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

Project management: RWTH Aachen University
Start: 1 December 2021
End: 30 November 2023

Background

The importance of electric fields is increasing during the course of power grid expansion, particularly in connection with the expansion of direct current lines. This is because, while there is no limit value for static electric fields, the 26th Ordinance Implementing the Federal Immission Control Act (26^th BImSchV) stipulates that irritation is to be prevented. The perception thresholds must therefore be known. In connection with the expansion of hybrid lines (Ultranet), it is also necessary to know the specific effects of a combination of direct and alternating fields and ion currents.

There are considerable gaps in knowledge regarding the perception of electric fields by humans. This matter is only addressed in two, older scientific publications ^{[1, 2]} as well as a study completed at the end of 2019 by RWTH Aachen University, which yielded unexpectedly low perception thresholds, particularly in the event of a combination of direct and alternating fields ^{[3, 4]}. Ion currents and atmospheric humidity also had a modifying influence. This scenario is relevant to hybrid lines. The results are to be verified, and the mechanisms are to be clarified.

Objective

The research project aims to investigate the perception of hybrid fields by humans and in particular the influence of weak DC background fields (DC = direct current; direct fields) on the perception threshold for AC fields (AC = alternating current; alternating fields). In addition, it will investigate the underlying biological mechanisms of perception. There is some evidence that AC fields cause vibrations in the hair on the arms and legs, whereas DC fields are more likely to be perceived via the head area. As these two modes of perception can interact with one another, the mechanisms are to be investigated both separately and in combination.

Implementation

The existing findings ^{[3, 4]} show that constant, weak AC background fields significantly influence and reduce the DC perception threshold. This project will investigate the influence of constant, weak DC background fields on the AC perception threshold. Forty to fifty particularly sensitive test subjects will be selected from the preliminary study and examined at constant temperature (22 °C) and humidity (50 %) with exposure to constant, weak DC background fields (1, 2, 3 and 4 V/m). The AC field strength will be varied within the range of 1–14 V/m, and the lowest perception threshold will be determined in psychophysiological tests. Some subjects will be sham exposed for control purposes, and the study will be double-blinded – i.e. neither the subjects nor the researchers will know when an electric field is present or not.

In addition, the project will seek to clarify the mechanisms of action that lead to the low perception thresholds. In particular, it will investigate the roles of body hair and atmospheric humidity. To this end, 30 healthy test subjects aged 18–35 will be recruited (15 women and 15 men). In terms of their individual head and body hair, the subjects’ characteristics are to be as different as possible. The air temperature will remain constant at 22 °C, and the humidity will be varied between 30 % and 70 %. Tests will be carried out with AC fields at 8–30 kV/m, DC fields at 14–38 kV/m, and hybrid fields. The physical properties of the hair (moisture content, thickness, length) will be ascertained, and the movements of the hair will be recorded on video. Further investigations will be carried out after the hair has been shaved off. The results will allow conclusions to be drawn regarding the causes of the low thresholds observed for hybrid fields.

References

[1] Blondin JP et al. (1996). Human perception of electric fields and ion currents associated with high-voltage DC transmission lines. Bioelectromagnetics 17: 230 - 241.
[2] Chapman CE et al. (2005). Perception of local DC and AC electric fields in humans. Bioelectromagnetics 26: 357-366.
[3] Jankowiak et al. (2021) Identification of Environmental and Experimental Factors Influencing Human Perception of DC and AC Electric Fields. Bioelectromagnetics 42: 341 - 356
[4] Kursawe et al. (2021) Human detection thresholds of DC, AC, and hybrid electric fields: a double‑blind study. Environ Health 20:92

An experimental study on subjects will clarify the threshold values above which spark discharges and contact currents are perceived and experienced as unpleasant or painful. The study will provide data on individual variability as well as on gender and age dependency.

Under partial or whole-body exposure, test subjects will be examined in order to determine the threshold values above which low-frequency magnetic fields induce electric currents that can influence the central and peripheral nervous system. Subjectively imperceptible influences on brain activity will be measured, and perceptible stimuli will be queried. The threshold values at which neuronal activity in the brain is modulated and the threshold values at which perceptions and sensory impressions arise and are perceived as unpleasant will be determined. Individual variability as well as sex and age dependency will be taken into account. The aim of this project is to check the reliability of the data currently available and to specify the threshold values, which have only been roughly known up to now.

