What are electric and magnetic fields?
How strong are magenetic fields near transmission lines?
What are the issues surrounding EMFs?
What research is under way?
What does the research mean from a public health perspective?
How can I arrange for a measurement of the magenetic fields around my home or business?
What precautionary measures are available?


Q: What are electric and magnetic fields?
A: Electric and magnetic fields are all around us. These invisible fields of energy exist around anything that carries or uses electricity. Power lines, appliances, light fixtures and electric wiring all produce EMF. Electric fields are produced by the voltage, or the strength of an electric charge on a wire, even when no current is flowing. Magnetic fields are produced only when a current is carrying the electric charge through a wire or conductor. Therefore, an appliance that is plugged in but not turned on will produce an electric field. When the appliance is operating, both an electric and magnetic field are present. Electric and magnetic fields quickly decrease as you move away from the source, but magnetic fields -- unlike electric fields -- pass through most materials and are difficult to shield.

Q: How strong are magentic fields near transmission lines?
A: Many variables affect field stength: the amount of current flowing, distance from the wires, and how the wires are positioned in relation to one another. The strength or intensity of magnetic fields are commonly measured in units called milligauss (mG), and become weaker with distance.

Below are examples of magnetic fields in milligauss measured from different voltage levels and various distances from transmission lines.

*Assumes normal current flow.
At a distance of 300 feet, magnetic fields are similar to typical background levels found in most homes.

Below are examples of magnetic fields in milligauss (mG) measured from various distances for common household appliances.

Source: Gauger, Jr., Household Appliance Magnetic Field Survey. IEEE transactions on power apparatus and systems. PA-104.

Q: What are the issues surrounding EMF?
A: Electric fields first attracted attention in the early 1970s. Studies conducted by the government and industry showed that strong electric fields produce some biological effects, but none proved that they are harmful to human health. Magnetic fields, which can't be felt and pass directly through the body, were essentially ignored for many years. In the early 1980s, scientists began to study magnetic fields more closely when some epidemiological studies -- research that relies on statistics to show associations between the occurrence of disease and potential causes -- suggested some possible association between magnetic fields and certain types of cancer. Scientists generally agree that these studies, taken as a whole, show no consistent association between magnetic fields and an increased risk of cancer. In October 1996, a National Research Council report concluded that current evidence does not link exposures to residential EMFs with cancer, adverse neurobehavioral effects, or reproductive and developmental impacts. In June 1999, a National Institute of Environmental Health Sciences report also concluded that evidence is "weak" that exposure to magnetic fields raises the risk of cancer and other human disease. Despite such findings, EMFs continue to be studied and debated in scientific and other public forums.

Q: What research is under way?
A: For many years, scientific research has been conducted at medical schools, universities and research institutes. The electric utility industry supports research efforts to further our understanding of EMF and possible adverse health effects and has funded more than $100 million in research over the last three decades. Ongoing research continues through the world's most comprehensive EMF research program conducted by the Electric Power Research Institute.

Q: What does the research mean from a public health perspective?
A: We rely upon outside experts for an analysis of research findings. A scientific review by the Oak Ridge Associated Universities for the U.S. Office of Science and Technology concluded that "epidemiologic findings of an association between electric and magnetic fields and childhood leukemia or other childhood or adult cancers are inconsistent and inconclusive." Scientists generally agree that:

• The epidemiologic studies, taken as a whole, show no consistent association between magnetic fields and cancer;
• Laboratory studies have not established a plausible mechanism to explain how fields interact with biological systems; and,
• Current research findings, taken as a whole, do not provide the basis for concluding that a risk exists, or that the safe and efficient way in which electricity is delivered should be modified.