2.1. International Workshop on the effect and perception thresholds of static and low-frequency magnetic and electric fields and contact currents in humans

Project management: Federal Office for Radiation Protection
Start: 26 October 2017
End: 27 October 2017

Background

The perception of electric and magnetic fields (e.g. those emitted by power lines) is possible under certain circumstances and is often described as unpleasant. For example, low-frequency magnetic fields induce electric currents that lead to irritation of muscles and nerves above the limit values. Under power lines, it is possible for metal objects to become electrically charged. When these are touched, spark discharges and contact currents are triggered. It is unclear when the thresholds of perceptibility and biological effects will be reached in these scenarios. Whether there is an age and sex dependency is also largely unknown.

Objective

The aim of the workshop was to summarise the current state of knowledge on the effect and perception thresholds of fields with internationally recognised experts and to identify scientific knowledge gaps in order to define possible research priorities.

Implementation

Experts from the fields of dosimetry, human biology, and neurobiology participated in the workshop. In total, 12 speakers participated in the workshop.
The five coordinated sessions dealt with the following main topics in 12 presentations:

• Session 1: Magnetic fields
• Session 2: Electric fields
• Session 3: Dosimetry and modelling
• Session 4: Electric currents
• Session 5: Research perspectives

Results

Session 1: Magnetic fields

The stimulation of the peripheral nervous system by low-frequency magnetic fields has been widely researched, and the perception thresholds are well known, especially from research on magnetic resonance imaging. These are far above the set limits and can therefore not be exceeded in the vicinity of power lines. There is currently no need for further studies on humans in this area.
Stimulation of the central nervous system by low-frequency magnetic fields leads, among other things, to visual perceptions (magnetophosphenes), which occur as a result of the stimulation of synapses in the retina. There is evidence of similar effects on synapses in the vestibular organ and in the brain. These already lead to a modulation of the neuronal signals below the threshold values for triggering nerve impulses. The exact thresholds and mechanisms of action have not been sufficiently researched; suggestions for further studies on subjects were therefore discussed.

Session 2: Electric fields

The current state of knowledge is insufficient, especially with regard to the perception of static electric fields that will emanate from the planned DC transmission lines. There is only one older pilot study and one follow-up study on test subjects; the results of this still need to be verified. A pilot study in which the parameters to be investigated are to be precisely defined has been under way at RWTH Aachen University since 2017. This was followed by an extensive study on 200 test subjects. Special consideration is given to the simultaneous effects of static and alternating fields, air ionisation, and humidity as well as the anatomical and physiological characteristics of the test subjects, who vary in age and sex as well as their clothing. The results of the study will form the basis for further research.

Session 3: Dosimetry

Electric and magnetic fields affect the human body from outside and can be measured only outside the body. External fields can lead to fields and currents inside the body (e.g. as a result of induction or influence). These can irritate both the peripheral and central nervous system.
These internal body fields and currents cannot be measured but rather will be calculated in dosimetric models. The models are based on anatomical body models and tissue properties that are as accurate as possible. Particularly accurate models and calculations based on them are helpful in explaining the observed biological effects of fields on the nervous system. It was recommended that these models should be further refined.

Session 4: Electric currents

The irritation of the peripheral nervous system by contact currents has been investigated in some subject studies. A good body of data exists, especially for occupationally exposed persons, most of whom are healthy young men. The results show a high inter-individual variability. The dependence on age and sex in particular is not sufficiently documented. Dosimetric models for the effect of contact currents inside the body should also be further developed.

The irritation of the central nervous system by direct and alternating current is studied mainly for therapeutic purposes in the medical field; in connection with the expansion of power grids, this aspect is of secondary importance.

Session 5: Research perspectives

Important aspects of human biological investigations during exposure to electric or magnetic fields as well as under the application of contact currents were explained. Of particular importance are quality requirements for study design, blinding, statistics, construction of exposure systems, collection of biological data under exposure, interference between exposure, and measuring devices.

The results obtained in the individual sessions will be taken into account in further research projects on the determination of threshold values as well as on dosimetry.

Abstracts of the workshop

The abstracts of the workshop can be downloaded from DORIS, the online repository of the BfS: Action and perception thresholds of static and ELF magnetic and electric fields and contact currents in humans: Workshop Abstracts ; Federal Office for Radiation Protection, Oberschleißheim/Neuherberg, 26. – 27.10.2016