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Preface
nuclear magnetic resonance takes place in biological medium under the influence of a
radiofrequency (RF) field to allow imaging and spectroscopy of tissues inside the human
body. Clearly, a biological effect is a prerequisite to any potential medical application of
electromagnetic fields. However, an unintended or deleterious biological effect of electromagnetic fields and radiation may indicate grounds for health and safety precautions
in the communication, industrial, scientific, and medical use of electromagnetic fields
and radiation. Regardless, to help advance knowledge of the biological effects of such
fields and to exploit their potential medical applications, it is essential to describe the
characteristics of not only the applied electromagnetic fields and radiation but also the
resulting electromagnetic fields and radiation inside the biological system.
A quantitative relationship between applied and induced electromagnetic fields and
radiation would relate them to specific responses of the biological system. It should also
facilitate an understanding of the biological responses. The induced field is the primary
source of energy driving the interaction of electromagnetic energy with the biological
system. Although it may contribute to the formulation of mechanisms of interaction, it
is independent of any mechanism of interaction. Moreover, knowledge of applied and
induced fields would aid in analyzing relationships among various observed biological
effects in different experimental models and subjects. It could also serve as an index
for comparison and extrapolation of experimental results from cell to cell, tissue to tissue, and tissue to animal, and from animal to animal, animal to human, and human to
human exposures.
Experiments designed to study the interaction of electromagnetic fields and radiation with biological systems and the possible effects of such fields on the systems can
be divided into three categories: (1) in vitro biological experiments, (2) in vivo animal
experiments, and (3) laboratory or epidemiological studies on humans. In vitro biological experiments typically involve biological entities constituted by cells contained within
flasks or petri dishes and exposed to well-defined electromagnetic fields and radiation.
These experiments are most suited to study the possible effects of exposure on specific
biological targets or to study postulates and verify proposed interaction mechanisms
aimed toward explaining observed biological responses. Epidemiological studies can
offer the most direct evidence on the health effects of human exposure to electromagnetic fields and radiation. Apart from the difficulties faced in exposure assessment, that
is, the quantification of levels of applied and induced electromagnetic fields and radiation, which is rather difficult if not impossible to obtain with a high degree of accuracy,
the major limitation of epidemiological studies is the prolonged period of time typically
required for observation in most cases and the related confounding factors.
Moreover, the implications of any effect obtained at the cellular level from in vitro
investigations are not always obvious in terms of health effects on the whole organism. Thus, it is often necessary to conduct in vivo experiments, where whole animals,
such as mice and rats, are directly exposed to electromagnetic fields and radiation and
the potential for induction of specific health effects is studied. In vivo experiments are
not only important in assessing possible health effects of electromagnetic fields and the
thresholds for their induction but also useful in allowing extrapolation of animal observations to human subjects, provided knowledge is available to specify the relationship
between applied and induced electromagnetic fields and radiation.
Preface
nuclear magnetic resonance takes place in biological medium under the influence of a
radiofrequency (RF) field to allow imaging and spectroscopy of tissues inside the human
body. Clearly, a biological effect is a prerequisite to any potential medical application of
electromagnetic fields. However, an unintended or deleterious biological effect of electromagnetic fields and radiation may indicate grounds for health and safety precautions
in the communication, industrial, scientific, and medical use of electromagnetic fields
and radiation. Regardless, to help advance knowledge of the biological effects of such
fields and to exploit their potential medical applications, it is essential to describe the
characteristics of not only the applied electromagnetic fields and radiation but also the
resulting electromagnetic fields and radiation inside the biological system.
A quantitative relationship between applied and induced electromagnetic fields and
radiation would relate them to specific responses of the biological system. It should also
facilitate an understanding of the biological responses. The induced field is the primary
source of energy driving the interaction of electromagnetic energy with the biological
system. Although it may contribute to the formulation of mechanisms of interaction, it
is independent of any mechanism of interaction. Moreover, knowledge of applied and
induced fields would aid in analyzing relationships among various observed biological
effects in different experimental models and subjects. It could also serve as an index
for comparison and extrapolation of experimental results from cell to cell, tissue to tissue, and tissue to animal, and from animal to animal, animal to human, and human to
human exposures.
Experiments designed to study the interaction of electromagnetic fields and radiation with biological systems and the possible effects of such fields on the systems can
be divided into three categories: (1) in vitro biological experiments, (2) in vivo animal
experiments, and (3) laboratory or epidemiological studies on humans. In vitro biological experiments typically involve biological entities constituted by cells contained within
flasks or petri dishes and exposed to well-defined electromagnetic fields and radiation.
These experiments are most suited to study the possible effects of exposure on specific
biological targets or to study postulates and verify proposed interaction mechanisms
aimed toward explaining observed biological responses. Epidemiological studies can
offer the most direct evidence on the health effects of human exposure to electromagnetic fields and radiation. Apart from the difficulties faced in exposure assessment, that
is, the quantification of levels of applied and induced electromagnetic fields and radiation, which is rather difficult if not impossible to obtain with a high degree of accuracy,
the major limitation of epidemiological studies is the prolonged period of time typically
required for observation in most cases and the related confounding factors.
Moreover, the implications of any effect obtained at the cellular level from in vitro
investigations are not always obvious in terms of health effects on the whole organism. Thus, it is often necessary to conduct in vivo experiments, where whole animals,
such as mice and rats, are directly exposed to electromagnetic fields and radiation and
the potential for induction of specific health effects is studied. In vivo experiments are
not only important in assessing possible health effects of electromagnetic fields and the
thresholds for their induction but also useful in allowing extrapolation of animal observations to human subjects, provided knowledge is available to specify the relationship
between applied and induced electromagnetic fields and radiation.