Strong sources of electromagnetic fields are currents of frequency. Main sources of emp

1. What is EMF, its types and classification
2. Main sources of EMF
2.1 Electric transport
2.2 Power lines
2.3 Electrical wiring
2.4 Household electrical appliances
2.5 TV and radio stations
2.6 Satellite communications
2.7 Cellular
2.8 Radars
2.9 Personal computers
3. How does EMF affect health?
4. How to protect yourself from EMF

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.

An electric field is created by charges. For example, in all the well-known school experiments on the electrification of ebonite, an electric field is present.

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, symbol E, unit of measurement V/m (Volts-per-meter). The magnitude of the magnetic field is characterized by the magnetic field strength H, unit A/m (Ampere-per-meter). When measuring ultra-low and extremely low frequencies, the concept of magnetic induction B is also often used, the unit T (Tesla), one millionth of a T corresponds to 1.25 A/m.

By definition, an electromagnetic field is a special form of matter through which interaction occurs 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, without disappearing when the source is removed (for example, radio waves do not disappear even in the absence of current in the antenna that emitted them).

Electromagnetic waves are characterized by wavelength, symbol - l (lambda). A source that generates radiation, and essentially creates electromagnetic oscillations, is characterized by frequency, designated f.

An important feature of 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 3l. In the “far” zone, the field intensity decreases in inverse proportion to the distance to the source r -1.

In the “far” zone of radiation there is a connection between E and H: E = 377H, where 377 is the wave impedance of the vacuum, 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. Denoted as S, the unit of measurement is W/m2. PES characterizes the amount of energy transferred by an electromagnetic wave per unit time through a unit surface perpendicular to the direction of propagation of the wave.

International classification of electromagnetic waves by frequency

Frequency range name	Range limits	Name of wave range	Range limits
Extreme low, ELF	3 - 30 Hz	Decamegameter	100 - 10 mm
Ultra-low, SLF	30 – 300 Hz	Megameter	10 - 1 mm
Infra-low, INF	0.3 - 3 kHz	Hectokilometer	1000 - 100 km
Very low, VLF	3 - 30 kHz	Myriameter	100 - 10 km
Low frequencies, LF	30 - 300 kHz	Kilometer	10 - 1 km
Mids, mids	0.3 - 3 MHz	Hectometric	1 - 0.1 km
Treble, HF	3 - 30 MHz	Decameter	100 - 10 m
Very high, VHF	30 - 300 MHz	Meter	10 - 1 m
Ultra high, UHF	0.3 - 3 GHz	decimeter	1 - 0.1 m
Ultra high, microwave	3 - 30 GHz	Centimeter	10 - 1 cm
Extremely high, EHF	30 - 300 GHz	Millimeter	10 - 1 mm
Hyperhigh, HHF	300 – 3000 GHz	decimmillimeter	1 - 0.1 mm

2. Main sources of EMF

Among the main sources of EMR are:

• Electric transport (trams, trolleybuses, trains,...)
• Power lines (city lighting, high voltage,...)
• Electrical wiring (inside buildings, telecommunications,…)
• Household electrical appliances
• TV and radio stations (broadcasting antennas)
• Satellite and cellular communications (broadcast antennas)
• Radars
• Personal computers

2.1 Electric transport

Electric vehicles - electric trains (including subway trains), trolleybuses, trams, etc. - are a relatively powerful source of magnetic field in the frequency range from 0 to 1000 Hz. According to (Stenzel et al., 1996), the maximum values ​​of the magnetic induction flux density B in commuter trains reach 75 μT with an average value of 20 μT. The average value of V for vehicles with a DC electric drive was recorded 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 over which these fields extend from the line wires reaches tens of meters. The range of propagation of the electric field depends on the voltage class of the power line (the number indicating the voltage class is in the name of the power line - for example, a 220 kV power line), the higher the voltage, the larger the zone of increased electric field level, while the size of the zone does not change during the operation of the power line.

The range of propagation of the magnetic field depends on the magnitude of the current flowing or on the line load. Since the load on power lines can change repeatedly both during the day and with changing seasons, the size of the zone of increased magnetic field level also changes.

Biological effect

Electric and magnetic fields are very strong factors influencing the state of all biological objects falling within the zone of their influence. For example, in the area of ​​influence of the electric field of power lines, insects exhibit changes in behavior: for example, bees show increased aggressiveness, anxiety, decreased performance and productivity, and a tendency to lose queens; Beetles, mosquitoes, butterflies and other flying insects exhibit changes in behavioral responses, including a change in the direction of movement towards a lower field level.

Developmental anomalies are common in plants - the shapes and sizes of flowers, leaves, stems often change, and 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 work of English scientists in the early 90s is well known, showing that a number of allergy sufferers, when exposed to the power line field, develop an epileptic-type reaction. With prolonged 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 recent years, cancer has often been cited as a long-term consequence.

Sanitary standards

Studies of the biological effect of EMF IF, carried out in the USSR in the 60-70s, were focused mainly on the effect of the electrical component, since no significant biological effect of the magnetic component was experimentally discovered at typical levels. In the 70s, strict standards were introduced for the population according to EP, which are still among the most stringent in the world. They are set out in the Sanitary Norms and Rules “Protection of the population from the effects of the 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 throughout the world is now considered the most dangerous to health, the maximum permissible magnetic field value for the population in Russia is not standardized. The reason is there is no money for research and development of standards. Most power lines were built without taking this danger into account.

Based on mass epidemiological surveys of the population living in conditions of irradiation by magnetic fields of power lines, a magnetic induction flux density of 0.2 - 0.3 µT.

Principles for ensuring public safety

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 sanitary protection zones for power transmission lines on existing lines are determined by the criterion of electric field strength - 1 kV/m.

Boundaries of sanitary protection zones for power lines according to SN No. 2971-84

The placement of ultra-high voltage overhead lines (750 and 1150 kV) is subject to additional requirements regarding the conditions of exposure to the electric field on the population. Thus, the closest distance from the axis of the designed 750 and 1150 kV overhead lines to the boundaries of populated areas 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 your local energy company, but you can try visually, although this 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, can only be determined approximately by the number of insulators in the 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

MPL, kV/m	Irradiation conditions
0,5	inside residential buildings
1,0	on the territory of a residential development zone
5,0	in populated areas outside of residential areas; (land of cities within the city limits within the boundaries of their long-term development for 10 years, suburban and green areas, resorts, lands of urban-type settlements within the village limits and rural settlements within the boundaries of these points) as well as in the territory of vegetable gardens and orchards;
10,0	at the intersections of overhead power lines with highways of categories 1–IV;
15,0	in uninhabited areas (undeveloped areas, even if frequently visited by people, accessible to transport, and agricultural land);
20,0	in hard-to-reach areas (inaccessible to transport and agricultural vehicles) and in areas specially fenced off to exclude public access.

Within the sanitary protection zone of overhead lines it is prohibited:

• place residential and public buildings and structures;
• arrange parking areas for all types of transport;
• locate automobile servicing enterprises and oil and petroleum products warehouses;
• carry out operations with fuel, repair machines and mechanisms.

The 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.

If in some areas the electric field strength outside the sanitary protection zone is higher than the maximum permissible 0.5 kV/m inside the building and higher than 1 kV/m in the residential area (in places where people may be present), they must measures should be taken to reduce tensions. To do this, on the roof of a building with a non-metal roof, almost any metal mesh is placed, grounded in at least two points. In buildings with a metal roof, it is enough to ground the roof in at least two points. In personal plots or other places where people are located, 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.

2.3 Electrical wiring

The greatest contribution to the electromagnetic environment of residential premises in the industrial frequency range of 50 Hz comes from the electrical equipment of the building, namely the cable lines supplying electricity to all apartments and other consumers of the building’s life support system, as well as distribution boards and transformers. In rooms adjacent to these sources, the level of the industrial frequency magnetic field, caused by the flowing electric current, is usually increased. The level of the electric field at industrial frequency is usually not high and does not exceed the maximum permissible limit for the population of 500 V/m.

The figure shows the distribution of the magnetic field of industrial frequency in a residential area. The source of the field is a power distribution point located in an adjacent non-residential building. At present, the results of the studies performed cannot clearly justify the limit values ​​or other mandatory restrictions for long-term exposure of the population to low-frequency magnetic fields at low levels.

Researchers from Carnegie University in Pittsburgh (USA) have formulated an approach to the problem of the magnetic field which they call “prudent prevention”. They believe that while our knowledge regarding the relationship between health and the consequences of radiation exposure remains incomplete, but there are strong suspicions about the health consequences, it is necessary to take steps to ensure safety that do not incur heavy costs or other inconveniences.

A similar approach was used, for example, in the initial stage of work on the problem of the biological effects of ionizing radiation: suspicion of risks of damage to health, based on solid scientific grounds, should in itself constitute sufficient grounds for taking protective measures.

Currently, many experts consider the maximum permissible value of magnetic induction to be 0.2 - 0.3 µT. It is believed that the development of diseases - primarily leukemia - is very likely with prolonged exposure of a person to fields of higher levels (several hours a day, especially at night, for a period of more than a year).

The main protective measure is precautionary.

• it is necessary to avoid prolonged stay (regularly for several hours a day) in places with an increased level of industrial frequency magnetic field;
• the bed for night rest should be kept as far as possible from sources of prolonged exposure; the distance to distribution cabinets and power cables should be 2.5 - 3 meters;
• if there are any unknown cables, distribution cabinets, transformer substations in or adjacent to the room, removal should be as much as possible; optimally, measure the level of electromagnetic fields before living in such a room;
• If it is necessary to install electrically heated floors, choose systems with a reduced level of magnetic field.

