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A hospital will usually have quite a bit of electrical equipment – think of all those monitors around the beds. That means the magnetic field may be slightly higher than in a home, simply because more electricity is being used. Some of the specialised equipment is a source of high magnetic fields. The commonest example is an MRI machine. This produces high static or DC fields, and raised but not so high fields at other frequencies. Another example would be some diathermy machines, which use radiofrequency currents and therefore produce radiofrequency EMF. In all these cases, there are strict exposure limits in place to protect patients and staff, and the equipment will have been assessed by a qualified professional. But there’s another EMF issue in hospitals. As well as producing high EMF, some of the specialised equipment – an MRI machine is again an example – could suffer interference if it was put into a high EMF environment. So, when necessary, hospitals ensure low-EMF environments. This applies to some equipment in universities or other research facilities as well, such as electron microscopes. Finally in the medical arena, an increasing number of people have pacemakers, defibrillators, or other active implanted medical devices. These can experience interference from high EMF. They are designed to revert to a safe mode in those circumstances, and there is no known instance of anyone coming to any harm from interference with an implanted medical device and the power system, but if you have any concerns, you should talk to your cardiologist or other doctor. X close
HOSPITAL X close Hospitals have quite a lot going on in EMF terms. They have a lot of electrical equipment. Some of that equipment is quite specialized and produces unusual EMF. And some equipment can be interfered with by EMF as well as producing them. show details
In electrical terms, a school is not that much different from a home. It has similar wiring circuits and similar electrical appliances in use, which produce magnetic fields in the same way as in the home. But schools will often have greater electricity use than the home – more appliances (computers, screens, lighting, etc) and more wiring – so the magnetic field in them may sometimes be slightly greater than the home. In the USA, teachers and students have been measured as having a median exposure (the level that half are above and half below) of 0.05 – 0.06 µT (0.5-0.6 mG). X close
SCHOOLS X close In electrical terms, schools are similar to homes, and produce similar EMF levels, maybe a bit higher. show details
A city or town street may often have electrical wires running along it, either on wood poles or under the road or sidewalk. Sometimes there can be several sets of wires, at different voltages. This means that there can be places on the sidewalk – directly underneath the overhead wires, or directly above the underground cables – where the magnetic field can be higher, perhaps up to 1 µT (10 mG). But of course, we don’t usually spend very long in those locations, we are usually walking or driving across them or past them. X close
CITY STREET X close The wires that often run along a street mean that the EMF, e.g. on the sidewalk, can be higher. show details
In electrical terms, an office building is not that much different from a home. It has similar wiring circuits and similar electrical appliances in use, which produce magnetic fields in the same way as in the home. But offices will often have greater electricity use than the home – more appliances (computers, screens, lighting, etc) and more wiring – so the magnetic field in them may sometimes be slightly greater than the home. In the USA, various office workers have been measured as having a median exposure of 0.06 µT (0.6 mG). X close
OFFICES X close In electrical terms, offices are similar to homes, and produce similar EMF levels, maybe a bit higher. show details
Some occupations involve higher exposures for workers than are normally experienced by members of the public, because they involve closer approach to high-power equipment. Industries which may have higher exposures to power-frequency EMF include electric welding, electrochemical processes, and induction heating, as well as the electric power industry. Examples of measured average exposures during a workday for various occupations include electrical engineers, 0.17 µT (1.7 mG); line workers in electric utilities, 0.25 µT (2.5 mG); auto mechanics, 0.23 µT (2.3 mG); and sewing machine operators, 0.68 µT(6.8 mG). These are median figures, so half the measured workers had higher exposures, half lower. For comparison, the equivalent figure for exposure in the home is less than 0.1 µT (1 mG). There are exposure limits in place (from international standards bodies such as the International Commission on Non-Ionizing Radiation Protection, ICNIRP, or, in the USA, the American Conference of Governmental Industrial Hygienists, ACGIH) to limit the exposures of workers to protect them from any known effects, and in most cases, it is relatively easy to make adjustments to work practices to reduce exposures if required. X close
