Electromagnetism and human health

image credit:http://iactafool.com

Since man appeared on the planet has lived with the magnetic fields of the earth and electromagnetic fields from outer space, which probably had and have influence on various biological functions. As a result of technological progress leading to an increase in the use of electricity in the last century humans are increasingly exposed to extremely low electromagnetic fields (EMF) in particular frequency 50-60 Hz, similar to the produced by power lines and a variety of household appliances. Moreover, occupationally exposed to magnetic fields include, among others, MRI operators, radar and radio, specialized facilities and biomedical physics, electrical workers casting and electrolytic processes

In the late seventies were works that suggested the association between EMF and cancer, particularly childhood leukemia. Since then they have done a lot of studies, both epidemiological and laboratory, to try to establish a possible link between EMF exposure and human disease. In this review, we will try to give an approximation to the current context of the controversy has been about the potential risk posed by being under the influence of magnetic fields and if this could become a public health problem. A summary of the experience of seven years of work we have investigated the biological effect of magnetic fields is also presented.

Physics Electromagnetic Fields

Wood , it states that at the time of Thales (640 -. 546 BC), the man spoke of magnetic attractions. For over two thousand years ago, the Chinese used the magnetic compass to orient themselves in their sea voyages and the deserts of Mongolia. As is known, the foundation of the compass is to adopt an orientation, which is given by a peripheral magnetic field.

And in modern times, the Danish physicist Hans Christian Oersted, in 1820, observed that the orientation of the needle of a compass can be changed by the action of an electric current in a similar way as it did a magnet. This led him to think about an electron conducting a field which manifests itself as a magnet, as well as being associated with magnetism electricity is formed.

A magnetic field is defined as the region in space in which a magnetized object can, in turn, magnetized to other bodies. According to the distribution of intensity you can be classified into:

Homogeneous: where the field strength is uniform.

Heterogeneous: where the intensity decreases proportionally to the distance from the center.

And according to whether they are constant or variable over time are classified as:

Static: the lines of force and direction are constant over time.

Spherical: the load switches in each pulse while the intensity also varies.

Considering both classification criteria, the effect of magnetic fields on various biological systems depend on whether it is homogeneous, heterogeneous, static or oscillating .

Furthermore, an electric field is caused by static electrical charges. When the magnetic and electric field in a region vary in time, both are related such that all electric field varies with time, always accompanied by an also variable and vice versa magnetic field, therefore, the so-called electromagnetic field is summarized by Parker as the relationship between electric and magnetic fields in a single physical entity.

According to Stewart ,in general for transmission of alternating current (AC), in North America, the rate is 60 Hertz (Hz) and Europe and other regions, is 50 Hz, often understood as the number of full cycles per unit time. In the International System of Units 1 cycle / 1 sec. equals 1 Hz.

Moreover, in a magnetic field force it is given by the magnetic flux density (also called magnetic intensity), this being the number of lines of force passing per unit area. The unit in the sexagesimal system for the magnetic intensity is Oersted (Oe) established in 1932 by international agreement, as a substitute for Gauss (G) but still used the latter's literature. International System of Units the magnetic flux density is given in Tesla (T), where each T is equivalent to 10,000 G.

In turn, the intensity of a magnetic field depends not only on an electrical variable, but also of the distance, its magnitude is directly related to the current flow (measured in amperes) and is inversely proportional to the square of the distance. Similarly, the magnitude of the electric field is in direct proportion to voltage and decreases as the distance increases .

Biological Effects of Magnetic Fields

Because the electrolyte composition living beings are generally good conductors of electricity. Through cell membranes and intracellular and extracellular body fluids are ionic currents, particularly in nerve and muscle cells which must be associated a magnetic field. Also, biological systems are magnetically influenced structures as free radicals having paramagnetic properties and those involved in ferromagnetic substances. The response of a biological system to an external magnetic field depends on the intrinsic magnetic properties of the system and the characteristics of the external field and the properties of the medium in which the phenomenon takes place.

Experiments have proven that the changes they undergo some parameters of biological systems by the action of magnetic fields influence not only the intensity but also the spatial and temporal characteristics of the field. Within this context is different the effect of a static field, which only produce a rotating magnetic dipoles tend to orient in the direction of the field and restricting their mobility, thus causing a significant effect if they participate in chemical reactions. In contrast, an oscillating field having periodic variations in time and superimposed movements can induce oscillation of the molecular dipole magnets, may affect the rate of chemical reactions depending on the amplitude, frequency and direction of the magnetic field variations . In scientific literature, many papers tested the effect of magnetic fields on enzymatic reactions in vitro, giving a qualitative and quantitatively different effects depending on the reaction in question and the characteristics of the field.

