An experimental study on limb contact current (perception and current load) at an electromagnetically-exposed workplace — The study focused on intermediate- and radio-frequency exposure

The limits for limb contact currents noted at the workplace exposed to electromagnetic fields with a frequency up to 110MHz have been set out by international guidelines (including European Directive 2013/35/EU) to protect workers against the indirect effects of exposure. The aim of this study was to analyse what level of limb currents exceed the perception threshold in the intermediate- and radio-frequency range used mostly by new telecommunication and power transfer technologies (f>15kHz). In tests with a group of healthy adult males, in the intermediate-/radio-frequency experiments, the contact current perception threshold was found to be proportional to the size of the contact area ((0.4-1.4)cm in diameter), and less inter-personally spread for larger contact areas, higher frequencies and for use of electro-conductive gel. Some percentage of workers are sensitive to limb current flow at levels significantly lower than the relevant limits. The tests, involving volunteers and the use of several clamp-on current meters, where focused on the in-situ evaluation of limb contact currents near broadcasting antennas. They showed that, in practice, the uncertainty of measurements reach +/-50%-covering inter-person variability, influence of the contact and exposure conditions and the calibration of measurement devices. The results indicate the limitations in the use of in-situ contact current measurements in occupational safety management system.