ELECTRIC AND MAGNETIC FIELDS (EMFs)

This fact sheet provides answers to basic questions about electric and magnetic fields (EMFs). It explains where EMFs can be found, how they can affect your health and what you can do to reduce exposure to them.

WHAT ARE EMFs?

EMFs are invisible forces that exist anytime electricity is being used. Electric fields are the result of voltage. For example, a common household appliance, such as a lamp, uses 120 volts of electricity. When the cord is plugged into an electric outlet, it creates an electric field because it is charged. Magnetic fields are a result of the flow of electric current. The lamp must be turned on to create a magnetic field. As you increase your distance from either field, the strength of the field decreases.

While the focus of this fact sheet is EMFs associated with the use of electrical power, it is important to note that EMFs are also created naturally by such things as lightning and static electricity.

HOW CAN I BE EXPOSED TO EMFs?

Because the use of electricity is an important part of daily living, most people are exposed to EMFs nearly all of the time. Some examples of EMF sources are power lines, home wiring, kitchen appliances, computers, TVs, electric shavers, hair dryers, electric blankets and electric clocks.

Electric currents produce magnetic fields. Stronger currents produce stronger fields. For example, the magnetic field generated by a hair dryer will be stronger when the dryer is on its “high heat” setting than when it is used on its “low heat” setting. Since magnetic fields are created only when there is an electric current, appliances plugged in, but turned “off”, do not produce magnetic fields.

HOW STRONG ARE THE EMFs FROM POWER LINES AND APPLIANCES?

The strength of EMFs depends on the amount of current flow and voltage. The strength of an electric field depends on the voltage of the object creating the field. The electric field is usually measured in units of volts per meter (V/m) or thousands of volts (kilovolts) per meter (kV/m). For example, a high voltage power line (138 kV) produces a stronger electric field than a low voltage (12 kV) power line. An electric field can exist even when there is no electric current. For example, a lamp or electric blanket plugged in but not turned “on” produces an electric field.

The strength of a magnetic field is measured in milligauss (mG). The closer you are to an EMF source, the stronger the field, and field strength declines rapidly with distance. For example, the strength of a magnetic field one foot from a microwave oven in use is about 60 mG. The strength of a magnetic field 50 feet from a high voltage power line is about 40 mG. Appliances like hair dryers create magnetic fields as high as 700 mG.

Shielding can reduce electric field strength. For example, trees, buildings and other objects, reduce electric fields. Magnetic fields, however, are not so easily blocked. Scientists have not yet found any shielding materials that effectively reduce magnetic fields.

HOW CAN EMFs AFFECT MY HEALTH?

Scientists know that exposure to EMF of 60 Hz can create tiny electric currents in the human body. However, these currents cannot be felt and are normally much lower than the body’s own natural electrical activity.

The National Research Council has concluded that no clear convincing evidence exists to show that residential exposures to EMFs are a threat to human health. Many studies have been conducted with contradictory results. The health effect of greatest interest is cancer. Some studies have shown no relationship between cancer and exposure to EMFs. Other studies have suggested a possible link between exposure to EMFs and a form of childhood leukemia. Two of these studies reported about a two-fold increase in the number of childhood leukemia cases in homes next to electrical power lines.

In 1999, the U.S. National Institute of Environmental Health Sciences (NIEHS) reviewed the data and concluded that although the cancer evidence was weak, it was still sufficient to warrant limited concern. Other studies concerning occupational exposure to EMFs have resulted in conflicting results and the NIEHS has concluded there is insufficient evidence to associate EMF exposure to a health risk.

HOW CAN I REDUCE MY EXPOSURE TO EMFs?

There are many things that can be done to reduce your exposure to EMFs. First, evaluate your everyday activities and the sources of EMFs you come into contact with throughout the day. Then take steps to reduce your exposure. The easiest way to reduce your exposure to EMFs is to limit the time you use electrical devices.

Since field strengths get lower the farther away you are, you can place appliances with small electric motors far away from you. For example, a motor driven electric clock on your bedside table may produce a fairly strong magnetic field near you as you sleep. You could move the clock a few feet away or replace it with a newer digital clock or with a wind up clock. When operating a microwave oven, stand several feet back, and if you have an electric blanket, use it only before you get into bed.

WHERE CAN I GET MORE INFORMATION?

This fact sheet was supported in part by funds from the Comprehensive Environmental Response,
Compensation, and Liability Act trust fund through a cooperative agreement with the Agency for Toxic Substances and Disease Registry, U.S. Department of Health and Human Services.