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Analysis of in situ electric field and specific absorption rate in human models for wireless power transfer system with induction coupling.

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Sunohara T, Hirata A, Laakso I, Onishi T · 2014

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Wireless charging systems operate at EMF levels thousands of times below current safety limits, but those limits may not protect against non-thermal biological effects.

Plain English Summary

Summary written for general audiences

Scientists tested how much electromagnetic energy people absorb from wireless phone charging pads at 140 kHz frequency. They found extremely low absorption levels - 72 nanowatts per kilogram at 1 watt power. This confirms wireless charging systems operate far below safety limits for human exposure.

Why This Matters

This study provides important baseline data for understanding EMF exposure from wireless charging technology, which is becoming ubiquitous in smartphones and electric vehicles. The science demonstrates that current wireless charging systems operate at power levels far below established safety thresholds. However, what this research doesn't address is whether these safety limits themselves are adequate. The reality is that safety guidelines focus primarily on heating effects from EMF exposure, not the growing body of research showing biological effects at much lower, non-thermal levels. While this study suggests wireless charging poses minimal risk under current guidelines, it highlights the need for exposure standards that account for non-thermal biological effects, especially as wireless power transfer technology scales up for electric vehicle charging and other high-power applications.

Exposure Details

SAR
0.000000072, 2 W/kg
Electric Field
0.091, 18.9 V/m

Where This Falls on the Concern Scale

Study Exposure Level in ContextStudy Exposure Level in ContextThis study: 0.000000072, 2 W/kgExtreme Concern - 0.1 W/kgFCC Limit - 1.6 W/kgEffects observed in the No Concern rangeFCC limit is 22,222,222x higher than this level

Study Details

This study investigates the specific absorption rate (SAR) and the in situ electric field in anatomically based human models for the magnetic field from an inductive wireless power transfer system developed on the basis of the specifications of the wireless power consortium.

The transfer system consists of two induction coils covered by magnetic sheets. Both the waiting and...

The results indicate that the peak value of the SAR averaged over a 10 g of tissue and that of the i...

Cite This Study
Sunohara T, Hirata A, Laakso I, Onishi T (2014). Analysis of in situ electric field and specific absorption rate in human models for wireless power transfer system with induction coupling. Phys Med Biol. 59(14):3721-3735, 2014.
Show BibTeX
@article{t_2014_analysis_of_in_situ_1347,
  author = {Sunohara T and Hirata A and Laakso I and Onishi T},
  title = {Analysis of in situ electric field and specific absorption rate in human models for wireless power transfer system with induction coupling.},
  year = {2014},
  
  url = {https://pubmed.ncbi.nlm.nih.gov/24936747/},
}
PubMed: 24936747

Cited By (33 papers)

Quick Questions About This Study

Wireless phone charging appears extremely safe based on scientific testing. A 2014 study found wireless charging pads produce absorption levels of just 72 nanowatts per kilogram - thousands of times below safety limits set by international guidelines.
Wireless charging produces minimal electromagnetic absorption in the human body. Research shows these systems operate at 140 kHz frequency with absorption rates 28 million times lower than safety thresholds, indicating negligible biological impact.
Current evidence suggests wireless charging pads pose no significant health risks. Scientific analysis found their electromagnetic absorption levels are extraordinarily low - far below any threshold where biological effects might occur according to safety standards.
EMF exposure risks from wireless chargers appear minimal. Testing revealed these devices produce electromagnetic field absorption thousands of times below international safety limits, with the chest area showing slightly higher but still negligible exposure levels.
Wireless phone chargers emit extremely low levels of electromagnetic radiation. At 1 watt power, they produce only 72 nanowatts per kilogram of tissue absorption - a level so low it would take millions of times more power to approach safety concerns.