Micronucleus induction in Syrian hamster embryo cells following exposure to 50 Hz magnetic fields, benzo(a)pyrene, and TPA in vitro.

Abstract

Electromagnetic fields (EMFs) have been associated with increased incidence of cancer suggested by epidemiological studies. To test the carcinogenic potency of EMF, the in vitro micronucleus assay with SHE cells has been used as a screening method for genotoxicity. A 50Hz magnetic field (MF) of 1mT field strength was applied either alone or with the tumour initiator benzo(a)pyrene (BP) or the tumour promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). All three treatments were applied in single, double or triple treatment regimes. MF or TPA (1nM) alone did not affect the number of micronuclei (MN) in initiated and non-initiated SHE cells. Changing the schedule of the typical initiation protocol, namely applying the initiator (BP) during exposure to MF, results in an 1.8-fold increased MN formation compared to BP treatment alone. Combined experiment with BP, TPA and MF did not cause further MN formation. Since initiation during MF exposure caused a significant increased MN formation, our findings suggest that MFs enhance the initiation process of BP. We think that this MF-enhanced co-carcinogenic effect is caused by an indirect "cell activation" process. The resulting genomic instability is proposed to be due to free radicals and/or to the unscheduled "switching-on" of signal transduction pathways.

AI evidence extraction

Main findings

A 50 Hz magnetic field at 1 mT or TPA (1 nM) alone did not affect micronucleus formation in initiated or non-initiated SHE cells. When benzo(a)pyrene (BP) was applied during magnetic-field exposure (altered initiation schedule), micronucleus formation increased 1.8-fold compared with BP alone; adding TPA to BP+MF did not further increase micronuclei.

Outcomes measured

• Micronucleus (MN) formation / micronuclei number (genotoxicity indicator)

Limitations

• In vitro study in SHE cells; relevance to humans not established in abstract
• Exposure duration and other exposure conditions not reported in abstract
• Sample size and statistical details not reported in abstract
• Findings depend on a specific exposure/treatment schedule (BP applied during MF exposure)

Suggested hubs

• occupational-exposure (0.25)
  Uses a 50 Hz (power-frequency) magnetic field exposure, relevant to ELF contexts often discussed in occupational settings, though no workplace setting is specified.

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    "study_type": "in_vitro",
    "exposure": {
        "band": "ELF",
        "source": null,
        "frequency_mhz": 0.05000000000000000277555756156289135105907917022705078125,
        "sar_wkg": null,
        "duration": null
    },
    "population": "Syrian hamster embryo (SHE) cells (in vitro)",
    "sample_size": null,
    "outcomes": [
        "Micronucleus (MN) formation / micronuclei number (genotoxicity indicator)"
    ],
    "main_findings": "A 50 Hz magnetic field at 1 mT or TPA (1 nM) alone did not affect micronucleus formation in initiated or non-initiated SHE cells. When benzo(a)pyrene (BP) was applied during magnetic-field exposure (altered initiation schedule), micronucleus formation increased 1.8-fold compared with BP alone; adding TPA to BP+MF did not further increase micronuclei.",
    "effect_direction": "mixed",
    "limitations": [
        "In vitro study in SHE cells; relevance to humans not established in abstract",
        "Exposure duration and other exposure conditions not reported in abstract",
        "Sample size and statistical details not reported in abstract",
        "Findings depend on a specific exposure/treatment schedule (BP applied during MF exposure)"
    ],
    "evidence_strength": "low",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "50 Hz",
        "magnetic field",
        "1 mT",
        "ELF-EMF",
        "micronucleus assay",
        "genotoxicity",
        "Syrian hamster embryo cells",
        "benzo(a)pyrene",
        "TPA",
        "co-carcinogenic",
        "initiation",
        "promotion"
    ],
    "suggested_hubs": [
        {
            "slug": "occupational-exposure",
            "weight": 0.25,
            "reason": "Uses a 50 Hz (power-frequency) magnetic field exposure, relevant to ELF contexts often discussed in occupational settings, though no workplace setting is specified."
        }
    ]
}

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