2.4 Household electrical appliances

All household appliances that operate using electric current are sources of electromagnetic fields. The most powerful are microwave ovens, convection ovens, refrigerators with a “no frost” system, kitchen hoods, electric stoves, and televisions. The actual EMF generated, depending on the specific model and mode of operation, can vary greatly among equipment of the same type (see Figure 1). All data below refers to a magnetic field of industrial frequency 50 Hz.

The magnetic field values ​​are closely related to the power of the device - the higher it is, the higher the magnetic field during its operation. The values ​​of the electric field of industrial frequency of almost all electrical household appliances do not exceed several tens of V/m at a distance of 0.5 m, which is significantly less than the maximum limit of 500 V/m.

Power frequency magnetic field levels of household electrical appliances at a distance of 0.3 m.

Maximum permissible electromagnetic field levels for consumer products that are sources of EMF

Source	Range	Remote control value	Note
Induction furnaces	20 - 22 kHz	500 V/m 4 A/m	Measurement conditions: distance 0.3 m from the body
Microwave ovens	2.45 GHz	10 µW/cm2	Measurement conditions: distance 0.50 ± 0.05 m from any point, with a load of 1 liter of water
PC video display terminal	5 Hz - 2 kHz	Epdu = 25 V/m Vpdu = 250 nT	Measurement conditions: distance 0.5 m around the PC monitor
	2 - 400 kHz	Epdu = 2.5 V/mV pdu = 25 nT
	surface electrostatic potential	V = 500 V	Measurement conditions: distance 0.1 m from the PC monitor screen
Other products	50 Hz	E = 500 V/m	Measurement conditions: distance 0.5 m from the product body
	0.3 - 300 kHz	E = 25 V/m
	0.3 - 3 MHz	E = 15 V/m
	3 - 30 MHz	E = 10 V/m
	30 - 300 MHz	E = 3 V/m
	0.3 - 30 GHz	PES = 10 μW/cm2

Possible biological effects

The human body always reacts to the electromagnetic field. However, in order for this reaction to develop into a pathology and lead to disease, a number of conditions must coincide - including a sufficiently high field level and duration of irradiation. Therefore, when using household appliances with low field levels and/or for a short period of time, the EMF of household appliances does not affect the health of the majority of the population. Potential danger can only be faced by people with hypersensitivity to EMFs and allergy sufferers, who also often have increased sensitivity to EMFs.

In addition, according to modern concepts, a magnetic field of industrial frequency can be dangerous to human health if prolonged exposure occurs (regularly, at least 8 hours a day, for several years) with a level above 0.2 microtesla.

• When purchasing household appliances, check in the Hygienic Report (certificate) the mark on the product’s compliance with the requirements of the “Interstate Sanitary Standards for Permissible Levels of Physical Factors when Using Consumer Goods in Domestic Conditions”, MSanPiN 001-96;
• use equipment with lower power consumption: industrial frequency magnetic fields will be lower, all other things being equal;
• Potentially unfavorable sources of a magnetic field of industrial frequency in an apartment include refrigerators with a “no-frost” system, some types of “warm floors”, heaters, televisions, some alarm systems, various types of chargers, rectifiers and current converters - the sleeping place should be at a distance at least 2 meters from these objects if they work during your night rest;
• When placing household appliances in an apartment, be guided by the following principles: place household electrical appliances as far as possible from rest areas, do not place household electrical appliances close together and do not stack them on top of each other.

A microwave oven (or microwave oven) uses an electromagnetic field, also called microwave radiation or microwave radiation, to heat food. The operating frequency of microwave radiation of microwave ovens is 2.45 GHz. It is this radiation that many people are afraid of. However, modern microwave ovens are equipped with fairly advanced protection that prevents the electromagnetic field from escaping beyond the working volume. At the same time, it cannot be said that the field does not penetrate at all outside the microwave oven. For various reasons, part of the electromagnetic field intended for the chicken penetrates outward, especially intensely, usually in the area of ​​the lower right corner of the door. To ensure safety when using ovens at home, Russia has sanitary standards that limit the maximum leakage of microwave radiation from a microwave oven. They are called “Maximum permissible levels of energy flux density created by microwave ovens” and have the designation SN No. 2666-83. According to these sanitary standards, the energy flux density of the electromagnetic field should not exceed 10 μW/cm2 at a distance of 50 cm from any point of the stove body when heating 1 liter of water. In practice, almost all new modern microwave ovens meet this requirement with a large margin. However, when purchasing a new stove, you need to make sure that the certificate of conformity states that your stove meets the requirements of these sanitary standards.

It must be remembered that over time the degree of protection may decrease, mainly due to the appearance of microcracks in the door seal. This can happen both due to dirt and mechanical damage. Therefore, the door and its seal require careful handling and careful maintenance. The guaranteed durability of protection against electromagnetic field leaks during normal operation is several years. After 5-6 years of operation, it is advisable to check the quality of protection and invite a specialist from a specially accredited laboratory for monitoring electromagnetic fields.

In addition to microwave radiation, the operation of a microwave oven is accompanied by an intense magnetic field created by an industrial frequency current of 50 Hz flowing in the oven's power supply system. At the same time, a microwave oven is one of the most powerful sources of a magnetic field in an apartment. For the population, the level of the industrial frequency magnetic field in our country is still not limited, despite its significant effect on the human body during prolonged exposure. In domestic conditions, a single short-term switching on (for a few minutes) will not have a significant impact on human health. However, now a household microwave oven is often used to heat food in cafes and similar other industrial settings. In this case, a person working with it finds himself in a situation of chronic exposure to a magnetic field of industrial frequency. In this case, mandatory control of the industrial frequency magnetic field and microwave radiation is necessary at the workplace.

Considering the specifics of the microwave oven, it is advisable to move away at a distance of at least 1.5 meters after turning it on - in this case, the electromagnetic field is guaranteed not to affect you at all.

2.5 TV and radio stations

A significant number of transmitting radio centers of various affiliations are currently located on the territory of Russia. Transmitting radio centers (RTC) are located in specially designated areas and can occupy fairly large areas (up to 1000 hectares). In their structure, they include one or more technical buildings where radio transmitters are located, and antenna fields on which up to several dozen antenna-feeder systems (AFS) are located. The AFS includes an antenna used to measure radio waves and a feed line that supplies high-frequency energy generated by the transmitter to it.

The zone of possible adverse effects of EMFs created by the PRC can be divided into two parts.

The first part of the zone is the PRC territory itself, where all the services that ensure the operation of radio transmitters and AFS are located. This territory is guarded and only persons professionally associated with the maintenance of transmitters, switches and AFS are allowed into it. The second part of the zone is the territories adjacent to the PRC, access to which is not limited and where various residential buildings can be located, in this case there is a threat of exposure to the population located in this part of the zone.

The location of the RRC can be different, for example, in Moscow and the Moscow region it is typically located in close proximity or among residential buildings.

High levels of EMF are observed in areas, and often outside the location of transmitting radio centers of low, medium and high frequencies (PRC LF, MF and HF). A detailed analysis of the electromagnetic situation in the territories of the PRC indicates its extreme complexity associated with the individual nature of the intensity and distribution of EMF for each radio center. In this regard, special studies of this kind are carried out for each individual PRC.

Widespread sources of EMF in populated areas are currently radio engineering transmitting centers (RTTCs), emitting ultrashort VHF and UHF waves into the environment.

A comparative analysis of sanitary protection zones (SPZ) and restricted development zones in the coverage area of ​​such facilities showed that the highest levels of exposure to people and the environment are observed in the area where the RTPC is located “old” with an antenna support height of no more than 180 m. The largest contribution to the total The intensity of the impact is contributed by the “corner” three- and six-story VHF FM broadcasting antennas.

DV radio stations(frequencies 30 - 300 kHz). In this range, the wavelengths are relatively long (for example, 2000 m for a frequency of 150 kHz). At a distance of one wavelength or less from the antenna, the field can be quite large, for example, at a distance of 30 m from the antenna of a 500 kW transmitter operating at 145 kHz, the electric field can be above 630 V/m and the magnetic field above 1. 2 A/m.

CB radio stations(frequencies 300 kHz - 3 MHz). Data for radio stations of this type say that the electric field strength at a distance of 200 m can reach 10 V/m, at a distance of 100 m - 25 V/m, at a distance of 30 m - 275 V/m (data are given for a 50 kW transmitter) .

HF radio stations(frequencies 3 - 30 MHz). HF radio transmitters usually have lower power. However, they are more often located in cities, and can even be placed on the roofs of residential buildings at a height of 10-100 m. A 100 kW transmitter at a distance of 100 m can create an electric field strength of 44 V/m and a magnetic field of 0.12 F/m.

TV transmitters. Television transmitters are usually located in cities. Transmitting antennas are usually located at altitudes above 110 m. From the point of view of assessing the impact on health, field levels at distances from several tens of meters to several kilometers are of interest. Typical electric field strengths can reach 15 V/m at a distance of 1 km from a 1 MW transmitter. In Russia, at present, the problem of assessing the level of EMF of television transmitters is especially relevant due to the sharp increase in the number of television channels and transmitting stations.

The main principle of ensuring safety is compliance with the maximum permissible levels of the electromagnetic field established by Sanitary norms and rules. Each radio transmitting facility has a Sanitary Passport, which defines the boundaries of the sanitary protection zone. Only with this document do the territorial bodies of the State Sanitary and Epidemiological Supervision permit the operation of radio transmitting facilities. They periodically monitor the electromagnetic environment to ensure it complies with the established remote controls.

