The main topics selected for the Special Issue cover some of important aspects of the area: physical and biological mechanisms of radiofrequency radiation effects by Hinrikus et al. and Herrala et al.; response to microwave radiation in physiological systems by Selmanoui et al. and Bachmann et al.; reproductive effects of intermediate frequency magnetic field by Khan et al.; low-frequency magnetic field effect on immune response by Wyszkowska et al. Special attention has been paid to medical applications of EMF including safety problems for implants in two papers by Zradzinski et al.; connectivity between surface and deep bioelectric fields in brain by Jäntti et al.; and practical use of EMF for toxicity assessment of biological suspensions by Muñoz et al....
The ongoing discussions about 5G technology are based on a presumption that, due to very thin skin-layer, the EMF effect occurs only in human skin. However, in the case of real living systems, the processes in different tissues are interconnected. Therefore, excited by EMF skin structures are physiologically connected to deeper systems in body and the affected space can be much deeper....
All experimental studies published in the Special Issue have been performed at the EMF levels lower than the reference levels for general public set by the ICNIRP. An only exception is the SAR value of 6 W/kg used as the higher level of exposure in the study by Herrala et al.
The ICNIRP Guidelines are based on thermal interaction mechanism for the RF EMF effects. Therefore, the rise of temperature inside tissue is the only criterion for the possibility of an EMF effect. The specific absorption rate (SAR) is a relevant parameter to describe the intensity of exposure in the case of thermal mechanism. The SAR value, corresponding to the fixed level of induced by EMF increase of temperature, can be considered as the threshold of the EMF effect induced by the thermal interaction mechanism.
In the case of non-thermal interaction mechanisms, the absorbed energy has no more direct linear relationship with the effect. Therefore, SAR becomes irrelevant as a parameter describing the threshold of the EMF effects. Parallel to SAR, the ICNIRP has set the reference levels for electric and magnetic fields strengths and EMF power spectral density, more relevant in the case of nom-thermal interaction mechanisms. Do the reference levels for EM field strengths set by ICNIRP determine the threshold of the non-thermal mechanism of EMF effects?
Rotations of dipolar molecules and radical pairs are known to be evident at the EMF strengths much less than the thermal threshold. The dielectric constant is assumed being constant, therefore, no threshold for dielectric polarization of a medium is expected at low-level exposure. The rotation of dipolar molecules can occur at very weak EMF. Radical pairs are known being sensitive to very weak magnetic fields, for example in birds. In the case of the rotation of dipolar molecules or radical pairs, the physical restrictions determining the minimal field strengths sufficient for the rotation are still unknown.
The threshold of the non-thermal mechanisms of EMF effects needs further theoretical and experimental investigations keeping in mind that the additional affecting factors can influence the threshold of low-level EMF. The oscillating nature of several biological structures, first of all, heart cells and neurons, makes possible parametric excitation of biological oscillations even by very weak periodic external EMF. The impact of parametric excitation depends not only on the strength of periodic force but rather more on the duration of excitation. Chaotic nature of biological systems creates a possibility that a very small initial change in a parameter of the system can cause remarkable alterations of the ongoing processes and finally results in a significant change in the status of the system. Due to diversity of living systems, the sensitivity to low-level EMF is expected to be different for individuals.
Herrala M, Mustafa E, Naarala J, Juutilainen J. Assessment of genotoxicity and genomic instability in rat primary astrocytes exposed to 872 MHz radiofrequency radiation and chemicals. Int J Radiat Biol. 2018 Oct;94(10):883-889. doi: 10.1080/09553002.2018.1450534. Epub 2018 Mar 23.
PURPOSE: We examined genotoxicity, co-genotoxicity and induced genomic instability (IGI) in primary astrocytes exposed to radiofrequency (RF) radiation.
MATERIALS AND METHODS: Rat primary astrocytes were exposed to 872 MHz GSM-modulated or continuous wave (CW) RF radiation at specific absorption rates of 0.6 or 6.0 W/kg for 24 h. Menadione (MQ) and methyl methanesulfonate (MMS; only in genotoxicity experiments) were used as co-exposures. Alkaline Comet assay and flow cytometric micronucleus scoring were used to detect genetic damage.
RESULTS: No IGI was observed from RF radiation alone or combined treatment with MQ. RF radiation alone was not genotoxic. RF radiation combined with chemical exposure showed some statistically significant differences: increased DNA damage at 6.0 W/kg but decreased DNA damage at 0.6 W/kg in cells exposed to GSM-modulated RF radiation and MQ, and increased micronucleus frequency in cells exposed to CW RF radiation at 0.6 W/kg and MMS.
CONCLUSIONS: Exposure to GSM modulated RF radiation at levels up to 6.0 W/kg did not induce or enhance genomic instability in rat primary astrocytes. Lack of genotoxicity from RF radiation alone was convincingly shown in multiple experiments. Co-genotoxicity of RF radiation and genotoxic chemicals was not consistently supported by the results.
After-effect induced by microwave radiation in human electroencephalographic signal: a feasibility study
Muñoz S, Sebastián JL, Antoranz P, García-Cambero JP, Sanchis-Otero A.Toxicity assessment of biological suspensions using the dielectric impedance spectroscopy technique. Int J Radiat Biol. 2018 Oct;94(10):944-950. doi: 10.1080/09553002.2018.1439196. Epub 2018 Feb 21.
PURPOSE: This article studies the variation of the electromagnetic parameters of a suspension of zebrafish (Danio rerio) embryos to assess its potential applications to toxicological and biomedical research areas.
MATERIALS AND METHODS: For this purpose, the dielectric impedance spectroscopy technique is applied to a modified coaxial line enclosing the biological suspension to be characterized in the frequency range from 100 kHz to 100 MHz. The electrical parameters of the suspension under test were obtained by fitting the impedance spectra to the resulted from the simulation of the test fixture using finite elements (FE).
RESULTS: Variation of the complex permittivity of the suspensions makes possible to identify viable and non-viable embryos after a toxic exposure, as well as different stages during the blastula period of embryonic development of the zebrafish.
CONCLUSIONS: The approach presented here, combining experimental and simulation techniques, may provide a basis for a non-invasive method to assess toxicity in any biological suspension.