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What happens when I am exposed to EMFs?

AC fields create weak electric currents in the bodies of people and animals. This is one reason why there is a potential for EMFs to cause biological effects.  Currents from electric and magnetic fields are distributed differently within the body. The amount of this current, even if you are directly beneath a large transmission line, is extremely small (millionths of an ampere). The current is too weak to penetrate cell membranes; it is present mostly between the cells, not through them.

Currents from 60-Hz EMFs are weaker than natural currents in the body, such as those from the electrical activity of the brain and heart. Some scientists argue that it is therefore impossible for EMFs to have any important effects. Other scientists argue that, just as a trained ear can pick up a familiar voice or cry in a crowd, so a cell may respond to induced current as a signal, lower in intensity yet detectable even through the background 'noise' of the body’s natural currents. Numerous laboratory studies have shown that biological effects can be caused by exposure to EMFs. In most cases, however, it is not clear how EMFs actually produce these demonstrated effects.

Strong electric fields, such as those found beneath large transmission lines, can cause hair on your exposed head or arms to vibrate slightly at 60 Hz. This is felt by some people as a tingling sensation. EMFs from transmission lines can also in some circumstances cause nuisance shocks from voltages created by EMFs on objects like ungrounded metal fences.

What effects of EMFs have been reported in laboratory studies?

scientists Several kinds of biological effects have been reported in studies of electric and/or magnetic fields. A biological effect is a measurable change in some biological factor. It may or may not have any bearing on health. Overall, effects attributed to EMFs have been small and difficult to reproduce. Very specific laboratory conditions are usually needed for effects of EMFs to be detected. It is not known how EMFs actually cause these effects.

Laboratory studies to date have not answered questions about possible human health effects. These studies are, however, providing clues about how EMFs interact with basic biological processes. The cell membrane may be an important site of interaction with induced currents from EMFs.

Keep in mind that some of these effects are within the 'normal' range of variation. A biological response to a particular stimulus does not necessarily result in a negative health effect.


  • Changes in functions of cells and tissues
  • Decrease in the hormone melatonin
  • Alterations of immune system
  • Accelerated tumor growth
  • Changes in biorhythms
  • Changes in human brain activity and heart rate

What are some typical EMF exposures?

First, 'exposure' must be defined. Scientists are still uncertain about the best way to do this, because experiments have shown that several aspects of the fields may be relevant to biological effects. Should exposure be an average of changing magnetic field levels over some time period, or should it focus only on time spent in high fields above some threshold value? Are rapid field changes important? Does the frequency content play a role? Even though the average field level has been used widely to represent EMF exposure, it is possible that other definitions may relate more closely to any possible effects.

Second, EMF in the environment is very complicated. We are usually exposed to EMF from a large number of sources every day. Fields change both in time and space. A person's EMF exposure depends to a large degree on what he or she is doing in the field at the time.


Several kinds of small meters are now available that can be carried or worn by a person to record magnetic field exposures automatically. The figure below is an example of data collected with one of these meters. The magnetic field was measured every 24 seconds over a 24-hour period. For this person, field exposure at home was very low. The occasional spikes (short exposures to high fields) occurred when the person drove or walked under or over power lines or was close to appliances in the home or office.

Some studies have used these automatic gauss meters to measure human exposure to magnetic fields (see picture above). These studies tend to show that appliances and building wiring contribute to the low-level background magnetic field exposure that most people receive. People living close to large power lines tend to have higher overall field exposures. However, there is much individual variation among homes.

In this graph we see a random sample of the magnetic field exposure of an employee over a 24-hour period. This person works in an office with a computer and lives in an all-electric 'very low current configuration' house.

Source:  Infoventures

News Release from the University of Toronto and The Hospital for Sick Children ...

Magnetic Field Exposure Associated with Childhood Leukemia

June 15, 1999

Researchers at the University of Toronto and the Hospital for Sick Children have found an association between magnetic field exposures in residences and the risk of developing childhood leukemia.

