Permeability of the blood-brain barrier induced by 915 MHz electromagnetic radiation, continuous wave and modulated at 8, 16, 50, and 200 Hz

Microsc Res Tech · 1994 · Harm · Low evidence

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HarmLow evidencePaper 5455

Albumin leakage was observed in 5/62 controls and 56/184 rats exposed to 915 MHz microwaves. Continuous wave exposure produced 14/35 positive findings, reported as significantly different from controls (P = 0.002).

Study snapshot

PublicationMicrosc Res Tech · 1994

Study typeanimal

Reported directionHarm

Evidence ratingLow

Abstract

Biological effects of electromagnetic fields (EMF) on the blood-brain barrier (BBB) can be studied in sensitive and specific models. In a previous investigation of the permeability of the blood-brain barrier after exposure to the various EMF-components of proton magnetic resonance imaging (MRI), we found that the exposure to MRI induced leakage of Evans Blue labeled proteins normally not passing the BBB of rats [Salford et al. (1992), in: Resonance Phenomena in Biology, Oxford University Press, pp. 87-91]. In the present investigation we exposed male and female Fischer 344 rats in a transverse electromagnetic transmission line chamber to microwaves of 915 MHz as continuous wave (CW) and pulse-modulated with repetition rates of 8, 16, 50, and 200 s-1. The specific energy absorption rate (SAR) varied between 0.016 and 5 W/kg. The rats were not anesthetized during the 2-hour exposure. All animals were sacrificed by perfusion-fixation of the brains under chloral hydrate anesthesia about 1 hour after the exposure. The brains were perfused with saline for 3-4 minutes, and thereafter fixed in 4% formaldehyde for 5-6 minutes. Central coronal sections of the brains were dehydrated and embedded in paraffin and sectioned at 5 microns. Albumin and fibrinogen were demonstrated immunohistochemically. The results show albumin leakage in 5 of 62 of the controls and in 56 of 184 of the animals exposed to 915 MHz microwaves. Continuous wave resulted in 14 positive findings of 35, which differ significantly from the controls (P = 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

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AI evidence extraction

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Study typeanimal

Effect directionharm

PopulationMale and female Fischer 344 rats

Sample size246

ExposureRF · 915 MHz · 2-hour exposure

Evidence strengthLowConfidence: 74% · Peer reviewed: yes

Main findings

Outcomes measured

Blood-brain barrier permeability/leakage (albumin, fibrinogen)
Albumin leakage (immunohistochemistry)

Limitations

Abstract is truncated; results for pulse-modulated conditions (8, 16, 50, 200 Hz) are not fully reported here.
SAR is reported as varying between 0.016 and 5 W/kg, but condition-specific SAR values are not provided in the abstract.
Timing of outcome assessment is limited to about 1 hour post-exposure.

View raw extracted JSON

{
  "study_type": "animal",
  "exposure": {
    "band": "RF",
    "source": null,
    "frequency_mhz": 915,
    "sar_wkg": null,
    "duration": "2-hour exposure"
  },
  "population": "Male and female Fischer 344 rats",
  "sample_size": 246,
  "outcomes": [
    "Blood-brain barrier permeability/leakage (albumin, fibrinogen)",
    "Albumin leakage (immunohistochemistry)"
  ],
  "main_findings": "Albumin leakage was observed in 5/62 controls and 56/184 rats exposed to 915 MHz microwaves. Continuous wave exposure produced 14/35 positive findings, reported as significantly different from controls (P = 0.002).",
  "effect_direction": "harm",
  "limitations": [
    "Abstract is truncated; results for pulse-modulated conditions (8, 16, 50, 200 Hz) are not fully reported here.",
    "SAR is reported as varying between 0.016 and 5 W/kg, but condition-specific SAR values are not provided in the abstract.",
    "Timing of outcome assessment is limited to about 1 hour post-exposure."
  ],
  "evidence_strength": "low",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "blood-brain barrier",
    "BBB permeability",
    "915 MHz",
    "microwaves",
    "RF exposure",
    "continuous wave",
    "pulse-modulated",
    "albumin leakage",
    "fibrinogen",
    "rats",
    "SAR"
  ],
  "suggested_hubs": [
    {
      "slug": "rf-brain-barrier",
      "weight": 0.9,
      "reason": "Animal study assessing BBB permeability after 915 MHz RF exposure."
    }
  ]
}

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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: 10.1002/jemt.1070270608
PubMed: 8012056

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