MAGNETIC FIELDS
SUMMARY:
There are two types of magnetic fields; natural static magnetic fields and man-made alternating magnetic fields. Most magnetic fields we are exposed to come from electric motors, or from the wiring in our house. They are called ELF or Extremely Low Frequency fields, and serious health problems have been associated with them, even at relatively low levels.
DETAILS:
A magnet is a material that has a particular orientation and spin of its electrons such that it creates a magnetic field. Physics cannot further explain how this occurs; it is just one of the mysteries of the universe. The field that a permanent magnet creates is called static magnetic field. Its strength does not change significantly over time. A permanent magnet always has two poles, and the magnetic lines of force are defined as going from the north pole to the south pole of the magnet. Permanent magnets do not have an electric field. Historically the most common use for a permanent magnet has been for the needle of a compass, which aligns itself with the permanent magnetic field of the earth.
Technology always advances in every field and so it is with magnets. MagLabs Pulsed Field Facility inside the Los Alamos Laboratory in New Mexico claims to have the strongest re-usable magnet in the world. They have achieved a level of 100 Tesla - for 0.015 seconds. This power allows new levels of scientific research to be done. To put this in perspective, most magnetic fields we encounter are measured in millionths, or billionths of a Tesla! Click on the picture for the incredible story. Then close the window to return here.
Electric motors are the most common source of magnetic fields in people’s lives. An electric motor has two essential parts; the rotor and the stator. The rotor consists of coils of conductive wire. It rotates when current is sent through it to create a magnetic field. That field reacts with the magnetic field that exists in the stator, using the basic principle of magnets, that opposite poles attract and the same poles repel. The stator can be either permanent magnets or another collection of coiled conductive wire with current sent through it. Generally electric motors create fluctuating magnetic fields as they operate, called AC magnetic fields. And since electric motors use electricity to operate, they also produce electric fields, also usually alternating in intensity or polarity.
Of most concern in an EMF safety analysis are motors that come in close contact to people at work or in their home. The chart below shows the result of research done in 1997 by Kim YS et al It shows the wide range of possible magnetic field exposure from various common household appliances.
The units in the chart are µT – or micro Teslas. In the 20+ years since this research was done, many studies have found that ELF (extremely low frequency) magnetic fields are much more damaging than previously thought. Most of the professional Gauss or Tesla meters today use the unit nT, or nano Tesla. One microTesla equals 1,000 nanoTesla. The exposure guidelines published by the International Building Biology Institute are also in nT units. So to convert to the guideline units, each number in the chart below needs to be multiplied by 1,000 for comparison.
The BB guidelines are for sleeping areas. Sleep is the time when you must have the lowest possible exposure to all forms of pollution so your body can heal and repair while in deep sleep. Temporary exposures could be 10 or more times higher. But anything over 0.1µT in the chart below (100nT) is considered a severe exposure while sleeping.
That standard is met only by an iron and a desk lamp. We see from this information that for a healthy life, you do not want to spend a lot of time in a massage chair or under an electric blanket. And an electric blanket also creates a huge electric field, covering your entire body!
There are also other sources of magnetic fields that can be unhealthy. If an electrician tries to save cost on the wire he buys, he may make bad decisions in wiring techniques. A three way switch that uses a two wire connection, or a situation where neutral wires are not kept separate, can result in large magnetic fields due to net currents on circuits, or circuit branches. You need a trained EMF consultant working with a highly skilled electrician to investigate, identify, and correct these situations. Another common thing that most people don't think about is an AC powered alarm clock next to your bed. The field at 2 feet can be 200nT. And another often missed source for a magnetic field is the metal bed frame or springs, which can distort the health supporting effect of the natural magnetic field of the earth.
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Years ago fluorescent lighting used magnetic ballasts. These created large low frequency magnetic fields that also caused lighting flicker. They have been banned, but still exist - and unfortunately often in old school buildings.
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Magnetic fields are very difficult and expensive to mitigate with shielding. An apartment complex with a large transformer near units may make those units impossible to mitigate to acceptable levels of magnetic flux density. To meet the most stringent requirements, even a utility transformer in your front yard may be unacceptable.
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A possible association between extremely low-frequency electromagnetic fields (EMFs) and childhood leukemia has been extensively studied during the last several decades. In a review from 1998, the National Institute of Environmental Health Sciences stated that extremely low-frequency EMFs are possibly carcinogenic to humans, partly on the basis of studies of childhood leukemia. In other studies, people have reported a variety of symptoms such as skin redness, tingling and burning sensations, as well as fatigue, headache, concentration difficulties, nausea, and heart palpitations. But since these were not controlled experiments and it is difficult to maintain an environment where only the extremely low-frequency magnetic field exists, with no other fields, scientists discount these self-identified effects.
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However, the experience of Building Biologists over many years has proved that serious health problems do occur in sensitive people. For more information see the detail section of the Electric page.