Protect magnets from EMF
Electromagnetic fields in the living environment
Electromagnetic fields in the environment
Natural and engineered EMFs occur in nature and in the man-made environment. In addition to the earth's magnetic field as an example of a naturally present field, many other fields are created through technical processes. Like light, they belong to the electromagnetic waves (Fig. 1). Their properties and possible effects on humans differ depending on their strength and frequency. The frequency is given in the unit Hertz (Hz). In the non-ionizing range of the electromagnetic spectrum, a distinction is made between static fields (0 Hz), low-frequency fields (up to approx. 1 kHz) and the range of intermediate-frequency and high-frequency fields (up to 300 GHz). According to the WHO, the intermediate frequency range is between 300 Hz and 10 MHz (WHO 2005a), but is not always defined in the same way. In the case of static and low-frequency fields, the electric and magnetic fields are considered separately. If the frequency is higher, these fields are viewed together as an electromagnetic field, but here too there are electrical and magnetic field components that are closely linked.
Static fields that occur in the living environment, for example with permanent magnets or batteries, can exert force effects on electrically charged molecules in the body or lead to an electrical charge on the body surface. In the household, low-frequency fields emanate from electrical appliances of all kinds and from power lines and typically have a mains frequency of 50 Hz in Europe. The low-frequency fields create induced electrical fields and currents within the biological tissue. This can stimulate excitable body cells such as sensory receptors, nerve and muscle cells. Intermediate frequency fields arise, for example, on induction stoves, energy-saving lamps or wireless charging stations that we know from electric toothbrushes, among other things. The irritating effect in the lower intermediate frequency range due to induced electrical fields and currents changes more and more into a warming effect on the tissue at higher frequencies. Mobile radio networks (e.g. mobile radio, WLAN, Bluetooth, cordless telephones), radio, television and microwave ovens work with high-frequency fields in the living environment. These fields can generate heat through their energy input in the tissue of the body.
Limit values protect us from excessive exposure to EMF. However, these are not regulated uniformly internationally. They are presented by various international commissions, e.g. B. the International Commission on Non-Ionizing Radiation Protection (ICNIRP), and recommended to the responsible state authorities for national implementation in legal regulations. The recommendations of the commissions are based on the regular evaluation of the current state of knowledge of science in the field of EMF and their possible effects on humans and the environment. When it comes to legislation, the states act autonomously. However, they are largely based on the recommendations of the expert commissions and, in the case of European countries, also on the corresponding EMF guidelines and recommendations of the European Union (EU). In Europe they orientate themselves z. B. on the recommendations of the ICNIRP. Basically be in it Basic restrictions for human exposure to EMF and Reference values
The limit values for EMF are not standardized internationally
differentiated for the limits of emissions from devices or systems. Basic limit values are based on the scientifically proven biological effects of electrical, magnetic and electromagnetic fields and are around 50 times below the proven thresholds. This means that particularly sensitive population groups, such as B. Children, the elderly and the sick are protected with a sufficient safety reserve. Reference values are limit values which, in contrast to the basic limit values, can be measured directly and thus enable compliance with the basic limit values to be checked. In the case of predominantly local exposure, e.g. For example, if a mobile phone is held to the ear, the use of the reference values is not suitable. Compliance with the local basic restrictions must then be assessed directly using computer simulations, for example.
In Germany and Europe there are different legal regulations for the protection of the general population and for occupational safety, all of which are based on the recommendations of the ICNIRP. In Europe, these are the EU Council Recommendation 1999/519 / EC for the protection of the general population and the EU Directive 2013/35 / EU for occupational safety. In Germany, the Ordinance on Electromagnetic Fields (26th BImSchV 2013) stipulates binding limit values for EMF that are generated by fixed systems such as B. cellular base stations, radio transmitters and high-voltage lines must generally be complied with and therefore also apply in the residential area. These limit values correspond to the ICNIRP reference values mentioned above. For non-stationary devices with radio applications (e.g. mobile phones, WLAN routers), domestic electrical installations and electrical household appliances (e.g. hair dryers, washing machines), which are often used in residential areas, there are regulations on device and product safety that are harmonized across Europe via standards and compliance with these must be indicated on the device by means of a CE mark when it is placed on the market. In the harmonized European standards, the protection goals were set on the basis of the basic limit values and reference values of the ICNIRP.Table 1 shows, based on the ICNIRP recommendations, a brief compilation of reference values and basic restrictions that are particularly interesting for the residential environment. Depending on the frequency, the limit values are defined by various physical quantities.