2.6 Satellite communications

Satellite communication systems consist of a transceiver station on Earth and a satellite in orbit. The antenna pattern of satellite communication stations has a clearly defined narrowly directed main beam - the main lobe. The energy flux density (PED) in the main lobe of the radiation pattern can reach several hundred W/m2 near the antenna, also creating significant field levels at a large distance. For example, a 225 kW station operating at a frequency of 2.38 GHz creates a PES equal to 2.8 W/m2 at a distance of 100 km. However, energy dissipation from the main beam is very small and occurs most in the area where the antenna is located.

2.7 Cellular

Cellular radiotelephony is one of the most rapidly developing telecommunication systems today. Currently, around the world there are more than 85 million subscribers using the services of this type of mobile (mobile) communications (in Russia - more than 600 thousand). It is expected that by 2001 their number will increase to 200–210 million (in Russia - about 1 million).

The main elements of a cellular communication system are base stations (BS) and mobile radiotelephones (MRT). Base stations maintain radio communication with mobile radiotelephones, as a result of which BS and MRI are sources of electromagnetic radiation in the UHF range. An important feature of the cellular radio communication system is the very efficient use of the radio frequency spectrum allocated for the system’s operation (repeated use of the same frequencies, use of different access methods), which makes it possible to provide telephone communications to a significant number of subscribers. The system operates on the principle of dividing a certain territory into zones, or “cells,” with a radius of usually 0.5–10 kilometers.

Base stations

Base stations maintain communication with mobile radiotelephones located in their coverage area and operate in signal reception and transmission modes. Depending on the standard, BS emit electromagnetic energy in the frequency range from 463 to 1880 MHz. BS antennas are installed at a height of 15–100 meters from the ground surface on existing buildings (public, service, industrial and residential buildings, chimneys of industrial enterprises, etc.) or on specially constructed masts. Among the BS antennas installed in one place, there are both transmitting (or transceiver) and receiving antennas, which are not sources of EMF.

Based on the technological requirements for building a cellular communication system, the antenna radiation pattern in the vertical plane is designed in such a way that the main radiation energy (more than 90%) is concentrated in a rather narrow “beam”. It is always directed away from the structures on which the BS antennas are located, and above adjacent buildings, which is a necessary condition for the normal functioning of the system.

Brief technical characteristics of cellular radio communication system standards operating in Russia

Name of the standard Operating frequency range of BS Operating frequency range of MRI Maximum radiated power of BS Maximum radiated power of MRI Cell radius
NMT-450 Analog 463 – 467.5 MHz 453 – 457.5 MHz 100 W 1 W 1 – 40 km
AMPS Analog 869 – 894 MHz 824 – 849 MHz 100 W 0.6 W 2 – 20 km
D-AMPS (IS-136) Digital 869 – 894 MHz 824 – 849 MHz 50 W 0.2 W 0.5 – 20 km
CDMADigital 869 – 894 MHz 824 – 849 MHz 100 W 0.6 W 2 – 40 km
GSM-900Digital 925 – 965 MHz 890 – 915 MHz 40 W 0.25 W 0.5 – 35 km
GSM-1800 (DCS) Digital 1805 – 1880 MHz 1710 – 1785 MHz 20 W 0.125 W 0.5 – 35 km

BS are a type of transmitting radio engineering objects, the radiation power of which (load) is not constant 24 hours a day. The load is determined by the presence of cell phone owners in the service area of ​​a particular base station and their desire to use the phone for a conversation, which, in turn, fundamentally depends on the time of day, location of the BS, day of the week, etc. At night, the load of the BS is almost zero , i.e. the stations are mostly “silent”.

Studies of the electromagnetic situation in the territory adjacent to the BS were carried out by specialists from different countries, including Sweden, Hungary and Russia. Based on the results of measurements carried out in Moscow and the Moscow region, it can be stated that in 100% of cases the electromagnetic environment in the premises of buildings on which BS antennas are installed did not differ from the background characteristic of a given area in a given frequency range. In the adjacent territory, in 91% of cases, the recorded levels of the electromagnetic field were 50 times less than the maximum limit established for the BS. The maximum measurement value, 10 times less than the maximum limit, was recorded near a building on which three base stations of different standards were installed at once.

Available scientific data and the existing system of sanitary and hygienic control during the commissioning of cellular base stations make it possible to classify cellular base stations as the most environmentally and sanitary and hygienically safe communication systems.

Mobile radiotelephones

A mobile radiotelephone (MRT) is a small-sized transceiver. Depending on the phone standard, transmission is carried out in the frequency range 453 – 1785 MHz. The MRI radiation power is a variable value that largely depends on the state of the communication channel “mobile radiotelephone – base station,” i.e., the higher the BS signal level at the receiving location, the lower the MRI radiation power. The maximum power is in the range of 0.125–1 W, but in real conditions it usually does not exceed 0.05–0.2 W. The question of the impact of MRI radiation on the user’s body still remains open. Numerous studies conducted by scientists from different countries, including Russia, on biological objects (including volunteers) have led to ambiguous, sometimes contradictory, results. The only undeniable fact is that the human body “responds” to the presence of cell phone radiation. Therefore, MRI owners are advised to take some precautions:

• do not use your cell phone unless necessary;
• talk continuously for no more than 3 – 4 minutes;
• Do not allow children to use MRI;
• when purchasing, choose a cell phone with a lower maximum radiation power;
• In a car, use MRI in conjunction with a hands-free communication system with an external antenna, which is best located in the geometric center of the roof.

For people surrounding a person talking on a mobile radiotelephone, the electromagnetic field created by MRI does not pose any danger.

Research into the possible influence of the biological effect of the electromagnetic field of elements of cellular communication systems is of great interest to the public. Publications in the media fairly accurately reflect current trends in these studies. GSM mobile phones: Swiss tests have shown that the radiation absorbed by the human head is within the limits permitted by European standards. Specialists from the Center for Electromagnetic Safety conducted medical and biological experiments to study the influence of electromagnetic radiation from mobile phones of existing and future cellular communication standards on the physiological and hormonal state of a person.

When a mobile phone is operating, electromagnetic radiation is perceived not only by the base station receiver, but also by the user’s body, and primarily by his head. What happens in the human body, and how dangerous is this effect to health? There is still no clear answer to this question. However, an experiment by Russian scientists showed that the human brain not only senses cell phone radiation, but also distinguishes between cellular communication standards.

The head of the research project, Doctor of Medical Sciences Yuri Grigoriev, believes that cell phones of the NMT-450 and GSM-900 standards caused reliable and noteworthy changes in the bioelectrical activity of the brain. However, a single 30-minute exposure to the electromagnetic field of a mobile phone does not have clinically significant consequences for the human body. The lack of reliable measurements in the electroencephalogram in the case of using a GSM-1800 standard telephone can characterize it as the most “friendly” for the user of the three communication systems used in the experiment.

2.8 Radars

Radar stations are usually equipped with mirror-type antennas and have a narrowly directed radiation pattern in the form of a beam directed along the optical axis.

Radar systems operate at frequencies from 500 MHz to 15 GHz, but individual systems can operate at frequencies up to 100 GHz. The EM signal they create is fundamentally different from radiation from other sources. This is due to the fact that periodic movement of the antenna in space leads to spatial intermittency of irradiation. Temporary intermittency of irradiation is due to the cyclical operation of the radar on radiation. The operating time in various operating modes of radio equipment can range from several hours to a day. Thus, for meteorological radars with a time intermittency of 30 minutes - radiation, 30 minutes - pause, the total operating time does not exceed 12 hours, while airport radar stations in most cases operate around the clock. The width of the radiation pattern in the horizontal plane is usually several degrees, and the duration of irradiation over the viewing period is tens of milliseconds.

Metrological radars can create a PES of ~100 W/m2 for each irradiation cycle at a distance of 1 km. Airport radar stations create PES ~ 0.5 W/m2 at a distance of 60 m. Marine radar equipment is installed on all ships; it usually has a transmitter power an order of magnitude lower than that of airfield radars, so in normal mode scanning PES created at a distance of several meters, does not exceed 10 W/m2.

An increase in the power of radars for various purposes and the use of highly directional all-round antennas leads to a significant increase in the intensity of EMR in the microwave range and creates long-distance zones with a high energy flux density on the ground. The most unfavorable conditions are observed in residential areas of cities within which airports are located: Irkutsk, Sochi, Syktyvkar, Rostov-on-Don and a number of others.

2.9 Personal computers

The main source of adverse effects on the health of a computer user is the means of visual display of information on a cathode ray tube. The main factors of its adverse effects are listed below.

Ergonomic parameters of the monitor screen

• reduced image contrast in conditions of intense external illumination
• specular reflections from the front surface of monitor screens
• flickering of the image on the monitor screen

Emissive characteristics of the monitor

• electromagnetic field of the monitor in the frequency range 20 Hz-1000 MHz
• static electric charge on the monitor screen
• ultraviolet radiation in the range 200-400 nm
• infrared radiation in the range 1050 nm - 1 mm
• X-ray radiation > 1.2 keV

Computer as a source of alternating electromagnetic field

The main components of a personal computer (PC) are: a system unit (processor) and various input/output devices: keyboard, disk drives, printer, scanner, etc. Each personal computer includes a means of visual display of information called differently - monitor, display. As a rule, it is based on a device based on a cathode ray tube. PCs are often equipped with surge protectors (for example, "Pilot" type), uninterruptible power supplies and other auxiliary electrical equipment. All these elements during PC operation form a complex electromagnetic environment at the user’s workplace (see Table 1).

