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

Abstract

Category: Biophysics, Electromagnetic Safety Tags: terahertz radiation, human skin, SAR, thermal effects, safety guidelines, wireless communication, exposure limits DOI: 10.1109/itc-egypt66095.2025.11186625 URL: ieeexplore-ieee-org.libproxy.berkeley.edu 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.

AI evidence extraction

Main findings

Using COMSOL Multiphysics simulations for 0.1–5 THz exposure, the authors report that maintaining SAR below 1.6 W/kg corresponds to power densities under 0.226 W/m^2 and produces negligible skin temperature increases. They also report that at 100 W/m^2 thermal effects remain small (~0.03 K) but SAR exceeds recognized safety standards, and that temporal SAR analysis suggests stricter limits may be needed for prolonged exposure.

Outcomes measured

• skin temperature change (thermal impact)
• specific absorption rate (SAR)
• maximum permissible power limits / power density thresholds

Limitations

• Frequency range limited to 0.1–5 THz
• Assumptions about uniform skin structure
• Modeling/simulation study without experimental validation (future phantom studies proposed)

Suggested hubs

• 5g-policy (0.55)
  Focuses on exposure limits/safety guidelines for very high-frequency wireless technologies (0.1–5 THz), relevant to next-generation communications policy discussions.
• who-icnirp (0.6)
  Evaluates adequacy/transferability of existing safety standards and calls for updated exposure guidelines.

{
    "study_type": "engineering",
    "exposure": {
        "band": "terahertz",
        "source": "wireless communication systems / terahertz exposure (modeled)",
        "frequency_mhz": null,
        "sar_wkg": 1.600000000000000088817841970012523233890533447265625,
        "duration": null
    },
    "population": "human skin (modeled)",
    "sample_size": null,
    "outcomes": [
        "skin temperature change (thermal impact)",
        "specific absorption rate (SAR)",
        "maximum permissible power limits / power density thresholds"
    ],
    "main_findings": "Using COMSOL Multiphysics simulations for 0.1–5 THz exposure, the authors report that maintaining SAR below 1.6 W/kg corresponds to power densities under 0.226 W/m^2 and produces negligible skin temperature increases. They also report that at 100 W/m^2 thermal effects remain small (~0.03 K) but SAR exceeds recognized safety standards, and that temporal SAR analysis suggests stricter limits may be needed for prolonged exposure.",
    "effect_direction": "unclear",
    "limitations": [
        "Frequency range limited to 0.1–5 THz",
        "Assumptions about uniform skin structure",
        "Modeling/simulation study without experimental validation (future phantom studies proposed)"
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "unknown",
    "keywords": [
        "terahertz radiation",
        "human skin",
        "SAR",
        "thermal effects",
        "safety guidelines",
        "wireless communication",
        "exposure limits",
        "COMSOL Multiphysics",
        "power density"
    ],
    "suggested_hubs": [
        {
            "slug": "5g-policy",
            "weight": 0.5500000000000000444089209850062616169452667236328125,
            "reason": "Focuses on exposure limits/safety guidelines for very high-frequency wireless technologies (0.1–5 THz), relevant to next-generation communications policy discussions."
        },
        {
            "slug": "who-icnirp",
            "weight": 0.59999999999999997779553950749686919152736663818359375,
            "reason": "Evaluates adequacy/transferability of existing safety standards and calls for updated exposure guidelines."
        }
    ]
}

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