Cancer Study Finds No Link to Power Lines
The magnetic fields generated by electric power lines and household appliances do not appear to cause leukemia in children, according to the largest, most thorough study yet of a question that has worried and even panicked many Americans for nearly two decades.
The eight-year, $4.5-million National Cancer Institute study of more than 1,200 children should help ease one of the most insidious health scares in recent memory. The new evidence is a “turning point” in the controversy, said Dr. Dimitrios Trichopoulos, chief of epidemiology at the Harvard School of Public Health.
In the study, which appears in today’s New England Journal of Medicine, researchers led by the institute’s Dr. Martha Linet, a cancer epidemiologist, located 638 children diagnosed with acute leukemia and 620 children without the disease. The researchers measured electromagnetic fields, or EMFs, inside the households where most of the children were raised, and noted the size and proximity of nearby electric power lines.
They found that the children with cancer were not exposed to electromagnetic fields any stronger or more pervasive than those experienced by the other youngsters.
Linet said she hoped that the work would dispel fears. “Based on our results,” she said, “is this likely to be an important cause of childhood leukemias? The answer is no.”
The American Cancer Society’s vice president for epidemiology and surveillance research, Dr. Clark Heath, said the “extraordinarily well-done study” makes “a strong statement about the lack of association” between electric power lines and childhood leukemia.
Over the years, some researchers have proposed that exposure to electromagnetic fields might also increase the risk of other diseases and health problems, including miscarriages, breast cancer and Alzheimer’s disease. But a National Academy of Sciences panel report last fall found little evidence for such links, though it left open the childhood leukemia question.
The possibility that low-level electromagnetic fields might cause acute lymphoblastic leukemia, the most common childhood cancer, was first raised in 1979. Colorado researchers found that a cluster of children with childhood leukemia lived closer to high-voltage power lines than did children without the disease.
Since then, scores of different studies followed up on that link, both confirming and arguing against it. A couple of well-received studies found that living close to high-voltage power lines increased children’s risk of leukemia 1.5 to 2 times.
Other researchers noted that acute lymphoblastic leukemia has become 20% more common over the last two decades as the nation has become more densely crisscrossed with power lines and more dependent on gadgets. Responding to such observations, citizens groups, attorneys and journalists publicized the apparent link, prompting some parents to sell homes near power lines to reduce their children’s risk of disease.
Acute lymphoblastic leukemia, which has a 70% survival rate, affects about 1,600 children in the United States. Although it is the most common childhood cancer, and a leading cause of childhood death, it is relatively rare, considering the more than 61 million American children age 15 and under.
The new cancer institute study was designed to address shortcomings in previous research. Although other studies had relied on indirect estimates of exposure to electromagnetic fields generated by power lines, the institute team went inside hundreds of houses to take one-day measurements in kitchens, family rooms and children’s bedrooms. They also measured EMFs inside mothers’ bedrooms to check on prenatal exposures.
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Most important, the scientists found no correlation between disease and the proximity or power of high-voltage power lines--the reported association that sparked the issue 18 years ago.
“This [study] carries a very substantial amount of weight saying it’s less likely” that power lines cause childhood leukemia, said Dr. David Savitz, chief of epidemiology at the University of North Carolina. Savitz, who led a 1988 studying proposing just such a link, agreed that this new research “undermined” his own findings.
Dr. Charles Stevens, a neurobiologist at the Salk Institute in La Jolla who led last year’s National Academy panel, said the new study was “the best one to date, the most careful and complete.”
But proponents of the EMF-cancer link criticized the institute team for downplaying one of their findings. Overall, the researchers found no increased leukemia risk at the levels of EMF commonly encountered. But in a handful of households, the EMF levels were considerably elevated, and in those the leukemia risk was also higher.
“It is being played as an absolutely negative study, but I don’t think the data published in the journal supports that contention,” said Louis Slesin, an environmental policy specialist and editor of Microwave News, which has reported aggressively on the possible cancer link. He said the findings were “equivocal.”
Linet countered that criticism, saying the apparent cancer link at certain, very high EMF levels was a statistical fluke perpetrated by the small number of cases in that category. If the effect were real, she said, the researchers would also have observed it at the highest EMF level, but that was not the case.
An editorial by a New England Journal editor was strikingly dismissive of the EMF cancer controversy.
“The many inconclusive and inconsistent studies have generated worry and fear and have given peace to no one,” wrote Dr. Edward Campion. Linet’s study, he said, supports the conclusion “that there is no convincing evidence that high-voltage power lines are a health hazard or a cause of cancer.”
