The Australian research focused on the thermal effects or specific absorption rate (SAR) of radio frequency radiation - a measure of its actual effects on brain tissue, whereas the earlier study simply looked at electromagnetic radiation levels.

BBC: Hands-free mobiles given safety boost

The concerns stem from the emissions of radio frequency (RF) radiation by both the handsets and the base stations that transmit and receive the signals.

BBC: Public Petitions Committee

The radiation just spread out into space - where it still is and can be detected as weak waves of radio frequency.

BBC: Pictures of the early Universe