This work is framed within the health and safety at work and refers to the study of the effects of magnetism and non-ionizing electromagnetic radiation on the human body, the risks and effects that could occur when having an electromagnetic field very close to the vital organs and the permissible fundamental magnitudes, as well as the changes and consequences in the health of man.
The bibliography and research and development trends in the application of magnetic fields in the world are reviewed and information is collected regarding the specialties in which it is being used the most.
Summary
The present work is framed inside the security and health in the work and he / she refers to the study of the effects of the magnetism and of the radiations electromagnetic Non-ionizing on the human body, the risks and effects that could happen when having an electromagnetic field very near the vital organs and the permissible fundamental magnitudes, as well as the changes and consequences in the man's health. It is revised the bibliography and investigation tendencies and development of the application of the magnetic fields in the world and information is picked up with respect to the specialties in that more it is using.
Electromagnetic effects on biological tissues
Biological tissues present variations in electrical characteristics when the frequency of the applied field increases or decreases, which implies having and taking safety and health measures at work that allow making technical development in this field compatible with the human body and its different applications in daily practice. People who work in high-voltage and high-frequency installations are exposed to a significant level of electromagnetic charge (EMC), this not only causes changes in the human body, but also in the working conditions and the recommended exposure time.
Historical synthesis of magnetism
The origin of the notion of magnetism is very ancient, dating back more than 3,500 years, in the middle of the Iron Age, in ancient Egypt, China and India. Then it was already discovered that a special stone, the magnetite or natural magnet, attracted iron filings and even adhered to iron objects.
The Roman naturalist Pliny the Elder (23-79 AD) transmitted the interpretation of Nicanor de Colophon (2nd century BC), according to which, the name of magnetite would come from a certain shepherd named Magnes who led his flock to graze, he observed the attraction that the soil rich in this mineral exerted on the iron parts of his boots and cane. By removing the earth to find the cause of the phenomenon, he discovered a stone with the very strange property of attracting iron.
Aristotle writes that the philosopher, mathematician and scientist Thales of Miletus (624-548 BC), one of the "seven sages of Greece" mentioned a mineral stone that had the property of attracting iron. Plato said that Socrates already affirmed the properties of magnetic rings. It is also said that at that time Cleopatra used to wear a tiara of magnets on his forehead to preserve his beauty.
When many centuries later, at the beginning of the Middle Ages, magnetite was known to European alchemists, they called it a "lodestone" (in French pierre aimant) and, as in ancient times, many curious properties were attributed to it, it was supposed that It provided vigor, pain relief, health, and stopped aging processes, among others.
Until after the studies and observations of Galileo Galilei and its experimental confirmation with Ferdinand Magellan's trip around the world, completed by Juan Sebastián Elcano in 1522, it was not generally accepted that the Earth was round, that it rotated in space and that Therefore, it had an axis of rotation whose ends are the Earth's poles.
This new conception of the Earth and the scientific advances that took place in the following four centuries, especially in the field of physics, already led scientists to consider it as a gigantic magnet with its respective magnetic poles in the north and In the south. Meanwhile, studies on the properties of magnets continued and in the 16th century, Philippus Aureolus Paracelsus (1493-1541) used magnets in multiple inflammatory processes in the soma and other regions of the body.
The experimental study of magnetism became known to the world through the publication in 1600 of the book "De Magnete" by William Gilbert, physician to Queen Elizabeth I. The book described the experimental discovery on which it was based, the declination of the needle. magnetized, which had already been noticed by Hartmann in 1544 and studied in detail by Robert Norman (1590), sailor, compass builder and one of the first scientists who did not belong to the nobility and lacked culture.
The English physicist Michael Faraday, in the 19th century, demonstrated the behavior of a magnet around a current. He was the founder of biomagnetism and magnetochemistry. He confirmed that all matter is magnetic, that is, matter is attracted or repelled by a magnetic field.
