There is no uniform explanation for the resultant mechanism of the effects of electromagnetic waves. The reason is that there may be a whole series of independent primary mechanisms, several of which may be acting simultaneously for a given set of parameters. The complexity of the resultant effects of electromagnetic waves on the organism is best shown by Table 4.
With changes in the field parameters, the character of the individual component processes may change substantially (166, 202, 205, 283). We have already mentioned that there are two kinds of effects, thermal and nonthermal. But there is no sharp dividing line between them. This fact stems from the nonuniformity of views on the meaning of the concept of nonthermal effect (frequently labelled as specific). The majority of authors understand this concept to mean the effect of electromagnetic waves of a field intensity so low that they do not produce a significant increase in the temperature of an irradiated object. This is of course a highly unobjective definition and does not provide any explanation of the basis of the phenomenon. The thermal effect is produced by an increase in the temperature of the system (or part of it) with increased molecular motion under the influence of impact and friction.
It is much more accurate to consider those effects as nonthermal that stem from primary nonthermal (stationary) mechanisms of the effects of electomagnetic waves on an irradiated system, without regard to the field intensity. Because the electrically charged particles (whether ions, molecular dipoles or colloidal particles) are always in motion in an alternating field, and because ionic and colloidal solutions including molecular dipoles are necessary components of a biological system (primarily water, but also organic compounds, such as amino acids), it is never possible in such systems to separate a thermal effect from a nonthermal one.
Under suitable conditions (conductivity, dielectric constant, frequency, intensity and nature of the field), and with specific features of the organism, the nonthermal effect may definitely predominate over the thermal one and thus be the biologically effective factor. At the present time, it is precisely the mechanisms of nonthermal effects of an electromagnetic field which are the center of attention. When rf energy strikes the surface of a body, some is reflected and some penetrates to be absorbed. The reflection depends on the electrical characteristics of the tissue on which the rf (page 49) field is incident. As radiation passes into tissue, its wavelength changes because there is a change in its velocity of propagation, which depends on the dielectric constant and the conductivity of the medium. A dipole located in the electrical field is aligned. If the field is alternating, the dipole begins to oscillate with the frequency of the field. The greater the dipole moment of the dipole, the greater the energy required for its oscillation. The result is an increase in temperature. The same results from an increase in frequency, since the oscillation rate of the molecular dipoles increases and the losses produced by friction likewise increase. (...)
However, practical experiments with animals have shown that because of thermoregulation the frequency dependence is not so pronounced and shows up distinctly only at hight field intensities (15). It is thus necessary to consider another means of rf penetration into the organism. This second pathway is called "electromagnetic induction." An rf potential is induced in a conductor located in an electromagnetic field.This potential may then be carried (after some loss) by the conductor to locations where there is no direct electromagnetic field. The losses produced in a unit length of the circuit depend primarily on the resistance of the conductor, the immediate environment around the conductor, and the frequency of the rf current flowing through the conductor. That is true for a conductor of the first order.
The electromagnetic field generates ionic currents in the organism. Lazarev has proposed the hypothesis (136) that the influence of the field increases the ion concentration in the vicinity of the cell membranes, which could result in largely reversible accumulation of protein molecules (some causing them so to speak to come out of solution). Moreover, he notes that a sufficiently large change in the ion concentration causes a change in the biological characteristics of the cells. The action of the electrical field on a charged particle thus leads to its forced motion. That means that the arrangement of the system is changed. If the field vanishes, the system requires a certain time to return to its original state. This interval is called the relaxation time, which depends on the dimensions and (page 50) charge of the particles, as well as the characteristics of the medium and the temperature. (...) If the period of the field changes in accordance with relaxation of the particles, transfer (and hence energy absorption) is at a maximum.(...)
