Some epidemiological evidence suggests that the electric and magnetic fields (EMFs) emitted by electric power, telecommunication, radar, and other electric and electronic systems might be harmful to health. Although federal authorities have not found this evidence compelling enough to regulate exposure to EMFs, public concerns have prompted political, legal, and market responses to the specter of EMF-induced health hazards. The economic impact of these responses probably exceeds $1 billion per year. Less certain is whether the health risk posed by EMFs warrants such a cost. Unfortunately, research to assess this risk may prove difficult because EMF bioeffects may be both subtle and unrelated to easily measurable aspects of exposure. This increases the importance of promoting fairness in the processes by which risks of exposure to EMFs are distributed across society.
During this century, the dramatic growth in the use of electric and electronic devices has been accompanied by a parallel increase in human exposures to the electric and magnetic fields (EMFs) that these devices emit. Electric power and telecommunication systems, electric and electronic appliances, broadcast facilities, and radar systems have contributed to rising background levels of EMFs in modern living and working spaces. While the benefits of electric and electronic technologies are clearly enormous, the pervasiveness of their EMF emissions has raised concerns about whether exposure to typical levels of EMFs in the environment are harmful to health.
Overall, the scientific evidence about the health risks of exposure to EMFs is suggestive of deleterious health effects but is not compelling. Although no regulatory action has been taken by federal authorities thus far, health concerns have prompted a number of legislative, administrative, legal, and market reactions that carry significant economic impacts. These include delays in the siting and licensing of new power lines, radar systems, and communications antennas; the filing of court cases involving claims of impaired health due to exposure to EMFs; decreases in the value of residential properties located near electric-power transmission lines and broadcast facilities; and the introduction of "low-field" power lines and consumer and office products that are more costly than power lines and product models not designed to lower EMF emissions.
The costs of these actions bear directly on what society should be willing to spend on research to learn whether the health threat posed by EMFs is real. The fact that so much risk management activity is undertaken even though there is no scientific consensus about this threat suggests that sociopolitical and ethical factors play a large role in driving society's response to the EMF problem.
Biological effects
Investigations of the biological effects of EMFs have been under way in the United States for several decades. To date, federal, state, and industry sponsors have spent several hundred million dollars on research to understand the biological effects of EMFs at frequencies ranging from 60 cycles per second (the frequency of the electric power system) to billions of cycles per second (the frequency of microwave ovens). While it is clear that EMFs at higher frequencies and strengths can damage biological systems through heating (the operating principle of the microwave oven), scientists do not know whether the health risks of long-term exposure to weaker or lower-frequency EMFs are significant. However, public concerns are mounting as a result of a number of epidemiological studies that report increased risks of cancer among persons who live near heavy-duty power lines or who work around electrical equipment. These studies suggest that the increased risk of death from cancer for these people is in the neighborhood of a few chances per 100,000 people per year. This level of risk, if real, is greater than the level of risk at which U.S. regulatory agencies have, on occasion, acted to mitigate other threats to human health, such as carcinogenic chemicals or ionizing radiation. Because of possible confounders and biases in most of the epidemiological studies per-formed to date, scientific opinion about whether the evidence from these studies represents a real EMF health effect varies enormously.
Some scientists have argued on theoretical grounds that environmental levels of power-frequency EMFs—that is, EMFs emitted by electric power systems and electrical devices—can have no biological effects because the electrical signals that they induce in body tissues are less intense than those that are produced naturally by electrical noise and the activity of the human nervous system. Other scientists contend that power-frequency EMFs might still be able to influence biological processes if cells or tissues have structures that respond to the special properties of the power-frequency signal—namely, coherence and spatial uniformity. Although there are many reports of observable biological effects of weak power-frequency EMFs, systematic efforts to replicate these findings in independent laboratories are only now getting under way.
Experiments to discern the biological effects of EMFs reveal some effects that are nonmonotonic functions of the intensity of exposure—that is, effects that are observed only within a narrow range of field strengths. For instance, studies have shown that human heart rates are slightly depressed by exposure to power-frequency EMFs typical of those beneath high-voltage transmission lines, but that they are not affected by fields 50 percent stronger or weaker.
Evidence that some biological effects of EMFs are observed only within a narrow range of field strengths implies that measures to reduce human exposure to EMFs could be counterproductive.
Evidence of nonmonotonic effects has three important implications for EMF risk assessment and management. First, it complicates the interpretation of epidemiological studies that, for the most part, have looked only for, correlations between risk and exposure measures that are increasing functions of field strength. Second, it limits the confidence with which the risk associated with strong EMFs—a risk measured in laboratory studies using animals—can be extrapolated to the risk associated with weak EMFs that humans typically encounter. Third, evidence of nonmonotonic effects has significance for proposals to mitigate exposures to EMFs, since it implies that measures to reduce the strength of these exposures could sometimes be counterproductive.
