Thermoregulatory responses of the immature rat following repeated postnatal exposures to 2,450-MHz microwaves.

Abstract

This study was designed to determine the changes that occur in the thermoregulatory ability of the immature rat repeatedly exposed to low-level microwave radiation. Beginning at 6-7 days of age, previously untreated rats were exposed to 2,450-MHz continuous-wave microwaves at a power density of 5 mW/cm2 for 10 days (4 h/day). Microwave and sham (control) exposures were conducted at ambient temperatures (Ta) which represent different levels of cold stress for the immature rat (ie, "exposure" Ta = 20 and 30 degrees C). Physiological tests were conducted at 5-6 and 16-17 days of age, in the absence of microwaves, to determine pre- and postexposure responses, respectively. Measurements of metabolic rate, colonic temperature, and tail skin temperature were made at "test" Ta = 25.0, 30.0, 32.5, and 35.0 degrees C. Mean growth rates were lower for rats exposed to Ta = 20 degrees C than for those exposed to Ta = 30 degrees C, but microwave exposure exerted no effect at either exposure Ta. Metabolic rates and body temperatures of all exposure groups were similar to values for untreated animals at test Ta of 32.5 degrees C and 35.0 degrees C. Colonic temperatures of rats repeatedly exposed to sham or microwave conditions at exposure Ta = 20 degrees C or to sham conditions at exposure Ta = 30 degrees C were approximately 1 degrees C below the level for untreated animals at test Ta of 25.0 degrees C and 30.0 degrees C. However, when the exposure Ta was warmer, rats exhibited a higher colonic temperature at these cold test Ta, indicating that the effectiveness of low-level microwave treatment to alter thermoregulatory responses depends on the magnitude of the cold stress.

AI evidence extraction

Main findings

Rats were repeatedly exposed to 2,450-MHz continuous-wave microwaves (5 mW/cm2) or sham conditions at ambient temperatures representing different cold stress levels (20°C or 30°C). Microwave exposure had no effect on mean growth rates at either exposure temperature. Differences in colonic temperature at colder test ambient temperatures suggested that any alteration of thermoregulatory responses depended on the magnitude of cold stress during exposure.

Outcomes measured

• Thermoregulatory ability
• Metabolic rate
• Colonic temperature
• Tail skin temperature
• Growth rate

Limitations

• Sample size not reported in the abstract
• SAR not reported (only power density provided)
• Details of randomization/blinding not described in the abstract

Suggested hubs

• who-icnirp (0.2)
  Animal study of microwave exposure relevant to RF exposure guidelines context, though no policy content is described.

{
    "study_type": "animal",
    "exposure": {
        "band": "microwave",
        "source": null,
        "frequency_mhz": 2450,
        "sar_wkg": null,
        "duration": "10 days (4 h/day) beginning at 6–7 days of age"
    },
    "population": "Immature rats (beginning at 6–7 days of age)",
    "sample_size": null,
    "outcomes": [
        "Thermoregulatory ability",
        "Metabolic rate",
        "Colonic temperature",
        "Tail skin temperature",
        "Growth rate"
    ],
    "main_findings": "Rats were repeatedly exposed to 2,450-MHz continuous-wave microwaves (5 mW/cm2) or sham conditions at ambient temperatures representing different cold stress levels (20°C or 30°C). Microwave exposure had no effect on mean growth rates at either exposure temperature. Differences in colonic temperature at colder test ambient temperatures suggested that any alteration of thermoregulatory responses depended on the magnitude of cold stress during exposure.",
    "effect_direction": "mixed",
    "limitations": [
        "Sample size not reported in the abstract",
        "SAR not reported (only power density provided)",
        "Details of randomization/blinding not described in the abstract"
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "immature rat",
        "thermoregulation",
        "microwave",
        "2450 MHz",
        "continuous-wave",
        "power density",
        "cold stress",
        "metabolic rate",
        "colonic temperature",
        "tail skin temperature",
        "growth rate",
        "sham exposure"
    ],
    "suggested_hubs": [
        {
            "slug": "who-icnirp",
            "weight": 0.200000000000000011102230246251565404236316680908203125,
            "reason": "Animal study of microwave exposure relevant to RF exposure guidelines context, though no policy content is described."
        }
    ]
}

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