PC as a source of EMF

Source Frequency range(first harmonic)
Monitor network transformer power supply 50 Hz
static voltage converter in switching power supply 20 - 100 kHz
frame scanning and synchronization unit 48 - 160 Hz
line scanning and synchronization unit 15 110 kHz
monitor anode accelerating voltage (only for CRT monitors) 0 Hz (electrostatic)
System unit (processor) 50 Hz - 1000 MHz
Information input/output devices 0 Hz, 50 Hz
Uninterruptible power supplies 50 Hz, 20 - 100 kHz

The electromagnetic field created by a personal computer has a complex spectral composition in the frequency range from 0 Hz to 1000 MHz. The electromagnetic field has electric (E) and magnetic (H) components, and their relationship is quite complex, so E and H are assessed separately.

Maximum EMF values ​​recorded at the workplace
Field type, frequency range, field strength unit Field strength value along the screen axis around the monitor
Electric field, 100 kHz - 300 MHz, V/m 17.0 24.0
Electric field, 0.02-2 kHz, V/m 150.0 155.0
Electric field, 2-400 kHz V/m 14.0 16.0
Magnetic field, 100 kHz - 300 MHz, mA/m nhp nhp
Magnetic field, 0.02-2 kHz, mA/m 550.0 600.0
Magnetic field, 2-400 kHz, mA/m 35.0 35.0
Electrostatic field, kV/m 22.0 -

Range of electromagnetic field values ​​measured at PC user workplaces

Name of measured parameters Frequency range 5 Hz - 2 kHz Frequency range 2 - 400 kHz
Alternating electric field strength, (V/m) 1.0 - 35.0 0.1 - 1.1
Alternating magnetic field induction, (nT) 6.0 - 770.0 1.0 - 32.0

Computer as a source of electrostatic field

When the monitor is operating, an electrostatic charge accumulates on the kinescope screen, creating an electrostatic field (ESF). In different studies, under different measurement conditions, EST values ​​ranged from 8 to 75 kV/m. At the same time, people working with the monitor acquire electrostatic potential. The spread of electrostatic potentials of users ranges from -3 to +5 kV. When ESTP is experienced subjectively, the user's potential is the deciding factor in the occurrence of unpleasant subjective sensations. A noticeable contribution to the total electrostatic field is made by the surfaces of the keyboard and mouse, which are electrified by friction. Experiments show that even after working with the keyboard, the electrostatic field quickly increases from 2 to 12 kV/m. At individual workplaces in the area of ​​the hands, static electric field strengths of more than 20 kV/m were recorded.

According to generalized data, in those working at a monitor from 2 to 6 hours a day, functional disorders of the central nervous system occur on average 4.6 times more often than in control groups, diseases of the cardiovascular system - 2 times more often, diseases of the upper respiratory tract - 1.9 times more often, diseases of the musculoskeletal system - 3.1 times more often. As the time spent on a computer increases, the ratio of healthy to sick users increases sharply.

Studies of the functional state of a computer user, conducted in 1996 at the Center for Electromagnetic Safety, showed that even with short-term work (45 minutes), significant changes in the hormonal state and specific changes in the biocurrents of the brain occur in the user’s body under the influence of electromagnetic radiation from the monitor. These effects are especially pronounced and persistent in women. It was noticed that in groups of people (in this case it was 20%), a negative reaction of the functional state of the body does not manifest itself when working with a PC for less than 1 hour. Based on the analysis of the results obtained, it was concluded that it is possible to form special professional selection criteria for personnel using a computer in the process of work.

Influence of air ion composition. The areas that perceive air ions in the human body are the respiratory tract and skin. There is no consensus regarding the mechanism of influence of air ions on human health.

Effect on vision. The visual fatigue of the VDT user includes a whole range of symptoms: the appearance of a “veil” before the eyes, the eyes become tired, become painful, headaches appear, sleep is disturbed, and the psychophysical state of the body changes. It should be noted that vision complaints can be associated both with the above-mentioned VDT factors and with lighting conditions, the operator’s state of vision, etc. Long-term statistical load syndrome (LTSS). Display users develop muscle weakness and changes in the shape of the spine. In the USA, it is recognized that DSHF is the occupational disease with the highest rate of spread in 1990-1991. In a forced working position, with static muscle load, the muscles of the legs, shoulders, neck and arms remain in a state of contraction for a long time. Since the muscles do not relax, their blood supply deteriorates; Metabolism is disrupted, biodegradation products and, in particular, lactic acid accumulate. In 29 women with prolonged static load syndrome, a biopsy of muscle tissue was taken, in which a sharp deviation of biochemical parameters from the norm was discovered.

Stress. Display users are often under stress. According to the US National Institute for Occupational Safety and Health (1990), VDT users are more susceptible to developing stress conditions than other occupational groups, including air traffic controllers. At the same time, for most users, working on VDTs is accompanied by significant mental stress. It has been shown that sources of stress can be: type of activity, characteristic features of the computer, software used, work organization, social aspects. Working on a VDT has specific stress factors, such as the delay time of the computer’s response (reaction) when executing human commands, “learnability of control commands” (ease of memorization, similarity, ease of use, etc.), method of information visualization, etc. Being in a state of stress can lead to changes in a person's mood, increased aggressiveness, depression, and irritability. Cases of psychosomatic disorders, gastrointestinal dysfunction, sleep disturbances, changes in heart rate, and menstrual cycle have been recorded. A person's exposure to long-term stress factors can lead to the development of cardiovascular diseases.

Complaints from personal computer users and possible reasons for their origin.

Subjective complaints Possible causes
pain in the eyes visual ergonomic parameters of the monitor, lighting in the workplace and indoors
headache aeroion composition of air in the work area, operating mode
increased nervousness, electromagnetic field, color scheme of the room, operating mode
increased fatigue electromagnetic field, operating mode
memory disorder electromagnetic field, operating mode
sleep disturbance operating mode, electromagnetic field
hair loss electrostatic fields, operating mode
acne and skin redness, electrostatic field, aeroionic and dust composition of air in the work area
abdominal pain, improper sitting caused by improper workplace design
lower back pain, incorrect seating of the user caused by the design of the workplace, operating mode
pain in the wrists and fingers; incorrect configuration of the workplace, including the height of the table does not correspond to the height and height of the chair; uncomfortable keyboard; operating mode

The Swedish TCO92/95/98 and MPR II are widely known as technical safety standards for monitors. These documents define the requirements for a personal computer monitor based on parameters that can affect the user’s health. TCO 95 imposes the most stringent requirements on the monitor. It limits the parameters of the monitor’s radiation, power consumption, and visual parameters, so that it makes the monitor the most loyal to the user’s health. In terms of emission parameters, TCO 92 also corresponds to it. The standard was developed by the Swedish Trade Union Confederation.

The MPR II standard is less stringent, setting electromagnetic field limits approximately 2.5 times higher. Developed by the Radiation Protection Institute (Sweden) and a number of organizations, including the largest monitor manufacturers. In terms of electromagnetic fields, the MPR II standard corresponds to the Russian sanitary standards SanPiN 2.2.2.542-96 “Hygienic requirements for video display terminals, personal electronic computers and organization of work.” Means to protect users from EMF

The main types of protective equipment offered are protective filters for monitor screens. They are used to limit the user's exposure to harmful factors from the monitor screen, improve the ergonomic parameters of the monitor screen and reduce the monitor radiation towards the user.

3. How does EMF affect health?

In the USSR, extensive research into electromagnetic fields began in the 60s. A large amount of clinical material has been accumulated on the adverse effects of magnetic and electromagnetic fields, and it was proposed to introduce a new nosological disease “Radio wave disease” or “Chronic microwave damage.” Subsequently, the work of scientists in Russia established that, firstly, the human nervous system, especially higher nervous activity, is sensitive to EMF, and, secondly, that EMF has the so-called. informational effect when exposed to a person at intensities below the threshold value of the thermal effect. The results of these works were used in the development of regulatory documents in Russia. As a result, the standards in Russia were set very stringent and differed from American and European ones by several thousand times (for example, in Russia the MPL for professionals is 0.01 mW/cm2; in the USA - 10 mW/cm2).

Biological effects of electromagnetic fields

Experimental data from both domestic and foreign researchers indicate high biological activity of EMF in all frequency ranges. At relatively high levels of irradiating EMF, modern theory recognizes a thermal mechanism of action. At a relatively low level of EMF (for example, for radio frequencies above 300 MHz it is less than 1 mW/cm2), it is customary to talk about the non-thermal or informational nature of the impact on the body. The mechanisms of action of EMF in this case are still poorly understood. Numerous studies in the field of biological effects of EMF will allow us to determine the most sensitive systems of the human body: nervous, immune, endocrine and reproductive. These body systems are critical. The reactions of these systems must be taken into account when assessing the risk of EMF exposure to the population.

The biological effect of EMF under conditions of long-term exposure accumulates over many years, resulting in the development of long-term consequences, including degenerative processes of the central nervous system, blood cancer (leukemia), brain tumors, and hormonal diseases. EMFs can be especially dangerous for children, pregnant women (embryos), people with diseases of the central nervous, hormonal, and cardiovascular systems, allergy sufferers, and people with weakened immune systems.

Effect on the nervous system.

A large number of studies carried out in Russia, and the monographic generalizations made, give grounds to classify the nervous system as one of the most sensitive systems in the human body to the effects of EMFs. At the level of the nerve cell, structural formations for the transmission of nerve impulses (synapse), at the level of isolated nerve structures, significant deviations occur when exposed to low-intensity EMF. Higher nervous activity and memory change in people who have contact with EMF. These individuals may be prone to developing stress reactions. Certain brain structures have increased sensitivity to EMF. Changes in the permeability of the blood-brain barrier can lead to unexpected adverse effects. The nervous system of the embryo exhibits particularly high sensitivity to EMF.

