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By Yevgeny YESKOV, Dr. Sc. (Biol), Russian State Agrarian Extramural University
One of the objectives of ecology as science is to study the biospheric impact of a broad spectrum of electromagnetic fields of both natural and anthropogenic origins. The functioning of organisms, irrespective of complexity, is directly affected by the processes going on at the level of cells and tissues.
During the observable geological period the earth has been subjected to natural electromagnetic impacts of a broad frequency range-from slow ones related to the change of magnetic and electric fields to gamma-radiation. The appearance of their artificial analogs dates back to the second quarter of the 1800s when electric machines were invented and came into use (electric magnets, electric engines, power generators). Presently, their input in the total biospheric effect is comparable to the natural one, occasionally surpassing it*.
Natural electromagnetic phenomena are highly variable in time and space. For example, while on the North Pole of our planet their strength is about 48 A/m and on the South Pole it reaches 56, on the Equator the intensity of these phenomena makes just some meager 32 A/m. However, in the zones of magnetic anomalies which are scattered over the surface of the earth numerously, intensity gradients are largely out of joint. Incidentally, an opinion is held that the location of earth magnetic poles has changed time and again which is probably triggered by processes going on in the earth's bowels.
Our luminary also contributes to the variation of electromagnetic phenomena causing magnetic storms up to 200 gammas strong with distinct 11-year and 27-day cycles. However, the impact of the sun upon our mundane life is not limited to just that. Its ultraviolet radiation influences ionospheric currents determining daily fluctuations of the magnetic field horizontal component reaching 20-30 gammas.
On top of the above, there are also electric fields produced, primarily, by internebular discharges (atmospherics), with the intensity in thunderclouds and strata reaching up to 100 kV/m. However, the intensity value is unstable slumping at the
* See: A.V. Klimenko and others, "Monitoring Energy Uses and the Environment", Science in Russia, No. 2, 1996.- Ed.
moment of discharge and gaining afterwards. The above phenomena may be slow- developing with the frequency below 1 cycle, or surge up to dozens of kilocycles.
The mentioned natural electric field sources have artificial analogs, such as, e.g., power lines (PL). They pass through forests, over water reservoirs and small settlements. They cut into big cities, and their net is constantly growing. The field intensity created beneath them varies with the line and the location. Thus, at the height of 2 meters above the surface, under a 500 kV PL, the average electric field intensity equals 6 kV/m, or 11 kV/m under a 750 kV PL, or 17 kV/m under a 1,500 kVPL. The induced magnetic field is by a few orders of magnitude lower than that of the earth, and its impact upon biosphere can be ignored.
Apart from the electromagnetic waves, electric current is induced on the surface directly beneath PL. Its strength depends on the dampness of the soil and the voltage of a particular PL.
If the latter equals 500 kV, the induced current fluctuates between 2 and 3.7 mcA growing by 6-15 percent, depending on the dampness of the soil. 15-20 meters down, its strength, given all other equal conditions, decreases 1.5 times, while at a distance of 15-20 meters from the line it is too low to be detected.
Electric phenomena in aqueous milieu are somewhat different from those going on the land. Here they are related to telluric (earth) currents whose intensity and direction are subject to long-term (up to a few years) and short-term (from a few seconds to minutes) variations. Moreover, their amplitude changes from fractions to hundreds of mcV/m. By way of comparison, such magnitude of electric field is observed in the vicinity of some industrial sites.
GOOD OR HARM
Back in the 16th century Paracelsus, a German physician, first voiced a supposition that magnetic field is essential for normal vital functions of humans. Further practices have confirmed that he was right, and in the 18th century Luigi Galvani, an Italian physiologist, was the first to discover electric phenomena produced by animals' muscular contractions (the so-called "animal electricity"). Ever since researchers have been trying to use electric fields for therapeutic purposes. To be absolutely precise, some of them observed its physiological effects, while others registered no reaction in "guinea-pigs". Thus, Dr. A. Skorobogatov, a Russian physiologist, and his co-authors (1969) subjected rabbits to constant electric field with the intensity of 8 kV/m and found out that their breath frequency either increased (22 percent of the animals) or decreased (45 percent). In similar experiments on rats a 15-16-minute exposure to a field with the intensity of 19.5-400 kV/m caused higher pulse and breath frequency. But other researches (S. A. Chebotaryov with co-authors, 1968, and KG. Portnov, 1972) exposed animals to electric field for 4 hours in a row 6 times a week and registered no physiological changes, in spite of the fact that the rabbits were placed between electrodes to which 15 kV current was applied, and in a month and a half they were reex-amined.
