The effects of exposure of different cell lines to 60 Hz electric fields on DNA damage and cell viability should be investigated.
The study was based on two previous studies by the authors (Kim et al. (2012) and Kim et al. (2010)) and should clarify whether the magnetic field or the electric field had been responsible for the effects observed in the previous studies.
Human tongue squamous carcinoma cells (SCC25), human adenocarcinoma (HeLa) cells and human lung fibroblast (IMR90) were exposed to electric fields generated by two different devices: one device generated a field parallel to the surface of the culture dishes and the other device generated a perpendicular field.
SCC25 cells were exposed to the perpendicular electric field for 30 minutes. HeLa and IMR90 cells were continuously exposed to the parallel field for 10 min to 144 hours. Moreover, HeLa and IMR90 cells were exposed to the parallel field for 30 minutes per day over 1-3 consecutive days. For each exposure condition a separate unexposed control group was used.
A positive control was conducted.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
60 Hz
Exposure duration:
continuous for 30 minutes
perpendicular field
|
|
|
Exposure 2:
60 Hz
Modulation type:
pulsed
Exposure duration:
continuous for 10 minutes to 144 hours
parallel field
|
|
|
Exposure 3:
60 Hz
Modulation type:
pulsed
Exposure duration:
continuous for 30 minutes/day over 1-3 days
parallel field
|
|
for the positive control, cells were exposed to UVC radiation for 2 minutes (50 J/m2)
| Frequency | 60 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | continuous for 30 minutes |
| Additional info | perpendicular field |
| Exposure source | |
|---|---|
| Setup | the device was composed of two facing electrodes parallel to the dishes; the powered electrode was located at the bottom surface and the four grounded electrodes were connected to a sinusoidal voltage source with a frequency of 60 Hz; for safety, the powered electrode was covered with white dielectric material with a relative permittivity of 10 and a thickness of 0.18 mm; four dishes were used at the same time for one experimental set; the direction of the electric field was perpendicular to the dish surface |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| electric field strength | 10 kV/m | maximum | estimated | - | in the medium |
| electric field strength | 750 kV/m | peak value | - | - | in the air |
| Frequency | 60 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | continuous for 10 minutes to 144 hours |
| Additional info | parallel field |
| Modulation type | pulsed |
|---|---|
| Duty cycle | 25 % |
| Pulse type | biphasic |
| Exposure source | |
|---|---|
| Chamber | CO2 incubator |
| Setup | the device consisted of two electrodes of 2 cm width and of 12 cm length covered on the bottom side of a plane glass; the left-side electrode was powered by a bipolar voltage source and the right-side electrode was grounded; the gap distance was 1 cm; the thickness and the relative permittivity of the glass were 3 mm and 4.2, respectively; for safety, the electrodes were covered with white dielectric material with a relative permittivity of 10 and a thickness of 0.18 mm; culture dishes were located on the top of the glass so the center of the dish was at the center of the gap; three dishes were used for one experimental set; the temperature was maintained at 36.7 - 37.1°C |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| electric field strength | 16 kV/m | maximum | calculated | - | at the center of the culture dish |
| electric field strength | 10 kV/m | spatial average | calculated | - | in the culture dish |
| Frequency | 60 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | continuous for 30 minutes/day over 1-3 days |
| Additional info | parallel field |
| Modulation type | pulsed |
|---|---|
| Duty cycle | 25 % |
| Pulse type | biphasic |
| Exposure source |
|
|---|
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| electric field strength | 16 kV/m | maximum | calculated | - | at the center of the culture dish |
| electric field strength | 10 kV/m | spatial average | calculated | - | in the culture dish |
Exposure of the different cells strains to either exposure system did not cause any significant differences between exposed cells and the respective cells of the control group.
The authors conclude that exposure of different cell lines to 60 Hz electric fields does not induce DNA damages and has no effect on the cell viability. Therefore, the effects reported in the previous studies can be attributed to the magnetic field.
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