Magnetobiology is the study of biological effects of mainly weak static and low-frequency magnetic fields, which do not cause heating of tissues. Magnetobiological effects have unique features that obviously distinguish them from thermal effects; often they are observed for alternating magnetic fields just in separate frequency and amplitude intervals. Also, they are dependent of simultaneously present static magnetic or electric fields and their polarization.
Magnetobiology is a subset of bioelectromagnetics. Bioelectromagnetism and biomagnetism are the study of the production of electromagnetic and magnetic fields by biological organisms. The sensing of magnetic fields by organisms is known as magnetoreception.
Biological effects of weak low frequency magnetic fields, less than about 0.1 millitesla (or 1 Gauss) and 100 Hz correspondingly, constitutes a physics problem. The effects look paradoxical, for the energy quantum of these electromagnetic fields is by many orders of value less than the energy scale of an elementary chemical act. On the other hand, the field intensity is not enough to cause any appreciable heating of biological tissues or irritate nerves by the induced electric currents.
An example of magnetobiological effects is the magnetic navigation by migrant animals. It is established that some animals are able to detect small variations of the geomagnetic field on the order of tens of nanoteslas to find their seasonal habitats.
The results of magnetobiological experiments are poorly reproducible. 10–20% of publications report failed attempts to observe magnetobiological effects. In the majority of experiments, success depended on a rare happy coincidence of suitable electromagnetic and physiological conditions. Many of the experiments await confirmation by independent studies.
Practical significance of magnetobiology is conditioned by the growing level of the background electromagnetic exposure of people. Some electromagnetic fields at chronic exposures may pose a threat to human health. World Health Organization considers enhanced level of electromagnetic exposure at working places as a stress factor. Present electromagnetic safety standards, worked out by many national and international institutions, differ by tens and hundreds of times for certain EMF ranges; this situation reflects the lack of research in the area of magnetobiology and electromagnetobiology. Today, the most of the standards take into account biological effects just from heating by electromagnetic fields, and peripheral nerve stimulation from induced currents.
Practitioners of magnet therapy attempt to treat pain or other medical conditions by relatively weak electromagnetic fields. These methods have not yet received clinical evidence in accordance with accepted standards of evidence-based medicine. Some institutions recognize the practice as a pseudoscientific one. Other institutions, such as NASA, use magnet technology for biological regenerative effects of bone in mammals.
Possible causes of the effects
In magnetobiology, theory is lagging far behind experiment. The nature of biological effects of weak electromagnetic fields remains unclear as yet, despite numerous experimental data. The following suggested causes of magnetobiological phenomena are frequently discussed:
- Crystallization of iron-bearing magnetic nanoparticles in tissues of the organism,
- Dependence of some biochemical free-radical reactions on the magnetic field magnitude,
- Possible existence of long-lived rotational states of some molecules inside protein structures,
- Magnetically induced changes in physical/chemical properties of liquid water.
Explanation of the physical nature of biological effects of weak magnetic fields is a fundamental scientific problem.
Profile scientific journals
- Electromagnetic radiation and health
- Transcranial magnetic stimulation
|This article does not cite any references or sources. (October 2011)|
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