To study the effects of power frequency magnetic fields on heart rate and heart rate variability in groups of adult volunteers.
The study was carried out in two parts: a pilot study and a follow-up study. The aim of the pilot study was to provide an independent replication of the data of a previous study (Graham C, Cohen HD, Cook MR, Phelps JW, Gerkovich MM, Fotopoulos SS. A double-blind evaluation of 60 Hz field effects on human performance. In: Anderson LE et al, editor. Interaction of Biological Systems with Static and ELF Electric and Magnetic Fields. CONF-841041. Springfield (VA):NTIS, 1987:471-86). Graham et al. observed that exposure to occupational level of electromagnetic fields cause slowing of heart rate in laboratory experiments with human volunteers.
The follow-up study was designed to confirm the results of the pilot study and to investigate further possible interaction of short (a few minutes) magnetic field exposure on the spectral content of heart rate variability signal.
There were two data collection periods in which there was either an actual field applied followed bei a sham exposure, or these in the reverse order.
Exposure | Parameters |
---|---|
Exposure 1:
50 Hz
Exposure duration:
continuous for 100 or 150 s
|
|
Exposure 2:
50 Hz
Exposure duration:
intermittent, 15 s on/15 s off for 100 or 150 s
|
|
Exposure 3:
50 Hz
Modulation type:
pulsed
Exposure duration:
continuous for 100 or 150 s
|
|
Exposure 4:
50 Hz
Modulation type:
pulsed
Exposure duration:
intermittent, 15 s on/15 s off for 100 or 150 s
|
Frequency | 50 Hz |
---|---|
Type | |
Waveform | |
Polarization |
|
Exposure duration | continuous for 100 or 150 s |
Measurand | Value | Type | Method | Mass | Remarks |
---|---|---|---|---|---|
magnetic flux density | 20 µT | effective value | measured | - | - |
Frequency | 50 Hz |
---|---|
Type | |
Waveform | |
Polarization |
|
Exposure duration | intermittent, 15 s on/15 s off for 100 or 150 s |
Exposure source |
|
---|
Measurand | Value | Type | Method | Mass | Remarks |
---|---|---|---|---|---|
magnetic flux density | 20 µT | effective value | measured | - | - |
Frequency | 50 Hz |
---|---|
Type | |
Waveform |
|
Polarization |
|
Exposure duration | continuous for 100 or 150 s |
Modulation type | pulsed |
---|---|
Rise time | 1.6 ms |
Exposure source |
|
---|
Measurand | Value | Type | Method | Mass | Remarks |
---|---|---|---|---|---|
magnetic flux density | 20 µT | effective value | measured | - | - |
Frequency | 50 Hz |
---|---|
Type | |
Waveform |
|
Polarization |
|
Exposure duration | intermittent, 15 s on/15 s off for 100 or 150 s |
Modulation type | pulsed |
---|---|
Rise time | 1.6 ms |
Exposure source |
|
---|
Measurand | Value | Type | Method | Mass | Remarks |
---|---|---|---|---|---|
magnetic flux density | 20 µT | effective value | measured | - | - |
A small but significant slowing of heart rate was revealed in two separate studies in which the fields were generated by continuous sinusoidal currents. Magnetic fields generated by square-wave currents or by currents turned alternatively on and off at 15 second intervals during the exposure period produced inconsistent effects on heart rate.
Analysis of the heart rate variability spectra in relation to continuous sinusoidal exposure revealed a consistent reduction in the ratio of power in the Low Band (0.02-0.15 Hz) to the High Band (0.16-1.0 Hz). This reduction in ratio was significant for experiments in which respiration was controlled at 0.2 Hz (12 breaths/minute) where the order was actual exposure followed by sham exposure (On --> Off). The spectral power in the Low Band was significantly reduced for both orders, but the High Band power was significantly raised only for the On --> Off order.
Although there are some inconsistencies, these findings indicate that short exposures to magnetic fields at occupational levels may influence heart rate control mechanisms.
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