Melatonin is a hormone, which is synthesized in the pineal gland in the brain. It is secreted especially at night, when no light reaches the retina. Melatonin regulates the human and animal circadian rhythm by a variation of its concentration. During the day, the concentration of melatonin in the blood is low and at night, the concentration is high. The level of melatonin decreases with advancing age and it varies considerably between individuals. Melatonin is an effective endogenous radical scavenger.
The German Commission on Radiological Protection (SSK) concludes in its recommendation from 2001 "Threshold Values and Precautions for Protection of the General Public from Electromagnetic Fields", that the hitherto studies present very indistinct results from animal experiments and that there is no evidence of adverse effects on human health. They recommend suitable research to answer the open questions on this topic. A current scientific review by Halgamuge (2013), in which more than 100 studies on the effects of power frequency fields (50/60 Hz) were evaluated, also arrived at the conclusion that the investigations from different laboratories provide indistinct results and that there is need for further research, especially on long-term effects. The International Commission on Non-Ionizing Radiation Protection (ICNIRP) confirms in its evaluation of effects of extremely low-frequency fields on health from 2010 that the exposure to 50 Hz/60 Hz electric or magnetic fields has no adverse effects on the neuroendocrine system, especially on the melatonin secretion.