Bioeffects of weak electromagnetic fields

Time varying magnetic fields are most often employed for therapeutic purposes and are present in environmental sources. In order for an electromagnetic field bioeffect to be possible, the signal parameters should not only satisfy the dielectric properties of the target, but also induce sufficient voltage to be detectable above thermal noise. The problem of the sensitivity of living cells and tissues is discussed in relation to signal/noise ratio at the target site. Some biophysical models for interactions of weak electromagnetic fields with biological systems are summarized. Cell studies and therapeutic application of electric and magnetic fields indicate that weak electromagnetic fields can have a profound effect on a large variety of biological systems.