The sources of electromagnetic fields (EMF) are extremely diverse - these are power transmission and distribution systems (power lines - power lines, transformer and distribution substations) and devices that consume electricity (electric motors, electric stoves, electric heaters, refrigerators, TVs, video display terminals, etc.).
Sources that generate and transmit electromagnetic energy include radio and television broadcasting stations, radar installations and radio communication systems, a wide variety of technological installations in industry, medical devices and equipment (devices for diathermy and inductothermy, UHF therapy, devices for microwave therapy and etc.).
The working contingent and the population may be exposed to isolated electric or magnetic components of the field, or a combination of both. Depending on the attitude of the exposed person to the source of exposure, it is customary to distinguish between several types of exposure - professional, non-professional, exposure in the home and exposure carried out for medical purposes. Occupational exposure is characterized by a variety of generation modes and options for exposure to electromagnetic fields (radiation in the near zone, in the induction zone, general and local, combined with the action of other adverse factors production environment). In terms of non-professional exposure, the most typical is general exposure, in most cases in the wave zone.
Electromagnetic fields generated by various sources can affect the entire body of a working person (general exposure) or a separate part of the body (local exposure). At the same time, exposure can be isolated (from one EMF source), combined (from two or more EMF sources of the same frequency range), mixed (from two or more EMF sources of different frequency ranges), and also combined (under conditions of simultaneous exposure to EMF). and other adverse physical factors of the working environment) impact.
An electromagnetic wave is an oscillatory process associated with interrelated electric and magnetic fields that change in space and time.
The electromagnetic field is the area of distribution of electromagnetic
Characteristics of electromagnetic waves. The electromagnetic field is characterized by the radiation frequency f, measured in hertz, or the wavelength X, measured in meters. An electromagnetic wave propagates in vacuum at the speed of light (3 108 m/s), and the relationship between the length and frequency of an electromagnetic wave is determined by the dependence
where c is the speed of light.
The speed of wave propagation in air is close to the speed of their propagation in vacuum.
The electromagnetic field has energy, and the electromagnetic wave, propagating in space, carries this energy. The electromagnetic field has electric and magnetic components (Table No. 35).
The electric field strength E is a characteristic of the electrical component of the EMF, the unit of which is V/m.
tension magnetic field H (A / m) is a characteristic of the magnetic component of the EMF.
The energy flux density (PEF) is the energy of an electromagnetic wave carried by an electromagnetic wave per unit time through a unit area. The PES unit is W/m.
Table No. 35. EMF intensity units in the International System of Units (SI)
|
For separate ranges of electromagnetic radiation - EMP (light range, laser radiation) other characteristics are introduced.
Classification of electromagnetic fields. The frequency range and wavelength of the electromagnetic wave make it possible to classify the electromagnetic field into visible light (light waves), infrared (thermal) and ultraviolet radiation, the physical basis of which is electromagnetic waves. These types of short-wave radiation have a specific effect on a person.
physical basis ionizing radiation also constitute electromagnetic waves of very high frequencies, which have high energy, sufficient to ionize the molecules of the substance in which the wave propagates (Table No. 36).
The radio frequency range of the electromagnetic spectrum is divided into four frequency ranges: low frequencies (LF) - less than 30 kHz, high frequencies (HF) - 30 kHz ... 30 MHz, ultra-high frequencies (UHF) - 30 ... 300 MHz, ultra-high frequencies ( microwave) - 300 MHz. 750 GHz.
A special kind of electromagnetic radiation (EMR) is laser radiation (LI) generated in the wavelength range of 0.1...1000 µm. A feature of LI is its monochromaticity (strictly one wavelength), coherence (all radiation sources emit waves in the same phase), sharp beam directivity (small beam divergence).
Conditionally to non-ionizing radiation(fields) include electrostatic fields (ESF) and magnetic fields (MF).
An electrostatic field is a field of fixed electric charges that interacts between them.
Static electricity is a set of phenomena associated with the emergence, conservation and relaxation of a free electric charge on the surface or in the volume of dielectrics or on insulated conductors.
The magnetic field can be constant, pulsed, variable.
Depending on the sources of formation, electrostatic fields can exist in the form of the electrostatic field itself, which is formed in different kind power plants and in electrical processes. In industry, ESPs are widely used for electrogas cleaning, electrostatic separation of ores and materials, electrostatic application of paint and varnish and polymeric materials. manufacturing, testing,
transportation and storage of semiconductor devices and integrated circuits, grinding and polishing of cases of radio and television receivers,
technological processes associated with the use of dielectric
materials, as well as the premises of computer centers, where multiplying computer technology is concentrated, are characterized by the formation
electrostatic fields. Electrostatic charges and the electrostatic fields created by them can occur when dielectric liquids and some bulk materials move through pipelines, pour dielectric liquids, roll film or paper into a roll.
Table number 36. International classification of electromagnetic waves
|
Electromagnets, solenoids, capacitor-type installations, cast and metal-ceramic magnets are accompanied by the appearance of magnetic fields.
Three zones are distinguished in electromagnetic fields, which are formed at different distances from the source of electromagnetic radiation.
Induction zone (near zone) - covers the gap from the radiation source to a distance equal to approximately U2n ~ U6. In this zone, the electromagnetic wave has not yet been formed, and therefore the electric and magnetic fields are not interconnected and act independently (the first zone).
Interference zone (intermediate zone) - located at distances from approximately U2p to 2lX. In this zone, the formation of EMW occurs and the person is affected by electric and magnetic fields, as well as an energy effect (second zone).
