Can we be shocked by direct current?
Dangerous electricity? Power lines and health
It crackles here - electric fields under high-voltage lines
The German power grid is around 1.8 million kilometers long. Almost three quarters of the cables run underground. Only about a quarter of the cables hang clearly visible from high masts. These are mostly high and extra high voltage lines with 110, 220 or even 380 kilovolts. The alternating current flowing in the process generates low-frequency fields.
Anja Lutz from the Federal Office for Radiation Protection describes how you can perceive this: When you walk under a high-voltage power line, you can sometimes hear it crackling - the charge in the air directly on the lines is responsible for this. Lutz also explains another phenomenon: If you are under a power line with a strong electric field, the following can happen: The hairs stand up because the electrically charged molecules on the surface of the skin align themselves with the electric field of the power line.
Electromagnetic fields as a health hazard?
In addition to the electric field, which can easily be shielded by trees or house walls, there is the magnetic field: It is created by the flowing current and affects the human body. Electromagnetic fields arise not only under power lines, but also from cell phones, WLAN or microwaves, for example. The harmlessness of these fields for humans has not yet been proven. Rather, some studies have caused unrest. The best known is the study by the elite University of Oxford: researchers analyzed the data from the national cancer registry from 1962 to 1995 and established a connection between leukemia in children and the proximity of the mother's home to a high-voltage power line at the time of birth.
So far no clear research results
The radiation protection expert Anja Lutz rates the studies as follows: "The crux of all these studies is always that they are so-called epidemiological studies. This means that the actual magnetic field exposure has been linked to the risk of leukemia and examined whether the risk of leukemia is also increased with increased exposure. These are indications that are to be taken very seriously. Such studies can never be taken as proof, because they cannot prove that the connection found is actually a cause-and-effect relationship. "
The Oxford study was repeated and carried out in a larger area with much more data. The connection between high voltage and cancer could no longer be found. So it could be that the first study only came to its result because the sample was too small. Lutz also notes that the biological mechanisms that explain how magnetic fields could lead to leukemia have not yet been found.
No more harmful than laser printer or coffee
Even in animal experiments, researchers have not yet succeeded in showing how electromagnetic fields can damage the organism. So there is no evidence that power lines are harmful or that they are not harmful. Since there are no clear results, the World Health Organization (WHO) has therefore classified low-frequency electromagnetic fields - on a par with laser printers and coffee - as 'possibly carcinogenic'. The special thing about electromagnetic fields, however, is that the field decreases as the square of the distance. As a result, ten times the distance from the line means only one hundredth of the field. A distance of 400 meters between the lines and residential buildings is considered safe protection.
Is there a difference between AC and DC?
Many of the new lines that will be built across Germany in the next few years do not carry alternating current at all - but direct current. According to Anja Lutz, however, this has completely different properties: She explains that a direct current line generates so-called static fields, which can be compared to the magnetic field of a magnet. No negative health effects are known to exist in direct magnetic fields. If these power lines are buried instead of hung up, the field changes again. It is higher directly above the underground cable than directly under an overhead line of the same strength. On the other hand, it is much narrower than under the suspended cables. Researchers assume that this is the least harmful to health.
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