Abstract: Experimental and
theoretical investigations of electrical properties of biological system have
helped to develop understanding of the properties of various biological
entities and to elucidate mechanisms of interaction of EM fields. There exist
two interactions views of the electrical field with matter: macroscopic and
microscopic. Generally said, interaction mechanisms could be explained by
relaxation phenomena, field-induced forces and no equilibrium phenomena. The aim
of this paper is to give the review of this phenomenon.
I.
Introduction
Many of scientists insist for the industry to accept their findings, allow to be made public and then let consumers decide how to react, like in case of tobacco. Particularly digital GSM (Global System Mobile) phones are biologically active, especially those with short, stub (helical) antennae. It is known that absorption depends on the shape of someone’s head and the way the phone is held, weather or not this happens in a closed area, on design of phone, type of antenna and how far is the nearest base-station mast. This could be investigated by using theoretical simulation or by measuring electromagnetic field in an artificial head. But, to explore if the influence of mobile telephone is really hazard for the human health, it is necessary, at first, to elucidate interaction mechanisms of electromagnetic (EM) fields with biological systems.
II. Mechanism of Acting
Experimental and theoretical investigations of passive electrical properties of biological systems have complemented each other and have helped to develop understanding of the structure and of properties of various biological entities and to elucidate mechanisms of interaction of EM fields. They result in a significant amount of data and reliable qualitative models. However, many areas deserve further investigations.
It is necessary to describe two interaction views of the electric field with matter: macroscopic and microscopic. The macroscopic view of interaction is described in terms of complex permitivity that represents a combined macroscopic effect of various molecular phenomena causing electrical polarization. Similarly, interaction of materials with the magnetic field is described on the macroscopic level by the
Permeability. However, most of biological substances are nonmagnetic or very weakly diamagnetic and their permeability can be assumed equal to that of vacuum. Though some bacteria, insects and some tissues exhibit weak magnetic properties. On microscopic level we take care about behavior of atoms and molecules, those respond to an external electric field because they contain charged carriers that are permanently displaced or can be displaced by the field. Matter, in general, is characterized by four types of polarizability: electronic, atomic, orientation and space charge polarization [1] . These three mechanisms of polarization result from charges that are locally bound in atoms, molecules or structure of solids and liquids. In addition, free-charge carriers (ions) that can migrate in the dielectric usually exist. When such carriers are impeded in their motion, either they become trapped in the material or on interfaces or because they cannot be freely discharged or replaced at the electrodes, space charges and a macroscopic field distortion result. This no uniform space charge distribution in the dielectric is responsible for a space charge polarization. Any of the preceding outlined polarization phenomena result in a relaxation-type behavior and in corresponding changes in the permittivity. For biological materials two polarization mechanisms are of particular importance: the space charge polarization from existence of membranes and ions and dipolar polarization, [1].
Electrical equivalent circuits, mathematical formulas and special graphs frequently represent the electrical properties of biological materials. The mixture theories provide a useful tool for analyzing various component contributions to the dielectric polarization.
Generally said, interaction mechanisms could be explained by relaxation phenomena, field-induced forces and no equilibrium phenomena. Biological tissues exhibit three strong relaxation phenomena: a-, b- and ¡-dispersion; and one weak: d-dispersion. Intercellular structures (tubular apparatus in muscle cells, relaxation behavior of membranes and relaxation of counter ions about the charged cellular structure) may contribute to this dispersion. The b-dispersion results mostly from a no homogenous structure, the resulting interfacial polarization. Smaller contributions result from relaxation of proteins. The ¡- dispersion results from free water relaxation, and d-dispersion results from relaxation of bound water, amino acid and charged side groups of proteins, [6].
All relaxation phenomena lead to conversion of EM energy of the interaction field into thermal energy. The thermal energy is then responsible for various biological responses. The amount of energy dissipated at any location of biological body depends on the intensity of the electric field at that location and the tissue conductivity. Biological responses to electromagnetic ally induced thermal stimuli can be significantly different from response to other thermal stimuli. Exposure to EM fields results in a highly no uniform energy deposition within biological bodies. Furthermore, the rate of the energy deposition can be very high, resulting in rapid temperature increases, particularly in the case of pulse-modulated fields. However, some effects have been showmen to be directly related to other interactions, for example, field-induced forces (for high-intensity electric fields) and no equilibrium phenomena (for weak EM fields), [1].
