Summary: BC Cancer Agency researchers and their colleagues used a unique approach to monitor personal electric and magnetic field exposure of nearly 800 children in five provinces and to investigate whether electric power lines and magnetic fields around their homes increased the risk of developing leukemia. The American Journal of Epidemiology is releasing the results in its May 1 issue.
VANCOUVER - There is no clear connection between exposure to power frequency electric and magnetic fields (EMF) and the risk of childhood leukemia, according to a 10-year study by BC Cancer Agency researchers and their collaborators, to be published on May 1 in the American Journal of Epidemiology. The BC Cancer Agency announced the results at a briefing session at the Vancouver Cancer Centre today.
The case-control study is the first in the world to measure the personal EMF exposure of children. It enrolled 399 children from five Canadian provinces who were diagnosed with leukemia between 0 and 14 years old between 1990 and 1995, and 399 children in a control group. Researchers designed a special Teddy Bear pack containing a monitoring device that continuously measured and recorded EMF levels. Each child wore the pack for 48 hours.
Personal magnetic fields were not related to risk of leukemia (relative risk for those exposed to over 0.2 microTesla of magnetic field =1.1, not statistically different from those with lower exposure). Nor was risk 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 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 and magnetic fields in and around the children's lifetime residences - in other words, their history of exposure.
"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.
Funding 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.
McBride says research on this topic began in 1979, when Dr. Nancy Wertheimer in Denver, Colorado began looking for causes for childhood cancer deaths.
"When she and her colleagues surveyed the children's environments, they saw differences in the power line configurations," McBride says. "They wondered whether these could be related to different magnetic fields in the home." Since then there have been more than 14 studies worldwide investigating the possible link.
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."
Leukemia is the most common form of childhood cancer. In Canada, approximately one of every 6,400 children is diagnosed with the disease before the age of 15 years. Causes of childhood leukemia are not well understood and several epidemiologic studies have suggested that children exposed to power-frequency electric and magnetic fields may be at increased risk.
Understanding risk factors for cancer and their distribution in the population is vital to prevention and early detection of cancer. The BC Cancer Agency's Cancer Control Research group conducts research into the distribution of and the causes of cancer. The group also conducts work in cancer prevention.
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.
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