Wave zone (far zone) - is located at distances over 2nX. In this zone, an electromagnetic wave is formed, electric and magnetic fields are interconnected. A person in this zone is affected by the energy of the wave (the third zone).
Action electromagnetic field on the body. The biological and pathophysiological effect of exposure to electromagnetic fields on the body depends on the frequency range, the intensity of the influencing factor, the duration of exposure, the nature of the radiation and the mode of exposure. The effect of EMF on the body depends on the patterns of radio wave propagation in material media, where the absorption of electromagnetic wave energy is determined by the frequency of electromagnetic oscillations, electrical and magnetic properties of the medium.
As is known, the leading indicator characterizing the electrical properties of body tissues is their dielectric and magnetic permeability. In turn, differences in the electrical properties of tissues (dielectric and magnetic permeability, resistivity) are associated with the content of free and bound water in them. All biological tissues, according to the dielectric constant, are divided into two groups: tissues with a high water content - over 80% (blood, muscles, skin, brain tissue, liver and spleen tissue) and tissues with a relatively low water content (fat, bone). The absorption coefficient in tissues with a high water content, at the same field strength, is 60 times higher than in tissues with a low water content. Therefore, the penetration depth of electromagnetic waves in tissues with a low water content is 10 times greater than in tissues with a high water content.
The thermal and athermal effects underlie the mechanisms of the biological action of electromagnetic waves. The thermal effect of EMF is characterized by selective heating of individual organs and tissues, an increase general temperature body. Intense EMF irradiation can cause destructive changes in tissues and organs, however, acute forms of damage are extremely rare and their occurrence is most often associated with emergencies in case of safety violation.
Chronic forms of radio wave lesions, their symptoms and course do not have strictly specific manifestations. However, they are characterized by the development of asthenic conditions and vegetative disorders, mainly with
side of the cardiovascular system. Along with general asthenia accompanied by weakness, fatigue, restless sleep, patients develop headache, dizziness, psycho-emotional lability, pain in the heart area, excessive sweating, decreased appetite. Signs of acrocyanosis, regional hyperhidrosis, coldness of the hands and feet, tremor of the fingers, lability of the pulse and blood pressure with a tendency to bradycardia and hypotension develop; dysfunction in the pituitary-adrenal cortex system leads to changes in the secretion of thyroid and gonadal hormones.
One of the few specific lesions caused by exposure to electromagnetic radiation of the radio frequency range is the development of cataracts. In addition to cataracts, when exposed to electromagnetic waves of high frequencies, keratitis and damage to the corneal stroma can develop.
Infrared (thermal) radiation, light emission at high energies, as well as ultraviolet radiation of a high level, with acute exposure, can lead to expansion of capillaries, burns of the skin and organs of vision. Chronic exposure is accompanied by a change in skin pigmentation, the development of chronic conjunctivitis and clouding of the lens of the eye. Ultraviolet radiation of low levels is useful and necessary for humans, as it helps to enhance metabolic processes in the body and the synthesis of a biologically active form of vitamin D.
The effect of exposure to laser radiation on a person depends on the intensity of the radiation, wavelength, nature of the radiation and exposure time. At the same time, local and general damage to certain tissues of the human body is distinguished. In this case, the target organ is the eye, which is easily damaged, the transparency of the cornea and lens is disturbed, and damage to the retina is possible. Laser study, especially in the infrared range, is able to penetrate tissues to a considerable depth, affecting internal organs. Prolonged exposure to laser radiation of even low intensity can lead to various functional disorders of the nervous, cardiovascular systems, endocrine glands, blood pressure, increased fatigue, and decreased performance.
Hygienic regulation of electromagnetic fields. According to regulatory documents: SanPiN "Sanitary and epidemiological requirements for the operation of radio electronic equipment with the conditions for working with sources of electromagnetic radiation" No. 225 dated 10.04.2007 of the Ministry of Health of the Republic of Kazakhstan; SanPiN "Sanitary rules and norms for the protection of the population from the effects of electromagnetic fields created by radio engineering objects" No. 3.01.002-96 of the Ministry of Health of the Republic of Kazakhstan; MU
“Guidelines for the implementation of state sanitary supervision of objects with sources of electromagnetic fields (EMF) of the non-ionizing part of the spectrum” No. 1.02.018 / y-94 of the Ministry of Health of the Republic of Kazakhstan; MU "Methodological recommendations for laboratory monitoring of sources of electromagnetic fields of the non-ionizing part of the spectrum (EMF) in the implementation of state sanitary supervision" No. 1.02.019 / r-94 of the Ministry of Health of the Republic of Kazakhstan regulates the intensity of electromagnetic fields of radio frequencies at the workplaces of personnel,
carrying out work with sources of electromagnetic fields and the requirements for monitoring, as well as regulated exposure to an electric field, both in terms of intensity and duration of action.
The frequency range of radio frequencies of electromagnetic fields (60 kHz - 300 MHz) is estimated by the strength of the electric and magnetic components of the field; in the frequency range of 300 MHz - 300 GHz - the surface density of the radiation energy flux and the energy load (EN) created by it. The total energy flux passing through the unit of the irradiated surface during the action (T) and expressed as the product of the PES T is the energy load.
At the workplaces of personnel, the EMF intensity in the frequency range of 60 kHz - 300 MHz during the working day should not exceed the established maximum permissible levels (MPL):
In cases where the time of exposure to EMF on personnel does not exceed 50% of the working time, levels higher than those indicated, but not more than 2 times, are allowed.
