Measurement and analysis of ELF electric field on human body surface

In order to study the biological effects of an ELF (extremely low frequency) electric field, the force exerted on body hair due to field exposure was investigated. It was shown theoretically that the force was proportional to the spatial gradient of the square of the electric field at the hair, and that it had a positive correlation with the dielectric constant of hair. A technique to measure the dielectric constant of hair in the ELF range was developed. Measurements were conducted at different temperatures and humidities of air surrounding human hair. It was found that the dielectric constant of hair increased with the relative humidity. It is concluded that these results provide useful information concerning the mechanism of the biological effects of the electric field. They explain well the seasonal variation of the threshold level of field perception. Therefore, the results suggest that the effect of humidity should be taken into account in setting up the safety standard for field exposure.