Study type: Medical/biological study (observational study)

ECG changes in humans exposed to 50 Hz magnetic fields. med./bio.

Published in: J Occup Health 2005; 47 (5): 391-396

Aim of study (acc. to author)

1) To measure the strength of the magnetic field produced by power transformer stations.
2) To use these magnetic field data and additional data collected on the patterns of exposure to estimate subjects' exposure in power transformer stations.
3) To determine whether the exposure levels exhibited dose-response patterns that might influence the ECG.

Background/further details

A total of 59 subjects (transformer substation workers), divided into three independent magnetic field strength groups, were compared. ECGs were recorded in the resting position at the Occupational Health Centre (not at workplace).

Endpoint

Exposure

Exposure Parameters
Exposure 1: 50 Hz
Exposure duration: daily exposure of 12 h for at least 5 years
location 1
Exposure 2: 50 Hz
Exposure duration: daily exposure of 12 h for at least 5 years
location 2
Exposure 3: 50 Hz
Exposure duration: daily exposure of 12 h for at least 5 years
location 3

Exposure 1

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration daily exposure of 12 h for at least 5 years
Additional info location 1
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 0.067 µT average over time estimated - -

Exposure 2

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration daily exposure of 12 h for at least 5 years
Additional info location 2
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1.18 µT average over time estimated - -

Exposure 3

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration daily exposure of 12 h for at least 5 years
Additional info location 3
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 5.2 µT average over time estimated - -

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

The data suggest that the relationship between field strength and response is non-linear. The adjusted mean QTc values are similar between the "low" exposure and the "high" exposure, but significantly lower in the "medium" group.
The authors' interpretation of the results is that a specific exposure pattern might be responsible for the non-linear effects, so that generally, characterizing exposure to electric and magnetic fields using simple metrics such as time-weighted average (TWA) may be insufficient.

Study character:

Study funded by

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