Electromagnetic radiation and mobile phones
Many people are concerned about the effects of radiation from mobile phones or mobile phone base stations.
The former Health Protection Agency (HPA) issued guidelines about mobile phone safety. It aims to base these around ‘sound scientific evidence relating to established effects on human health’.
- radiate powers up to around 1/4 watt
- are held with the antenna around 2cm from the user’s head
- mostly expose the tissues of the head nearest to the phone’s antenna
- localised exposure is measured as the specific absorption rate (SAR) in the head
- guidelines advise that localised SAR should not exceed two watts per kilogram when averaged over any 10 grams of tissue and six minute period
- all phones sold in the UK have to be tested to ensure that they produce SARs below the above figure
- radiate powers up to around 100 watts
- antennas are typically tens of metres away from the general public
- exposure is more even over the body but at a very much lower level than with a phone
- the power density of the radio waves incident on the body is a good measure of whole-body exposure
- guidelines advise reference levels of either 4.5 watts or 9 watts per square metre depending on the frequency band
- in addition to their obligations under UK safety law, the network operators have voluntarily agreed to comply with lower international guidelines
- typical exposures at locations accessible to the public are thousands of times lower than guidelines