In water molecules which have a relaxation period on the order of 10 to the power of -11 sec at room temperature, the absorption of energy reaches its maximum in the frequency range from 10 to the power of 9 to 10 to the power of 11 Hz, corresponding to wavelengths of 30 cm to 3 mm (166). Such absorption has been observed experimentally (220). In the case of proteins, the relaxation time in an aqueous solution is in the order of 10 to the power of -7 sec, which points to resonant absorption of energy in the range of frequencies of the order of 10 to the power of 6 Hz. That agrees with the experimentally determined basic frequencies for sensitive effects of an rf field on the properties of gamma globulin, described by Bach et al. (9), although the authors do not mention this circumstance. It should thus be possible to explain the selective frequency changes observed in the elctrophoretic and antigenic properties of gamma globulin under the influence of the rf field as the disturbance of the structure by the action of the relaxation absorption of energy, which in turn can lead to a shift in the reactivity of some functional groups in the molecule. An explanation of this sort also agrees with the temperature dependence of the effective frequency (...), as observed by the above authors.
The spatial resonance of large molecules in the microwave region is closely related to the relaxation resonance. In evaluating a possibility of this kind (disputed by many authors), it is necessary to appreciate the relationship between the wavelength and the frequency of the electromagnetic waves in the medium under consideration. (...) The wavelength depends largely on the dielectric constant and the conductivity of the medium, but indirectly. Besides, it has been determined that some systems, among which it is necessary to include ionic conduction, have an enormously high dielectric constant, running up (page 51) to many thousands (1). We can therefore assume that in such a medium, microwaves may have a wavelength comparable with the dimensions of macromolecules. We can thus even accept the possibility of a direct spatial resonance of the molecules, which theoretically can lead to mechanical deformation or damage (166).
Direct damage to molecules by resonance phenomena nevertheless seems to be quite improbable, since a very intense field would be required. It is possible, however, to excite molecules by the absorption of a quantum of energy (195). That increases the potential energy of molecules. A return to the unexcited state can take place either by transfer of the energy to another, unexcited molecule, which leads to an increase in its motion (and therefore to a thermal effect); by radiation of the energy; or finally by the structuring of certain parts of the molecule. The last form of energy loss leads to a change in at least some of the characteristics of the molecule.
This form of absorption of electromagnetic waves in the nonionizing portion of the spectrum is known, as previously mentioned, for example in ammonia where there are 12 frequencies in the range from 2 to 4 GHz (ie wavelengths from 15 to 7,5 cm) at which molecules can be excited. Radiation of energy leads to a reversal of the tetrahedral structure of the NH3 molecule. One more fact remains to be considered. Excited molecules very readily participate in a number of chemical reactions such as oxidation, fission, etc. This phenomenon occurs in the range of wavelengths on the order of 0,1 mm.
Mention has already been made of the orientation of dipolar molecules in an electrical field resulting from the attraction between unlike electrical charges and repulsion between like charges. In the case of large dipolar molecules (for example, proteins), as the frequency rises (above the relaxation frequency), their oscillation in resonance with the field becomes increasingly more difficult; above a certain frequency, they come to rest in some intermediate position, depending primarily on the shape of the molecule and the distribution of the charge. However, because the charge distribution of the dipole cannot be considered as fixed at a certain exact site, this "charge cloud" still moves about the molecule at the oscillation frequency.That can also lead to changes in the reactivity at the corresponding centers of the molecule.
The group of "resonance theories" also includes the interesting idea of regarding the biological effect of electromagnetic waves as a nonthermal effect resulting from the cyclotron resonance of several notable varieties of molecules in the organism (257). It is actually a combination of the elctromagnetic field with the earth´s magnetic field. This idea is still purely speculative, without any sort of experimental foundation.
Charged particles (ionic or colloidal), under certain conditions, form around themselves an electrical dipole layer, composed of oppositely charged ions. The total external effect is (page 52) that of an electrically neutral entity (Fig. 20a). The electrical field then contains a nucleus (ie the original charged particle) and dipole layers, each drawn with a certain force in opposite directions, giving rise to an induced dipole which is a priori oriented along the lines of force of the electrical field (Fig. 20b). It is generally known that the greater the field intensity, the more pronounced is the separation between the two charges in the dipole. In the event of a random encounter between dipoles oriented in this manner, there is an attraction between their oppositely charged ends that leads to linking of the particles (Fig. 20c). This phenomenon, which has been known in colloids for a long time (131, 177), has recently received considerable renewed attention (257, 268) precisely because of (page 53) the effects of rf fields on the organism. It would appear that it might be possible to explain, at least partially, the recently discovered genetic changes evoked by high-frequency electromagnetic fields (94) in this way.
