Bioelectric background fields and their implications for ELF dosimetry

Electrically active cells, such as those comprising nerve, muscle, or bone, produce ELF currents not only across themselves but also in the surrounding tissue including the tight extracellular spaces between cells. An analysis based on "cable models" of neurons or muscle cells is herein used to estimate those extracellular (or "pericellular") current densities. In order to explore frequency bands the neural or muscle action potentials are represented by a Fourier series of sine wave components. The results of this analysis suggest that endogenous currents in, or near, nerve and muscle are far stronger (higher density) than currents likely induced by exogenous ELF fields--such as 1 microT, 60 Hz magnetic fields. This holds true even for "higher harmonics" including those at or near 60 Hz.