A study on extremely low-frequency electric and magnetic fields and cancer: Discussion of EMF safety limits

Since Wertheimer and Leeper reported in 1979 that the incidence of cancer in children living near distribution lines is twice or three times as high as normal, the association between leukemia or cancer and extremely-low-frequency (ELF) electric and magnetic fields (EMF, electromagnetic fields) has often been the subject of debate. Compared with the thermal effect of high frequency bands, the non-thermal effects of ELF-electromagnetic fields on animals are very weak and have been studied in the recent past. A positive correlation between low level ELF electromagnetic fields and some specific cancers was detected by epidemiological studies but not directly by laboratory experiments. Nevertheless it has been reported that very low-level (0.1 mu T order) ELF electromagnetic fields can induce cell proliferation and a high transcription rate in human lymphocytes and human carcinoma cell lines. However, more investigations are necessary to arrive at an appropriate conclusion as to whether a low level ELF electromagnetic field induces mutation or acts as a promotor of cancer. In the last two decades, equipment using high power EMF e.g. pulse magnetic fields have come into common use and the effects of eddy currents, which are induced by the time-varying magnetic fields, in humans and animals are clearly noticed. These effects are magnetophosphenes, spastic contraction of muscles and stimulation of nerves. In 1990, the American Conference of Governmental Industrial Hygienists (ACGIH) published the threshold limit values (TLV) of ELF magnetic fields as a function of 60/f (frequency) mT while in 1993 the National Radiation Protection Board (NRPB of the UK) published 80/f mT safety guideline. These magnetic flux densities i.e. 1.2 mT at 50 Hz recommended by ACGIH or 1.6 mT at 50 Hz by NRPB were calculated so as to obtain a current density of 1-10 mAm(-2) i.e. the supposed minimum electric current to affect animals. While these recommended values are 100 to 1,000 times higher than the flux density levels in our living environment, the suggested value that epidemiologists think has deleterious effects on humans is 0.2 mu T. It is difficult to decide which is the right guideline to adopt: the one suggested by the results of epidemiological surveys indicating that very low-level EMF raises the incidence of leukemia and other cancer, or the one which was recommended as the minimum level of magnetic flux density inducing a current that would supposedly affect humans and animals. Therefore this disparity between the values arrived at by epidemiological surveys and that recommended by regulatory agencies has to be resolved.