Fig. 20
The chain formation of colloidal (and more coarsely dispersed) particles might, unlike all previously suggested mechanisms, also explain certain effects of biological agents at lower frequencies. The described effect has been experimentally verified in the frequency band from 0 to 100 MHz (257). A careful study of this phenomenon forcibly suggests the idea that possibly not only colloidal particles form chains, but molecules as well. That could lead to the creation of a sort of pseudomacromolecules, whose presence would produce a change in the response of the organism. Thus, for example, if there is chain formation by ions or molecules, which are normally transported through semipermeable membranes, the process would be retarded or even prevented as the length of the chain increases. Externally, the phenomenon would manifest itself as a change in the permeability of the membrane, as one can actually conclude from some experimental reports (280).
But the permeability of a membrane can also change under the influence of an rf field on the basis of a change in polarization, which can also be produced by purely electrical phenomena, as are described later on in this chapter. All theories proposed thus far have certain shortcomings. They cannot explain, among other things, alternating effects, as for instance the change in nerve-cell sensitivity, which proceeds sometimes in the positive, sometimes in the negative direction. Similar phenomena can also be explained by a change in the electrical characteristics of nerve cells (152, 153). Many parts of the organism can be assigned to the category of semiconductors on the basis of their electrical characteristics (66, 202), whose resistance may depend on the direction of the current flow. From this point of view, the factor of primary importance is their asymmetrically nonlinear volt-ampere characteristic, which represents current as a function of voltage (Fig. 21).
(Page 54) In some cases, for a certain part of this characteristic, an increase in current does not go with an increase in voltage, but rather a decrease. Such elements are said to have a region of negative resistance (segment A in Fig. 22).
A common feature of all systems with an asymmetrically nonlinear characteristic is that when an alternating signal is applied to them, it is asymmetrically distorted and a dc voltage results. There is detection of an ac signal. All semiconductors have this property. It has recently been found that a great many organic compounds have semiconductor properties (109). Many of them occur in the organism (for example, hemoglobin, desoxyribonucleid acid, etc.). Finally, it has been established that nerve fibers and many other cells behave like nonlinear elements (32, 84, 85), sometimes even containing a region of negatice resistance (146). At a certain value of the action potential (the so-called working point) and a definite amplitude of an alternating signal, they can cause its asymmetric distortion.
The biologically important semiconducting systems can thus be divided into three groups:
(a) direct, ie with electronic conductivity;
(b) indirect, ie with ionic conductivity; and
(c) mixed.
Among the direct semiconductors we count those systems in which the nonlinear element is actually the molecule or group of identical molecules (a polymer). In such a semiconductor, the nonlinearity is of a conductive nature, and such a semiconductor (either by itself or doped with majority charge carriers) is an asymmetrically nonlinear element precisely because its resistance in a certain region of the applied potential depends on the direction of the current flow. This group includes all organic semiconductors whose semiconductor characteristics are produced (page 55) by molecular arrangement, especially of the pi electrons. The conductivity in such materials is of the electronic variety.
However, there is still another group of nonlinear elements, in which ionic conductivity prevails.
If such a system contains a polarizable element, then the passage of a dc current (that is organized movement of the ions) leads to a polarization potential, which affects the volt-ampere characteristic of the system. In the case of a cell, the membrane acts as this kind of polarized element. If it is not itself a charge carrier, the solution-membrane-solution system (assuming similar composition of both solutions and structural symmetry of the membrane) will have the highest symmetrically nonlinear volt-ampere characteristic. If the system also contains a source of potential (as for example, the structural polarization of the membrane or unequal concentrations of some ion on the two sides of the membrane), the working point of the system shifts in such a way that the symmetry of the volt-ampere characteristic is disturbed. That produces an asymmetrically nonlinear circuit with rectification properties and a characteristic similar to that of semiconductors.
