High Voltage Power Lines: the Minimium Distance From a House

EMF Exposure

• High-voltage power lines are only one source of EMFs. Fluorescent lights, electric blankets, small appliances, power tools, television sets and many other items in the home emit EMFs. A 1992 study by the National Institute of Environmental Health Sciences found that most people in United States are exposed to about the equivalent of 0.5 milligauss (mG) every 24 hours. Your exposure varies with your activities. A milligauss is a unit of unit of magnetic induction. If you stood in front of a copy machine for an hour making copies, you could be exposed to anywhere from 4 to 200 mG, depending on the machine.

EMF and High-Voltage Lines

• High-voltage power lines emit a considerably stronger EMF than your toaster or light bulbs. Standing 65 feet from the tower of a 500-kilovolt transmission line, you'd be receiving about 29.4 mG. Move to 100 feet away and this drops to 12.6 mG. At 200 feet, your exposure drops to 3.2 mG, and at 300 feet you're exposed to only 1.4 mG — less than that emitted by your electric clothes dryer. Step inside your house and the EMF exposure drops further, since building materials in the walls block even more of the EMF.

Measuring Your Risks

• Studies in the late 1970s and early 1980s linked EMF exposure to childhood leukemia. Scientists criticized these studies for lack of control groups or small sample sizes. Numerous studies since that time have not shown a strong correlation between levels of EMF exposure and cancers. One problem is isolating the kind of EMF exposure. Everyone has some exposure from his everyday activities, making it difficult to test the effects of one type of exposure, such as exposure from power lines.

Considerations

• Most municipalities have no laws regulating the distance homes must be from power lines. A 2007 report in the "Appraisal Journal" found that any effect of property values from high-voltage lines disappeared when homes were 200 feet or more from the lines. At this distance, buyers apparently felt the danger from exposure to the lines did not impact their view of the value of the house. If you're shopping for a home, you might use 200 feet as a distance at which your future property values and your health are unlikely to be affected.