INDUSTRY X close Some industries – e.g. welding, electrochemical, and induction heating – use high-power equipment that produces higher EMF exposures for their workers. show details
inside of house
Inside a home, there are localised areas of higher magnetic field close to electrical appliances (click on the "inside of house icon" to see more details). But when you are not close to an appliance, the field over the general area of the house – what we call the “background field” – actually usually comes from the distribution wiring outside the home, the 120 or 240 V “secondaries”, the service drops to the home, or sometimes the “primaries”, the next voltage up that feeds the transformers. These are either carried on wood poles along the street or behind the houses, or can be buried under the road or sidewalks. The way this wiring produces magnetic fields is all to do with how they are grounded (it can involve water pipes as well, as these are all connected to the grounding system). This makes it difficult to predict accurately the field in an individual home. But the median field in a USA home (the field which half the homes are above and half below), distant from appliances, is probably 0.06-0.07 µT (0.6-0.7 mG). Less than 1% of USA homes have a field above 0.4 µT (4 mG). X close
WOOD POLE & WIRES X close Often, the magnetic field over the general volume of a house, not close to any appliances, comes from the 120/240 V distribution wiring outside the house, either carried on wood poles or buried underground. show details
BREAKER PANEL / CONSUMER UNIT X close House wiring in general is not a significant source of magnetic field. (If the house wiring is a significant source, it often indicates that the wiring has been done in an unconventional way.) But the breaker panel or consumer unit can produce slightly higher fields, simply because there is more wiring and the individual wires may have greater separation.
As far as the power frequency or 60 Hz fields are concerned, a smart meter produces very low fields – lower, in fact, than the old-fashioned rotating-disk analogue meters. A smart meter communicates meter readings to the electricity company, nearly always using radio signals. There are different ways of doing this. Some use exactly the same technology as you’d find in a cell phone. That means that the radio-frequency electromagnetic field they produce is the same as a cell phone – except, of course, you don’t get as close to a smart meter as you do to a cell phone (which you hold in your hands or hold to your head), so your exposure from it is much lower. Other smart meters use a dedicated “mesh radio” system, where each meter has to communicate only to the next link in the mesh. Because they have only a low range, they are low power, and produce similarly low emissions. X close
SMART METER X close Smart Meters produce very low power-frequency EMF. They usually also produce radiofrequency EMF, at a low level because they need to have only a low range. show details
Heat pumps and air conditioners can be quite big units and consume a fair bit of power, so you might think they would produce high fields. But in fact, like most modern appliances, they are designed to be very efficient, so their emissions are lower than you might expect. Against the surface, you might find a maximum of 10 µT (100 mG), dropping down to background levels within a metre (3 feet) or so. X close
HEAT PUMP / AIR CONDITIONING X close Heat pumps and air conditioners are designed to be very efficient, and the EMF they produce is not that high and falls off rapidly with distance. show details
The solar panels on your roof produce direct current (DC) electricity. That means that they, and all the wiring from them up to the inverter, produce DC magnetic fields. The earth’s magnetic field is also DC, so the fields from the solar panels and wiring merely slightly perturb the existing geomagnetic field. The inverter itself is like any other electrical appliance; it produces a magnetic field that is highest immediately next to the surface, and drops rapidly with distance away. In fact, because inverters are designed to be efficient with modern electronics, they don’t produce an especially high field: perhaps 10 µT (100 mG)”. X close
SOLAR PV X close Solar panels, and the accompanying inverter, do produce EMF, both AC and DC, but usually not that high. show details
SMART METER As far as the power frequency or 60 Hz fields are concerned, a smart meter produces very low fields – lower, in fact, than the old-fashioned rotating-disk analogue meters. A smart meter communicates meter readings to the electricity company, nearly always using radio signals. There are different ways of doing this. Some use exactly the same technology as you’d find in a cell phone. That means that the radio-frequency electromagnetic field they produce is the same as a cell phone – except, of course, you don’t get as close to a smart meter as you do to a cell phone (which you hold in your hands or hold to your head), so your exposure from it is much lower. Other smart meters use a dedicated “mesh radio” system, where each meter has to communicate only to the next link in the mesh. Because they have only a low range, they are low power, and produce similarly low emissions.