Rationing and hygienic assessment of permanent magnetic fields (PMF) in industrial premises and workplaces (Table No. 37) is carried out differentiated, depending on the time of exposure to the worker during work shift and taking into account the conditions of general or local exposure.
| Table No. 37 |
The PMF hygienic standards (Table No. 38), developed by the International Committee on Non-Ionizing Radiation, which operates under the International Association for Radiation Protection, are also widely used.
What is EMF, its types and classification
In practice, when characterizing the electromagnetic environment, the terms "electric field", "magnetic field", "electromagnetic field" are used. Let us briefly explain what this means and what connection exists between them.
The electric field is created by charges. For example, in all well-known school experiments on the electrification of ebonite, there is just an electric field.
A magnetic field is created when electric charges move through a conductor.
To characterize the magnitude of the electric field, the concept of electric field strength is used, the designation E, the unit of measurement is V / m (Volt-per-meter). The magnitude of the magnetic field is characterized by the strength of the magnetic field H, unit A/m (ampere-per-meter). When measuring ultra-low and extremely low frequencies, the concept of magnetic induction B, the unit T (Tesla), is also often used, one millionth of T corresponds to 1.25 A / m.
By definition, an electromagnetic field is a special form of matter through which an interaction is carried out between electrically charged particles. The physical reasons for the existence of an electromagnetic field are related to the fact that a time-varying electric field E generates a magnetic field H, and a changing H generates a vortex electric field: both components E and H, continuously changing, excite each other. The EMF of stationary or uniformly moving charged particles is inextricably linked with these particles. With the accelerated movement of charged particles, the EMF "breaks away" from them and exists independently in the form of electromagnetic waves, not disappearing with the removal of the source (for example, radio waves do not disappear even in the absence of current in the antenna that emitted them). 
Electromagnetic waves are characterized by a wavelength, the designation is l (lambda). A source that generates radiation, and in fact creates electromagnetic oscillations, is characterized by a frequency, the designation is f.
An important feature of the EMF is its division into the so-called "near" and "far" zones. In the "near" zone, or induction zone, at a distance from the source r< l ЭМП можно считать квазистатическим.
Здесь оно быстро убывает с расстоянием,
обратно пропорционально квадрату r -2
или кубу r -3 расстояния. В "ближней"
зоне излучения электромагнитная волне
еще не сформирована. Для характеристики
ЭМП измерения переменного электрического
поля Е и переменного магнитного поля Н
производятся раздельно. Поле в зоне
индукции служит для формирования бегущих
составляющей полей (электромагнитной
волны), ответственных за излучение.
"Дальняя" зона - это зона
сформировавшейся электромагнитной
волны, начинается с расстояния r >3l. In the "far" zone, the field intensity decreases inversely with the distance to the source r -1. 
In the "far" zone of radiation there is a connection between E and H: E = 377N, where 377 is the vacuum impedance, Ohm. Therefore, as a rule, only E is measured. In Russia, at frequencies above 300 MHz, the electromagnetic energy flux density (PEF), or the Poynting vector, is usually measured. Referred to as S, the unit of measure is W/m2. PES characterizes the amount of energy carried by an electromagnetic wave per unit time through a unit surface perpendicular to the direction of wave propagation.
International classification of electromagnetic waves by frequency
|
Name of the frequency range |
Range limits |
Name of the wave range |
Range limits |
|
Extreme low, ELF |
Decamegameter | ||
|
Ultra low, VLF |
30 – 300 Hz |
Megameter | |
|
Infralow, ILF |
Hectokilometer |
1000 - 100 km |
|
|
Very low, VLF |
Myriameter | ||
|
Low frequencies, LF |
30 - 300 kHz |
Kilometer | |
|
Medium, midrange |
Hectometric | ||
|
Treble, HF |
Decameter | ||
|
Very high, VHF |
30 - 300 MHz |
Meter | |
|
Ultra high,UHF |
decimeter | ||
|
Ultra high, microwave |
centimeter | ||
|
Extremely high, EHF |
30 - 300 GHz |
Millimeter | |
|
Hyper high, GHF |
300 - 3000 GHz |
decimillimeter |
2. Main sources of emp
Among the main sources of EMP can be listed:
Personal computers
Electric transport (trams, trolleybuses, trains,…)
Power lines (urban lighting, high voltage,…)
Wiring (inside buildings, telecommunications,…)
Household electrical appliances
Television and radio stations (transmitting antennas)
Satellite and cellular communications (transmitting antennas)
2.1 Electric transport
Electric transport - electric trains (including metro trains), trolleybuses, trams, etc. - is a relatively powerful source of a magnetic field in the frequency range from 0 to 1000 Hz. According to (Stenzel et al., 1996), the maximum values of the flux density of magnetic induction B in suburban "trains" reach 75 μT with an average value of 20 μT. The average value of V in a vehicle with a DC electric drive is fixed at 29 µT. A typical result of long-term measurements of the levels of the magnetic field generated by railway transport at a distance of 12 m from the track is shown in the figure.
2.2 Power lines
The wires of a working power line create electric and magnetic fields of industrial frequency in the adjacent space. The distance to which these fields propagate from the wires of the line reaches tens of meters. The range of propagation of the electric field depends on the voltage class of the power transmission line (the number indicating the voltage class is in the name of the transmission line - for example, a 220 kV transmission line), the higher the voltage, the larger the zone of an increased level of the electric field, while the dimensions of the zone do not change during the operation of the transmission line.
The range of propagation of the magnetic field depends on the magnitude of the flowing current or on the load of the line. Since the load of the power transmission line can change several times both during the day and with the change of the seasons of the year, the size of the zone of an increased level of the magnetic field also changes.
