated to see the difference in the temperature rise. After 15 minutes of conversation, the mobile phone was removed to acquire thermal image on the right and left sides of ear-skull area. Then, the conversation was continued for another 15 minutes and the images for the same area were captured again. The temperature for both, the ear-skull area and temperature of the mobile front surface were captured after 30 minutes exposure to see the thermal equilibrium between these two temperatures. The entire captured images were collected and analyzed. It is shown in this study that different commercially available handheld mobile phones can cause very different thermal effects under identical experimental conditions. The measurement results are expected to help consumers in choosing those phones that cause the least thermal influences and biological effects. They might also help change the phone user's behavior in order to minimize the exposure to electromagnetic radiation.