CONSUMER ELECTRONICS / APPLIANCES Domestic appliances can produce both electric and magnetic fields – the electric field whenever they are plugged in, and the magnetic field only when they are operating and drawing current. The fields are highest very close to the surface of the appliance, and fall rapidly with distance. Typically, the magnetic field will have fallen down to background levels within 1 m (3 feet). A XX produces a typical magnetic field at 0.3 m (1 foot) away of XX. At the typical distance from it when you are using it, the magnetic field would be XX.
outside of house
Domestic appliances can produce both electric and magnetic fields – the electric field whenever they are plugged in, and the magnetic field only when they are operating and drawing current. The fields are highest very close to the surface of the appliance, and fall rapidly with distance. Typically, the magnetic field will have fallen down to background levels within 1 m (3 feet). A XX produces a typical magnetic field at 0.3 m (1 foot) away of XX. At the typical distance from it when you are using it, the magnetic field would be XX. X close
DOMESTIC APPLIANCES X close Domestic appliances produce electric fields whenever they are plugged in, and magnetic fields when they are operating. The fields are highest close to the surface and fall rapidly with distance. See more details on the fields from typical appliances below.
LCD TV X close An LCD TV produces a typical magnetic field at 0.3 m (1 foot) away of up to 0.25 µT (25 mG). At the typical distance from it when you are watching it, the magnetic field could be up to 0.06 µT (0.6 mG).
ELECTRIC STOVE X close An electric stove produces a typical magnetic field at 0.3 m (1 foot) away of 0.1-0.5 µT (1-5 mG). At the typical distance from it when you are using it, the magnetic field could be up to 2 µT (20 mG).
LAPTOP X close A laptop computer produces a very low field – often negligible, or perhaps up to 0.01 µT (0.1 mG) at the typical distance from it when you are using it.
REFRIDGERATOR X close A refrigerator/freezer produces a typical magnetic field at 0.3 m (1 foot) away of up to 2 µT (20 mG).
WASHING MACHINE X close A washing machine produces a typical magnetic field at 0.3 m (1 foot) away of 0.1-3 µT (1-30 mG).
EV CHARGING X close Chargers for electric vehicles (EVs) can range in power from a few kilowatts up to fast chargers at tens or even hundreds of kilowatts. But home EV chargers tend to be lower power, and to supply alternating current (AC) to the car, with the conversion to the direct current (DC) that the battery needs happening in the car. A typical charger may produce a magnetic field of a few microteslas (a few tens of milligauss) at different locations close to its surface, and, typically, lower fields close to the cable. The field falls rapidly with distance and the area of this elevated field is quite limited – within 30 cm (1 foot) the field will be only a fraction of the field on the surface.
Solar panels produce direct current (DC) electricity. That means that they, and all the wiring from them up to the inverter, produce DC magnetic fields. The earth’s magnetic field is also DC, so the fields from the solar panels and wiring merely perturb the existing geomagnetic field. The earth’s magnetic field is a few tens of microteslas (hundreds of milligauss) depending on latitude, and the DC fields produced by the panels and cables rarely exceed this level. This happens only within a few metres (tens of feet) of the panels and wiring; beyond that, the effect becomes very small. X close
SOLAR FARM X close Solar panels produce DC or Direct Current magnetic fields, which, over a limited area, can perturb the earth’s magnetic field. show details
Solar farms will always have an inverter to change the direct current (DC) produced by the solar panels to the alternating current (AC) used by the electricity grid. They may have batteries as well to store electricity. The inverter itself is like any other electrical appliance; it produces a magnetic field that is highest immediately next to the surface, and drops rapidly with distance away. The highest field close to the surface is generally less than 100 µT (1000 mG), depending on the design and power of the inverter. X close
BATTERY & INVERTER X close The inverter at a solar farm, and any batteries, produce EMF only over a limited area. show details
Ships use various radio-frequencies, for radar, navigation, and communications. And radiofrequencies are used in all sorts of other processes in everyday life as well, in the home and outside. The frequencies can vary a lot, from hundreds of kilohertz (kHz, or a thousand cycles per second) up to over a gigahertz (GHz, a billion cycles per second), and the power levels can vary too, but they are all designed to be compliant with the relevant exposure limits. X close
BOAT RADAR & COMMUNICATIONS X close There are many uses of radio, microwaves, etc, for communication, navigation, and other purposes, including by shipping. These therefore produce EMF. show details
