## 1 Introduction  
The increasing use of electric and electronic devices in home and work environments poses the problem of checking for the human safety of possible damages due to electromagnetic fields (EMFs), both at low and high frequencies. EMFs may cause thermal and non-thermal effects on cells, tissues, and living organisms [1]. The interactions of EMFs with the nervous system include effects on neuronal signaling, synaptic plasticity, and potential implications for neurodegenerative conditions [2]. Exposition to EMFs can lead to cardiovascular risk [3], undesired cellular and molecular effects [4], and pacemaker and cardioverter defibrillator malfunctioning [5]. Furthermore, the introduction and diffusion of new technologies, such as wireless energy transmission systems, have accentuated these problems in the case of medical implants [6]. In checking for human safety, some international organizations (IEEE, IEC, ICNIRP) have stated limits (basic restrictions) to the induced current density and electrical field in the human body [7]. However, since these limits are difficult to measure, other limits (reference levels) are stated in free space, assuming uniform fields [8]. To link basic restrictions to reference levels, several coupling factors are defined in the standards from various organizations. Of course, there is vast scientific literature on this topic. An analytical model to establish the induced voltage in a pacemaker, considering a magnetic field in the range from 10 Hz to 30 kHz, is proposed in [9], which also reports some experimental data. In [10], measurements were performed to study safety issues due to exposures to non-uniform fields considering the coupling factor. An experimental assessment of human exposure to electromagnetic fields generated by a domestic induction cooktop was performed in [11]. The main problems related to these approaches are the low accuracy of the analytical methods, their limited application cases, and safety issues related to experimental measurements. Therefore, the use of EMF simulators is considered the best approach [12]. A 3-D human model was combined with a source model to evaluate the coupling factors in [11]. The effectiveness of the quasi-static approximation in assessing human exposure to electromagnetic fields from a wireless power transfer system has been studied in [13]. Numerical investigations to evaluate the coupling factor were reported in [14], considering the frequency range 250 Hz-10 kHz. In this study, the finite difference time domain method was used to evaluate the induced current density in an accurate human body model adopting suitable tissue parameters. The impact of electromagnetic fields on the human body is an important topic in the transportation industry, given the electrification of large vehicles and the push toward the fully a electric transportation paradigm in aircraft, ships, and vehicles [15; 16]. In this context, a study on human safety issues due to EMFs in the passenger compartment of an electric vehicle was reported in [17]. The analysis focused on the internal electric field induced by the non-uniform magnetic fields generated by the cables. In [18], different human body models were considered to evaluate the coupling factors at 50 Hz. Different coil configurations and a quasi-static electromagnetic simulation of a complex anatomical human model were considered to analyze the variation in the coupling factor versus different quantities (distance, radius, etc.). Circular coils and parallel wires with balanced currents were the two different sources of non-uniform magnetic field analyzed in [19], where numerical methods were used to assess the coupling factors under different situations in terms of non-uniform magnetic field exposure. Analyses of high-voltage power lines were led in [20], where the moment method was adopted to analyze the current induced in the body.