Because of fact that tissue contains a lot of water, in studies of aqueous solutions, knowledge of the electrical properties of water is essential. One thoroughly investigated macromolecule is hemoglobin [1] that exhibits distributed-relaxation time dispersion owing to the polar nature of the molecule at about 2 MHz. But peptides and amino acids, being much smaller than proteins, exhibit relaxation at higher frequencies about 3 GHz. Investigations of blood, bacteria and cellular organelles contributed to understanding of the role of cell membranes in the polarization processes. The essential electrical parameters of the membranes are capacitance and conductance per unit area. The membranes separate regions of different dielectric properties, so that charged interfaces are formed. This is called b-dispersion and typically occurs at a few tens of kilohertz to few hundred of megahertz [3].
III.Tissues Under RF/MW Acting
The electrical properties of tissues in situ, freshly excised and some time after death are expected to be different. The most differences result from breakdown of cellular structure and cell membrane function, [6]. These occurrences result in the redistribution of intracellular and extra cellular ions. Additionally, tissue excision or death can result in loss of blood and water. The greatest differences between in vivo and in vitro properties are at low frequencies in the range of a-dispersion due to change in metabolic activity and ionic milieu of the cells. The changes in the electrical properties in the b-dispersion region are slower, since the rate of change depends on the rate of disintegration of cell membranes, [6]. At high frequencies (MW), the differences between the in vivo and in vitro properties result mostly from blood and water content variations. The general behavior of the electrical properties as a function of frequency is the same in various tissues for different species. The differences in the electrical properties are rather small, not more than 15 %, and in this frequency range can be attributed to different water content, Fig. 1., [1].
Fig.1. Dielectric constant and conductivity of skeletal
Muscle tissue (cat, rat, dog) [1]
By the radiation, the exterior signals are transducer into the cell interior. The cell division is regulated by processes, which involve ions. These features have been shown to alter their behaviour in the presence of imposed external EM fields. Documented changes include alternation of the permeability of
The cell membrane, alternation of the signal transudations processes, which regulate cell behavior and involve many electro-chemical processes. One study has indicated that microwaves can alter DNA synthesis, enzyme activity, ion transport, cell proliferation and the cell cycle, [4]. Now even, scientists say exposure to the phones low-level radiation causes red blood cells to leak hemoglobin. Even at levels lower than those emitted by mobile phones, the cell leaked hemoglobin. The accumulation of hemoglobin in the body could result in heart diseases or kidney stones, [5]. Scientists at Sweden Lund University (1995.) found that two minutes of exposure to emissions from mobile phones can disable a safety barrier in the blood causing proteins and toxins to leak into the brain. This can cause the chances of developing diseases such as Alzheimer’s, multiple sclerosis and Parkinson’s disease. Symptoms reported by mobile phone users include fatigue, dizzy spell, memory loss and headaches in association with the use of cellular phones. There are several lines of evidence to support these conclusions. As first, headaches as a consequence of exposure to low intensity microwaves were already reported in literature. As second, the blood-barrier appears to be involved in headaches, and low intensity microwave energy exposure affects the barrier. Third, the dopamine system of the brain appear to be involved in headaches, and low intensity
Electromagnetic energy exposure affects those systems. In all three lines of research, the microwave energy used was approximately the same (in frequencies, modulations and incident energies) as those emitted by present day cellular telephones, [4].
Microwaves really open up the blood brain barrier, [2]. The blood -brain barrier is a cell between the blood that circulates in the blood vessels of the brain and the actual brain tissue. The barrier lets oxygen and nutrition inside while carbon dioxide and waste products are transported out through it. The barrier hinders some medicines and several poisonous substances to invade and injured the brain. Phones make brain receptive to poison. New Swedish research shows that the radiation from mobile phones might make it easier for poison to penetrate into the brain. The microwave radiation from cell phones can open the safety barrier that is supposed to protect the brain from being invaded by poisonous substances contained in blood. Since albumen can get into the brain there is reason to believe that other smaller or equal sized molecules can too. Proteins found in the blood can, if they get to the brain, cause autoimmune diseases such as multiple sclerosis. Damaged nerve cells could also lead to dementia, premature aging, and memory loss is another damaging effect. In fact, the microwave radiation could split the DNA molecules in the brains of live rates. It could be the same at people. Some people are more sensitive to radiation than the average person. But, there is not yet way to identify them. For instance, several different genes provide every cell with the ability to repair routine injures to chromosome and DNA. People who are born with a faulty “repair gene” in every cell, are going to be more vulnerable than the average person to cancer induced by radiation and by other carcinogens (mutagens), [3].