Chargers for electric vehicles (EVs) can range in power from domestic units at a few kilowatts up to fast chargers at tens or even hundreds of kilowatts. That puts the fast chargers among the more high-power items of electrical equipment we encounter in everyday life. Charging can be AC or DC. Lower-power chargers tend to supply alternating current (AC) to the car, with the conversion to the direct current (DC) that the battery needs happening in the car. Higher-power chargers convert the AC of the electricity supply to the DC that the EV needs within the charger. A typical fast charger may produce a magnetic field of a few microteslas up to maybe a few tens of microteslas (a few tens up to a few hundreds of milligauss) at different locations on its surface. The field falls rapidly with distance and the area of this elevated field is quite limited – within 30 cm (1 foot) the field will be only a fraction of the field on the surface, and it is likely to have fallen down to background levels at 1 m (3 feet) or not much further away. For DC charging, the DC current produced by the charger passes down the charging cable to your EV. This produces a mainly DC magnetic field. This is the same type of field as the earth’s magnetic field, so the effect is just to perturb the DC field from the earth that we are exposed to anyway. With AC charging, the current in the charging cable is AC, but as these are lower power and the cable is compact, the magnetic field it produces is low. X close
EV CHARGING X close EV chargers range from smaller domestic units to high-power fast chargers. They do produce EMF, but only in a limited area around them. show details
OUTSIDE FENCE For a member of the public, the electrical equipment inside a power station is too far away for it to affect their exposure. Outside the perimeter fence or wall, the highest fields come not from the power station itself but from the power lines that carry the power away. Depending on the power and voltage, there might be places directly under an overhead line (or, sometimes, directly over an underground cable) where you could experience magnetic fields up to 10 µT (100 mG).
BIG TOWER Larger transmission lines are used to carry large quantities of electrical power over larger distances. They are at higher voltages, typically, in the USA, 230 kV, 345 kV, 500 kV, or 765 kV, because this is more efficient (less power is wasted as heat than at lower voltages). A line at higher voltages produces a higher electric field (directly because of the voltage) and a higher magnetic field (because the currents carried are also usually larger, and the spacing of the wires is greater). Directly under the line, where the field is the highest, the typical magnetic field for, for example, a 500 kV power line could be 10 µT (100 mG). The field still falls off quite rapidly to the sides of the line, but the range of the field is larger than for smaller distribution lines. For this 500 kV example, the magnetic field would fall below 1 µT (10 mG) at about 80 m (250 feet) away from the line.
Inside a power station, the highest fields produced are close to the generators and the cables leading from them to the transformers that send the electricity produced into the grid. It doesn’t make much difference whether the generators are powered by coal, oil, gas, or even nuclear; the generators themselves are always quite similar. Workers can experience quite high fields – in very limited locations, up to a millitesla (mT, 10 gauss) – but as they wouldn’t spend extended periods very close to the generators during a typical shift, their average exposure is not actually that high. These regions of higher field are entirely within the confines of the power station – a member of the public wouldn’t experience them at all. (close)
INSIDE A POWER PLANT X close There are areas inside power stations with high EMF. But these affect workers only, not members of the public. show details
For a member of the public, the electrical equipment inside a power station is too far away for it to affect their exposure. Outside the perimeter fence or wall, the highest fields come not from the power station itself but from the power lines that carry the power away. Depending on the power and voltage, there might be places directly under an overhead line (or, sometimes, directly over an underground cable) where you could experience magnetic fields up to 10 µT (100 mG). X close
OUTSIDE A POWER STATION X close Outside a power station, the highest EMF usually comes from the power lines that carry the power away, not from anything inside it. show details
There has been a lot of research into possible effects of EMF on animals, farming, etc., and it is almost all reassuring. Scientists have looked, for example, at crop yields, milk production from cows, weight gain, and reproduction, and concluded that there are no adverse effects. There can be a minor issue with bees experiencing induced voltages on a hive directly under a line, but this is easily fixed, and there is evidence that bees can actually fare better in the corridors along power lines. X close
ANIMALS X close Evidence suggests that there are no effects of EMF on animals or crops. show details
