Microwave Absorption by Magnetite: A Possible Mechanism for Coupling Nonthermal Levels of Radiation to Biological Systems
The presence of trace amounts of biogenic magnetite (Fe_3O_4) in animal and human tissues and the observation that ferromagnetic particles are ubiquitous in laboratory materials (including tissue culture media) provide a physical mechanism through which microwave radiation might produce or appear to produce biological effects. Magnetite is an excellent absorber of microwave radiation at frequencies between 0.5 and 10.0 GHz through the process of ferromagnetic resonance, where the magnetic vector of the incident field causes precession of Bohr magnetons around the internal demagnetizing field of the crystal. Energy absorbed by this process is first transduced into acoustic vibrations at the microwave carrier frequency within the crystal lattice via the magnetoacoustic effect; then, the energy should be dissipated in cellular structures in close proximity to the magnetite crystals. Several possible methods for testing this hypothesis experimentally are discussed. Studies of microwave dosimetry at the cellular level should consider effects of biogenic magnetite.
© 1996 Wiley-Liss, Inc. Received for review October 25,1994; revision received September 22,1995. Article first published online: 6 Dec 1998. The author is grateful for support from EPRI project WO 4307-03 and NIH grant ES-06652 during the development of these ideas. Helpful discussions with many friends and colleagues are also acknowledged along with the lengthy comments of three referees and the Assistant Editor.