Acceleration of the development of benzopyrene-induced skin cancer in mice by microwave radiation.

Abstract

Development and growth of skin cancer may be affected by various physical and chemical factors present in human environment. Of these factors electromagnetic radiation of radio- and microwave spectra are among the most common. In the present study Balb/c mice were exposed to chemical carcinogen, 3,4-benzopyrene, painted on the skin every 2nd day for a total of 6 months, and simultaneously irradiated with athermal (5 mW/cm2) or subthermal (15 mW/cm2) doses of 2,450 MHz microwaves. The other group of animals was preirradiated with microwaves at 10 mW/cm2 power level for 1, 2, or 3 months and then treated with benzopyrene, as above. Control mice were exposed for 6 months to benzopyrene, resulting in the development of baso- or spinocellular skin carcinoma within approximately 9 months, and sham-irradiated with microwaves. The growth of the tumour was assessed according to a self-designed 7-range macroscopic scale, supported by microscopical examinations of skin sections. All protocols of microwave irradiations resulted in a significant acceleration of the development of benzopyrene-induced skin cancer and in shortening of life span of the tumour-bearing hosts. This effect seemed to be dose-dependent since subthermal doses (15 mV/cm2) and longer (3 months) expositions to microwaves were more efficient as compared to athermal doses (5 mW/cm2) and shorter preirradiations. In addition, low-level, long-lasting exposure to microwaves led to a marked suppression of delayed hypersensitivity of mice treated with benzopyrene, as assessed by their reactivity to dinitrofluorbenzene (DNFB). It is suggested that the observed co-carcinogenic effect of microwave radiation may, at least in part, result from the inhibitory action of microwaves on cellular immune reactions of exposed animals.

AI evidence extraction

Main findings

All microwave irradiation protocols (2,450 MHz at 5, 10, or 15 mW/cm2; described as athermal or subthermal) significantly accelerated development of benzopyrene-induced skin cancer and shortened lifespan of tumor-bearing mice versus sham-irradiated controls. Effects appeared dose-dependent, with 15 mW/cm2 and longer (3-month) preirradiation more effective than 5 mW/cm2 and shorter preirradiations. Long-lasting low-level microwave exposure was associated with suppressed delayed hypersensitivity (DNFB reactivity) in benzopyrene-treated mice.

Outcomes measured

• Development/latency of benzopyrene-induced skin cancer (baso- or spinocellular carcinoma)
• Tumor growth (macroscopic scale; supported by microscopy)
• Life span of tumor-bearing mice
• Delayed hypersensitivity (DNFB reactivity)

Limitations

• Sample size not reported in abstract
• Exposure metric reported as power density (mW/cm2) without SAR or dosimetry details
• Tumor growth assessed using a self-designed macroscopic scale (validation not described)
• Mechanistic interpretation (immune suppression) is suggested rather than directly established

Suggested hubs

• who-icnirp (0.25)
  Animal study on microwave exposure and cancer outcomes relevant to RF health-risk evaluations.

{
    "study_type": "animal",
    "exposure": {
        "band": "microwave",
        "source": null,
        "frequency_mhz": 2450,
        "sar_wkg": null,
        "duration": "Simultaneous exposure during 6 months of benzopyrene treatment; or preirradiation for 1, 2, or 3 months before benzopyrene treatment"
    },
    "population": "Balb/c mice",
    "sample_size": null,
    "outcomes": [
        "Development/latency of benzopyrene-induced skin cancer (baso- or spinocellular carcinoma)",
        "Tumor growth (macroscopic scale; supported by microscopy)",
        "Life span of tumor-bearing mice",
        "Delayed hypersensitivity (DNFB reactivity)"
    ],
    "main_findings": "All microwave irradiation protocols (2,450 MHz at 5, 10, or 15 mW/cm2; described as athermal or subthermal) significantly accelerated development of benzopyrene-induced skin cancer and shortened lifespan of tumor-bearing mice versus sham-irradiated controls. Effects appeared dose-dependent, with 15 mW/cm2 and longer (3-month) preirradiation more effective than 5 mW/cm2 and shorter preirradiations. Long-lasting low-level microwave exposure was associated with suppressed delayed hypersensitivity (DNFB reactivity) in benzopyrene-treated mice.",
    "effect_direction": "harm",
    "limitations": [
        "Sample size not reported in abstract",
        "Exposure metric reported as power density (mW/cm2) without SAR or dosimetry details",
        "Tumor growth assessed using a self-designed macroscopic scale (validation not described)",
        "Mechanistic interpretation (immune suppression) is suggested rather than directly established"
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "microwave radiation",
        "2450 MHz",
        "power density",
        "athermal",
        "subthermal",
        "benzopyrene",
        "skin cancer",
        "Balb/c mice",
        "co-carcinogenic effect",
        "delayed hypersensitivity",
        "DNFB",
        "immune suppression"
    ],
    "suggested_hubs": [
        {
            "slug": "who-icnirp",
            "weight": 0.25,
            "reason": "Animal study on microwave exposure and cancer outcomes relevant to RF health-risk evaluations."
        }
    ]
}

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