On a typical radio mast or pylon, there may be a whole variety of antennas and dishes. Some will be cell-phone base stations, some local repeaters for radio or TV broadcasts. If there are dishes, a metre or so (a few feet) across, these are probably microwave links for transmitting data. The design of the dish creates a narrow beam (it is more efficient that way), so EMF exposures outside the direct beam are usually very low X close
MICROWAVE DISH X close A dish focusses the EMF in a narrow beam, so the EMF in areas outside the beam, where the public can be, is low. show details
Cell phones operate at high frequencies, around 1 GHz (gigahertz, or a billion cycles per second), which are collectively known as “radiofrequencies”. They therefore produce radiofrequency EMF. Successful operation of cell phones requires antennas (also called “base stations” quite frequently, especially in urban areas. They can be mounted on buildings, but often they are found on poles or pylons, which often carry a whole variety of antennas and dishes. Very close to the front of the antenna, the radio-frequency EMF can be quite high. In fact, it can be too high to be safe for human exposure (very high levels of radio-frequency EMF can cause heating in human tissues). The distance for this to happen depends on the design and power of the antenna, but would rarely be more than 3 m (10 feet). So the antennas will usually have to be switched off before anyone works on them. But members of the public do not get that close to the antennas. By design, the antennas are raised up above ground and pointing slightly downwards. Directly underneath them, or even at the distance away where the beam from the antenna hits the ground, exposures are much lower, well below the exposure limits. X close
ANTENNA X close Right in front of a cell-phone antenna the radiofrequency EMF is quite high, but they are designed so that the EMF in areas which the public can access is much lower. show details
Inside a power station, the highest fields produced are close to the generators and the cables leading from them to the transformers that send the electricity produced into the grid. It doesn’t make much difference whether the generators are powered by coal, oil, gas, or even nuclear; the generators themselves are always quite similar. Workers can experience quite high fields – in very limited locations, up to a millitesla (mT, 10 gauss) – but as they wouldn’t spend extended periods very close to the generators during a typical shift, their average exposure is not actually that high. These regions of higher field are entirely within the confines of the power station – a member of the public wouldn’t experience them at all. X close
Substations are where power lines are switched to direct power flows as needed, and transformers change the voltage of the power. They range in size from the largest transmission substations, with voltages over 100 kV and extending over several acres, to the smallest substations found in residential areas to supply power to local homes. Substations always contain specialised equipment such as transformers and switchgear that produce elevated EMF. But the EMF from that equipment falls rapidly with distance and rarely extends outside the perimeter of the substation. Nearly always, the highest EMF around a substation is found where the various power lines enter and leave it, either overhead or underground. X close
SUBSTATION X close Substations are where power lines are switched and transformers convert voltages. Outside the perimeter fence, where the public have access, substations themselves don’t usually produce high EMF – the EMF comes from the wires entering and leaving. show details
Larger transmission lines are used to carry large quantities of electrical power over larger distances. They are at higher voltages, typically, in the USA, 230 kV, 345 kV, 500 kV, or 765 kV, because this is more efficient (less power is wasted as heat than at lower voltages). A line at higher voltages produces a higher electric field (directly because of the voltage) and a higher magnetic field (because the currents carried are also usually larger, and the spacing of the wires is greater). Directly under the line, where the field is the highest, the typical magnetic field for, for example, a 500 kV power line could be 10 µT (100 mG). The field still falls off quite rapidly to the sides of the line, but the range of the field is larger than for smaller distribution lines. For this 500 kV example, the magnetic field would fall below 1 µT (10 mG) at about 80 m (250 feet) away from the line. X close
LARGER POWER LINES X close All power lines produce EMF underneath them, which fall off with distance to the sides. With larger power lines, used for transmission at voltages above 200 kilovolts, the maximum EMF and the distance to fall away are both higher, though still always within the levels determined as safe for public exposure. show details
Power lines operate at a whole range of voltages. Generally, the higher the voltage, the bigger the tower or pylons carrying the wires. The biggest transmission lines are at 230 kV and above, but beneath this, there are plenty of smaller power lines – typical voltages include 115 kV, 69 kV, and 35 kV – which may be referred to as “transmission”, “subtransmission”, or “distribution” lines. They will typically be carried on larger wood poles, or smaller lattice steel pylons. For any power line, the highest EMF is directly underneath it, and where the conductors are closest to the ground. The EMF fall rapidly with distance away from the line to the sides. Directly under the line, the magnetic field for a typical power line at, for example, 115 kV, could be 4 µT (40 mG). For this example, the magnetic field would fall below 1 µT (10 mG) at about 20 m (60 feet) away from the line. X close