Biological action
Electric and magnetic fields are very strong factors influencing the state of all biological objects that fall into the zone of their influence. For example, in the area of action of the electric field of power lines, insects show changes in behavior: thus, increased aggressiveness, anxiety, decreased efficiency and productivity, and a tendency to lose queens are recorded in bees; in beetles, mosquitoes, butterflies and other flying insects, a change in behavioral responses is observed, including a change in the direction of movement towards a lower field level.
Anomalies of development are common in plants - the shapes and sizes of flowers, leaves, stems often change, extra petals appear. A healthy person suffers from a relatively long stay in the field of power lines. Short-term exposure (minutes) can lead to a negative reaction only in hypersensitive people or in patients with certain types of allergies. For example, the works of British scientists in the early 90s are well known, which showed that a number of allergy sufferers develop an epileptic-type reaction under the action of the power line field. With a long stay (months - years) of people in the electromagnetic field of power lines, diseases can develop mainly of the cardiovascular and nervous systems of the human body. IN last years among the long-term consequences are often called oncological diseases.
Sanitary standards
Studies of the biological effect of EMF FC, carried out in the USSR in the 60-70s, focused mainly on the effect of the electrical component, since no significant biological effect of the magnetic component at typical levels was found experimentally. In the 1970s, stringent standards were introduced for the population in terms of EP IF, and to this day they are one of the most stringent in the world. They are set out in the Sanitary Norms and Rules "Protection of the population from the effects of an electric field created by overhead power lines of alternating current of industrial frequency" No. 2971-84. In accordance with these standards, all power supply facilities are designed and built.
Despite the fact that the magnetic field around the world is now considered the most dangerous to health, the maximum permissible value of the magnetic field for the population in Russia is not standardized. The reason is that there is no money for research and development of norms. Most of the power lines were built without taking into account this danger.
Based on mass epidemiological surveys of the population living in conditions of exposure to magnetic fields of power lines as a safe or "normal" level for conditions of prolonged exposure, which does not lead to oncological diseases, independently of each other, Swedish and American experts recommended the value of the magnetic flux density of 0.2 - 0.3 μT.
Principles for ensuring the safety of the population
The basic principle of protecting public health from the electromagnetic field of power lines is to establish sanitary protection zones for power lines and reduce the electric field strength in residential buildings and in places where people can stay for a long time by using protective screens.
The boundaries of the sanitary protection zones for power transmission lines of which on operating lines are determined by the criterion of electric field strength - 1 kV / m.
Borders of sanitary protection zones for power lines in accordance with SN No. 2971-84
|
Power line voltage | ||||
|
The size of the sanitary protection (security) zone |
Borders of sanitary protection zones for power lines in Moscow
|
Power line voltage | |||||||
|
The size of the sanitary protection zone |
The placement of ultra-high voltage overhead lines (750 and 1150 kV) is subject to additional requirements for the conditions of exposure to an electric field on the population. So, the nearest distance from the axis of the designed 750 and 1150 kV overhead lines to the boundaries of settlements should, as a rule, be at least 250 and 300 m, respectively.
How to determine the voltage class of power lines? It is best to contact the local energy company, but you can try visually, although it is difficult for a non-specialist:
330 kV - 2 wires, 500 kV - 3 wires, 750 kV - 4 wires. Below 330 kV, one wire per phase, it can only be determined approximately by the number of insulators in a garland: 220 kV 10-15 pcs., 110 kV 6-8 pcs., 35 kV 3-5 pcs., 10 kV and below - 1 pc. .
Permissible levels of exposure to the electric field of power lines
|
remote control, kV/m |
Irradiation conditions |
|
inside residential buildings |
|
|
within the residential area |
|
|
in a populated area outside the residential area; (land of cities within the city limits within the boundaries of their prospective development for 10 years, suburban and green areas, resorts, land of urban-type settlements within the settlement line and rural settlements within the boundaries of these points) as well as on the territory of vegetable gardens and orchards; |
|
|
at the intersections overhead lines power transmission with motor roads 1 - IV categories; |
|
|
in uninhabited areas (undeveloped areas, even though often visited by people, accessible for transport, and agricultural land); |
|
|
in hard-to-reach areas (inaccessible to transport and agricultural machines) and in areas specially fenced off to exclude access to the population. |
Within the sanitary protection zone of the overhead line, it is prohibited:
place residential and public buildings and structures;
arrange areas for parking and stopping all types of transport;
to locate car service enterprises and warehouses for oil and oil products;
carry out operations with fuel, repair machines and mechanisms.
Territories of sanitary protection zones are allowed to be used as agricultural land, but it is recommended to grow crops on them that do not require manual labor.
In the event that in some areas the electric field strength outside the sanitary protection zone turns out to be higher than the maximum allowable 0.5 kV / m inside the building and above 1 kV / m on the territory of the residential development zone (in places where people can stay), they must steps should be taken to reduce tensions. To do this, almost any metal grid is placed on the roof of a building with a non-metal roof, grounded at least at two points. In buildings with a metal roof, it is enough to ground the roof at at least two points. In household plots or other places where people stay, the power frequency field strength can be reduced by installing protective screens, for example, reinforced concrete, metal fences, cable screens, trees or shrubs at least 2 m high.
All sources of EMF, depending on the origin, are divided into natural and anthropogenic.
In the spectrum natural electromagnetic fields can be conditionally divided into three components:
· geomagnetic field (GMF) of the Earth;
the electrostatic field of the Earth;
· variable EMF in the frequency range from 10 to 10 Hz.