The study, reported in two separate papers in the current issues of the International Journal of Cancer (IJC) and the journal Cancer Causes and Control (CCC), shows that children with higher exposures to magnetic fields in residences are two to four times more likely to develop leukemia compared to children who are less exposed. The study comprehensively measured magnetic field exposures inside and outside the children's homes. Wire code was also assigned to each residence. For some children, EMF exposures were measured by a personal monitor.

The authors report in IJC that overall, wire code -- a surrogate indicator of magnetic field exposure based on the physical characteristics of the line and proximity of the residence to power lines -- was not associated with an increased risk of developing leukemia. However, measured magnetic field exposure was associated with an elevated incidence of leukemia in children under age six who were exposed in residences occupied during the first two years of life.

A subset of the total study population wore a personal monitoring device which measured EMF during usual activities in the home over 48 hours. As reported in CCC, exposure to magnetic fields was associated with a two-fold increase in risk of developing leukemia.

When other factors such as residential mobility, power consumption, child's medical history and other environmental exposures were taken into account, children exposed to higher levels of magnetic fields were 4.5 times more likely to develop leukemia compared to less exposed children. Risks were higher for children diagnosed at less than six years of age and for those with acute lymphoblastic leukemia -- the most common type of leukemia in children.

"As the methods of assessing exposure were refined, we found that the association between magnetic fields and the risk of developing childhood leukemia became stronger, particularly in children diagnosed at a younger age," says lead author Dr. Lois Green, epidemiologist in the department of public health sciences at U of T and at Ontario Power Generation. "But this study does not establish that magnetic fields cause cancer. To date, laboratory research has not shown a plausible biologic mechanism supporting a cause and effect relationship."

Researchers compared 201 children living in the Greater Toronto Area (GTA) who were diagnosed with leukemia at 0 to 14 years of age between1985 and 1993 at the Hospital for Sick Children with 406 control children.

Where possible, magnetic field exposures were measured at all the GTA residences occupied by the child during the period of inquiry -- the only study to date to consider several different exposure time periods. A detailed questionnaire was also administered to gather information about other factors such as family history, which might be related to leukemia risk.

"Acute lymphoblastic leukemia is most commonly seen in children two to six years of age. The association we saw with this age group is interesting because the range of exposures to possible risk factors is smaller and shorter," says Dr. Mark Greenberg, professor of pediatrics at U of T and pediatric oncologist at the Hospital for Sick Children. "We don't know what it means however, because there is no good biologic explanation for how such exposure might work."

Another consideration, Green adds, is the possibility that lifetime exposures to magnetic fields may have been measured more accurately for younger children because the interval between diagnosis and measurement was short, thus reducing possible misclassification of exposure.

Funding was provided in part by the Ontario Hydro Services Company (formerly part of Ontario Hydro) and the Canadian Electrical Association.

   For more on the study or to reach Dr. Green, contact:
   Steven de Sousa
   U of T Public Affairs
   (416) 978-5949
   e-mail: [2]

Questions and answers about electric and magnetic fields and U of T/HSC leukemia research ...

   June 15, 1999

What are electric and magnetic fields?

   Electric and magnetic fields, referred to as EMFs, are invisible lines of force that surround all electrical appliances, house wiring, power lines in the street and high voltage transmission lines. These invisible lines of force are created by electric charges, which produce two kinds of fields: electric and magnetic. Electric fields are produced by voltage and magnetic fields are produced by current. A lamp that is plugged in but turned off produces an electric field. If the lamp is both plugged in and turned on it produces a magnetic field as well. Electric fields are easily shielded by conducting objects like trees and buildings. Magnetic fields are not easily shielded by most materials. EMFs exist almost everywhere. However, the intensity of magnetic and electric fields diminishes greatly as you move away from the source.

Why are you studying EMFs?

   In 1979 a study in Denver, Colorado first raised the possibility that residential proximity to power lines might be associated with childhood leukemia. Since that time there have been many studies which have attempted to clarify the relationship between electric and magnetic fields and the risk of cancer. However, the results of these studies have been inconsistent and sometimes conflicting.

   This current study by the University of Toronto and The Hospital for Sick Children was designed to improve the measure of EMF exposures and thereby better characterize the relationship with the risk of childhood leukemia.

