Comment on “multivariable quantitative relation between cell viability and the exposure parameters of 9.33 GHz RF-EMP irradiation”

"Comment on “multivariable quantitative relation between cell viability and the exposure parameters of 9.33 GHz RF-EMP irradiation”." Electromagnetic Biology and Medicine, 41(1), pp. 118–119

Response to the comment

Dear Sir/Madam,

Thanks for the comment. I would interpret my ideas corresponding to the comment as follow.

In the comment, the equation

(1) $\mathrm{I}=\frac{E^2}{2c{\mu }_0}$(1)

was used to calculate the intensity of the electromagnetic wave, and the calculation result is $1.33\times {10}^{6}W/m^2$ . According to this calculation result, it is said that the wave energy is so huge (compared to Solar irradiance) that thermal effects caused the cell inhibition.

1. Please note that equation (1)(1) $\mathrm{I}=\frac{E^2}{2c{\mu }_0}$(1) is used to calculate the average energy that received per m² and per second when the incident wave is a continuous one. However, the wave used in our work is the pulsed wave. The maximum electric field intensity is 41.93 kV/m, the maximum pulse duration is 750 ns, and the maximum pulse number is 100. According to the calculation standard recommended, the average intensity within 6 min (according to the standard) should be:

(2) $\bar{I}=\frac{\mathrm{N}\tau \frac{E^2}{2c{\mu }_0}}{360}=\frac{100\times 750\times {10}^{-9}\times \frac{{\left(41.93\times {10}^3\right)}^2}{2\times 3\times {10}^8\times 12.57\times {10}^{-7}}}{360}\approx 0.5W/m^2$(2)

In the case of pulsed wave, the average intensity is not as high as it had been descried in the comment.

On another aspect, the photon energy of 9.33 GHz microwave is far smaller than that of the solar radiation. According to the equation

(2) $\mathrm{E}=\mathrm{h}\upsilon$(2)

The frequency (υ) of solar radiation is ranged from $4.0\times {10}^{14}{10}^{15}Hz$ (UV-visible light), much higher than the microwave used in this work ($9.33\times {10}^{9}Hz$). Therefore, from the photon energy point of view, the photon energy of 9.33 GHz microwave is much lower than that of the solar radiation.

The continuous microwave normally shows thermal effects on biosystem, and the effects of radiations on biological systems are well characterized. For pulsed electromagnetic wave, besides the thermal bioeffect, understanding the nonthermal effects is of more interests.¹ In our work, temperature raising of the cell culture medium has been monitored (figure 2 in the paper), it is found that when the pulse number is larger than 1000 (under the maximum electric intensity and pulse duration), significant temperature raising can be observed. Combined with the theoretical calculation result (Table 1 in the paper), the pulse number was limited 100, to ensure little significant macro-temperature-raising.

2. Es (maximum 41.93kV/m in this study) is the spatial electrical intensity of the wave. The actually electrical intensity that exert on the cells is not that high. We used XFDTD to calculate the inner electrical field intensity, and the specific energy absorption rate (SAR, W/kg) and total specific energy absorption (SA, J/kg) value were also be calculated. Though the SAR value is high (the electric field intensity is high), the SA value is not high enough to cause significant temperature raising.

3. Debashri Manna summarized reviewed the bioeffects caused by RF-EMF exposure. It is worth note that under the low SAR exposure condition($\le$10W/kg), the exposure time per day normally be several hours (at least decades of minutes), and the irradiation would last for days, weeks or even months.² Electric field intensity was seldom mentioned in these works except the SAR value. However, in our work, the irradiation finished within 1 second (only 100 pulses), and the bioeffect is dominated by electric field. In this case, low electric field intensity showed no significant bioeffect. There are some other reports on electromagnetic pulse irradiation concern to such high electric field intensity^3,4,5,6,7

Notes

¹ Debashri Manna & Rita Ghosh. Effect of radiofrequency radiation in cultured mammalian cells: A review. Electromagnetic Biology and Medicine, (2016). DOI:10.3109/15368378.2015.1092158.

² Ju Hwan Kim, Choong-Hyun Lee, Hyung-Gun Kim and Hak Rim Kim. Decreased dopamine in striatum and difficult locomotor recovery from MPTP insult after exposure to radiofrequency electromagnetic fields. Scientific Reposrts, 9, article number:1201 (2019).

³ Li, K. C., Ma, S. R., Ding, G. R. Effect of EMP on one formation of MC3T3-E1 cells. International Symposium on Antennas, Propagation and Em Theory, Kunming, China: IEEE: 895–897 (2009). doi 10.1109/ISAPE.2008.4735362.

⁴ Jauchem, JR; Ryan, KL; Frei, MR et.al., Repeated exposure of C3H/HeJ mice to ultra-wideband electromagnetic pulses: lack of effects on mammary tumors. RADIATION RESEARCH, 155(2): 369–377 (2001).

⁵ X.W. Wang, G.R. Ding, C.H. Shi, T. Zhao, J. Zhang, L.H. Zeng, G.Z.Guo, Effect of Electromagnetic Pulse Exposure on Permeability of Blood-testicle Barrier in Mice. Biochemical and Environmental. Sciences 21: 218–221(2008).

⁶ Yong Bin Chen, Jing Li, Jun Ye Liu, Li Hua Zeng, Yi Wan, Yu Rong Li, Dongqing Ren & G. Z. Guo. Eff ect of Electromagnetic Pulses (EMP) on associative learning in mice and a preliminary study of mechanism. International Journal of Radiation Biology, December 2011; 87(12): 1147–1154.

⁷ Gary L. Thompson, Caleb C. Roth, Marjorie A. Kuipers, Gleb P. Tolstykh, Hope T. Beier, Bennett L. Ibey. Permeabilization of the nuclear envelope following nanosecond pulsed electric field exposure. Biochemical and Biophysical Research Communications 470 (2016) 35e40.