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Neurodevelopmental anomalies of the hippocampus in rats exposed to weak intensity complex magnetic fields throughout gestation.

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Fournier NM, Mach QH, Whissell PD, Persinger MA. · 2012

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Weak magnetic fields during pregnancy permanently damaged rat brain development at levels commonly found near power lines and home wiring.

Plain English Summary

Summary written for general audiences

Researchers exposed pregnant rats to extremely weak magnetic fields (similar to power line levels) throughout pregnancy and found that specific exposure levels caused permanent brain damage in the offspring. The baby rats exposed to low-intensity fields (30-50 nT) developed smaller hippocampus regions and showed impaired learning abilities as adults. Interestingly, both weaker and stronger magnetic field exposures didn't cause these problems, suggesting a narrow 'danger zone' of exposure intensity.

Why This Matters

This study reveals a troubling reality about prenatal EMF exposure: even incredibly weak magnetic fields can permanently alter brain development when exposure occurs during critical developmental windows. The exposure levels that caused brain damage (30-50 nT) are well within the range of everyday magnetic field exposures from power lines, electrical wiring, and household appliances. What makes this research particularly significant is the 'window effect' it demonstrates - only a specific range of intensities caused damage, which helps explain why EMF research sometimes produces conflicting results. The hippocampus damage observed here affects learning and memory formation, functions critical for normal cognitive development. This adds to growing evidence that the developing brain is uniquely vulnerable to EMF exposure, supporting the need for enhanced protection of pregnant women and children from these ubiquitous environmental exposures.

Exposure Details

Magnetic Field
0.00002, 0.00005, 0.00058, 0.0012 mG
Source/Device
50 Hz
Exposure Duration
24 h/day during gestation (21 days)

Where This Falls on the Concern Scale

Study Exposure Level in ContextA logarithmic scale showing exposure levels relative to Building Biology concern thresholds and regulatory limits.Study Exposure Level in ContextThis study: 0.00002, 0.00005, 0.00058, 0.0012 mGExtreme Concern5 mGFCC Limit2,000 mGEffects observed in the No Concern range (Building Biology)FCC limit is 100,000,000x higher than this exposure level

Study Details

To investigate the effect of weak intensity magnetic fields on the prenatal brain, pregnant Wistar rats were continuously exposed to one of four intensities (reference: 5–20 nT; low 30–50 nT; medium 90–580 nT; high 590–1200 nT) of a complex magnetic field sequence designed to interfere with brain development.

As adults, rats exposed to the low-intensity (30–50 nT) complex magnetic field displayed impairments...

These findings suggest that prenatal exposure to complex magnetic fields of a narrow intensity window during development can result in subtle but permanent alterations in hippocampal microstructure and function that can have lasting effects on behavior.

Cite This Study
Fournier NM, Mach QH, Whissell PD, Persinger MA. (2012). Neurodevelopmental anomalies of the hippocampus in rats exposed to weak intensity complex magnetic fields throughout gestation. Int J Dev Neurosci. 2012 Oct;30(6):427-433.
Show BibTeX
@article{nm_2012_neurodevelopmental_anomalies_of_the_249,
  author = {Fournier NM and Mach QH and Whissell PD and Persinger MA. },
  title = {Neurodevelopmental anomalies of the hippocampus in rats exposed to weak intensity complex magnetic fields throughout gestation.},
  year = {2012},
  
  url = {https://www.sciencedirect.com/science/article/abs/pii/S0736574812004364},
}

Quick Questions About This Study

Researchers exposed pregnant rats to extremely weak magnetic fields (similar to power line levels) throughout pregnancy and found that specific exposure levels caused permanent brain damage in the offspring. The baby rats exposed to low-intensity fields (30-50 nT) developed smaller hippocampus regions and showed impaired learning abilities as adults. Interestingly, both weaker and stronger magnetic field exposures didn't cause these problems, suggesting a narrow 'danger zone' of exposure intensity.