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Berlin Environmental Atlas

08.05 Electromagnetic fields

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Biological Effects

"Electrosmog" is the buzzword which has directed public awareness towards technical field emissions in recent years. All over the world, numerous studies have been carried out on the possible effects of electromagnetic fields on humans, animals, plants and cell or tissue cultures, and a series of large-scale epidemiological surveys has also been conducted. The effects of electromagnetic fields generally depend on the frequency and intensity, but also on individual characteristics such as body size or angle towards the field.

Findings have been largely substantiated with regard to the effects of induced eddy currents at higher and medium-range field strengths (cf. Fig. 5), and these have formed the basis for the limit values in protective legislation.

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Fig. 5: Schematic Distribution of Eddy Currents Induced by Magnetic Fields of Longitudinal and Transversal Orientation Towards the Body (SSK 1990)

An external magnetic field induces eddy currents in the human body on a circular plane perpendicular to the direction of the field. Similarly, an electric field creates a flow in the body which follows the same direction as the field: under high overhead voltage lines, for example, the flow would be from head to foot - and vice-versa (alternating field!). These field-induced flows are recognised as the predominant cause of biological effects at low-frequency fields. Above certain trigger values, the induction flows, just like direct body current, cause effects which can damage the organism.

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Tab. 1: Biological Effects of Different Current Densities at 50 Hz (cf. Bernhardt 1990)

Excel
[Table is also available as Excel-File (MS-Excel is required).]

Although sensitive people can already detect electrical fields at 1kV/m, be it from the vibrations of body hair or due to discharge from conducting objects near the human body, there is no known danger to health, even when exposed for long periods of time. Indirect effects on electronic implants, e.g. rarely used types of single-pole artificial pacemaker, can occur from a field strength of around 2.5 kV/m or 20 µT, but life-threatening results are very unlikely. However, uncomfortable stutter rhythms can occur, which is why those affected people should stay away from strong fields (BfS 1994).

The scientific literature yields numerous epidemiological studies which address possible links between exposure to fields and the risk of cancer among certain sections of the population. So far, despite sometimes considerable effort, the results have been contradictory. Direct comparisons are rendered more difficult by varying circumstances. There is a shared emphasis, however, on the need for more research into both the epidemiology and the mechanisms at play.

Limit and Recommended Values

The observed effects have been used by various national and international bodies to establish limit or recommended values for different frequencies and areas of exposure. In addition to limits on direct field impact (V/m, A/m) at the workplace and among the general population, there are also maximum limits for indirect field impacts, pacemakers, small transmitters, partial body exposure, exposure of short duration, pulsed radiation, etc.

Due to the different safety strategies which have been conceived for different sections of the population, it is difficult to compare the various limit and recommended values.

The International Committee on Non-Ionising Radiation Protection (ICNIRP, formerly INIRC) of the International Radiation Protection Association (IRPA) has defined a maximum admissible body current density of 10 mA/m² (INIRC/IRPA 1990) which takes its lead from the body's own physiological current densities. Acute danger to health from the disruption of nervous, muscular and cardiac functions only occurs at 10 - 100 times this amount (cf. Tab.1).

To protect the population at large, ICNIRP/IRPA recommends a further reduction by a factor of five, resulting in a body current density of 2 mA/m².

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