title: Geomagnetic disturbances are associated with reduced nocturnal excretion of a melatonin metabolite in humans.
abstract: The effects of geomagnetic disturbances on urinary excretion of the melatonin metabolite, 6-hydroxymelatonin sulfate (6-OHMS), were studied in conjunction with 60 Hz magnetic field (MF) and ambient light exposure in 132 electric utility workers. Geomagnetic activity was assessed using a local (equivalent amplitude or A(K), Boulder, CO) and global (average antipodal or aa) index. Personal exposures to 60 Hz MFs and light were obtained using data-logging meters. The relationship between geomagnetic activity and 6-OHMS was assessed with adjustment for age, light exposure, and month of participation. Mean overnight 6-OHMS excretion was lower on days when the 36-h A(K) or aa values exceeded 30 nT. A greater reduction in 6-OHMS excretion was observed when increased geomagnetic activity was combined with elevated 60 Hz MF or reduced ambient light exposures.
authors.affiliation: Department of Environmental Health, Colorado State University, Fort Collins 80523, USA.
authors.forename: J B
authors.initials: JB
authors.lastname: Burch
authors.forename: J S
authors.initials: JS
authors.lastname: Reif
authors.forename: M G
authors.initials: MG
authors.lastname: Yost
mesh_terms: D002940:Circadian Rhythm / Q000502:physiology*; D004574:Electromagnetic Fields / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008550:Melatonin / Q000031:analogs & derivatives* / Q000652:urine; D016273:Occupational Exposure; D010775:Photic Stimulation
chemical_list: D008550:Melatonin; C012365:6-hydroxymelatonin