The cellular phone has to emit radio frequency energy at levels high enough to reach base stations (antenna towers) tens of kilometers away. Since the energy is emitted as a microwave in the direct vicinity of theusers head there are concerns about the safety of this technology.
There are reports from cell studies as well as animal studies that is most worrying. Among other effects the double DNA breakage is among thefundamental och disturbing findings. This may indicate that there may bea significant risk of developing cancer tumours, foremost brain tumoursin the user of cellular (mobile) phones.
The design of the cellular phones casing, electronic and foremost the antenna construction gives widely different near and far fields around the phone.
It is at present time not completely clear what parameters of the field gives biological effects, however as an intermediate cautionary step one can use the simple measure of absorbed radiated energy into the tissue of the head.
This is given as a SAR - Specific Absorption Ratio and is measured in watts per kilogram. This may not be a true measure of the biological hazard from the phone but may be used as an indication of the energy recieved into the head.
See it as prudent avoidance. Niels Kuster, a radiation expert at the Swiss Federal Institute of Technology, has developed a new measurement technique to measurecell-phone EMR towards the user's head. He recently measured 16 popular cell phone models, and published the results in the Swiss Consumer Report magazine.
The table below is an excerpt from his study some years back:
SAR is given as Cenelec value for average EMR exposure of user's head, measured in Watt per kg of user's body weight. (A low number means less radiated energy into the users head).