Effects on energy absorption of orientation and size of animals exposed to 2.45-GHz microwave radiation.

Abstract

Rat cadavers oriented perpendicularly to the electric field (parallel to the magnetic field) were exposed to 2.45-GHz microwave radiation. The weight of the cadavers ranged from approximately 5 to 320 g and their lengths ranged from approximately 5 to 22 cm. Average, whole-body specific absorption rates (SAR) were measured using calorimetric techniques, and local specific absorption rates were obtained from time-temperature profiles measured with a non-interacting thermistor probe. The average, whole-body SAR decreased gradually from 0.58 mW g-1 per mW cm-2 at 40 g (10.1 cm in length) to 0.38 mW g-1 per mW cm-2 at 320 g (22 cm in length). The average whole-body SAR decreased from 0.81 to 0.34 mW g-1 per mW cm-2 for cadavers ranging in weight from 5 g (5 cm in length) to 30 g, respectively. The local SAR in the brains decreased from approximately 0.95 mW g-1 per mW cm-2 at 40 g to 0.54 mW g-1 per mW cm-2 at 320 g. Between 5 g and 30 g the SARs in the brain varied from 0.52 to 1.11 mW g-1 per mW cm-2. The local SAR in the colon ranged from 1.05 mW g-1 per mW cm-2 to 0.24 mW g-1 per mW cm-2 for weights between 40 and 320 g. In the 5 to 30 g range, the SAR varied from 0.48 to 1.23 mW g-1 per mW cm-2. A comparison of these results with data previously reported for animals oriented parallel to the E-field showed that the average whole-body SARs were larger for animals weighing greater than 40 g when oriented perpendicularly to the E-field. The local SARs in the colon and brain were slightly higher for the parallel orientation in animals weighing greater than 40 g. The average, whole-body and local SARs were significantly higher for the parallel orientation for animals weighing less than 40 g.

AI evidence extraction

Main findings

Rat cadavers (approximately 5–320 g; 5–22 cm) oriented perpendicular to the electric field were exposed to 2.45-GHz microwave radiation and SAR was measured calorimetrically (whole-body) and via time-temperature profiles (local). Whole-body SAR generally decreased with increasing weight/size (e.g., from 0.58 to 0.38 mW g-1 per mW cm-2 between 40 g and 320 g; and from 0.81 to 0.34 between 5 g and 30 g). Compared with previously reported data for parallel-to-E-field orientation, whole-body SARs were larger for animals >40 g when oriented perpendicular to the E-field, while local SARs in colon and brain were slightly higher for the parallel orientation in animals >40 g; for animals <40 g, whole-body and local SARs were significantly higher for the parallel orientation.

Outcomes measured

• Average whole-body specific absorption rate (SAR)
• Local SAR in brain
• Local SAR in colon
• Effect of animal orientation relative to E-field on SAR
• Effect of animal size/weight on SAR

Limitations

• Cadaver (non-living) model; findings pertain to energy absorption rather than health outcomes
• Sample size not reported in the abstract
• Exposure duration and incident power density levels are not fully specified beyond normalization per mW cm-2
• Comparisons to parallel orientation rely on previously reported data not detailed in the abstract

Suggested hubs

• occupational-exposure (0.2)
  Microwave exposure/SAR dosimetry may be relevant to exposure assessment contexts, though no occupational setting is specified.

{
    "study_type": "exposure_assessment",
    "exposure": {
        "band": "microwave",
        "source": null,
        "frequency_mhz": 2450,
        "sar_wkg": null,
        "duration": null
    },
    "population": "Rat cadavers",
    "sample_size": null,
    "outcomes": [
        "Average whole-body specific absorption rate (SAR)",
        "Local SAR in brain",
        "Local SAR in colon",
        "Effect of animal orientation relative to E-field on SAR",
        "Effect of animal size/weight on SAR"
    ],
    "main_findings": "Rat cadavers (approximately 5–320 g; 5–22 cm) oriented perpendicular to the electric field were exposed to 2.45-GHz microwave radiation and SAR was measured calorimetrically (whole-body) and via time-temperature profiles (local). Whole-body SAR generally decreased with increasing weight/size (e.g., from 0.58 to 0.38 mW g-1 per mW cm-2 between 40 g and 320 g; and from 0.81 to 0.34 between 5 g and 30 g). Compared with previously reported data for parallel-to-E-field orientation, whole-body SARs were larger for animals >40 g when oriented perpendicular to the E-field, while local SARs in colon and brain were slightly higher for the parallel orientation in animals >40 g; for animals <40 g, whole-body and local SARs were significantly higher for the parallel orientation.",
    "effect_direction": "unclear",
    "limitations": [
        "Cadaver (non-living) model; findings pertain to energy absorption rather than health outcomes",
        "Sample size not reported in the abstract",
        "Exposure duration and incident power density levels are not fully specified beyond normalization per mW cm-2",
        "Comparisons to parallel orientation rely on previously reported data not detailed in the abstract"
    ],
    "evidence_strength": "insufficient",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "2.45 GHz",
        "microwave radiation",
        "specific absorption rate",
        "SAR",
        "calorimetry",
        "thermistor probe",
        "rat cadavers",
        "orientation",
        "electric field",
        "magnetic field",
        "brain",
        "colon",
        "dosimetry"
    ],
    "suggested_hubs": [
        {
            "slug": "occupational-exposure",
            "weight": 0.200000000000000011102230246251565404236316680908203125,
            "reason": "Microwave exposure/SAR dosimetry may be relevant to exposure assessment contexts, though no occupational setting is specified."
        }
    ]
}

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