NO SIGHT in modern life seems more familiar or benign than the electric power line. It runs along roads, through valleys, over mountains, webbing the nation in a technology that has become synonymous with convenience and comfort.

So it came as no small jolt when, in 1979, two University of Colorado researchers completed a low-budget study that threatened to stand a big-bucks industry on its ear.

Nancy Wertheimer and Ed Leeper found that children in the Denver area who died of leukemia and other cancers lived "unduly often near electric lines carrying high currents." It was the first epidemiological study to suggest a link between the electromagnetic fields surrounding power lines and childhood cancer.

Critics, chief among them the electric power industry, complained that the study was flawed. (For one thing, it was done so cheaply that the researchers had to estimate EM fields by the size and number of power lines near subjects' homes.) But the controversy it ignited wouldn't go away.

Eight years later, there's a second study, also conducted in Denver, by a team of researchers whose mission was to correct the deficiencies of the Wertheimer study and, with any luck, lay the controversy to rest.

No such luck.

The new study, conducted by David A. Savitz of the University of North Carolina and made public this summer, found that children in homes exposed to higher EM fields from power lines were 1.7 times more likely to develop cancer than children in homes with lower fields. For leukemias, lymphomas and soft-tissue tumors, the risk was even more pronounced.

In recent testimony before a House subcommittee, Savitz called the results "suggestive" rather than conclusive. But if further studies are conducted and bear out the Denver results, he said, it could mean that "a sizable proportion of childhood cancers" are related to electromagnetic fields from power lines.

Whispering Cells

The Savitz study has become the latest scientific entry in a high-stakes debate over the health effects of EM fields -- not just from the ubiquitous power lines that are the warp and weft of modern society, but from an expanding array of communications and consumer devices.

But this time the study coincides with new understanding about the atomic behavior of cells, including evidence that they can detect, amplify and respond to the most minute EM stimuli.

In recent years, biomedical researchers have demonstrated that low-frequency EM fields can disrupt the body's natural immune system, modify the production of hormones and help promote the growth of tumors. Some leading researchers now believe that physical events, rather than chemical ones, govern the most basic biological functions -- through electrical interactions so elegant and complex that the classical laws of physics may be useless in describing them.

The concept of cells communicating in a subtle flow of energy -- or "whispering together" as researchers term it -- carries some troubling overtones. If, as laboratory studies suggest, cells can detect EM fields as small as a ten-millionth of a volt per inch, what might be their response to fields as high as a ten-thousandth of a volt per inch (the tissue field induced by standing directly beneath a high-voltage power line) or even one volt per inch (the tissue field induced by holding a cellular telephone next to the head)?

There is still no conclusive evidence that the EM fields to which millions of Americans are exposed are a health hazard, but the unfolding knowledge about cellular communications has shaken the long-held view that nonionizing radiation, by definition, cannot produce biological effects.

"This attitude can only be described as wearing blinders in the face of available scientific evidence, with the same apparent lack of good sense as the executives of the tobacco industry who never admit to even the slightest danger in smoking," says W. Ross Adey, a leading researcher in the field and associate chief of research and development at the Veterans Administration Medical Center in Loma Linda, Calif.

"Even without supporting evidence from epidemiological findings, results of animal, tissue and cellular research strongly suggest tissue interactions with environmental EM fields that would initiate pathological responses, including cancer promotion," says Adey, who appeared with Savitz at a hearing last month before a House Interior subcommittee.

The Danger Zone

The controversy has been separated conveniently for years by the point on the EM spectrum that is occupied by visible light -- a frequency of roughly 500 trillion cycles a second. {See illustration.}

Frequency refers to the number of EM waves, or "cycles," that pass a point in one second. Low-frequency waves are relatively long and gentle, like the swells of a placid ocean. Moving up the spectrum, wavelengths grow progressively shorter and their energy levels increase.

Above the point of visible light, EM waves pack enough energy to do physically alter the atoms they strike, changing them into charged particles called ions. Hence the term "ionizing radiation," which applies to ultraviolet rays, X rays, gamma rays and so on up to the cosmic rays of outer space.

All are capable of destroying or damaging components of living cells, especially DNA stored in the nucleus. The higher such waves are on the frequency spectrum, the greater their energy level and ability to cause damage.

But below the point of visible light, EM waves are "nonionizing," meaning that they do not possess enough energy to charge atoms. Engineers and many scientists have long accepted the view that nonionizing radiation poses no biological threat other than by heating -- the "thermal" effect exploited by microwave ovens, which operate on frequencies of more than two billion cycles per second.

They further assumed that, if ionizing radiation becomes progressively more dangerous as frequencies increase, then nonionizing radiation must become less dangerous as frequencies decrease. By that reasoning, high-voltage electric power lines, with EM fields of a mere 60 Hertz (cycles per second), would appear to be imminently safe.