Moreover, in living things that move within a magnetic field like Earth's, a potential difference can alter motility is induced. Although the geomagnetic field is relatively weak, these effects have been observed in elasmobranchs. Are known to have sharks and rays based on electromagnetic induction to navigate and locate prey mechanisms and the intensity of the magnetic field can be a limiting factor in the responsiveness of the subject. It is also proposed that migratory birds have a mechanism for navigation guidance based on the generation of electrical potentials induced electromagnetically. It has also been found that some microorganisms, particularly bacteria, have the ability to guide its movement in response to an external magnetic field (magnetotactismo), these bacteria contain one or two chains rich intracellular iron particles. Also described magneto sensibilidad properties for a variety of migratory insects and even in humans, although the latter finding is controversial.

Moreover, radio waves and some types of ultraviolet light, are some non-ionizing radiation to which man is often exposed. The biological effects of the former are currently being determined, while the harm of ultraviolet light in the DNA has been linked to the formation of thymine dimers, which is the most frequently injury induced by this radiation, usually these damages are removed by cells through excision repair mechanisms. If the exposed cells are not efficient in this type of repair, DNA damage and cell remain undergo considerable changes as in the case of Xeroderma pigmentosum and skin cancer .

Furthermore, non-ionizing radiation frequency is extremely low as the case of 60 Hz magnetic fields have been shown to have effects on biological systems and it is reported that these can affect the rate of reactions and a large amount of biochemical processes . Also, it has been reported that EMFs have effects on the synthesis of DNA, RNA and proteins, changes in hormone production; modification of the immune response and the degree of cell growth and differentiation.

Furthermore, we have obtained experimental evidence suggesting that EMFs affect growth and proliferation in several cell types.

From the physical point of view, it has proven to be the electric field induced by the variable magnetic field which determines the cellular response. However, the influence of a static magnetic field added to the variable field, also has been demonstrated, so that the mechanism of interaction is more complex than the mere influence of induced electrical fields. It is assumed that the primary interaction occurs in the cell membrane and more specifically in ion channels, calcium being the most actively participating in biological alterations .

Also it assessed the effect of electric fields in embryos. In one study, C3H / He male mice were exposed to an electric field of 20 kV / m to 50 Hz frequency for two weeks. Then each male mouse was mated with 2 different weekly females over a period of 8 weeks for females they were fertilized by mice that had been exposed to the electric field and no alterations in the survival of embryos were found.

In another study Nordstrom et al. found an increase in the frequency of birth defects in children whose parents worked in the high voltage generating sources, which could indicate a genetic effect level of EMF.

Moreover, it is well known that the EMC can produce a variety of beneficial effects in biological systems. The pulsating magnetic fields for example, are used for repairing bone fractures; Andrew and Basset  showed that the bone tissue is sensitive to magnetic and electric fields of low frequency. First, the tissue was subjected to a variable magnetic field and low frequency detected in the tissue a current is induced as the voltmeter was modified in the presence of said field. Thus the study of the possible use of magnetic fields for the therapy of persistent fractures and in some cases, onset of osteoporosis.

Electromagnetic Fields and Cancer

Recently discussed the possible association of exposure to EMF with the development of acute leukemia and has proposed a relationship between the form of exposure in children and adults magnetic field, however, they have not been well defined as these physical agents causing disease.

Also, several epidemiological studies have correlated human exposure to electromagnetic fields with a high incidence of cancer.

In contrast, Costa and Hoffmann , they discovered that high intensity magnetic fields in the range 1 to 50 G, with a frequency of 5 to 1000 KHz, reduce the concentration of malignant cells in animal tissue. Usually for cancer treatment, the diseased tissue is subjected from 1 to 1000 pulses of 100 msec duration at a second depending on the type of tumor. The effect of this treatment is to reduce the number of malignant cells; after chemotherapy is applied. The advantage is that no heat is generated in tissue and normal tissue but also suffers alteration; change is minor compared to the effect on cancer cells. In addition, cells of the immune system are not affected by the treatment so the net effect on the body is favorable.