The German physician, Frederik Franz Antón Mesmer (1734-1815) affirmed that the properties of the natural magnet was a remedy for all diseases and believed that all animated beings were endowed with a similar force, which he called animal magnetism, capable of producing healings in the organs to which it will be applied. This therapeutic theory was called "mesmerism" in his honor.
Mollet in France (1753), in his book "Essalsur Electrifico de Corps" attempted the first objective explanation of the biological effects of electricity.
In 1785, Carlos Agustín Coulomb established with great precision the law that bears his name: "The attraction or repulsion between two magnetic poles with different or equal charges is inversely proportional to the square of the distance that separates them." Ampere and his collaborator Dominique Arago (1786-1853) showed that steel needles become magnetized if they are placed inside a circular wire that carries an electric current. This was the prelude to the construction of the first "electromagnet" in 1825, named after William Sturgeon (1783-1850).
However, the logical and mathematical formalization of all the previous experiments was required to reach a scientific model, which was due to the masterful work of James Clerk Maxwell published in 1873 in which he established the concept of "electric and magnetic fields". The well-known Maxwell equations indicate that magnetic electric fields, varying in time, generate energy waves that propagate in the space environment with the speed of light. This knowledge proved that light is an electromagnetic phenomenon. Maxwell's works were a source of inspiration for many sages in the years that followed: Röentgen, Curie, Rutherford, Plank and Einstein, among others.
The Japanese Fukada and Yasuda, physicist and orthopedic, in 1953 were the first to demonstrate in rabbits, the piezoelectric effects of bone and collagen, when they are subjected to mechanical compression or an electric current.
In 1962, Bassett, Becker, Shamos, and others confirmed piezoelectric properties in living bone and emphasized that potentials are negative in the area of compression and positive in the area of distraction.
Anderson and Ericsson in 1968 added the flow current potentials, also called electrokinetics, present in living, wet bones. This current causes a potential difference in the direction of flow of the different fluids containing ions.
Biological effects of magnetic fields
Magnetization effect (Primary biological effect)
• Responsible for the orientation of molecules and dipole atoms.
• It occurs on elements with "non-zero" magnetic moments.
It includes the following actions:
• Modification of membrane permeability.
• Stabilization of the Na pump.
• Encouragement of liaison processes.
• Stimulation of cell reproduction.
• Activation of REDOX systems.
Piezoelectric effect (secondary biological effect)
• Direct effect:
- Produces the electrical polarization of the mass of a body or the creation of electrical charges on its surface, when it is subjected to mechanical forces.
• Reverse effect:
- Deformation of a body when it is subjected to an electric field.
- Architectural orientation of the bone trabeculae in damaged areas.
Metabolic effect
- Responsible for all the stimulating trophic processes and tissue repair, through: Local control of the blood supply of each tissue.
Nervous control of the blood supply of large segments of the circulation.
Humoral control of certain substances that increase or decrease blood flow.
Application of magnetic fields in medicine
It is vitally important to know how the magnetic and electromagnetic field influences living beings in the first place, but also how man can manipulate it and obtain benefits from its properties, either by direct application or by the development of systems and equipment that improve the quality of life in general.
In major research centers around the world, the systems that apply the magnetic field are highly studied, with satisfactory results in many cases; which opens a vast horizon for the development of various technologies and applications. Without a doubt, the consultation and study of global research and development trends on the application of the magnetic and electromagnetic field in health.
The main lines of research of the magnetic field applied to medicine are currently aimed at:
• Development of methods and equipment for the treatment of diseases using the magnetic and electromagnetic field (CME).
• Development and investigation of the possibilities of diagnosis using Magnetic Resonance Imaging (MRI) systems.
• Study of the adverse effects produced by CME.
It was found that the main effects of CME and that allow it to be used in therapeutic processes are biostimulant, analgesic, anti-inflammatory and anti-oedematous effects. According to the results of this bibliographic consultation, the CME can be used in the treatment of diseases such as:
• Temporary disturbances of cerebral blood circulation after an insult or trauma.