As we have already seen, asymmetrically nonlinear circuits distort an alternating signal in such a way as to give rise to a dc component; ie rectification takes place. In direct semiconductors the rectification effect is produced by a different conductivity according to the direction of the current, whereas in indirect semiconductors, the rectification effect is produced by the polarization potential of the system; here the distortion can be thought of as adding to (or substracting from) the potential of the system, the instantaneous voltage of the alternating signal (according to the polarity of the half-wave). The lack of symmetry results in a direct current with a positive or negative sign, which changes the polarization potential of the membrane. In practise both of these factors may occur in combination so that the group of mixed semiconductors results. We know that in a physiological state, living cells have an electrical charge. Under its influence, the arrangement of ions or amphoteretic compounds such as proteins is not accidental, neither within a cell nor in the immediate external environment of a cell membrane.
If the potential of a cell changes, its microstructure thus changes as well; the cell is no longer in the physiological state which is likely to manifest itself in its characteristics; and if it is a controlling cell (nerve cell), the activity of other cells in the organism may be affected as well. The greater the deviation in the characteristics of the cell from the normal, the more pronounced the shift from equilibrium, and the greater the influence on the entire state and behavior of the organism. However, the effect of the absolute value of the change in potential on the behavior of the cell is largely determined by the position of the working point. This is most dramatically evident in the case of controlling (nerve) cells.
More simply, we can say that the organism as a whole, and thus (page 56) every cell, has the ability to maintain its equilibrium to a certain degree, subject to interference both from without and within. However, this ability is limited partly by the time factor, ie the organism can defend itself for only a certain period of time; and partly by the magnitude of the deviation from equilibrium. The time factor is inversely proportional to quantity, ie the greater the disturbance of equilibrium, the shorter the period of time during which the organism can cope with this abnormal state. It should also be mentioned that the mutual relationships are not linear.
As even relatively small functional units of the organism are composed of a multitude of cells, for which we can assume qualitatively different electrical characteristics, the resultant volt-ampere characteristic of such a unit can have a shape which produces a different change in potential (even as to sign) according to the magnitude of the ac input signal. A more detailed discussion of this matter would exceed the scope of this book, and the interested reader is referred to the literature (153).
On the basis of all the concepts mentioned here, the effect of high-frequency fields on the organism can thus take the form of a change in the arrangement of a number of molecules both inside and outside the cell, and consequently the passage of molecules through the cell membranes may be affected. There is no splitting of molecules and consequent production of new substances foreign to the organism, as confirmed by experimental data.
Also in accord with these findings is the known reversibility of signs of damage (obviously, only to a certain degree, as long as the entire organism is not destroyed, or anyhow a part of it). Because the circulatory and nervous system are the most conductive parts of the organism, the rf current (produced by induction and conduction) is maximum along these pathways. It is also necessary to asume the maximum possibility of changes in tissues whose cells undergo maximum asymmetric distortion and are sensitive to deviations from the normal state. It is likely that this is particularly true of the cells in the nervous system. The mechanism described earlier can change the characteristics and thus the behavior of a cell and if it is a control cell these changes are transferred to the organs being controlled. Thus far, there have been no reports whose results could be interpreted as contradicting the above hypotheses. On the contrary, many papers present data that support these assumptions both directly and indirectly.
Thus Rejzin (142), for example, found that an rf field affects a neuromuscular preparation even outside the irradiated area. He ascribes it to the so-called "diffusions of the field" by the tissue, which is nothing more than conduction. Electromagnetic self-induction along conductive pathways in the organism has recently been put to use for measuring blood flow (271). Both induction and conduction can be demonstrated by a simple experiment, in which the head of a rat is placed in the field of an rf generator. The field is just strong enough (at f = 1 MHz, for example) to fire (page 57) a glow lamp. The lengthwise axis of the body of the experimental animal is aligned with the propagation direction of the field, so that the tail is in a field so weak that it cannot fire the glow lamp. Nevertheless, the effect of conduction suffices to fire the lamp at the tip of the tail.
