Biological Effects of Stationary Magnetic Fields

123

Using biophysical criteria, I show that continuous radiofrequency (RF) and microwave radiation with intensity less than 10 mW/cm(2) are unlikely to affect physiology significantly through athermal mechanisms. Biological systems are fundamentally noisy on the molecular scale as a consequence of thermal agitation and are noisy macroscopically as a consequence of physiological functions and animal behavior. If electromagnetic fields are to significantly affect physiology, their direct physical effect must be greater than that from the ubiquitous endogenous noise. Using that criterion, I show that none of a set of interactions of weak fields, which I argue is nearly complete on dimensional grounds, can affect biology on the molecular scale. Moreover, I conclude that such weak fields are quite unlikely to generate significant effects in their interactions with larger biological elements such as cells. In the course of that analysis, I examine important special examples of electromagnetic interactions: "direct" interactions where biology is modified simply by the motion of charged elements generated by the electric field; resonance interactions; the effects of electrostrictive forces and induced dipole moments; and modifications of radical pair recombination probabilities. In each case, I show that it is unlikely that low intensity fields can generate significant physiological consequences.

Section: Opening Of Voltage Gated Channelsmentioning

confidence: 99%

Biophysical limits on athermal effects of RF and microwave radiation

Adair

2002

123

“…The majority of this interest has focused on whether or not there are reproducible, harmful or bene®cial effects of AC (time varying) EMF-induced exposures which could in¯uence human health [Saffer and Phillips, 1996;Reiter and Richardson, 1992]. In addition, many scienti®c reports describe potentially important DC (static) magnetic ®eld reactions with biological indicator systems in vivo and in vitro [Tenforde, 1990], ranging from bacteria to insects and birds to mammals [Singh et al,1994;Frankel, 1986;Berk et al, 1997].…”

Section: Introductionmentioning

confidence: 99%

Increased antibiotic resistance ofE. coli exposed to static magnetic fields

Stansell

Winters

Doe

et al. 2001

The present study demonstrates that exposure of bacteria to medium strength static magnetic fields can significantly alter antibiotic sensitivity. Cultures of Escherichia coli were exposed to fields produced by permanent magnets. Samples of bacterial cultures continuously growing in the presence and in the absence of static magnetic fields were left untreated or were treated with an antibiotic and measured at 45 min intervals for cell growth and survival. It was found that exposure of E. coli to the static fields significantly increased antibiotic resistance. Bioelectromagnetics 22:129-137, 2001. Published 2001 Wiley-Liss, Inc.

“…In general, the results were as follows. On one hand, the authors reported no effects of moderateintensity (1 mT-1 T) or strong-intensity (1-5 T) SMF exposure on action potential conduction velocity, ionchannel currents [Schwartz, 1978[Schwartz, , 1979, and electroretinogram responses [Tenforde et al, 2005]. These negative findings seem to support the conclusion of Wikswo and Barach [1980], that ultrastrong (24 T and above) magnetic flux densities are required to produce neurophysiological changes, especially in axonal conductivity.…”

Section: Introductionmentioning

confidence: 90%

Exposure to an inhomogeneous static magnetic field increases thermal pain threshold in healthy human volunteers

Kovács-Bálint

Csathó

László

et al. 2010

In the present experiment, the effect of a single 30 min inhomogeneous static magnetic field (SMF) exposure on thermal pain threshold (TPT) was examined in 15 young healthy human volunteers. The SMF had a maximum peak-to-peak amplitude of 330 mT with a maximum gradient of 13.2 T/m. In either of two experimental sessions (SMF or SHAM), four blocks of 12 TPT trials were carried out under SMF or SHAM exposure on all fingertips of the dominant hand, excluding the thumb. TPT and visual analog scale (VAS) data were recorded at 0, 15, and 30 min exposure time, and 30 min following exposure. SMF treatment resulted in a statistically significant increase in TPT during the entire exposure duration and diminished within-block thermal habituation, leaving pain perception unchanged. These results indicate that SMF-induced peripheral neuronal or circulatory mechanisms may be involved in the observed TPT increase by setting the pain fibre adaptation potential to higher levels.