Effect on the immune system

Currently, sufficient data have been accumulated indicating the negative impact of EMF on the immunological reactivity of the body. The results of research by Russian scientists give reason to believe that when exposed to EMF, the processes of immunogenesis are disrupted, more often in the direction of their inhibition. It has also been established that in animals irradiated with EMF, the nature of the infectious process changes - the course of the infectious process is aggravated. The occurrence of autoimmunity is associated not so much with a change in the antigenic structure of tissues, but with the pathology of the immune system, as a result of which it reacts against normal tissue antigens. In accordance with this concept. the basis of all autoimmune conditions is primarily immunodeficiency in the thymus-dependent cell population of lymphocytes. The influence of high-intensity EMF on the body’s immune system is manifested in a suppressive effect on the T-system of cellular immunity. EMFs can contribute to nonspecific inhibition of immunogenesis, increased formation of antibodies to fetal tissues and stimulation of an autoimmune reaction in the body of a pregnant female.

Effect on the endocrine system and neurohumoral response.

In the works of Russian scientists back in the 60s, in the interpretation of the mechanism of functional disorders under the influence of EMF, the leading place was given to changes in the pituitary-adrenal system. Studies have shown that under the influence of EMF, as a rule, stimulation of the pituitary-adrenaline system occurred, which was accompanied by an increase in the content of adrenaline in the blood and activation of blood coagulation processes. It was recognized that one of the systems that is early and naturally involved in the body's response to the influence of various environmental factors is the hypothalamic-pituitary-adrenal cortex system. The research results confirmed this position.

Effect on sexual function.

Sexual dysfunction is usually associated with changes in its regulation by the nervous and neuroendocrine systems. Related to this are the results of work on studying the state of gonadotropic activity of the pituitary gland under the influence of EMF. Repeated exposure to EMF causes a decrease in the activity of the pituitary gland
Any environmental factor that affects the female body during pregnancy and affects embryonic development is considered teratogenic. Many scientists attribute EMF to this group of factors.
Of primary importance in teratogenesis studies is the stage of pregnancy during which EMF exposure occurs. It is generally accepted that EMFs can, for example, cause deformities by acting at different stages of pregnancy. Although there are periods of maximum sensitivity to EMF. The most vulnerable periods are usually the early stages of embryo development, corresponding to the periods of implantation and early organogenesis.
An opinion was expressed about the possibility of a specific effect of EMF on the sexual function of women and on the embryo. A higher sensitivity to the effects of EMF of the ovaries than the testes was noted. It has been established that the sensitivity of the embryo to EMF is much higher than the sensitivity of the maternal body, and intrauterine damage to the fetus by EMF can occur at any stage of its development. The results of epidemiological studies will allow us to conclude that the presence of contact of women with electromagnetic radiation can lead to premature birth, affect the development of the fetus and, finally, increase the risk of developing congenital deformities.

Other medical and biological effects.

Since the beginning of the 60s, extensive research has been carried out in the USSR to study the health of people exposed to electromagnetic fields at work. The results of clinical studies have shown that prolonged contact with EMF in the microwave range can lead to the development of diseases, the clinical picture of which is determined primarily by changes in the functional state of the nervous and cardiovascular systems. It was proposed to identify an independent disease - radio wave disease. This disease, according to the authors, can have three syndromes as the severity of the disease increases:

• asthenic syndrome;
• astheno-vegetative syndrome;
• hypothalamic syndrome.

The earliest clinical manifestations of the consequences of exposure to EM radiation on humans are functional disorders of the nervous system, manifested primarily in the form of autonomic dysfunctions, neurasthenic and asthenic syndrome. Persons who have been in the area of ​​EM radiation for a long time complain of weakness, irritability, fatigue, weakened memory, and sleep disturbances. Often these symptoms are accompanied by disorders of autonomic functions. Disorders of the cardiovascular system are manifested, as a rule, by neurocirculatory dystonia: lability of pulse and blood pressure, tendency to hypotension, pain in the heart, etc. There are also phase changes in the composition of peripheral blood (lability of indicators) with the subsequent development of moderate leukopenia, neuropenia , erythrocytopenia. Changes in the bone marrow are in the nature of a reactive compensatory stress of regeneration. Typically, these changes occur in people who, due to the nature of their work, were constantly exposed to EM radiation with a fairly high intensity. Those working with MF and EMF, as well as the population living in the area affected by EMF, complain of irritability and impatience. After 1-3 years, some people develop a feeling of internal tension and fussiness. Attention and memory are impaired. There are complaints about low sleep efficiency and fatigue. Considering the important role of the cerebral cortex and hypothalamus in the implementation of human mental functions, it can be expected that prolonged repeated exposure to maximum permissible EM radiation (especially in the decimeter wavelength range) can lead to mental disorders.

4. How to protect yourself from EMF

Organizational measures for protection from EMF Organizational measures for protection from EMF include: selection of operating modes of emitting equipment that ensures a radiation level not exceeding the maximum permissible, limiting the place and time of stay in the EMF action area (protection by distance and time), designation and fencing zones with increased levels of EMF.

Time protection is used when it is not possible to reduce the radiation intensity at a given point to the maximum permissible level. The existing remote control systems provide for a relationship between the intensity of the energy flux density and the irradiation time.

Protection by distance is based on a drop in radiation intensity, which is inversely proportional to the square of the distance and is applied if it is impossible to weaken the EMF by other measures, including protection by time. Protection by distance is the basis for radiation regulation zones to determine the required gap between EMF sources and residential buildings, office premises, etc. For each installation emitting electromagnetic energy, sanitary protection zones must be determined in which the intensity of the EMF exceeds the maximum permissible limit. The boundaries of the zones are determined by calculation for each specific case of placement of a radiating installation when operating at maximum radiation power and are controlled using instruments. In accordance with GOST 12.1.026-80, radiation zones are fenced off or warning signs are installed with the words: “Do not enter, dangerous!”

Engineering and technical measures to protect the population from EMF

Engineering and technical protective measures are based on the use of the phenomenon of shielding electromagnetic fields directly in places where a person stays or on measures to limit the emission parameters of the field source. The latter is usually used at the development stage of a product that serves as a source of EMF. Radio emissions can penetrate into rooms where people are located through window and door openings. For screening observation windows, room windows, glazing of ceiling lights, and partitions, metallized glass with screening properties is used. This property is given to glass by a thin transparent film of either metal oxides, most often tin, or metals - copper, nickel, silver and their combinations. The film has sufficient optical transparency and chemical resistance. When applied to one side of the glass surface, it attenuates the radiation intensity in the range of 0.8 - 150 cm by 30 dB (1000 times). When the film is applied to both surfaces of the glass, the attenuation reaches 40 dB (10,000 times).

To protect the population from the effects of electromagnetic radiation in building structures, metal mesh, metal sheet or any other conductive coating, including specially designed building materials, can be used as protective screens. In some cases, it is sufficient to use a grounded metal mesh placed under the facing or plaster layer. Various films and fabrics with a metallized coating can also be used as screens. In recent years, metallized fabrics based on synthetic fibers have been produced as radio-shielding materials. They are obtained by chemical metallization (from solutions) of fabrics of various structures and densities. Existing production methods make it possible to regulate the amount of applied metal in the range from hundredths to units of microns and change the surface resistivity of tissues from tens to fractions of Ohms. Shielding textile materials are thin, lightweight, and flexible; they can be duplicated with other materials (fabrics, leather, films) and are compatible with resins and latexes.

Common terms and abbreviations

A/m ampere per meter – unit of measurement of magnetic field strength
BS Base station of a cellular radio communication system
V/m volt per meter – unit of measurement of electric field strength
VDT video display terminal
TPL temporary permissible level
WHO World Health Organization
W/m2 watt per square meter - a unit of energy flux density
GOST State Standard
Hz hertz – unit of measurement of frequency
power transmission line
MHz megahertz – a unit multiple of Hz, equal to 1000000 Hz
MHF microwaves
µT microtesla – a unit multiple of T, equal to 0.000001 T
MP magnetic field
MP IF power frequency magnetic field
NEMI non-ionizing electromagnetic radiation
PDU maximum permissible level
PC personal computer
PMF alternating magnetic field
PPE energy flux density
PRTO transmitting radio engineering object
IF industrial frequency, in Russia it is 50 Hz
PC personal electronic computer
Radar radar station
RTPC radio technical transmitting center
Tesla tesla – unit of measurement of magnetic induction, flux density of magnetic induction
EMF electromagnetic field
EP electric field

The abstract is based on materials from the Center for Electromagnetic Safety

Widespread sources of EMF in populated areas are currently radio engineering transmitting centers (RTTCs), emitting electromagnetic waves in the HF and UHF ranges into the environment. A comparative analysis of sanitary protection zones and restricted development zones in the area of ​​operation of such facilities showed that the highest levels of exposure to people and the environment are observed in the area where the RTPC is located “old” with an antenna support height of no more than 180 m. The largest contribution to the total intensity of electromagnetic pollution include cellular base stations, functional television and radio transmitters, radio relay stations, radar stations, microwave devices. Of course, you shouldn’t give up inventions that make life easier. But to prevent technical progress from becoming an enemy from an assistant, you just need to follow some rules and use technical innovations wisely. - systems for the production, transmission, distribution and consumption of direct and alternating current electricity (0-3 kHz): power plants, power lines (VL), transformer substations, house power distribution boards, power cables, electrical wiring, rectifiers and current converters); - Appliances; - electric-powered transport (0-3 kHz): railway transport and its infrastructure, urban transport - metro, trolleybuses, trams, etc. - is a relatively powerful source of magnetic field in the frequency range from 0 to 1000 Hz. The maximum values ​​of magnetic induction flux density (B) in commuter trains reach 75 μT with an average value of 20 μT; - functional transmitters: broadcasting stations of low frequencies (30 - 300 kHz), medium frequencies (0.3 - 3 MHz), high frequencies (3 - 30 MHz) and ultra-high frequencies (30 - 300 MHz); television transmitters; base stations of mobile (including cellular) radio communication systems; ground stations for space communications; radio relay stations; radar stations, etc. In the long list of sources of electromagnetic pollution, we can highlight those that we encounter most often.

