The results are published in the July 3 issue of the New England Journal of Medicine .
EMFs exist naturally inside the human body and in the surrounding environment.
But stronger fields are produced by power lines and electric appliances, which have been the focus of most research. The first study to suggest a risk from magnetic fields was published in 1979, when researchers reported that children who had died from leukemia or other cancers were about two to three times more likely than other children to have lived within 40 meters of a high-current power line. Several other groups of investigators later described similar findings based on proximity to power lines. When researchers have actually measured magnetic fields in children's homes, however, they have not found significantly increased risks of leukemia or other cancers. Previous studies on magnetic fields and childhood cancer have had one or more shortcomings that make interpretation of their results difficult.