[Analysis of methods for measurement and assessment of occupational exposure to electromagnetic fields in dielectric heating].

Abstract

BACKGROUND: High-frequency (HF) welders are the most common devices that make use of dielectric heating. They are a source of high-intensity electromagnetic fields (EMFs). Manual operation of those welders makes that the limbs are exposed to EMFs of extremely high intensity, far in excess of the currently admissible values. The aim of this study was to update knowledge of actual exposure of HF welder operators to EMF and to optimize the procedure of exposure assessment. MATERIAL AND METHODS: Measurements of the EMF intensity in the vicinity of 10 dielectric welders at work posts of 12 operators were performed. EMF measurements were made using the reference method, extended by auxiliary measurement points to measure induced currents I(L) in the limbs. Induced current measurements were performed in 20 operators tending the same HF welder. RESULTS: the highest values of the electric (E) and magnetic (H) fields measured at work posts were for whole body: E, up to 350 V/m, and H, up to 1.00 A/m; and for limbs: E, up to 600 V/m and H, up to 3.30 A/m. The W exposure indicator in the primary vertical measurement points was almost as high as 60. I(L) values measured at the wrist exceeded 64 mA and were individual-operator-dependent. CONCLUSIONS: EMF exposure of 25% of HF welder operators exceeded the national admissible values and after taking into account the operators' hands, this figure rose to 50%. The measured value of I(L), representing a measure of internal exposure to EMF, should serve as the main criterion in deciding whether working conditions are admissible.

AI evidence extraction

Main findings

Measurements near 10 dielectric welders at work posts found whole-body field maxima up to E=350 V/m and H=1.00 A/m, and limb maxima up to E=600 V/m and H=3.30 A/m; the exposure indicator W in primary vertical points was almost 60. Induced current I(L) at the wrist exceeded 64 mA and varied by operator. The authors report that 25% of operators exceeded national admissible values, rising to 50% when accounting for hands/limbs, and propose I(L) as the main criterion for admissibility decisions.

Outcomes measured

• Electric field strength (V/m)
• Magnetic field strength (A/m)
• Exposure indicator W
• Induced limb current I(L) (mA)
• Exceedance of national admissible exposure values

Limitations

• Frequency of the HF welders not reported in the abstract
• National admissible limits and how exceedance was determined are not detailed in the abstract
• Sample sizes differ by measurement type (12 operators for field measurements; 20 for induced current measurements)
• Results reported as maxima; distribution/averages and uncertainty not provided in the abstract

Suggested hubs

• occupational-exposure (0.95)
  Study measures and assesses EMF exposure among HF welder operators in the workplace, including exceedance of admissible limits.

{
    "study_type": "exposure_assessment",
    "exposure": {
        "band": "RF",
        "source": "occupational",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": "HF (high-frequency) welder operators (dielectric heating)",
    "sample_size": 20,
    "outcomes": [
        "Electric field strength (V/m)",
        "Magnetic field strength (A/m)",
        "Exposure indicator W",
        "Induced limb current I(L) (mA)",
        "Exceedance of national admissible exposure values"
    ],
    "main_findings": "Measurements near 10 dielectric welders at work posts found whole-body field maxima up to E=350 V/m and H=1.00 A/m, and limb maxima up to E=600 V/m and H=3.30 A/m; the exposure indicator W in primary vertical points was almost 60. Induced current I(L) at the wrist exceeded 64 mA and varied by operator. The authors report that 25% of operators exceeded national admissible values, rising to 50% when accounting for hands/limbs, and propose I(L) as the main criterion for admissibility decisions.",
    "effect_direction": "harm",
    "limitations": [
        "Frequency of the HF welders not reported in the abstract",
        "National admissible limits and how exceedance was determined are not detailed in the abstract",
        "Sample sizes differ by measurement type (12 operators for field measurements; 20 for induced current measurements)",
        "Results reported as maxima; distribution/averages and uncertainty not provided in the abstract"
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "dielectric heating",
        "HF welders",
        "occupational exposure",
        "electromagnetic fields",
        "electric field",
        "magnetic field",
        "induced current",
        "exposure assessment",
        "workplace measurements"
    ],
    "suggested_hubs": [
        {
            "slug": "occupational-exposure",
            "weight": 0.9499999999999999555910790149937383830547332763671875,
            "reason": "Study measures and assesses EMF exposure among HF welder operators in the workplace, including exceedance of admissible limits."
        }
    ]
}

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