Effects of ambient temperature and exposure to 2450-MHz microwave radiation on evaporative heat loss in the mouse.

Abstract

Whole-body evaporative heat loss was measured as whole-body evaporative water loss in mice during a 90-min exposure to 2450-MHz microwave radiation at an ambient temperature of 20 degrees C and in non-exposed mice maintained at ambient temperatures of 20, 25, 30, 33, and 35 degrees C. The ambient-temperature threshold for increasing evaporative water loss was between 30 and 33 degrees C. A specific absorption rate of microwave radiation in excess of 29 W/kg was required to produce an increase in heat loss. For absorption rates ranging from 29 to 44 W/kg, the mouse dissipated 65% of the total absorbed heat by water evaporation; the remainder was dissipated passively. The data collected in the mouse may be extrapolated to larger species, such as man, but only by an exponential relationship. Using this relationship, it was shown that a threshold specific absorption rate of 29 W/kg in a 0.033-kg mouse was equivalent to approximately 0.25 W/kg in a 70-kg human.

AI evidence extraction

Main findings

In mice, the ambient-temperature threshold for increasing evaporative water loss was between 30 and 33°C. During 90-min 2450-MHz exposure, an SAR in excess of 29 W/kg was required to increase heat loss; for SAR 29–44 W/kg, about 65% of absorbed heat was dissipated by evaporation and the remainder passively. An exponential scaling relationship was used to suggest that 29 W/kg in a 0.033-kg mouse corresponds to approximately 0.25 W/kg in a 70-kg human.

Outcomes measured

• Whole-body evaporative heat loss (whole-body evaporative water loss)
• Ambient-temperature threshold for increasing evaporative water loss
• Specific absorption rate (SAR) threshold for increased heat loss
• Proportion of absorbed heat dissipated via evaporation vs passive dissipation

Limitations

• Sample size not reported in the abstract
• Animal study; human relevance is discussed via extrapolation rather than direct measurement
• Exposure conditions beyond frequency, duration, and SAR range are not described in the abstract

{
    "study_type": "animal",
    "exposure": {
        "band": "microwave",
        "source": null,
        "frequency_mhz": 2450,
        "sar_wkg": 29,
        "duration": "90-min exposure"
    },
    "population": "Mice",
    "sample_size": null,
    "outcomes": [
        "Whole-body evaporative heat loss (whole-body evaporative water loss)",
        "Ambient-temperature threshold for increasing evaporative water loss",
        "Specific absorption rate (SAR) threshold for increased heat loss",
        "Proportion of absorbed heat dissipated via evaporation vs passive dissipation"
    ],
    "main_findings": "In mice, the ambient-temperature threshold for increasing evaporative water loss was between 30 and 33°C. During 90-min 2450-MHz exposure, an SAR in excess of 29 W/kg was required to increase heat loss; for SAR 29–44 W/kg, about 65% of absorbed heat was dissipated by evaporation and the remainder passively. An exponential scaling relationship was used to suggest that 29 W/kg in a 0.033-kg mouse corresponds to approximately 0.25 W/kg in a 70-kg human.",
    "effect_direction": "harm",
    "limitations": [
        "Sample size not reported in the abstract",
        "Animal study; human relevance is discussed via extrapolation rather than direct measurement",
        "Exposure conditions beyond frequency, duration, and SAR range are not described in the abstract"
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "mouse",
        "microwave radiation",
        "2450 MHz",
        "specific absorption rate",
        "SAR threshold",
        "evaporative heat loss",
        "thermoregulation",
        "ambient temperature"
    ],
    "suggested_hubs": []
}

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