The rapid and widespread increase of communication technologies that use electricity has greatly changed the electromagnetic environment around us, in addition to the constant increase in the use of electricity there is an increasing use of sources and devices that emit electromagnetic waves .
All this leads to an increasing spread of exposure and justifies the need to evaluate different effects from thermal effects which prevention is the basis of exposure limits currently in force.
In recent years there have been numerous scientific studies on the possible dangers of electromagnetic waves to the human body. Some of these have confirmed the presence of significant adverse effects (cancer, memory loss, changes in behavior and development of children, reduced fertility), others have stressed the absolute absence of danger to the human body.
For example, a recent study by the National Cancer Institute (the American Institute which deals with the Cancer Research) found that after using a cell phone for 50 minutes, the tissues of the brain on the side of the phone metabolize more glucose tissue than the other side. In this regard, it should be pointed out that as a result of extensive scientific research and laboratory studies on animals, electromagnetic waves have the following biological effects:
- from 25 to 30 MHz (CB, radio taxi, radio astronomy, etc.). penetrate every tissue of the human body, bones and especially in the brain, spinal cord and into the crystalline of the eye;
- from 87 to 108 MHz (FM Broadcast) penetrate up to 4 inches deep in the brain, spinal cord and in the lens;
- from 174 to 230 MHz (VHF television band) effects especially on children growing;
- from 470 Mhz to 1 GHz (elevision band IV/V and UHF mobile telephony) penetrate into the brain up to 2 cm and have a power efficiency ten times higher than that of the FM waves;
- from 2,4 to 2,5 GHz (radar, satellites, microwave ovens, amateur radio satellite) penetrate into the brain up to 1 cm and are harmful to the eyes, blood and micro-organisms;
- from 10 to 100 GHz (military radar, industrial furnaces, the Earth exploration-satellite and space research, radiolocation, meteorology) penetrate a few millimeters into the brain, damage the blood and micro-organisms possess a potency about ten thousand times greater than that of the waves of 10MHz.
The electromagnetic field and waves
The electromagnetic field is given by the electric field that varies periodically in time which generates the magnetic field in Fig.1, perpendicularly to itself and in the propagation direction.
The electromagnetic waves, so generated, are propagated in phase, to the speed of light of 300,000 km/s in free space. They are characterized by the following parameters:
- FREQUENCY represents the number of complete oscillations carried by the electromagnetic wave in a time interval of one second, and is measured in Hertz (Hz).
- WAVELENGTH corresponds to the distance in meters of a complete oscillation or at a distance of two minima or two maxima of the wave. It is represented by the Greek letter λ and is related to the frequency by the relation λ = c / f where: λ is the wavelength in meters; c is the speed of light in meters per second and is equal to 3・108 m/s; f is the frequency in Hertz. From this relationship you can see that the wavelength is inversely proportional to the frequency.
- INTENSITY is the amount of energy that flows perpendicular to the propagation direction, in a second through a surface of one square meter, it is measured in W/m2.
These parameters are related to each other and each influences the effect that the field can have on a biological system. In the vicinity of a radiating element (antennas, industrial equipment, household appliances, power lines, etc..) the electric field and the magnetic field can be considered separately. For distances greater than about a tenth of the wavelength, the field structure begins to suffer from the phenomenon of radiation that is the two fields are mutually concatenated and are propagated in free space in the form of electromagnetic field.
The electric field is represented by the symbol E and is measured in volts per meter (V/m), while the magnetic field is represented by the symbol H and is measured in amperes per meter (A/m) or more generally in Tesla ( T ). Actually the Tesla is the unit of measurement of magnetic flux density represented by the symbol B which manifests itself especially when you are in the presence of ferromagnetic materials. Between the two units there is a relationship 1 Tesla = 795 800 A/m. Since the Tesla is a unit of measurement for the magnetic field, very large, typically you can refer to its submultiple the micro Tesla (μT) equal to one millionth of a Tesla for which the relationship becomes 1 μT = 0.7958 A / m .
An electromagnetic wave carries energy which is defined as “power density” and is represented by the symbol S. The power density is the energy transported per unit time and surface and is expressed in watts per square meter (W/m2), it is proportional to the product of the intensity of the electric field and the magnetic field.
The frequency is the main parameter which influences the mode of interaction of the electromagnetic field with a biological system and therefore affects the effects to the point that, an electromagnetic field with equal intensity, can be almost insignificant or very dangerous depending on its frequency.
