1. Introduction

  This review examines primarily direct experimental studies of the effects of low-intensity HF EMF on biological subjects, including humans. Unlike epidemiological observations, direct experiments allow parameters of the acting EMF to be established more accurately, the condition of the subject to be monitored before and during exposure and for a certain period afterwards, and scientific hypotheses on the mechanisms of the effects to be verified. Clinical experiments done with the intention of improving the condition of the patients are the only legitimate experiments on people, and for this reason, published articles more often deal with the positive effects of HF EMF. One should consider, however, that EMFs with therapeutic effects comprise only a minuscule portion of all acting fields, and that there is a large probability of harmful effects from incidental generalized exposure, as confirmed in experiments on animals.

  Currently we still do not know the specific receptor in humans for perception of extremely high frequency electromagnetic radiation (EHF EMR). Nevertheless, the presence of sensory reactions has been established during local peripheral exposure of humans to EHF EMR [Andreev, Beliy and Sit'ko, 1985]. At this moment in time, the following can be considered established:
  1) Humans are capable of differentiating reliably between exposure to EHF EMR and a sham exposure;
  2) Electromagnetic sensitivity in humans is determined by the biotropic characteristics of the EHF EMR: frequency, power, time and place of exposure; The most typical reaction in humans is of a resonant character and is found during changes in frequency of EHF EMR [Andreev, Beliy and Sit'ko, 1985]. Use of extremely low power EHF EMR of 10-19 W/Hz in millimeter wave resonance therapy for treating people involves selection of an individual frequency which has the maximum therapeutic effect [Andreev, Beliy and Sit'ko, 1985; and Sit'ko, Skripnik and Yanenko, 1999].
  3) The so-called points of Chinese acupuncture play a particular role in this reception, and are notable for having been used for thousands of years in treating practically all systems of the human body.

2. Natural Electromagnetic Background

  Natural sources of background EMF consist mainly of objects of cosmic origin: radio emissions from the sun and planets, relict radiation, and noise from atmospheric events [Pisanko, Pyasetskiy].

  Background microwave radiation--relict radiation--is cosmic radiation with a spectrum characteristic of an absolutely black body at a temperature of 2.7 K; it determines the intensity of the background radiation of the universe in the shortwave radio band (in cm, mm and sub-mm waves). It is characterized by the highest degree of isotropy. The main contribution to the energy density is made by radiation with wavelengths, from 6 to 0.6 mm. In this range, the density of energy is 0.25 eV/cm3. Radio wave emissions from an active sun, during eruptions and flares, are observed at frequencies of 1.2, 3, 9.5, 35 and 70 GHz, raising the total value by 30%. The intensity of natural background EMR is at a maximum in the morning hours and at a minimum in the evening. A power flux density (PFD) of 3 x 10-7 mW/cm2 in the range of 100-300 GHz was recorded on the Earth's surface when the atmospheric concentration of water vapor was 2.7g/m3. EMR with wavelengths less than 3 cm is absorbed by resonance in the atmosphere:
  1) in precipitation (rain, fog, snow);
  2) by molecular absorption in water vapor and oxygen.
  Researchers [Yesepkina, Korol'kov and Pariyskiy] underscore the resonant absorption of water vapor at frequencies of 26 and 188 GHz. Atmospheric oxygen has absorption maxima at frequencies of 60 and 118.7 GHz. In addition, this band contains windows of transparency at wavelengths of 8.6 mm, 3.2 mm, 2.1 mm and 1.2 mm. Radiation in the mm band penetrating from space through the windows of transparency can be considered to be the primary radiation. On Earth, the heating of various physical bodies also gives rise to radiation in the mm band, which can be considered secondary. Such sources of EHF EMR are water, sand, bricks, plaster, granite, marble, wood, etc. [Sit'ko, Skripnik and Yanenko, 1999]. Since living organisms have evolved under conditions of low natural background EHF EMR, they lack a ready-made mechanism of evolutionary adaptation to heightened levels of radiation resulting from technogenic factors.

3. History of Research in the USSR

  In the 1950s in the USSR, there was development in a new scientific direction--mastery of the millimeter (EHF) portion of the spectrum of coherent electromagnetic oscillations [O.V. Betskiy, 1997]. This work was conducted in the organizations of the Ministry of Electronic Industry, the Academies of Science of the USSR and Ukrainian SSR, and in institutions of higher education. The Scientific Council on the Problem of "Generation, Amplification and Transformation in the mm Wave Band" was founded under the direction of academician N.D. Devyatkov.

  In the 1960s, all necessary instrumentation was created for the millimeter and sub-millimeter wavelength bands.

  In 1965, N.D. Devyatkov and his coworkers set forth an original idea that all living organisms on Earth are not adapted to this type of radiation, because under natural conditions it is practically absent due to strong absorption by the Earth's atmosphere (mainly by water vapor). A proposition was also put forward about the possibility that low-intensity electromagnetic waves have specific effects on biological structures and organisms. Research was begun on the interaction of mm-waves with biological objects.

  The research showed that generation of coherent waves by cells is a systemic process in which cell membranes, protein molecules and transport mechanisms are involved.

  There are data on excitation in cells of coherent oscillations s in a wide range of frequencies, but a particularly large part of the data are concerned with frequencies of 30 to 300 GHz, which corresponds to the mm wavelength range.