What did your study investigate?

   The study involved a comprehensive assessment of the residential magnetic field exposures of 201 children with leukemia and 406 controls. In addition to measuring magnetic fields in the homes currently occupied by the study participants, we measured, where allowed, the magnetic fields in previously occupied homes. We used the following types of measurements: personal monitoring, interior and exterior point-in-time measures, and wire code.

   A subset of cases and controls whose current residence was relevant to our inquiry period wore a personal monitor that measured both electric and magnetic fields. For this residence we also assigned wire code and took measurements inside and outside the home.

What are the key findings of this study?

   For the study population overall, wire code, which is a surrogate measure of magnetic field exposure, was not associated with an increased risk of childhood leukemia.

   There was no consistent trend of increasing risk of leukemia with increasing exposure to magnetic fields.

   There was a suggestion that leukemia risk was more pronounced for    children diagnosed at less than six years of age in relation to magnetic field exposures measured in residences occupied earliest in the period of inquiry.

   Analysis of magnetic field exposures in the child's current residence showed a statistically significant increase in risk in relation to increasing levels of magnetic fields. However, electric field exposures in the home were associated with a decreased risk of leukemia.

   It's important to note that this study did not determine that EMF exposure causes childhood leukemia. Rather, there seems to be a correlation, which needs still further investigation.

   While I understand that there is no causal relationship between EMF exposure and the risk of childhood leukemia, are there steps I can take to reduce exposure to EMFs?

   In this study, the external electrical system is a major source of magnetic fields in homes. There is little which residents can do to alter this.

   Within the home, electrical equipment and elements of the household electrical system may contribute to magnetic field exposures. In our study, appliances contributed only a small amount to the children's measured exposure.

Are there certain electric appliances that are more likely to have high EMF measurements?

   It is important to remember that EMFs diminish rapidly as you move away from the source. Therefore, appliances that are used close to the body and for prolonged periods of time are more likely to contribute significantly to a person's exposure. Examples of these are hair dryers, can openers and other electrical equipment with a motor.

What are wire codes? Do they differ between cities / provinces?

   Wire codes are a surrogate indicator of magnetic (not electric) field exposures first developed by researchers, Wertherimer and Leeper. Wire code is a way of categorizing homes according to magnetic field levels. It does not involve measuring the fields, but rather considers the size, number and type of electrical conductors outside the home and their distances from the home.

   Because electrical distribution systems vary by jurisdiction, so can wire codes. The magnetic field levels in a given wire code category can vary from one jurisdiction to another.

What is the difference between your study and other studies that show there are no associations between EMFs and childhood leukemia?

   The most common differences between studies relate to how the exposures were measured, how the subjects were selected, how other factors which might also be related to leukemia were taken into account and how the data are analyzed.

What factors did you take into consideration when you were assessing EMF levels?

   We considered a large number of different factors that might also be related to childhood leukemia and/or exposure to magnetic fields. These included the child's medical history, reproductive history of the mother, exposures to pesticides, chemicals, x-rays, and medications taken by the mother during pregnancy.

How did you gather data on the subjects' EMF exposure? 

The study was very comprehensive in its assessment of exposure. Several different methods of measurement were used.

   We took measurements of magnetic fields around the outside perimeter of the home, inside the home (child's bedroom and two other rooms that were frequently used) and for a subset of children, we asked them to wear a personal monitor for up to two days. This monitor measured both electric and magnetic field exposures associated with the child's usual activities in the home. We also looked at wire code.

Did you differentiate between electric and magnetic field exposures?

   Measurements of the electric and magnetic fields were available for only a subset of the study population, 88 cases and 133 controls whose residence at the time of interview was relevant to the inquiry period. Although electric and magnetic fields usually appear together at power frequencies (60 Hertz), the relationship between the two is not constant and therefore, they must be measured separately. 

What are the risks to my unborn baby if I am exposed to EMFs? 

At this time, the risks, if any, are unknown. 

Source: EMF guru  

Links to:

Geopathic Stress

What are EMFs?

EMFs and Cancer



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