By William K. Stevens | The New York Times |
IN the century since electric power revolutionized human existence, most people have scarcely thought, if at all, about whether it is safe to live with the electromagnetic fields radiated by the cables, wires, fixtures and appliances all around them. When the question did come up, scientists generally assured the public that there was no danger to health.
They are no longer so certain. While virtually all experts still say no proof yet exists that electromagnetic fields pose any health threat, accumulating scientific evidence has convinced many that there is cause for concern.
Laboratory studies on animal cells have shown that electrical current alternating at 60 cycles per second, or 60 hertz, the kind that comes into almost every American home, emits radiation that can cause biochemical changes. Some of the changes might conceivably cause adverse health effects if the cells in the human body are similarly affected. And three epidemiological studies have demonstrated a statistical association between exposure to power distribution lines and cancer in children, although two other studies have not.
The rising sense of concern – and the uncertainty engendered by ambiguous and often contradictory data – was brought into sharp focus in a comprehensive background paper issued last month by the Congressional Office of Technology Assessment. ”The emerging evidence no longer allows one to categorically assert that there are no risks,” said the report, prepared by a team at Carnegie Mellon University. ”But it does not provide a basis for asserting that there is a significant risk.
”It is now clear that 60-hertz and other low-frequency electromagnetic fields can interact with individual cells and organs to produce biological changes,” the report concluded. While the nature of these interactions is ”subtle and complex” and their implications for public health remain unclear, the study said, there are ”legitimate reasons for concern.”
The concerns could evaporate in the face of further research. All of the findings are still considered preliminary, at best, grist for hypotheses to be rigorously tested through the scientific method. Most of the laboratory studies that have found biochemical changes have not yet been successfully repeated, and even if their findings are borne out, no one knows how much of a health risk, if any, that would mean. Other studies have found no effects at all. Virtually no one who has studied the problem believes that whatever risk might be posed by 60-hertz fields is anywhere near the risk posed by cigarettes, asbestos, automobile accidents or a whole range of other familiar hazards. And no one is yet advocating the rewiring of America.
Nevertheless, the accumulating evidence has moved the issue squarely onto the public agenda. Congress has held hearings on the question. Eight states, including New York and New Jersey, have regulated the intensity of the electrical field transmission lines can generate. The press has focused attention on the issue, most recently in a three-part series in The New Yorker magazine. And, after years of flat or decreasing research expenditures, a worldwide research effort aimed at clarifying the question is gathering momentum.
”The whole thing is very worrisome,” said Dr. David O. Carpenter, the dean of the School of Public Health operated jointly by the New York State Department of Public Health and the State University of New York at Albany. ”We see the tips of the iceberg, but we have no idea how big the iceberg is. It ought to concern us all.” Dr. Carpenter was the executive secretary of the New York State Power Lines Project, which carried out a major study on the health effects of 60-hertz electromagnetic fields; its major findings were reported in 1987.
The power lines study identified ”several areas of potential concern for public health,” particularly the possibility that magnetic fields near homes had been linked by epidemiological studies to cancer, but said final conclusions must await more research.
Even some experts associated with the electric power industry, which has long asserted that electromagnetic fields pose no risk, concede that the results of the research raise serious questions that must be answered.
”Until a couple of years ago it looked like there was nothing here at all,” said Dr. Leonard Sagan, who directs radiation studies for the Electric Power Research Institute of Palo Alto, Calif., which is supported by the power industry. Now, he said, ”all these things coming together can’t be ignored.” While stressing that ”I don’t think there’s evidence of a risk to human health that’s been demonstrated,” he said, ”I don’t mean to exclude the possibility of such a risk.” ‘Something Is Going On’
When Dr. Samuel Milham, head of chronic disease epidemiology for the Washington State Department of Health, first looked into the matter, he thought it was nonsense. ”I said it’s got to be voodoo,” said Dr. Milham, who conducted several occupational studies that link higher cancer rates with people who work around electromagnetic fields like power company employees and electricians. ”Now I believe something is going on,” he said. ”What its extent is, I don’t know.”
High-voltage transmission lines have been the focus of protest by citizens living near rights-of-way for some years. But if electromagnetic fields do turn out to pose a health risk, transmission lines may be the least of the trouble. Distribution lines, home wiring circuits, appliances, lighting fixtures, even electric blankets also create 60-hertz fields, and the study for the Office of Technology Assessment concluded that they ”could play a far greater role than transmission lines in any public health problem.”
The office’s report was prepared by Indira Nair and M. Granger Morgan, both physicists at Carnegie-Mellon University’s Department of Engineering and Public Policy, and H. Keith Florig, a research fellow in the department. Emerging Science Questions, Not Answers
The research effort aimed at understanding the relationship between electromagnetic radiation and health is an extensive one, and, according to the Office of Technology Assessment report, most of the work is of ”very high quality.” But so far it has focused on identifying some possible effects of such radiation on living tissues and organisms, and it has raised more questions than it has answered.
