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Elektromagnetische Felder

Proven effects on health caused by the fields around power supplies

Alternating current with a frequency of 50 Hertz (Hz) flows in the German electricity network. Arising from this are so-called low frequency electric and magnetic fields that together with the alternating current in the power lines change their direction 100 times per second. These are known as low frequency alternating fields.

Effect of alternating magnetic fields Effect of alternating magnetic fieldsEffect of alternating magnetic fields on people: they generate more or less pronounced eddy currents

Natural electrical fields in the body

In all living creatures, therefore also in humans, there are many electrically charged particles. Their movement causes electric fields and currents. In many metabolic processes, electrically charged particles are displaced and nerves carry their signals in the form of electric pulses. The heart is also electrically active.

These endogenous processes can be measured by medical doctors for example using an electrocardiogram (ECG) or an electroencephalogram (EEG).

Effects of low frequency fields

Low frequency fields generate additional electric fields and currents in the human body. As a consequence nerve and muscle cells can be stimulated. However, for this to happen, certain frequency-specific effect thresholds must be exceeded. For example, electric field strengths of 4-6 volts per metre (V/m) are required to stimulate nerve fibres in the skin or muscles.

The lowest proven effective threshold relates to the triggering of so-called "phosphenes". These are perceptions of light that arise because of the stimulation of sensitive cells in the retina. Although phosphenes have no negative effect on health, they are however considered to be a particularly sensitive model of the stimulation of electrically excitable cells.

The higher the field strengths in the body, the more dangerous these can be. If neuronal signal conduction in the body becomes muddled, there is a threat for example of cardiac arrhythmia.

Protection from health risks

Pacemaker PacemakerPacemaker

As the thresholds for proven effects are known, recommendations can be made on this basis to limit low frequency fields. The International Commission on Non-Ionising Radiation Protection (ICNIRP) recommends for frequencies of 50 Hertz that the electric field strengths generated in the brain and retina should remain under 20 millivolts per metre (0.02 V/m).

The limit values for stationary plants set out in the 26th German Federal Immission Protection Ordinance (26. BImSchV) are also based on this recommendation. The limit values for the immissions affecting the body from the outside protect against the proven health-related effects of low frequency electric and magnetic fields.

Static electric and magnetic fields

No health risks have been demonstrated for static electric fields occurring in usual exposure situations that arise from direct current power lines. The static magnetic fields arising from direct current power lines are also harmless in usual exposure situations.

The amendment to the 26th BImSchV made in August 2013 sets legal requirements for direct current plants in Germany. The limit value of 500 microtesla (0.5 millitesla) was selected so as to rule out interference effects on cardiac pacemakers from static magnetic fields.

In the medical sector, strong static magnetic fields of several tesla (i.e. several thousand millitesla) are used for imaging processes. In this sector, acute effects such as dizziness and nausea can occur both in patients and also in medical staff.

By the way, the effects of low frequency fields differ greatly from those of high frequency fields. The latter are found for example around mobile communications.

State of 2017.07.05

© Bundesamt für Strahlenschutz