Model Variability in Assessment of Human Exposure to Radiofrequency Fields

Abstract

Overview

Recent advances in computational dosimetry for electromagnetics and thermodynamics are reviewed to assess human exposure to electromagnetic fields (EMF) in the MHz-to-terahertz range. The study emphasizes variability in computational dosimetry models, examining computational electromagnetic methods, anatomical phantoms, and tissue dielectric property characterization. The rationale for using dosimetric quantities—such as Specific Absorption Rate (SAR) and absorbed power density—in international guidelines is re-examined regarding their relationship with temperature rises in human tissues.

Findings

• Heating factors, defined as steady-state temperature rise per SAR, are assessed for brain, eye lens, skin, and body core.
• The study discusses the transition in guidelines from using SAR to absorbed power density at 6 GHz, highlighting considerations around optimal spatial averaging.
• Computational evaluations cover product compliance, 5G devices, and wireless power transfer systems.
• SAR variability is driven largely by anatomical scaling, with children exhibiting potentially higher localized absorption than adults—sometimes up to a threefold difference in rare cases.
• Whole-body averaged SAR (WBASAR) is generally 40%-60% higher in children and smaller models compared to adults, with additional variability contributed by body shape, modeling method, and tissue properties (10%-30%).
• Temperature rise variability is more sensitive to thermal and physiological parameters, such as blood perfusion and thermoregulatory responses, rather than just anatomy.
• Vascular models can influence local temperature distribution, especially near large arteries and deep brain regions.
• The observed variability in computed temperature rise and SAR remains within the safety margins set by ICNIRP and IEEE guidelines, but further research is essential as new technologies like 6G emerge.

Conclusion

Model variability in computational dosimetry significantly affects predictions of EMF-induced temperature rise, and ultimately, assessments of health risk. Anatomical, thermophysiological, and numerical model differences play a crucial role in defining physical exposure limits and highlight the need for ongoing research. Although current safety guidelines incorporate margins that cover known variability, attention to these uncertainties remains critical for robust EMF safety and standard refinement.