Action Potential Threshold Variability for Different Electrostimulation Models and the Impact on Occupational Exposure Limit Values

ABSTRACT Occupational exposure limit values (ELVs) for body internal electric fields can be derived from thresholds for action potential generation. These thresholds can be calculated with electrostimulation models. The spatially extended nonlinear node model (SENN) is often used to determine such thresholds. An important part of these models are the membrane channel dynamics describing the ionic transmembrane currents. This work shows how ELVs change significantly with different ion channel dynamics (up to a factor of 22). Furthermore, two more detailed double-cable models by Gaines et al. (MRG-Sensory and MRG-Motor) are also considered in this work. Thresholds calculated with the SENN model (with Frankenhaeuser-Huxley membrane channel dynamics) and the MRG models are compared for frequencies between 1 Hz and 100 kHz and temperatures between 22 °C and 37 °C. Results show that MRG thresholds are lower than SENN thresholds. In the context of occupational ELVs, using the double cable model would lead to approximately ten times lower limit values. Therefore, future exposure guidelines should take the influence of different electrostimulation models into account when deriving ELVs. Highlights Different membrane channel dynamics change derived exposure limit values by more than one order of magnitude. Double-cable models result in a reduction of derived exposure limit values by one order of magnitude. Lower temperatures reduce the action potential thresholds at frequencies below 300 Hz.