Any electrically charged conductor generates two kinds of invisible fields, electric and magnetic. Taken together, they are called electromagnetic fields. Sixty-hertz fields fall into what is called the extremely low frequency (E.L.F.) range of the electromagnetic spectrum. The electrical field can be blocked with shielding, but the associated magnetic field cannot easily be blocked.
Electromagnetic fields at these low frequencies do not produce the same dramatic effects on the body as are produced by two other commonly used forms of electromagnetic radiation, both at much higher frequencies: X-rays, which have enough energy to break apart D.N.A., which carries genetic information; and microwaves, which cause damage from heat. For years, scientists asserted that because 60-hertz fields can do neither, they could not possibly cause significant changes in the body.
That assertion is now being challenged by laboratory experiments on living cells and animals, and by the epidemiological studies that have shown a statistical association – but no cause-and-effect relationship -between cancer and exposure to electromagnetic fields from wires that carry electricity through neighborhoods and into homes. Laboratory Studies Abnormalities In Embryos
Findings from what is still a young and growing body of laboratory experiments with human cells and animals suggest that electromagnetic fields can interfere with the functioning of D.N.A. and R.N.A., the controllers of cell reproduction; that they can cause reproductive disorders and birth defects in chicks; that they stimulate activity in biochemicals linked to the growth of cancer; and that they affect other substances that are critically involved in the workings of the central nervous system.
At the cellular level, the evidence so far identifies the membrane that envelops the cell as the main site of interaction with electromagnetic fields. The membrane governs some of the cell’s most critical functions, like the flow of material, energy and information from the outside to the interior. If its function were severely disrupted, cell-to-cell communication and the immune response could also be disrupted, scientists say.
Some experiments have found that exposure to electrical power fields alters the flow of calcium across the cell membrane, although the health significance is not clear. Calcium governs cell division and egg fertilization. One experiment has shown that electromagnetic fields change the rate of synthesis in deoxyribonucleic acid and another that they interfere with the functioning of ribonucleic acid in converting the instructions issued by D.N.A. into production of proteins. Still another has shown that the radiation spurs the action of an enzyme associated with the growth of cancerous tumors. Mood and Sleep Disorders
One cellular experiment has shown that 60-hertz electromagnetic fields alter the action of hormones called neurotransmitters, which send signals between nerves, and of hormones that control the biological clock. If the same effect occurs in humans, the O.T.A. study said, this might play a role in a number of disorders, including altered sensitivity to drugs and toxins, disruption of the biological clock, mood and sleep disorders and chronic depression.
In what has been called the ”henhouse project,” six independent laboratories in the United States, Canada and Europe exposed fertilized chicken eggs to pulses of 60-hertz radiation like that emanating from video display terminals and television sets. Taken together, the experiments showed an increase in the proportion of abnormal embryos in eggs that had been radiated. The same effects have not been observed when eggs are exposed to steady, rather than pulsed, radiation of the sort generated by electrical appliances and power lines. Epidemiological Studies Power Lines And Cancer.
The studies that have gained perhaps the most attention, however, have sought to assess the association of electromagnetic fields encountered in everyday living with adverse health effects in humans.
In one, researchers at the Kaiser-Permanente Medical Care Program in Oakland, Calif., reported last year that women who used video display terminals for more than 20 hours each week in the first three months of pregnancy suffered almost twice as many miscarriages as women doing other types of office work. The study’s authors were careful to say that the findings did not necessarily mean that the terminals themselves had caused the miscarriages and that other factors, like stress, could have been responsible. Studies by other researchers are now under way.
Other epidemiological studies have tried to find out whether there is an association between exposure to 60-hertz fields and childhood cancer. The first of these, by two Colorado epidemiologists, Nancy Wertheimer and Ed Leeper, compared children who died of cancer in Denver between 1950 and 1973 with a control group of other children. The study found that children who lived near electrical-distribution lines were twice as likely to develop cancer as those who did not. Flaws Eliminated
The study was widely debated and criticized for what were seen as biases and failure to account for all variables. A subsequent study was commissioned by the New York State Power Lines Project to test the findings. The new study, headed by David A. Savitz, an epidemiologist now at the University of North Carolina, attempted to repeat the earlier investigation while eliminating what critics saw as its flaws. It was also carried out in Denver but involved children diagnosed from 1976 to 1983 as having cancer. To the surprise of the critics, the Savitz study bore out the earlier findings.
The scientists who designed the Savitz study ”were very skeptical,” said Dr. Carpenter, the Power Lines Project’s executive secretary. ”None of us expected the Savitz study to replicate the Wertheimer results. But the study did in fact replicate the results in almost every degree.” As much as anything, the study is widely credited with persuading many skeptics to take the issue seriously.
