There have also been fears about the amount of microwave radiation emitted, both by the mobiles themselves and their transmitters.
So are mobile phones safe?
Nobody really knows the answer to this question and it has been the subject of fierce debate for many years.
There is currently no definitive scientific evidence to suggest that mobile phones pose a risk to health - although some studies have raised concerns.
A far more proven safety problem with mobiles is that the temptation to make calls on the move can lead people into trouble, particularly when driving.
On 1 December 2003 a new law came into force to prohibit drivers using a hand-held mobile phone, or similar device, while driving.
Phones in cars can have many benefits. They provide security and help in an emergency. However, they are distracting if used when driving and this increases the risk of a crash.
In 2005 it's illegal to use a hand-held mobile phone when driving, even when you're stopped at traffic lights or in a queue of traffic. This includes making or receiving calls, pictures, text messaging or accessing the Internet. The rule is you must pull over to a safe location.
The law says risk using a hand-held mobile phone when driving, and you risk a fine!
Mobile phones receive their calls on radio frequency (RF) waves, which are in the Ultra High Frequency (UHF) band also used by television and some radar transmissions.
Excessive exposure to high levels of UHF radiation can cause heating (microwave ovens exploit this effect). There are also unproven claims that such radiation can cause cancers and brain damage.
All mobile phones sold in Britain now carry health warnings about excessive use, particularly for children. This follows an official inquiry, chaired by Sir William Stewart, during 1999/2000.
Stewart's Inquiry found no evidence that mobile phone use damaged health, but neither could it prove it was harmless. He is now chairing an independent task force carrying out further investigations.
One source of radio frequency (RF) radiation with mobiles is the transmitter that relays the signals. Most experts agree this threat is negligible, since the aerials do not beam directly downwards and in any case the degree of thermal radiation drops off as a cube of the distance from the transmitter (the radiation at ten metres away is only one thousandth what it was within one metre, dropping to one eight thousandth at 20 metres).
To receive a dangerous dose of radiation, one would need to be standing almost touching the transmitting antenna.
Fears have also been raised about the subtle effects of low-level radiation and electromagnetic fields around antennas but these are very hard to quantify and Government tests published in 2002 indicated no cause for concern. Nevertheless, research to identify the future direction of mobile phone technology, its safety and the future needs for mast development continues.