The Earth's natural electric field is generated by an excess negative charge on the surface, and its strength in open areas is usually in the range of 100 to 500 V/m. Thunderclouds can increase the intensity of this field up to tens or hundreds of kV/m.
The geomagnetic field of the Earth consists of the main constant field (its contribution is 99%) and the variable field (1%). The existence of a constant magnetic field is explained by the processes occurring in the liquid metal core of the Earth. In the middle latitudes, its strength is approximately 40 A / m, at the poles 55.7 A / m.
The variable geomagnetic field is generated by currents in the magnetosphere and ionosphere. For example, strong disturbances of the magnetosphere can be caused by magnetic storms that multiply the amplitude of the variable component of the geomagnetic field. Magnetic storms are the result of penetration into the atmosphere of charged particles flying from the Sun at a speed of 1000 ... 3000 km / s, the so-called solar wind, the intensity of which is due to solar activity (solar flares, etc.).
Thunderstorm activity (0.1 ... 15 kHz) contributes to the formation of the natural electromagnetic background of the Earth. Electromagnetic oscillations at frequencies of 4 ... 30 Hz almost always exist. It can be assumed that they can serve as synchronizers of some biological processes, since they are resonant frequencies for a number of them.
The spectrum of solar and galactic radiation reaching the Earth includes EMP of the entire radio frequency range, infrared and ultraviolet radiation, visible light, ionizing radiation.
The human body emits EMF with a frequency above 300 GHz with an energy flux density of 0.003 W/m². If the total surface area of the medium human body 1.8 m², then the total radiated energy is approximately 0.0054 W.
At present, for the first time in the world, Russian scientists have developed hygienic recommendations regulating human exposure to weakened geomagnetic fields. The reason for such studies was complaints about the deterioration in the well-being and health of persons working in specialized shielded facilities, which, due to their design features, prevent EMR of natural origin from penetrating into them.
Weakened natural geomagnetic fields (GMF) can also be created in underground structures of the subway (levels of natural GMF are reduced by 2...5 times), in residential buildings made of reinforced concrete structures (by 1.5 times), in car interiors (in 1.5 ... 3 times), as well as in airplanes, bank vaults, etc.
When a person is in a deficit of natural EMF, a number of functional changes occur in the leading systems of the body: an imbalance of the main nervous processes in the form of predominance of inhibition, dystonia of cerebral vessels, changes in the cardiovascular and immune systems develop, etc.
Anthropogenic EMF sources, in accordance with the international classification, are divided into two groups:
sources generating extremely low and ultra-low frequencies from 0 to 3 kHz;
· sources generating radiation in the radio frequency range from 3 kHz to 300 GHz, including microwave radiation.
The first group includes, first of all, all systems of production, transmission and distribution of electricity (power lines - transformer substations, power plants, electrical wiring systems, various cable systems); office electrical and electronic equipment, electric transport: railway transport and its infrastructure, urban - metro, trolleybus, tram.
The length of power lines in our country is more than 4.5 million km. The power transmission line wires are the source of energy radiation into the surrounding space. Despite the fact that the electromagnetic energy of the power frequency field (50 Hz) is largely absorbed by the soil, the field strength under the wires and near them can be significant and depends on the voltage class of the power transmission line, load, suspension height, distance between the wires, vegetation cover, relief below the line.
Sources of EMF in the range of 3 kHz ... 300 GHz are transmitting radio centers, radio stations in the LF, MF, EHF ranges, FM radio stations (87.5 ... 10 MHz), mobile phones, radar stations (meteorological, airports), microwave heating installations, VDT and personal computers, etc.
The impact of high levels of EMP, created, for example, by transmitting radio centers (RTCs), in many cases, affects not only RRTs employees, but also people who are in adjacent houses. PRTs include one or more technical buildings, which contain radio transmitters and antenna fields, where up to several dozen antenna-feeder systems are located. The placement of the PRTs can be different, for example, in Moscow, placement in the immediate vicinity or among residential buildings is typical (for example, Oktyabrsky PRTs).
Radar stations have high power and are usually equipped with highly directional all-round antennas, which leads to a significant increase in the intensity of EMP in the microwave range and creates large areas with a high energy flux density on the ground. The most unfavorable conditions are noted in residential areas of cities within the boundaries of which airports are located - Irkutsk, Sochi, Rostov-on-Don, etc.
Currently, several million people in Russia use cellular communications. Cellular communication consists of a network of base stations and handheld personal radiotelephones. Base stations are located at a distance of 1 to 15 km from each other, forming the so-called "cells" between themselves by means of radio relay communication. They provide communication with personal radiotelephones at frequencies of 450, 800, 900 and 1800 MHz. The power of the transmitters is in the range from 2.5 to 320 watts (typically 40 watts).
Base station antennas are located at a height of 15-50 m from the Earth's surface, mainly on the roofs of buildings. When they are located on the roofs of public, administrative or residential buildings, the electromagnetic environment is monitored, but they are not considered as potential sources of danger, since the radiation of the side lobes of the base antennas is of little importance.
Handheld radiotelephones cellular communication have a power of 0.2 ... 7 watts. Output power is correlated with frequency: the higher the frequency, the lower the output power.
To reduce the consequences, it is recommended not to press the phone to your ear, or to apply it during a conversation to one or the other ear and talk continuously for no more than 2 ... 3 minutes. Some scientists propose to change the design of the radiotelephone so that the antenna is directed downward relative to the ear, and even better away from the speaker.
