Electromagnetic fields (EMFs) are low-level radiation generated by electrical devices, including power lines, household appliances, and computer terminals. They penetrate walls, buildings, and human bodies, and virtually all Americans are exposed to them, some to relatively high levels. Several dozen studies, conducted mainly over the last 15 years, suggest that exposure to EMFs at certain levels may cause serious health effects, including childhood leukemia, brain tumors, and damage to fetuses. But other studies show no such connections.

EMFs are strongest around power stations, high-current electric power lines, subways, movie projectors, hand-held radar guns and large radar equipment, and microwave power facilities and relay stations. Common sources of everyday exposure include electric razors, hair dryers, computer video display terminals (VDTs), television screens, electric power tools, electric blankets, cellular telephones, and appliances such as toasters and food blenders.

The electricity used in North American homes, offices, and factories is...