What is the SAR value for mobile phones and base stations?

High-frequency electromagnetic fields penetrate the human body at a depth of a few millimetres to a few centimetres. The body tissue absorbs their energy and transforms it into heat. This is called the thermal effect.

The amount of energy that is absorbed by the body is measured by the specific absorption rate, SAR in short, in watts per kilogram body tissue (Watt/kg).

Mobile phones and mobile phone base stations send out electromagnetic fields in alternation. These fields carry the radio signals that transmit information from the sender to the receiver; distances may cover several kilometres. Electromagnetic fields from base stations that people are exposed to are generally much weaker than fields created by mobile phones held to the ear when making a call.

Legal limits regulate the strength of electromagnetic fields created by mobile phones and base stations. They guarantee that fields are not a health risk. Agreed at an international level, these limits take into consideration scientifically proven effects on health, both thermal and non-thermal.

The SAR limit for fields created by mobile phone base stations is 0.08 watt/kg for the general public. This value is averaged for the whole body. It guarantees that the maximum possible rise in body temperature near mobile phone base stations remains below 0.02 °C. A different limit for electromagnetic fields created near the head by mobile phone use applies for parts of the body: 2 Watt/kg, averaged for 10 grams of body tissue. This limit ensures that the local rise in temperature occurring in parts of the body when using a mobile phone remains below 0.1 °C. The partial body limit assumes the theoretically possible maximum: A user could talk on a mobile phone for 24 hours a day and seven days a week without being exposed to any health risks.

SAR values in everyday life

In practice, the strength of electromagnetic fields remains considerably below the legal SAR limits. Both mobile phones and base stations automatically reduce their transmission power to the lowest possible value that still allows good reception. This also lessens the field’s SAR value.

SAR values for mobile phones always refer to the maximum possible transmission power. However, these will only be reached under unfavourable transmission conditions. Field strength weakens as the distance between the mobile phone and the base station is reduced.

SAR values do not take into consideration the specific transmission properties of each mobile phone. This is because the average or actual transmission power is important for the electromagnetic fields, and not the possible maximum. Mobile phones create varying electromagnetic fields owing to differences in their design and construction, as well as their electronics and antenna.