Mobile devices use low-power radio waves
Mobile phones and devices use low-power radio waves, or radio frequency electromagnetic fields, to exchange information with the mobile network.
There are safety limits for human exposure to radio waves specified by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) based on recommendations from the World Health Organization (WHO). The limits take into account a wide margin of safety in order to protect people from all known health effects caused by exposure to radio waves. The radio wave exposure limits that apply to mobile phones are expressed in SAR (Specific Absorption Rate) levels. SAR is a measure of the rate of radio energy absorption in body tissue.
There are no safety reasons to compare SAR values of different phones
Mobile phones and devices must be designed to meet the exposure limits and undergo SAR testing before they are released on the market. SAR information, including the maximum SAR value, is included in the packaging of the phone. There are slight differences in SAR levels depending on the model of the phone, but below the SAR limit there is no difference in safety, and thus, no reason to compare the SAR values of various phone models.
The SAR value that is provided with new mobile phones is the highest value obtained during extensive testing of that phone model. The SAR value in normal use will be significantly lower due to several reasons.
The phone is constantly varying its output power, keeping it at the lowest level needed for the radio waves to reach the nearest base station. The phone is further reducing the transmitted power when the user is listening and not talking. This is not taken into account during SAR testing, which is always performed at the maximum power level of the phone. Furthermore, SAR varies depending on which frequency band the phone is using and the provided SAR value corresponds to the frequency band giving maximum SAR.
The difference between the provided maximum SAR value and the real-life SAR value of one phone model is much larger than the small variations in maximum SAR of different phone models. Typical, real-life SAR values can be as low as a few percent of the provided maximum SAR value.
Hands-free equipment is recommended for convenience
Hands-free devices or headsets are designed for convenient, hands-free operation of the phone and not for safety reasons. Nevertheless, using a hands-free device can reduce radio-wave exposure to the mobile phone user’s head, and the WHO recommends that people use them if they want to reduce their exposure.
Mobile phones users should obey local restrictions for use
Radio waves have a potential to cause disturbances (electromagnetic interference) in sensitive electronic devices. The immunity to such interference of cardiac pacemakers, hearing aids and other medical equipment has increased immensely in recent years. Nevertheless, mobile phone users should always obey restrictions that may exist in locations such as hospitals and aircraft, or which are recommended by their physician.