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Magnetic Fields (ELF)

Frequency spectra from current vs. magnetic flux density measurements for mobile phones and other electrical appliances.

No Effects Found

Straume A, Johnsson A, Oftedal G, Wilén J · 2007

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Common EMF measurement shortcuts can overestimate phone exposures by 220% or underestimate appliance exposures by 230%, undermining research reliability.

Plain English Summary

Summary written for general audiences

Norwegian researchers compared two methods for measuring electromagnetic field exposure from mobile phones and household appliances like hair dryers and electric drills. They found that using battery current measurements (a common shortcut in research) can overestimate phone exposures by up to 220% or underestimate appliance exposures by up to 230% compared to direct magnetic field measurements. This means many EMF exposure studies may have inaccurate data, highlighting the need for more precise measurement techniques.

Why This Matters

This study reveals a critical flaw in how EMF exposure is often measured and reported. When researchers take shortcuts by measuring battery current instead of actual magnetic fields, they can be off by more than double in either direction. This matters enormously for the broader EMF health debate because inaccurate exposure measurements make it nearly impossible to establish reliable dose-response relationships or compare studies meaningfully. The reality is that if we can't measure exposure accurately, we can't properly assess health risks. While this particular study found no devices exceeded safety guidelines at normal distances, the measurement discrepancies it uncovered call into question the reliability of exposure data in countless other studies. What this means for you is that EMF research may be even more uncertain than it appears, and the true exposure levels from your devices could be significantly different from what manufacturers or researchers report.

Exposure Information

A logarithmic frequency spectrum from 10 Hz to 100 GHz showing where this study's 217 Hz - 2.4 kHz exposure sits relative to common EMF sources.Where This Frequency Sits on the EMF SpectrumELFVLFLF / MFHF / VHFUHFSHFmm10 Hz100 GHzThis study: 217 Hz - 2.4 kHzPower lines50/60 HzCell phones~1 GHzWiFi2.4 GHz5G mm28 GHzLogarithmic scale

Specific exposure levels were not quantified in this study. The study examined exposure from: 217 Hz to 2.4 kHz

Study Details

The frequency spectra of electromagnetic fields have to be determined to evaluate human exposure in accordance to ICNIRP guidelines. In the literature, comparisons with magnetic field guidelines have been performed by using the frequency distribution of the current drawn from the battery. In the present study we compared the frequency spectrum in the range 217 Hz to 2.4 kHz of the magnetic flux density measured near the surface of a mobile phone with the frequency spectrum of the supply current

By using the multiple frequency rule, recommended in the ICNIRP guidelines, we estimated the magneti...

The frequency distributions obtained from the two measurement methods are not equal. The frequency c...

There was no indication that the devices studied would exceed the reference levels at the working distances normally used.

Cite This Study
Straume A, Johnsson A, Oftedal G, Wilén J (2007). Frequency spectra from current vs. magnetic flux density measurements for mobile phones and other electrical appliances. Health Phys. 93(4):279-287, 2007.
Show BibTeX
@article{a_2007_frequency_spectra_from_current_3426,
  author = {Straume A and Johnsson A and Oftedal G and Wilén J},
  title = {Frequency spectra from current vs. magnetic flux density measurements for mobile phones and other electrical appliances.},
  year = {2007},
  
  url = {https://pubmed.ncbi.nlm.nih.gov/17846524/},
}
PubMed: 17846524

Cited By (4 papers)

Quick Questions About This Study

Norwegian research found mobile phones produce magnetic fields well below safety reference levels at normal usage distances. However, the study revealed that common measurement methods can overestimate phone magnetic field exposure by up to 220%, suggesting many EMF studies may contain inaccurate data.
A 2007 study found hair dryers produce magnetic fields within safe reference levels during typical use. The research showed that indirect measurement methods commonly used in EMF studies can underestimate hair dryer magnetic field exposure by up to 230% compared to direct measurements.
Research on electric drills, hair dryers, and fluorescent lamps found these appliances produce magnetic fields within established safety limits at normal working distances. The study emphasized that accurate EMF exposure assessment requires direct magnetic field measurements rather than electrical current shortcuts.
Electric drills generate magnetic fields that remain below safety reference levels at typical working distances, according to Norwegian researchers. The study found that common measurement techniques used in EMF research can underestimate drill magnetic field exposure by significant amounts.
A 2007 Norwegian study revealed that many EMF studies may contain inaccurate data because researchers use electrical current measurements instead of direct magnetic field measurements. This shortcut can overestimate mobile phone exposures by 220% or underestimate appliance exposures by 230%.