Research contractor: RWTH Aachen University Hospital Institute for Occupational, Social and Environmental Medicine
Project manager: Dr Michael Kursawe
Start: 01.07.2024
End: 31.12.2026
Funding: max. EUR 2,109,769.09

Background

Powerline Source: Michael Rosskothen/stock.adobe.com

The electricity grid in Germany is currently being expanded. This involves the construction of overhead lines for high-voltage direct current (HVDC) transmission, high-voltage alternating current (HVAC) transmission and hybrid lines that combine both transmission technologies in one route (e.g. Ultranet). These types of cables generate static and low-frequency electric fields, and expansion is expected to lead to changes in the population’s exposure to fields of this kind.

In Germany, there are limit values that apply to time-varying electric fields, such as those emitted by overhead high-voltage (HV) transmission lines. These limits are defined in the 26th Ordinance Implementing the Federal Immission Control Act (26th BImSchV). Compliance with the limit values ensures that there are no effects on health. The limits apply to places where people are present on more than just a temporary basis.

No limit value has been stipulated for static electric fields, however, as there is no evidence of relevant adverse effects on health. Nevertheless, static and low-frequency electric fields are perceptible – for example, as a tingling sensation on the surface of the skin. The 26th BImSchV also stipulates that significant nuisance from such fields must be avoided. Accordingly, it is important to know the perception thresholds of these fields.

Previous research findings show significant differences in the perception thresholds between different people (interindividual variance). This includes a study by RWTH Aachen University that was initiated by the BfS and funded by the electricity grids research programme. That study showed that some people taking part in the trials were able to perceive very weak fields. These individuals did not, however, identify themselves as being affected by “electrohypersensitivity” and did not experience any health burdens as a result of these perceptions. The causes of the interindividual variance are still unclear, although there is strong evidence that body hair is a factor.

State of knowledge regarding “electrohypersensitivity” and those affected

Electrohypersensitivity (EHS) is not recognised as a medical diagnosis by the World Health Organization (WHO) and is instead described as “idiopathic environmental intolerance to electromagnetic fields” (IEI-EMF). This refers to a subjectively perceived special sensitivity to low-frequency and high-frequency electromagnetic fields.

Examples of applications that generate electromagnetic fields.

Those affected are also referred to as EHS sufferers and attribute various symptoms – such as headaches, aching limbs and insomnia – to electromagnetic fields. However, the mostly nonspecific symptoms that the sufferers describe cannot be causally attributed to the fact that these individuals are or have been exposed to electromagnetic fields. To date, no biophysical mechanism of action has been identified that could explain the symptoms. Nevertheless, those affected attribute their considerable individual psychological stress to the fields.

People affected by electrosensitivity often claim that they can perceive electromagnetic fields. As yet, these claims have not been investigated with respect to static and low-frequency electric fields. There is also little knowledge regarding the clinical characteristics of this group of people. Moreover, there has so far been no systematic investigation of whether those affected are predominantly prone to certain comorbidities or whether they have socioeconomic factors in common.

Objective

This research project is intended to expand current knowledge of the human perception thresholds of static and low-frequency electric fields to the group of EHS sufferers not previously included in the investigations. At the same time, there is scientific interest in gaining a better knowledge and deeper understanding of the characteristics of those affected by electrosensitivity. This improved understanding of affected individuals would allow those persons to be identified more reliably and addressed in a scientifically sound manner.

Implementation

This research project determines and compares the perception thresholds of static, low-frequency and hybrid electric fields for two groups:

• people who describe themselves as suffering from electrohypersensitivity
• people who do not describe themselves as suffering from electrohypersensitivity (control group).

At the same time, the person’s medical history, comorbidities and relevant socioeconomic data are collected through comprehensive environmental medical diagnostics. The data obtained is analysed with a view to possible correlations with the perception thresholds.