  Three possible channels were pointed out for conduction of operative signals within an organism over considerable distances: the nervous system, the humoral system and the system of acupuncture points. In addition, a number of peculiarities of these channels were discovered:
-Conduction of signals through the nervous system is accomplished in the myelin sheaths of the axons.
-Conduction of signals through the humoral system is connected with the movement of generating cells through the blood and lymphatic systems. In this way, within the organism the transmission of signals is accomplished, apparently, not by conduction of radiation, not by movement of charges, but by the displacement of generator-cells, the oscillations of which reflect the information being carried. -Water molecules strongly absorb EHF radiation, and play a big role in various biophysical effects involving mm waves.

  Many biological processes, including processes in biomembranes, are sensitive to environmental mixing (as the result of local heating and convection). It was found experimentally that low-intensity EHF radiation can cause acceleration of active transport of sodium ions (at an energy flux density (EFD) of 1 mW/cm2), a change the permeability of erythrocyte membranes to potassium ions (EFD of 1-5 mW/cm2), acceleration of peroxide oxidation of unsaturated fatty acids in liposomes (EFD of 1 mW/cm2), increase of ion conductivity of bilayered lipid membranes (EFD of 1-10 mW/cm2), etc.

  One of the more interesting experimental facts discovered by A.Z. Smelyanskaya, L.A. Sevastyanovaya, and others in irradiating various microorganisms with mm waves in 1968-71, was the dependency of biological effects on frequency.

  Under the influence of EHF EMR (wavelength of 5.6 mm, EFD of 0.5 mW/cm2), the nature of the change in potential difference of the plasma membrane of a growing cell was identical to that which arises during exposure to photosynthetic active radiation [Petrov, Betskiy]. It was deduced that mm wavelengths have the ability to stimulate the synthesis of ATP in the cell.

  [Tambiev and Kirikova] studied the effect of low-intensity EHF EMR on the growth of biomass of Spirulina, a blue-green alga. Over the course of multi-year experiments it was shown that along with growth in biomass of the alga (as much as 300%), there was significantly increased synthesis of biologically active substances (vitamins, carbohydrates, etc.) which are excreted into the environment.

  From the beginning of the 1960s in the USSR, a wide range of research was conducted on the health of people who had contact with EMF on the job. The results of clinical research showed that prolonged contact with EMF in the SHF band can lead to development of diseases, the clinical profile of which is determined above all by changes in the functional condition of the nervous and cardiovascular systems. It was proposed to define it as a specific illness--radiowave sickness. This illness can have three syndromes according to the acuteness of the disease:
    -asthenic syndrome;
    -astheno-vegetative syndrome;
    -hypothalamic syndrome.

4. Physical Approach to Resonant Absorbtion of Low-intensity HF EMR

  The basis of the chosen approach was a concept about the dissipation of energy of EHF radio waves in a non-homogenous object upon their resonant penetration into the object [Petrosyan, Zhiteneva, Gulyaev]. During this process, energy in the form of monochromatic wmm waves should be transformed into thermal energy in the molecular environment of the object according to Planck's law of radiation. It has also been thought that this additional noise energy may be taken as a change in intensity of the radio wave noise produced by the object itself, or the radioecho of the object, in a wide range of frequencies in the SHF region, including the decimeter. Because the depth of penetration of decimeter waves into aqueous media is greater by several orders of magnitude than the skin layer for the mm range, the detection of a radioecho from the object in the dm range would signify penetration of EHF EMR into the object at resonant frequencies.

  To avoid possible experimental errors, special measures were adopted. Detection of the radioecho of the object exposed to EHF radiation was done radiometrically with the aid of a highly sensitive SHF radiometer working in a bandwidth of 50 MHz with a fluctuational sensitivity of 0.1 K(<10-20 W) at a time constant of one second. Another SHF radiometer was used as a control, tuned to a frequency of 0.4 GHz with analogous parameters. Use of an antenna allowed radioecho signals to be taken from any point on the object. The source of monochromatic EHF EMR was a set of tunable generators, which continuously covered the range of 4-120 GHz. For controlling the quality of the radiation from the generators, a standard generator was also used.

  Research was done on the human body, on animals, on water under various conditions and on a number of other objects in liquid or aqueous dispersed conditions.

  The basic result of this experimental research was discovery of "physical" EHF resonance. Physical resonance explains maximum radioecho of an object in a narrow range of EHF EMR frequencies. It is well known that a non-linear medium responding to an external periodic influence may be found in one of three dynamic conditions--chaotic, oscillating or stationary--depending on the intensity of the influence. All of these three conditions were observed clearly when the power of the EHF radiation was changed. A stationary state was achieved by cardinal reduction of the EHF power from 10 mW/cm2 to a level of less than 10 _W/cm2. Only under these conditions were echoes received adequate, in relation to the intensity of the EHF radiation, to allow physical resonances to be detected. In this sense, EHF resonance is a threshold effect at a low enough level of power compared to the fundamental parameter--the intensity of the medium's own molecular vibrations, with no effect found at levels higher than this.

  From the experimental results they obtained, the authors [Petrosyan, Zhiteneva, Gulyaev] drew the following conclusions:
    -There exist radiophysical resonances of size interaction of EHF radiowaves with objects;     -Spontaneous shifts of resonant frequency and low-frequency auto-oscillations are observed;     -EHF resonances of biological objects (humans) coincide with those of physical objects (water);     -Various liquids and aqueous dispersed media have individual characteristic EHF spectra.

  It can be stated that penetration of EHF radiowaves into a medium (object) occurs at the resonant frequencies of the molecular oscillators of the medium, and the resonant interaction must be interpreted as resonant transparency of the medium to EHF radiowaves, not as the absence of absorption by that medium.



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