Thermal and SAR-Based Limits for Human Skin Exposed to Terahertz Radiation

Authors: Elmaadawy S, Jornet JM

Year: 2025

Category: Biophysics, Electromagnetic Safety

Journal: 2025 International Telecommunications Conference (ITC-Egypt)

DOI: 10.1109/ITC-Egypt66095.2025.11186625

URL: https://ieeexplore-ieee-org.libproxy.berkeley.edu/document/11186625

Abstract

Overview

Terahertz technology is rapidly emerging as a key player in wireless communication and sensing, drawing increasing research attention. However, safety regulations have yet to fully encompass the entire terahertz spectrum, with current standards addressing only the sub-terahertz band (100-300GHz).

Methods

To address this gap, the authors developed a COMSOL Multiphysics model to:

  • Analyze the thermal impact of terahertz exposure on human skin
  • Determine maximum permissible power limits from 0.1 THz to 5 THz
  • Assess state-of-the-art terahertz wireless communication systems and evaluate related exposure safety

Findings

  • The currently defined power levels for the sub-terahertz band are insufficient for both the sub-terahertz and broader terahertz regions.
  • COMSOL simulations demonstrated that keeping SAR below the accepted 1.6 W/kg threshold requires power densities under 0.226 W/m2, which yielded negligible increases in skin temperature.
  • Even at power densities as high as 100 W/m2, although the thermal effects were minimal (≈0.03 K), SAR values far exceeded recognized safety standards.
  • Temporal SAR analysis suggests that stricter limits could be necessary for prolonged exposure.

Conclusions

  • This research provides the first comprehensive thermal and SAR-based safety analysis for human skin exposed to terahertz frequencies (0.1-5 THz).
  • Findings indicate that current sub-THz safety standards are not transferrable to the full terahertz spectrum, underscoring the urgent need for updated exposure guidelines.
  • Limitations include the frequency range (only up to 5 THz) and assumptions about uniform skin structure.
  • Future work: experimental phantom studies and expanded analysis of potential long-term biological impacts of terahertz radiation.

⚠️ There is a clear connection between terahertz electromagnetic fields and regulatory safety concerns relating to human health, particularly with respect to skin exposure and the inadequacy of current standards.

terahertz radiation human skin SAR thermal effects safety guidelines wireless communication exposure limits
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