According to Tarusov, for example, the semiconductor nature of a cell suggested by theory can be ascribed to it on the basis of its conductivity in the resting state (254). This is also in agreement with the finding that the thermal coefficient of resistance of tissue is always negative, which is one of the characteristic properties of semiconductors. Under the effect of an rf field the cathodic excitation of a neuromuscular preparation is increased and the anodic excitation is decreased. This result is indicative of a change in the charge of the cell in an rf field in accordance with the concepts described above. The change in the charge of such a field has even been successfully measured. In accordance with the experiments cited above, an rf field produces the electrical negativity of a nerve (142). These results have been evidently forgotten, for suggestions are only now being made that an organism or its part could function as a detector of electromagnetic waves (202, 279). Finally, measurements have provided the actual volt-ampere characteristics of living cells (178), which have the appearance of the characteristics of classical semiconductors: they are asymmetrically nonlinear, often with a region of negative resistance.
Mention should also be made in conclusion of some consequences that stem from the theories proposed regarding the mechanism of the biological effect of the rf field. We have said that a change in the charge of a nerve cell is of the highest consequence for the entire organism, since a change in its physiological state produces a change in its controlling functions as well. The effect of the rf field on the organism must thus depend on the state of the central nervous system, as has been pointed out long ago (142, 208). The threshold level of the rf field differs for stimulation and for inhibition of the CNS. Experiments in which rats were given a psychotone perfectly support this point, and the field intensity required to kill the experimental animals was then significantly less.
On the other hand, it was found that the rf field intensity required to produce the same damage to the organism is much greater when the animal is under the influence of a narcotic. The effect of such substances, wheter stimulatory or inhibitory on the CNS, may be thought of as a shift in the working point on the cell characteristic or as a change in the ability to transmit control signals in the organism. In much the same way one might assume that all other factors affecting the parameters of the compensatory system of the cell can not only weaken or intensify the effect of electromagnetic waves, but may even directly influence the functional capacity of the cell. Such a combination factor may take the form either of the effect of (page 58) certain chemical substances or of physical factors or else of changes produced by regressive structures in the organism due to influences of a psychic nature.
At this point, a comparison is in order between the carcinogenic effect of certain chemical substances and their structure. All of these substances have pi electrons in their molecules, closely related to the semiconductor properties of the molecule (54). The question then arises as to whether it is precisely the semiconductor nature of these substances that play an important role in their carcinogenic effect, and whether this effect is activated by or even conditioned by the presence of an electromagnetic field.
Nonlinear elements may also cause detection of a modulated signal, so that low-frequency component appears. Thus, we can explain the observation of Frey, who mentions the ability of persons (including the deaf!) to "hear" a pulse-modulated transmitter.
The most interesting (and from the biological standpoint, most important) conclusions can be drawn in the case of cells whose volt-ampere characteristic has a region of negative resistance. For a favorable position of the working point (physiological state) near the peak of the characteristic curve (cf. Fig. 22), the application of a stimulus of appropriate amplitude and direction produces a sudden shift in the working point, so that even when this stimulus is removed the cell cannot return to its initial state, but remains "stimulated" to a degree. In other words, we can determine from such a characteristic curve that if we gradually increase the amplitude of the stimulus from zero we shall find a certain threshold of the effect. If we reduce the stimulus from a large amplitude, it will cease to be effective at another, usually lower, threshold value.
Presman has published a hypothesis (203) according to which certain processes in living organisms at all levels of existence (from the molecular to the systemic) are initiated by internal and external electromagnetic fields. Electrical fields are doubtless an important component in the control of physiological processes in organisms, as Bassett (13) has recently demonstrated for bone growth. Naturally, these phenomena are not so simple as may have been indicated. In addition, one must keep in mind that these ideas are of a predominantly speculative nature. That should not detract in any way from their significance, however, since they are very useful for further study. A more detailed discussion of these interesting problems would go beyond the scope of this book.