In the case of electrical installations, electric power, the electric equipment in general, there is no appreciable production of electromagnetic waves because the frequency of 50 Hz is too low, it in fact corresponds to a wavelength of 6000 km and up to a virtually distance of approximately 600 km from the source, the electric field and magnetic field are independent of one another and can have effects only at a distance of some tens of centimeters. It should be specified that the alternating magnetic field occurs mainly when an electric current runs through a cable, and is enhanced by coils such as those of extensions or from the windings of transformers and electric motors. Their magnetic field is directly proportional to the value of the current.
The alternating electric field occurs in all conductors, switches, sockets, electrical panels and equipment, when they are under tension. The alternating electric field, in contrast to the magnetic one, is emitted even when there is no current in the system, but it is powered. In other words, there is an electric field even when the devices are turned off, but the voltage is still present in the system, from the controls to the sockets and in long power cords of the devices plugged in. The electric field is directly proportional to the voltage, in Fig 2 there is an example of the visible presence of the two types of radiation in the residential sector.
Currently it is quite easy to shield the electric field while it is much more difficult to shield the magnetic field. There are excellent screens for electric fields:
- the heavy building materials such as bricks and concrete;
- all types of metal such as aluminum foil for household appliances;
- tapes and stockings of copper for electrical cables and electronic;
- paints based on graphite and certain types of fabrics.
To shield the magnetic fields at low frequency, however, you can use the ferromagnetic substances such as nickel, iron and cobalt, or alloys thereof. It has recently been introduced on the market a product material in Italy, called SKUDOTECH an alloy with high magnetic permeability that with thickness of only 0.5 mm. This material reaches attenuation factors of the magnetic field up to 40 dB.
The electromagnetic spectrum
Respect to the relationship with biological systems, the spectrum of electromagnetic waves is divided into two main types, as shown in Figure 3:
– Ionizating Radiation (IR) with a frequency exceeding 300 GHz (x-rays, gamma rays), these radiations are able to break, even with very small intensities, the chemical bonds of the molecules of the human body, favoring the formation in it of very reactive molecules that can cause serious damage to the biological systems causing very serious diseases such as leukemia or cancers of various kinds.
– Non Ionizating Radiation (NIR) with a frequency of less than 300 GHz, such as: ELF (extremely low frequency 1÷300 Hz); IF (intermediate frequency 300 Hz ÷ 10 MHz); RF (radio frequency 10 MHz ÷ 1 GHz); MW (microwave 1 ÷ 300 GHz). This radiation, even in the presence of high field intensity, is not able to break chemical bonds of the molecules of the human body and the main effect that it produces on the molecules is to make them oscillate producing friction and consequently heat; an example is the cooking with your microwave oven.
Sources of electromagnetic waves and their effects
Electromagnetic waves in addition to being produced and used in the telecommunications industry for the remote transmission of sound, images and data, are also present in our daily lives.
For example, walking on the carpet due to friction you can produce a strong electric field. The cathode ray tube of a television or computer monitor emits electrons that in addition to hit the screen they are propagated even in the environment. Motors of refrigerators, dishwashers, washing machines and air conditioners radiate a considerable electromagnetic energy in the environment. Irons; synthetic materials can be electrostatically charged by friction as the pantyhose and continuous changes of clothing. Other causes of the presence of electromagnetic fields in the environment are: the distribution lines of high voltage overhead and underground, parabolic antennas for satellite communications, military and civilian radar systems, alarm systems, metal detectors, cellular telephony, automated systems for access control, electromedical equipment, systems remote opening gates and doors.
The effect of non-ionizing electromagnetic waves (NIR) is generally not harmful, that is, it can not harm the health of the exposed individual, but exactly it is a biological effect that may or may not result in harm to the health of the exposed individual.
The most obvious of the biological effects of electromagnetic fields is heating of body tissues, an effect known to be used by microwave ovens which is also easily seen after a long conversation using mobile phone. In Fig. 4 you can see, using a thermal image, the effect of heating of the tissues before (image A) and after (image B) a 15-minute conversation with the phone.
In addition, we have to add that the effects of this phenomenon, incorrectly called “electrosmog“, it is difficult to detect due to the fact that turns out to be an abnormal form of pollution because it does not give rise to processes of accumulation in the environment, but contaminants are present only as long as the sources that produced them remain in use.
