Effect of occupational exposure to magnetic fields on 6-hydroxymelatonin sulfate excretion

Background. Decreased melatonin (a noted antioxidant and oncostatic agent) has been associated with electric and magnetic field (EMF) exposed workers in some studies but not in others. Evidence suggests variations in the individual melatonin response to EMF exposure may be important [Graham, 1996; Davis, 2001]. The mixed results in previous studies could be explained by a lack of accounting for inter-individual variation in response to EMF.;The U.S. Army Apache aircraft electrical systems are extensive. The cockpit EMF exposures of such aircraft have never been recorded. The melatonin levels associated with such exposures have also never been documented.;Objectives. The main objective of this research was to investigate the association between human urinary 6-hydroxymelatonin sulfate (6-OHMS) levels and the occupational EMF exposures in U.S. Army Apache pilots and non-pilots at Fort Rucker, Alabama.;Methods. Melatonin was obtained through urine samples provided by volunteers on the mornings following the last off-work day (Monday morning) and the last day (Friday morning) of the week. Pilot and non-pilot volunteers wore personal EMF exposure dosimeters throughout the week of study. Information on physiologic or lifestyle factors known to affect melatonin was assessed through questionnaires. Pilot group was examined as a predictor of melatonin outcomes. Magnetic field exposure as a predictor of melatonin was also investigated.;Results. Pilots and non-pilots had similar geometric mean magnetic field exposures. Results suggested a negative correlation in the individual 6-OHMS weekly concentration differences with geometric mean magnetic field exposures. The potential for cumulative effects of magnetic field exposure on 6-OHMS was also noted. Additional associations between melatonin and some physiologic/lifestyle factors were also noted. The intea-individual 6-OHMS weekly changes were independent of pilot group and the magnetic field rate of change (RCMS).;Conclusions. The mixed results in previous studies using between-group comparisons could be explained by a lack of accounting for variation in inter-individual melatonin response to EMF. Although the long-term effects of melatonin changes in relation to disease, such as cancer, are unknown, demonstration of biologic effects at such low, residentially relevant field strengths could have great public health significance.