Evaluating the cumulative exposure to low frequency electric fields

Starting from this July, we have to apply the guidelines emerging from the new Directive 2013/35 / EU, focused on the protection of European citizens against the excessive exposure to non-ionizing electromagnetic radiation. In the present paper we have focused only on the low frequency emissions of electric field. Even in the Directive, are clearly underlined the differences, from many points of view, between the non-thermal dominant effects of low frequency fields and the radiofrequency fields with dominant thermal effects. In turn, the low frequencies domain imposes a distinct treatment of the electric and magnetic fields, which are not mutually linked by constant impedance. It is compulsory a different approach for these near fields from various perspectives: probes, measuring procedures, human response to excessive exposure. In the first part we have completed a synthetic comparison of maximum permissible E-field levels, according to different European or even worldwide standards, now in force. In the second part, based on a clearly stated procedure, we have measured and interpreted the E-fields strengths, at four distinct low frequencies, in a library hall fitted with 25 PCs (full-tower cases and 15” TFT-LCD displays) and individual energy saving lamps for every workstation. There were compared the results by developing a cumulative metric, aiming to provide a single number assessing the level of exposure to close electric fields. While interpreting the results and the influence of different factors on the proposed metric, we put forward actions aiming to reduce human exposure to this manmade (disturbing) factor.