RF Safe

Spontaneous and Nitrosourea-induced Primary Tumors of the Central Nervous System in Fischer 344 Rats Exposed to Frequency-modulated Microwave Fields1

1999 · No effect · Moderate evidence

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No effectModerate evidencePaper 6664

Across six groups (n=90/group; total n=540), FM RF exposure (836.55 MHz) produced no observed changes in survival, number/incidence, or histological type of spontaneous or ENU-induced CNS tumors. ENU significantly increased CNS tumor incidence and reduced sur…

Study snapshot

Publicationmanual · 1999
Study typeanimal
Reported directionNo effect
Evidence ratingModerate

Abstract

In a 2-year bioassay, we exposed Fischer 344 rats to a frequencymodulated (FM) signal (836.55 MHz 6 12.5 KHz deviation) simulating radiofrequency exposures in the head of users of hand-held mobile phones. We tested for effects on spontaneous tumorigenicity of central nervous system (CNS) tumors in the offspring of pregnant rats and also for modified incidence of primary CNS tumors in rats treated with a single dose of the neurocarcinogen ethylnitrosourea (ENU) in utero. ENU dosage (4 mg/kg) was selected to give an expected brain tumor incidence of 10–15% over the mean life span of 26 months. Pregnant dams (n 5 102) were randomly assigned to six groups. Their offspring were treated as cohorts in each of the six groups (n 5 90 per group; total, n 5 540): Sham ENU/Sham Field, Sham ENU/Field Exposed, ENU/Sham Field, ENU/Field Exposed, ENU/Cage Control, and Sham ENU/Cage Control. Intermittent field exposures began on gestation day 19 and continued until weaning at 21 days, resuming thereafter at 31 days and continuing until experiment termination at 731–734 days. Energy absorption rates (SARs) in the rats’ brains were similar to localized peak brain exposures of a phone user (female, 236 g, 1.0 W/kg; male, 450 g, 1.2 W/kg). Of the original 540 rats, 168 died before the termination of the experiment. In these rats, ENU significantly reduced survival from a mean of 708 days in three groups without ENU treatment to 645 days in three groups treated with ENU (P < 0.0005). There were no effects on survival attributable to FM field exposure in either ENU-treated or in sham-treated groups. Spontaneous CNS tumor incidence in control groups was 1.1–4.4% but sharply higher in rats receiving ENU (14.4–22.2%; P < 0.0001). No FM field-mediated changes were observed in number, incidence, or histological type of either spontaneous or ENU-induced brain tumors, nor were gender differences detected in tumor numbers. These negative findings with FM fields contrast with our study using standard digital phone fields pulsed on and off at 50/se, where a trend was noted toward reduced incidence of both spontaneous and ENU-induced CNS tumors (W. R. Adey et al., Radiat. Res., 152: 293–302, 1999). Although consistent but not attaining significance in the experiment overall (spontaneous CNS tumors, P < 0.08 one-tailed; P < 0.16 two-tailed; ENU-induced CNS tumors, P < 0.08 one-tailed, P < 0.16 two-tailed), the trend was significant (P < 0.015 one-tailed, P < 0.03, two-tailed) in rats that received ENU and died prior to experiment termination, with a primary brain tumor as the cause of death. We discuss differences in the signaling structure of digital and FM fields. Certain bioeffects induced by either amplitude-modulated or pulsed radiofrequency fields at athermal levels have not been seen with fields of similar average power but unvarying in intensity (continuous wave or frequency-modulated fields).

Machine Enhanced Logic

AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typeanimal
Effect directionno_effect
PopulationFischer 344 rats (offspring of pregnant dams), including in utero ENU-treated and sham-treated cohorts
Sample size540
ExposureRF · 836.55 MHz · 1.2 W/kg · Intermittent exposures from gestation day 19 to weaning (21 days), resumed at 31 days and continued until termination at 731–734 days
Evidence strengthModerateConfidence: 78% · Peer reviewed: yes

Main findings

Across six groups (n=90/group; total n=540), FM RF exposure (836.55 MHz) produced no observed changes in survival, number/incidence, or histological type of spontaneous or ENU-induced CNS tumors. ENU significantly increased CNS tumor incidence and reduced survival, but these effects were not attributed to FM field exposure.

Outcomes measured

  • Spontaneous CNS tumor incidence
  • ENU-induced primary CNS tumor incidence
  • Number of CNS tumors
  • Histological type of CNS tumors
  • Survival

Limitations

  • Exposure described as simulating localized head exposure; detailed dosimetry beyond peak brain SAR not provided in abstract
  • 168/540 animals died before experiment termination; impact on tumor ascertainment not detailed in abstract
  • Intermittent exposure schedule is described but specific daily exposure durations are not stated in abstract
View raw extracted JSON
{
  "study_type": "animal",
  "exposure": {
    "band": "RF",
    "source": "mobile phone (simulated)",
    "frequency_mhz": 836.55,
    "sar_wkg": 1.2,
    "duration": "Intermittent exposures from gestation day 19 to weaning (21 days), resumed at 31 days and continued until termination at 731–734 days"
  },
  "population": "Fischer 344 rats (offspring of pregnant dams), including in utero ENU-treated and sham-treated cohorts",
  "sample_size": 540,
  "outcomes": [
    "Spontaneous CNS tumor incidence",
    "ENU-induced primary CNS tumor incidence",
    "Number of CNS tumors",
    "Histological type of CNS tumors",
    "Survival"
  ],
  "main_findings": "Across six groups (n=90/group; total n=540), FM RF exposure (836.55 MHz) produced no observed changes in survival, number/incidence, or histological type of spontaneous or ENU-induced CNS tumors. ENU significantly increased CNS tumor incidence and reduced survival, but these effects were not attributed to FM field exposure.",
  "effect_direction": "no_effect",
  "limitations": [
    "Exposure described as simulating localized head exposure; detailed dosimetry beyond peak brain SAR not provided in abstract",
    "168/540 animals died before experiment termination; impact on tumor ascertainment not detailed in abstract",
    "Intermittent exposure schedule is described but specific daily exposure durations are not stated in abstract"
  ],
  "evidence_strength": "moderate",
  "confidence": 0.78,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "Fischer 344 rats",
    "radiofrequency",
    "frequency-modulated",
    "836.55 MHz",
    "SAR",
    "mobile phone simulation",
    "central nervous system tumors",
    "brain tumors",
    "ethylnitrosourea",
    "in utero exposure",
    "2-year bioassay"
  ],
  "suggested_hubs": [
    {
      "slug": "mobile-phones-rf",
      "weight": 0.9,
      "reason": "FM RF signal explicitly simulates head exposure from hand-held mobile phones; brain SARs compared to phone users."
    }
  ]
}
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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: Not supplied
PubMed: Not supplied

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