Summary of results of study of power-frequency electric and magnetic fields and risk of childhood leukemia in Canada
Description
Reference: McBride ML, Gallagher RP, Theriault G, et al. Power-frequency
electric and magnetic fields and risk of childhood leukemia in Canada.
American Journal of Epidemiology May 1, 1999;149:831-42.
Leukemia is the most common childhood malignancy in Canada. The etiology of
leukemia is not well understood and several recent studies have suggested that
children exposed to strong low frequency electrical or magnetic fields may be at
higher risk of the cancer.
The results of this recently-published study do not show any clear
connection between exposure to power frequency electric or magnetic fields
(EMF), or living near powerlines with high current configurations, and an
increased risk of developing childhood leukemia.
This case-control study (comparing the experience of children with leukemia
and that of a group of children without leukemia - the control group) is the
only study in the world to measure the complete personal EMF exposure of
children. It enrolled 399 children from five Canadian provinces (BC, Alberta,
Saskatchewan, Manitoba, and Quebec) who were diagnosed with leukemia between 0
and 14 years old between 1990 and 1995, and 399 children of similar age and sex,
in a control group. Each child wore a pack containing a monitoring device that
continuously measured and recorded EMF levels for 48 hours. A further 24-hour
EMF measurement was collected in each child's bedroom.
Personal magnetic fields were not related to risk of leukemia (relative risk
for those exposed to over 0.2 microTesla of magnetic field around the time of
diagnosis =1.1 times those with lower exposure, not a statistical difference).
Estimates of personal magnetic field exposure at two years prior to diagnosis,
and over the child's lifetime, also did not show an increased risk of leukemia
for those with higher exposures.
In addition to gathering data about the children's personal exposure to
electric and magnetic fields, researchers assessed the type of and distance to
power lines in and around the children's lifetime residences. Risk of developing
leukemia was not increased with living near a power line with very high electric
current configurations (relative risk = 1.2, again not statistically different
from those living near underground wiring).
"In contrast to some earlier studies that showed a relation between
certain power line configurations and increased risk, this study presents
considerable evidence against such a relationship," says Mary McBride,
the principal investigator. "Our study has several advantages over previous
studies. The study is more comprehensive because we took measurements of many
sources. In particular, we conducted more direct assessment by monitoring
personal EMF exposure."
Other principal investigators on the study were Richard Gallagher,
head of the Cancer Control Research Unit at the BC Cancer
Agency and Dr. Gilles Theriault, from McGill University, Montreal.
Epidemiologists and pediatric oncologists from several provincial cancer
organizations also collaborated on the study.
"The Canadian study represents a careful and comprehensive assessment of
EMF and the risk of childhood leukemia," says Dr. Leslie L. Robison,
director of the Division of Epidemiology/Clinical Research and the chair of
Pediatric Cancer at the University of Minnesota Cancer Center. "The
conclusions of McBride and co-workers provide additional evidence that magnetic
field exposure are not of etiologic importance for leukemia occurring within the
pediatric age group."
"This study is good enough to add evidence against there being a
substantial association," Dr. David Savitz, chair of the Department of
Epidemiology at the University of North Carolina School of Public Health in
Chapel Hill (quoted in Microwave News).
Funding for the study came from the National Health Research and Development
Programme of Health Canada - through a
peer-reviewed granting process - and the Canadian
Electricity Association (CEA). The US Electric Power Research Institute
contributed a portion of the funding through the CEA.
What does the study mean to children and their families?
"We don't know a lot about the causes of childhood leukemia,"
McBride continues. "Some of the results from this study point to new
directions that could bring us closer to solid answers. Our goal is to discover
what we can do to prevent the cancer in the first place."
The BC Cancer Agency provides a
comprehensive cancer control program for the people of British Columbia by
working with community partners to deliver a range of oncology services,
including prevention, early detection, diagnosis and treatment, research,
education, supportive care, rehabilitation and palliative care. The BC Cancer Research Centre
conducts research into the causes and cures for cancer. The BC Cancer Foundation has a
mandate to raise funds to support the work of the Agency and Research Centre,
for a world without fear of cancer.
Principal Investigator
Research Team
Page created: Aug. 17, 1999
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