Can the electric and magnetic fields (EMF) to which people are routinely exposed, cause health effects? What are sources of EMFs, and when are EMFs dangerous?
EMF (or ElectroMagnetic Field) is a broad term which includes electric fields generated by charged particles in motion and radiated fields such as TV, radio, hair dryer, and microwaves. Electric fields are measured in units of volts per meter or V/m. Magnetic fields are measured in milli-Gauss or mG. The field is always strongest near the source and diminishes as you move away from the source. These energies have the ability to influence particles at great distances. For example, the radiation from a radio tower influences the atoms within a distant radio antenna, allowing it to pick up the signal. Despite the many wonderful conveniences of electrical technology, the effects of EMF on biological tissue remains the most controversial aspect of the EMF issue, with virtually all scientists agreeing that more research is necessary to determine safe or dangerous levels.
Research since the mid-1970s has provided extensive information on biological responses to power-frequency electric and magnetic fields. The Electric and Magnetic Fields (EMF) Research and Public Information Dissemination (RAPID) Program was charged with the goal of determining if electric and magnetic fields associated with the generation, transmission, and use of electrical energy pose a risk to human health. The fact that 20 years of research have not answered that question is clear evidence that health effects of EMF are not obvious and that risk relationships, if the risk is identified, are not simple. Because epidemiologic studies have raised concerns regarding the connection between certain serious human health effects and exposure to electric and magnetic fields, the program adopts the hypothesis that exposure to electric or magnetic fields under some conditions may lead to an unacceptable risk to human health. The focus of the program is not only to test, as far as possible within the statutory time limits, that hypothesis for those serious health effects already identified, but to identify as far as possible the special conditions that lead to elevated risk and to recommend measures to manage risk.
Electromagnetic hypersensitivity (ES) is a physiological disorder characterized by symptoms directly brought on by exposure to electromagnetic fields. It produces neurological and allergic-type symptoms. Symptoms may include, but are not limited to, headache, eye irritation, dizziness, nausea, skin rash, facial swelling, weakness, fatigue, pain in joints and/or muscles, buzzing/ringing in ears, skin numbness, abdominal pressure and pain, breathing difficulty, and irregular heartbeat. Those affected persons may experience an abrupt onset of symptoms following exposure to a new EMF such as fields associated with a new computer or with new fluorescent lights, or a new home or work environment. The onset of ES has also reported following chemical exposure. A concerted effort to provide scientifically valid research on which to base decisions about EMF exposures is underway, and results are expected in the next several years. Meanwhile, some authorities recommend taking simple precautionary steps, such as the following:
The Office of Technology Assessment of the Congress of the United States recommends a policy of prudent avoidance with respect to EMF. Prudent avoidance means to measure fields, determine the sources, and act to reduce exposure.
Electric fields in the home, on average, range from 0 to 10 volts per meter. They can be hundreds, thousands, or even millions of times weaker than those encountered outdoors near power lines. Electric fields directly beneath power lines may vary from a few volts per meter for some overhead distribution lines to several thousands of volts per meter for extra high voltage power lines. Electric fields from power lines rapidly become weaker with distance and can be greatly reduced by walls and roofs of buildings.
Magnetic fields are not blocked by most materials. Magnetic fields encountered in homes vary greatly. Magnetic fields rapidly become weaker with distance from the source.
The chart on the left summarizes data from a study by the Electric Power Research Institute (EPRI) in which spot measurements of magnetic fields were made in the center of rooms in 992 homes throughout the United States. Half of the houses studied had magnetic field measurements of 0.6 mG or less, when the average of measurements from all the rooms in the house was calculated (the all-room mean magnetic field). The all-room mean magnetic field for all houses studied was 0.9 mG. The measurements were made away from electrical appliances and reflect primarily the fields from household wiring and outside power lines.
If you are comparing the information in this chart with measurements in your own home, keep in mind that this chart shows averages of measurements taken throughout the homes, not the single highest measurement found in the home.
Magnetic fields close to electrical appliances are often much stronger than those from other sources, including magnetic fields directly under power lines. Appliance fields decrease in strength with distance more quickly than do power line fields.
|The graph shows magnetic fields produced by electric blankets, including conventional 110-V electric blankets as well as the PTC (positive temperature coefficient) low-magnetic-field blankets. The fields were measured at a distance of about 2 inches from the blanket’s surface, roughly the distance from the blanket to the user’s internal organs. Because of the wiring, magnetic field strengths vary from point to point on the blanket. The graph reflects this and gives both the peak and the average measurement.|