Plasma concentrations of thyroxine in dairy cows exposed to 60 Hz electric and magnetic fields.

Bioelectromagnetics · 2006 · Mixed · Low evidence

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MixedLow evidencePaper 5130

Study snapshot

PublicationBioelectromagnetics · 2006

Study typeanimal

Reported directionMixed

Evidence ratingLow

Abstract

Two experiments were carried out to assess the effects of electric and magnetic fields (EMF) on blood thyroxine (T4) in dairy cattle. In experiment 1, 16 lactating pregnant Holstein cows were exposed to 10 kV/m, 30 microTesla (microT) EMF. The animals were divided into two groups of eight animals each. Each group was exposed to EMF according to one of two treatment sequences of three periods of 28 days each. Sequence 1 was EMF OFF-ON-OFF and sequence 2 was EMF ON-OFF-ON. During the last day of each treatment period, blood samples were collected every 4 h for 24 h to estimate T4 plasma concentrations. In experiment 2, 16 nonlactating, nonpregnant, multiparous Holsteins were exposed to 10 kV/m, 30 microT EMF. The animals were divided into two groups of eight animals each. Each group was exposed to EMF according to one of the two treatment sequences described above, except that each period amounted to the number of days corresponding to one estrous cycle. During treatment, blood samples were collected every other day for T4 analysis. In both experiments, the light cycle emulated a short photoperiod (8 h light/16 h dark). During the ON periods, the animals were exposed to EMF for 16 h, 8 h of the light period plus the first 8 h of during the dark period. In experiment 1, exposed animals did not have any change in T4 plasma concentrations due to treatment (P = .0968), but, the time of sample collection revealed a significant difference (P = .0012). In experiment 2, the effect of period (P = .0009) and the treatment by days interaction (P = .0003) were statistically significant. We conclude that a worst case scenario exposure of dairy cattle to 10 kV/m, 30 microT EMF influences, in a moderate fashion, the blood levels of thyroxine.

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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 directionmixed

PopulationHolstein dairy cows (lactating pregnant; and nonlactating, nonpregnant, multiparous)

Sample size32

ExposureELF · Experiment 1: three periods of 28 days each (OFF-ON-OFF or ON-OFF-ON); EMF ON exposure 16 h/day. Experiment 2: three periods each lasting one estrous cycle (OFF-ON-OFF or ON-OFF-ON); EMF ON exposure 16 h/day.

Evidence strengthLowConfidence: 78% · Peer reviewed: yes

Main findings

Two experiments in Holstein cows exposed to 60 Hz fields (10 kV/m electric field; 30 µT magnetic field) found no statistically significant treatment effect on T4 in experiment 1 (P = .0968), while experiment 2 showed statistically significant effects of period (P = .0009) and a treatment-by-days interaction (P = .0003). The authors conclude this “worst case scenario” exposure moderately influences blood thyroxine levels.

Outcomes measured

Plasma thyroxine (T4) concentrations

Limitations

Exposure described as combined electric and magnetic fields; effects of each component cannot be separated from the abstract.
Details of direction/magnitude of T4 changes are not provided in the abstract.
Animal study; generalizability to humans not addressed in the abstract.

View raw extracted JSON

{
  "study_type": "animal",
  "exposure": {
    "band": "ELF",
    "source": null,
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": "Experiment 1: three periods of 28 days each (OFF-ON-OFF or ON-OFF-ON); EMF ON exposure 16 h/day. Experiment 2: three periods each lasting one estrous cycle (OFF-ON-OFF or ON-OFF-ON); EMF ON exposure 16 h/day."
  },
  "population": "Holstein dairy cows (lactating pregnant; and nonlactating, nonpregnant, multiparous)",
  "sample_size": 32,
  "outcomes": [
    "Plasma thyroxine (T4) concentrations"
  ],
  "main_findings": "Two experiments in Holstein cows exposed to 60 Hz fields (10 kV/m electric field; 30 µT magnetic field) found no statistically significant treatment effect on T4 in experiment 1 (P = .0968), while experiment 2 showed statistically significant effects of period (P = .0009) and a treatment-by-days interaction (P = .0003). The authors conclude this “worst case scenario” exposure moderately influences blood thyroxine levels.",
  "effect_direction": "mixed",
  "limitations": [
    "Exposure described as combined electric and magnetic fields; effects of each component cannot be separated from the abstract.",
    "Details of direction/magnitude of T4 changes are not provided in the abstract.",
    "Animal study; generalizability to humans not addressed in the abstract."
  ],
  "evidence_strength": "low",
  "confidence": 0.78,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "dairy cattle",
    "Holstein cows",
    "thyroxine",
    "T4",
    "endocrine",
    "electric field",
    "magnetic field",
    "ELF",
    "60 Hz",
    "10 kV/m",
    "30 microTesla",
    "photoperiod"
  ],
  "suggested_hubs": [
    {
      "slug": "occupational-exposure",
      "weight": 0.25,
      "reason": "Study involves controlled exposure of animals to 60 Hz electric and magnetic fields, relevant to ELF exposure scenarios."
    }
  ]
}

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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: 10.1002/bem.20253
PubMed: 16724328

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