Sources of electromagnetic fields in the living environment
In the course of advancing mechanization, EMFs from a variety of different field sources occur in our living environment. The fields are either generated by electrical installations, devices or permanent magnets in your own living environment or emitted from electrical systems located outside. Low-frequency magnetic fields and high-frequency electromagnetic fields penetrate walls and other materials and can therefore easily get into the interior from the outside. They can also penetrate the body tissue and basically cause effects there. Low-frequency electric fields, on the other hand, are largely shielded by walls, vegetation or other material. They can therefore only affect people outdoors with a direct view of the field source or indoors near electrical installations or devices. They also penetrate the body less well and act mainly on the body surface.
According to their purpose, the type of their power supply (batteries, mains current) and their electrical properties, installations and devices can be distinguished in the living environment that generate static fields, low-frequency alternating fields, intermediate frequency fields or high frequency fields. In any case, the strength of the fields decreases significantly with the distance from the field source. This means that the fields are always strongest when there is direct body contact with a field-generating device or in its immediate vicinity. How much people are exposed to fields depends on the respective field strengths emitted by the devices or systems and their distance. There is almost always simultaneous exposure to several fields with different frequencies and strengths from different field sources. Detecting the total exposure of a person at a certain location therefore requires complex measurements or - with precise knowledge of the various field sources and their strengths and distances to people - extensive computer simulations.
Significant static magnetic fields in the living environment are based on the one hand from strong permanent magnets, e.g. B. of magnetic toys, jewelry or holders and of the magnetic cores in speakers, headphones and device transformers. On the other hand, DC batteries such. B. Batteries for small appliances and car batteries, static electric fields between their poles. When electricity is drawn, static magnetic fields are also created. The magnetic fields of the permanent magnets mentioned are sometimes so strong (over 500 µT) at distances of less than 10 cm that electronic implants (e.g. pacemakers) can be disturbed (BAG 2016a). The strength range for a possible direct biological effect (dizziness, metallic taste in the mouth and light phenomena on the retina from 2 T; ICNIRP 2009) is not reached by such magnets. The static magnetic fields of photovoltaic systems in houses take on values at a distance of 30–50 cm that correspond to the natural earth's magnetic field. In Germany this has a magnetic flux density of approx. 45 µT. Static electric and magnetic fields from high-voltage direct current transmission lines (HVDC lines) can reach the living area from outside, provided there is a line nearby. The HVDC line expansion is currently being planned and set up in Germany on a larger scale. The strength of the magnetic fields generated by HVDC lines in their vicinity is at most in the strength range of the natural earth's magnetic field.
Low frequency fields
Low-frequency fields, especially the 50 Hz magnetic fields worth mentioning here, originate in living areas from power cables laid in walls or exposed, as well as from electrical devices that are operated with mains electricity. These are almost all electrical household appliances and lights, whereby fields of the intermediate frequency range also arise in the increasingly common electronically controlled household appliances. Magnetic fields only arise in electrical conductors and devices when a current flows in the cables, i.e. when the devices are switched on. Electric fields, on the other hand, are always present as soon as a conductor or device is live, i.e. also on devices, lamps and their power cables that are switched off when they are connected to the mains. In contrast to magnetic fields, however, the electrical fields are strongly attenuated by conductive material (such as masonry, shielding cable sheathing or the metallic housing of devices).
The strongest magnetic fields are generated by electrical devices with powerful motors, transformers (power supply units), magnetic coils or with a strong heating power. Humans are exposed to the highest fields when such devices are also operated close to the body (e.g. hair dryers, razors, drills, electric blankets).Table 2 shows typical magnetic flux densities of some household appliances at different distances.
It can be seen that all magnetic fields generated by household appliances decrease rapidly with distance; the field strength is reduced by at least half when the distance is doubled. Magnetic field mats, which are offered for private use for therapeutic purposes, but also as recreational and wellness devices, sometimes generate strong magnetic fields that are above the international recommended limit values (BAG 2016b).
External, low-frequency magnetic fields affecting the living environment can primarily come from the 50 Hz high-voltage overhead lines mentioned above, as well as from AC underground cables, traction power lines and transformer stations if these are located close to the home. In such systems, the legal limit values of the 26th BImSchV must be observed. Measurements in various European countries, including Germany, showed that the values in indoor areas are almost always below 1 µT, i.e. H. more than a hundred times below the German limit value (EFHRAN 2011).
