A generalized model for the interaction of microwave radiation with bound water in biological material.

The Journal of microwave power · 1981 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 6021

Study snapshot

PublicationThe Journal of microwave power · 1981

Study typeother

Reported directionUnclear

Evidence ratingInsufficient

Abstract

Calculations have been performed concerning the deposition of microwave energy in bound water surrounding a biological macromolecule immersed in a continuum consisting of free water and dissolved ions. In particular a previous model of a hydrated macromolecule has been generalised to one where the relaxation frequency of the bound water varies across the layer, and the calculations have been carried out for three combinations of values of ionic conductivity of the bound water and the continuum. When these conductivities are equal, but low, the average energy deposition per unit volume in the bound water is greater, sometimes by at least an order of magnitude, than that in the continuum at frequencies in the region of hundreds of MHz to a few GHz. As the ionic conductivity increases this effect decreases and at conductivities equal to that of physiological saline the specific energy deposition in the bound water is not more than around twice that in the surrounding electrolyte continuum over this frequency range. Therefore, for tissues of high bound water content exposed to microwaves of a given power density the biological effect produced is enhanced. For a biological tissue of high ionic conductivity with 20% of its water in the bound state the overall energy absorption would be 25% greater at certain frequencies than if all the water were in the free state. For materials of low ionic conductivity the increase would be more than one order of magnitude.

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AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typeother

Effect directionunclear

PopulationNot supplied

Sample sizeNot supplied

ExposureRF

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

Model calculations suggest that, at frequencies in the region of hundreds of MHz to a few GHz, average energy deposition per unit volume in bound water can exceed that in the surrounding electrolyte continuum when ionic conductivities are equal but low (sometimes by at least an order of magnitude). As ionic conductivity increases, the difference decreases; at conductivities equal to physiological saline, bound-water specific energy deposition was reported as not more than around twice that of the continuum over this frequency range. The model implies overall tissue energy absorption could be ~25% greater at certain frequencies for tissue with high ionic conductivity and 20% bound water, and more than an order of magnitude greater for low ionic conductivity materials.

Outcomes measured

calculated microwave energy deposition in bound vs free water (specific/average energy deposition per unit volume)
overall energy absorption differences as a function of ionic conductivity and frequency

Limitations

The abstract describes theoretical/model calculations rather than measurements in biological systems.
No specific exposure metric (e.g., incident power density, SAR) or exact frequencies are provided beyond a broad range.
Biological effects are inferred from energy deposition/absorption rather than directly measured outcomes.

View raw extracted JSON

{
  "study_type": "other",
  "exposure": {
    "band": "RF",
    "source": null,
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "calculated microwave energy deposition in bound vs free water (specific/average energy deposition per unit volume)",
    "overall energy absorption differences as a function of ionic conductivity and frequency"
  ],
  "main_findings": "Model calculations suggest that, at frequencies in the region of hundreds of MHz to a few GHz, average energy deposition per unit volume in bound water can exceed that in the surrounding electrolyte continuum when ionic conductivities are equal but low (sometimes by at least an order of magnitude). As ionic conductivity increases, the difference decreases; at conductivities equal to physiological saline, bound-water specific energy deposition was reported as not more than around twice that of the continuum over this frequency range. The model implies overall tissue energy absorption could be ~25% greater at certain frequencies for tissue with high ionic conductivity and 20% bound water, and more than an order of magnitude greater for low ionic conductivity materials.",
  "effect_direction": "unclear",
  "limitations": [
    "The abstract describes theoretical/model calculations rather than measurements in biological systems.",
    "No specific exposure metric (e.g., incident power density, SAR) or exact frequencies are provided beyond a broad range.",
    "Biological effects are inferred from energy deposition/absorption rather than directly measured outcomes."
  ],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "microwave radiation",
    "RF",
    "bound water",
    "hydrated macromolecule",
    "ionic conductivity",
    "energy deposition",
    "specific energy absorption"
  ],
  "suggested_hubs": []
}

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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: 10.1080/16070658.1981.11689216
PubMed: 6909302

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