Toronto Study
Child Leukemia Connection
(part 2)


---------- Forwarded message ----------
Date: Sun, 26 Sep 1999 19:44:23 -0500 (CDT)
From: "Roy L. Beavers" <>
To: emfguru <>
Subject: News Release from the University of Toronto:

......This is the second of the two documents on the U. of Toronto 1999 EMF/childhood leukemia study......

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.

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