Power lines

The wires of a working power transmission line (PTL) create electromagnetic fields of industrial frequency in the adjacent space. The distance over which these fields extend from the line wires reaches tens of meters. The range, propagation and magnitude of the field depend on the voltage class of the power line (the number indicating the voltage class is in the name - for example, a 220 kV power line), the higher the voltage, the larger the zone of increased electromagnetic field level, while the size of the zone does not change during operation power lines. Since the load on power lines can change repeatedly both during the day and with changing seasons, the size of the zone of increased magnetic field level also changes. The boundaries of sanitary protection zones for power lines on existing lines are determined by the criterion of electric field strength - 1 kV/m. The placement of ultra-high voltage overhead lines (750 and 1150 kV) is subject to additional requirements regarding the conditions of exposure to the electric field on the population. Thus, the closest distance from the axis of the designed 750 and 1150 kV overhead power lines to the boundaries of populated areas should, as a rule, be at least 250 and 300 m, respectively.

Household electrical appliances

The most powerful are microwave ovens, convection ovens, refrigerators with a “no frost” system, electric stoves, televisions, and computers. The actual EMF generated, depending on the specific model and mode of operation, can vary greatly among equipment of the same type. The electromagnetic field values ​​are closely related to the power of the device. Moreover, the degree of pollution increases exponentially with increasing power.

Functional transmitters

Radar systems operate at frequencies from 500 MHz to 15 GHz, but individual systems can operate at frequencies up to 100 GHz. The EM signal they create is fundamentally different from radiation from other sources. This is due to the fact that periodic movement of the antenna in space leads to spatial intermittency of irradiation. Temporary intermittency of irradiation is due to the cyclical operation of the radar on radiation. The operating time in various operating modes of radio equipment can range from several hours to a day. So, for weather radars with a time intermittency of 30 minutes - emission, 30 minutes - pause, the total operating time does not exceed 12 hours, while airport radar stations in most cases operate around the clock. The width of the radiation pattern in the horizontal plane is usually several degrees, and the duration of irradiation over the viewing period is tens of milliseconds. Meteorological radars can create a PES of ~100 W/m2 for each irradiation cycle at a distance of 1 km. Airport radar stations create a PES of ~ 0.5 W/m 2 at a distance of 60 m. Marine radar equipment is installed on all ships; it usually has a transmitter power an order of magnitude lower than that of airfield radars, so in normal scanning mode the PES created at a distance several meters, does not exceed 10 W/m2. An increase in the power of radars for various purposes and the use of highly directional all-round antennas leads to a significant increase in the intensity of EMR in the microwave range and creates long-distance zones with a high energy flux density on the ground. The most unfavorable conditions are observed in residential areas of cities within which airports are located.

cellular

The main elements of a cellular communication system are base stations (BS) and mobile radiotelephones (MRT). Base stations maintain radio communication with mobile radiotelephones, as a result of which BS and MRI are sources of electromagnetic radiation. An important feature of the cellular radio communication system is the very efficient use of the radio frequency spectrum allocated for the system’s operation (repeated use of the same frequencies, use of different access methods), which makes it possible to provide telephone communications to a significant number of subscribers. The system uses the principle of dividing a certain territory into zones, or “cells,” with a radius of usually 0.5-10 kilometers. Base stations maintain communication with mobile radiotelephones located in their coverage area and operate in signal reception and transmission modes. Depending on the standard, BS emit electromagnetic energy in the frequency range from 463 to 1880 MHz. BS are a type of transmitting radio engineering objects, the radiation power of which (load) is not constant 24 hours a day. The load is determined by the presence of cell phone owners in the service area of ​​a particular base station and their desire to use the phone for a conversation, which, in turn, fundamentally depends on the time of day, location of the BS, day of the week, etc. At night, the load of the BS is almost zero . A mobile radiotelephone (MRT) is a small-sized transceiver. Depending on the phone standard, transmission is carried out in the frequency range 453 - 1785 MHz. The MRI radiation power is a variable value that largely depends on the state of the communication channel “mobile radiotelephone - base station,” i.e., the higher the BS signal level at the receiving location, the lower the MRI radiation power. The maximum power is in the range of 0.125-1 W, but in a real situation it usually does not exceed 0.05 - 0.2 W.

The question of the impact of MRI radiation on the user’s body still remains open. Numerous studies conducted by scientists from different countries, including Russia, on biological objects (including volunteers) have led to ambiguous, sometimes contradictory, results. The only undeniable fact is that the human body “responds” to the presence of cell phone radiation.

Satellite connection

Satellite communication systems consist of a transceiver station on Earth and a satellite in orbit. The antenna pattern of satellite communication stations has a clearly defined narrowly directed main beam - the main lobe. The energy flux density (EFD) in the main lobe of the radiation pattern can reach several hundred W/m 2 near the antenna, also creating significant field levels at a large distance. For example, a station with a power of 225 kW, operating at a frequency of 2.38 GHz, creates a PES equal to 2.8 W/m 2 at a distance of 100 km. However, energy dissipation from the main beam is very small and occurs most in the area where the antenna is located.

TV and radio stations

Television transmitters are usually located in cities. Transmitting antennas are usually located at altitudes above 110 m. From the point of view of assessing the impact on health, field levels at distances from several tens of meters to several kilometers are of interest. Typical electric field strengths can reach 15 V/m at a distance of 1 km from a 1 MW transmitter. In Russia, at present, the problem of assessing the level of EMF of television transmitters is especially relevant due to the sharp increase in the number of television channels and transmitting stations. Transmitting radio centers (RTC) are located in specially designated areas and can occupy fairly large areas (up to 1000 hectares). In their structure, they include one or more technical buildings where radio transmitters are located, and antenna fields on which up to several dozen antenna-feeder systems (AFS) are located. The AFS includes an antenna used to measure radio waves and a feed line that supplies high-frequency energy generated by the transmitter to it. The zone of possible adverse effects of EMFs created by the PRC can be divided into two parts. The first part of the zone is the PRC territory itself, where all the services that ensure the operation of radio transmitters and AFS are located. This territory is guarded and only persons professionally associated with the maintenance of transmitters, switches and AFS are allowed into it. The second part of the zone is the territories adjacent to the PRC, access to which is not limited and where various residential buildings can be located, in this case there is a threat of exposure to the population located in this part of the zone. The location of the PRC can be different, for example, in Moscow and St. Petersburg it is typically located in close proximity or among residential buildings. Widespread sources of EMF in populated areas are currently radio engineering transmitting centers (RTTCs), emitting electromagnetic waves in the HF and UHF ranges into the environment.

Technological progress also has a downside. The global use of various electrically powered equipment has caused pollution, which is given the name electromagnetic noise. In this article we will look at the nature of this phenomenon, the degree of its impact on the human body and protective measures.

What is it and sources of radiation

Electromagnetic radiation is electromagnetic waves that arise when a magnetic or electric field is disturbed. Modern physics interprets this process within the framework of the theory of wave-particle duality. That is, the minimum portion of electromagnetic radiation is a quantum, but at the same time it has frequency-wave properties that determine its main characteristics.

The spectrum of frequencies of electromagnetic field radiation allows us to classify it into the following types:

• radio frequency (these include radio waves);
• thermal (infrared);
• optical (that is, visible to the eye);
• radiation in the ultraviolet spectrum and hard (ionized).

A detailed illustration of the spectral range (electromagnetic radiation scale) can be seen in the figure below.

Nature of radiation sources

Depending on their origin, sources of radiation of electromagnetic waves in world practice are usually classified into two types, namely:

• disturbances of the electromagnetic field of artificial origin;
• radiation coming from natural sources.

Radiations emanating from the magnetic field around the Earth, electrical processes in the atmosphere of our planet, nuclear fusion in the depths of the sun - they are all of natural origin.

As for artificial sources, they are a side effect caused by the operation of various electrical mechanisms and devices.

The radiation emanating from them can be low-level and high-level. The degree of intensity of the electromagnetic field radiation completely depends on the power levels of the sources.

Examples of sources with high levels of EMR include:

• Power lines are usually high-voltage;
• all types of electric transport, as well as the accompanying infrastructure;
• television and radio towers, as well as mobile and mobile communication stations;
• installations for converting the voltage of the electrical network (in particular, waves emanating from a transformer or distribution substation);
• elevators and other types of lifting equipment that use an electromechanical power plant.

Typical sources emitting low-level radiation include the following electrical equipment:

• almost all devices with a CRT display (for example: payment terminal or computer);
• various types of household appliances, from irons to climate control systems;
• engineering systems that provide electricity supply to various objects (this includes not only power cables, but related equipment, such as sockets and electricity meters).

Separately, it is worth highlighting special equipment used in medicine that emits hard radiation (X-ray machines, MRI, etc.).

Impact on humans

In the course of numerous studies, radiobiologists have come to a disappointing conclusion - long-term radiation of electromagnetic waves can cause an “explosion” of diseases, that is, it causes the rapid development of pathological processes in the human body. Moreover, many of them cause disturbances at the genetic level.

