A link between power line magnetic fields and childhood leukemia was revealed in a 1979 health study. More studies in the U.S. and Europe supported these findings, including links to other diseases. But when careful measurements were made in schools, offices and residences it was found that most high magnetic fields in buildings were caused by certain common wiring errors, as well as by electric currents on water pipes due to grounding practices. Karl Riley pioneered a successful method of tracing high magnetic fields to the site of the error. A simple correction clears the field. Though his...