Electromagnetic fields in biology and medicine (Journal editorial, Oct 18, 2018)

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 ….

Threshold of low-level EMF effects

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.