The Buzz over Transmission Lines
September 8, 2006
The discussion over whether to place transmission and distribution lines underground is largely about costs and what route the wires will take. But activists are also concerned about electromagnetic fields, which some studies say increase the threat of childhood leukemia and adult brain cancer, as well as cause degeneration in nerve cells connected to the brain and spinal cord.
The evidence is inconclusive but researchers have left open the possibility that a connection does exist between electromagnetic fields (EMFs) that are produced by power lines and some illnesses. The apparent solution is to run lines far away from schools and hospitals as well as to consider deeper undergrounding and taller poles. Nevertheless, the concerns raised could not have come at a more precarious time, when the nation has placed an emphasis on electric reliability.
EMFs are invisible lines of force that surround any wire or conductor that carries electricity. That includes overhead and underground power distribution lines, interior structural wiring, and many common electrical devices. EMFs related to transmission lines have grabbed the public's attention, although the EMFs generated from wiring and appliances within the home can exceed those generated from transmission lines. EMFs get weaker as the distance increases from their source, which has been used to support the argument that such lines must be re-routed away from sensitive locations.
A few dozen studies have looked at the possible link between proximity to power lines and various types of childhood cancer. Some of the examinations do show a tie to cancer and particularly leukemia. The first came in 1979 by two Denver-based doctors who found that children who died from cancer were two to three times more likely to have lived within 131 feet of a power line and that they were therefore exposed to EMFs.
That was generally confirmed by a second Denver study done in 1988 and again by a third one performed in Los Angeles in 1991. Swedish, Mexican and Danish researchers came to the same conclusion, all in 1992 and 1993. Japanese researchers found in 2002 that children exposed to excessive EMFs were twice as likely to suffer from leukemia.
But those studies are contradicted by others that include a 3-year analysis that examined a 20-year time period by the National Research Council. It took place in the mid 1990s and reviewed 500 cases, finding "no conclusive and consistent evidence" that EMFs harm people. In 1997, the New England Journal of Medicine published the results of an eight-year examination, which found "no evidence" of EMFs and childhood cancer.
"Research has not shown in any convincing way that electromagnetic fields common in homes can cause health problems, and extensive laboratory tests have not shown that EMFs can damage the cell in a way that is harmful to human health," says Charles Stevens, chairman of the National Research Council committee looking into the issue and a neurobiologist, in a previously published report.
Fear of EMFs was at a peak in the early 1990s. That was when lawyers started filing lawsuits on the matter and when a well-publicized case in Italy broke. That's when three top executives at utility ENEL were charged with manslaughter for managing power lines that allegedly caused threatening diseases. Hundreds of utility projects have been challenged based on the EMF argument while at least three suits have been filed in U.S. federal court over the matter.
EMFs are found in all households that use electricity, either as a result of electrical appliances or electrical circuits. EMFs are calculated in teslas and can be measured by a hand-held device. Homes with an average of 0.4 microteslas are thought by some experts to pose a risk, although most appliances in most homes add up to much less. North American households average 0.09 microteslas while those on continental Europe average less, mainly because electricity is supplied in North America at 60 hertz -- a bigger producer of EMFs than Europe's 50 hertz system.
So, the danger comes -- if at all -- by having children and some adults exposed to more than 0.4 microteslas. About 5 percent of all homes in the United States are estimated to carry EMF levels above that amount. Many experts conclude that it would take significantly higher EMF levels in the home to do any damage - and certainly ones that are much greater than those studies that concluded there is a link between EMFs and some forms of cancer.
Communities' concerns are real. In San Francisco, some citizens demanded that a 230 kilovolt power line be re-routed away from homes, schools and commercial enterprises. The 27-mile line was therefore placed underground. Meanwhile, Southern California Edison's customers in Mission Viejo are discussing EMFs with regard to a proposed power line to be built there. And, so are customers of NSTAR in Boston, who demanded that a 345 kilovolt underground line be diverted.
Fear over EMFs is still prevalent. Researchers commissioned by the California Public Utilities Commission said in 2002 that EMFs enhance the likelihood of childhood leukemia and adult brain cancer. One of the studies that California researchers examined occurred in 1994 and involved 223,000 men who worked at Ontario Hydro, Hydro-Quebec and Electricite de France. The investigation looked at cancer rates at the electric utilities between 1970 and 1989 and discovered that there were 4,151 cases. Of those, 140 were leukemia and 108 were brain tumors.
Those workers who developed leukemia were exposed to three times as much EMFs as others operating in less "hazardous" surroundings, the report says. Similarly, those who developed brain cancer were subjected to EMF levels at 12-times the rate of those working in "safer" areas. Nevertheless, the findings were considered "inconclusive" because of the small number of cases.
"All it's going to take is one or two good hits and the sharks will start circling," says Tom Ward, a Baltimore attorney who is suing Northeast Utilities Co. and its Connecticut Light & Power Co. unit over an alleged EMF cancer, in a previously published news report.
Despite diverse opinions on the subject, various stakeholders are coming together to ease concerns. Some solutions involve running power lines using taller poles, particularly when they would be located close to population centers or along major highways. Other times, the lines could be placed underground, although this would be a far more expensive option and one that would be reflected in customers' rates. The Swedish government, for instance, hasn't allowed transmission lines near schools since 1993 while the state of Tennessee requires that such power lines be at least 400 meters away from learning institutions.
Researchers have not been able to rule out a link between EMFs and proximity to power lines. But, the reality is that the dangers over contracting cancer as a result of EMFs are highly improbable unless there is prolonged and high exposure to that type of radiofrequency.