Aspects of the Effects of Non-ionizing Electromagnetic Radiation on the Human Body

Abstract

The non-ionizing Electromagnetic Radiation (EMR) has recently become a growing concern, with the widespread use of electrical appliances and wireless communications devices. The general exposure limits have already been established in related EMR standards. The dosimetry studies, which evaluate the magnitudes and distribution of in-situ Electromagnetic (EM) fields inside the human body, provide scientific evidence for certain derivation, and supplement the general exposure limits in the EMR standards.
Due to the inhomogeneity of human tissues for the dosimetry studies, the complex geometry of the human critical parts, together with the diversity in different exposure scenarios, lead to varying dosages in different parts of the body; the current dosimetry analysis and modelling are not suitable to be generalized to cover all exposure situations, including EM dosimetry analysis for detailed critical body parts, and modelling of complex EM sources.
In this thesis, computational EM programs are developed for detailed analysis of the human body exposed to EMR, for dosimetry studies. This thesis focuses on two aspects: i) analysis of EM power absorption in critical body parts for Radio Frequency (RF) EM exposure, and ii) source modelling for Low Frequency (LF) EM exposure assessment.
It is found, in a general review of the RF safety standards for the first aspect, that it is a consensus that current researchers share the same opinion that the existing limits for localized RF EM exposures of critical human parts require validation by further dosimetry analysis. A refined human eye model is constructed from the existing biometric data, for the detailed analysis of Specific Absorption Rate (SAR) and temperature rise in the eyes for this purpose. The variations in SAR and temperature rise, caused by the changes in the eye features, such as the eye size, palpebral fissure, and gaze angle, are evaluated for EM dosimetry analysis.
It is also found that, for the LF magnetic exposure of the second aspect, that the standard coil model is inaccurate and inefficient for assessment of induced electric field strength inside the human body for an electrical Appliance-Under-Test. For an accurate and efficient source modelling in dosimetry studies, a novel equivalent magnetic vector potential model is proposed. This novel model requires only a single-component magnetic field to be measured, hence relieving a lot of practical measurement effort – the Radial Basis Functions (RBFs) are adopted for the interpolation of discrete measurements. The magnetic vector potential model can then be directly constructed by superpositioning a set of simple algebraic functions of RBF parameters. It is demonstrated that this model is more accurate and effective than the standard coil source model.
In summary, the work in this thesis provides a refined eye model for detailed SAR and temperature rise analysis in critical body parts, and an accurate source modelling for LF magnetic exposure assessment.

Date of Award	1 Sept 2016
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Sai Wing Peter LEUNG (Supervisor)