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Interaction of Extremely Low–Frequency Electromagnetic Fields
4.5 Coupling and Dosimetry of ELF EMF
with Biological Systems
The dielectric property of tissues, the basic concept of electromagnetic coupling of ELF EMF
and biological systems, and several calculation methods and models were briefly introduced
in the previous three sections. These aspects are very important for both experimental and
numerical dosimetries concerning the estimation of induced currents and internal electric
fields inside biological systems, human beings in particular. In this section, the scientific
evolution of ELF EMF dosimetry and its application to the human body model are reviewed.
The homogeneous human (or animal) body with a single conductivity was modeled
in ELF EMF. The dosimetry involves the coupling between ELF EMF and biological systems and the measurement or calculation of the internal induced currents and electric
fields inside the biological systems during and after exposures. In previous dosimetric
studies, simple human and animal models were used to calculate the amount of induced
electrical quantities. In recent years, advances in computer technology, along with
the development of hardware and commercially available software, have made it possible to perform calculations using complex models. Simple geometric models such as
the spherical, rotating ellipsoid, oblong, and cylindrical models approximate the human
body form; the induced current distributions in the body can be calculated analytically.
Information on internal electric field strengths or induced current densities inside the
biological systems has been obtained through experiments using a scaled human model
or a full-size mannequin. At the ELF region, the electric and magnetic fields can be supposed to be decoupled. So, it is possible to study and compute independently the induced
electrical quantities inside the human body.
4.5.1 ELF Electric Field
Several steps are involved in the development of dosimetry of the electric field effects.
First, the analytical method for estimating the electric fields and body surface charge
densities is applied using a simple human model. At the intermediate stage, an anatomically more realistic human model is used for the computation of induced electric fields
and induced currents. From the end of the 1990s, computation has been based on MRIbased high-resolution human models with different organ conductivities.
The electric field is disturbed on the surface of a conductive object due to nearby
human beings, trees, houses, etc. So, the value of the exposure electric field, called
unperturbed electric field, is used as the field strength before the introduction of such
objects. In the case of ELF electric field dosimetry, it has been assumed that the electric
fields are uniform and are vertically directed to the object such as standing under a
transmission line. Depending on the direction of the object to the applied electric field
and its strength, the electric fields and induced current densities vary.
4.5.1.1 Coupling with Simple and Analytical Models
Quantification of the electric fields and induced currents in the human body when
exposed to transmission lines has been a very important issue in human health assessment. Between 1970 and 1980, dosimetric studies in the ELF region assessed the human
Interaction of Extremely Low–Frequency Electromagnetic Fields
4.5 Coupling and Dosimetry of ELF EMF
with Biological Systems
The dielectric property of tissues, the basic concept of electromagnetic coupling of ELF EMF
and biological systems, and several calculation methods and models were briefly introduced
in the previous three sections. These aspects are very important for both experimental and
numerical dosimetries concerning the estimation of induced currents and internal electric
fields inside biological systems, human beings in particular. In this section, the scientific
evolution of ELF EMF dosimetry and its application to the human body model are reviewed.
The homogeneous human (or animal) body with a single conductivity was modeled
in ELF EMF. The dosimetry involves the coupling between ELF EMF and biological systems and the measurement or calculation of the internal induced currents and electric
fields inside the biological systems during and after exposures. In previous dosimetric
studies, simple human and animal models were used to calculate the amount of induced
electrical quantities. In recent years, advances in computer technology, along with
the development of hardware and commercially available software, have made it possible to perform calculations using complex models. Simple geometric models such as
the spherical, rotating ellipsoid, oblong, and cylindrical models approximate the human
body form; the induced current distributions in the body can be calculated analytically.
Information on internal electric field strengths or induced current densities inside the
biological systems has been obtained through experiments using a scaled human model
or a full-size mannequin. At the ELF region, the electric and magnetic fields can be supposed to be decoupled. So, it is possible to study and compute independently the induced
electrical quantities inside the human body.
4.5.1 ELF Electric Field
Several steps are involved in the development of dosimetry of the electric field effects.
First, the analytical method for estimating the electric fields and body surface charge
densities is applied using a simple human model. At the intermediate stage, an anatomically more realistic human model is used for the computation of induced electric fields
and induced currents. From the end of the 1990s, computation has been based on MRIbased high-resolution human models with different organ conductivities.
The electric field is disturbed on the surface of a conductive object due to nearby
human beings, trees, houses, etc. So, the value of the exposure electric field, called
unperturbed electric field, is used as the field strength before the introduction of such
objects. In the case of ELF electric field dosimetry, it has been assumed that the electric
fields are uniform and are vertically directed to the object such as standing under a
transmission line. Depending on the direction of the object to the applied electric field
and its strength, the electric fields and induced current densities vary.
4.5.1.1 Coupling with Simple and Analytical Models
Quantification of the electric fields and induced currents in the human body when
exposed to transmission lines has been a very important issue in human health assessment. Between 1970 and 1980, dosimetric studies in the ELF region assessed the human