Study type: Medical/biological study (experimental study)

Human acute neurophysiological perceptions associated with ELF flux densities up to 50 mT. med./bio.

Published in: 2019 IEEE Radio and Antenna Days of the Indian Ocean (RADIO), Reunion IEEE, 2019: 1-2, ISBN 9781728122991

Aim of study (acc. to author)

The effects of exposure to extremely low frequency magnetic fields on magnetophosphene perceptions should be investigated.

Background/further details

A total of 81 volunteers (18-55 years) were divided into the following groups: exposure to a magnetic field of 1) 20 Hz (n=20), 2) 50 Hz (n=21), 3) 60 Hz (n=20) and 4) 100 Hz (n=20). Each subject was tested in 11 exposure periods. The magnetic flux density ranged from 0 to 50 mT with 5 mT increments, and each exposure period was followed by 5 seconds of rest without exposure. The order of the exposures was randomly assigned by a computer program. The volunteers were sitting in the dark (adaptation time = 5 min) with eyes closed and they used a button-press to report magnetophosphene perception.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 20 Hz
Exposure duration: 11 x 5 seconds
Exposure 2: 50 Hz
Exposure duration: 11 x 5 seconds
Exposure 3: 60 Hz
Exposure duration: 11 x 5 seconds
Exposure 4: 100 Hz
Exposure duration: 11 x 5 seconds

Exposure 1

Main characteristics
Frequency 20 Hz
Type
Exposure duration 11 x 5 seconds
Exposure setup
Exposure source
Chamber participants were sitting in the dark (adaptation time = 5 min) with the eyes closed
Setup exposure system consisted of two 99-turn coils (11 turns of 9 layers), made with square copper wire cooled with circulating water, the coils had a 356 mm inner diameter and a 501 mm outer diameter and were arranged in a Helmholtz coil-like manner, enabling the generation of a homogenous MF (± 5%) over the head; a motorized non-magnetic lift enabled vertical movement of the coil system such that the participant's eyes could be centered between the coils
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 0 mT effective value measured - lowest magnetic flux density
magnetic flux density 50 mT effective value measured - highest magnetic flux density

Exposure 2

Main characteristics
Frequency 50 Hz
Type
Exposure duration 11 x 5 seconds
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 0 mT effective value measured - lowest magnetic flux density
magnetic flux density 50 mT effective value measured - highest magnetic flux density

Exposure 3

Main characteristics
Frequency 60 Hz
Type
Exposure duration 11 x 5 seconds
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 0 mT effective value measured - lowest magnetic flux density
magnetic flux density 50 mT effective value measured - highest magnetic flux density

Exposure 4

Main characteristics
Frequency 100 Hz
Type
Exposure duration 11 x 5 seconds
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 0 mT effective value measured - lowest magnetic flux density
magnetic flux density 50 mT effective value measured - highest magnetic flux density

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • during exposure

Main outcome of study (acc. to author)

Results showed frequency-dependent thresholds for initial perception of 2.51 T/s at 20 Hz (group 1), 6.28 T/s at 50 Hz (group 2), 7.54 T/s at 60 Hz (group 3), and 12.57 T/s at 100 Hz (group 4) and for the 50% detection rate 4.73 T/s at 20 Hz, 8.83 T/s at 50 Hz, 10.55 T/s at 60 Hz, and 33.46 T/s at 100 Hz.
The authors conclude that magnetophosphene perception sensivity was greater at lower frequencies of magnetic field exposure.

Study character:

Study funded by

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