cell phones response

[John Campbell]

Martin Gledhill has responded to Bev's question re cell phones.
He apologised for the delay as he was in the Chatham Islands when the question
was passed to him.
John Campbell

Bev Pantry of Carmel College asked:- 
My Y13 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 

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