EMF sources in a wide frequency range are VDTs and personal computers. At the workplaces of computer users with monitors based on cathode ray tubes, fairly high levels of EMF are recorded, which indicates the danger of their biological action, and the distribution of fields is complex and uneven at different workplaces. The spectral characteristic of the field at the workplace of a computer user and a typical map of the electromagnetic environment are shown in fig. 7.2 - 7.4.
In industry, high-frequency electromagnetic radiation is used for induction and dielectric heating of materials (hardening, melting, metal deposition, heating of plastics, gluing plastics, heat treatment food products and etc.).
For example, near industrial generators for high-frequency hardening of metals, wood drying, etc. the electric field strength at workplaces can reach several hundred up to a thousand V / m, and the magnetic field strength - tens of A / m.
Rice. 7.2. Spectral characteristic of an alternating electric field at the user's workplace. Monitor CM-102, Taiwan
Rice. 7.3. An example of the distribution of an alternating electric field at the user's workplace
Rice. 7.4. Magnetic field lines around the display
Sources of constant magnetic fields at workplaces are: electromagnets and direct current solenoids, pulsed installations of half-wave and capacitor types, magnetic circuits in electrical machines and apparatuses, cast and ceramic-metal magnets used in radio engineering. Permanent magnets and electromagnets are widely used in instrumentation, in magnetic washers of cranes and other fixing devices, in devices for magnetic water treatment, nuclear magnetic resonance installations, etc. Powerful sources of a constant magnetic field are magnetohydrodynamic generators, the levels of magnetic fields of which at the location of the service personnel reach 50 mT. Average levels of permanent magnetic fields in working area operators in electrolytic processes are 5...10mTl. high levels(10... 100mT) are created in salons Vehicle on a magnetic pad.
Electrostatic fields arise when working with easily electrified materials and products, during the operation of high-voltage direct current installations. Static electric fields are widely used in industry for electrogas cleaning, electrostatic separation of ores and materials, electrostatic application of paint and varnish and polymeric materials, etc.
*11111* In technological processes, artificial EMF sources are widely used, operating in the following frequency ranges: f= 3-300 Hz - industrial frequency currents; f= 60 kHz-300 GHz - RF currents. At metallurgical plants, installations for induction metal processing are used, which allow: melting, hardening, annealing, welding metal. In addition, sources of EMF are automation equipment, transformers, capacitors, cathode ray tubes.
An effective remedy EMF protection is shielding. The choice of screen design depends on the wavelength range, the nature of the work performed, and the radiation source.
Protecting a person from the harmful effects of an electromagnetic field of industrial frequency
Currently, devices and electrical installations for various purposes that propagate electromagnetic fields are widely used in everyday life and in production. Among the various physical environmental factors that can have adverse effects on humans, the most dangerous is the electromagnetic field (EMF) of the industrial frequency of 50 Hz.
Sources of electromagnetic fields
The human senses do not perceive electromagnetic fields. A person cannot control the level of radiation and assess the impending danger, a kind of electromagnetic smog. Electromagnetic radiation propagates in all directions and, first of all, has an impact on the person working with the device-emitter, and on the environment (including other living organisms). It is known that a magnetic field arises around any object powered by electric current. An elementary source of EMF is an ordinary conductor through which an alternating current of any frequency passes, i.e. Almost any electrical appliance used by a person in everyday life is a source of EMF.
The electrical networks entangling the walls of our apartments can be clearly seen during their installation, even before the walls are plastered. This is, first of all, the wiring of networks to all sockets and switches, as well as cables and various types of extension cords for household appliances. Add to this also the cables that feed residential buildings from urban transformer substations, the distribution of electrical networks on the floors of the house to electricity meters and facilities automatic protection each apartment, the power supply system for elevators and lighting of corridors, entrances of houses, etc.
In daily activities in the conditions of the territory occupied by residential and public buildings, streets, public areas, a person is also exposed to industrial frequency EMF from various sources.
Overhead power lines (TL) have been laid through residential areas of cities. Overhead transmission lines with a voltage of 10, 35 and 110 kV, passing through residential areas, affect a small part of the inhabitants of cities and towns, but cause reasonable complaints from them even if the maximum permissible levels (MPL) of the electromagnetic field are not exceeded. Among other sources of electromagnetic fields of industrial frequency, open switchgear of transformer substations, urban electric transport (contact networks of trolleybuses and trams) and railway electric transport, as a rule, either close to residential buildings or cutting through settlements (villages, cities, etc.) . Of course, the walls of houses, especially those made of reinforced concrete panels, are screens and, thus, reduce the level of EMF, however, the impact of external EMF on a person cannot be ignored. Table 1 shows the average levels of the electromagnetic field in the open area and inside residential premises, which practically represents an average industrial area.
In addition to internal and external power networks, one should not forget also internal and local sources of EMF, as close as possible to a person. These include physiotherapy equipment in hospitals, household electrical consumers powered by electrical networks with an industrial frequency of 50 Hz.
Measurements of the strength of magnetic fields created by household electrical appliances have shown that their short-term effect is even stronger than a long-term stay of a person near power lines. The level of magnetic field strength at various distances from household appliances to a person, mGs, is given in Table 2.
The impact of EMF on the human body
The degree of biological influence of EMF on the human body depends on the frequency of oscillations, field strength and intensity.
The human body is a kind of vessel filled with liquid, the conductivity of which is explained by the presence of hemoglobin in it, which contains complex compounds of iron with protein in human blood. Thus, there are favorable conditions when an external alternating magnetic field can induce a current in the glandular protein of the human body and create the possibility of interaction of red blood cells with this field.
