Toxicology and carcinogenesis studies in Sprague Dawley (Hsd:Sprague Dawley SD) rats exposed to whole-body radio frequency radiation at a frequency (900 MHz) and modulations (GSM and CDMA) used by cell phones

Abstract

The predominant source of human exposure to radio frequency radiation (RFR) occurs through usage of cellular phone handsets. The Food and Drug Administration nominated cell phone RFR emission for toxicology and carcinogenicity testing in 1999. At that time, animal experiments were deemed crucial because meaningful human exposure health data from epidemiological studies were not available. Male and female Sprague Dawley (Hsd:Sprague Dawley SD) rats were exposed to time-averaged whole-body specific absorption rates of Global System for Mobile Communications (GSM)- or Code Division Multiple Access (CDMA)-modulated cell phone RFR at 900 MHz in utero, during lactation, and after weaning for 28 days or 2 years. Genetic toxicology studies were conducted in rat peripheral blood erythrocytes and leukocytes, brain cells, and liver cells. (Abstract Abridged). Genetic toxicology Comet assay As part of the 14-week interim evaluation, samples of frontal cortex, hippocampus, cerebellum, liver, and blood leukocytes were evaluated for DNA damage using the comet assay (two sexes, two cell phone RFR modulations, and five tissues per animal). Samples of peripheral blood from these same animals were also evaluated for chromosome damage in the micronucleus assay. Results in the comet assay are based on the 100-cell scoring approach that was standard at the time of the studies; data obtained using a second, 150-cell scoring approach recommended in a recently adopted international guideline for the in vivo comet assay, are noted for the few instances where results differed between the two methods. A significant increase in DNA damage (% tail DNA) was observed in hippocampus cells of male rats exposed to the CDMA modulation. Although the levels of DNA damage in hippocampus cells were also increased in an exposure-related fashion using the 150-cell scoring approach, the increases were not statistically significant. An exposure-related increase in DNA damage seen in the cells of the frontal cortex of male rats exposed to the CDMA modulation was judged to be equivocal based on a significant trend test. Although results from scoring 100 cells were negative for male rat blood leukocytes exposed to either CDMA or GSM modulations, the results (both CDMA and GSM) were judged to be equivocal when evaluated using the 150-cell scoring method. No statistically significant increases in DNA damage were observed in any of the female rat samples scored with the 100-cell approach; with the 150-cell approach, results in peripheral blood leukocytes of female rats (CDMA) were judged to be equivocal. Micronucleus assay No significant increases in micronucleated red blood cells or changes in the percentage of immature erythrocytes among total erythrocytes were observed in peripheral blood of rats of either sex exposed to either modulation of cell phone RFR. Conclusions GSM-modulated RFR Under the conditions of this 2-year whole-body exposure study, there was clear evidence of carcinogenic activity (see a summary of the peer review panel comments and the public discussion on this Technical Report in Appendix L) of GSM-modulated cell phone RFR at 900 MHz in male Hsd:Sprague Dawley SD rats based on the incidences of malignant schwannoma of the heart. The incidences of malignant glioma of the brain and benign, malignant, or complex pheochromocytoma (combined) of the adrenal medulla were also related to RFR exposure. The incidences of benign or malignant granular cell tumors of the brain, adenoma or carcinoma (combined) of the prostate gland, adenoma of the pars distalis of the pituitary gland, and pancreatic islet cell adenoma or carcinoma (combined) may have been related to RFR exposure. There was equivocal evidence of carcinogenic activity of GSM-modulated cell phone RFR at 900 MHz in female Hsd:Sprague Dawley SD rats based on the incidences of schwannomas of the heart. Increases in nonneoplastic lesions of the heart, brain, and prostate gland in male rats, and of the heart, thyroid gland, and adrenal gland in female rats occurred with exposures to GSM-modulated RFR at 900 MHz. CDMA-modulated RFR Under the conditions of this 2-year whole-body exposure study, there was clear evidence of carcinogenic activity (see a summary of the Peer Review Panel comments and the public discussion on this Technical Report in Appendix L) of CDMA-modulated cell phone RFR at 900 MHz in male Hsd:Sprague Dawley SD rats based on the incidences of malignant schwannoma of the heart. The incidences of malignant glioma of the brain were also related to RFR exposure. The incidences of adenoma of the pars distalis of the pituitary gland and adenoma or carcinoma (combined) of the liver may have been related to RFR exposure. There was equivocal evidence of carcinogenic activity of CDMA-modulated cell phone RFR at 900 MHz in female Hsd:Sprague Dawley SD rats based on the incidences of malignant schwannoma of the heart, malignant glioma of the brain, and benign, malignant, or complex pheochromocytoma (combined) of the adrenal medulla. Increases in nonneoplastic lesions of the heart, brain, and prostate gland in male rats, and of the brain in female rats occurred with exposures to CDMA-modulated RFR at 900 MHz. National Toxicology Program (NTP). 2018. Technical report on the toxicology and carcinogenesis studies in Sprague Dawley (Hsd:Sprague Dawley SD) rats exposed to whole-body radio frequency radiation at a frequency (900 Mhz) and modulations (GSM and CDMA) used by cell phones. Research Triangle Park, NC: National Toxicology Program. NTP Technical Report 595. doi.org

