Systematic Derivation of Safety Limits for Time-Varying 5G Radiofrequency Exposure Based on Analytical Models and Thermal Dose

2018 · Harm · Low evidence

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HarmLow evidencePaper 1996

Study snapshot

Publicationmanual · 2018

Study typeengineering

Reported directionHarm

Evidence ratingLow

Abstract

Systematic Derivation of Safety Limits for Time-Varying 5G Radiofrequency Exposure Based on Analytical Models and Thermal Dose Neufeld E, Kuster N. Systematic Derivation of Safety Limits for Time-Varying 5G Radiofrequency Exposure Based on Analytical Models and Thermal Dose. Health Phys. 2018 Sep 21. doi: 10.1097/HP.0000000000000930. Abstract Extreme broadband wireless devices operating above 10 GHz may transmit data in bursts of a few milliseconds to seconds. Even though the time- and area-averaged power density values remain within the acceptable safety limits for continuous exposure, these bursts may lead to short temperature spikes in the skin of exposed people. In this paper, a novel analytical approach to pulsed heating is developed and applied to assess the peak-to- average temperature ratio as a function of the pulse fraction α (relative to the averaging time [INCREMENT]T; it corresponds to the inverse of the peak-to-average ratio). This has been analyzed for two different perfusion- related thermal time constants (τ1 = 100 s and 500 s) corresponding to plane-wave and localized exposures. To allow for peak temperatures that considerably exceed the 1 K increase, the CEM43 tissue damage model, with an experimental-data-based damage threshold for human skin of 600 min, is used to allow large temperature oscillations that remain below the level at which tissue damage occurs. To stay consistent with the current safety guidelines, safety factors of 10 for occupational exposure and 50 for the general public were applied. The model assumptions and limitations (e.g., employed thermal and tissue damage models, homogeneous skin, consideration of localized exposure by a modified time constant) are discussed in detail. The results demonstrate that the maximum averaging time, based on the assumption of a thermal time constant of 100 s, is 240 s if the maximum local temperature increase for continuous-wave exposure is limited to 1 K and α ≥ 0.1. For a very low peak-to-average ratio of 100 (α ≥ 0.01), it decreases to only 30 s. The results also show that the peak- to-average ratio of 1,000 tolerated by the International Council on Non-Ionizing Radiation Protection guidelines may lead to permanent tissue damage after even short exposures, highlighting the importance of revisiting existing exposure guidelines. ncbi.nlm.nih.gov

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AI evidence extraction

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Study typeengineering

Effect directionharm

PopulationNot supplied

Sample sizeNot supplied

ExposuremmWave · bursts of a few milliseconds to seconds; averaging times discussed up to 240 s

Evidence strengthLowConfidence: 74% · Peer reviewed: yes

Main findings

An analytical model of pulsed heating above 10 GHz was developed to relate peak-to-average temperature ratio to pulse fraction and thermal time constants. Using a CEM43 tissue damage model (600 min threshold for human skin) and safety factors (10 occupational, 50 public), the authors report a maximum averaging time of 240 s (assuming thermal time constant 100 s) when continuous-wave local temperature rise is limited to 1 K and pulse fraction α ≥ 0.1; for peak-to-average ratio 100 (α ≥ 0.01) the averaging time decreases to 30 s. The paper states that a peak-to-average ratio of 1,000 (as tolerated by ICNIRP guidelines) may lead to permanent tissue damage after short exposures, suggesting existing guidelines should be revisited.

Outcomes measured

skin temperature spikes (peak-to-average temperature ratio)
maximum averaging time for compliance
thermal dose / tissue damage risk (CEM43 model; threshold 600 min for human skin)

Limitations

Model-based/analytical approach rather than empirical measurements
Assumptions in thermal and tissue damage models (including CEM43)
Homogeneous skin assumption
Localized exposure represented via a modified thermal time constant
Only two perfusion-related thermal time constants analyzed (τ1 = 100 s and 500 s)

View raw extracted JSON

{
  "study_type": "engineering",
  "exposure": {
    "band": "mmWave",
    "source": "5G/broadband wireless devices",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": "bursts of a few milliseconds to seconds; averaging times discussed up to 240 s"
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "skin temperature spikes (peak-to-average temperature ratio)",
    "maximum averaging time for compliance",
    "thermal dose / tissue damage risk (CEM43 model; threshold 600 min for human skin)"
  ],
  "main_findings": "An analytical model of pulsed heating above 10 GHz was developed to relate peak-to-average temperature ratio to pulse fraction and thermal time constants. Using a CEM43 tissue damage model (600 min threshold for human skin) and safety factors (10 occupational, 50 public), the authors report a maximum averaging time of 240 s (assuming thermal time constant 100 s) when continuous-wave local temperature rise is limited to 1 K and pulse fraction α ≥ 0.1; for peak-to-average ratio 100 (α ≥ 0.01) the averaging time decreases to 30 s. The paper states that a peak-to-average ratio of 1,000 (as tolerated by ICNIRP guidelines) may lead to permanent tissue damage after short exposures, suggesting existing guidelines should be revisited.",
  "effect_direction": "harm",
  "limitations": [
    "Model-based/analytical approach rather than empirical measurements",
    "Assumptions in thermal and tissue damage models (including CEM43)",
    "Homogeneous skin assumption",
    "Localized exposure represented via a modified thermal time constant",
    "Only two perfusion-related thermal time constants analyzed (τ1 = 100 s and 500 s)"
  ],
  "evidence_strength": "low",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "5G",
    "radiofrequency",
    "above 10 GHz",
    "millimeter wave",
    "pulsed exposure",
    "bursts",
    "power density averaging time",
    "skin heating",
    "temperature spikes",
    "thermal time constant",
    "CEM43",
    "tissue damage",
    "ICNIRP",
    "safety limits",
    "occupational exposure",
    "general public"
  ],
  "suggested_hubs": [
    {
      "slug": "5g-policy",
      "weight": 0.86,
      "reason": "Focuses on deriving safety limits for time-varying 5G (>10 GHz) exposures and implications for guidelines."
    },
    {
      "slug": "who-icnirp",
      "weight": 0.83,
      "reason": "Explicitly discusses ICNIRP guideline peak-to-average ratio and suggests revisiting exposure guidelines."
    }
  ]
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1097/hp.0000000000000930
PubMed: Not supplied

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