Possible health effects of 50/60Hz electric and magnetic fields: review of proposed mechanisms.

There is inconclusive evidence from both epidemiological and laboratory studies that fields similar to those produced by electrical power transmission lines may contribute to certain diseases including cancer. There are several objections to a hypothesis of a direct causative link, based on identifying a mechanism of interaction. One is that the energy density of the fields is several orders of magnitude smaller than that associated with random thermal motion in biological tissue. Secondly, the induced currents are many times smaller than endogenous currents associated with normal membrane processes. A comparison of current densities and characteristics associated with field-related phenomena such as electrosensitivity in species of fish, night-time melatonin depression in rodents, limb regeneration in amphibians and magnetophosphenes in humans reveals little that can be of use in determining a 'response metric', yet guide-lines for the general public are in fact based on this quantity, for immediate effects at least. Indeed, currents induced by the electric component of environmental 50 Hz fields are of similar magnitude to those induced by the magnetic component, yet epidemiological studies have identified surrogates of the latter as the significant exposure metric in relation to cancer incidence. Proposed mechanisms, many of which are still at the 'working hypothesis' stage, are compared with experimental evidence. Some conflict with epidemiological evidence, itself not strong, but becoming stronger, is apparent.