Bioelectromagnetics

Bioelectromagnetics is the study of how electromagnetic fieldsinteract with and influence biological processes. Common areas of investigation include the mechanism of animal migration and navigation using the geomagnetic field, studying the potential effects of man-made sources of electromagnetic fields, such as those produced by the power distribution systemand mobile phones, and developing novel therapies to treat various conditions.

While several treatments based on the use of magnetic fields have been reported in peer-reviewed journals, the only ones that have been approved by the FDA are the use of pulsed magnetic fields to aid non-union bone fractures. Transcranial magnetic stimulationis currently under active study in multiple research centres, and will likely become an approved therapy in the future.

Introduction: general features of observed interactions

Thermal vs nonthermal nature

Most of the molecules that make up the human body interact only weakly with electromagnetic fields(EMF) that are in the radiofrequencyor extremely low frequencybands. One basic interactiion is the absorption of energy from the EMF, which can cause tissue to heat up; more intense field exposures will produce greater heating. This heat deposition can lead to biological effects ranging from discomfort to protein denaturation to burns. Many nations and regulatory bodies (for example, the International Commission on Non-Ionizing Radiation Protection) have established safety guidelines to limit the EMF exposure to a non-thermal level, which can either be defined as heating only to the point where the excess heat can be dissipated/radiated away, or as some small temperature increase that is not detectable with current instruments (such as a heating of less than 0.1°C).

However, some research has indicated that biological effects may be present for these non-thermal exposures. Various mechanisms have been proposed to explain non-thermal exposures, and there may be several mechanisms at work underlying the differing phenomena observed.

Noise-masking, time and space integration, cooperativity

Intrinsic fields

Natural fields

Primary interaction mechanisms

Membrane polarization

Electrorotation

Ion cyclotron resonance (and ion parametric resonance)

Nonlinear kinetics

Frohlich-style macro dipole interactions

DNA conduction

Microtubule waveguides

Ferromagnetic domains

Frequency selectivity from spatial features

Effects on the level of a cell or below

Calcium efflux

Neurotransmitter systems

DNA strand breaks and genotoxicity

Ornithine decarboxylase

Melatonin

Bacterial growth and metabolism

Effects on the level of an organ or system

Blood-brain barrier permittivity

EEG changes

Wound healing, regeneration and bone growth

Cancer promotion

Whole-organism effects

Electrical sensing organs (fish, etc)

Navigation (bees, pidgeons, etc)

Effects on embryonic development

Behavioral effects

Many subtle, and at times, not-so-subtle effects on behaviour have been reported from exposure to magnetic fields, with a particular focus in research on pulsed magnetic fields. The specific pulseform used appears to be an important factor for the behavioural effect seen. For instance, a pulsed magnetic field originally designed for magnetic resonance spectroscopic imaging was found to alleviate symptoms in bipolar patients (Rohan et al, 2004), while another MRI pulse had no effect. A whole-body exposure to a pulsed magnetic field was found to alter standing balance (Thomas et al, 2001) and pain perception (Shupak et al, 2004) in other studies.

Effects of artificial fields

Powerlines

CRTs

Cell phones

Radar

Other transmitters (radio, TV, ...)

Medical applications

Bone fracture healing

TMS (and related)

A strong changing magnetic field can induce electrical currents in conductive tissue, such as the brain. Since the magnetic field will penetrate tissue, it can be generated outside of the head to induce currents within, hence Transcranial magnetic stimulation. These currents will depolarize parts of the brain, leading to changes in the patterns of neural activation. Essentially, it is a form of electroconvulsive therapyusing induced currents from strongly changing magnetic fields rather than inserted electrodes. This type of controlled siezure can be useful in treating disorders such as severe depression, or as a tool for inducing localized brain activation in functional imaging studies.

Low-level Laser Therapy (LLLT)

Strong magnetic pulses for disinfection

Other

See also

Bioelectromagnetism

Biophysics

Unsolved problems in biology

Specific absorption rateand Electromagnetic radiation hazard.

Mobile phone radiation and health

References

Organizations

• The Bioelectromagnetics Society(BEMS)
• European BioElectomagnetics Association(EBEA)
• Society for Physical Regulation in Biology and Medicine(SPRBM) (formerly the Bioelectrical Repair and Growth Society, BRAGS)

Books

• Robert O. Becker and Andrew A. Marino, Electromagnetism and Life, State University of New York Press, Albany, 1982 (ISBN 0873955617)
• Robert O. Becker, The Body Electric: Electromagnetism and the Foundation of Life, William Morrow & Co, 1985 (ISBN 0688001238)
• Robert O. Becker, Cross Currents: The Promise of Electromedicine, the Perils of Electropollution, Tarcher, 1989 (ISBN 0874775361)
• Jaakko Malmivuo and Robert Plonsey, Bioelectromagnetism: Principles and Applications of Bioelectric and Biomagnetic Fields, Oxford University Press, 1995 (ISBN 0195058232)
• David O. Carpenter and Sinerik Ayrapetyan, Biological Effects of Electric and Magnetic Fields, Volume 1 : Sources and Mechanisms, Academic Press, 1994 (ISBN 0121602613)
• David O. Carpenter and Sinerik Ayrapetyan, Biological Effects of Electric and Magnetic Fields : Beneficial and Harmful Effects (Vol 2), Academic Press, 1994 (ISBN 0121602613)
• A. Chiabrera (Editor), Interactions Between Electromagnetic Fields and Cells, Springer, 1985 (ISBN 030642083X)
• Mary E. O'Connor (Editor), et al, Emerging Electromagnetic Medicine, Springer, 1990 (ISBN 0387972242)
• William F. Horton and Saul Goldberg, Power Frequency Magnetic Fields and Public Health, CRC Press, 1995 (ISBN 0849394201)
• Riadh W. Y. Habash, Electromagnetic Fields and Radiation: Human Bioeffects and Safety, Marcel Dekker, 2001 (ISBN 0824706773)
• Ho Mae-Wan, et al, Bioelectrodynamics and Biocommunication, World Scientific, 1994 (ISBN 9810216653)
• Paul Brodeur, Currents of Death, Simon & Schuster, 2000 (ISBN 0743213084)

Journals

• Bioelectromagnetics, Wiley, 1985-present, (ISSN 0197-8462)
• Bioelectrochemistry, Elsevier, 1974-present, (ISSN 1567-5394)
• BioMagnetic Research and Technology [1]
• Biofizika ("Biophysics", in Russian) (ISSN 0006-3509)
• Radiatsionnaya Bioliogiya Radioecologia ("Radiation Biology and Radioecology", in Russian) (ISSN 0869-8031)

Journal Articles

• Rohan et al., 2004. Am J Psychiatry. 161(1):93-8.
• Shupak et al., 2004. Neurosci Lett. 363(2):157-62.
• Thomas et al., 2001. Neurosci Lett. 309(1):17-20.

External links

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It uses material from the http://en.wikipedia.org/wiki/Bioelectromagnetics Wikipedia article Bioelectromagnetics.