Video: How electromagnetic radiation affects people.
https://www.youtube.com/watch?v=FYWgXyHW93Q

This is due to the fact that the electromagnetic field has a high level of biological activity, which negatively affects living organisms. The influence factor depends on the following components:

• the nature of the radiation produced;
• how long and with what intensity it continues.

The effect on human health of radiation, which is of an electromagnetic nature, directly depends on the location. It can be either local or general. In the latter case, large-scale exposure occurs, for example, radiation produced by power lines.

Accordingly, local irradiation refers to exposure to certain areas of the body. Electromagnetic waves emanating from an electronic watch or mobile phone are a vivid example of local influence.

Separately, it is necessary to note the thermal effect of high-frequency electromagnetic radiation on living matter. The field energy is converted into thermal energy (due to the vibration of molecules); this effect is the basis for the operation of industrial microwave emitters used to heat various substances. In contrast to its benefits in production processes, thermal effects on the human body can be detrimental. From a radiobiological point of view, being near “warm” electrical equipment is not recommended.

It is necessary to take into account that in everyday life we ​​are regularly exposed to radiation, and this happens not only at work, but also at home or when moving around the city. Over time, the biological effect accumulates and intensifies. As electromagnetic noise increases, the number of characteristic diseases of the brain or nervous system increases. Note that radiobiology is a fairly young science, so the harm caused to living organisms from electromagnetic radiation has not been thoroughly studied.

The figure shows the level of electromagnetic waves produced by conventional household appliances.

Note that the field strength level decreases significantly with distance. That is, to reduce its effect, it is enough to move away from the source at a certain distance.

The formula for calculating the norm (standardization) of electromagnetic field radiation is specified in the relevant GOSTs and SanPiNs.

Radiation protection

In production, absorbing (protective) screens are actively used as means of protecting against radiation. Unfortunately, it is not possible to protect yourself from electromagnetic field radiation using such equipment at home, since it is not designed for this.

• in order to reduce the impact of electromagnetic field radiation to almost zero, you should move away from power lines, radio and television towers at a distance of at least 25 meters (the power of the source must be taken into account);
• for CRT monitors and TVs this distance is much smaller - about 30 cm;
• Electronic watches should not be placed close to the pillow; the optimal distance for them is more than 5 cm;
• As for radios and cell phones, bringing them closer than 2.5 centimeters is not recommended.

Note that many people know how dangerous it is to stand next to high-voltage power lines, but most people do not attach importance to ordinary household electrical appliances. Although it is enough to place the system unit on the floor or move it further away, and you will protect yourself and your loved ones. We advise you to do this, and then measure the background from the computer using an electromagnetic field radiation detector to clearly verify its reduction.

This advice also applies to the placement of the refrigerator; many people place it near the kitchen table, which is practical, but unsafe.

No table can indicate the exact safe distance from a specific electrical equipment, since radiation may vary, both depending on the device model and the country of manufacture. At the moment, there is no single international standard, so standards in different countries may have significant differences.

The radiation intensity can be accurately determined using a special device - a fluxmeter. According to the standards adopted in Russia, the maximum permissible dose should not exceed 0.2 µT. We recommend taking measurements in the apartment using the above-mentioned device for measuring the degree of electromagnetic field radiation.

Fluxmeter - a device for measuring the degree of radiation of an electromagnetic field

Try to reduce the time you are exposed to radiation, that is, do not stay near operating electrical devices for a long time. For example, it is not at all necessary to constantly stand at the electric stove or microwave oven while cooking. Regarding electrical equipment, you can notice that warm does not always mean safe.

Always turn off electrical appliances when not in use. People often leave various devices turned on, not taking into account that at this time electromagnetic radiation is emanating from electrical equipment. Turn off your laptop, printer or other equipment; there is no need to expose yourself to radiation again; remember your safety.

Sources of electromagnetic fields (EMF) are extremely diverse - these are power transmission and distribution systems (power lines, transformer and distribution substations) and devices that consume electricity (electric motors, electric stoves, electric heaters, refrigerators, televisions, video display terminals, etc.).

Sources that generate and transmit electromagnetic energy include radio and television broadcast 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 population may be exposed to isolated electric or magnetic field components or a combination of both. Depending on the relationship of the exposed person to the source of radiation, it is customary to distinguish between several types of exposure - professional, non-professional, exposure at home and exposure for therapeutic purposes. Occupational exposure is characterized by a variety of generation modes and options for exposure to electromagnetic fields (irradiation in the near zone, in the induction zone, general and local, combined with the action of other unfavorable factors in the working environment). In conditions of non-occupational exposure, the most typical is general exposure, in most cases in the wave zone.

Electromagnetic fields generated by certain sources can affect the entire body of a working person (general exposure) or a separate part of the body (local exposure). In this case, 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), as well as combined (under conditions of simultaneous exposure to EMF and other unfavorable physical factors of the working environment) exposure.

An electromagnetic wave is an oscillatory process associated with interconnected electric and magnetic fields varying in space and time.

An electromagnetic field is the area of ​​propagation of electromagnetic

Characteristics of electromagnetic waves. An electromagnetic field is characterized by a radiation frequency f, measured in hertz, or a wavelength X, measured in meters. An electromagnetic wave propagates in a vacuum at the speed of light (3,108 m/s), and the relationship between the length and frequency of the electromagnetic wave is determined by the relationship

where c is the speed of light.

The speed of propagation of waves in air is close to the speed of their propagation in vacuum.

An electromagnetic field has energy, and an electromagnetic wave, propagating in space, transfers this energy. The electromagnetic field has electric and magnetic components (Table No. 35).

Electric field strength E is a characteristic of the electrical component of the EMF, the unit of measurement of which is V/m.

Magnetic field strength H (A/m) is a characteristic of the magnetic component of the EMF.

Energy flux density (EFD) is the energy of an electromagnetic wave transferred by an electromagnetic wave per unit time through a unit area. The unit of measurement for PES is W/m.

Table No. 35. Units of measurement of EMF intensity in the International System of Units (SI) Range Quantity name Unit designation Constant magnetic field Magnetic induction Field strength Ampere per meter, A/m Tesla, T Constant electric (electrostatic) field Field strength Potential Electric charge Volt per meter, V/m Coulomb, C Ampere per meter, A/m Electromagnetic field up to 300 MHz Magnetic field strength Electric field strength Ampere per meter, A/m Volts per meter, V/m Electromagnetic field up to 0.3-300 GHz Energy Flux Density Watt per square meter, W/m2

For certain ranges of electromagnetic radiation - EMR (light range, laser radiation) other characteristics have been introduced.

Classification of electromagnetic fields. The frequency range and length 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 humans.

The physical basis of ionizing radiation is also made up of 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 type of electromagnetic radiation (EMR) is laser radiation (LR), generated in the wavelength range 0.1...1000 microns. The peculiarity of LR is its monochromaticity (strictly one wavelength), coherence (all radiation sources emit waves in the same phase), and sharp beam directionality (small beam divergence).

Conventionally, non-ionizing radiation (fields) can include electrostatic fields (ESF) and magnetic fields (MF).

An electrostatic field is a field of stationary 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, alternating.

Depending on the sources of formation, electrostatic fields can exist in the form of an electrostatic field itself, formed in various types of power plants and during electrical processes. In industry, ESPs are widely used for electrogas purification, electrostatic separation of ores and materials, and electrostatic application of paints and polymers. Manufacturing, testing,

transportation and storage of semiconductor devices and integrated circuits, grinding and polishing of cases for 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 they create can arise when dielectric liquids and some bulk materials move through pipelines, when dielectric liquids are poured, or when film or paper is rolled.

Table No. 36. International classification of electromagnetic waves № range Frequency range name Metric division of wavelengths Length Abbreviated letter designation 1 3-30 Hz Decamegameter 100-10 mm Extremely low, ELF 2 30-300 Hz Megameter 10-1 mm Ultra-low, SLF 3 0.3-3 kHz Hecto-kilometer 1000-100 km Infra-low, INF 4 from 3 to 30 kHz Myriameter 100-10 km Very low, VLF 5 from 30 to 300 kHz Kilometer 10-1 km Low frequencies, LF 6 from 300 to 3000 kHz Hectometer 1-0.1 km Mids, mids 7 from 3 to 30 MHz Decameter 100-10 m Treble, Treble 8 from 30 to 300 MHz Meter 10-1 m Very high, VHF 9 from 300 to 3000 MHz decimeter 1-0.1 m Ultra high, UHF 10 from 3 to 30 GHz Centimeter 10-1 cm Ultra high, microwave 11 from 30 to 300 GHz Millimeter 10-1 mm Extremely high, EHF 12 from 300 to 3000 GHz decimmillimeter 1-0.1 mm Hypertreble, HHF

Electromagnets, solenoids, capacitor-type installations, cast and cermet magnets are accompanied by the appearance of magnetic fields.

In electromagnetic fields, three zones are distinguished, which are formed at different distances from the source of electromagnetic radiation.

Induction zone (near zone) - covers the interval from the radiation source to a distance equal to approximately V2n ~ V6. In this zone, the electromagnetic wave has not yet been formed and therefore the electric and magnetic fields are not interconnected and act independently (first zone).

The interference zone (intermediate zone) is located at distances from approximately V2n to 2lX. In this zone, electromagnetic waves are formed and a person is affected by electric and magnetic fields, as well as an energy impact (second zone).

Wave zone (far zone) - located at distances greater than 2lX. In this zone, an electromagnetic wave is formed, and the electric and magnetic fields are interconnected. A person in this zone is affected by wave energy (third zone).

