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Electromagnetic Fields in Biological Systems
static magnetic fields (SMFs), low-frequency magnetic fields, and pulsed magnetic fields.
Regarding the magnetic sensing mechanism of biological systems, it has been reported
that animals can detect small changes in the geomagnetic field by two distinct mechanisms: (1) using the mineral magnetite as the primary sensor and (2) using magnetically sensitive chemical reactions. Several models have been proposed to account for the
effects of magnetic fields on biological sensing and reactions.
In modern society, there are many sources of electromagnetic fields (EMFs) or
time-varying magnetic fields. Humans are exposed daily to human-made and naturally originated fields. During the past decade, questions about whether the exposure to
EMFs may be linked with adverse health effects have been raised. Although the interaction of nonthermal EMFs, in particular low frequencies up to 300 Hz, with biological
systems has been investigated, there is no biophysical mechanism that can explain many
of the observed biological effects of low and moderate levels of magnetic fields (<1 T).
Proposed mechanisms include effects on electric currents, direct forces on biomagnetic
materials, effects on free radicals, ion cyclotron resonance (ICR), charge transfer processes, stochastic resonance, and a dynamical systems/Larmor procession model, etc
(see the review by Shigemitsu 2006; Pilla 2007).
Recent developments in medical instrumentation such as magnetic resonance imaging (MRI) and transcranial magnetic stimulation (TMS) have raised questions as to
whether strong (in the tesla [T] range) magnetic fields influence human health. Medical
applications of SMFs of moderate intensities (1–200 mT) for pain reduction and tissue
healing have also been studied for many years. Therapeutic applications of permanent
magnets and other electromagnetic devices have recently been expanded to various
areas such as treatments of pain and diseases like rheumatoid arthritis and cancer.
The objective of this chapter is to describe and shed light on some of the more recent
information on the biological effects and medical applications of magnetic fields. A discussion of possible implications of these effects on biological systems is also provided. This
chapter consists of four sections. Each section contains a comprehensive review of a recent
topic of interest. Short summaries of the mechanism of magnetic field action on biological
systems and the biomagnetic phenomena are described in Section 3.2, which includes a
brief review of well-known mechanisms that are discussed before mentioning the interactions of weak SMFs with biological systems including magnetic sensing and sensing using
magnetite as the primary sensor. Section 3.3 reviews and summarizes more recent in vivo
and in vitro experimental results of the effects of magnetic fields including TMS and MRI
fields. Section 3.4 covers special topics including the response of plants to magnetic fields.
In parallel with a comprehensive review on biological effects, the development and medical applications of biomagnetic phenomena are introduced in Section 3.5, and they are
reviewed with emphasis on the applications that are currently under investigation.
3.2 Mechanisms of Biological Effects and
Biomagnetic Phenomena of Magnetic Fields
Table 3.1 shows three types of well-known mechanisms of the biological effects of magnetic fields including SMFs and time-varying magnetic fields (Ueno and Shigemitsu
2007). As shown in Table 3.1, there are two basic mechanisms of SMFs: (1) magnetic
Electromagnetic Fields in Biological Systems
static magnetic fields (SMFs), low-frequency magnetic fields, and pulsed magnetic fields.
Regarding the magnetic sensing mechanism of biological systems, it has been reported
that animals can detect small changes in the geomagnetic field by two distinct mechanisms: (1) using the mineral magnetite as the primary sensor and (2) using magnetically sensitive chemical reactions. Several models have been proposed to account for the
effects of magnetic fields on biological sensing and reactions.
In modern society, there are many sources of electromagnetic fields (EMFs) or
time-varying magnetic fields. Humans are exposed daily to human-made and naturally originated fields. During the past decade, questions about whether the exposure to
EMFs may be linked with adverse health effects have been raised. Although the interaction of nonthermal EMFs, in particular low frequencies up to 300 Hz, with biological
systems has been investigated, there is no biophysical mechanism that can explain many
of the observed biological effects of low and moderate levels of magnetic fields (<1 T).
Proposed mechanisms include effects on electric currents, direct forces on biomagnetic
materials, effects on free radicals, ion cyclotron resonance (ICR), charge transfer processes, stochastic resonance, and a dynamical systems/Larmor procession model, etc
(see the review by Shigemitsu 2006; Pilla 2007).
Recent developments in medical instrumentation such as magnetic resonance imaging (MRI) and transcranial magnetic stimulation (TMS) have raised questions as to
whether strong (in the tesla [T] range) magnetic fields influence human health. Medical
applications of SMFs of moderate intensities (1–200 mT) for pain reduction and tissue
healing have also been studied for many years. Therapeutic applications of permanent
magnets and other electromagnetic devices have recently been expanded to various
areas such as treatments of pain and diseases like rheumatoid arthritis and cancer.
The objective of this chapter is to describe and shed light on some of the more recent
information on the biological effects and medical applications of magnetic fields. A discussion of possible implications of these effects on biological systems is also provided. This
chapter consists of four sections. Each section contains a comprehensive review of a recent
topic of interest. Short summaries of the mechanism of magnetic field action on biological
systems and the biomagnetic phenomena are described in Section 3.2, which includes a
brief review of well-known mechanisms that are discussed before mentioning the interactions of weak SMFs with biological systems including magnetic sensing and sensing using
magnetite as the primary sensor. Section 3.3 reviews and summarizes more recent in vivo
and in vitro experimental results of the effects of magnetic fields including TMS and MRI
fields. Section 3.4 covers special topics including the response of plants to magnetic fields.
In parallel with a comprehensive review on biological effects, the development and medical applications of biomagnetic phenomena are introduced in Section 3.5, and they are
reviewed with emphasis on the applications that are currently under investigation.
3.2 Mechanisms of Biological Effects and
Biomagnetic Phenomena of Magnetic Fields
Table 3.1 shows three types of well-known mechanisms of the biological effects of magnetic fields including SMFs and time-varying magnetic fields (Ueno and Shigemitsu
2007). As shown in Table 3.1, there are two basic mechanisms of SMFs: (1) magnetic