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Radiation protection in electromobility

  • In the case of electric vehicles, electric and magnetic fields arise primarily during operation and charging.
  • The magnetic fields are of particular importance from a radiation protection perspective.
  • In relation to electric vehicles, existing research shows that the magnetic fields depend less on the electric power of the motors than on a vehicle's operating state and technical design (position of the battery, cables, power electronics, etc.).
  • In principle, the Federal Office for Radiation Protection is committed to ensuring that the potential exposure of users is kept to a minimum as part of the development of equipment and, in this case, vehicles.

Electric car; the rear section of the vehicle is transparent. The battery is visible. Electric carElectric car with battery in rear section of vehicle Source: Firstsignal/Getty Images

As with anywhere that electricity is used, electromobility leads to the production of electric and magnetic fields. These fields surround the battery, motor and cables during the operation of electric vehicles. In many cases, the strongest fields are found in the footwells of the front seats. Depending on the construction of the vehicle and the position of the battery, for example, the highest values may also be recorded in the back seat – in other words, where children often sit. Electric and magnetic fields are also produced while the vehicles are being charged.

The term "electric vehicles" is used to refer to purely battery-electric vehicles as well as hybrid electric vehicles. The fields associated with electromobility have frequencies ranging from zero hertz (static fields) to several tens or hundreds of kilohertz (low-frequency fields and fields in what is known as the intermediate frequency range). The magnetic fields are of particular importance from a radiation protection perspective.

With the number of electric vehicles likely to increase in the coming years, the BfS recommends giving due regard to radiation protection aspects in electromobility.

Health effects

On the whole, the health effects of intermediate-frequency fields are not as well-researched as the effects of low or high frequencies. This was the result of a systematic review commissioned by the BfS that investigated not only the possible health effects but also the population’s exposure to intermediate-frequency fields. Apart from electric vehicles, magnetic fields with these frequencies can also be generated by other types of technology.

According to current knowledge, these intermediate-frequency fields do not trigger any health effects, provided that the recommendations of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) are adhered to. There are no legal limit values for electromagnetic fields in motor vehicles in Germany.

In relation to electric vehicles, existing research shows that the magnetic fields depend less on the electric power of the motors than on a vehicle's operating state and technical design (position of the battery, cables, power electronics, etc.).

Electromobility: research into possible sources of electric and magnetic fields

In the case of electric vehicles, electric and magnetic fields arise primarily during operation and charging. A research project commissioned by the BfS investigated magnetic fields in electric vehicles and hybrids.

Where do electric and magnetic fields occur in the vehicle?

Irrespective of their propulsion system, modern vehicles have numerous sources of alternating magnetic fields, including air conditioning systems, fans and heated seats as well as driver assistance, comfort and entertainment systems that use high-frequency electromagnetic fields to transmit information wirelessly by radio. These sources are also present in vehicles with conventional propulsion systems and can give rise to fields of a similar strength to the drive trains of hybrid or electric vehicles.

Research and studies into electromobility

Research project on the operation of electric vehiclesShow / Hide

The research project Determination of the exposure to magnetic fields of alternative drive concepts, final report, in German only) was carried out on behalf of the BfS with the aim of measuring magnetic fields produced by the drive trains in electric vehicles and hybrids. Measurements were taken in vehicles both on chassis dynamometers and while driving on roads in real traffic conditions. The research also looked at different constant driving speeds as well as the effects of accelerating and braking manoeuvres.

The analyses revealed a highly uneven distribution of magnetic fields in the electric vehicles, with the highest values often appearing in the footwells of the front seats. Significantly lower values were measured at other locations, such as in the areas occupied by drivers' and passengers' heads and torsos. This highlights potential for minimisation that manufacturers could utilise in vehicle development.

High field strengths also occur in conventional vehicles

In some cases, the highest values were measured in the back seat, especially when the battery was in an unfavourable position or the wiring was located directly below or behind the back seat bench. However, there were no indications that the recommended maximum exposure levels were exceeded in the analysed vehicles, nor were excess levels observed in a more recent study eby an international group of scientists. Further measurement results are reported on the EMF-Portal.

Comparative measurements in two vehicles with combustion engines found similarly high field strengths in the footwells of the front seats as in the electric vehicles. These fields originated from the motor of a ventilation fan and its wiring. At the highest power level, the measurements exceeded the recommended reference values in one instance.

Research project on the charging of electric vehiclesShow / Hide

The energy storage devices of battery-electric and plug-in hybrid electric vehicles are usually charged with a cable. As is the case whenever an electric current flows, a magnetic field is formed around the conductor. However, the cables can be manufactured so that the field strengths outside the cable are lower.

