Electric and Magnetic Fields (EMF) and Health

Peter A. Valberg, Ph.D.

March, 2001

Where does EMF come from?

All matter contains electrically-charged particles. Most objects are electrically neutral because positive and negative charges are present in equal numbers. When the balance of electric charges is altered, we experience electrical effects, such as the static electricity attraction between a comb and our hair, or drawing sparks after walking on a synthetic rug in the wintertime. The work put into electrically charging something is measured by the voltage. Voltage on a power line is like the “pressure” of the electricity, and is analogous to the pressure of water in a plumbing system.

Electrical effects both in nature and in society’s use of electricity (generation, transmission, consumption) produce EMF. Because our everyday lives are dependent on electricity, we need to be aware of the potential health effects of electricity. We are all familiar with the hazards of electric shock which comes from contact with bare wires. EMF exists in the space around electrical devices and is an expression of the fact that electric charges exert force on each other.

Electric charges push and pull on each other. Opposite charges (i.e., + and –) attract and like charges (i.e., + and +) repel. Scientists call this force the electric field, and say that each electric charge generates an electric field that exerts force on other nearby charges. In short, an electric field is a measure of force per unit charge, and is often given in units of volts per meter (V/m).

When electric charges move, an electric current exists, which generates a magnetic field. Units of electric current are amperes (A), and current measures the “flow” of electricity, which is analogous to the flow of water in a plumbing system. The moving charges in an electric current produce a magnetic field which exerts force on other moving charges. In short, a magnetic field expresses the force per unit current, and is often given in units of gauss (G) or milligauss (mG). Electric motors use this principle to turn electricity into mechanical work. Conversely, magnetic fields are used to generate electric power from mechanical energy.

Magnetic fields are produced by the earth’s core, and can be easily demonstrated with a compass needle. The size of the earth’s magnetic field in the North America is about 570 milligauss (mG). Permanent magnets contain electrical currents at the atomic level that can generate strong magnetic fields. Typical toy magnets (“refrigerator-door” magnets) produce 100,000 – 500,000 mG. Magnetic resonance imaging (MRI) is a medical diagnostic procedure that puts humans in fields even larger (10,000,000 mG). These are all steady or DC fields.

Electric transmission lines create EMF because they carry electric currents at high voltages, and EMF decrease in size as the distance from the source (the electric charges or currents) increases. For a transmission line, EMF levels are highest near the center of the right-of-way, and the levels drop off rapidly as you move away from the transmission corridor. Electricity provided to homes and offices uses currents and voltages that change direction and intensity 60 times a second, called 60 “Hertz” (Hz). Because of this, the EMF also fluctuates up and down at 60 Hz, and these are called “AC” fields, because they are derived from Alternating Currents. Power-line EMF is of a much lower frequency than radio waves, where the frequencies are greater than 100,000 Hz. Thus, it is not correct to speak of EMF “emissions” from power lines because, unlike radio waves, power-line EMF neither propagate away from the line or carry energy away from it.

Why the concern?

EMF are present in the vicinity of all electrical devices, and human society has lived with (and used) electrical devices for over a century. Beginning in the late 1970’s, some research scientists turned asked whether there might be health effects from EMF associated with electricity generation and use. A period of intensive research followed, but now, much of this effort is winding down because well-funded, worldwide, intensive laboratory investigations have not been able to uncover reliable evidence for an EMF health hazard.

Where do we encounter EMF?

For residences, typical 60-Hz magnetic fields in the middle of rooms (away from appliances) range from about ½ to 2 mG. These fields are, to a large extent, produced by outdoor electricity distribution wiring, electric wiring inside the house, and indoor ground-current return pathways (i.e., currents on the water pipes to which electrical systems are grounded).

Larger magnetic field levels can be found anywhere electricity is used. For example, microwave ovens, refrigerators, fluorescent lamps, electric ranges, clothes washers, toasters, vacuum cleaners, and many other appliances produce magnetic fields of size 40 – 100 mG at distances of 1 foot. The magnetic fields from personal-care appliances such as shavers, hair dryers, massagers, electric toothbrushes, and electric blankets can be many 100’s of mG. Even though motorized electric appliances produce some of the highest EMFs commonly encountered, such appliances have been used for many years without evidence of ill effects.