Rationales for mitigation
The possibility that EMFs may be harmful has created risk management problems that involve many sources of power-frequency EMFs, including high-voltage transmission lines, neighborhood power-distribution circuits, home and office wiring, electrical appliances, and office equipment. These problems might be ameliorated by any of a number of actions aimed at modifying people's exposure to EMFs. For instance, transmission lines can be placed on wider rights-of-way or routed to avoid homes and businesses; power-distribution wires can be close-packed to promote mutual cancellation of the field from each wire; office spaces can be arranged so that work areas are not adjacent to rooms where power transformers and other power-handling equipment are located; and electrical appliances can incorporate technologies for shielding or canceling their EMF emissions.
For management, a principal question is which, if any, of these mitigative actions can be justified. The answer depends largely on the rationales upon which mitigation decisions are based. Possible grounds include (1) balancing mitigation costs and potential health benefits, (2) assuring that no one bears an unfair burden of potential risk, (3) reducing delays in the approval of new and upgraded power lines, (4) diminishing liability risk, (5) cutting the expected costs of future retrofits, and (6) enhancing product marketability. A public agency charged with the protection of human health might base its decisions on the first two rationales, an electric utility might consider all but the last, and an electric appliance manufacturer might be concerned primarily with the last three.
To resolve conflicts over the siting of electric-power transmission lines, electric utilities could offer to purchase private property near these lines and conduct siting auctions to identify corridors for new lines
It should be noted that any measures to mitigate exposure to EMFs need to be carefully considered, since they can increase other kinds of risks to human health. Altering the electrical design of power lines and appliances to reduce EMF emissions, for instance, can have negative effects on safety. Compacting overhead power wires increases maintenance workers' risk of electrocution. Similarly, changing the design of an electric blanket to include a grounded shield increases the risk that the blanket will catch fire or shock users.
Economic impacts
Because the scientific evidence on EMF bioeffects is both complicated and contradictory, regulatory bodies and organizations concerned with scientific standards have been unable to reach a consensus on prescriptive approaches to EMF risk management. While scientific opinion varies widely about whether the EMF-cancer connection is real, public apprehension over potential EMF hazards has prompted a host of ad hoc responses, each with significant economic impacts. These impacts are evidenced in five trends.
First, concerns about EMFs have complicated and delayed the permit and siting process for new electric-power transmission and substation facilities. Some state and local legislative bodies have proposed or enacted outright moratoria on the construction of transmission lines; yet the net benefits of electric-power trading and increased reliability of electric service that even a single new transmission line can provide can be as high as tens of millions of dollars per year.
Second, the public's desire to avoid exposure to EMFs is reflected in the falling value of property along transmission-line routes. In the United States, approximately 10 million acres of land and 1 million homes lie close enough to a transmission line to have EMF levels in excess of typical background levels in most households. A decline of even 1 percent in the value of these properties amounts to a nationwide market loss of about $1 billion.
Third, the filing of court cases that involve claims of damaged health as a result of exposure to EMFs is becoming more common. Because juries are ill-equipped to deal with the complexities of evidence concerning EMF bioeffects, many of these claims have been settled out of court for undisclosed amounts.
Fourth, whether to avert litigation, avoid future retrofits of electric power lines, or exercise prudence with respect to public health, many electric utilities are unilaterally changing the design of new electric-power distribution circuits in residential areas and placing more power lines underground, on higher poles, or in more compact configurations. The cost of these measures can range from a few percent to 25 percent of the total cost of power lines. Given that electric utilities nationwide invest about $10 billion annually in the construction of power distribution circuits, these EMF mitigation practices, if widely adopted, would cost roughly $1 billion per year.
Finally, to reduce risk of liability and enhance product marketability, manufacturers of some consumer and office appliances have begun to offer "low-field" product models at prices that are a few percent higher than models not designed to lower EMFs. Both the $2 billion market for video display terminals and the $100 million market for electric blankets are expected to deal only in low-field models within a few years.
Although difficult to assess, it seems likely that the total economic cost of the above responses to potential EMF hazards now exceeds $1 billion dollars annually, a cost that will probably grow in years to come. Whether any of these responses are worth their price depends on the health benefits that they produce. These benefits can become better known only through additional research on EMF bioeffects.
