(FORTUNE Magazine) – IN NOVEMBER, 65% of the voters in Washington's Whatcom County approved a measure limiting construction of new high-voltage power lines. Last summer a citizens' group in Monmouth County, New Jersey, forced a utility to table plans for an electric transmission line. School boards in Florida and elsewhere with buildings near power lines are closing off parts of their grounds to protect their kids. What's behind all this? A rising national fear of possible risks to health from the magnetic fields generated by electric currents. It's a concern that has also renewed debate over the safety of the ubiquitous video display terminal (VDT). Other corporations besides utilities are listening up: IBM recently told FORTUNE that it will reduce the strength of extremely low frequency (ELF) fields in all new-model VDTs after the end of 1991. The issue could also hurt property values near power lines and sidetrack high-tech advances like magnetic levitation trains that create strong fields. A growing body of evidence suggests that ELF electromagnetic fields -- those with very long wavelengths -- are worth worrying about, though utilities and computer makers insist there is no proof that they do harm. (IBM executives say they believe that all their existing terminals are safe and that the company is merely responding to customers' wishes.) But epidemiologists, who study the incidence of disease, are finding more and more situations where people exposed to ELF fields apparently have elevated rates of cancer, especially brain cancer and leukemia. In several studies, higher rates seem to be associated with exposure levels not greatly different from those near some VDTs or many types of power lines. ELF fields have not been proved to cause cancer. Epidemiology only identifies associations between exposure and disease -- not cause and effect. An apparent correlation may be mere coincidence, the result of something else entirely. While laboratory work has shown that ELF fields can have biological effects, no conclusive evidence exists that those effects are dangerous. But despite enormous gaps and uncertainties in the data, even utility industry spokesmen like Dr. Leonard Sagan call the evidence ''inconclusive but suggestive.'' Sagan, a physician, heads electromagnetic field studies for the Electric Power Research Institute (EPRI), a group funded by utilities. An overview of ELF fields prepared for the congressional Office of Technology Assessment last year concluded, ''The emerging evidence no longer allows one to categorically assert that there are no risks.'' Says Imre Gyuk, who supervises the Department of Energy's modest research effort into ELF fields: ''There is clearly cause for concern but not for alarm.'' Some go further. Dr. David Carpenter, dean of the school of public health at the State University of New York's Albany campus, was once a skeptic. Now he says, ''This is really harming people. In my judgment the present state of affairs is like the correlation between smoking and lung cancer 30 years ago.'' The causal relationship between smoking and cancer was clearly demonstrated only with extensive cellular and animal studies of the kind that have yet to be carried out with ELF fields. Those fields are created by AC current as it alternates back and forth 60 times a second in the circuits that carry it. (Direct current, produced by batteries, sets up negligible fields.) The more current flowing through a wire, the stronger the magnetic field. ELF fields are so named because they fall at the low end of the electromagnetic spectrum. They carry much less energy than X-rays or even microwaves and cannot break chemical bonds or heat living tissue. UNTIL RECENTLY physicists assumed that the infinitesimal amounts of energy in ELF fields couldn't affect the human body. Yet for years some orthopedic surgeons have used pulsed ELF fields to speed the healing of broken bones, though scientists do not fully understand why that works. They still believe that the fields are probably too weak to initiate cancer, but they are starting to examine the possibility that fields -- especially their magnetic component -- may encourage the growth of cancers actually caused by something else entirely. Are you being zapped? Even the most alarmist experts think that if there is any danger, it most likely comes from chronic exposure to ELF fields above levels routinely found almost anywhere (see box). Only measurements in your home or workplace will reveal your exposure, but you probably need not worry unless a high-current power line passes very near your home or your child's school, or you work in a room full of closely spaced VDTs -- or you're a telephone or power company lineman. Paul Brodeur, a journalist whose books and articles have played a major role in bringing this issue to public attention, advocates interim protective measures like rewiring, rerouting, or burying power lines near schools and beginning a national program to measure intensities in homes around the country.

