Human acute neurophysiological perceptions associated with ELF flux densities up to 50 mT

Current guidelines and recommendations limiting human exposure to extremely low frequency (ELF) magnetic field (MF) are based on the most reliable acute human neurophysiological exposure responses. However, the currently available perception thresholds are established on small sample size and non-replicated experiments. The current human study aimed to test MF levels leading to mahnetophosphenes perceptions at 20, 50, 60 and 100 Hz. Perception reported button-press were recorded in these 4 frequency groups in 55 randomly assigned magnetic flux density conditions. Results showed a frequency-dependent threshold for initial perception: 2.51 T/s at 20 Hz, 6.28 T/s at 50 Hz, 7.54 T/s at 60 Hz, and 12.57 T/s at 100 Hz; and for the 50% detection rate: 4.73 T/s at 20 Hz, 8.83 T/s at 50 Hz, 10.55 T/s at 60 Hz, and 33.46 T/s at 100 Hz. Since it is a linear correlate of the induced in-situ E-fields, the dB/dt metric was chosen to analyse the the data. It confirmed lower magnetophoshene perception at lower frequencies for a similar in-situ induced E-field.