Q:

I have heard that exposure to weak electrical fields, such as those from overhead transmission lines, home appliances and even electric blankets, poses health risks over time. Do the wires embedded in an electric-radiant slab give off an electrical field, or does the lead sheathing on the wires block such emissions?

Alan Berry, Palos Verdes, CA

A:

Richard D. Watson, research chairman of ASHRAE Radiant Heating and Cooling Technical Committee, replies: All energized electrical devices emit an electromagnetic field (EMF). Research, to date, has not found whether the relationship cited in studies of EMF and health problems is coincidental or causal. The lead sheathing on wires in an electric-radiant slab is for grounding purposes and has no impact upon EMF.

If you’re concerned about EMF, bear these two facts in mind: EMF intensity, measured in milligauss, decreases geometrically (the inverse square law) as you move away from the source of the EMF. And EMF intensity increases with the amount of power (wattage) in a circuit. Information concerning power output is available from manufacturers of electric-radiant heat products. Both private outfits and many local utilities will measure EMF levels in your home. However, no standardized threshold of safe vs. unsafe levels of EMF has been established.