Dr. Savitz himself is the first to warn against drawing unwarranted conclusions from the study. At best, he said in a formal statement after the study was made public, ”there is a suggestion of a possible hazard which has yet to be resolved.” Even if the study provided conclusive proof, he said, the risk of cancer would be 1.5 or 2 cancers in 10,000 children a year. ”This would be very important,” he said in the statement, ”but minor relative to childhood injuries or risks from known cancer hazards to adults such as cigarette smoking or asbestos exposure.”
In an interview, he summed up what he and many others consider the mainstream scientific opinion about any cancer threat posed by electromagnetic fields: ”Is there reason for concern? An honest, objective review would have to say yes. Is there persuasive evidence that E.L.F. radiation causes cancer? The answer is a clear no.”
Course of Action Prudence Over Panic
Scientists are nowhere near establishing any risk standards for electromagnetic exposure. Even if that should turn out to be called for, the task is expected to be more complicated than in the case of other environmental risks to health, such as those posed by chemicals. Partly, this is because electromagnetic fields often appear to affect living tissue only at certain thresholds or ”windows” of intensity. Biological effects may be triggered at lower intensities rather than higher ones: more may not be worse.
Present efforts in several states to set ”safe” upper limits on the strength of radiation from transmission lines, the O.T.A. report said, are therefore scientifically insupportable. And in fact, reducing the intensity of fields to which people are exposed might even make things worse, said Mr. Florig of Carnegie-Mellon.
Experts at this point generally do not urge that 60-hertz fields be aggressively regulated. The Carnegie-Mellon team, however, has advanced what it calls a policy of ”prudent avoidance” until more definitive knowledge develops. They advise taking relatively low-cost, low-effort steps to limit exposure to electromagnetic fields like these:
* Try to route new transmission lines so they avoid people and widen transmission rights-of-way, but do not tear out and rebuild old lines.
* Develop new approaches to house wiring that minimize electromagnetic fields.
* Redesign new appliances to minimize or eliminate fields, but do not throw out all old appliances before they wear out.
* Use electric blankets only to preheat the bed or eliminate them.
* Move an electric alarm clock as far from the bed as is practical.
Dr. Savitz said that while concern may be justified, ”our study is not sufficiently convincing to warrant drastic action by homeowners.”
But in Canada last month, an arbitration board in a labor-management case adopted a preventive precedent in ordering that an employer cooperate in the development of a prototype shielding mechanism for video display terminals. The board reasoned that although the evidence of harm from V.D.T.’s was merely suggestive and inconclusive, ”there are simply too many incidents where the environment has been invaded by unknown factors which have come to light only after the harm has been done.”
Research Efforts Attracting More Interest
Virtually everybody who has looked at the problem advocates a major research effort. ”There is enough concern that some key questions have to be answered,” said Richard Phillips, of the Environmental Protection Agency’s Health Research Laboratory at Research Triangle Park, N.C. Dr. Phillips, a recognized authority in the field, edits the journal Bioelectromagnetics, in which much of the research on the subject has been published. ”The big question,” he said, ”is the cancer issue.”
Despite the proliferation of studies, the Office of Technology Assessment report found, there has been a marked decrease in the level of Federal research support in recent years. Congress has allocated $3 million for that purpose to the Department of Energy in the fiscal year 1989. Because of budgetary restraints, most of the environmental agency’s projects dealing with E.L.F. fields were shut down in 1986.
A number of states have undertaken modest research programs, and the electric utility industry has backed others. The major utility researcher, the Electric Power Research Institute, spent $1.7 million in 1986, but in a measure of increasing concern is spending $5.5 billion this year. It is the largest single program in the world.
Scientists in other countries are also pursuing the subject, and Dr. Sagan of the power institute said, ”One sees a worldwide research effort developing.” Moreover, he said, American scientists are showing greater interest. ”Until very recently,” he said, ”it was very difficult to get the attention of the scientific community.” That, he said, is no longer true.
”My hope is that we will have a definite answer one way or another in four or five years,” he said. ”The bad news would be if it continues to be ambiguous.”
If everyday electric and magnetic fields turn out to pose a health risk, small sourceslike the coffee maker at left could play a major role. The most intense magnetic fields in the home are found near such appliances, although the fields extend only a few feet.
Power Lines Under New Focus Much attention has focused on high-voltage transmission lines, but epidemiological studies have linked childhood cancer with exposure to magnetic fields from smaller distribution wires.
Looking At Cells Laboratory experiments have shown that electromagnetic radiation can interact with the surface of a cell to trigger changes inside the cell. The cell wall controls the flow of material, energy, and information from the outside to the cell interior.