Magnetic fields from electric current have been known to exist since their discovery by scientists in the 1800’s, and are not a recent technological creation. Per capita electric power consumption has gone up in the U.S. approximately 20-fold over the last 50 years, and human exposure to magnetic fields at power-line frequencies has gone up due to increased use of household appliances, personal-care appliances, electric toys, and audio-video equipment. Moreover, rural electrification, the increased delivery of electric power to residences, and the increased use of electrical office equipment have also contributed to greater EMF exposure. Over this same period of time, the U.S. has seen great improvements in health statistics (e.g., decreases in age-specific mortality, decreased cigarette smoking). Thus, a broad perspective on public health in the US does not provide a basis for health concerns about EMF associated with electricity use.

What kind of research has raised the public concern about EMF?

The epidemiology studies have received the most attention. “Epidemiology” is a statistical science that looks for correlations between patterns of disease occurrence and patterns of human lifestyle, diet, environment, or exposure. An epidemiologic study published in 1979 suggested that living near electric power distribution lines was linked to an increased risk of childhood cancer. In any such study, the actual EMF levels that children had been exposed to were unknown, so the researchers developed a surrogate for past EMF exposures that was based on the proximity, number, and size of electric utility lines near the home. This summary description of the electric power distribution line configuration near a home was called its “wire code.”

What has been done in response to the concerns raised about EMF?

Since the first study, a number of epidemiologic studies have examined associations between disease and the “wire code” classification of homes. If an association was seen with the wire code classification, it was interpreted as showing an effect of EMF on the disease being studied. However, repeat studies showed that the associations with wire code were weak and inconsistent. Moreover, the associations disappeared when actual measured magnetic fields were substituted in place of wire codes. It was found that the wire codes were poor surrogates for actual EMF exposure, but rather, were good surrogates for many other non-EMF factors such as traffic density, age of the home, rental vs. ownership, and assessed value of the home. This made it unlikely that the wire code associations with cancer risk were actually an effect of EMF exposure. That is, the EMF exposure was not a “causal” factor in the associations reported.

Supporting evidence for an effect of EMF exposure on health has not been forthcoming from laboratory animals exposed to EMF, or from mechanistic analysis of how EMF might cause an effect on living cells. To date, there is neither an accepted mechanism by which power line EMF can cause disease, nor is there any animal model in which exposure to even large magnetic fields has consistently produced a disease or a pre-disease condition. This means that no one has been able to identify what aspect of EMF is the one we should potentially avoid. If there were bad health effects, would they be due specifically to the frequency of oscillation, the electric fields, the magnetic fields, continuous exposure, intermittent exposure, peak fields, transients, or what? In spite of many years of work, no firm evidence of adverse EMF effects has been found in the laboratory.

In summary, the current scientific evidence available from a considerable amount of EMF research and human experience has yet to identify any particular level of power-line EMF as hazardous to health. For example, the steady magnetic field of the earth is about 570 milligauss (mG) in size, and is not believed to have any adverse biological effects. Power-line magnetic fields are generally much smaller than this, but they oscillate in size and direction at 60 times a second. Of course, because of the movement of your body and the flow of your blood cells, the earth’s field is also experienced by your body as a magnetic field changing in time.

What is the present status of expert opinion on EMF health effects?

At this point in time, a large volume of literature on the question of EMF health effects has been generated, representing the accumulation of many years of laboratory work and many years of human experience with EMF. The scientific data on EMF and health have been assembled and reviewed by many independent consensus groups of research and health scientists. These groups and agencies include the World Health Organization, the National Radiation Protection Board (UK), the National Academy of Sciences, the American Medical Association, the American Physical Society (the professional society for American physicists), the American Cancer Society, the Swedish National Health and Welfare Board, and others. The reports of these groups are voluminous, thorough, and even-handed. Some of the conclusions are given below. These “blue-ribbon” panels did not identify EMF from any type of electric-power transmission line as unsafe for nearby residents and public.

In 1996, the National Academy of Sciences (NAS) reviewed the scientific literature regarding EMF effects on health. The NAS concluded that power-line EMF was not a human health hazard, stating:

“Based on a comprehensive evaluation of published studies relating to the effects of power-frequency electric and magnetic fields on cells, tissues, and organisms (including humans), the conclusion of the committee is that the current body of evidence does not show that exposure to these fields presents a human-health hazard. Specifically, no conclusive and consistent evidence shows that exposures to residential electric and magnetic fields produce cancer, adverse neurobehavioral effects, or reproductive and developmental effects.”

