Wireless Radiation and Electromagnetic Field Studies Published from 2016 to 2020 (Volume 1)

2016 · Mixed · Low evidence

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MixedLow evidencePaper 1304

Study snapshot

Publicationmanual · 2016

Study typeengineering

Reported directionMixed

Evidence ratingLow

Abstract

Wireless Radiation and Electromagnetic Field Studies Published from 2016 to 2020 (Volume 1) Joel M. Moskowitz, Ph.D. School of Public Health University of California, Berkeley Electromagnetic Radiation Safety Links hereby incorporated by reference. 875 pages. The effect of metal objects on the SAR and temperature increase in the human head exposed to dipole antenna (numerical analysis) Bhargava D, Rattanadecho P, Wessapan T. The effect of metal objects on the SAR and temperature increase in the human head exposed to dipole antenna (numerical analysis). Case Studies in Thermal Engineering. Volume 22, December 2020. doi: 10.1016/j.csite.2020.100789. Abstract Wearable metal objects with high electromagnetic reflection characteristics can cause interference with the incident waves during exposure to the electromagnetic (EM) radiation. Therefore, it is of interest to investigate the effect of metal objects capable of increasing the absorption of EM energy and temperature within the tissues when get exposed to EM radiation. A numerical analysis of increase in specific absorption rate (SAR) and temperature distribution in a human head model when metal objects are placed between the head and radiating source is performed. A realistic three-dimensional heterogeneous human head model, metal objects of different shapes and sizes, and spectacles with different lenses are used. A half-wavelength dipole antenna operating at 1800 MHz served as an EM radiation source. Results show that the presence of metal objects in proximity to the head alters SAR and temperature increase within the tissues. In most cases, metal objects redistribute the EM field incident upon them to a smaller region increasing power absorption, thereby increasing SAR and temperature in that region. The power absorption in head layers is found to be sensitive to metal object's size and shape, and distance of the antenna from the objects. Conclusion This study investigated the SAR and temperature increase inside a heterogeneous human head model when metal objects of various shape and sizes were present in the proximity. The results show different important features to be discussed in the paper. The metal objects definitely alter the absorption of EM radiation in the tissues. In most of the cases, presence of all shapes of metal objects increase the SAR and temperature in the head model for voice calling position. Among all the metal objects, pin metal (7.2 cm length) causes highest increase in energy absorption in the head layers. However, pin metal having a length of 8.2 cm also decreases the energy absorption in the head model compared to when there is no metal object at all. For video calling position, both types of spectacle lenses (glass and PVC) decrease the power absorption in the eyeball layers. There is no major difference in the power absorption for both types of lenses. The skin around the eyes, however, has increased value of SAR and temperature in presence of spectacle lenses. The distance between the dipole antenna and metal objects also affects the energy absorbed in the tissue layers. The power absorption in the tissue layers increases as the dipole antenna moves closer to the metal objects. However, for resonant sizes of pin and ring, the head layers had highest power absorption when dipole antenna is 2 cm away from the metal objects. Skin around the eye area also has higher power absorption when dipole antenna is 2 cm away from the spectacle lenses. It is observed that a specific distance between the antenna and metal objects is necessary to have strong current coupling. Moving the antenna far or closer to that specific position makes the coupling go out of phase which results in low energy absorption in the tissue layers. The size of metal objects affects the distribution of power absorbed in the tissues of the head. In presence of metal objects, the energy gets concentrated to a smaller region on the head which increases the power absorption there, hence, increase in SAR and temperature. The SAR and temperature do not directly correlate with each other and highly depend on the dielectric and thermal properties of tissues. For voice calling position, the maximum value of SAR is found in the skin layer, whereas, bone had the maximum value of temperature increase. For video calling position, SAR is maximum in the vitreous layer of the eyeball, whereas, sclera and vitreous had the maximum value of temperature increase. The maximum SAR and temperature obtained in the voice calling position due to pin metal were 26.42 W/kg and 37.42 ̊C, respectively, in the skin layer. Here, the SAR exceed the ICNIRP/IEEE (2 W/kg) limit of general public exposure. For video calling position, the maximum SAR and temperature increase were 196.87 W/kg (glass lens in vitreous) and 43.66 ̊C (no spectacle in sclera and vitreous), respectively. Here, both SAR and temperature obtained were higher than the thresholds for the induction of cataract and opacification formation. This paper, hence, shows how important it is to study temperature distribution along with the SAR distri-bution to clearly understand the effect of EM radiation on the tissues. Results obtained from this study can help spread awareness among the people who often get exposed to EM radiation wearing some type of metal objects. If the metal objects have size and distance in the range of generating strong coupling interaction with the EM radiation source, this could cause a harmful effect on the health. Open access paper: sciencedirect.com

