Mobile phones and the inner ear

A new technique has been developed by researchers in the Netherlands to look at the effect of radiation from mobile phones on complex structures like the inner ear and eye. The technique called `quasistatic zooming` will help researchers calculate the amount of radiation from mobile phones absorbed by human tissue on scales of less than one millimetre. The work is published today in the Institute of Physics journal, Physics in Medicine and Biology.

Concern about the potentially hazardous effects of mobile phones on human tissue has led to a great deal of research on the subject. Using computer models of the head, the amount of electromagnetic radiation absorbed and the resulting increases in the temperature in the head have been calculated. One drawback of this research is that these computer models are very complicated and take a long time to do the calculations, so the models have to be simplified to make the experiments practical. To keep the experiment time down, the computer calculates the amount of radiation absorbed on two millimetre sections of the head, but Jeroen Van de Kamer and colleagues from the University of Utrecht are concerned that this resolution is too limiting.

“A resolution of two millimetres is adequate for studying the brain as it does not have small-scale intricate features, but this is not high enough to test how mobile phones affect the inner ear and eye,” said Dr Van de Kamer. “To find out what is going on here, high-resolution simulations are needed,” he added.

To make higher-resolution simulations, Dr Van de Kamer and Dr Lagendijk have developed a new technique that calculates the distribution of the absorbed radiation on a sub-millimetre scale from the conventionally computed, low-resolution distribution of the electric field. This `quasistatic zooming` allows the researchers to find the power distribution in the head, at a scale as low as 0.4mm, due to a radiating phone held next to the ear. Comparing their results with conventional calculations they found that the main part of the brain has the same power distribution due to the mobile phone, but the more intricate structures in the head absorbed the power of the mobile phone in a different way than had been seen before. For example, a thin sheet of cerebral spinal fluid around the brain was seen to absorb more radiation at the surface of the brain than had been seen with the 2 millimetre resolution computer model.

“It is clear from this that, for small scale structures, high-resolution electromagnetic modelling is a necessity”, said Dr Van de Kamer.

Although the maximum increase in temperature found in the head is less than 0.2 degrees centrigrade as it was with lower resolution computer models, research must now be done with this higher resolution technique to check the impact of mobile phones on the inner ear and eye and other small-scale parts of the head.