WASHINGTON — Evidence has failed to prove a relationship between exposure to electromagnetic fields--such as those produced by power lines and home appliances--and cancer and other health abnormalities, according to a report released Thursday by the National Research Council.
The long-awaited report, while reassuring, is not expected to put the controversy to rest. Some experts remain convinced that there is a link between childhood leukemia and proximity to EMFs, as the electromagnetic fields are called. Questions also have been raised about the relationship of EMFs to reproductive and developmental abnormalities and learning and behavioral problems.
The council, part of the highly respected National Academy of Sciences, examined 500 studies conducted during the past 17 years before concluding that its findings "do not support claims that electromagnetic fields are harmful to a person's health," said Dr. Charles F. Stevens, chairman of the council.
"Research has not shown in any convincing way that electromagnetic fields common in homes can cause health problems," said Stevens, who is an investigator with the Howard Hughes Medical Institute and a professor at the Salk Institute in La Jolla.
The possible connection between EMFs and health dangers has been hotly debated since 1979, when a study showed that children living close to high concentrations of certain types of electrical wires, or to utility substations that deliver power, were 1.5 times more likely to develop leukemia.
In its report, the council confirmed that there was a "weak but statistically significant" correlation between the incidence of childhood leukemia in residents of homes near certain kinds of wires, but said that no existing research has established that EMFs were responsible.
The link "may be the result of factors other than magnetic fields that are common to houses with the types of external wiring identified with the disease," the council said. The council included David A. Savitz of the University of North Carolina, who conducted one of the early leukemia studies.
Experts have said other factors common to homes near power lines could include such things as high traffic density, air quality, construction features of older homes, or even herbicides that might have been used in and around power lines to destroy foliage. The council called for additional research to explain and identify these factors.
Most Americans do not live near such substations or high-voltage lines, according to Dr. Robert S. Bobrow, a Long Island family practice physician who has written and lectured on electromagnetic fields and health. Bobrow, who was not a member of the council, said that only 5% of homes are near these power sources.
"They look like an erector-set construction, with thick numerous wires and very high poles," he said. "They are real eyesores. Most homes are not built near them because the houses would be difficult to sell. If you lived near them, you'd know them."
Most of the health questions that have been raised involve these outside power sources, rather than common home appliances such as hair dryers, microwave ovens and electric blankets--all of which also produce EMFs.
Electric blankets are now made in a way that negates exposure, Bobrow said, and most people are only exposed briefly to EMFs produced by other appliances. However, "if you live near these transmission lines, you're taking a bath in them for 16 to 24 hours a day--the exposure is constant," he said.
The council said that studies looking at the leukemia connection have been inconclusive, in part because "outside wiring correlates poorly with measurements of actual fields inside the home, in that it accounts for only a fraction of the fields inside."
Although scientists have tried to measure fields inside homes of children with the disease, the results "have been inconsistent and contradictory and do not constitute reliable evidence of an association," the report said.
Louis Slesin, editor of the New York-based "Microwave News," which has studied these issues for years, applauded the council for validating the existence of a pattern involving nearness to power lines and the development of childhood leukemia. However, he said, the council "set too tough a standard" for establishing proof that the cause was something other than EMFs.