Micronucleus formation in human amnion cells after exposure to 50 Hz MF applied horizontally and vertically.

Abstract

Micronucleus (MN) induction as a genotoxic effect of extremely-low-frequency electromagnetic fields (ELF-EMF, 50 Hz, 1 mT) was studied in human amniotic fluid cells (AFC) after continuous exposure to magnetic fields (MF), oriented horizontally and vertically with respect to the surface of the culture medium, at different time points. To compare the effectiveness of different exposure systems, a Helmholtz-coil system and a so-called Merritt-coil system was used. A statistically significant increase in MN frequency could be detected in exposed cells compared to controls after 72 h continuous exposure to MF applied vertically in the Merritt-coil system, while no effect was found after exposure in the Helmholtz-coil system. Furthermore, a significant increase in MN induction occurred after 24, 48 and 72 h exposure to MF applied horizontally in the Helmholtz-coil system in comparison to controls, whereas horizontally MF generated in the Merritt-coil system induced no genotoxic effects. To exclude suppression of indirect EMF-induced DNA-lesions, we studied MN formation in the presence of N-Acetyl-p-aminophenol (APAP, Paracetamol(R)), which is an inhibitor of DNA-repair mechanisms. We found a dose-dependent increase of MN formation in APAP-treated AFC cells, but no significant further increase in MN frequency after additional MF exposure. Therefore we conclude, that EMF-induced MN formation is not caused by directly or indirectly induced clastogenic mechanisms. The obtained results show that the orientation of MF with respect to the cell culture dish and the physical condition of the exposure system is of major importance for the induction of micronuclei in certain cell types. Therefore, the reason for inconsistent results published in the literature may be caused by the variability of exposure systems, the exposure conditions and the cell types used.

AI evidence extraction

Main findings

Human amniotic fluid cells exposed to 50 Hz, 1 mT magnetic fields showed statistically significant increases in micronucleus frequency under some exposure configurations: after 72 h vertical exposure in the Merritt-coil system, and after 24/48/72 h horizontal exposure in the Helmholtz-coil system. No effect was observed for vertical exposure in the Helmholtz-coil system or horizontal exposure in the Merritt-coil system. With the DNA-repair inhibitor APAP, MN increased dose-dependently, but additional MF exposure did not further increase MN frequency; authors conclude MN formation was not due to directly or indirectly induced clastogenic mechanisms and that field orientation/exposure system conditions are important determinants.

Outcomes measured

• Micronucleus (MN) frequency / micronucleus induction (genotoxicity)

Limitations

• Sample size not reported in abstract
• In vitro study; generalizability to humans not established
• Results depended on exposure system and field orientation, indicating sensitivity to experimental setup
• Mechanistic conclusion (not clastogenic) based on APAP co-treatment as described in abstract; details not provided

Suggested hubs

• occupational-exposure (0.2)
  ELF magnetic-field exposure at 50 Hz is relevant to some occupational settings, though this study is in vitro and not explicitly occupational.

{
    "study_type": "in_vitro",
    "exposure": {
        "band": "ELF",
        "source": "laboratory magnetic field exposure (Helmholtz-coil and Merritt-coil systems)",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": "continuous exposure for 24, 48, and 72 h (time points reported)"
    },
    "population": "Human amniotic fluid cells (amnion cells; AFC) in culture",
    "sample_size": null,
    "outcomes": [
        "Micronucleus (MN) frequency / micronucleus induction (genotoxicity)"
    ],
    "main_findings": "Human amniotic fluid cells exposed to 50 Hz, 1 mT magnetic fields showed statistically significant increases in micronucleus frequency under some exposure configurations: after 72 h vertical exposure in the Merritt-coil system, and after 24/48/72 h horizontal exposure in the Helmholtz-coil system. No effect was observed for vertical exposure in the Helmholtz-coil system or horizontal exposure in the Merritt-coil system. With the DNA-repair inhibitor APAP, MN increased dose-dependently, but additional MF exposure did not further increase MN frequency; authors conclude MN formation was not due to directly or indirectly induced clastogenic mechanisms and that field orientation/exposure system conditions are important determinants.",
    "effect_direction": "mixed",
    "limitations": [
        "Sample size not reported in abstract",
        "In vitro study; generalizability to humans not established",
        "Results depended on exposure system and field orientation, indicating sensitivity to experimental setup",
        "Mechanistic conclusion (not clastogenic) based on APAP co-treatment as described in abstract; details not provided"
    ],
    "evidence_strength": "low",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "ELF-EMF",
        "50 Hz",
        "magnetic field",
        "1 mT",
        "micronucleus",
        "genotoxicity",
        "human amniotic fluid cells",
        "Helmholtz coil",
        "Merritt coil",
        "field orientation",
        "APAP",
        "paracetamol",
        "DNA repair inhibitor"
    ],
    "suggested_hubs": [
        {
            "slug": "occupational-exposure",
            "weight": 0.200000000000000011102230246251565404236316680908203125,
            "reason": "ELF magnetic-field exposure at 50 Hz is relevant to some occupational settings, though this study is in vitro and not explicitly occupational."
        }
    ]
}

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