AI evidence extraction

Main findings

Clear evidence of carcinogenic activity of GSM- and CDMA-modulated cell phone RFR at 900 MHz in male rats based on malignant schwannoma of the heart and malignant glioma of the brain. Equivocal evidence in female rats. Some increases in nonneoplastic lesions and equivocal increases in DNA damage in certain brain regions were observed. No significant increases in micronucleated red blood cells were found.

Outcomes measured

• malignant schwannoma of the heart
• malignant glioma of the brain
• pheochromocytoma of the adrenal medulla
• granular cell tumors of the brain
• adenoma or carcinoma of the prostate gland
• adenoma of the pars distalis of the pituitary gland
• pancreatic islet cell adenoma or carcinoma
• nonneoplastic lesions of heart, brain, prostate gland, thyroid gland, adrenal gland
• DNA damage in hippocampus and frontal cortex cells
• micronucleus assay results

Limitations

• Study conducted in rats, which may not fully extrapolate to humans
• Some equivocal findings and statistical significance varies by assay method
• Specific absorption rates not detailed in abstract

Suggested hubs

• occupational-exposure (0.3)
  Animal toxicology study on cell phone RFR exposure relevant to occupational and general exposure contexts.
• who-icnirp (0.7)
  Study on carcinogenicity of cell phone RFR at 900 MHz relevant to exposure guidelines.

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    "study_type": "animal",
    "exposure": {
        "band": "RF",
        "source": "cell phone",
        "frequency_mhz": 900,
        "sar_wkg": null,
        "duration": "in utero, lactation, and after weaning for 28 days or 2 years"
    },
    "population": "Sprague Dawley (Hsd:Sprague Dawley SD) rats, male and female",
    "sample_size": null,
    "outcomes": [
        "malignant schwannoma of the heart",
        "malignant glioma of the brain",
        "pheochromocytoma of the adrenal medulla",
        "granular cell tumors of the brain",
        "adenoma or carcinoma of the prostate gland",
        "adenoma of the pars distalis of the pituitary gland",
        "pancreatic islet cell adenoma or carcinoma",
        "nonneoplastic lesions of heart, brain, prostate gland, thyroid gland, adrenal gland",
        "DNA damage in hippocampus and frontal cortex cells",
        "micronucleus assay results"
    ],
    "main_findings": "Clear evidence of carcinogenic activity of GSM- and CDMA-modulated cell phone RFR at 900 MHz in male rats based on malignant schwannoma of the heart and malignant glioma of the brain. Equivocal evidence in female rats. Some increases in nonneoplastic lesions and equivocal increases in DNA damage in certain brain regions were observed. No significant increases in micronucleated red blood cells were found.",
    "effect_direction": "harm",
    "limitations": [
        "Study conducted in rats, which may not fully extrapolate to humans",
        "Some equivocal findings and statistical significance varies by assay method",
        "Specific absorption rates not detailed in abstract"
    ],
    "evidence_strength": "moderate",
    "confidence": 0.6999999999999999555910790149937383830547332763671875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "radio frequency radiation",
        "cell phone",
        "carcinogenesis",
        "Sprague Dawley rats",
        "GSM",
        "CDMA",
        "DNA damage",
        "toxicology"
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