On the other hand, they have been postulated theories about the possibility of carcinogenesis associated with EMFs. Thus, Fitzgerald ,proposed a mechanism to explain the formation of a tumor due to this cause in which there are at least two steps: 1) initiation stage in which DNA is damaged by an external agent, producing DNA resulting in abnormal and abnormal protein expression. For initiation enough energy is required to break the chemical bonds of DNA (more than they can provide CEM to which we are regularly exposed). promotion stage, which is the latency period between exposure to a carcinogen and the appearance of cancer. According to the above EMF act more like promoters and initiators as accelerate the development process rather than induce cancer directly.

In an experimental study mammary tumors were induced in rats using the dimethylbenzanthracene (DMBA) to a group of 99 female rats then exposed to magnetic fields of 100 m T for 24 hours daily for 7 days; another group of 99 rats was used as a control under the same environmental conditions as the group exposed to treatment. The results showed that those treated with DMBA and exposed for long periods to the magnetic field, and rats showed an increase incidence greater than the group not exposed to the magnetic field malignant breast tumors.

Furthermore it has been observed that when cultured cancerous cells are exposed magnetic fields, a significant acceleration in cell growth, which continued at a rapid rate even after exposure to the magnetic field presented. Also, in rats in which the formation of chemically induced mammary tumors is found to exhibit greater tumor growth when low frequency magnetic fields were exposed

Moreover, it has been suggested that the risk of childhood leukemia may be related to the combined effects of static magnetic fields and magnetic fields of extremely low frequency (34). Also in another study (35), it has been suggested that EMFs are related to cancer, to this, peripheral blood cultures were incubated in the presence of a CEM of 5 mT and 50 Hz frequency. The results showed that the carcinogenic effects caused by EMF non-starter type, but probably have promoting effects.

Genetic Effects of Electromagnetic Fields

There is to date a general consensus on the genotoxic effect attributed to exposure to EMF of 60 Hz, however there have been several studies that include a variety of biological models, for example in research were exposed to Salmonella pretreated typhimurium with azide (chemical mutagen) to a CEM 2 Gauss and 60 Hz frequency, and an increase of 14% was found in the rate of mutation.

Furthermore, Koana et al. estimated the genetic effects of magnetic fields on the fruit fly Drosophila melanogaster. Young larvae of both normal and mutant genotypes were exposed to a uniform magnetic field of 0.6 T for 24 h, and then were left to continue development under normal cultivation and finally emerge at pupal stage. After hatching the survivors they were counted and found that the number of adult mutant genotype, increased approximately 8% compared with the control group, suggesting that the static magnetic field causes DNA damage level eliminating larval cells homozygous recessive.

Regarding the effect on chromosomes, Nordenson et al. human amniotic cells exposed to a sinusoidal magnetic field of 50 Hz and 30μT for 72 h and found an increase in the frequency of chromosome aberrations compared to an unexposed group.

In contrast Galt et al. (39) tested the effect of a CEM 50 Hz 30μT on human amniotic cells for a period of three days exposure, in order to confirm the experiments conducted by Nordenson et al in which the chromosome breakage and formation gaps was relatively high after exposure. But they found no increase in chromosome damage in cells exposed to electromagnetic fields.

In a related study to the above, a significant increase of SCA was found when exposed peripheral lymphocytes cultured bovine EMC 50 Hz. It was also observed an increase in the number of chromosomal aberrations in mouse tumor cells after exposure to electrostatic and in lymphocytes exposed to microwaves  fields.

In another study, lymphocyte cell lines from patients with chromosomal instability syndromes 1-2 Gauss magnetic fields of 60 Hz were exposed, and found no effect on the frequency of sister chromatid exchange and chromosome breakage .

On the other hand, in another study human peripheral lymphocytes of 32 workers occupationally exposed to transformers that generate strong magnetic fields for more than 20 years and no changes were found in the frequency of chromosomal aberrations or the sister chromatid exchange  were analyzed.

Moreover, in another related study, human lymphocytes in vitro to 2.5 mT electromagnetic fields were exposed. And the results showed no genotoxic effect caused by the same.