Another, less widespread, option is wireless charging. Vehicles equipped for this charging method are parked over a coil located on or in the ground – in a garage or parking space, for example. The generated magnetic field induces a current in the vehicle coil, and this current charges the battery. The ground coil generates powerful magnetic fields that far exceed the EU's recommended reference values, but these fields become significantly weaker with increasing distance from the coil.

Compared to those into low- and high-frequency fields, there are relatively few studies into the effects of the intermediate frequency range that are relevant to electric vehicles. As part of the Federal Environment Ministry's departmental research plan, there are therefore plans to launch further projects aimed at investigating the influence that intermediate-frequency magnetic fields generated during inductive charging could have in animal models. The BfS also intends to invite tenders for additional measurements on newer vehicle models and thereby to obtain data relating to other vehicles and exposure during the charging process.

Influence of intermediate-frequency magnetic fields from inductive power transfer during the charging of electric vehicles on the behaviour of laboratory rodents

Project management: Fraunhofer ITEM, Hanover
Start: 1 May 2021
End: 28 February 2025

Background

The wireless charging of electric vehicles is carried out using the frequencies 20 kHz, 85 kHz and 140 kHz, which lie within the intermediate frequency range. So far, this range has been the subject of relatively little research into potential biological and health effects.

The BfS commissioned a literature study in order to determine the current state of knowledge [1]. As well as identifying the currently used technologies that emit intermediate-frequency fields, this included a search of specialist literature on biological effects. Despite an increasing number of corresponding devices, such as induction hobs or wireless charging systems, biological effects are the subject of a relatively small number of studies [2].

Most of these studies focused on reproduction and development, including a number of high-quality studies from Japan that found no negative impacts. Other studies focused on the brain, cognition and behaviour and failed to reach a consistent conclusion. A small number of in vitro studies found no evidence of genotoxic effects. A study of mice at a frequency of 20 kHz found no indications of carcinogenic effects [3]. Another study, of female mice at 20 kHz, found no influence on development or tumour incidence. In the same study, effects suggesting improved agility and alertness were observed in two out of three behavioural tests [4].

Objective

The behavioural tests that revealed effects in the event of exposure to 20 kHz in the aforementioned study [4] are to be repeated at 85 kHz and 140 kHz. In addition, a potential toxicological or carcinogenic effect at these two frequencies is to be investigated.

Implementation

The study will be carried out on mice of the strain C57BL/6J, which is an established mouse model for the investigation of various endpoints. Over a period of 300 days, 80 animals will be permanently exposed to fields with frequencies of 80 kHz and 140 kHz respectively and a magnetic flux density of 200 µT. Two equally sized groups will be sham exposed in parallel. The study will be blinded, i.e. the personnel carrying out the experiments and analysing the results will not be informed of which animals are exposed or sham exposed.

After 200 days, three behavioural tests will be carried out on 20 animals from each exposure group in order to obtain insights into motor behaviour (Rotarod), memory and spatial orientation (eight-arm maze), and exploratory behaviour or anxiety (open field test).

After 300 days, histopathological examinations will be performed on 39 organs from each of the animals and the tumour incidence will be determined in accordance with the OECD Guideline.

References

[1] Hirtl R et al. (2018) Exposition und Wirkungen der elektromagnetischen Felder neuartiger Technologien im Zwischenfrequenzbereich – systematischer Review - Vorhaben 3616S82437
[2] Bodewein et al. (2019). Systematic review on the biological effects of electric, magnetic and electromagnetic fields in the intermediate frequency range (300Hz to 1MHz). Environ Res 171: 247-259.
[3] Nishimura I et al. (2019). Carcinogenicity of intermediate frequency magnetic field in Tg.rasH2 mice. Bioelectromagnetics 40: 160-169.
[4] Lerchl A et al. (2021) Effects of long‐term exposure of intermediate frequency magnetic fields (20 kHz, 360 μT) on the development, pathological findings, and behavior of female mice. Bioelectromagnetics 42: 309-316.

Recommendations

In principle, the Federal Office for Radiation Protection is committed to ensuring that the potential exposure of users is kept to a minimum as part of the development of equipment and, in this case, vehicles. From the outset, the development of new vehicle models should ensure that vehicle occupants are exposed to the lowest possible field strengths.

In the case of wireless charging, the BfS wishes to emphasise that the ground coil in particular can generate strong magnetic fields, but that these quickly become weaker with increasing distance from the coil. Precautions must therefore be taken to ensure that the area between the coils remains clear and that only low field strengths occur in locations where people might be present.

People with active physical aids (pacemakers, neurostimulators, etc.) should also ask the doctor who is treating them whether magnetic fields can affect the operation of the medical product they are using.

State of 2023.11.14

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