(FORTUNE Magazine) – Though it's still unclear whether extremely low frequency (ELF) fields ^ contribute to cancer, you may want to play extra safe and not take unnecessary chances. Granger Morgan, a professor of engineering and public policy at Carnegie-Mellon University, coined the term ''prudent avoidance'' to describe ways to limit ELF exposure without great cost or inconvenience. Most people move in and out of fields of varying intensity all day (see chart). Scientists believe that routine brief exposures, even if intense, probably do not put anyone at risk. However, it may be wise to avoid prolonged periods within a field. Studies have correlated cancer with long-term exposures above two to three milligauss. The background level in most homes is around one milligauss. After Morgan used a gauss meter to measure fields in his own house, he moved his son's bed to a different part of the boy's room. In general, the young seem more susceptible than grownups. Here are a few steps to take that may cut down on risk: -- Keep your VDT at arm's length. Stay at least 28 inches from the front of it, and don't sit within three feet of the sides or back of anyone else's. The fields are more intense there. -- Keep the kids a good three feet from the color TV, which creates the same kind of fields that VDTs do. -- Reduce the use of electric blankets, especially during pregnancy. Try turning on the blanket only to heat up the bed and unplugging it before getting in. -- Move electric clocks, radios, answering machines, and other electrical devices that stay on continuously several feet away from your head when you are sleeping. Or use battery-operated machines, which don't emit ELF fields. -- Don't stand in front of the dishwasher or microwave oven while it's on. -- As a very rough guideline, if you have small children or expect to get pregnant, don't buy a house within 150 feet of a local high-current line or 400 feet of a long-distance high-tension line. -- Measure the fields in your home (or prospective home). Some utilities will do this, or you can buy or rent an easy-to-operate gauss meter. For a price list with ordering information, send a self-addressed stamped envelope to Microwave News, P.O. Box 1799, Grand Central Station, New York, N.Y. 10163.

CHART: NOT AVAILABLE CREDIT: SOURCE: ELECTRIC POWER RESEARCH INSTITUTE CAPTION: Magnetic field exposure In one day this man was exposed to fields from (1) a desktop computer, (2) a TV set, (3) an electric blanket, (4) an electric razor, (5) a microwave oven, (6) a heating/cooling unit, (7) a power line and substation he walked past.