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ELF: the current controversy.

ELF: The Current Controversy

In 1979, Nancy Wertheimer of the Universityof Colorado Medical Center and physicist Ed Leeper suggested a link between living near high-current electric power lines and an increased risk of cancer, particularly childhood leukemia. The key, said the Boulder scientists, might be the extremely low-frequency (ELF) magnetic fields produced as electricity flows through wires.

Since then, the role of ELF fields incancer has been debated among those studying electromagnetic fields, with the power industry challenging the existence of such a link. A number of studies, including a recent one that has replicated the 1979 findings, are now sparking more controversy. Some of the studies have also linked ELF fields to tumor growth and electrically heated beds to spontaneous abortions.

Unlike some potential environmentalhazards, ELF magnetic fields are virtually everywhere, making avoidance difficult. The flow of electric current through power lines creates magnetic fields, which easily penetrate walls of buildings and the body. These low-frequency fields localize near plumbing in houses and under streets, and their strength appears to be related to the types of wiring configurations nearby. They are, for example, found around power stations, welding equipment, subways and movie projectors.

Wertheimer and Leeper found the overalldeath rate for certain cancers among children living in homes with high-current wiring configurations (with their higher radiation of ELF fields) to be twice that expected for children in general (SN: 4/21/79, p.263), but there was no proof that ELF fields were the cause. Nonetheless, such early studies generated interest among epidemiologists and power utility officials, and illuminated the need for replicate studies.

Last November, epidemiologist DavidSavitz of the University of North Carolina in Chapel Hill announced research results that support the Wertheimer-Leeper findings. He reported his findings at a Denver meeting on the health effects of power lines, organized by the Electric Power Research Institute (EPRI) of Palo Alto, Calif., and the U.S. Department of Energy.

Savitz, along with Frank Barnes andHoward Wachtel of the University of Colorado, found a fivefold increase in childhood cancer--particularly leukemia --in those homes near the highest level of ELF fields. Homes in this group were located within 15 meters of primary wires designed to carry very high electric currents, or within 7.5 meters of primary wires that carry lower currents. (Primary wires carry electricity from the power substation to the neighborhood transformer.) The data, currently being prepared for publication, were based on current configurations similar to those in the 1979 study, lending credibility, say the researchers, to the ELF-cancer theory.

Savitz and his colleagues evaluatedapproximately 500 homes in Denver in 1984-85; about half of them contained cases of childhood cancer as reported in the state's tumor registry. While some of the researchers classified both cancer and control homes on the basis of their proximity to different types of residential power lines, another group independently interviewed test subjects and controls.

Savitz and Barnes told SCIENCE NEWSthat certain aspects of their study addressed some of the criticisms aimed at the earlier work. For instance, the researchers coding the homes' current configurations did not know which households had cancer cases; this removed certain biases that may have affected the first study. Also, Savitz and his co-workers concluded that the Wertheimer-Leeper wire configuration schemes--which rated houses on their proximity to different types of wiring--was a better parameter for evaluating long-term ELF field exposure than on-the-spot measurements inside the home.

There remain, however, problems thathave no ready-made solutions. As Savitz points out, the number of households evaluated represents a "limited amount of data': Only about 3 percent of the Denver homes studied were classified at the highest exposure level. He points out that magnetic fields, unlike air and noise pollution, are not noticed by the human senses, making detection more complicated. Perhaps most significant is the problem--often faced in epidemiologic studies--that proving a causal relationship is difficult when researchers must rely on past records and events.

Wertheimer and Leeper's latestwork is another example of the suspicious-but-is-it-the-cause dilemma. In a 1986 issue of BIO-ELECTROMAGNETICS (Vol. 7, No. 1), they report that users of electrically heated beds--which can give off ELF fields--are more likely to have miscarriages and longer gestation periods during seasons when heated waterbeds or electric blankets are used. About 1,700 Denver births over the 1976-82 period were studied, along with reported abortions, most of which were spontaneous rather than induced.

Among users, the median gestationperiod for midwinter conceptions was about one week longer than that for conceptions during July and August. For electric blanket users, 75 percent of the miscarriages occurred in September through January; for waterbed users, 61 percent; and for nonusers, 44 percent. No such seasonal variations were seen among those who did not use heated waterbeds or electric blankets.

Wertheimer and Leeper currently areevaluating different types of home heating systems, looking for possible heat-related causes of their results. (Other studies have shown heat harms sperm.) Preliminary data indicate heat itself is not the cause, Wertheimer told SCIENCE NEWS.

"It would be very easy to design awaterbed that does not create a field,' she says. Wertheimer believes that, for the individual, exposure to ELF fields does not pose a very big risk, but that from a public health viewpoint there may be need to worry. "The early warning is out,' she says, "which is what the epidemiologist is supposed to do.'

The heated-bed study also providessome evidence that ELF fields may be related to congenital birth defects in humans, says Wertheimer. Laboratory experiments by other researchers indicate that ELF fields can affect fetal development in swine, chickens and rabbits. Whether magnetic fields actually affect cell development is a controversial subject. In order to assess possible effects, research groups are working with ELF fields in such experimental systems as neuronal activity in rat brains and chromosome breakage in human blood cells.

