Calculation of Electric Field Induced in the Human Body for Simultaneous Exposure to Spatially Uniform ELF Electric and Magnetic Fields With a Phase Difference

International exposure guidelines such as ICNIRP guidelines and IEEE C95.1 standard are published to protect human from potential adverse health effect. These guidelines and standards establish the limit for the induced electric field, also called the basic restriction. The permissible external field strength—known as the reference level—is then conservatively derived from the basic restriction. Though the reference level is calculated assuming that the human body is exposed to electric or magnetic fields separately, in reality, simultaneous exposure to both fields may occur. Such exposures are particularly likely when a human body is positioned under overhead transmission lines. Under such circumstances, a phase difference between the electric and magnetic fields occur due to the phase difference between the power line’s voltage and current. We investigated the impact of external electric and magnetic field phase differences on the induced electric field in numerical human models. This was done under simultaneous exposure to a spatially uniform vertical electric field and horizontal magnetic fields at 50 Hz. Our computational findings revealed that the strength of the induced electric field fluctuates with the phase difference and that the variation caused by this difference varies across different body parts. The basic restrictions of the ICNIRP guidelines were met under the simultaneous exposure to electric and magnetic fields at the reference level, even when considering the phase difference

Intercomparison of in Situ Electric Fields in Human Models Exposed to Spatially Uniform Magnetic Fields

IEEE C95.1 (radio frequency) and C95.6 (low frequency) standards for human protection from electromagnetic fields are currently under revision. In the next revision, they will be combined into one standard covering the frequency range from 0 Hz to 300 GHz. Although the C95.1 standard considers anatomical human models for deriving the relationship between internal and external field strengths, homogeneous ellipses are used in the C95.6 standard. In the guidelines of the International Commission on Non-Ionizing Radiation Protection, anatomical human models are used together with reduction factors to account for numerical uncertainty. It is worth revisiting their relationship when using different anatomical models. In this paper, five research groups performed a comparative study to update the state-of-the-art knowledge of in situ electric fields in anatomical human models when exposed to uniform low-frequency magnetic fields. The main goals were to clarify both numerical uncertainty and model variability. The computational results suggest a high consistency among in situ field strengths across laboratories; agreement in the 99th percentile with a discrepancy of under 5% was achieved. The in situ electric fields varied as expected given the models' different dimensions. The induction factor, which is the ratio of the in situ electric fields for the temporal derivative of the external magnetic flux density, is derived for body parts and tissues. The classification of body parts into 'the limb' and 'other tissues' is shown to be critical for determining the in situ field strength.Peer reviewe

Intercomparison of the averaged induced electric field in learning-based human head models exposed to low-frequency magnetic fields

Publisher Copyright: AuthorAnatomical human models have been widely used in the assessment of induced field strength for low-frequency (LF) electromagnetic field exposure. One bottleneck is the assignment of a single electrical conductivity to all the voxels of the corresponding tissue. This simplification is known to cause computational artifact; therefore, a large reduction factor was considered in international guidelines and standards. Recently, head models with nonuniform conductivities generated using deep learning networks were proposed, and the effect on the reduction of staircasing artifacts was demonstrated. If the effectiveness of the models is confirmed for different models and codes, it would be useful to derive the relationship between the internal and external field strengths needed for setting the exposure limit. The Subcommittee 6 of the IEEE International Committee on Electromagnetic Safety Technical Committee 95 launched a working group to conduct the first intercomparison study of the induced electric field in learning-based head models exposed to LF magnetic fields. Seven international research groups have cooperated in this joint study. The highest relative difference (RD) in averaged electric fields was 23%, which is attributable to the difference caused the by scalar potential finite difference (SPFD) method and finite element method. Except for one group, the RDs in the 100th and 99th percentile values of the averaged electric field using the SPFD method with different solvers and codes were below 1%, indicating that the uncertainty due to different codes is sufficiently small under the same exposure scenarios. The findings would be informative for future revision of exposure limits and reduction factors in the exposure standard, which is closely related to computational uncertainty.Peer reviewe