13/03/2012
Children and Adults Exposed to Low Frequency Magnetic Fields at the ICNIRP Reference Levels: Theoretical Assessment of the Induced Electric Fields
Jurriaan F. Bakker, Maarten M. Paulides, Esra Neufeld, Andreas Christ, Xi Lin Chen, Niels Kuster, and Gerard van Rhoon, Physics in Medicine and Biology, Volume 57, Number 7, pp. 1815–1829, April 2012, online March 13
Recently, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) has issued revised guidelines on the exposure of the human body to low frequency electric and magnetic fields. While the rationale for the definition of the basic restrictions has remained the same — nerve stimulation and induction of phosphenes — the induced electric field averaged over a volume of 2×2×2mm³ has been defined as a new metric for the basic restrictions. Moreover, the new guidelines provide recommendations to minimize the impact of numerical artifacts (stair-casing errors) when assessing the exposure using anatomical computer models of the human body.
The objective of this study is to show whether the electric fields induced in adults and children remain below the basic restrictions for exposure at the reference levels. The exposure was evaluated using the scalar potential finite element method implemented in SEMCAD X to calculate the induced fields in six child and two adult models of the Virtual Population exposed to a homogeneous magnetic field at three different polarizations covering a frequency range from 1Hz to 100kHz.
The scientific and technical impact of the study can be summarized as:
- The basic restrictions on the induced electric fields are not exceeded for the evaluated anatomies and postures at the reference levels for the general public. At occupational exposure, the basic restrictions for peripheral nerve stimulation can be exceeded by >50%. For other postures, the induced fields are expected to be even larger.
- The results determined according the new recommendations by the ICNIRP depend on mesh resolution, segmentation (tissue volume) and therefore cannot be used to universally determine compliance of sources or exposure situations. Revisions of the recommendations are suggested.