While many household appliances like hair dryers and electric can openers emit strong fields over a few inches, people use these devices only briefly and the fields drop off rapidly with distance. However, sleeping under an electric blanket is probably imprudent -- at least if you're pregnant. One study of 474 children in Denver, published in May, found that those whose mothers used the blankets during pregnancy were 2.5 times more likely to contract brain tumors than children whose mothers did not. While epidemiologists consider the more than doubled risk in this study significant, the absolute overall risk that a child will get cancer because its mother used an electric blanket remains minuscule. (Some manufacturers have recently introduced blankets with reduced fields.) The risk from ELF fields appears much lower than from many already known carcinogens. For children living within 130 feet of high-current power lines, the most worrisome studies put the risk of cancer at two to three times that for other children. The risk of lung cancer is 20 times greater for chain smokers than for the public at large. Epidemiologists have conducted 50 to 60 studies of human exposure to ELF fields and cancer. The majority have found at least some increased risk, albeit usually small. Nancy Wertheimer was the first to identify the possible problem in a study published in 1979. She examined the homes of 344 children in Denver who died of cancer before age 19 from 1950 to 1973 and compared them with the homes of 344 other children of similar ages from similar neighborhoods. Wertheimer noticed power distribution lines near the homes of a number of cancer victims. She classified those homes as high current or low current, depending on the way power was distributed in the immediate vicinity. She found that children in the high-current houses were two to three times as likely as the others to die of lymphomas, nervous system tumors, or leukemia. Expecting to discredit Wertheimer's results, a group set up by the New York State Public Utilities Commission hired another epidemiologist, David Savitz, to conduct a similar but more rigorous study. His report, published in 1988, in fact confirmed Wertheimer's results, although the risks were slightly lower. The background level of ELF magnetic fields in most homes and offices is roughly one milligauss (mG). He reported a doubling of risk for leukemia and a 50% increase in all cancers among children who lived in homes where ELF fields, presumably from the nearby distribution wires, measured above 2 mG. He found that level in about 20% of the homes in the study. His results were what convinced David Carpenter of SUNY Albany. He oversaw the group that commissioned Savitz's research, and he fully expected a negative result. Says Carpenter: ''The Savitz study changed my entire view of the field, and it has enormous implications.'' Based on those results, he estimates that up to 30% of all childhood cancers may be attributable to ELF fields. ''That's conservative,'' he adds. Newer data suggest that the hazards of working near ELF fields could be even greater. A 1988 study found that utility workers in East Texas were 13 times more likely to develop brain cancer than the general public. The researchers compared the occupations of 202 men who died from brain tumors in 40 East Texas counties between 1969 and 1978 with a control group. The study lumped all utility workers together and did not classify them according to their actual exposure to ELF fields. Epidemiologists from the University of Southern California published a study this year showing that men with occupations like electrician and electrical engineer are ten times more likely to contract astrocytoma, a type of brain tumor. They interviewed virtually all Los Angeles men diagnosed with the two , most common types of primary brain tumors from 1980 to 1984 -- 272 in all. They found that electrical workers with ten years on the job had a higher risk of astrocytoma than those with only five years' experience. But they noted no increased risk for several other types of brain tumors.

Perhaps the most disturbing occupational study was done by epidemiologists from Johns Hopkins University. In late 1989 they said they found a sevenfold increase in leukemia risk among young New York Telephone Co. cable splicers, who work in close proximity to electric power lines. A team led by Genevieve Matanoski evaluated cancers among 51,000 linemen who worked at the company between 1976 and 1980. The splicers were exposed to surprisingly weak fields -- only 4.3 mG. Early data from an even larger nationwide study of linemen the team had conducted showed no such strong pattern. The New York work has not been completed or published, partly for lack of funds. Representatives of the electric power industry do not dismiss these results. Says Sagan of EPRI: ''In my mind the occupational data support the childhood data, and that is what makes it necessary for us to take the whole thing seriously.'' But, he cautions, ''to say an activity is associated with cancer doesn't prove anything about what the electromagnetic fields might be doing.'' Sagan, who will supervise $6 million in EPRI medical research on the subject in 1991, admits he is ''befuddled.'' At the federal Environmental Protection Agency, Martin Halper doesn't feel so confused. He is the director of the analysis and support division in the Office of Radiation Programs and spent many years in the Office of Toxic Substances. Says he: ''In all my years of looking at chemicals, I have never seen a set of epidemiological studies that remotely approached the weight of evidence that we're seeing with ELF electromagnetic fields. Clearly there is something here.'' Sagan and others suggest that other so-called confounding factors could be causing the cancers in the epidemiological studies. Carcinogenic solvents, for example, might be acting on electricians, or PCBs on utility workers, or fumes from traffic sickening children who live near power lines. Replies Halper: ''If people want to be naysayers, they'll never talk about the 60-some studies together. They'll pick out each one and fault it individually. But when you have this number of studies, it's improbable, if not impossible, that a confounding factorcould have invalidated all of them.'' So much for correlations, but what about causes? Cell biologists and others trying to figure out how fields might induce cancer have run up against layers of mysteries. Notes the Office of Technology Assessment report: ''ELF fields appear to be an agent to which there is no known analogue.'' While scientists have shown that fields can have biological effects, they can find no clear relation of dose to response. A number of experiments with ELF fields have found so-called ''windows of effect,'' ranges of frequency or intensity where an effect occurs -- but at both lower and higher frequencies or intensities, it seems to disappear. AS IF THE ''windows'' problem weren't enough, the relation between exposure and the direction and intensity of the earth's static magnetic field also seems significant. The earth's field can vary tremendously even within a single room. Another rapidly developing area of