Machine Enhanced Logic

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 typeengineering

Effect directionmixed

PopulationNot supplied

Sample sizeNot supplied

ExposureRF · 1800 MHz

Evidence strengthLowConfidence: 74% · Peer reviewed: yes

Main findings

Numerical modeling using a 3D heterogeneous human head exposed to a 1800 MHz half-wavelength dipole antenna found that nearby metal objects (various shapes/sizes) generally redistributed the incident EM field to smaller regions, increasing localized power absorption, SAR, and temperature; effects depended on object size/shape and antenna distance. In voice-calling position, most metal objects increased SAR/temperature, with a 7.2 cm pin producing the highest increase (reported maximum SAR 26.42 W/kg and temperature 37.42 °C in skin), while an 8.2 cm pin decreased absorption compared with no metal. In video-calling position, spectacle lenses decreased power absorption in eyeball layers but increased SAR/temperature in skin around the eyes; reported maxima included SAR 196.87 W/kg (glass lens in vitreous) and temperature 43.66 °C (no spectacle in sclera/vitreous), and the text states these exceeded ICNIRP/IEEE SAR limits and cataract/opacification-related thresholds.

Outcomes measured

Specific absorption rate (SAR) distribution in head tissues
Temperature distribution/increase in head tissues
Power absorption in head/eye tissue layers
Effect of metal objects (pins, rings, spectacles/lenses) on SAR and temperature
Comparison to ICNIRP/IEEE SAR limit and cataract/opacification thresholds (as stated)

Limitations

Numerical analysis/modeling study (no human or animal measurements reported)
Results depend on modeled head anatomy, tissue dielectric/thermal properties, object geometries, and antenna positioning as specified

View raw extracted JSON

{
  "study_type": "engineering",
  "exposure": {
    "band": "RF",
    "source": "dipole antenna (voice/video calling position)",
    "frequency_mhz": 1800,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "Specific absorption rate (SAR) distribution in head tissues",
    "Temperature distribution/increase in head tissues",
    "Power absorption in head/eye tissue layers",
    "Effect of metal objects (pins, rings, spectacles/lenses) on SAR and temperature",
    "Comparison to ICNIRP/IEEE SAR limit and cataract/opacification thresholds (as stated)"
  ],
  "main_findings": "Numerical modeling using a 3D heterogeneous human head exposed to a 1800 MHz half-wavelength dipole antenna found that nearby metal objects (various shapes/sizes) generally redistributed the incident EM field to smaller regions, increasing localized power absorption, SAR, and temperature; effects depended on object size/shape and antenna distance. In voice-calling position, most metal objects increased SAR/temperature, with a 7.2 cm pin producing the highest increase (reported maximum SAR 26.42 W/kg and temperature 37.42 °C in skin), while an 8.2 cm pin decreased absorption compared with no metal. In video-calling position, spectacle lenses decreased power absorption in eyeball layers but increased SAR/temperature in skin around the eyes; reported maxima included SAR 196.87 W/kg (glass lens in vitreous) and temperature 43.66 °C (no spectacle in sclera/vitreous), and the text states these exceeded ICNIRP/IEEE SAR limits and cataract/opacification-related thresholds.",
  "effect_direction": "mixed",
  "limitations": [
    "Numerical analysis/modeling study (no human or animal measurements reported)",
    "Results depend on modeled head anatomy, tissue dielectric/thermal properties, object geometries, and antenna positioning as specified"
  ],
  "evidence_strength": "low",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "1800 MHz",
    "dipole antenna",
    "SAR",
    "temperature increase",
    "human head model",
    "metal objects",
    "spectacles",
    "lenses",
    "voice calling position",
    "video calling position",
    "ICNIRP",
    "IEEE"
  ],
  "suggested_hubs": [
    {
      "slug": "who-icnirp",
      "weight": 0.55,
      "reason": "Abstract explicitly references ICNIRP/IEEE SAR limit comparisons."
    }
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}

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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: 10.1016/j.csite.2020.100789
PubMed: Not supplied

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