In 1997, the National Cancer Institute completed a comprehensive epidemiologic study, published in the New England Journal of Medicine (Martha Linet and collaborators). This study tried to replicate earlier (smaller) studies showing an association of childhood leukemia with utility wire configurations outside the home. The authors concluded that their study of 1,258 children showed no EMF effect: “Our results provide little evidence that living in homes characterized by high measured time-weighted average magnetic field levels, or by the highest wire-code category increases the risk of acute lymphoblastic leukemia in children.”

The World Health Organization (1998) published a review of EMF health effects; they concluded that additional topic areas for research could be suggested, but that currently available evidence was not persuasive of a health effect:

“It was concluded that, while health hazards exist from exposures to ELF at high field strengths, the literature does not establish that health hazards are associated with exposure to low-level (environmental) fields.” [High field strengths would be upwards of 50,000 mG, whereas power-line fields are generally less than 100 mG.]

The International Commission on Non-Ionizing Radiation Protection (1998) proposed a “reference level” of allowable continuous EMF exposure for the general public of 830 mG (which is an order of magnitude higher than typical EMF exposure from electric-power lines).

The National Academy of Sciences/National Research Council (1999) evaluated the scientific and technical content of research projects conducted under the “U.S. EMF RAPID Program,” and concluded that:

“Results of the EMF-RAPID program do not support the contention that the use of electricity poses a major unrecognized public-health danger.”

“No finding from the EMF-RAPID program alters the conclusions of the previous NRC review on the Possible Effects of [EMF] on Biologic Systems (NRC 1997). In view of the negative outcomes of EMF-RAPID replication studies, it now appears even less likely that [EMF] in the normal domestic or occupational environment produce[s] important health effects, including cancer.”

The report “recommends that no further special research program focused on possible health effects of power-frequency magnetic fields be funded.”... “unless a biologic effect that can be used to plan the studies” is identified.

The National Institute of Environmental Health Sciences (1999) has announced that, after six years of accelerated EMF research, the evidence for a risk of cancer and other human disease from the electric and magnetic fields (EMF) around power lines is “weak.”

“[EMF] exposure cannot be recognized as entirely safe because of weak scientific evidence that exposure may pose a leukemia hazard . . . . The NIEHS does not believe that other cancers or non-cancer health outcomes provide sufficient evidence of a risk to currently warrant a concern.”

“Virtually all of the laboratory evidence in animals and humans, and most of the mechanistic studies in cells fail to support a causal relationship.... The lack of consistent, positive findings in animal or mechanistic studies weakens the belief that this association is actually due to [EMF] . . . .”

Health Canada has provided the following statement on EMF (December 1999): “For a power frequency of 60 Hz, there is at present no Canadian national standard for EMF exposure. We are unsure of what levels of EMFs are safe or unsafe because the existing worldwide scientific evidence is not sufficient to define a level of exposure that can affect human health.”

The Ministry of Health of the government of the province of British Columbia in Canada has concluded that (March 2000):

“When the research to date is taken as a whole, the evidence does not support the assumption that fields surrounding power lines, appliances, etc., pose a risk to human health. In recent years, larger, better designed studies have provided firmer evidence that exposure to these fields does not increase the risk of childhood cancer or produce other detrimental health effects.”

The American Cancer Society (ACS) conclusions on EMF are:

“Electromagnetic radiation at frequencies below ionizing and ultraviolet levels has not been shown to cause cancer. While some epidemiologic studies suggest associations with cancer, others do not, and experimental studies have not yielded reproducible evidence of carcinogenic mechanisms. Low-frequency radiation includes radiowaves, microwaves, and radar, as well as power frequency radiation arising from the electric and magnetic fields associated with electric currents (extremely low-frequency radiation).”

What can we conclude about the possibility of EMF health effects?

It is clear that careful reviews of scientific data by panels of experts do not support the claim that EMF from electric-power transmission lines can cause human health effects. To quote Dr. Charles Stevens, the chair of the National Academy of Sciences committee that reviewed EMF research in the 1996 report: “Science can’t prove that anything is safe. But so far we have failed to find a hazard.”

Peter A. Valberg, Ph.D.

March, 2001