Danger Overhead

By Christine Gorman

CAN POWER LINES CAUSE CANCER? Numerous reports in the popular press have blared out warnings. Frightened citizens have abandoned homes located close to high-tension wires; others have gone to court to keep the lines away. The reason for the hysteria: a growing number of scientific studies suggest that the risk of leukemia and other malignancies rises with exposure to electromagnetic fields, which are generated in varying degrees by all electrical devices from high-voltage power lines to hair dryers.

Until now the studies have been ambiguous. Some have found an association with brain cancer but not leukemia in children. Others have detected just the opposite. In addition, the link to cancer appears stronger when the electromagnetic field is estimated by researchers and disappears when it is measured by instruments.

This fog may finally start to clear because of two studies done in Sweden. The first, led by epidemiologists Maria Feychting and Anders Ahlbom of Stockholm's Karolinska Institute, looked at everyone who lived within 300 m (328 yd.) of a high-tension line in Sweden from 1960 to '85. Although the investigators could find no evidence of an increased cancer threat for adults, they did detect a higher risk of leukemia in children. The second study, led by Birgitta Floderus of Sweden's National Institute of Occupational Health, linked on-the-job exposure to electromagnetic fields and leukemia in workingmen.

Although the research does not prove cause and effect, it shows an unmistakable correlation between the degree of exposure and the risk of childhood leukemia. "From a research point of view, they add significant information," says Stan Sussman, manager of electromagnetic-field studies for the Electric Power Research Institute, a California-based organization funded by utility companies. "It is becoming more and more likely that there is something associated with living near high-power lines, especially for childhood leukemia."

The results have prompted Sweden's government to consider whether new regulations are needed. A task force will look at the concentration of schools and day-care centers close to power lines. According to Microwave News, a U.S. * publication that covers the field in depth, this is the first time a national government has acknowledged the link.

What makes the Karolinska study particularly significant is the thoroughness of its design. The investigation encompassed nearly 500,000 people. By restricting their analysis to high-power transmission lines, the researchers could easily calculate the field strength for each household studied and be assured that the lines were the dominant source of electromagnetic radiation. Since field strength drops off dramatically with distance and all the houses were in the same corridor, investigators could also be fairly certain that the only difference between exposed and unexposed homes was proximity to the lines, not other environmental factors.

One of the most telling results was that the cancer risk grew in proportion to the strength of the electromagnetic field. Children with constant exposure to the weakest fields, calculated at less than 1 milligauss (about the same that a coffee maker generates when it is brewing), had the lowest incidence of cancer. Those exposed to fields of 2 milligauss showed a threefold increase in their risk, while children exposed to 3 milligauss showed a fourfold increase in the risk of leukemia. Such a clear progression makes it difficult to argue that factors other than exposure to the electromagnetic field were responsible for the extra cases of leukemia.

However, the report does have some weaknesses. Childhood cancer is so rare that even such a large study was able to uncover only 142 cases. In the highest exposure groups, the calculation for leukemia risk was based on as few as seven cases. In addition, the Swedes found no increase in malignancies of the brain. "Up to this point the evidence had been stronger for brain tumors," says David Savitz, an epidemiologist at the University of North Carolina.

The second study looked at 1,632 men in central Sweden, 511 of whom had contracted leukemia or brain tumors. Adjusting for exposures to various other environmental factors, the researchers concluded that, compared with the other men, more of the leukemia patients had occupational exposures to electromagnetic radiation.

"I think it will take a long time before we have final proof," Maria Feychting says. But even if the link holds up, she notes, people should not panic: "The risk for leukemia is very small -- 1 out of 20,000 children a year." Reacting too hastily to scientific findings can in itself be hazardous to one's health. Witness the realization that more people may be exposed to asbestos during its removal than if it is merely encased. As for electromagnetic radiation, prudence would suggest that the ideal location for a new day-care center is not next to city power lines. For families, it might make more sense simply to shift a child's bed away from a power line rather than move the house.

With reporting by Ulla Plon/Copenhagen