Intermediate frequency fields
Fields in the intermediate frequency range arise in the living environment, for example when operating induction hobs, energy-saving lamps, wireless charging stations, screens and other electronically controlled electrical devices and lights. In addition, the inverters of photovoltaic systems in the house generate noticeably strong intermediate frequency fields in the kHz range in addition to low static and low-frequency fields. A comprehensive recent study in 121 rooms of 42 apartments in Belgium, Slovenia and Great Britain found that power tools, energy-saving lamps, vacuum cleaners, microwave ovens with inverter technology, dimmers and washing machines are among the most common sources of intermediate frequency fields (Aerts et al. 2017) . A total of 279 devices from 65 device categories were measured. The strongest electric and magnetic fields were measured in induction cookers, LCD screens, microwave ovens and refrigerators with inverter technology as well as in energy-saving and fluorescent lamps. Induction cookers must generally be viewed as the strongest source of intermediate frequency fields in the household (Aerts et al. 2017). If the body is not far from the stove (1–20 cm) and under unfavorable conditions (unsuitable and / or off-center cookware), the limit values can be reached in some cases or even exceeded with some devices (BAG 2016c).
In the case of inverters in photovoltaic systems, in view of the intermediate frequency fields generated by them, it is recommended that this part of the system not be installed in the immediate vicinity of permanent residence areas (LUBW / LfU 2010).
High frequency fields
High-frequency fields are created in the living environment by the transmitters of various radio applications and as leakage radiation from microwave ovens. A number of small transmitters are operated in the house and apartment: mobile phones, DECT cordless phones and base stations, WLAN routers and clients (e.g. notebooks, tablet PCs), Bluetooth devices (headsets, wireless computer peripherals, etc.), other wireless devices (e.g. baby monitors) and other wireless device connections (wireless headphones, speakers, video connections, etc.). Of these, cell phones and some types of baby monitoring devices emit the strongest high-frequency fields (Schmid et al. 2007; Streckert 2012). The radiation protection limit values must be observed in any case. The Federal Office for Radiation Protection (BfS) nevertheless recommends giving preference to cell phones and smartphones with low field intensity (ie with the lowest possible specific absorption rate, "SAR value", see "Further information") and using baby monitoring devices with the lowest possible field intensity (e.g. B. to use devices that have been awarded the "Blue Angel". The fields of the other devices only reach a significant size for humans if they are operated directly on the body. This is e.g. This is the case, for example, with cordless DECT telephones or notebooks and tablet PCs with activated WLAN modules when they are worn or used directly on the body. However, field simulations with several simultaneously acting field sources in the home and office showed that the limit values are also observed at the locations of the field maxima. Human exposure from devices operated close to the body is generally higher than from devices that are a considerable distance away from the body. However, the total exposure remains well below the applicable limit values (Schmid et al. 2007; Streckert 2012). Even newer high-frequency technologies in the living environment, such as Compared to applications operated close to the body, eg intelligent electricity meters (smart meters) do not make a significant contribution to the overall exposure to high-frequency fields (see "Further information"). A great deal of additional information on the small transmitters occurring in the residential area can be found on the BfS website (see "Further information").
The frequency of the microwaves used in microwave ovens to heat food (2.45 GHz) is in a similar frequency range as the EMF of WLAN and some mobile phone applications (UMTS, LTE). However, the power used in the herds is around 4000 times higher than that of cellular networks and WLAN (LUBW / LfU 2010). The housing and the tight door prevent significant portions of the microwaves from escaping to the outside. The leakage radiation that occurs despite good shielding is, according to measurements by the BfS, about 1% of the specified limit value on the device surface and about 0.05–0.1% of the limit value at a distance of 30 cm. It is recommended to ensure that the devices are in a technically perfect condition. Children should not stand in front of or next to the running device in order to avoid unnecessary exposure (see "Further information").
High-frequency fields that reach the living environment from outside are mainly emitted by cellular base stations as well as radio and television transmitters. In some places, the fields from nearby amateur radio or directional radio transmitters, radar systems and, more recently, regional WiMAX radio networks are added - although only the most important transmitters are mentioned here.
The contributions of these high-frequency sources radiating from a distance to the total human exposure are far below the contributions from field sources that touch the body (such as a mobile phone) or that are operated close to the body, such as. B. a notebook on your thighs.This also applies if the distant sources involved in the scenario are in the majority compared to those in contact with the body and emit powers that are orders of magnitude higher (Streckert 2012).
