title: Melatonin metabolite excretion among cellular telephone users.
abstract: OBJECTIVE
  The relationship between cellular telephone use and excretion of the melatonin metabolite 6-hydroxymelatonin sulfate (6-OHMS) was evaluated in two populations of male electric utility workers (Study 1, n=149; Study 2, n=77).
  
  
  METHODS
  Participants collected urine samples and recorded cellular telephone use over 3 consecutive workdays. Personal 60-Hz magnetic field (MF) and ambient light exposures were characterized on the same days using EMDEX II meters. A repeated measures analysis was used to assess the effects of cellular telephone use, alone and combined with MF exposures, after adjustment for age, participation month and light exposure.
  
  
  RESULTS
  No change in 6-OHMS excretion was observed among those with daily cellular telephone use >25 min in Study 1 (5 worker-days). Study 2 workers with >25 min cellular telephone use per day (13 worker-days) had lower creatinine-adjusted mean nocturnal 6-OHMS concentrations (p=0.05) and overnight 6-OHMS excretion (p=0.03) compared with those without cellular telephone use. There was also a linear trend of decreasing mean nocturnal 6-OHMS/creatinine concentrations (p=0.02) and overnight 6-OHMS excretion (p=0.08) across categories of increasing cellular telephone use. A combined effect of cellular telephone use and occupational 60-Hz MF exposure in reducing 6-OHMS excretion was also observed in Study 2.
  
  
  CONCLUSIONS
  Exposure-related reductions in 6-OHMS excretion were observed in Study 2, where daily cellular telephone use of >25 min was more prevalent. Prolonged use of cellular telephones may lead to reduced melatonin production, and elevated 60-Hz MF exposures may potentiate the effect.
authors.affiliation: Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO 80523, USA. james.burch@colostate.edu
authors.forename: J B
authors.initials: JB
authors.lastname: Burch
authors.forename: J S
authors.initials: JS
authors.lastname: Reif
authors.forename: C W
authors.initials: CW
authors.lastname: Noonan
authors.forename: T
authors.initials: T
authors.lastname: Ichinose
authors.forename: A M
authors.initials: AM
authors.lastname: Bachand
authors.forename: T L
authors.initials: TL
authors.lastname: Koleber
authors.forename: M G
authors.initials: MG
authors.lastname: Yost
mesh_terms: D000293:Adolescent; D000328:Adult; D040421:Cell Phone; D004307:Dose-Response Relationship, Radiation; D004559:Electric Wiring; D004574:Electromagnetic Fields; D006801:Humans; D008027:Light; D008297:Male; D008550:Melatonin / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000378:metabolism* / Q000652:urine*; D008875:Middle Aged; D011210:Power Plants; D011846:Radio Waves; D013997:Time Factors
chemical_list: C054513:6-sulfatoxymelatonin; D008550:Melatonin