Now, for the influence of electric fields on humans. Many people are exposed to PL or work at enterprises using dielectrics which produce strong static discharges at friction. To find out the effect of such conditions upon human health, in the late 1960s of the past century a group of people were subjected to thorough examination. Individuals exposed to a constant electric field with the intensity of 2 kV/m during 2 hours daily for 50-60 days in a row showed no deviations from the standard of higher nervous system functioning. The body temperature, pulse frequency, arterial blood pressure and blood composition were normal too.
The above elicits a conclusion that direct exposure to constant electric fields provokes no physiological changes in the human or animal organism. Occasionally identified variance with the normal in the case of persons working with electrolyzed materials is most probably related to by-effects, such as electrical discharges and air ozoning under the impact of electrical charges near the sources of high voltage and ionization.
But a very different picture emerges once we have to appraise the influence upon the organisms of warm-blooded animals and humans of alternating electric fields broadly proliferated in everyday life. Special attention should be paid to the ecological effects of the so-called infra-low fields-less than 20 cycles-and electric fields of industrial frequencies-50-60 cycles. The former belong to the spectrum comprising the earth's natural background, the latter are transmitted over long distances via PL, and both are by far not as harmless as constant electric fields.
Thus, A. P. Volynsky in his experiments conducted in 1971 upon rabbits discovered that being subjected to an electric field with the frequency of 8 cycles and the intensity of just 0.1-0.5 kV/m the animals produced higher frequency and amplitude of electroencephalogram. When exposed to electric fields of industrial frequency the same animals experienced the disruption of muscular movement coordination and thermoregulation and blood pressure growth. However, that was not the case when rabbits were injected Novocain in the sacrum of the spinal cord.
People too experience negative effects of electric fields with the frequency of 50-60 cycles. They complain of profuse sweating, hyperex-citability or, conversely, those signs of ailment getting all the more pronounced as the field intensity is growing. The phenomena can be observed right under PLs or in their direct vicinity.
The negative effect of industrial frequency electric fields on distribution substations' and PL service personnel has captured the attention of scientists. Experiments conducted in 1975 through 1985 at the Research Institute of Power Engineering (Novosibirsk), the Research Institute of Biology and Biophysics (Tomsk), the Engineering and Pedagogical Institute (Sverdlovsk) and other institutions have revealed that the principal organism derangements caused by the impact of low- frequency electric fields include vegetative dysfunction, tachycardia, arterial hypertension*, fatigue and insomnia. It should be noted that the incidence of industrial disease is the function of the track record.
Thus, employees of distribution substations, after 7 or 10 years of work, display hyperexcitability of the peripheral nervous system, a certain relaxation of inhibition processes and a substantial increase of neutrophils' (a form of leucocytes) activity. Remarkably, the number of leucocytes declines during the first two years of work at a substation, and in about 3 to 6 years it is almost back to normal. However, their composition is changed: the number of neutrophils is increased and that of lymphocytes is reduced.
Since humans and warm-blooded animals have no special sensors of electric field, they can only perceive it in an oblique way. A mechanism of such sensitivity is based upon the irritation of exteroceptors (receptors localized on the body surface) with induced currents. Under a 500 kV PL the human body experiences currents 100 mcA strong.
As N. G. Novikov proved in 1984, induced currents also irritate biologically active zones on the body surface (humans have 664 such zones). Acting upon those, as distinct from "non-active" skin area, results in hyperesthesia due to a decreased electric resistance, producing a material effect upon the organism physiological condition. Thus, with the electric field intensity at 5 kV/m and a 50-cycle frequency, active areas sustain an electric current of a few, and at 20 kV/m-hundreds of microamperes. That 3-5 times exceeds currents on non-active areas of the skin. As for a direct impact of electric fields on the central nervous system, it is unlikely because of the high conductivity of skin and the adjacent tissues screening the organism and keeping electric oscillations off.