• Neuritis in different locations, phantom pain and vegetative polyneuritis.
• Inflammatory ganglionitis of the sympathetic trunks.
• Mild and medium-grade ischemic diseases of the heart, endoarteritis and occlusive arteriosclerosis of the vessels of the legs and arms.
• Chronic venous insufficiency, including topical alterations.
• Long-term bronchial asthma and pneumonia.
• Ulcerative diseases of the stomach and duodenum.
• Subacute hepatitis, including viral, and subacute pancreatitis.
• Osteochondrosis.
• Dystrophic and inflammatory diseases of the joints, tubular bone fractures and lower jaw.
• Chronic dermatitis, psoriasis and scleroderma.
• Soft tissue injuries.
• Acute otitis, tonsillitis, toothache and postoperative phlegmons, among others.
Exposure to EMF and incidence in cancer.
One of the biggest concerns within the scientific community. Among the associations found between EMF and different types of cancer, there is a very weak one that relates the use of analog mobile phones and glioma (tumor in nervous tissue), carried out in Finland in 2002, a brain tumor on the side of the head where the telephone carried out in Sweden in 2003 had been used most frequently, a study carried out in Rome in 2002 found a significant increase in the incidence of leukemia in children living near high-power radio stations, said study differs from another conducted in Great Britain in 1997 where some evidence of an increased incidence of leukemia was found in adults but not in children,Likewise, there are studies with found results regarding melanoma of the skin. Finally, although there have been positive findings that relate the risk of the appearance of certain types of cancer with the use of mobile phones or exposure to radiofrequency fields at both occupational and residential levels, there is still no consistent demonstration that relates the magnitude and time of exposure with the response, however they also affirm that the design of the studies has been frequently deficient, in addition, although the studies do not demonstrate a high risk of cancer incidence, neither do they rule out the possibility of occurrence, especially in the face of continued exposure during many years.Finally, although there have been positive findings that relate the risk of the appearance of certain types of cancer with the use of mobile phones or exposure to radiofrequency fields at both occupational and residential levels, there is still no consistent demonstration that relates the magnitude and time of exposure with the response, however they also affirm that the design of the studies has been frequently deficient, in addition, although the studies do not demonstrate a high risk of cancer incidence, neither do they rule out the possibility of occurrence, especially in the face of continued exposure during many years.Finally, although there have been positive findings that relate the risk of the appearance of certain types of cancer with the use of mobile phones or exposure to radiofrequency fields at both occupational and residential levels, there is still no consistent demonstration that relates the magnitude and time of exposure with the response, however they also affirm that the design of the studies has been frequently deficient, in addition, although the studies do not demonstrate a high risk of cancer incidence, neither do they rule out the possibility of occurrence, especially in the face of continued exposure during many years.However, they also affirm that the design of the studies has often been deficient, in addition, although the studies do not demonstrate a high risk of cancer incidence, they do not rule out the possibility of its occurrence, especially in the face of continued exposure for many years.However, they also affirm that the design of the studies has often been deficient, in addition, although the studies do not demonstrate a high risk of cancer incidence, they do not rule out the possibility of its occurrence, especially in the face of continued exposure for many years.
Electromagnetic fields and the human body
The mechanisms of interaction between electromagnetic fields (EMF) and biological structures are naturally evident in the human body with electrical currents, through them nerve impulses communicate, biochemical processes that go from digestion to brain activity.
In humans, it has been shown that static electric fields interact with the body by inducing a surface electric charge, the main mechanism of interaction occurs when a person comes into contact with a charged conducting object, or when there is a potential difference high enough to ionize the air in such a way as to allow electrical conduction between a charged object and a person with good grounding in such a case they could receive an electric shock. These interactions could be very painful, the degree of disturbance depends on the intensity of the field and the level of isolation of the person.
