SAR thresholds for electromagnetic exposure using functional thermal dose limits.

Abstract

BACKGROUND AND PURPOSE: To protect against any potential adverse effects to human health from localised exposure to radio frequency (100 kHz-3 GHz) electromagnetic fields (RF EMF), international health organisations have defined basic restrictions on specific absorption rate (SAR) in tissues. These exposure restrictions incorporate safety factors which are generally conservative so that exposures that exceed the basic restrictions are not necessarily harmful. The magnitude of safety margin for various exposure scenarios is unknown. This shortcoming becomes more critical for medical applications where the safety guidelines are required to be relaxed. The purpose of this study was to quantify the magnitude of the safety factor included in the current basic restrictions for various exposure scenarios under localised exposure to RF EMF. MATERIALS AND METHODS: For each exposure scenario, we used the lowest thermal dose (TD) required to induce acute local tissue damage reported in literature, calculated the corresponding TD-functional SAR limits (SAR) and related these limits to the existing basic restrictions, thereby estimating the respective safety factor. RESULTS: The margin of safety factor in the current basic restrictions on 10 g peak spatial average SAR (psSAR) for muscle is large and can reach up to 31.2. CONCLUSIONS: Our analysis provides clear instructions for calculation of SAR and consequently quantification of the incorporated safety factor in the current basic restrictions. This research can form the basis for further discussion on establishing the guidelines dedicated to a specific exposure scenario, i.e. exposure-specific SAR limits, rather than the current generic guidelines.

AI evidence extraction

Main findings

Using literature-reported lowest thermal dose required to induce acute local tissue damage, the authors estimated TD-functional SAR limits and compared them to existing basic restrictions. They report that the margin of safety factor in current 10 g peak spatial average SAR (psSAR) basic restrictions for muscle is large and can reach up to 31.2.

Outcomes measured

• Safety factor/margin in existing basic restrictions for localized RF EMF exposure
• Thermal dose (TD)-functional SAR limits related to acute local tissue damage

Limitations

• Safety margin estimates are based on lowest thermal dose values reported in literature (details not provided in abstract).
• Applies to specific scenario described (10 g psSAR for muscle); generalizability to other tissues/exposure scenarios not stated in abstract.

Suggested hubs

• who-icnirp (0.78)
  Discusses international basic restrictions on SAR and quantifies incorporated safety factors relevant to guideline-setting.

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    "study_type": "other",
    "exposure": {
        "band": "RF",
        "source": null,
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": null,
    "sample_size": null,
    "outcomes": [
        "Safety factor/margin in existing basic restrictions for localized RF EMF exposure",
        "Thermal dose (TD)-functional SAR limits related to acute local tissue damage"
    ],
    "main_findings": "Using literature-reported lowest thermal dose required to induce acute local tissue damage, the authors estimated TD-functional SAR limits and compared them to existing basic restrictions. They report that the margin of safety factor in current 10 g peak spatial average SAR (psSAR) basic restrictions for muscle is large and can reach up to 31.2.",
    "effect_direction": "unclear",
    "limitations": [
        "Safety margin estimates are based on lowest thermal dose values reported in literature (details not provided in abstract).",
        "Applies to specific scenario described (10 g psSAR for muscle); generalizability to other tissues/exposure scenarios not stated in abstract."
    ],
    "evidence_strength": "insufficient",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "radiofrequency",
        "RF EMF",
        "specific absorption rate",
        "SAR",
        "peak spatial average SAR",
        "psSAR",
        "thermal dose",
        "acute local tissue damage",
        "basic restrictions",
        "safety factor",
        "exposure guidelines"
    ],
    "suggested_hubs": [
        {
            "slug": "who-icnirp",
            "weight": 0.7800000000000000266453525910037569701671600341796875,
            "reason": "Discusses international basic restrictions on SAR and quantifies incorporated safety factors relevant to guideline-setting."
        }
    ]
}

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