Nocturnal excretion of a urinary melatonin metabolite among electric utility workers

Scand J Work Environ Health. 1998 Jun;24(3):183-9. doi: 10.5271/sjweh.297.


Objectives: The effects of 60-Hz magnetic field and ambient light exposures on the pineal hormone melatonin were studied among electric utility workers.

Methods: Personal exposure was measured at 15-second intervals over 3 consecutive 24-hour periods. Exposure metrics based on magnetic field intensity, intermittence, or temporal stability were calculated for periods of work, home, and sleep. A rate-of-change metric (RCM) was used to estimate intermittence, and the standardized RCM (RCMS = RCM/standard deviation) was used to evaluate temporal stability. The effects of magnetic field exposure on total overnight 6-hydroxymelatonin sulfate (6-OHMS) excretion and creatinine-adjusted nocturnal 6-OHMS (6-OHMS/cr) concentration were analyzed with adjustment for age, month, and light exposure.

Results: Magnetic field intensity, intermittence, or cumulative exposure had little influence on nocturnal 6-OHMS excretion. Residential RCMS magnetic field exposures were associated with lower nocturnal 6-OHMS/cr concentrations. In multivariate statistical analyses, the interaction term for geometric mean and RCMS magnetic field exposures at home was associated with lower nocturnal 6-OHMS/cr and overnight 6-OHMS levels. Modest reductions in the mean 6-OHMS levels occurred after RCMS exposures during work. The greatest reductions occurred when RCMS exposures both at work and at home were combined; therefore the effects of temporally stable magnetic fields may be integrated over a large portion of the day.

Conclusions: Results from this study provide evidence that temporally stable magnetic field exposures are associated with reduced nocturnal 6-OHMS excretion in humans.

Publication types

  • Clinical Trial
  • Controlled Clinical Trial
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Analysis of Variance
  • Biomarkers / urine
  • Circadian Rhythm
  • Electricity*
  • Electromagnetic Fields / adverse effects*
  • Environmental Monitoring / methods*
  • Humans
  • Male
  • Melatonin / analogs & derivatives*
  • Melatonin / urine*
  • Middle Aged
  • Occupational Exposure / adverse effects*
  • Reference Values
  • Workplace


  • Biomarkers
  • Melatonin
  • 6-hydroxymelatonin