Static magnetic fields interact through the following mechanisms:
Magnetic induction
• Electrodynamic interactions with moving electrolytes
The action of static or variable magnetic fields with time is manifested through the Lorentz Force. This is how the electrical charges that make up the blood (electrolytes), when circulating through the blood vessels with a certain speed, can experience these forces and an electric field that will give rise to a potential difference between the walls of the vessel.
The conduction of nerve impulses can be considered as an ionic flow subjected to the action of the Lorentz Force, under the influence of a static magnetic field. Theoretical models and experiments suggest that below 2T no observable changes occur in the velocity of nerve impulses.
• Faraday currents
Time-varying magnetic fields induce electrical currents in tissues, however the movement (approach or distance) of a static magnetic field also causes a magnetic induction gradient. This is the case of the cardiac muscle, which when contracting when subjected to a static magnetic field, generates gradients in it. The current density induced by the variation of the magnetic field is proportional to the radius of the loop through which the field lines pass, due to this, high densities are expected at the macroscopic level and very low at the cellular level. This is how the movement of a person in a field of 200mT can give rise to an induced current of density (J) between 10 and 100mA / m2, assuming an imaginary loop of 30cm radius.These values are not considered to produce harmful effects on the functioning of the nervous system (ICNIRP criteria).
Electromagnetic fields of frequencies greater than 100Khz
Exposure to EMF generally produces minimal energy absorption, causing a non-measurable increase in temperature, however, above 100Khz, significant energy absorption and temperature increases may occur, which is explained in detail later in thermal interaction..
Due to their effects, the mechanisms of interaction of living matter with EMFs are classified into two categories:
• Thermal: they occur due to the heating of the tissues caused by the direct absorption of energy from the fields and by induced currents as a consequence of Faraday's law.
• Non-thermal: Interaction mechanisms that do not show evidence of temperature rise are the subject of further discussion at this time because they are the ones that present the greatest difficulty of limitation and regulation.
Thermal interaction
They are produced by the direct absorption of energy from fields, the distribution of energy within the body is highly non-uniform and depends on several factors such as the frequency range of radiation and the electrical absorption properties of the human body, which they are quite heterogeneous. According to the energy absorption capacity of the human body, the frequency spectrum can be divided into four ranges:
1. from 100 Khz. up to 20 MHz, significant absorption can occur in the neck and legs.
2. from 20 MHz to 300 MHz, relatively high absorption can occur throughout the body, and in some specific parts of the body according to their resonances.
3. From 300 MHz to several GHz, non-uniform local absorptions may occur.
4. Above 10 GHz, energy absorption occurs mainly at the surface of the body.
The physical quantity that determines the level of energy absorption due to external electric fields is the SAR for its acronym in English (specific energy absortion rate) as its name indicates it is a measure of the specific absorption rate of energy in the human body, its units are watts per kilogram.
Non-thermal effects. They occur when the wave energy is insufficient to raise the temperature above the normal temperature fluctuations of the biological system. There is evidence that prolonged exposures to low intensity radiation are potentially harmful due to the non-thermal effect of radiation exposure.
In EMFs with frequencies below 1MHz there is no significant heating, but they induce currents and electric fields in the tissues, changes in the cholinergic activity of animals that could influence health are observed in alterations of the electroencephalogram, however, Research in this field is limited, in fact the World Health Organization does not pay much attention to non-thermal effects. A large group of North American researchers and those from member countries of the North Atlantic Treaty (NATO) deny the possibility that radio frequency fields provoke any type of biological response that is not of thermal origin. Their fundamental argument is that these types of waves do not generate mutagenic responses and do not influence the initiation of cancers.
Interaction mechanisms
When a person comes into contact with a conductive object present in the field with a different electric potential, causing contact currents, whose magnitude and spatial distribution depend on the frequency, the size of the object and the person and the contact area; In the frequency range up to approximately 100 KHz, the flow of electrical current from an object in the field to the individual's body can lead to stimulation of peripheral muscles and nerves. With the increase in current levels it can manifest as perception, pain from electric shock and burning, inability to release the object, difficulty in breathing and in very high currents cardiac ventricular fibrillation. The threshold values for these effects are frequency dependent, the lowest threshold occurs between 10 and 100 Hz.