If the ionized-radiation injured cell, it does not die. A damage chromosome or damaged piece of DNA can result in benign and malignant tumors. It is known that cancer begins with a single cell having abnormal genetic instructions. A cell s abnormal instructions cause it to do abnormal things- such as dividing too often, or forming a tumor, or migrating from its appropriate location to live and divide elsewhere in the body (metastasis), [3]. Living cells, whose abnormalities can be caused by radiation, do these cancerous activities: ionized and non -ionized. When ionized radiation is usedd to treat cancer, it is used in very high doses, which do enough damage to kill cells, and dead cells cannot behave like cancer.
Especially worrying is the fact that even very low microwave effects seem to affect the brain. But, in biological systems there are often windows where the organism is more sensitive. It could be used in purpose of prevention, like the fact that the lower frequencies penetrate deeper into the brain. Mobile phones emit microwave radiation whenever calls are made. It doesn’t seem to matter how long you talk on cellular phone; the blood-brain-barrier is opened at once. The albumen remains in the rat brains for several days after exposure to microwaves, [2].
IV. RF/MW Measurement Technique
Experimental methods for measuring electrical properties of biological tissues have several common features. At lower frequencies (f <100 MHz) a quasistatic approach is used, in both, time and frequency domain technique. At frequencies above 1 GHz the wave character of the phenomena has to be taken into account. The sample is normally placed in a coaxial line or waveguide and properties of reflected or transmitted waves are measured as they are related to the dielectric properties of the test material. At frequencies above 40 GHz free spaces quasioptical techniques are also used.
Time domain technique includes “time domain spectroscopy” (TDS) for determining the permitivity e (w) from measurements performed in the time domain. At present the TDS methods cover the frequency range from a fraction of a hertz to approximately 15 GHz. Frequency domain spectroscopy (FDS) is associated with experimental techniques for determining the permitivity e (w) from measurements performed in the frequency domain by means of a selected monochromatic signal. It has undergone a rapid development with the introduction of the automatic network analyzer, which is capable of accurate measurements of transmission and reflection coefficients in a wide band of frequencies from a few hertz to 100 GHz. All these equipment is very expensive and must be supported by states or big companies. There is a big problem: these companies don’t like the truth come on the day light!
Conclusion
To date, the scientific community has not provided evidence to prove, or disprove allegations that the RF/MW radiation emitted from cellular telephones is hazardous. While some studies conclude that exposure to RF/MW radiation emitted by cellular telephone could lead to adverse health effects, others suggest that cellular telephones are safe.
There is nothing novel in the conclusion that the laws of physics are powerless to predict and preclude some phenomena. Ultraviolet light, tobacco smoke, and as best each can cause cancer, but the known laws of nature neither predict nor explain the relationships. The inability to predict or preclude bioeffects in the physics thought-style is direct consequence of the complexity of the biological organisms, in particular, their no linearity. The ability to predict the future and to neglect small differences is usually confined context of closed linear systems. That is, systems that can be modeled linearly as they do not exchange energy with their surroundings. In these instances, the laws of physics explain and predict. The operation of automobiles, space ships, atomic bombs and similar are all achievements of 20th century physics. But earthquakes, volcano eruptions, the weather and the behavior of living beings can’t be predicted because these systems are open and they exchange energy with their environment and they are governed by nonlinear laws. It is simply that we do not know how to apply the laws of physics to them. Because of that, it is impossible to find the solution of the hazard problems within only the physics thought-style. It was necessary to use another way to establish scientific facts, the biological thought-style, too, what the scientists try to do.
References
[1] O.P.Gandhi: “Biological effects and Medical Applications
Of Electromagnetic Energy”, Prentice Hall, New Jersey,
07632,1990.
[2] A.H. Fray: “Headaches from Cellular Telephones,
Random line”, Inc. Potomac, MD, Environmental Health
Perspective, Vol. 106, Nm. 3, March 1998.
[3] Gofman, J.W., Answers to Frequently-Asked-Questions
About radiation, Egan O’ Connor of CNR, fall 1996.
[4] A. Philips: “Mobile Phone Adverse Health Concerns”,
EMFACT Consultancy 1999.
[5] S. Harris: ” Now Mobiles Give You Kidney Damage”,
EMFACTS Consultancy, dec. 1999.
[6] K.R. Foster, H.P. Schwan, “ Dielectric properties of tissues
and biological materials: a critical review”, CRC Critical
Reviews in Biomedical Engineering, vol. 17, pp. 25-104,
1989.
1Faculty of Electrical Engineering Banjaluka, Bosnia and
Herzegovina
2Medical Faculty Banjaluka
3student, Faculty of Electrical Engineering Banjaluka
e-mail: [email protected]
Dr Radojka Pra{talo
Elektrotehni~ki fakultet
Banjaluka
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