In the meantime, it is instructive to compare society's current expenditures to avert or mitigate exposure to EMFs with the expenditures that might be justified under a cost-benefit model if health risks associated with EMFs prove to be as large as existing epidemiological evidence suggests—that is, if EMFs cause between 100 and 1,000 cancer deaths per year in the United States. Studies of risk valuation reveal that the value people place on reducing such comparatively small risks varies widely. A typical amount that people are willing to pay for risk reductions of 1 in 1 million is about $3, but the amount varies across the population and across different risks by at least a factor of two. If the United States wanted to restrict spending on the reduction of EMF risks to levels that are comparable to those spent to avert other risks, the most it could justify spending on EMF mitigation would be about 10 billion dollars per year. This may not be much more than the cost of current ad hoc efforts and represents just several percent of the total cost of electricity to consumers.
Limits of science
Public and private resources in the amount of about $20 million per year are spent in the United States on epidemiological and laboratory research on the bioeffects of power-frequency EMFs. Various bills now in Congress would, over the next few years, double or triple the annual federal commitment to this research, which is roughly $7 million in Fiscal Year 1992.
Two possible outcomes of future research would have a dramatic effect on the EMF debate. One would be the identification of one or more confounders or biases that would "explain" the existing epidemiological evidence that EMFs promote cancer. For instance, further studies might show that the apparent connection between EMFs and cancer was really due to a lack of randomness in the selection of study subjects. Public concerns might then be significantly quelled. Another highly significant outcome of future research would be the unambiguous replication of some EMF-induced bioeffect in a number of independent laboratories. Such replication would put to rest theoretical arguments that weak power-frequency EMFs cannot affect biological systems.
Additional research may not lead to scientific consensus about the magnitude of health risks posed by EMFs; even if it did, the public's distrust of risk management institutions might keep some EMF issues alive.
Although additional research might answer some important nagging questions, there is no guarantee that it will lead to scientific consensus about the magnitude of the health risks posed by EMFs. As the continuing scientific debates over the risk of cancer due to low-level exposures to ionizing radiation and carcinogenic chemicals show, scientific tools for risk assessment are often too blunt to tease out small but socially significant risks. Laboratory experiments on the reaction of cells and tissues to potentially harmful substances have limited relevance to the reaction of whole animals to these substances. In addition, the statistical power of epidemiological studies is rather weak, given the thresholds of risk that society seems to consider significant. The statistical power of animal experiments is greater than that of epidemiological studies, but only when exposures in those experiments are strong enough to produce an effect in a large fraction of the animal population tested. As mentioned above, the validity of extrapolating risks from exposures to strong EMFs used in animal experiments to risks from exposures to weak EMFs encountered by people is limited by evidence that EMF effects may not be monotonic. Even if scientists were to reach consensus on health risks due to EMFs, the public's growing distrust of risk management institutions may keep the most contentious EMF issues—for example, the siting of electric-power transmission lines—alive in perpetuity.
Promoting fairness in EMF risk management
Like other environmental issues, the EMF issue is as much about sociopolitical and ethical concerns as it is about health risk. It has a sociopolitical dimension because it pits property owners, workers, and consumers concerned about exposure to risks against large organizations such as electric utilities, manufacturers, and government agencies. The issue has an ethical dimension because it involves balancing individuals' desires to eliminate involuntarily imposed risks (however small) with society's need to have reliable electric power and electric products at an affordable price.
Ongoing EMF-bioeffects research programs should be complemented by a program of social science research that would explicitly deal with these sociopolitical and ethical concerns. Such a program could assess people's willingness to pay to avoid exposure to EMFs, devise ways to incorporate the public's values in risk management decisions concerning EMFs that are made on its behalf, and articulate the moral basis for imposing involuntary risk such as that borne by persons living and working on property along new electric-power transmission corridors. It could also evaluate the potential of various ways to resolve conflicts over the siting of electric power lines. These could include offers by electric utilities to purchase private property near power lines, guarantees by these utilities that property would not be devalued by its proximity to new lines, and siting auctions whereby utilities identified corridors for new lines by asking property owners along all possible routes to bid on their willingness to accept a power line on their property.
EMF risk management can be fair only if stakeholders are well informed about the evidence on EMF bioeffects, and about the feasibility and costs of modifying human exposure to EMFs. Unfortunately, the complexity of these subjects makes the public particularly vulnerable to selective reporting about them. Such reporting has been exploited by interest groups on both sides of the EMF debate. Much work is needed to understand the information needs of various groups and to develop channels to address those needs. Recent initiatives by the U.S. Department of Energy, the U.S. Environmental Protection Agency, the state of California, and the electric utility industry represent moves in the right direction.
H. Keith Florig is a fellow in the Center for Risk Management at Resources for the Future. Portions of this article are drawn from his article in the July 24, 1992 issue of Science.
A version of this article appeared in print in the October 1992 issue of Resources magazine.
A version of this article appeared in print in the October 1992 issue of Resources magazine.
