Dosimetric Uncertainties: Magnetic Field Coupling to Peripheral Nerve

Area of Science:

• Electromagnetism and Health
• Biophysics
• Radiation Protection Standards

Background:

• International guidelines from ICNIRP and IEEE set magnetic field exposure limits to prevent peripheral nerve stimulation (PNS).
• A significant divergence exists between ICNIRP and IEEE limits between 3.35-100 kHz, impacting public safety assessments.
• Understanding dosimetric uncertainties is crucial for accurate exposure limit evaluations.

Purpose of the Study:

• To analyze the discrepancy in magnetic field exposure limits set by ICNIRP and IEEE.
• To evaluate the dosimetric relationships between external magnetic fields and induced electric fields at the PNS threshold.
• To assess the inherent uncertainties in these dosimetric relationships.

Main Methods:

• Combined experimental data from human subjects exposed to magnetic fields with published estimates of induced electric field PNS thresholds.
• Evaluated dosimetric relationships of external magnetic fields to induced fields at the PNS threshold.
• Analyzed coupling coefficients relating external fields to induced electric fields in peripheral nerves.

Main Results:

• The logarithmic range of magnetic field thresholds constrains the uncertainty bounds for in situ electric field PNS thresholds and nerve coupling coefficients.
• ICNIRP's public exposure limit uses a coupling coefficient above dosimetric uncertainty bounds; IEEE's falls within the lower end of uncertainty bounds.
• Dosimetric estimates can be derived without computational dosimetry or tissue conductivity values.

Conclusions:

• The study provides insights into the dosimetric basis for differing ICNIRP and IEEE magnetic field exposure limits.
• Identified constraints on coupling coefficients could facilitate re-evaluation and potential harmonization of ICNIRP and IEEE limits.
• The findings support a more accurate assessment of public exposure to magnetic fields and potential health risks.