HUMAN PERCEPTION OF ELECTRIC-FIELDS AND ION CURRENTS ASSOCIATED WITH HIGH-VOLTAGE DC TRANSMISSION-LINES

The objective of this study was to assess the ability of humans to det ect the presence of DC electric fields and ion currents. An exposure c hamber simulating conditions present in the vicinity of high-voltage D C (HVDC) lines was designed and built for this purpose. In these exper iments, the facility was used to expose observers to DC electric field s up to 50 kV/m and ion current densities up to 120 nA/m(2). Forty-eig ht volunteers (25 women and 23 men) between the ages of 18 and 57 year s served as observers. Perception of DC fields was examined by using t wo psychophysical methods: an adaptive staircase procedure and a ratin g method derived from signal-detection theory. Subjects completed thre e different series of observations by using each of these methods; one was conducted without ion currents, and the other two involved variou s combinations of electric fields and ion currents. Overall, subjects were significantly more likely to detect DC fields as the intensity in creased. Observers were able to detect the presence of DC fields alone , but only at high intensities; the average threshold was 45 kV/m. Exc ept in the most sensitive individuals, ion current densities up to 60 nA/m(2) did not significantly facilitate the detection of DC fields. H owever, higher ion current densities were associated with a substantia l lowering of sensory thresholds in a large majority of observers. Dat a analysis also revealed large variations in perceptual thresholds amo ng observers. Normative data indicating DC field and ion current inten sities that can be detected by 50% of all observers are provided. Tn a ddition, for the most sensitive observers, several other detection pro portions were derived from the distribution of individual detection ca pabilities. These data can form the basis for environmental guidelines relating to the design of HVDC lines. (C) 1996 Wiley-Liss, Inc.