Exposure of children to ELF magnetic fields in France: Results of the EXPERS study

Abstract

Exposure of children to ELF magnetic fields in France: Results of the EXPERS study Magne I, Souques M, Bureau I, Duburcq A, Remy E, Lambrozo J. Exposure of children to extremely low frequency magnetic fields in France: Results of the EXPERS study. J Expo Sci Environ Epidemiol. 2016 Nov 9. doi: 10.1038/jes.2016.59. Abstract The assessment of magnetic field exposure in children is an important point in the context of epidemiological issues. EXPERS is the first study ever carried out measuring personal exposure to extremely low frequency magnetic fields at a national scale, involving 977 French children with 24 h personal measurements. Descriptive statistical analyses were performed for all the children, and only for children where no alarm clock was identified, as in some cases this requirement of the measurement protocol was not respected. The proportion of children with a 24 h arithmetic mean of ≥0.4 μT was 3.1% when considering all children and 0.8% when excluding alarm clocks. The alarm clocks were the main variable linked to the child exposure measurements. Magnetic field exposure increased when the home was located close to a high voltage power line. However, none of the 0.8% of children living at <125 m to a 225 kV line or <200 m to a 400 kV overhead line had a personal exposure of >0.4 μT. A multiple correspondence analysis showed the difficulty to build a statistical model predicting child exposure. The distribution of child personal exposure was significantly different from the distribution of exposure during sleep, questioning the exposure assessment in some epidemiological studies. ncbi.nlm.nih.gov Conclusion The EXPERS study is the first study of magnetic field personal exposure of children, with a significant number of subjects, at the scale of a country. It is also the first study on this subject in France. We looked for a relationship between the subjects' characteristics and their exposure, and observed differences depending on the indicator chosen (AM, GM or median). We studied the AM in more detail and found a strong correlation between the highest exposures and alarm clocks because of non-respect of the measurement protocol. That is why we performed two analyses, one over all the children, and one over the children for whom no alarm clock was identified on the magnetic field measurements during the night. The proportion of children with an AM ≥0.4 μT was 3.1% when considering all children and 0.8% when excluding those with alarm clocks. The magnetic field exposure was found to be correlated and increased when the home was located close to a 63 to 400 kV overhead line. However, few children were concerned and none of them had a personal exposure of >0.4 μT. On the contrary, the magnetic field exposure was found to be correlated and decreased when the home was located close to a MV overhead line. We hypothesize that this result is an artifact, because these grids are mainly found in rural areas, and the exposure was inversely correlated with the size of urban areas. We looked for correlations between the 24 h exposure (AM, GM and median). Excepted the alarm clocks, no other variable was significantly linked to the child exposure. This result was confirmed by a multiple correspondence analysis that showed that it would be difficult to build a model to predict the child exposure from the collected variables. The distribution of the 24 h AM, which is the personal exposure of children, was found to be significantly different from the distribution of the AM during the sleep of children, or of the TWA that was calculated from AM during sleep and school periods. This result questions the exposure assessment in some epidemiological studies. The same work will be done for the adults of the EXPERS study. More detailed focus will be done for electric grids.

AI evidence extraction

Main findings

In 977 French children with 24 h personal measurements, 3.1% had a 24 h arithmetic mean ≥0.4 µT; this was 0.8% when excluding children for whom an alarm clock was identified in night measurements. Alarm clocks were the main variable linked to higher measured exposure. Exposure increased with proximity to high-voltage overhead lines, but among children living <125 m from a 225 kV line or <200 m from a 400 kV line, none had personal exposure >0.4 µT; exposure distributions differed between 24 h personal exposure and sleep-period exposure, raising questions about some epidemiological exposure assessments.

Outcomes measured

• 24 h personal exposure to extremely low frequency magnetic fields (arithmetic mean, geometric mean, median)
• Proportion of children with 24 h arithmetic mean ≥0.4 µT
• Associations of exposure with presence of alarm clocks and proximity to overhead power lines (63–400 kV; 225 kV; 400 kV; MV overhead lines)
• Comparison of distribution of 24 h exposure vs exposure during sleep and vs TWA based on sleep and school periods

Limitations

• Some measurement protocol non-compliance related to alarm clocks affected exposure estimates, requiring analyses excluding those cases.
• Multiple correspondence analysis indicated difficulty building a predictive statistical model from collected variables.
• Authors hypothesize an observed decrease in exposure near MV overhead lines may be an artifact related to rural/urban differences.

Suggested hubs

• occupational-exposure (0)

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    "study_type": "exposure_assessment",
    "exposure": {
        "band": "ELF",
        "source": "power lines / household sources (alarm clocks)",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": "24 h personal measurements"
    },
    "population": "French children",
    "sample_size": 977,
    "outcomes": [
        "24 h personal exposure to extremely low frequency magnetic fields (arithmetic mean, geometric mean, median)",
        "Proportion of children with 24 h arithmetic mean ≥0.4 µT",
        "Associations of exposure with presence of alarm clocks and proximity to overhead power lines (63–400 kV; 225 kV; 400 kV; MV overhead lines)",
        "Comparison of distribution of 24 h exposure vs exposure during sleep and vs TWA based on sleep and school periods"
    ],
    "main_findings": "In 977 French children with 24 h personal measurements, 3.1% had a 24 h arithmetic mean ≥0.4 µT; this was 0.8% when excluding children for whom an alarm clock was identified in night measurements. Alarm clocks were the main variable linked to higher measured exposure. Exposure increased with proximity to high-voltage overhead lines, but among children living <125 m from a 225 kV line or <200 m from a 400 kV line, none had personal exposure >0.4 µT; exposure distributions differed between 24 h personal exposure and sleep-period exposure, raising questions about some epidemiological exposure assessments.",
    "effect_direction": "unclear",
    "limitations": [
        "Some measurement protocol non-compliance related to alarm clocks affected exposure estimates, requiring analyses excluding those cases.",
        "Multiple correspondence analysis indicated difficulty building a predictive statistical model from collected variables.",
        "Authors hypothesize an observed decrease in exposure near MV overhead lines may be an artifact related to rural/urban differences."
    ],
    "evidence_strength": "moderate",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "EXPERS",
        "children",
        "France",
        "extremely low frequency",
        "ELF",
        "magnetic fields",
        "personal exposure",
        "24 h measurement",
        "alarm clock",
        "high voltage power line",
        "overhead line",
        "0.4 µT",
        "exposure assessment"
    ],
    "suggested_hubs": [
        {
            "slug": "occupational-exposure",
            "weight": 0,
            "reason": null
        }
    ]
}

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