Daytime 50 Hz magnetic field exposure and plasma melatonin and urinary 6-sulfatoxymelatonin concentration profiles in humans

Concern about the health effects of extremely low frequency (ELF) magnetic fields (MF) has been raised by epidemiological studies indicating an associ ation between certain cancers and living near power lines or working in hig h electric field environments. Alterations in pineal function have been pro posed as a mechanism through which power-frequency MFs may interact with li ving organisms. A double blind laboratory study was performed to evaluate d aytime exposure effects of 100 muT root mean square (rms) 50 Hz MF. Three h ead exposure sessions of 30 min each were performed: sham, continuous, and intermittent (15 s on/off cycles) MFs were presented to each subject in ear ly or late afternoon (13:30 or 16:30 hr). Twenty-one healthy male volunteer s (20-27 yr old) participated in these 3-weekly experimental conditions. Bl ood samples were drawn for serum melatonin measurement, hourly at night (fr om 20:00 to 07:00 hr) under controlled environmental conditions. Urinary ex cretion of 6-sulfatoxymelatonin (aMT6s), the main melatonin metabolite, was measured for a 17 hr period, by means of urine samples taken at 19:00 hr ( 14:00-19:00 hr "afternoon period"), 23:00 hr (19:00-23:00 hr "evening perio d"), and 07:00 hr, day 2 (23:00-07:00 hr day 2 "night-time period"). There were no significant differences in either plasma melatonin or in aMT6s excr etion profiles in the three experimental conditions. However, a tendency fo r a smaller increase of night-time urinary aMT6s after continuous MF exposu re was found (P = 0.08) particularly in men with the lower excretion rate o f aMT6s ("Low Group") (P = 0.07). We conclude that this study does not indi cate that daytime acute MF exposure influences either melatonin secretion o r aMT6s excretion. Inter-individual differences in pineal production of mel atonin, however, have to be taken into account in further studies.