We are exposed to three different types of radiation fields.

• Electric fields
• Magnetic fields
• Electromagnetic fields

Electric Fields

These fields surround every static (constant in time) electrical charge. The unit is V/m or kV/m.

An example for a static electric field is:

• The natural electrical field between the surface of the earth and the ionosphere 0.1-0.5 kV/m; thunderstorms tremendously increase this value

Examples for dynamic electric fields are:

• Home supply power lines
• Wall sockets and connected devices
• Out door electric power lines

Magnetic Fields

Magnetic fields are generated by the movement of an electrical charge. They are wherever an electrical current flows.

The magnetic field decreases with distance to the source. The unit is A/m (Ampere per metre) or T (Tesla= magnetic induction). Commonly used are also mT and µT. A field of 1T already is a very strong magnetic field. 1A/m equals 1.25 µT

An example for a static magnetic field is the magnetic field of the earth with 40-50 µT.

Examples for dynamic magnetic fields are;

• the field of a CTT being stronger than 1T
• Power adapters
• Alarm clocks
• Electric motors
• Outdoor electric power lines
• Transformers of halogen incandescent lamps

Electromagnetic Fields

Periodically undulating (inconstant) electrical fields coexist with periodically undulating (inconstant) magnetic fields. The unit of the strength of the signal is µW/m 2 or mV/m. The number of waves per second is called the frequency. The unit of frequency is called Hz (Hertz) or kHz, MHz, GHz.

Electromagnetic waves travel with the speed of light of approximately 300,000 km/sec. They don’t need a medium for this, meaning that unlike sound waves they can travel through vacuum. The field strength determines the power that can be received from the wave field. Recommendations of safe values therefore orientate at the strength of the signal rather than the frequency.

The most widespread sources of electromagnetic fields are:

• basestations for mobile phones ( GSM and UMTS )
• charge stations of wireless phones according to the DECT standard (24h a day, also when not in use)
• wireless network for your PC
• microwave ovens (when in use)