Study type: Medical/biological study (experimental study)

The effects of different intensities, frequencies and exposure times of extremely low-frequency electromagnetic fields on the growth of Staphylococcus aureus and Escherichia coli O157:H7. med./bio.

Published in: Electromagn Biol Med 2015; 34 (1): 14-18

Aim of study (acc. to author)

The effects of exposure of bacteria to different extremely low frequency magnetic fields on cell growth should be investigated.

Background/further details

Bacteria of the strains, Staphylococcus aureus and E. coli, were each exposed to magnetic fields with every combination of 3 different frequencies (20, 40 and 50 Hz) and 2 different magnetic flux densities (2 and 4 mT) for 4 different durations (1, 2, 4 and 6 h). For each exposure condition, a separate sham exposure was conducted and each exposure and respective sham exposure condition was tested 2 times and 4 plates per replicate were counted.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 20 Hz
Exposure duration: continuous for 1, 2, 4 or 6 hours
Exposure 2: 40 Hz
Exposure duration: continuous for 1, 2, 4 or 6 hours
Exposure 3: 50 Hz
Exposure duration: continuous for 1, 2, 4 or 6 hours
Exposure 4: 20 Hz
Exposure duration: continuous for 1, 2, 4 or 6 hours
Exposure 5: 40 Hz
Exposure duration: continuous for 1, 2, 4 or 6 hours
Exposure 6: 50 Hz
Exposure duration: continuous for 1, 2, 4 or 6 hours

General information

the local geomagnetic field was measured as 32 ± 2.5 µT

Exposure 1

Main characteristics
Frequency 20 Hz
Type
Waveform
Exposure duration continuous for 1, 2, 4 or 6 hours
Exposure setup
Exposure source
Chamber Eppendorf tubes (1.5 ml)
Setup tubes were placed in the middle of the coils; temperature inside the coil was maintained at 25 ± 0.5°C; no significant temperature change was detected between the activated coils during the trials; the field was homogeneous with a maximum of ± 3.5% deviation
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 2 mT - measured - -

Exposure 2

Main characteristics
Frequency 40 Hz
Type
Waveform
Exposure duration continuous for 1, 2, 4 or 6 hours
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 2 mT - measured - -

Exposure 3

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration continuous for 1, 2, 4 or 6 hours
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 2 mT - measured - -

Exposure 4

Main characteristics
Frequency 20 Hz
Type
Waveform
Exposure duration continuous for 1, 2, 4 or 6 hours
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 4 mT - measured - -

Exposure 5

Main characteristics
Frequency 40 Hz
Type
Waveform
Exposure duration continuous for 1, 2, 4 or 6 hours
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 4 mT - measured - -

Exposure 6

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration continuous for 1, 2, 4 or 6 hours
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 4 mT - measured - -

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • before exposure
  • after exposure

Main outcome of study (acc. to author)

In both strains and independently from the applied frequency and intensity of the magnetic field, a general trend towards a decreasing cell growth with increasing exposure duration was observed. Except for the exposure duration of 1 hour, which showed inconsistent results, all cells exposed for 2, 4 or 6 hours to a field of 20, 40 or 50 Hz and 2 or 4 mT showed a significantly decreased cell growth compared to the sham exposed cells.
Exposure to a 20 Hz field of 4 mT for 6 h produced the largest decrease in cell growth compared to the sham exposed cells.
The authors conclude that exposure of bacteria to different extremely low frequency magnetic fields could retard cell growth as a function of time.

Study character:

Study funded by

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