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

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Authors not listed · 2006

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Power line frequency EMF at transmission line levels moderately disrupted thyroid hormone levels in dairy cattle.

Plain English Summary

Summary written for general audiences

Researchers exposed dairy cows to power line frequency electric and magnetic fields (10 kV/m, 30 microTesla at 60 Hz) for 16 hours daily over multiple 28-day periods. The study found moderate changes in blood thyroxine (thyroid hormone) levels, with timing of exposure and reproductive status affecting the results.

Why This Matters

This study adds important evidence that power line EMF can disrupt endocrine function in large mammals. The 30 microTesla magnetic field exposure is significant - that's 600 times stronger than typical home levels (0.05 microTesla) but comparable to what you'd find directly under transmission lines or near electrical substations. The fact that thyroid hormone levels changed in cattle suggests similar effects could occur in humans with chronic high-level exposure. What makes this particularly concerning is that thyroid hormones regulate metabolism, growth, and development throughout the body. The researchers called this a "worst case scenario" exposure, but for people living near power lines or working in electrical facilities, such exposures aren't hypothetical - they're daily reality.

Exposure Information

A logarithmic frequency spectrum from 10 Hz to 100 GHz showing where this study's 60 Hz exposure sits relative to common EMF sources.Where This Frequency Sits on the EMF SpectrumELFVLFLF / MFHF / VHFUHFSHFmm10 Hz100 GHzThis study: 60 HzCell phones~1 GHzWiFi2.4 GHz5G mm28 GHzLogarithmic scale

Specific exposure levels were not quantified in this study.

Cite This Study
Unknown (2006). Plasma concentrations of thyroxine in dairy cows exposed to 60 Hz electric and magnetic fields.
Show BibTeX
@article{plasma_concentrations_of_thyroxine_in_dairy_cows_exposed_to_60_hz_electric_and_magnetic_fields_ce4873,
  author = {Unknown},
  title = {Plasma concentrations of thyroxine in dairy cows exposed to 60 Hz electric and magnetic fields},
  year = {2006},
  doi = {10.1002/bem.20253},
  
}
DOI: 10.1002/bem.20253PubMed: 16724328

Quick Questions About This Study

Yes, dairy cows exposed to 60 Hz EMF at 10 kV/m and 30 microTesla showed moderate changes in blood thyroxine levels. The effects varied based on timing and whether the cows were lactating and pregnant.
The 30 microTesla exposure was extremely high - about 600 times stronger than typical home magnetic field levels. This represents exposure levels found directly under high-voltage transmission lines or near electrical substations.
Yes, the study found that the time of day when blood samples were collected significantly affected thyroxine levels. Cows were exposed to EMF for 16 hours daily, including 8 hours of light and 8 hours of darkness.
Yes, the two experiments showed different response patterns. Lactating pregnant cows showed timing-dependent effects, while non-lactating, non-pregnant cows showed period effects and treatment-day interactions, suggesting reproductive status influences EMF sensitivity.
The researchers used 10 kV/m electric fields and 30 microTesla magnetic fields at 60 Hz - levels typically found only directly under major transmission lines. Most people experience much lower daily exposures from power lines.