SMALLER POWER LINES X close All power lines produce EMF underneath them that fall off to the sides. With smaller power lines, often called “subtransmission” or “distribution”, the maximum EMF and the distance to fall away are both smaller. show details
The electricity industry isn’t the only industry where staff can be exposed to high EMF (EMF are an issue for welding, induction heating, electrochemical processes, and others). But some electricity industry staff can certainly experience elevated EMF. For example, working in a substation has been measured as a median exposure (the value that half are above and half below) to magnetic fields of 0.72 µT (7.2 mG), electricians of 0.54 µT (5.4 mG), and line workers of 0.25 µT (2.5 mG). Electricity companies are very conscious of safety and have strict procedures in place to protect their staff, including procedures to make sure they are never exposed to unsafe levels of EMF. X close
UTILITY WORKER X close Some utility workers are among the occupations that receive higher EMF exposures. show details
“EMF” covers both electric and magnetic fields. Placing a power line underground eliminates any external electric field (the sheath of the cable captures the electric field). But underground cables still produce magnetic fields. The size of the magnetic field depends on the type of underground cable and its design. The magnetic field directly above an underground cable can sometimes actually be higher than underneath the equivalent overhead line, because you can be closer to the cables – they may be buried only a metre or so (three feet) below ground, as opposed to being maybe 10 metres (30 feet) in the air. But the individual wires are usually closer together when they are underground, and that means that the magnetic field falls even more rapidly with distance to the sides. Overall, the region where there is an elevated magnetic field is usually less for the underground cable than the overhead line. The actual fields produced are very dependent on the design of underground cable. For one specific example of a transmission line, the underground cable might produce (at 1 m (3 feet) above ground) 8 µT (80 mG) directly above it, compared to 5 µT (50 mG) for the equivalent overhead line. But, for this example, for distances away from the cable greater than 3 m (10 feet), the field from the underground cable is less than for the overhead line X close
UNDERGROUND WIRE X close Putting wires underground eliminates the electric field. There’s still a magnetic field, but, to the sides of the wires, it’s smaller. show details
Submarine cables and their impact on marine life.
Click the shark
Most offshore windfarms send their power ashore in alternating current (AC) cables, either laid on the seabed or buried beneath the seabed in a shallow trench. The design of the cables can vary depending on the size of the windfarm (the electrical power it generates). These cables may produce a magnetic field in their immediate vicinity in the sea. Click on the shark to see the latest scientific evidence on whether this has any effects on marine life. As well as AC cables under the sea from windfarms, there can sometimes also be direct current (DC) cables, from a windfarm a long way offshore or from an interconnector between two different electricity systems separated by a sea. These produce DC magnetic fields. The earth’s magnetic field is also DC, so the fields from the cable simply modify the existing geomagnetic field rather than producing anything new. X close
SUBSEA CABLES X close Subsea cables do produce EMF, but any effects are very limited. show details
There is a wide variety of marine animals (from tiny amphipods to the largest whales) that utilize EMF. Based on current knowledge, the animals with the most acute sensitivity to magnetic fields are turtles, cetaceans (whales, dolphins and porpoises) and some migratory fish, while those most sensitive to electric fields are the elasmobranchs (sharks, skates and rays). These animals are able to perceive changes in EMF hundreds to thousands times lower than the maximum EMF predicted to be generated by subsea power cables. The evidence base to date has been focused on simple, laboratory studies that create either magnetic or electric fields and very few have used actual cable EMFs. Although there may be evidence of effects for some species, whether these effects lead to biologically significant impacts remains unknown. X close Reference: EPRI, Characterisation of the EMF Environment Associated with Submarine HVDC Cables and Evaluation of Potential Effects Upon Marine Animals (3002028429)
MARINE LIFE X close Effects of EMF from subsea cables on marine life can be transient but whether these effects lead to long term, biologically significant impacts at the population level remains unknown. show details
