Electric and magnetic fields are generated by all power sources, including conductors, wiring, tools and appliances. The fields increase with the magnitude of the power source, but dramatically decrease with distance from the source conductor or wiring.
Electric fields and magnetic fields are independent of each other.
Electric fields are reduced by distance, by mutual cancellation (placing the wires as close together as possible without creating an arc between them) or by placing objects or insulation between the wire and the exposure location. Magnetic fields are reduced by distance, by mutual cancellation or by specific types of shields.
The effects of fields from power lines have been the object of research since the late 1950s. Over 26,000 research reports have been generated in that time, and none report adverse health cause and effect.
The incidence of cancer has not increased with the increased use of electricity in the United States or any other country that measures incidence rates. Scientists and doctors have found no testable hypothesis that demonstrates a possible mechanism by which power fields can cause adverse health effects, cancer or any other disease or debilitating condition.
A 1979 study in Denver, Colorado, reported on preliminary research of possible environmental factors associated with childhood cancer. Since then, at least a dozen similar studies have been completed in an effort to determine the relationship. More than half of the studies reported no association. Those that did report a possible association have not been reproducible in later studies that were larger and better controlled.
Using the raw data on fields and exposures collected in the dozen studies, the International Agency for Research on Cancer concluded that there may be a possible association between a single, rare form of childhood cancer and magnetic fields. If the possibility does exist, it is a very low probability and a mechanism for causation is not known.