A single nocturnal exposure to 2-7 millitesla static magnetic fields does not inhibit the excretion of 6-sulfatoxymelatonin in healthy young men

The present study sought to evaluate possible acute effects on 6-sulfatoxymelatonin (aMT6s) excretion, a surrogate for melatonin levels in blood, in volunteers exposed to static magnetic fields with flux densities representative for workers in light metal reduction plants and operators of medical MRI in hospitals. Eleven healthy male volunteers (23-43 years) participated. Urine samples were collected for two consecutive 24 h periods from 22:00 hours day 1 (exposure day) through day 2 (day after exposure) and then for 24 h from 07:00 hours on day 7 (control day). On the day of exposure the subjects slept in the MRI room from 22:00 hours until 07:00 hours next morning, thus receiving a 9 h exposure to the magnetic field (2-7 mT). On the day after exposure and on the control day, they slept at home and otherwise performed their ordinary daily activities. Total daily urine production was collected in four parts: 22:00-07:00 hours, 07:00-11:00 hours, 11:00-18:00 hours, 18:00-22:00 hours, and the volume for each interval was measured and recorded. Samples were transferred to coded bottles and frozen for later RIA analysis of aMT6s. Pairs of values of mean hourly aMT6s excretion, both diurnal and for the four daily intervals, were compared using two-sided Wilcoxon signed ranks test. The day of exposure and the day after exposure were not significantly different from the control day, either for the total diurnal secretion or the interval data. In summary, the study shows no association between a single nocturnal exposure to a static magnetic field of strength 2-7 mT and excretion of aMT6s in urine.