In summary, a distinction must be made between the sources of electrical, magnetic and electromagnetic fields in the living environment:
- rather short-term, sometimes relatively high field exposure from magnets, electrical devices and lights as well as cell phones in one's own environment,
- a rather low permanent exposure due to the in-house power grid and local radio networks,
- a comparatively low long-term exposure to external power supply systems and the general supply of radio services.
The extent of exposure from the relatively powerful personal devices (e.g. cell phones, baby monitors) and the in-house radio networks (e.g. WLAN, Bluetooth, DECT) can generally be easily controlled. Exposure to the in-house power grid could at least temporarily be avoided by using a power switch. On the other hand, the low long-term exposure to external field sources - with the exception of certain shielding options for high-frequency fields (cf. LfU 2008) - cannot be controlled by in-house measures.
Acute effects of the fields
The acute effects of electric, magnetic and electromagnetic fields on humans have been well researched. The limit values were derived from these acute effects and aim to avoid harmful effects for humans.
By static electric fields the surface of the skin can be electrically charged. This happens in the living environment z. B. by rubbing on carpets or synthetic clothing. Here, micro-discharges on the body surface or movements of the body hair can be felt, which can be uncomfortable but harmless. Static magnetic fields penetrate the body tissue and can interact with charged particles in the body at high flux densities above the limit values (from 2–3 Tesla), which do not occur in the living environment.
Also through low frequency electric fields the described harmless charging effects occur on the skin. The electric field generated by an external 50 Hz alternating field inside the body is several hundred thousand to million times weaker than the external electric field (ICNIRP 2010). This field effect is therefore irrelevant from a health point of view with the field strengths occurring in the living environment. Low frequency magnetic fields penetrate the body almost unhindered. Above certain threshold values, the eddy currents triggered in the body can lead to a perceptible irritation of sensory receptors, nerve and muscle cells. Since such proven effects served as the basis for setting the limit values, they are excluded in the residential area through compliance with the limit values when using devices and systems.
in the Intermediate frequency range
A long-term increase in core body temperature by more than 1 ° C is considered to be harmful to health
the EMF changes its possible effects with increasing frequency. The irritant effect described above for low-frequency magnetic fields is increasingly transformed into a heating of the tissue caused by the field. The possible health effects are still comparatively little investigated here. Well-founded limit values also exist for this area, but international bodies still attach great importance to more detailed research into possible effects (SCENIHR 2015; WHO 2005a).
At EMF in High frequency range (from 10 MHz) the heat effect on the body tissue dominates. The heat is generated as frictional heat when neighboring molecules and charged particles move in the tissue. The very fast movement of these particles is triggered by the force exerted by the electrical component of the EMF on electrically charged groups of the molecules and on free charge carriers (ions). The limit values are chosen so that the body tissue cannot overheat. A long-term increase in the core body temperature by more than 1 ° C is considered to be the threshold for harmful effects. Experiments showed that this occurs with a field-related energy absorption in the body over approx. 30 minutes at a specific absorption rate (SAR) of 4 W / kg, if the fields act evenly on the whole body. As a precaution, the recommended basic limit value for the general population has been set with a safety factor of 50 at 0.08 W / kg for exposure of the whole body. In the case of local exposure of a part of the body, e.g. B. with a mobile phone to the ear, a SAR of 2 W / kg is the limit.
Further discussed effects of the fields
In addition to the acute effects, which have been clearly proven, other effects of the fields are discussed, namely with field strengths that are in some cases well below the limit values.
When health problems develop as a result of EMF exposure, those affected complain of a large number of different, rather unspecific symptoms, such as: B. tiredness, dizziness, or pain. While the symptoms are clearly demonstrable, a causal connection with the exposure to EMF below the limit values has not yet been scientifically proven. In the absence of clear diagnostic criteria, the WHO does not regard electrosensitivity as a medical condition and questions whether it is an independent medical problem (WHO 2005b).
Cancer and childhood leukemia
Regarding long-term domestic or occupational exposure to low frequency magnetic fields There was no evidence of an increased cancer risk in adults (e.g. leukemia, breast cancer or brain tumor; SSK 2008). In children, however, an increased risk of childhood leukemia after prolonged exposure to magnetic flux densities above 0.3-0.4 T was found in epidemiological studies. This prompted the International Agency for Research on Cancer (IARC) to classify low-frequency magnetic fields as “possibly carcinogenic” (2B) (IARC 2002). However, the results of the epidemiological studies could not be confirmed by animal experiments, and science does not yet know any mechanism of action that could explain the development of leukemia in weak magnetic fields.
