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Electric and Magnetic Fields
From morning to “lights out,” electricity makes our lives more comfortable and safe. Eight million people in the Northwest get their
electricity from the transmission grid owned and operated by BPA. With electric power, however come certain precautions that are
also well known. Electric power lines, household wiring, and appliances can cause serious injury from electric shock if handled improperly.
Magnetic fields are produced when electric current is flowing, so they are only present when an appliance is turned on. As the flow of electricity – the current – increases, the magnetic field increases. Magnetic fields pass through most objects and cannot be blocked as easily as electric fields. They are typically measured in milligauss.
Together, electric and magnetic fields are known as EMF. EMF is found everywhere there is electricity, including household wiring, electric appliances and power lines. Both electric and magnetic fields are strongest at the electrical source and diminish quickly with distance.
What do scientific studies say about EMF?
Health issues are important to everyone. Electricity is an essential part of our lives, and it is important to get the facts on EMF to make informed decisions. The issue of public health effects from electric and magnetic fields has been the subject of much debate. Research studies and scientific reviews have been conducted since the 1960s, and the results have been evaluated by international scientific and public health organizations and agencies. One of the largest evaluations of EMF to date was led by two U.S. government institutions, the National Institutes of Health and the U.S. Department of Energy This six-year project was designed to provide scientific evidence to determine whether exposure to power-frequency EMF involves a potential risk to human health. The agencies also developed materials to inform the public about EMF.
In 1999, the National Institute of Environmental Health Sciences (NIEHS) reported to the U.S. Congress that the overall scientific evidence for human health risk from EMF exposure was determined to be weak and that aggressive regulatory action was not warranted. However, the agency also concluded that EMF exposure could not yet be recognized as entirely safe because of weak scientific evidence that exposure may pose a small risk related to childhood leukemia. As such, NIEHS recommended a more passive approach with emphasis on additional scientific research and continued public/regulatory education.
How does EMF affect the siting of transmission lines?
As a federal agency, the Bonneville Power Administration relies on NIEHS and the U.S. Department of Energy findings and conclusions for guidance and direction when addressing EMF exposure for new transmission facilities. BPA often performs EMF assessments as part of the environmental process when designing and siting new transmission lines. EMF assessment is one of the many important factors that BPA considers when determining and selecting preferred project alternatives.
BPA will continue to monitor the latest scientific EMF research and will communicate new information to interested parties, particularly as part of the public information on its transmission construction projects.
Where can I get more information about EMF?
You can find more information about EMF at www.niehs.nih.gov/health/topics/agents/emf/ which includes the 1999 report to Congress and a brochure called “Questions and Answers about EMF – Electric and Magnetic Fields Associated with the Use of Electric Power.” Another excellent source for EMF information is the World Health Organization.
Electric and Magnetic Fields Brochures and Publications
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Transmission Services