As regards the daily life, the NIR radiation is non-ionizing below 300 GHz, such as household electrical appliances, mobile telephony equipment, broadcasting and data, computer, trains and trams, electric power lines, electric motors, transformers, radar and security systems. These devices generate current circulation more or less localized in the human body, resulting in overheating of parts exposed to radiation. The danger of this phenomenon lies in the fact that overheating occurs internally to the body to which it is not adequately perceived by the sensory organs. In this way the body is not able to activate the necessary compensation mechanisms. The organs with a poor blood circulation, which promotes the dispersion of the heat produced, are the most affected such as corneas and testicles.
The depth of penetration of the electromagnetic waves in the tissues of the human body is inversely proportional to the frequency, that is, it increases when frequency decreases. To measure the radiant energy absorbed by the body per unit of time is used the specific absorption rate SAR (Specific Absorption Rate) measured in W/kg. This is the amount of heat energy absorbed in one second by a kilogram of body mass. The SAR is influenced by many variables, both physical (frequency, polarization, modulation) and biological (biological properties of the body, size, orientation with respect to the lines of force) and changes according to the different characteristics of the human body such as clothes, thickness of the skin, hair, age and sex.
From studies in experimental animals with frequencies up to 10 GHz, it was found that a SAR must be at least 4 W / kg to produce adverse health effects such as skin burns and / or eye disorders, so this value is usually considered the threshold for human health in the absorption of energy. For example, using a mobile phone, the level of the SAR in the head, is generally of about 2 W/kg corresponding to an increase in body temperature of about 1 °C, then when the absorption exceeds the limit of 10 W/kg for long periods of time , the damage to the body become irreversible.
Amount of energy close to the value of 10 W/kg, can be found only in the immediate vicinity (no more than several meters) of powerful antennas of transmitting equipment usually installed on the tops of mountains suitably fenced, reachable only by experts specially trained, or on tall pylons adequately protected by the approach of strangers. In Fig.5 you can see a radio or television station transmitter, specifically that of Castaldia in the province of Pordenone (Italia) at a height above sea level of 1100 m distant from population centers.
According to some laboratory studies, a significant reduction of melatonin was observed in subjects exposed for prolonged periods to non-ionizing radiation of considerable power. This hormone that regulates mood and the reproductive system, is produced mainly at night by the pineal gland located at the back of the brain. At frequencies above 10 GHz, the penetration depth of the electromagnetic fields in the tissue is small, for which the SAR is no longer a size appropriate for assessing the energy absorbed; a size more appropriate is the density of incident energy expressed in W/m2.
In addition to the thermal effects described, exposure to electromagnetic radiation in the human body determines the biological effects even with very low SAR of 0.01 W/kg. Indeed, the scientific research is still not able to explain with only the heating of tissues. The human biological system is a highly complex system and especially delicate and may be influenced even at very low field intensity, by the resonance between the frequency of the electromagnetic field and that of some mechanisms of the cells.
Yet surely it will take many years of research to get to be a full investigation of these effects, for these reasons, it is still impossible to set precise and safe exposure limits for electromagnetic radiation even at very low field strengths.
The regulations in this regard
In 1998, the ICNIRP (International Commission on Non Ionizing Radiation Protection) has established threshold levels for exposure to non-ionizing radiation providing the guidelines for the standards of various countries.
In Italy, the ICNIRP international guidelines have been implemented in a much more restrictive way with various decrees and regulations (DL 381/1998, EC 519 1999, IEC 211-6, IEC 211-7, EN 50449, IEC 50413, IEC EN 50499, Decree 81 of 2008, Decree 123 of 2008, Decree 179 of 2012). For example the limit recommended by ICNIRP of 41 V/m for the electric field, corresponding to a SAR value of 0.08 W/kg, is already 50 times lower than the value of the threshold of 4 W/kg, while with Decree 381/1998 imposes a limit of 20 V/m, which is further reduced to 6 V/m for the environments in which the permanence exceeds 4 hours per day, such as in schools or in the workplace.
It must be borne in mind that the threshold values reported by the decrees and the rules are the limits of indirect reference, that have been detected in the most easily measurable condition, set in a generic manner taking into account the most unfavorable exposure conditions, without taking into account the fact that the human body absorbs energy under various exposure conditions and especially to personal physical condition.
This is the reason why those limits, because imposed by law and technical standards, must be complied with, even thought it is uncertain whether or not they can cause harmful effects to exposed persons. The guidelines indicate that in fact, below a certain threshold, the exposure to electromagnetic fields is, according to current scientific knowledge, harmless; obviously this does not automatically imply that above these limits the exposure is harmful.