It is known that at a power of 10 mW/cm2 of the irradiated surface, human tissue can warm up by several tenths of a degree. And the intensity of absorption of electromagnetic energy in the human body depends on the frequency of radiation.
The action of EMF of especially high intensity (switchgear of substations and power lines of voltage 330 - 500 - 750 - 1500 kV) manifests itself in different ways. Being in the EMF, the human body is charged by any contact with the metal structure of the substation or power lines, which leads to a discharge pulse. It is established that the time of such an impulse is microseconds. The effect of this discharge resembles the sensation of an unpleasant unexpected prick. The consequence of this may be a weakening of the grasping ability of the fingers and hands in general, a loss, perhaps for some microseconds, of psychological orientation, etc., which can lead to injuries: a climber falling from the height of a support, bruising the workers standing below with a tool, dropped from the hands of a climber, etc.
In general, intense EMF of industrial frequency is caused in workers by:
Violation of the functional state of the central nervous, cardiovascular and endocrine systems;
Dizziness, sleep disturbance, increased drowsiness, lethargy, fatigue, decreased accuracy of movements;
Changes in blood pressure and pulse, the occurrence of pain in the heart, accompanied by headache and arrhythmia, etc.
violation of sexual function;
Deterioration of the development of the embryo;
All these changes in the human body are recorded during medical examinations (blood test, electrocardiography, etc.)
In recent years, information has appeared that the source of malignant neoplasms can be EMF of industrial frequency.
Protecting a person from EMF
To protect people from the harmful effects of EMF, regulations and standards are applied, which represent a kind of compromise between the benefits of using new technologies and new equipment and the possible risk caused by this application.
Permissible levels of non-ionizing radiation of various types and frequency ranges, etc.
The establishment of maximum permissible levels (MPL) is based on the principle of the threshold of the harmful effects of EMF on humans. As EMF maximum control levels, such levels are provided that, during systematic exposure in the operating mode for this particular source of EMF, do not cause diseases and deviations in the state of health in people (without sex and age restrictions). Table 3 shows the permissible levels of field strength from power transmission lines of industrial frequency.
However, not only the magnitude of the EMF intensity is important, but also the duration of a person's stay in the zone of action of this field. On the basis of research, the following standards have been developed for electric fields of industrial frequency, providing for limiting the time a person stays in the EMF source area (see Table 4)
With an EMF intensity of 5 kV / m, the work is not limited both in nature and in duration. At a voltage of more than 25 kV / m, and also if a longer duration of a person's stay in the EMF is required than given above, work must be carried out using protective equipment, for example, special clothing, the fabric of which has the properties of a screen. As fabrics, fabrics with conductive dye, fabrics containing flexible copper wire fibers, fabrics with threads of conductive polymer, etc. are used.
As preventive measures, it is envisaged to constantly monitor the electromagnetic environment by conducting electromagnetic monitoring, as well as predicting the development in general for the enterprise or organization of the electromagnetic environment.
The dimensions of the sanitary protection zones of power transmission lines, depending on their voltage class (f = 50 Hz), are given in Table 5.
The sanitary protection zone is understood as the so-called security zone, which has a conditional direction along the overhead power line and is measured from the projection of the extreme wires of the power transmission line on the ground.
It should be noted that the regulation of the size of the sanitary protection zone of the power transmission line is carried out at the voltage class of the power transmission line of 330 kV and higher in terms of the electrical component. However, according to the magnetic component of the electromagnetic field of the power transmission line, which is more dangerous than the electrical component, the dimensions of the sanitary protection zone can presumably be 200 ... 400 m. Research to establish the final dimensions of the protection zone in terms of the magnetic component should be continued.
Place residential buildings;
Provide parking and stops for all types of transport;
Arrange any sports and playgrounds;
Collect mushrooms, any fruits, berries and especially medicinal plants.
To control the electromagnetic situation in residential buildings or in office premises where a person is located, devices are used, consisting of an EMF intensity recorder (variable and electrostatic) of the RIEP - 50/20 type and a magnetic field intensity recorder RIMP 50 / 2.4, giving light and sound signals when the maximum remote control for this source.
It also provides for the protection of people from EMF exposure by the so-called method of distances from EMF sources, i.e. sanitary protection zone, the size of which depends on the intensity of the source (Table 4).
As for the methods of protecting a person in residential premises, some practical recommendations can be given in this regard.
Because in own apartment It is almost impossible to completely get rid of household electrical appliances, it is advisable to follow the following rules:
Do not install lighting fixtures (sconces, lamps with shades) above the bed, the light flow from which is directed downwards towards you - the light should only be directed upwards;
Do not install a TV, computer, or “base” of a radiotelephone in the bedroom, which is better to replace with a regular one;
Do not put an electronic clock (alarm clock) at the head of the bed;
Turn off the TV, music center, player and other sources of electromagnetic radiation from the network at night, which may be in standby mode, etc.
Refuse, if possible, from the systematic use of electric shavers;
Use irons with a bifilar winding of heating coils (such a winding does not have inductance).
conclusions
On the basis of domestic and foreign studies, the existence of links between some diseases of the population and the impact of electromagnetic radiation, in particular EMF, has been established.
Establishment of these relationships is the subject of further studies of the electromagnetic load, taking into account the statistical indicators of the health status of individual groups of the population, including taking into account the profession, age, gender, etc.
Literature
Dunaev V.N. Formation of electromagnetic load in urban environment//Sanitation and hygiene. - 2002. - No. 5. -p.31-34.
Emelyanov V. Measures to protect the population and territories in the conditions of electromagnetic pollution of the environment//Fundamentals of life safety. -2000. - No. 1. - P.58-61.