Table 1. Threshold current ranges for indirect effects up to 1MHz.
In general, the threshold currents that produce perception and pain have been shown to vary little in the frequency range of 100 KHz to 1 MHz and are unlikely to vary significantly in the frequency range up to about 110 MHz.
Factors Affecting Exposure
Many factors affect the influence that EMF exposure has on living matter both in occupational settings and for the general public, including:
- The output power, frequency and type of source The distance of the person from the source The location of the person from the source The type of antenna and the direction of the emitted wave The presence of objects that can reflect the fields or shield people from them Exposure time.
Table 2: Exposure limits at the occupational level
Conclusions
Biological tissues present variations in electrical characteristics when the frequency of the applied field increases or decreases.People who work in high-voltage and high-frequency installations that are exposed to a significant level of electromagnetic charge (EMF) require a clear delimitation as an area of occupational exposure to electromagnetic fields in order to protect human health according to their level and exposure time, which implies having and taking safety and health measures at work that allow the technical development in this area to be compatible field with the human body. There are advantages in the effects of EMFs, so they can be used in the treatment of diseases, in therapeutic processes such as biostimulant, analgesic,anti-inflammatory and anti-oedematous.
Bibliography
1. Barnes FS. Interaction of DC and ELF electric fields with biological materials and systems. In: Polk C, Postowe, eds. Handbook of Biological Effects of Electromagnetic Fields. 2 ed. Boca Raton: CRC Press, 1996: 103-47.
2. Hossman KA, Herman DM. Effect of electromagnetic radiation of mobile phones on the central nervous system. Bioelectromagnetics. 2003; 24 (1): 49-62.
3. National Radiological Protectio Board Advice on Limiting Exposure to Electromagetic Fields (0-300 GHz) Doc. NRPB volume 15 N ° 2, 2004
4. National Radiological Protectio Board Review of the Scientific Evidence for Limiting Exposure to Electromagnetic Fields (0-300 GHz) Doc. NRPB volume 15 N ° 3, 2004.
5. Domenico Formica and Sergio Silvestri Biological effects of exposure to magnetic resonance imaging, Biomedical Engineering OnLine, April 22, 2004..
Available at
6. Unidad Ecológica Salvadoreña Cellular Telephony and Electromagnetic Pollution:
7. Impacts on Human Health and Proposals for Regulation in El Salvador, April 2002.
8. World Health Organization, Establishing a Dialogue on the Risks of Electromagnetic Fields, 2001
9. European Parliament, Electromagnetic Fields and Health, Informative Note No. 5, 2001.
Available at www.europarl.eu.int/stoa/publi/pdf/briefings/05_es.pdf
10. Ministry of Labor and Social Affairs of Spain, Exposure to Static Magnetic Fields, Technical Note of Prevention 598, 2002.
11. Ministry of Labor and Social Affairs of Spain, Electric current: effects when passing through the human organism, Technical Note of Prevention 400, 2002.
12. Environmental Health Perspectives, Epidemiology of Health Effects of Radiofrequency
13. Exposure, volume 112, number 17, December 2004.
14. International Commission on Non-ionizing Radiation Protection, Recommendations to Limit Exposure to Electric and Magnetic Fields and Electromagnetic (up to 300 GHz) 1988; 54 (1): 115-23.
15. Ministry of Communications of Colombia, Decree 195 by which limits of exposure of people to electromagnetic fields are adopted, procedures are adapted for the installation of radio stations and other provisions are issued, January 31, 2005.
16. Portales M Electromagnetic pollution and health. Accessed February 2009. Available at:.
17. The Royal Society of Canada, Recent Advances in Research on Radiofrequency Fields and Health, 2003.
18. International Telecommunications Union, Guidance on complying with limits for human exposure to electromagnetic fields, ITU-T K.52, December 2004.