For example, the undersigned, for about 20 years has operated without damage, in large transmission systems up to frequencies of 20 GHz, in locations where there were transmitters with power amplifiers on antenna load of 50 Ω up to 40 kW with high frequency voltage equal to 1400 V. In the vicinity of the pylons, where the antennas were positioned, electromagnetic fields were so intense that it was not possible to use measuring instruments with moving coil, digital clocks, radio, TV.
Thus, in presence of conflicting studies, among those who claim it is not dangerous and who claim the danger of electromagnetic fields, the World Health Organization recommend that you apply a form of preventive intervention against a potentially serious risk, aimed at providing precautionary answers. This, at least until data safe and scientifically proven will not be available. In particular, referring to the DL No. 123 of 9/4/2008 governing the protection of workers from the risks of exposure to electromagnetic fields and to the new Decree N ° 179 of 18/10/2012, the employer is obliged to assess and, if necessary, to calculate and/or measure the levels of electromagnetic fields to which workers are exposed. These assessments must be carried out in accordance with the harmonized European standards from CENELEC.
For all situations not covered by the above European standards, the employer must take the specific guidelines identified by the Advisory Committee for the prevention of accidents and occupational hygiene, or alternatively, those of the IEC also assessing the levels of provided by the manufacturers of the equipment in accordance with the specific Community Directives product.
The elements of the risk assessment of exposure
For a proper assessment of the risk of exposure to electromagnetic fields, you must pay attention to the following items:
- the level, duration, frequency spectrum, the type of exposure;
- the exposure limit values and action values ;
- all the effects on the health and safety of workers and/or exposed individuals ;
- indirect effects such as interference with medical electronic equipment and devices such as cardiac pacemakers and / or other devices; initiation of electrical explosive devices (detonators); fires and explosions caused by sparks produced by induced fields, contact currents, electric shock;
- the existence of replacement equipment designed to reduce the levels of exposure to electromagnetic fields, taking account of the work to be performed;
- the characteristics of the installation of the equipment, their state of maintenance, operating procedures, the characteristics of the environments, the layout of workstations, operating modes adopted by the employees;
- the availability of rehabilitation to minimize exposure levels;
- simultaneous exposure to fields of different frequencies;
- information as a result of health surveillance, including information found in scientific publications.
The rules to follow
Unfortunately, the continuous technological progress forces us to be more and more exposed, even for long periods, to the radiation of electromagnetic waves, BUT TODAY WE KNOW EVERYTHING ABOUT THEIR NATURE, YET WE KNOW LITTLE OR NOTHING ABOUT THEIR REAL BIOLOGICAL EFFECTS, so in order not to excessively underestimate this phenomenon, it is a good idea to respect in every situation, working or not, the following rules:
- do not store the phone on the chest close to the heart, avoiding long and frequent conversations and often switch the listenting between the two ears, using only headsets;
- hold the phone on and/or the clock radio at least one meter away from the pillow or the workplace;
- do not sleep with electric blankets on;
- avoid activating the electric underfloor heating in the bedrooms at night or in the workplace;
- do not stay too long near appliances such as refrigerator, oven, water heater,microwave oven, television, the computer;
- make sure that the microwave oven is turned off before opening, the safety switch may not work properly;
- fully unravel extensions to avoid the formation of loops;
- avoid the use of multiple sockets and/or power strips;
- not have beds, sofas, desks, behind partitions, where appliances or industrial machinery are places;
- keep halogen bulbs at a distance of at least 50 cm, and make sure they are equipped with special glass shield for high frequencies, because in addition to the electromagnetic fields they emit a high-frequency radiation that can be very harmful;
- Always keep the hair dryer at about 30 cm from the head and often change hands;
- Prefer fluorescent lighting and avoid installing electric radiators;
- avoid standing for long periods, at distances of less than a meter from the transformer of halogen bulbs;
- avoid prolonged use of electrical appliances by children;
- hold appliances remote control for children and infants of at least 70cm away from their head;
- keep children at least one meter away from the TV or monitor for video games;
- prevent children observe the food being cooked through the glass of the microwave because the shield can become less effective with time;
- install, if possible, in a general electric panel, a “circuit breaker” network device capable of disconnecting and automatically recover a particular line, such as sleeping quarters when all electrical appliances are switched off or on.