This literature includes epidemiological studies, research on biological systems, and analyses of theoretical interaction mechanisms. No plausible biophysical mechanisms for the systematic initiation or promotion of cancer by these power line fields have been identified. Thus, even though very hard to prove a universal negative, there have been so many studies over two decades that it is virtually certain that any significant hazard would have been discovered by now. The critics make a number of very telling points. The fields produced by power lines are very small.
Power lines produce both electric and magnetic fields.
The electric field is greatly reduced in magnitude within the human body, because the body is an electrical conductor. In fact, power lines produce electric fields inside the human body that are much smaller than the electric fields that normally exist in the body. The magnetic field is not significantly shielded inside the human body, so the only realistic possibility of health effects come from the magnetic field. The magnetic fields from power lines are rather small. Typically they are about 2 milliGauss.