EMF Health-effects Research

Primary DNA Damage in Human Blood Lymphocytes Exposed In Vitro to 2450 MHz Radiofrequency

Vijayalaxmi, Leal BZ, Szilagyi M, Prihoda TJ, Meltz ML

Radiation. Radiat Res 153(4):479-486, 2000

Human peripheral blood samples collected from three healthy human volunteers were exposed in vitro to pulsed-wave 2450 MHz radiofrequency (RF) radiation for 2 h. The RF radiation was generated with a net forward power of 21 W and transmitted from a standard gain rectangular antenna horn in a vertically downward direction. The average power density at the position of the cells in the flask was 5 mW/cm2. The mean specific absorption rate, calculated by finite difference time domain analysis, was 2.135 (+/-0.005 SE) W/kg. Aliquots of whole blood that were sham-exposed or exposed in vitro to 50 cGy of ionizing radiation from a (137)Cs gamma-ray source were used as controls.

The lymphocytes were examined to determine the extent of primary DNA damage (single-strand breaks and alkali-labile lesions) using the alkaline comet assay with three different slide-processing schedules. The assay was performed on the cells immediately after the exposures and at 4 h after incubation of the exposed blood at 37 +/- 1 degrees C to allow time for rejoining of any strand breaks present immediately after exposure, i.e. to assess the capacity of the lymphocytes to repair this type of DNA damage. At either time, the data indicated no significant differences between RF-radiation- and sham-exposed lymphocytes with respect to the comet tail length, fluorescence intensity of the migrated DNA in the tail, and tail moment. The conclusions were similar for each of the three different comet assay slide-processing schedules examined. In contrast, the response of lymphocytes exposed to ionizing radiation was significantly different from RF-radiation- and sham-exposed cells.

Thus, under the experimental conditions tested, there is no evidence for induction of DNA single-strand breaks and alkali-labile lesions in human blood lymphocytes exposed in vitro to pulsed-wave 2450 MHz radiofrequency radiation, either immediately or at 4 h after exposure.

Additional Web Notes

Comment by SF: I wrote to Dr Henry Lai to ask about this attempt by the US Airforce to replicate his research, and this was his reply:

The main point is that in their experiment DNA migration is not linear with time of electrophoresis. This suggests that they did not do the assay properly.

They exposed human whole blood to 2450 MHz microwaves and found no effect on DNA using the comet assay. They claimed that the assay method used was similar to that we used in our experiments. However, for some unknown reason, they didn't followed exactly our protocol.

There were several very important differences.

  • They put 10% DMSO in the assay solution and then digested the cells with the enzyme Proteinase-K. We have found that the Protainase-K step is very important in showing the DNA effect of RFR. However, Protainase-K cannot work in the presence of DMSO.
  • They also used a much less sensitive dye (ethidium bromide, at least one order of magnitude less sensitive) to stain the DNA. We used the dye YOYO-1.
  • They used a very high voltage to do the electrophoresis. This reduces the resolution and sensitivity of the assay.
  • They also did not put an antioxidant in the electrophoretic solution. Antioxidant reduces the background of DNA damage.

Thus, one would expect that the assay protocol they used is less sensitive. However, their data actually showed that it was claimed to be more sensitive. They claimed a two-fold increase in DNA migration in their positive controls when cells were irradiated with 50 rads of ionizing radiation.

Remember, NP [Dr Singh] can only detect 25 rads in whole blood exposure.

Another very interesting result reported in the paper is that they showed DNA migrated for about 30 microns after 20 minutes of electrophoresis. Then, for an additional 10 minutes of electrophoresis, DNA suddenly moved another 100 microns.


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