Invertebrates display the highest diversity of species (about 1,260,000). Insect species alone total almost 1 million. However, little is known yet about the influence of electric fields upon those.
In the recent years it has been the honeybee that captured the attention of researchers. It is so far the only representative of fauna that has proven to have an organ perceiving low-frequency electric fields* and use static electricity in the system of spatial orientation and intranets communications**.
Naturally, experiments conducted in different countries to assess the impact of constant electric field upon insects' vital functions were not limited to only that. Studying the moth of the Geometridae family, American scholar D. Edwards in 1961 discovered that an electric field with the intensity of 18 kV/m caused the reduction of oviposition, however the percentage share of males in the population grew. Still earlier, in 1986, Japanese naturalist Shima Toshio with co-authors established a negative effect of a 15-180-minute exposure to the field of fruit flies (Drosophilidae family) pupa resulting in increased incidence of abnormal development. New data did not linger to follow. Thus, it was discovered that isolated honeybees placed in a high-intensity field developed a higher oxygen demand, while sawflies (Tenthredinidae family) experienced the growth of the body liquid fractions freezing temperature. However, despite the luring prospects promised by the data obtained (sex regulation, freeze-resistance, etc.), due to the low reproducibility, the observed effects could not be tapped.
Reaction of insects to electrostatic charges on surfaces deserves special attention. Here is the description of an experiment which the author conducted on bees. At the mouth of a hive a 1.5-2.5 cm wide metallic plate was placed hooked up to a DC 250- 300 V source. Whenever that happened, the insects' movements on the plate at first paced down 5-7 times, however pretty soon they would resume their normal tread. A similar phenomenon was observed at take-off: the "last steps" were as hard to make. Such response to an energized conductor was observed in the case of other insects too. As they approached a conductor they might halt at 30-40 V, or even come to a complete stop at 100 V.
Some researchers believe: bees react to an increased intensity of a constant electric field and growing air ionization. That is supposed to explain why, as it has long been observed, they stop flying before thunderstorm. However, such supposition did not stand the tests we conducted in 1990. Then the insects' condition was appraised on the basis of several ethological indicators, including the range and intensity of produced sounds, the stability of intranets thermoregulation and flight activity. Despite the fact that the intensity of constant electric field reached 15 kV/m, and ion concentration amounted to 2.106/cm 3 , the bees behaved in the good old way.
But it is the other way round when invertebrates are exposed to low-frequency electric fields. Observing such instances during quite a long time span between 1966 and 2001,
* Hypertension-increased hydrostatic pressure in blood vessels, and body cavities.- Ed.
* See: Ye. Yeskov, "Trichoid sensillae: what is that?", Science in Russia, No. 5, 1997.- Ed.
** See: Ye. Yeskov, "Plants and animals-electromagnetic links?", Science in Russia, No. 1, 2002.-Ed.
I discovered a great variety of responses. For example, the population of grasshoppers dwelling under a PL and in its direct vicinity depends on the voltage and the distance. Directly under the line the number of insects is minimal, but at a distance of 100 meters from a 110 kV PL, it grows, on the average, 1.3 times, while in the zone of a 500 kV PL the corresponding magnification is 2.5 times.
The data may change a great deal with the weather. Thus, grasshoppers stay off power lines in nasty days with a high relative humidity. When it reaches 44 percent grasshoppers' density under a 500 kV PL is 3.6 times lower than at a distance of 100 m from it, and 5.7 times as low under 89 percent humidity.
Conversely, earthworms tend to swarm under power lines. As you retreat from a 500 kV PL by 25 meters, their quantity decreases 1.4 times on the average, as you retreat by 50 m-1.4 and by 100 m-2.6 times, respectively. It is noteworthy that the results of the experiments were substantially influenced by the presence of vegetation which partially shields low-frequency electric fields. That is corroborated by the fact that under a 500 kV PL in a cereal field we found the average of 138 worms per square meter, while under bushes there were 159 earthworms.
However, let us get back to bees as the best studied representatives of shoney harvest beehives are often placed in forest areas under power lines or in their vicinity, because in such places trees are cut down and the clearings are overgrown with honey plants. But the desired effect is not readily attained, since power lines disrupt intranest thermoregulation. While in the location of a bee hatch the normal temperature does not exceed 36 degrees Centigrade, in beehives under 500 kV PLs it not just grows but for a few minutes fluctuates within 5C or may vary from 36-37C to 40-41C. Bees cannot adjust to such conditions, and the only thing to be done is to remove beehives from PL.