Moreover Rosenthal and Obe  exposed peripheral CEM human cells and found that did not alter the frequency of spontaneous sister chromatid exchange and chromosomal aberrations, but when cells were subjected previously exposed to chemical mutagens action of EMF, a frequency of sister chromatid exchange was found higher than when they were in the presence of chemical mutagen, but in the absence of the magnetic field, suggesting a synergistic effect.

In another study the in vitro effects of pulsed electromagnetic fields 10, 20 and 40 Gauss for 48 hours on human peripheral lymphocytes was studied using cytogenetic testing of sister chromatid exchange and found no statistically significant difference between groups at CEM and the control .

But Khalil and Qassem  human lymphocytes exposed to EMF of 1.05 mT and 50 Hz for 24, 48 and 72 h and found decreased mitotic activity and a high rate of chromosomal aberrations.

Moreover, human lymphocytes exhibitions were held to electric fields (0.5,2.0,5.0 kV / m) from 50 Hz to see if they produced genotoxic effects (studying micronucleus formation) in vitro. It was found that electric fields of 50 Hz frequency not exert genotoxic effects at the chromosomal level.

In another study conducted in humans, the frequency of chromosomal aberrations, sister chromatid exchange, index replication and micronuclei in peripheral lymphocytes of 27 samples of workers from high voltage sources, which had prolonged periods of exposure to EMF was determined 50 Hz and 27 samples of workers of the telephone line that served as a reference group. What we got was that there were no statistically significant differences between groups in the analysis of sister chromatid exchange, index replication or micronucleus formation. However, an increase in chromosome breakage in workers high voltage sources compared to the control group was observed, so it is suggested that exposure to EMF 50 Hz is associated with an increase in breaking chromatids .

Assessment of Cytotoxic and genotoxic potential of 60 Hz electromagnetic fields.

In recent years, he has worked in the physics laboratory of the School of Biological Sciences at the Autonomous University of Nuevo Leon, on a long-term project that aims to evaluate the genotoxic risk and / or cytotoxic associated with exposure to EMF Spherical 60 similar to those generated by power lines, substations and distribution devices generally powered by electricity from alternating current network and our surrounding environment, in mammalian cells Hz. The influence of magnetic fields was measured in cultured human lymphocytes at intensities of 1.0, 1.5 and 2.0 mT and an increase in cell proliferation, mitotic and evaluated for proliferative index was observed. Also we evaluated the effect of EMF in circulating blood cells in vivo and found that mouse lymphocytes and neutrophils is decreased in response to an increase similar to that for the case of in vitro lymphocyte magnetic treatment. It has also been studied in our laboratory the clastogenic effect on bone marrow cells in vivo mouse and an increase in the frequency of micronucleated cells was found, which is indicative of chromosomal breaks in animals treated with the magnetic intensities aforementioned However, to study the effects of this physical factor on germ cells in vivo mouse breeding, not cytotoxic or genotoxic when assessing meiotic chromosome aberrations and morphological alterations of sperm cells effect was found. The acute effects of EMF 1.0 mT 60 Hz on ex vivo murine macrophage and lymphocyte functions and growth of tumor cells recently studied and no change was detected as compared to untreated animals .

Conclusion

Based on the above, you cannot say conclusively that electromagnetic fields can be regarded as a widespread public health problem; however, there is enough evidence that these fields represent a form of energy that should be avoided. Recently it has been postulated that the magnetic fields of the environment play a role in altering gene which can have adverse effects on human health (54) expression. It has also been said that the great variability and controversial results, is that there are too many variables involved and not all experiments were performed with the necessary rigor.

On the other hand, it is clear that over time has been increasing the number of physical and chemical agents to which we are exposed as a result of technological and industrial development; consequently also it increased public interest in the possible negative effects for health may have exposure to these factors. While, for a lot of these (pesticides, heavy metals, ionizing radiation, etc.) have already been proven adverse health effects, there are other agents that are the subject of much controversy because their effects have not been determined clearly, as noted above about exposure to extremely low frequency EMF.

The research results presented here, including our own experience suggests that magnetic fields are capable of modifying cellular activities, and that this should be considered in estimating the potential risk of an occupational or environmental exposure to these physical agents.

Summary

In this review, it gives an approximation to the current context of the controversy has been about the potential risk posed by being under the influence of magnetic fields and if this could become a public health problem. The research results presented here suggest that magnetic fields are capable of modifying cellular activities, and that this should be considered in estimating the potential risk of an occupational or environmental exposure to these physical agents