The effect of the electromagnetic field on the body. The biological and pathophysiological effect of electromagnetic fields on the body depends on the frequency range, the intensity of the influencing factor, the duration of irradiation, the nature of the radiation and the irradiation mode. The effect of EMF on the body depends on the pattern of propagation of radio waves in material environments, 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 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 high water content, at the same field strength, is 60 times higher than in tissues with low water content. Therefore, the depth of penetration of electromagnetic waves into tissues with a low water content is 10 times greater than in tissues with a high water content.

Thermal and athermic 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 and an increase in overall body temperature. 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 emergency situations when safety precautions are violated.

Chronic forms of radio wave injuries, 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

aspects of the cardiovascular system. Along with general asthenia, accompanied by weakness, increased fatigue, restless sleep, patients experience headache, dizziness, psycho-emotional lability, pain in the heart, increased sweating, and decreased appetite. Signs of acrocyanosis, regional hyperhidrosis, cold hands and feet, tremor of the fingers, lability of 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 sex hormones.

One of the few specific lesions caused by exposure to electromagnetic radiation in the radio frequency range is the development of cataracts. In addition to cataracts, when exposed to high-frequency electromagnetic waves, keratitis and damage to the corneal stroma can develop.

Infrared (thermal) radiation, light radiation at high energies, as well as high-level ultraviolet radiation, with acute exposure, can lead to dilation of capillaries, burns of the skin and organs of vision. Chronic irradiation is accompanied by changes in skin pigmentation, the development of chronic conjunctivitis and clouding of the eye lens. Ultraviolet radiation at low levels is useful and necessary for humans, as it enhances metabolic processes in the body and the synthesis of the biologically active form of vitamin D.

The effect of laser radiation on a person depends on the intensity of the radiation, wavelength, nature of the radiation and exposure time. In this case, local and general damage to certain tissues of the human body is distinguished. The target organ in this case is the eye, which is easily damaged, the transparency of the cornea and lens is impaired, and damage to the retina is possible. Laser scanning, especially in the infrared range, can penetrate tissue to a considerable depth, affecting internal organs. Long-term 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 working conditions with sources of electromagnetic radiation” No. 225 dated April 10, 2007, Ministry of Health of the Republic of Kazakhstan; SanPiN “Sanitary rules and standards 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/u-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) during state sanitary supervision" No. 1.02.019/r-94 The Ministry of Health of the Republic of Kazakhstan regulates the intensity of electromagnetic fields of radio frequencies at personnel workplaces,
carrying out work with EMF sources and requirements for monitoring, and irradiation with an electric field is also regulated, 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 300 MHz - 300 GHz - by the surface radiation energy flux density and the energy load (EL) created by it. The total energy flow passing through a unit of irradiated surface during the action time (T), and expressed by the product of PES T, represents the energy load.

At personnel workplaces, the EMF intensity in the frequency range 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 EMFs on personnel does not exceed 50% of the working time, levels higher than those specified are allowed, but not more than 2 times.

Standardization 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 employee during the work shift and taking into account the conditions of general or local exposure.

Table No. 37. Maximum permissible limits for the impact of PMF on workers.

The PMP hygienic standards (Table No. 38), developed by the International Committee on Non-Ionizing Radiation, which operates under the International Radiation Protection Association, are also widely used.

In the process of evolution and life activity, a person is influenced by the natural electromagnetic background, the characteristics of which are used as a source of information that ensures continuous interaction with changing environmental conditions.

However, due to scientific and technological progress, the electromagnetic background of the Earth has now not only increased, but also undergone qualitative changes. Electromagnetic radiation has appeared at wavelengths that are of artificial origin as a result of man-made activities (for example, the millimeter wavelength range, etc.).

The spectral intensity of some man-made sources of electromagnetic field (EMF) may differ significantly from the evolutionarily developed natural electromagnetic background to which humans and other living organisms of the biosphere are accustomed.

Sources of electromagnetic fields

The main sources of EMF of anthropogenic origin include television and radar stations, powerful radio engineering facilities, industrial technological equipment, high-voltage power lines of industrial frequency, thermal shops, plasma, laser and X-ray installations, atomic and nuclear reactors, etc. It should be noted that there are man-made sources of electromagnetic and other physical fields for special purposes, used in electronic countermeasures and placed on stationary and mobile objects on land, water, under water, and in the air.

Any technical device that uses or produces electrical energy is a source of EMFs emitted into external space. A peculiarity of exposure in urban conditions is the impact on the population of both the total electromagnetic background (integral parameter) and strong EMF from individual sources (differential parameter).

The main sources of electromagnetic fields (EMF) of radio frequencies are radio engineering facilities (RTO), television and radar stations (RLS), thermal shops and areas in areas adjacent to enterprises. Exposure to industrial frequency EMF is associated with high-voltage power lines (VL), sources of constant magnetic fields used in industrial enterprises. Zones with increased levels of EMF, the sources of which can be RTO and radar, have dimensions of up to 100...150 m. Moreover, inside buildings located in these zones, the energy flux density, as a rule, exceeds permissible values.

Spectrum of electromagnetic radiation from the technosphere

An electromagnetic field is a special form of matter through which interaction between electrically charged particles occurs. An electromagnetic field in a vacuum is characterized by the vectors of electric field strength E and magnetic field induction B, which determine the forces acting on stationary and moving charges. In the SI system of units, the dimension of electric field strength [E] = V/m - volt per meter and the dimension of magnetic field induction [V] = T - tesla. The sources of electromagnetic fields are charges and currents, i.e. moving charges. The SI unit of charge is called the coulomb (C), and the unit of current is the ampere (A).

The forces of interaction of the electric field with charges and currents are determined by the following formulas:

F e = qE; F m = , (5.9)

where F e is the force acting on the charge from the electric field, N; q is the amount of charge, C; F M - force acting on the current from the magnetic field, N; j is the current density vector, indicating the direction of the current and equal in absolute value to A/m 2 .

The straight brackets in the second formula (5.9) denote the vector product of vectors j and B and form a new vector, the modulus of which is equal to the product of the moduli of vectors j and B multiplied by the sine of the angle between them, and the direction is determined by the right “gimlet” rule, i.e. . when rotating vector j to vector B along the shortest distance, vector . (5.10)

The first term corresponds to the force exerted by an electric field of intensity E, and the second to the magnetic force in a field with induction B.

The electric force acts in the direction of the electric field strength, and the magnetic force is perpendicular to both the speed of the charge and the magnetic field induction vector, and its direction is determined by the right-hand screw rule.

EMFs from individual sources can be classified according to several criteria, the most common of which is frequency. Non-ionizing electromagnetic radiation occupies a fairly wide frequency range from the ultra-low frequency (ULF) range of 0...30 Hz to the ultraviolet (UV) region, i.e. up to frequencies 3 1015 Hz.

The spectrum of man-made electromagnetic radiation extends from ultra-long waves (several thousand meters or more) to short-wave γ-radiation (with a wavelength of less than 10-12 cm).

It is known that radio waves, light, infrared and ultraviolet radiation, x-rays and γ-radiation are all waves of the same electromagnetic nature, differing in wavelength (Table 5.4).

Subbands 1...4 refer to industrial frequencies, subbands 5...11 - to radio waves. The microwave range includes waves with frequencies of 3...30 GHz. However, historically, the microwave range is understood as wave oscillations with a length of 1 m to 1 mm.

Table 5.4. Electromagnetic wave scale

Wavelength λ	Wave subbands	Oscillation frequency v	Range
	No. 1...4. Ultra long waves
	No. 5. Kilometer waves (LF - low frequencies)
	No. 6. Hectometric waves (MF - middle frequencies)
			Radio waves
	No. 8. Meter waves (VHF - very high frequencies)
	No. 9. Decimeter waves (UHF - ultra high frequencies)
	No. 10. Centimeter waves (microwave - ultra high frequencies)
	No. 11. Millimeter waves (millimeter wave)
0.1 mm (100 µm)	Submillimeter waves
	Infrared radiation (IR range)	4.3 10 14 Hz	Optic range
	Visible range	7.5 10 14 Hz
	Ultraviolet radiation (UV range)
	X-ray range
	γ-Radiation
	Cosmic rays

The optical range in radiophysics, optics, and quantum electronics refers to the range of wavelengths from approximately submillimeter to far ultraviolet radiation. The visible range includes vibrations of waves with lengths from 0.76 to 0.38 microns.

The visible range is a small part of the optical range. The boundaries of the transitions of UV radiation, X-ray, and γ-radiation are not exactly fixed, but approximately correspond to those indicated in the table. 5.4 values ​​of λ and v. Gamma radiation, which has significant penetrating power, transforms into radiation of very high energies, called cosmic rays.

In table Table 5.5 shows some man-made sources of EMF operating in various ranges of the electromagnetic spectrum.

Table 5.5. Technogenic sources of EMF

Name	Frequency range (wavelengths)
Radio engineering objects	30 kHz...30 MHz
Radio transmitting stations	30 kHz...300 MHz
Radar and radio navigation stations	Microwave range (300 MHz - 300 GHz)
TV stations	30 MHz...3 GHz
Plasma installations	Visible, IR, UV ranges
Thermal installations	Visible, IR range
High voltage power lines	Industrial frequencies, static electricity
X-ray installations	Hard UV, X-ray, visible light
	Optical range
	Microwave range
Process installations	HF, microwave, IR, UV, visible, X-ray ranges
Nuclear reactors	X-ray and γ-radiation, IR, visible, etc.
Special-purpose EMF sources (ground, water, underwater, air) used in electronic countermeasures	Radio waves, optical range, acoustic waves (combination of action)