The fears of some scientists that electromagnetic fields produced by power lines may cause cancer have been heightened by two recent studies from Sweden that show as much as a fourfold increase in the risk of leukemia among children who live near power lines.
The new reports are particularly compelling to experts because the Swedish researchers have compiled extensive evidence--available perhaps nowhere but Scandinavia--on the extent of exposure to electromagnetic fields, which are more commonly known as EMF. Poor documentation of EMF exposure has been the biggest criticism of the U.S. studies that first suggested such a link.
The studies are also the first to show that cancer risk goes up with increasing exposure, a finding that is considered crucial in validating an epidemiological study. But experts and the researchers cautioned that reaction to the reports should not be hasty because even the increased risk is still very small, "about one out of 20,000 children a year," said epidemiologist Maria Feychting of the Karolinska Institutetin Stockholm.
The authors of the reports will present their data in the United States for the first time this week at a Department of Energy-sponsored meeting in San Diego. The two studies--one of children and adults living next to high-tension power lines and the other of men exposed to EMF while they are working--are likely to become the primary focus of the meeting.
"This is the most important thing that has come down the pike in this area in years and years," said physicist Louis Slesin, editor of Microwave News, who has followed the EMF issue closely. "It rewrites the book on the whole issue."
The new studies "represent a real advance in the literature because they specifically counter some of the specific criticisms or problems in some of the past studies," said epidemiologist David Savitz of the University of North Carolina.
How American utilities will react to the study "will depend on what the Swedish utilities and government decide to do," said Peter Jump, a spokesman for the Edison Electric Institute, which represents electric utilities in Washington. "Its influence will be increased or decreased by that."
If that is the case, the study may prove very influential. On Sept. 30, Sweden's National Board for Industrial and Technical Development formally announced that from now on it "will act on the assumption that there is a connection between exposure to power frequency magnetic fields and cancer, in particular childhood cancer."
That statement marks "the first time a national government has recognized the EMF-cancer link," according to Microwave News. Sweden is considering actions ranging from establishing safety standards for new power lines to moving families with children away from power lines. The board expects to issue new exposure regulations within six months.
"We don't want to do something that we will discover in another year or two . . . is not of any help and may have even hurt," Jump said. "We're still in a bit of a quandary over what to do about it."
EMFs are all around us, from the motors in refrigerators to the radiation from a computer or television screen to the slight emissions from electrical blankets. They arise whenever an electrical current is passed through a wire. The greater the current, the higher the magnetic field. Such fields are the driving force for electric motors and electromagnets.
Such a field can produce subtle changes in living cells, and many researchers believe that the fields can lead to the unrestrained cellular proliferation that is known as cancer. No one, however, has yet demonstrated that an electric field can cause cancer in cells or animals grown in the laboratory. That would be "the smoking gun that would change people's views in an instantaneous and marked way," Savitz said
In the absence of such direct evidence, researchers have had to rely on epidemiological studies. In the past, similar studies showed the first link between smoking and lung cancer. But that link was more easily believed, experts agree, because the effects of smoking were so much larger and more readily visible than is the case with EMF.
Over the last 13 years, a variety of U.S. researchers have reported an increased risk of various forms of cancer, including leukemia, lymphoma and brain tumors, among children who live near power lines and among workers exposed to EMF on the job.
But critics have found faults with these studies. Among other problems, critics have charged that estimates of total exposure may have been inaccurate and that unforeseen bias may have occurred in selection of the control groups--those not exposed to EMF.
Also, studies by Savitz and USC epidemiologist John Peters found no association between cancer and EMF when they based their study on actual measurements of the fields near power lines, so-called spot magnetic field measurements.