The effects of radiofrequency fields on cell proliferation are non-thermal.

Abstract

The number of reports on the effects induced by radiofrequency (RF) electromagnetic fields and microwave (MW) radiation in various cellular systems is still increasing. Until now no satisfactory mechanism has been proposed to explain the biological effects of these fields. One of the current theories is that heat generation by RF/MW is the cause, in spite of the fact that a great number of studies under isothermal conditions have reported significant cellular changes after exposure to RF/MW. Therefore, this study was undertaken to investigate which effect MW radiation from these fields in combination with a significant change of temperature could have on cell proliferation. The experiments were performed on the same cell line, and with the same exposure system as in a previous work [S. Kwee, P. Raskmark, Changes in cell proliferation due to environmental non-ionizing radiation: 2. Microwave radiation, Bioelectrochem. Bioenerg., 44 (1998), pp. 251-255]. The field was generated by signal simulation of the Global System for Mobile communications (GSM) of 960 MHz. Cell cultures, growing in microtiter plates, were exposed in a specially constructed chamber, a Transverse Electromagnetic (TEM) cell. The Specific Absorption Rate (SAR) value for each cell well was calculated for this exposure system. However, in this study the cells were exposed to the field at a higher or lower temperature than the temperature in the field-free incubator i.e., the temperature in the TEM cell was either 39 or 35 +/- 0.1 degrees C. The corresponding sham experiments were performed under exactly the same experimental conditions. The results showed that there was a significant change in cell proliferation in the exposed cells in comparison to the non-exposed (control) cells at both temperatures. On the other hand, no significant change in proliferation rate was found in the sham-exposed cells at both temperatures. This shows that biological effects due to RF/MW cannot be attributed only to a change of temperature. Since the RF/MW induced changes were of the same order of magnitude at both temperatures and also comparable to our previous results under isothermal conditions at 37 degrees C, cellular stress caused by electromagnetic fields could initiate the changes in cell cycle reaction rates. It is widely accepted that certain classes of heat-shock proteins are involved in these stress reactions.

AI evidence extraction

Main findings

Cell cultures exposed to a GSM-simulated 960 MHz field in a TEM cell showed a significant change in cell proliferation compared with non-exposed controls at both 39°C and 35±0.1°C. Sham-exposed cells under the same temperature conditions showed no significant change in proliferation.

Outcomes measured

• Cell proliferation

Limitations

• Sample size not reported in abstract.
• Exposure duration not reported in abstract.
• SAR values were calculated but not reported in abstract.
• Direction of the proliferation change (increase vs decrease) not specified in abstract.
• Single cell line/exposure system; generalizability unclear from abstract.

Suggested hubs

• who-icnirp (0.2)
  In vitro study of RF (GSM 960 MHz) biological effects relevant to RF health-risk evaluations.

{
    "study_type": "in_vitro",
    "exposure": {
        "band": "RF/microwave",
        "source": "GSM signal simulation (mobile communications)",
        "frequency_mhz": 960,
        "sar_wkg": null,
        "duration": null
    },
    "population": "Cell line (cell cultures in microtiter plates)",
    "sample_size": null,
    "outcomes": [
        "Cell proliferation"
    ],
    "main_findings": "Cell cultures exposed to a GSM-simulated 960 MHz field in a TEM cell showed a significant change in cell proliferation compared with non-exposed controls at both 39°C and 35±0.1°C. Sham-exposed cells under the same temperature conditions showed no significant change in proliferation.",
    "effect_direction": "harm",
    "limitations": [
        "Sample size not reported in abstract.",
        "Exposure duration not reported in abstract.",
        "SAR values were calculated but not reported in abstract.",
        "Direction of the proliferation change (increase vs decrease) not specified in abstract.",
        "Single cell line/exposure system; generalizability unclear from abstract."
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "radiofrequency",
        "microwave",
        "GSM",
        "960 MHz",
        "TEM cell",
        "specific absorption rate",
        "cell proliferation",
        "non-thermal effects",
        "temperature",
        "sham exposure"
    ],
    "suggested_hubs": [
        {
            "slug": "who-icnirp",
            "weight": 0.200000000000000011102230246251565404236316680908203125,
            "reason": "In vitro study of RF (GSM 960 MHz) biological effects relevant to RF health-risk evaluations."
        }
    ]
}

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