research is intermittency: Some data show that fields have a greater biological effect when exposure is not continuous but instead switches on and off, as in an electric blanket adjusting its temperature during the night. Other factors that may affect risk include duration of exposure, time of day, age, the shape of the waves in the field, the angle of the field, and the subsidiary frequencies that accompany a main frequency. Says Carl Blackman, an EPA research biophysicist whose pioneering work helped identify some of these variables: ''It gets so complex, you just want to throw up your hands.'' Even so, Blackman and others are making discoveries that may be of tremendous significance. Much of their research points to the importance of the cell membrane, the barrier that separates the cell from the outside world. Says Dr. Ross Adey, a neurologist whose work has fundamentally altered the ELF debate: ''We have found that the cell membrane is indeed a very powerful amplifier of the energy in these very weak fields. It's a physical, not chemical, process.'' Adey speculates that disruption of interaction between cells by ELF fields may be what contributes to some cancers. One possibly related effect, well established in experiments with animals: a reduction in the brain's production of melatonin, a hormone that seems to inhibit growth of some tumors. Until recently it was not widely known that VDTs, too, could be a source of exposure to ELF fields. In fact the ELF fields emitted by a VDT are produced not only by the flow of electric current but also by the electron gun that creates the image on the screen. The 40 million VDTs in the U.S. represent a significant source of exposure. Color monitors generally emit higher fields than black and white ones do. The idea that VDT use might be dangerous is not new. Clusters of miscarriages and other pregnancy problems have been reported for years among women using VDTs. In the mid-1980s, several lab experiments showed increased rates of malformation in mouse fetuses exposed to higher-frequency fields also associated with VDTs. Then a 1988 epidemiological study of a group of 1,583 California women found that clerical workers who used terminals more than 20 hours a week had a 2.4 times greater risk of miscarriage than women who didn't use the machines. The researchers, who worked for a big health maintenance organization in Northern California, conceded the possibility that other factors such as job-related stress might account for the results. Soon thereafter, IBM helped fund a large-scale investigation in Toronto of the effects of the higher-frequency fields on pregnant mice. The results, released in late 1989, assuaged many fears. Scientists found no statistically significant malformations. Other epidemiologists reported no increase in miscarriages among VDT operators. Then, last summer, MacWorld magazine pubished the results of tests showing that some color monitors emit ELF fields of over 4 mG one foot in front of the screen and at higher levels at the sides and back. In an accompanying article, Paul Brodeur drew attention to disturbing research about ELF fields, including the Johns Hopkins study of New York Telephone workers. The effects of the MacWorld measurements have been dramatic. Apple Computer announced it will sponsor research to help assess risks. The Food and Drug Administration began testing field levels near VDTs. Besides IBM, some small VDT makers, including Sigma Systems and Tandberg Data, said they would soon sell monitors with reduced ELF emissions. Though many think her data suggest danger for VDT users, Genevieve Matanoski, who conducted the Johns Hopkins study, still works with a personal computer and thinks it's too early to start worrying. ''We're a long way from saying that VDT-type fields can be a health problem,'' she says. ''We still don't know what kinds of exposures really matter.'' No studies have explored whether any association exists between VDTs and cancer. COMPUTER COMPANIES can modify new VDTs at relatively little cost, but rising / public fears could force utilities to spend billions redesigning their distribution systems. Already two states, Florida and New York, have adopted a 200 mG exposure maximum at the edge of power-line rights of way. While that level poses little obstacle for utilities, Florida's Hillsborough County is fighting the state to force it lower. One study calculated that to bring transmission line fields down to a maximum of 100 mG at the edge of rights of way would cost $5 billion in Florida alone. But with all the uncertainties, science cannot now say, ''Here you are in danger, and here you are not,'' so money spent on reducing exposure levels might be wasted. Says Louis Slesin, publisher of Microwave News, the most authoritative journal on ELF fields and health: ''I'm sympathetic to the power companies not wanting to act now. We really don't know which variable we'd most want to control.'' He thinks money would be better spent on research into the basic mechanisms that cause biological effects. However, Slesin urges utilities to reduce fields wherever it is not enormously expensive. New power- line configurations can cut emissions up to 50%. Not for at least five and maybe ten years will scientists know enough to guide policy effectively for regulators and business. That's no consolation to the school board of Florida's Palm Beach County. In 1988 parents of children attending Sandpiper Shores Elementary School in Boca Raton sued to have the school closed because the parents believed it was dangerously close to power lines. The case is still not resolved, and the board has spent about $175,000 so far to defend itself. Some school systems in situations like that in Boca Raton have turned around and sued power companies. In 1987 a Houston school district forced a utility to remove a transmission line that ran within 300 feet of three schools. Cost: $8 million. Good old market considerations may eventually create the strongest pressures to resolve the scientific uncertainty. Says Slesin of Microwave News: ''The battleground is going to be property values.'' David Lewis, a real estate consultant in Houston, estimates that houses near transmission lines there have dropped about 25% in value over the past 18 months. He says living near power lines is starting to seem as undesirable to buyers as living near a freeway. In Manhattan, a real estate risk advisory service has begun offering investors information about the location of electrical substations so they can avoid nearby property. ; Given the uncertainty about what is safe, managers ought to keep themselves and their employees informed. At this point workplace changes need not be dramatic. Even Dr. Robert Becker, a pioneer in research into the biological effects of ELF fields who has spoken out for years about possible dangers, wouldn't take draconian steps. Says he: ''If I were running a business where women operated PCs, I would at least have the ELF emissions measured. I'd make sure workers sat far enough back from the machines so they were below the 3 mG level. If a woman became pregnant, I'd take her off the machine for the duration of her pregnancy. Further than that I would not go.''