[Biological influences of electromagnetic fields].

In recent years some people expressed concern about possible health effects of electric and magnetic fields produced by exposure to extremely low frequency bands (ELF: less than 300 Hz). This was first mentioned by epidemiological studies. However, the epidemiological method has several limitations that are difficult to overcome. One problem is the detection of relationships when the risk ratios are relatively low. Another obstacle may be how to define 'strength' of magnetic or electric fields. In animal studies, there have been published several papers that melatonin was depressed by exposure to magnetic fields. Levels of photon energy at the ELF bands are extremely low, hence it provides difficulty how to elucidate the 'positive' experimental results in terms of biophysical mechanisms.