Another negative factor of alternating electric fields consists in their repellant effect which is strong enough to cause the bees gathered on a feeder with honey or a sucrose solution take off at the activation of a 50+/-10 kV/m field. When the danger passes the insects return back.
Another effect of electric field is stimulation of the locomotions of bees and paper wasps called so because they build their nests of paper. In the former hyperactivity is caused by the field frequency of 500 cycles and intensity of 20-30 kV/m. For the latter it takes just 7 kV/m in other equal conditions.
As distinct from the above insects, red forest ants react to electric field by slowing down. At the field intensity of 80-90 kV/m they slowly ascend their hill and take defensive postures. Many of them discharge protective acidic secretion.
Now let us take a look at the blood-sucking mosquito. In 1998 V. M. Orlov from Tomsk established that with the electric field intensity of 10 kV/m it starts to fly much slower. At 40-60 kV/m the insect loses trophic motivation (stops to attack people and animals). Besides, the probability of its electric resistance in such conditions decreases by 30 percent even at 5 kV/m and disappears completely at 30-40 kV/m.
So, among the reviewed invertebrate species it is paper wasps that are the most sensitive to alternating electric field. Their average perceptive threshold is 0.04 kV/m at the frequency of 500 cycles. On the contrary, red forest ants proved to be
the most "thick-skinned".
Repeated studies have demonstrated that insects perceive low-frequency electric fields with two different mechanisms. One of them is connected with the use of mechanoreceptors (different types of antennae, trichoid sensillae and so forth) reacting to electric field with the vibration of their primary transformers. The second mechanism is based on the irritation with currents induced at the points of insects' contacts with each other and with conductive surfaces.
WHAT ABOUT FLORA?
The study of plants' reaction to electric impact dates back to the late 1800s-early 1900s when Indian naturalist Bos established that every plant reacts to irritation by electric current, particularly, with the change of the direction in which it shoots off roots. The roots, just like sprouts, bend under the influence of direct current (galvanotropism), due to the faster or slower growth on one side which may result from either a shift in anion and cation concentrations taking place at the electrolysis of plant salts, or the dislocation of hormones. The orientation of a shoot (a root) relative to the electric field vector determines the direction of the bend and the rate of growth. The latter is faster if the field vector coincides with the axis of the shoot, and its apex is turned to the positive electrode. The reversal of poles produces the opposite effect, and with the electric field vector positioned at a square angle to the longitudinal axis of a root or a shoot, the plant is developing, irregularly shooting off plenty of sprouts. The galvanotropism phenomenon has a high reproducibility, opening up broad opportunities for utilization in irrigated agriculture and hydroponics. The experiments conducted by the author jointly with N. Krasikov and T. Marenkova in 2002 have demonstrated: a substantial effect upon the growth and development of plants is exerted by the electrolyzing of water with a direct current field. A considerable role in the process is played by admixtures. Thus, the presence of calcium, sodium or magnesium in the water inhibits the process (distilled water purified of the above elements is charged better).
So, why does electrolyzed water better stimulate the growth of plants? The truth is, the occurred volumetrical and charge polarization fosters water structuring, positioning its molecules in a definite order, rather than erratically. In such metastable state water is easier and faster to consume for seeds and, in the end of the day, speeds up their germination. Irrigated with such water plantules develop faster.
The experiments carried out at the Research Institute of Biology and Biophysics (Tomsk) in 1984 established: alternating electric fields also affect soil processes vital for plants' growth. The fact is that an industrial frequency electric field changes the cellulase activity of soil (cellulase is an enzyme splitting up cellulose). Higher or lower activity of this enzyme proves to depend on the plant species exposed to electric field. For example, under a 500 kV PL red hawk's-beard plantations show a higher cellulase activity by growing faster, but it is vice versa in the case of peas.
Hence, it has been proven that constant, especially low-frequency, electric fields produce a broad range of biological effects, and the consequences depend on their magnitude and duration. The last but not the least role is played by ecological situation and the degree of the organisms' complexity. However, we are still up for plenty of surprises in the course of further research.
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