The left image shows a top view of the electric field strength generated by a wireless transmitter in the region of a human head model. The right image shows the corresponding degree of absorption (SAR) of electromagnetic radiation by the head and neck. While the intensity nearest the antenna (the white region) may appear ‘high’, it is important to know what SAR value corresponds to that maximum intensity.
Effects of Wireless Devices on Human Health
DR LOUIS-RAY Harris, lecturer in the Department of Physics, UWI, Mona, has been conducting investigations on the effects of wireless devices on human health.
Dr Harris explains a point using a computer-generated model that shows the absorption of electromagnetic radiation inside the head when a cellphone is close to the ear.
Harris’ background is in wireless communications, and his current research is a follow-up to his PhD thesis which involved applying a large-scale numerical estimation method to radiowave propagation in large and complex indoor environments, as well as subsequent research that focused on the simultaneous use of devices such as cellphones and tablets, and their effects on the human body.
“My focus in this study is on the effects of wireless devices on the brain as the phone is a device that is used closest to the brain,” he told UWIMONA Now.
“From studies done worldwide, it is accepted that there is some relationship between electromagnetic (EM) radiation and heating. The signals transmitted by antennas in the phone are absorbed by tissues in the body, and this can have a heating effect on those tissues. So the concern has been whether or not the heating effect is linked to the formation of tumours in the brain,” Harris said.
His study focuses on the Specific Absorption Rate (SAR), which tells how much power from the EM radiation is absorbed per kilogramme of the body.
“Different phones and wireless devices have different SAR values. There are guidelines that dictate the maximum SAR a device should have, both for the US and EU markets. The guidelines place a restriction on the manufacturers of wireless devices to ensure that their devices comply with the respective limits,” he said.
In addition, he pointed out that the International Commission for Non-Ionising Radiation Protection (ICNIRP) also issued guidelines setting out the maximum allowable SAR values for wireless devices “to prevent excessive localised heating of human tissues”.
For his study, Harris used specialised software to do various simulations involving placing wireless devices at different positions around the body, and the software calculated the SAR values for different configurations. For the different configurations that were simulated, comparisons were made of the SAR values with the guidelines issued by the ICNIRP.
“The point of the study is to objectively investigate and model realistic scenarios and see what the results tell us. The results have shown that for the specific configurations that have been modelled to date, the SAR values are less than those recommended by the ICNIRP,” he said.
Nevertheless, Harris underscored the need for vigilance among consumers, noting that newer models of phones with higher SARs are constantly being developed. He said children were particularly vulnerable as the average child is exposed to a lot more EM radiation than before, especially given the increased mobile usage.
“More children are now using phones, and as their brains are not as developed as those of adults, the brain tissue is softer and there is greater absorption of the EM radiation,” he explained.
“What researchers have been trying to find out is what condition of EM radiation would result in adverse effects on human health. The composition of the tissue, the strength of the signal, the distance between the device and the tissue, as well as the duration of calls are all factors that contribute to increased absorption,” he added.
Harris plans to continue additional studies using different configurations and different environments to effectively determine the SAR. “I will be doing further studies with different configurations of devices. Based on my analysis of the data I already have, the threshold by the ICNIRP was not exceeded for these cases, and the test devices are within the ICNIRP limits. Tests have shown that the configurations of these devices used in the study are not harmful to human health,” he said.
However, Harris will be examining various other wireless devices to determine whether or not their use in different configurations would be harmful to human health. “This includes other non-phone devices that are used near the brain or clipped to the waist, wearable devices such as watches, devices attached to clothes, and eyeglasses that have wireless capabilities,” he said.
According to Harris, it is also important for people to be aware of the SAR values of their cellphones and tablet devices, which are usually included in the manual or on the manufacturers’ websites. All wireless devices should have SAR values that are less than the limits of 1.6 W/kg (US) and 2 W/kg (Europe). People should also limit the duration of calls where the phone is at the head for long periods, or use hands-free headsets.