Bev Pantry of Carmel College asks :-

My Year 13 students have asked how dangerous is the radiation when using cell phones or cordless phones. Is there something that you can buy to insert in the cell phone that absorbs/stops the radiation. If so how effective is this?

Martin Gledhill, a physicist at the Ministry of Health's National Radiation Laboratory, responded.

Cellphones and cordless phones are small, relatively low-powered radio transmitters. In use they produce radiofrequency (RF) signals, otherwise known as “RF radiation”. (This should not be confused with the radiation from x-ray equipment or radioactive sources, which is completely different in its physical properties and the way it interacts with the body.)

Because the body is mostly composed of electrically conductive fluid, it absorbs some of the energy in the RF radiation emitted by a cellphone. Ultimately that energy is transformed into heat – but in such tiny amounts that it would be extremely difficult if not impossible to detect. Video clips of cellphones boiling eggs or popping popcorn are simply special effects.

The effects of RF radiation on the body have been investigated extensively. While cellphones and cordless phones are relatively new, they are just applications of radio technology that has been around for a long time. Exposure standards to protect health have been developed from a review of the research data. Cellphones and cordless phones on sale in New Zealand comply with those standards.

One question often asked is whether cellphones cause brain tumours. Studies on cellphone users do not show an increased risk of brain tumours in people who have used cellphones for periods up to ten years. There is little known about effects on people who have used cellphones for longer than that. While some studies suggest that there may be a small increased risk of tumours among the heaviest users, this pattern is not consistent and the researchers caution that the finding may be explained by biases in the way the studies were carried out. (For example, hazy recall of how much a phone was used over ten years ago.)

Laboratory research on cell cultures and animals exposed over their lifetimes does not show that RF radiation affects tumour incidence.

The phone radiates along much of its length. Patches, chips and similar gimmicks do not reduce exposures to RF radiation.

If you do want to reduce exposures, there are simple steps you can take: Use the phone in places with a good signal strength, which allows the phone to transmit at reduced power. Phones using the newer CDMA or 3G (UMTS) technologies usually provide much greater reductions in power. Use a hands-free kit. Minimise the length of time spent on calls. Use a conventional land line phone (ie not cordless), or a car kit with an external antenna