One study attracting attention is that ofJerry Phillips, director of biochemical research at the Cancer Therapy and Research Center in San Antonio, Tex. Phillips told SCIENCE NEWS he has shown in recent experiments that exposure to ELF fields causes an abnormal increase in the growth of cancer cells. Those cells, he says, also show a 60 to 70 percent greater resistance to disruption by the body's naturally occurring killer cells.

The changes appear to be permanent,passed from one generation of cancer cells to the next. They occurred in cells descending from those exposed to ELF fields more than five months prior to experiments, according to Phillips's paper in the November 1986 IMMUNOLOGY LETTERS.

Such results could explain the abnormallyhigh cancer rates reported among those exposed to magnetic fields. But the consensus of researchers, including Phillips, is that the tumor cell experiments need to be repeated by other laboratories to validate the results. To that end, a group at the University of Maryland School of Medicine in Baltimore began similar experiments last year.

The power industry's reaction to thelatest results appears to be one of cautious concern. Leonard Sagan, manager of the Radiation Sciences Program at EPRI, calls the work by Wertheimer, Savitz and others "interesting.' He told SCIENCE NEWS that the different current configurations "mean something.' But, he says, rather than being causative agents, they may instead indicate other potential cancer causes, such as population density, socioeconomic class or local road traffic.

Commenting on Wertheimer andLeeper's bed study, Sagan agrees that "the use of electric blankets deserves some attention, because it is an important source of magnetic radiation to the public.'

EPRI, as the power industry's researcharm, evidently does not plan to sit idle while others raise suspicions. According to Sagan, EPRI spends $2 million annually to study ELF field effects, and that figure will "significantly increase.' One study now being funded is at the School of Public Health at Johns Hopkins University in Baltimore, where researchers are looking at cancer incidence among telephone company employees (phone lines are strung along electrical lines).

Industry concern over whether a linkbetween ELF and health problems actually exists also can be seen in reports from the November/December 1986 MICROWAVE NEWS:

EPRI has funded a two-year, $350,000epidemiologic study at the University of Southern California in Los Angeles to test the Wertheimer-Leeper and Savitz findings. It will include additional information on parent occupation and chemical exposure.

The Texas Supreme Court has refusedto allow the Houston Lighting & Power Co. to activate a power line built across school property. A 1985 lower court ruling awarding the school district $25 million in punitive damages is still under appeal.

Last month, representatives of the 20utilities that form the Western Energy Supply and Transmission Associates were meeting to discuss priorities for future bioeffects research and its funding.

In Canada, representatives fromunions, utilities, academia and government are forming a group to address priorities in ELF exposure research.

Much of the research is directed towardthose who work in magnetic fields. More studies are suggesting that such occupations carry the increased risk of developing cancers (SN: 11/10/84, p.292). Response to the studies is flowing from several sectors, including Massachusetts Institute of Technology, which will offer a practical course on the hazards and measurement of nonionizing radiation in August.

All the data, statistical analyses andconfounding factors are adding their weight to the hefty problem of deciding which ELF effects should concern the public. Clay Easterly of Oak Ridge (Tenn.) National Laboratory organized a workshop immediately following the Denver power line meeting to review the latest ELF results, but he refuses to talk publicly about a consensus statement being prepared using participants' comments.

"A lot of people had been skeptical for along, long time [about the ELF-cancer link],' he told SCIENCE NEWS. "But now scientists are recognizing the significance of this research.' He says the Oak Ridge lab will recommend a "multicentered approach' to ELF field research.

"Many things need to be sorted out,'says Sagan, adding that the public so far has "no reason for taking any protective action. We wouldn't know how to do that, even if there were a need.'

Other researchers contacted by SCIENCENEWS, even those with attention-getting data, agree. "There is no solid evidence that you should be worried, even if you live under the power line,' says Savitz. "The bottom line . . . is that the evidence does fall short of implicating these fields as a health hazard.' But he adds, "The other side is that there are these suspicions raised that haven't been resolved. So from a public health perspective, there is a reason for concern.'

The debate on ELF fields and theirbiological effects is increasingly sensitive as a political issue, according to Wertheimer and others. As Savitz says, "There is certainly a spectrum of views on this--to put it mildly.'

While recognizing the potential forscare tactics and public panic, researchers in the field widely believe that, although there is no absolute proof that ELF fields cause conditions like spontaneous abortion and childhood cancer, there is sufficient reason to take a closer look.

Photo: Data gathered by Denver researcherssuggest that gestation periods are generally longer for infants of users of electric blankets and electrically heated waterbeds, if conception occurs in seasons with increased use of heated beds (above). For users of electrically heated beds, excess miscarriages apparently occur during relatively colder months (right).
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Title Annotation:extreme low-frequency magnetic fields
Author:Edwards, Diane D.
Publication:Science News
Date:Feb 14, 1987
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