IN modern life of a person, almost any electrical device has its own radiation. The source (EMF) is a high-voltage line, TV and even a personal smartphone. All mankind lives in one big place, this is the Earth, which was originally permeated with natural waves of various spectrums.
common space
Scientists have established the level of natural wave background in which the body is accustomed to exist. The globe has two different poles, and every day we experience the influence of the radiation spectrum on ourselves. Changing under the influence of external factors, the electromagnetic field of a person is disturbed, which leads to health problems.
Researchers have long noticed that the largest wars in the world occurred after solar flares, when the natural magnetic background of the Earth was disturbed. Recently, this indicator is given in weather forecasts on television. In nature, there are special places with rocks. A person cannot be here for the following reason: the electromagnetic radiation and the electromagnetic field do not match.
Health impact
Electromagnetic radiation and electromagnetic field affect human health, therefore, acceptable indicators have been established. The negative effect of waves on the nervous system, the work of the brain and heart was noted. Animals and insects living in areas of high EMF show pathologies in the body structure.
According to studies, the influence of waves negatively affects the well-being of a person. Headache and fatigue are provoked, the work of internal organs is disrupted. The older generation can even pass out in a dangerous area: near high-voltage lines or a working electromagnet.
The source of the electromagnetic field is:
- Cellular, smartphones, Wi-Fi emitters, Appliances. Strong EMF occurs when the microwave oven is operating.
- Electric transport, conducting lines, industrial facilities.
- Radars, walkie-talkies, radiating installations.
- Scanners are medical, at the airports.
- Teleradio communication, UHF installations.
Norms
According to regulations, a sanitary zone should be organized next to powerful emitters. It is calculated according to the technical data of the object by a special commission. Standard values are specified in the documentation. So, when forming indicators, the mains voltage and the current flowing through the wires are taken into account.
Such a source of electromagnetic field is a high-voltage power line that feeds the whole city. The sanitary zone takes into account that the load on suitable wires varies with the time of day and year. The area of this site is dangerous for people, animals and plants. The maximum allowable limit, which is not dangerous for the body, is the flux density equal to 0.3 μT. Above this value, a healthy person may develop cancer and heart disease.
home appliances
Therefore, the instructions for the microwave oven indicate: it is not recommended to be directly in front of the front panel while heating food. Prolonged stay of pregnant women in the zone of increased electromagnetic field can lead to miscarriages. Scientists have proven that cellular telephone affects a person's well-being. It is better not to leave it at night near the head and not to carry it in pockets near the heart.
On the street
The source of the electromagnetic field is a power line, electric transport: trams, trolleybuses. Therefore, when choosing suburban area experienced people try to stay away from power lines of broadcasting stations, cellular repeaters, electrical substations. In case of suspicion of exceeding allowable norms radiation can be checked with an instrument. The culprit will be obliged to eliminate the negative factor.
Another powerful emitter is Railway. Near it, there will definitely be inflated indicators. However, there is no getting away from them, this is a price for the convenience of the citizens' movement.
Fighting methods
One of the main ways to exclude the influence of EMF on a person is the spatial separation of radiating objects. High-voltage lines are laid high above natural landscapes so as not to harm plants and animals. Near such structures it is forbidden to build residential buildings, grow crops, and graze livestock.
Shielding of emitting objects is common in the city. The energy of the electromagnetic field does not penetrate through grounded metal shells. If a person is isolated from the Earth's field for a long time, he will have a strong weakness or, conversely, aggression. A similar state of health is manifested in sailors or submariners after a long voyage.
Wave Treatment
With the right radiation, the opposite effect can be observed. It is used in medicine to restore body functions. The source of the electromagnetic field is which the patient applies to the sore spot. Long-term therapy relieves chronic ailments of the joints, blood vessels, heart.
EMF is used to relieve pain, improve blood circulation, and thanks to it, fatigue quickly disappears. The therapeutic effect is formed due to the ionization of the metal components of the blood. A person feels the warming effect of radiation. Periodic use of medical devices negates the recurrence of chronic diseases.
The electromagnetic field has a positive effect on the immune system, removes swelling. There is a rapid regeneration of cells after injury. However, magnetotherapy can Negative influence in the presence of pacemakers or when a person has blood diseases. The doctor should prescribe such treatment based on the results of the examination.
What else is forbidden to place in negative zones?
Sanitary zone near strong sources of electromagnetic field is established supervisory authorities. In this place, all objects are placed only after agreement with them. The ban applies to premises and areas reserved for the storage of fuels and lubricants. It is impossible to build oil depots, gas stations, parking lots for any type of transport, except for electric.
Also, people should not be in the area. It is forbidden to place stops, markets, arrange meetings. If it is necessary to organize such places, shielding of the source is used. On rooftops where there are transmitting stations, you can often see a metal mesh around the antenna. This is how they achieve a narrowing of the sanitary zone.
Similar measures are taken to protect residential and industrial buildings from conventional and ball lightning. A metal antenna is installed on the roof, grounded deep into the ground. An accumulation of positive potential is formed around the building, and the electrons go through an artificial circuit. When placing a new device in your home, it is better to take care in advance about the place of its installation away from the sleeping area.
Chantilly Castle - the second in France after Versailles Chantilly Castle how to get from Paris
Amusement park "The Land of Legends Theme Park" in Turkey
Holy places in Greece. Greece Orthodox. Pilgrimage to the feast of St. Nicholas
Picodi: All discounts in one place!
How to get to Dolmabahce Palace