Study type: Medical/biological study (experimental study)

Time-varying magnetic fields of 60 Hz at 7 mT induce DNA double-strand breaks and activate DNA damage checkpoints without apoptosis. med./bio.

Published in: Bioelectromagnetics 2012; 33 (5): 383-393

Aim of study (acc. to author)

To study the biological effects and potential genotoxicity of exposure to 60 Hz time-varying magnetic fields of 2-14 mT on human primary cells and cancer cells.

Background/further details

The cells were investigated immediately or 24 h following exposure. Positive controls were performed with UVC radiation (for apoptosis and DNA double-strand breaks) and TBHP (tert-butyl hydroperoxide; for the induction of reactive oxygen species).
The authors also compared the position and time dependency of DNA double-strand breaks with numerical simulation of the magnetic fields. The Lorentz force and eddy currents in these experiments were numerically calculated to investigate the influence of each factor on the double-strand breaks.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 60 Hz
Exposure duration: continuous for 30 min
Exposure 2: 60 Hz
Exposure duration: continuous for 0 - 120 min

Exposure 1

Main characteristics
Frequency 60 Hz
Type
Exposure duration continuous for 30 min
Exposure setup
Exposure source
Setup circular coils with a diameter of 0.9 cm and 3500 turns of wire wound on an acrylic cylinder; cell culture dish with a diameter of 3.5 or 6 cm placed so at the coil's base that the coil was in the center of the dish
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 2 mT minimum measured - -
magnetic flux density 14 mT maximum measured - -
power 400 mW maximum - - 5 - 400 mW

Exposure 2

Main characteristics
Frequency 60 Hz
Type
Exposure duration continuous for 0 - 120 min
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 7 mT - measured - measured at 4 mm from the bottom of the cell culture dish
power 400 mW maximum - - 5 - 400 mW

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated material:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

Upon continuous exposure of human fibroblast and cervical cancer cells to a 60 Hz magnetic field at 7 mT for 0-120 minutes, no significant change in cell viability was observed. Cell viability of the two cell lines was also not altered by magnetic fields of 0-14 mT at an exposure time of 30 minutes.
However, DNA double-strand breaks were detected in both cell lines exposed to 7 mT or at higher intensities for 30 or 60 minutes (as shown by formation of gamma-H2AX foci and/or gamma-H2AX expression and comet assay). The DNA damage checkpoint pathway was activated in these cells (as shown by protein expression of phospho-ATM and p-Chk2) without programmed cell death (apoptosis; as shown by no change in expression of caspase-3, cleaved caspase-3 and PARP).
The exposure of the cell lines to a 60 Hz magnetic field did not induce intracellular reactive oxygen species production, suggesting that the observed DNA double-strand breaks were not directly caused by reactive oxygen species.
The DNA double-strand breaks mainly occurred at the central region of the culture plates, where the magnetic field was strongest, after a 30 minutes exposure. After 90 minutes, however, the amount of double-strand breaks increased rapidly in the outer regions, where the eddy current and Lorentz force were strong.
In conclusion, the data suggest that exposure to a 60 Hz magnetic field of 2-14 mT has a genotoxic potential in both human non-cancerous and cancerous cells even after short exposures of tens of minutes.

Study character:

Study funded by

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