How strong are the electromagnetic fields of mobile phone base stations?

In order to protect the public’s health from the effects of electromagnetic fields, German legislation has prescribed protection limits for base stations. These limits are based on recommendations by national and international expert committees and have been embodied in the 26th Ordinance Implementing the Federal Immission Control Act (Ordinance on electromagnetic fields – Verordnung über elektromagnetische Felder zum Bundes-Immissionsschutzgesetz – 26 BImSchV). The operation of mobile phone base stations in Germany is thus subject to one specific law that is based on scientific findings. Compliance with these limits is a prerequisite for obtaining a site certificate from the independent Federal Network Agency for Electricity, Gas, Telecommunications, Post and Railway (Bundesnetzagentur). This certificate, in turn, is a legal requirement for the operation of a mobile phone base station by a network operator. The safe distance specified in the site certificate states how far from the station the fields will remain below the protection limits defined by 26 BImSchV. The Federal Network Agency will only allow the operation of a base station providing that no-one lives or works or has any other reason to remain permanently within this safe distance.

The basis for the calculation of the safe distance is the maximum possible transmission power of the antenna. Electromagnetic fields created by adjacent stations will also be taken into account. Today’s mobile phone base stations use an average power of 10 - 50 watts per channel and antenna.

In Germany, several frequency ranges are used for mobile communications. Because of their physical properties, different limits have been established for each of them. There are two limits for GSM networks: 42 V/m for 900 megahertz transmitters and 58 V/m for 1800 megahertz transmitters. The limit for UMTS is 61 V/m and for the new LTE stations the limits are 38.7 V/m for 800 megahertz transmitters and 61 V/m for 2600 megahertz transmitters.  

The transmission power of base stations in practice

In day-to-day operation, several factors influence the propagation and strength of electromagnetic fields. Mobile phone base stations often do not transmit with maximum power as this can affect other base stations. Instead, they will automatically reduce their power to the lowest level that is required. In GSM networks, for instance, a base station with 10 watts power per channel will only transmit at an average of 4 to 6 watts on each channel. UMTS and LTE mobile phone standards also have automatic power control that reduces transmission power when required.

Thus, mobile phone base stations only create electromagnetic fields that reach a fraction of the permissible limits. In areas where people are present, fields will remain a hundred times or more below the prescribed limit. Certain materials such as walls will also dampen electromagnetic fields. For instance, a concrete wall that is 20 cm thick will reduce the field strength by about 90 percent.  

Typical values of mobile phone fields

New base stations for the UMTS networks have increased existing electromagnetic fields around mobile phone base stations in many places. However, independent institutions have measured the field strength and found that total strength has only increased slightly as UMTS operates with a very low transmission power; it also reduces its fields more than GSM. The Federal Network Agency always assesses the overall situation at a location and only issues site certificates on this basis. This means that legal limits will always apply, including in locations where UMTS installations already exist or are being planned.

An online simulation of the IZMF Information Centre for Mobile Communications illustrates typical mobile phone field values at base stations. This internet application is easy to use and gives an impression of the strength of the electromagnetic fields around mobile phone base stations.

Information such as the height of the buildings, the power of the base station and the distance between the antennas and neighbouring houses can be entered into the online form. The programme will then calculate the strength of the electromagnetic fields at any point in the vicinity of the station and how close they come to the legal limit as defined by 26 BImSchV.  

Public site database of the Federal Network Agency

Since 2004, the Federal Network Agency has been publishing an online database of the electromagnetic fields at mobile phone base stations. This allows interested users to enter their postcode and street address; they will then obtain information about electromagnetic fields at base stations in their area.  The database was launched with the support of mobile network operators and contains information on fixed radio and mobile network installations. The database also contains up-to-date information about all the locations where measurements have been carried out to ensure that the strength of the electromagnetic fields remains below the legal limits. As well as providing information on the measurements that have been undertaken, the database also displays them graphically in relation to the legal limits. In general, the measured values lie many times below these limits.