Strain-Dependent Effects of Long-Term Exposure to 27.5 GHz 5 G Millimeter Waves on Male Reproductive Outcomes in Mice

Abstract

Background: The biological impact of prolonged exposure to 5 G millimeter-wave frequencies (FR2) on male reproductive health remains insufficiently characterized despite the global deployment of this technology in the near future. Here, we investigated the effects of chronic 27.5 GHz FR2 exposure on testicular function and sperm quality in three mouse strains with distinct genetic backgrounds (Car-S, CD1, and C57BL/6 J). Methods: Adult males (8-weeks old at the onset of the study) were exposed for 100 days to low (6.67 W/m²) or high (20 W/m²) power density, or were SHAM-exposed. Reproductive parameters were assessed through testicular histopathology, serum testosterone measurement, and quantitative and qualitative sperm analyses. Results: Continuous temperature monitoring and dosimetry confirmed that exposure remained strictly non-thermal throughout the experiments. The average ambient temperature recorded during the study was 22.8°C, while the mean whole-body specific absorption rate (SAR) was 0.26 W/kg and 0.77 W/kg under the LPD and HPD exposure conditions, respectively. Car-S mice showed significant reductions in sperm concentration and motility, increased tail abnormalities, and alterations in testicular architecture and testosterone levels, irrespective of prior carcinogen treatment administered for the evaluation of skin carcinogenesis. CD1 mice were largely resistant, displaying preserved sperm parameters with only minor morphological defects, whereas C57BL/6 J mice exhibited intermediate sensitivity, with reduced sperm viability and motility but normal concentration, morphology, and histology. Conclusions: These findings demonstrate that genetic background strongly influences susceptibility to long-term 27.5 GHz FR2 exposure, highlighting the importance of integrating functional sperm endpoints and population heterogeneity in human health risk assessment.

AI evidence extraction

Main findings

Car-S mice had reduced sperm concentration and motility, more tail abnormalities, and altered testicular architecture and testosterone levels. CD1 mice largely retained normal sperm parameters, while C57BL/6 J mice showed reduced sperm viability and motility without changes in concentration, morphology, or histology. The reported whole-body SARs were 0.26 and 0.77 W/kg for the low- and high-power-density conditions, respectively.

Outcomes measured

• Sperm concentration, motility, viability, and morphology
• Testicular histopathology
• Serum testosterone

{
    "study_type": "animal",
    "exposure": {
        "band": "5G millimeter wave (FR2)",
        "source": null,
        "frequency_mhz": 27500,
        "sar_wkg": null,
        "duration": "100 days"
    },
    "population": "Adult male Car-S, CD1, and C57BL/6 J mice",
    "sample_size": null,
    "outcomes": [
        "Sperm concentration, motility, viability, and morphology",
        "Testicular histopathology",
        "Serum testosterone"
    ],
    "main_findings": "Car-S mice had reduced sperm concentration and motility, more tail abnormalities, and altered testicular architecture and testosterone levels. CD1 mice largely retained normal sperm parameters, while C57BL/6 J mice showed reduced sperm viability and motility without changes in concentration, morphology, or histology. The reported whole-body SARs were 0.26 and 0.77 W/kg for the low- and high-power-density conditions, respectively.",
    "effect_direction": "mixed",
    "limitations": [],
    "evidence_strength": "low",
    "confidence": 0.95999999999999996447286321199499070644378662109375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "5G",
        "FR2",
        "27.5 GHz",
        "millimeter waves",
        "male reproduction",
        "sperm quality",
        "mouse strains",
        "non-thermal exposure"
    ],
    "suggested_hubs": []
}

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