randomly oriented because of thermal motion, but when the field is present a preferential alignment
becomes established. If the dipoles were attached to a cell membrane, for example, then the preferential
alignment might correspond to a state of altered membrane permeability. Every EMF produces some
preferential alignment, but one cannot determine, before the fact, how much alignment would be
biologically significant. Historically, the notion has been that something approaching saturation would
be required, but this view is based on inappropriate models of living organisms (low-pressure gasses
and dilute solutions of polar solutes).
In addition to permanent dipoles, which may or may not be present in a material, applied EMFs
can induce a dipole moment as a result of electronic and atomic polarization. Field-generated forces
(Type 3) occur when the field interacts with the induced dipole moment, and they can produce
interesting orientational and translational effects in in vitro systems. One of the best known such
effects, pearl-chain formation (Fig. 9.2), has been observed with many kinds of particles including
blood cells (alive and dead) and plastic microspheres. Present theory suggests that field strengths
needed to produce pearl-chains are of the order of 104-106 v/m, depending on particle size. If this is
true of all Type-3 processes-the latest evidence suggests that it is not - they would be of little biological
interest.
Heat is an ubiquitous consequence of EMFs and it has long been associated with gross,
irreversible changes in tissue - the microwave oven is perhaps the latest and most familiar example. In
theory, any heat input to a biological system (hence any EMF) could alter one or more of its functions.
This idea, however, directly conflicts with the prominent view (at least in the West) that only heat
inputs that are an appreciable fraction of the organism's basal metabolic rate can lead to biological
effects. We shall have more to say concerning the implications of this view in chapter 10.
Since heat is always produced when an organism is exposed to an EMF, one cannot
experimentally determine whether a resulting biological effect could occur in the absence of heat
production. (Conversely, although it is a heavy burden for such a humble process, it is always possible
to assert that any EMF-induced biological effect is due to heat.) Thus it seems pointless to relate heat -a
thermodynamic concept that is independent of the precise details of molecular activity- to observed
biological effects which can, ultimately, be explained in more fundamental terms.
The most fertile ground for understanding the physical basis of EMF-induced biological effects
involves those processes that we have lumped together in Type 5. They are quantum mechanical and
classical processes and include, for example, superconductivity, Hall effect, converse piezoelectric
effect, cooperative dipole interactions, Bose-Einstein condensation, and plasma oscillations. Type-s
processes have sensitivities as low as 10-9 µW/cm2 and 10-9 gauss, and, therefore, are theoretically
capable of serving as the underlying physical mechanism for any known EMF-induced biological
effect. Some direct evidence for Type-5 processes has already been described in previous chapters;
other developments in this area that also deserve mention are the initiative of Pilla, Frolich, Zon, and
Cope.
Pilla's model originated with his and Bassett's work regarding the effects of localized pulsed
magnetic fields on bone growth in dogs (2) and humans (3). Pilla reasoned that there must exist
generalized mechanisms by which diverse electrical stimuli could alter cell function. He proposed a
theory of electrochemical information transfer in which field-induced changes in the ionic
microenvironment were responsible for alterations in cell permeability (4, 6). The theory allows for
three non-faradaic electrochemical processes: the binding of specific ions; the passage of ions through
the membrane; and changes in the membrane double-layer. Because the kinematics of each process
differed -measured in impedance studies of the cell's cytoplasmic membrane- it would be possible, in
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