Yet most of the epidemiological research on nonionizing radiation has found a weak association with cancer -- too tenuous to be conclusive but too consistent to be ignored. Leukemias and lymphomas are more prevalent among electricians, television and radio repairmen, film projectionists and the like. The risk of astrocytoma (a form of brain tumor) is higher among electronics designers, manufacturers and installers.

Similarly, numerous animal studies have demonstrated neurological or reproductive effects from low-frequency electromagnetic fields. Chick embryos show a higher rate of abnormalities when exposed to low-frequency fields; mice suffer a higher rate of abortion and abnormal fetuses when exposed to slightly higher frequencies, approximating those emitted by video display termimals.

"I must say I was skeptical," says Louis Slesin, editor of the New York-based Microwave News, a newsletter that closely follows research on nonionizing radiation. "The fields implicated by the Savitz and Wertheimer studies are smaller than the Earth's magnetic field. The field from a VDT is so small. People don't understand the mechanism, how these miniscule fields can have an impact."

Even more puzzling was the fact that the studies often failed to show the positive correlation between dosage and damage that scientists have come to expect in analyzing health hazards.

For example, smoking two packs of cigarettes a day is riskier than smoking one. Similarly, if exposure to a weak EM field results in a slightly elevated risk of birth defects or cancer, researchers would expect exposure to a stronger EM field to produce an even higher risk. Yet chick embryos showed severe brain development damage at certain low frequencies and no damage at higher ones. Because of such inconsistencies, critics have often dismissed the results as either flawed, biased or unsubstantiated.

But the inconsistency may be inherent in the organisms. One theory is that biological effects are not dose-dependent but occur in what Adey calls "windows," dependent on EM frequency, field strength and length of exposure.

Adey developed the theory after he and a colleage conducted a series of experiments showing that certain low-frequency fields activated the flow of calcium from cells. At slightly higher frequencies, however, the flow of calcium subsided. At still higher frequencies, the flow resumed.

The results were significant because calcium plays a key role in many cellular reactions, including the action of lymphocytes, a type of white cell that is the body's main defense against "invaders."

In separate experiments, scientists at the Cancer Therapy and Research Center in San Antonio discovered that human cancer cells exposed to 60-Hz fields (the frequency of a high-voltage power line) grew as much as 24 times as fast as unexposed cells and showed "greatly increased resistance to destruction by the cells of the body's defense system."

Jerry L. Phillips, biomedical research director at the San Antonio center, says the experiment suggests that certain EM fields -- while not carcinogenic in themselves -- might enourage the development of cancer by suppressing the body's defense system.

Researchers also have found that weak microwave fields can enhance the action of phorbol esters, a chemical cancer promoter often used in laboratory studies because of its predictable method of action. In the absence of phorbol esters, the microwave field had no effect. Those results, researchers say, suggest that EM fields may work in tandem with environmental pollutants to promote cancer.

Taken together, the laboratory studies suggest mechanisms to explore how exposure to EM fields can result in an increased incidence of human cancers. But what fields, and at what levels, and for how long?

The Electromagnetic Deluge

Scientists are the first to acknowledge that they don't have the answers.Some contend, however, that enough is known now to start minimizing public exposure, at least to the long-term, intermittent EM fields that have aroused the most health concerns.

At the moment, there are no federal standards for exposure to nonionizing radiation, a situation that has resulted in some interesting anomalies.

The military, for example, limits microwave workers to exposures of no more than 10 milliwatts per square centimeter (a field of about 130 volts per meter) in six minutes. The average home microwave oven emits a field half that strong, meaning that a homeowner who watches the stew cook for more than 12 minutes has exceeded the military standard.

Most scientists discount the possibility of health hazards from such household appliances because EM fields drop off sharply with distance from the appliance and exposures tend to be brief. The possible exceptions are electric blankets and waterbed heaters, which can expose the body to fields similar to that of a high-voltage power line for eight hours at a time.

But in an age of burgeoning military and commercial use of the EM spectrum, others are not so sanguine. "Electromagnetic pollution is far greater than any other pollution man has caused," says former biomedical researcher Robert O. Becker.

Becker, now retired in upstate New York, raised questions more than a decade ago about an extra-low frequency submarine communication system that the Navy was seeking to build in Wisconsin. After the ensuing controversy, the project was scaled back but not shelved. It is now nearing completion. "The usage is continually expanding," he says. "We're headed for real trouble."

Adds Slesin: "There are 300,000 miles of power lines in the United States, and we're moving toward the time when there'll be a VDT on every desk, plus all the radio, the TV, all the modern communications.

"You don't have to look to the future. The future is here."