Too prolonged exposure to high frequency EMF In addition to broadcasting, radar and other high-frequency field sources, research has concentrated more and more on mobile communications over the past 20 years. Since the head is most exposed to cell phones, brain tumors were predominantly examined. The IARC classified high-frequency fields as “possibly carcinogenic” after a summarizing assessment of the studies on cancer diseases (IARC 2013). The decisive factor was epidemiological studies, some of which indicated an increased risk of two types of brain tumors with intensive cell phone use. For other types of cancer (e.g. leukemia, lymphoma, breast cancer, testicular tumor) there was insufficient evidence of a connection. Since studies with observation periods of more than 15 years are currently still lacking, the WHO recommended further research on long-term exposure to mobile phones, especially taking into account children and adolescents (WHO 2010, 2014) - because they will use mobile phone services for much longer in the course of their lives than today's adults.
The studies available to date make it unlikely that it was due to domestic as well as occupational exposure low-frequency (50/60 Hz) magnetic fields increases the risk of Parkinson's disease and multiple sclerosis (MS). However, in some occupational groups there is evidence of a slightly increased risk of developing amyotrophic lateral sclerosis (ALS) or Alzheimer's disease for people who are heavily exposed at work. In the case of exposure in everyday life, there are so far only a few studies that indicate an increased risk of Alzheimer's disease (BFE 2016). However, neurodegenerative diseases are generally difficult to investigate because there are no official registers and diagnosis and exposure assessment are sometimes difficult. Here, too, further research still needs to be clarified.
An overview was given of the EMF occurring in the living environment and their possible effects. The low-frequency magnetic fields and intermediate-frequency fields generated by household appliances as well as the fields emitted by domestic radio applications (in particular from cell phones) are of primary importance. The limit values and device standards applicable in Germany and many other countries protect our body from excessive exposure, also taking into account the multiple exposure caused by many devices and systems operated at the same time. The large safety reserves taken into account in the limit values are decisive for this. Anyone who nevertheless wants to protect themselves or others - for example children - from field emissions can do so by increasing the distance to the field sources (even at night) and by taking simple behavioral measures, such as B .:
- Complete shutdown of the devices when not in use (no standby mode),
- The shortest possible duration of use (e.g. for cell phones),
- Use of devices that are marked as low-radiation,
- Use of headsets when using a mobile phone,
- Only switch on data traffic and / or WLAN for mobile devices when necessary.
Since there are still final scientific uncertainties and the corresponding need for research in some questions, these and other precautionary measures are recommended by the BfS (see BfS 2017).
ICNIRP: Guidelines for limiting exposure to time-varying electric, magnetic, and electromagnetic fields (up to 300 GHz). Health Phys 1998; 74: 494-522.
ICNIRP: Guidelines on limits of exposure to static magnetic fields. Health Phys 2009; 96: 504-514.
ICNIRP: Guidelines for limiting exposure to time-varying electric and magnetic fields (1 Hz to 100 kHz). Health Phys 2010; 99: 818-836.
LUBW / LfU: Electromagnetic fields in everyday life - current information on sources, use and effects. 2nd ed . Karlsruhe, Augsburg: LUBW - State Institute for Environment, Measurements and Nature Conservation Baden-Württemberg and Bavarian State Office for the Environment, 2010.
The complete literature list is available in the appendix as a PDF.
26. BImSchV: Ordinance on electromagnetic fields in the version published on August 14, 2013 (Federal Law Gazette I p. 3266), 2013
IARC (Ed.): Non-ionizing radiation, part 1: static and extremely low frequency (ELF) electric and magnetic fields. IARC Monographs on the evaluation of carcinogenic risk to humans, Volume 80. Lyon: IARC Press, 2002
IARC (Ed.): Non-ionizing radiation, part 2: radiofrequency electromagnetic fields. IARC Monographs on the evaluation of carcinogenic risks to humans, Volume 102. Lyon: IARC Press, 2013
SCENIHR: Final opinion on potential health effects of exposure to electromagnetic fields (EMF). 2015
Federal Office for Radiation Protection: SAR value
Federal Office for Radiation Protection: Intelligent Electricity Meters - Smart Meters
Federal Office for Radiation Protection: Applications of high-frequency fields
Federal Office for Radiation Protection: Microwave ovens
Co-authors of this article are:
Sarah Drießen, Dagmar Dechent and Dominik Stunder
For the authors
Dr. rer. nat. Frank Gollnick
femu - Research Center for Electro-Magnetic Environmental Compatibility,
Institute for Occupational Medicine and Social Medicine
RWTH Aachen University Hospital
Pauwelsstrasse 30 52074 Aachen
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