By Bo Shaffer

During the last ten years questions have arisen regarding the possible health effects associated with exposure to electric and magnetic fields. Lawsuits have been filed alleging that adverse health effects and diminished property values have resulted from such "EMF" and "ELF" exposure or the fear of exposure..

What is EMF?

"EMF" means electromagnetic fields. Electromagnetic fields are pervasive in our culture and are composed of electric and magnetic fields. Most EMFs that we are exposed to are man-made, but some also occur naturally. The most widespread and enduring of these natural EMF fields is the magnetic field of the earth itself, which exists everywhere on the planet and far out into space. Although the earth's magnetic field is all around us, it is of very low strength, only about one half of a Gauss or about 500 milligauss, or mg. The Gauss is the unit of magnetic field strength, and a milligauss is one thousandth of a Gauss. The most impressive display of natural electric fields in action is that of high voltage lightning flashes, frequently seen(and heard) in the spring and summer during thunderstorms and electrical storms. Less impressive but nonetheless annoying are the minor shocks we all experience on dry days when walking on carpets builds up a static electric charge which is discharged whenever we touch a conductor.

Fields and the Electromagnetic Spectrum

Electric and magnetic fields result from electrical charges in motion. The electric current in a wire is just a bundle of electrons moving along the wire under the pressure of a voltage difference along the wire. A current of electricity produces both an electric and a magnetic field which propagate outward at right angles to one another. The radiation produced by oscillating electromagnetic fields, such as alternating current or "AC", familiar to all of us, and other sources of electromagnetic energy is called "Electromagnetic Radiation" or "EMR." The electromagnetic spectrum comprises EMR ranging from gamma rays and x-rays with ultra-short wavelengths and ultra-high frequencies, to visible light, rays with longer wavelengths like infrared (heat)radiation, microwaves, radar, UHF and VHF television signals, radio waves and at the very low and extremely low frequency ranges "ELF" of the 50 to 60 Hertz or HZ (cycles per second) of the familiar AC (alternating current) electrical power distribution system which is commonly used in the developed nations. The higher the frequency of the radiation the shorter the wavelength, so the wavelength of 60 Hz AC household current is thousands of miles.

Effects of Radiation, EMF and ELF

Radiation at very high frequencies, and very short wavelengths, like x-rays and gamma rays is called "ionizing radiation" because it can cause ionization or physical damage to a target atom or matter that it strikes. X-rays and gamma rays produce effects in living systems because the energy carried by this radiation is so large that it can break molecular bonds. It can actually break apart DNA, the molecules that make up our genes. This is the way X-ray exposure can lead to cancer. However the energy carried in 60 Hz fields and the man-made magnetic fields discussed here is much too low to break molecular or chemical bonds. Microwaves do not carry enough energy to break chemical or molecular bonds, but they are absorbed by the water in tissues where they can also set up strong currents. This causes heating, which is what makes a microwave oven work. While 60 Hz fields can also set up currents in tissues, these currents are much weaker. The amount of heat they generate is trivial compared to the natural heat that comes from the cells of the body. The EMF and ELF part of the electromagnetic spectrum discussed here is called non-ionizing radiation because it does not cause a physical disruption upon impact with matter but may, in some situations, cause some type of biological effect. The jury is still out on whether EMF/ELF also causes health effects upon exposure. However, although scientists have been studying this question for some time, there has been no definitive demonstration of a specific, proven, positive cause and effect relationship between electric and magnetic fields and health effects. Utility companies and public health agencies are getting calls from concerned citizens inquiring about possible health effects associated with the electric and magnetic fields associated with power lines and other components of the electric power distribution system such as transformers and other equipment.

Manmade Sources of EMF

In addition to natural sources, common everyday use of electricity produces electric and magnetic fields. If fact the overwhelming majority of exposure to these fields comes from these man-made sources. These types of fields are associated with power lines, wiring in buildings at home, school and in the workplace. Common electric appliances such as microwave ovens, electric ranges and cooktops, electric clocks, hair dryers, electric shavers, electric blankets, and others produce these electromagnetic fields. These appliances all produce electric and magnetic fields when they are turned on and plugged into a live electric outlet.

Commercial Use of Electricity

Before the invention of man-made electricity, humans were exposed only to the constant magnetic field of the earth and the occasional electric and magnetic field increases caused by lighting bolts. However, since the advent of commercial electricity power distribution in the last hundred years, we have been increasingly surrounded by man-made electric and magnetic fields generated by our electric power grid and the appliances we use everyday, as well as higher frequencies from radio and television transmissions and use or radar by commercial and military aviation. The most commonly used type of electricity used in our homes and places of work is alternating current or "AC", in which the current does not flow steadily in one direction but moves back and forth. Wherever there is an electric current, there are also electric and magnetic fields which are created by the electric charges. The current is measured in amperes or "amps" for short.

Intensity and Shielding of Fields

The AC fields to which we are all exposed come from high voltage, long distance power transmission lines, and from the distribution system that brings this power to our homes, work places, factories and schools. Electric and magnetic fields also emanate from common appliances as mentioned above. The magnetic fields from these sources are often much weaker than the earth's field but can sometimes exceed its 500 milligauss strength. The strength of electric and magnetic fields are reduced dramatically as one moves away from their sources. Electric fields may be blocked by objects such as earth, trees or buildings or may be shielded out by special construction techniques or certain types shielding. Magnetic fields on the other hand are normally not blocked by such objects, although certain types of metal such as "mu metal" can sometimes shield against magnetic fields.

Research Studies

There have been a number of scientific experiments, studies and epidemiological studies on the questions of potential biological and health effects of EMF and ELF. Overall the sum of these studies to date has neither confirmed nor demonstrated that exposure to such fields causes health effects. However, neither have these studies unequivocally demonstrated the absence of EMF/ELF caused health effects. Therefore, not surprisingly, research on possible health risks from EMF and ELF fields is continuing. In the United States, major support for research on possible health risks comes from the Electric Power Research Institute ("EPRI"), the U. S. Department of Energy and the Environmental Protection Agency.

Other EMF Sites:

Back to Delta Environmental

©1995 DTI           Last updated March 29, 1995           dti@deltatech.com