Absorption of microwave radiation by the anesthetized rat: electromagnetic and thermal hotspots in body and tail.

Abstract

Anatomic variability in the deposition of radiofrequency electromagnetic energy in mammals has been well documented. A recent study [D'Andrea et al., 1985] reported specific absorption rate (SAR) hotspots in the brain, rectum and tail of rat carcasses exposed to 360- and to 2,450-MHz microwave radiation. Regions of intense energy absorption are generally thought to be of little consequence when predicting thermal effects of microwave irradiation because it is presumed that heat transfer via the circulatory system promptly redistributes localized heat to equilibrate tissue temperature within the body. Experiments on anesthetized, male Long-Evans rats (200-260 g) irradiated for 10 or 16 min with 2,450, 700, or 360 MHz radiation at SARs of 2 W/kg, 6 W/kg, or 10 W/kg indicated that postirradiation localized temperatures in regions previously shown to exhibit high SARs were appreciably above temperatures at body sites with lower SARs. The postirradiation temperatures in the rectum and tail were significantly higher in rats irradiated at 360 MHz and higher in the tail at 2,450 MHz than temperatures resulting from exposure to 700 MHz. This effect was found for whole-body-averaged SARs as low as 6 W/kg at 360 MHz and 10 W/kg at 2,450 MHz. In contrast, brain temperatures in the anesthetized rats were not different from those measured in the rest of the body following microwave exposure.

AI evidence extraction

Main findings

In anesthetized rats irradiated for 10 or 16 minutes at 360, 700, or 2,450 MHz and whole-body-averaged SARs of 2, 6, or 10 W/kg, localized post-irradiation temperatures at previously identified high-SAR regions were appreciably higher than at lower-SAR body sites. Rectum and tail temperatures were significantly higher after 360 MHz exposure, and tail temperature was higher after 2,450 MHz exposure, compared with 700 MHz; brain temperature did not differ from the rest of the body following exposure.

Outcomes measured

• Localized post-irradiation tissue temperature (rectum, tail, brain, other body sites)
• Thermal hotspots relative to SAR hotspots

Limitations

• Sample size not reported in abstract
• Only anesthetized male rats studied; generalizability to other conditions/species not stated
• Short exposure durations (10–16 min)
• Temperature outcomes reported post-irradiation; measurement details not provided in abstract

{
    "study_type": "animal",
    "exposure": {
        "band": "microwave",
        "source": null,
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": "10 or 16 min"
    },
    "population": "Anesthetized, male Long-Evans rats (200–260 g)",
    "sample_size": null,
    "outcomes": [
        "Localized post-irradiation tissue temperature (rectum, tail, brain, other body sites)",
        "Thermal hotspots relative to SAR hotspots"
    ],
    "main_findings": "In anesthetized rats irradiated for 10 or 16 minutes at 360, 700, or 2,450 MHz and whole-body-averaged SARs of 2, 6, or 10 W/kg, localized post-irradiation temperatures at previously identified high-SAR regions were appreciably higher than at lower-SAR body sites. Rectum and tail temperatures were significantly higher after 360 MHz exposure, and tail temperature was higher after 2,450 MHz exposure, compared with 700 MHz; brain temperature did not differ from the rest of the body following exposure.",
    "effect_direction": "harm",
    "limitations": [
        "Sample size not reported in abstract",
        "Only anesthetized male rats studied; generalizability to other conditions/species not stated",
        "Short exposure durations (10–16 min)",
        "Temperature outcomes reported post-irradiation; measurement details not provided in abstract"
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "microwave radiation",
        "radiofrequency",
        "specific absorption rate",
        "SAR hotspots",
        "thermal hotspots",
        "rat",
        "anesthetized",
        "rectum",
        "tail",
        "brain",
        "360 MHz",
        "700 MHz",
        "2450 MHz"
    ],
    "suggested_hubs": []
}

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