If you had cast the doubts about the safety of mobile phones to the back of your mind, then think again. Hand-held personal data assistants (PDAs) are about to bring these concerns firmly to the front. The way we use PDAs – holding them in front of our heads as opposed to against our ears – presents new challenges concerning the potential health risks of mobile devices.

Personal communication handsets such as PDAs emit and receive electromagnetic waves with frequencies between about 1.5 and 3 GHz, which is in the radio region of the spectrum. While we know that too much ultraviolet radiation can damage the skin and that gamma radiation should be avoided at all costs, relatively little is known about the biological effects – if any – of electromagnetic waves at radio frequencies.

New research now suggests that wearing glasses can dramatically change how much radiation the human head absorbs from hand-held mobile devices as Matthew Chalmers describes in the May edition of Physics World. Matthew Chalmers is Features Editor of Physics World