How dangerous is the radiation in electric cars?

Roland S. doesn't sound like someone who tends to exaggerate or gets into something unnecessarily. But when the real estate agent complains that he feels uncomfortable in his Mercedes EQS on longer journeys, that his legs tingle and that he attributes this to electromagnetic radiation in the electric car, then it sounds quite credible.

The man knows his way around radiation. Years ago, he worked for a company that produced crystals for the semiconductor industry. This requires extremely strong magnetic fields. The businessman has respect for them, as they can have an impact on the human body.

"It's tingling in the legs"

This is also confirmed by the Federal Office for Radiation Protection (BfS). "In the medical field, strong static magnetic fields of several tesla (i.e. several thousand millitesla) are used for imaging procedures. In this area, acute effects, such as dizziness or nausea, can occur for patients, but also for medical staff." The BfS further writes: "No health hazards have been proven for static electric fields emanating from direct current lines, as they occur in normal exposure situations. The static magnetic fields emitted by direct current lines are also harmless in normal exposure situations." In contrast to X-rays and gamma radiation, however, the energy of electromagnetic fields is not sufficient to damage the genetic material and cause cancer.

But does this also apply in the car? How strong are the magnetic fields there? And are electric cars different from combustion engines?

"We take the issue very seriously"

A conversation with Martin Reuter helps. The doctor of electrical engineering is responsible for the electromagnetic compatibility (EMC) of electric drives at Mercedes-Benz. Or to put it another way: Among other things, he must ensure that no harmful radiation is produced in the electric car.

"We take the issue very seriously and look at it from the development of a vehicle to its release," says Reuter. The recommendations of the BfS, which in turn refer to the WHO, serve as a basis. The World Health Organization evaluates all medical research and publishes limit values as recommendations via the International Commission on Non-Ionizing Radiation Protection (ICNIRP) – for radiation exposure from mobile phones or cell towers, but also in electric cars. In the EU, these are currently 5 kilovolts per metre (5 kV/m) for electric fields and 100 microtesla (100 μT) for magnetic fields.

Limit values are only a recommendation

However, since the WHO is not a government organization, these values have no legislative function. Manufacturers can, but do not have to, adopt them. For Reuter, there is no question: "Mercedes naturally adheres to these limits," says Reuter. "Especially in order to be able to refute fears like those of the EQS driver."

Reuters' team investigates EMC in its own test building in Sindelfingen. The manufacturer invested 50 million euros here in 2019 to test antenna systems and the up to 250 electronic components installed in a car. In the S-Class, for example, more than five kilometres of cable have been laid. "For example, we make sure that the radio doesn't hum when the electric motor is running." For this reason, the engineers must carefully insulate all cables and electrical components and shield them from each other. "In principle, however, e-cars and combustion engines differ very little. Both have the same critical sources of magnetic fields such as seat heating, air conditioning, assistance systems or loudspeakers."

In electric cars, electric units such as batteries, motors or on-board chargers are added. But studies show that the magnetic fields depend less on the electrical power of the electric motors than on the position of the battery, the cables and the power electronics.

In 2009, Seibersdorf Labor GmbH from Austria even carried out road tests on behalf of the BfS with hybrid and electric cars available at the time, such as the Toyota Prius, the all-electric Fiat Panda Electric and the Mercedes transporter Atego BlueTec Hybrid, in order to "determine the exposure to magnetic fields of alternative drive concepts". The radiation levels in the vehicles were measured both on chassis dynamometers and in road traffic under real traffic conditions. Different constant driving speeds and the effects of acceleration and braking manoeuvres were also taken into account.

Increased values during braking and acceleration

The result: In the case of hybrid cars, the locally occurring maximum immissions were between 29 and 34 percent below the ICNIRP reference value for the general population, while in the all-electric Fiat Panda it was still three percent. "These maximum values," says the researchers' final report, "occur in most cases in a very localized manner, typically in the foot and lower leg area at the driver's and passenger's seats. In some cases, when the battery or the wiring is located unfavourably directly under or behind the rear seat, immission values of up to a maximum of 34 percent of the reference value were also measured in the abdominal area on the rear seat (depending on the vehicle)." Especially when braking and accelerating the vehicle.

In other places, for example in the head or torso area of drivers and passengers, the measured values were significantly lower. "This opens up minimization potential," the BfS concluded at the time, "which manufacturers can use in vehicle development."

A question of shielding

And they do, as Mercedes engineer Reuter assures. In order to reduce radiation exposure, Mercedes therefore lays cables and electrical components as far as possible in the underbody or engine compartment, i.e. separated from the cabin by a metal layer. In addition, the field energy decreases disproportionately with increasing distance. In free space, the magnetic field is only a quarter as strong at twice the distance. Insulation or shielding can even reduce it to a tenth. "Even a few millimeters more distance between cables or wires can make a big difference here," says electrical engineer Reuter.

Incidentally, that study from Austria also examined the exposure to electrical radiation in two vehicles with combustion engines, a VW Passat and an Audi A4. The result: The engineers determined a similarly strong radiation in the front footwell as in an electric car. Responsible for this was the motor of a ventilation fan and its wiring. At the highest power level, the measured values were even above the recommended reference values in one case. But here, too, the magnetic field measurements did not provide any indication of a potential hazard. Not even for wearers of pacemakers, for example.

And since 2009, the automotive industry has continued to improve the design of vehicles with hybrid and electric drives. In today's electric motors, for example, an aluminum die-cast housing prevents electromagnetic radiation from escaping. In addition, filters are used to reduce electromagnetic radiation at the interfaces to the outside. To protect the occupants, but also to prevent disruptions in the interaction of the electronic systems.

Unexplained "phenomena"

Mercedes customer Roland R. is not reassured by all this. He travels a lot in his EQS – both professionally and privately. After 1.5 years, there are already over 60,000 kilometers on the speedometer of his luxury electric car. On long journeys, he also likes to make himself comfortable in the back seat and let his wife chauffeur him. "Then," he complains, "it tingles even faster than in front. Maybe because I'm sitting directly above the rear engine?" Even if the electric Mercedes draws up to 200 kW direct current at the fast-charging station, the driver says he feels it physically.

Although there is no direct physical connection, physicist Reuter does not simply dismiss such observations from customers. Scientific studies would confirm such "phenomena". The fear of creeping poisoning, for example from exhaust fumes from a factory or the vicinity of a nuclear power plant, can cause people stomach aches or make them feel uncomfortable: Everyone is sensitized differently.