Magnetic fields and pineal function in humans: evaluation of nocturnal acute exposure to extremely low frequency magnetic fields on serum melatonin and urinary 6-sulfatoxymelatonin circadian rhythms.

Exposure to a 50/60-Hz electromagnetic field can decrease the nocturnal production of melatonin in rodents. Melatonin is considered to be a marker of circadian rhythms, and abnormalities in its secretion are associated with clinical disorders, including fatigue, sleep disruption, mood swings, impaired performance, and depression, which are consequences of desynchronisation. Interestingly, some epidemiological studies have been reported finding most of these clinical disorders in individuals living or working in an environment exposed to electromagnetic fields. This experiment was designed to look for the possible effects of acute exposure (9 hours) to 50-Hz linearly polarized magnetic fields (10 mu T) on the pineal function. Thirty-two young men (20-30 years old) were divided into two groups (control group, i.e., sham-exposed: 16 subjects; exposed group: 16 subjects). All subjects participated in two 24-hour experiments to evaluate the effects of both continuous and intermittent exposure to linearly polarized magnetic fields. They were synchronized with a diurnal activity from 08:00 to 23:00 and nocturnal rest. The experiment lasted two months (mid-February to mid-April). The subjects were exposed to the magnetic fields (generated by three Helmholtz coils per bed) from 23:00 to 08:00, while lying down. Blood samples were collected during each session at 3-hour intervals from 11:00 to 20:00 and hourly from 22:00 to 08:00. Total urine was collected every 3 hours from 08:00 to 23:00 and once during the night, from 23:00 to 08:00. The levels of serum melatonin and its metabolite in urine (6-sulfatoxymelatonin) in exposed men did not differ significantly from those in control (sham-exposed) subjects. This study shows that nocturnal acute exposure to either continuous or intermittent 50-Hz linearly polarized magnetic fields of 10 mu T does not affect melatonin secretion in humans.