Human body exposure to power lines: relation of induced quantities to external magnetic fields.
Induced electric field and corresponding current density values in various organs of the human body can be computed numerically using a heterogeneous, anatomically representative voxel model. Such computations are available for uniform magnetic fields of various directions with respect to the body. The highest exposure levels occur for non-uniform fields, most often in occupational settings. Various organ induced dosimetric measures of the induced quantities can also be computed, although the associated computational complexity and effort are greater than for uniform fields. A simplified method of estimation of the induced measures is described and validated. The method is based on evaluation of the external (exposure) magnetic flux density in locations corresponding to those occupied by various organs and dosimetry for the uniform fields. Computations of the external fields are relatively simple even for very complex geometries of current-carrying conductors. Computational methods are available for external fields. The external magnetic fields can also be measured. Detailed organ dosimetry is already published. In this contribution, the proposed simplified dosimetry is verified using accurate, numerically computed dosimetry for four non-uniform field exposure scenarios. For most dosimetric measures and organs, the proposed method gives conservative estimates. Only in rare cases when a large organ is in a weak exposure field compared to the whole-body average exposure, the induced dosimetric measures may be underestimated by up to 10%. Another exception is the maximum induced electric field in spatially distributed tissues such as bone marrow, muscle, or skin when a part of the limb is in a very strong magnetic field close to the conductor. However, both of these situations are easily recognizable from the mutual configuration of the human body and the current-carrying conductors. Thus, additional corrections can be applied to the estimates.
Stuchly
M A
MA
Department of Electrical and Computer Engineering, University of Victoria, BC Canada. mstuchly@ece.uvic.ca
Dawson
T W
TW
D003198:Computer Simulation; D004574:Electromagnetic Fields / Q000009:adverse effects*; D004781:Environmental Exposure; D006801:Humans; D008280:Magnetics; D008962:Models, Theoretical; D011874:Radiometry / Q000379:methods