Medical/biological study (experimental study)

Geomagnetic activity and human melatonin metabolite excretion med./bio.

By: Burch JB, Reif JS, Yost MG

Published in: Neurosci Lett 2008; 438 (1): 76-79

Aim of study (acc. to author)

To evaluate the relationship between geomagnetic activity and overnight excretion of the melatonin metabolite, 6-hydroxymelatonin sulfate, and potential modifications by ambient light and 60 Hz MF exposure among male electric utility workers.

Background/further details

61 participants worked in the field of electric power distribution, 51 worked in electric generation and 41 were comparison workers. Collected data on total noctural urine output from 1997 and 1995 were analysed. Geomagnetic activity, 60 Hz magnetic field and ambient light exposures were summerized over 3 h, 24 h and 36 h intervals.

Endpoint

endocrine changes: overnight melatonin metabolite excretion

Exposure

- 50/60 Hz
- geomagnetic field
- occupational

Exposure	Parameters
Exposure 1: DC/static Exposure duration: 3 h, 24 h, 36 h	-

General information

also a combination either of geomagnetic field and 60 Hz exposure or of geomagnetic field and ambient light exposure was evaluated

Exposure 1

Main characteristics

Frequency	DC/static
Type	magnetic field
Exposure duration	3 h, 24 h, 36 h

Exposure setup

Parameters

No parameters are specified for this exposure.

Exposed system:

human
whole body

Methods Endpoint/measurement parameters/methodology

endocrine changes: overnight melatonin metabolite excretion: urinary 6-hydroxymelatonin sulphate concentration

Investigated system:

urine sample

Investigated organ system:

endocrine system

Time of investigation:

during exposure

Main outcome of study (acc. to author)

Elevated geomagnetic activity was associated with reduced melatonin metabolite excretion. There was no combined effect of 60 Hz magnetic field exposure with geomagnetic activity. There was little evidence for the combination of low ambient light exposures and elevated geomagnetic activity being associated with reduced 6-hydroxymelatonin sulphate levels. Time intervals in which geomagnetic activity predicted the largest differences in 6-hydroxymelatonin sulphate excretion occurred between 15 and 33 h prior to urine sample collection, which coincides with key periods of melatonin regulation.
The authors suggest that geomagnetic activity may play a role in the entrainment of human melatonin rhythm.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Department of Veterans Affairs (VA), USA
National Institute of Environmental Health Sciences/National Institute of Health (NIEHS/NIH), USA
Platte River Power Authority (PRPA), USA

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