Study type: Medical/biological study (experimental study)

Perception of local DC and AC electric fields in humans med./bio.

By: Chapman CE, Blondin JP, Lapierre AM, Nguyen DH, Forget R, Plante M, Goulet D
Published in: Bioelectromagnetics 2005; 26 (5): 357-366
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Aim of study (acc. to author)

To address some of the factors that contribute to the human ability to detect the presence of weak electric fields generated by direct current (DC) and alternating current (AC) sources.

Background/further details

The study is an extension of a previous report of Blondin et al. with whole body exposure (see publication 2309).
In the first session (screening session), the exposed region consisted of the forearm and hand of the left, pronated arm, i.e., the dorsal skin surfaces were exposed. Further testing was restricted to AC electric fields as none of the subjects could detect the maximal DC electric field presented.

Endpoint

Exposure

Exposure Parameters
Exposure 1:
Exposure duration: repeated exposures each in four periods with a total maximum of 25 s
Exposure 2: 60 Hz
Exposure duration: repeated exposures each in four periods with a total maximum of 25 s

Exposure 1

Main characteristics
Frequency
Type
Exposure duration repeated exposures each in four periods with a total maximum of 25 s
Exposure setup
Exposure source
Chamber The electric field was generated by a plate suspended in the middle of the enclosure. The ground plate, on which the subject¿s arm rested, was elevated from the bottom of the enclosure, and heated to a comfortable temperature. The radial field intensity distribution (around the arm) was maximum at the highest exposed point in the chamber. Along the arm, field intensity was highest distally (hand), declining proximally (forearm).
Setup During testing, the subject was seated beside the exposure chamber. The left forearm and hand were inserted into the chamber through an aperture in the metal grid that surrounded the apparatus, and rested on the floor of the chamber.
Additional info Each signal trial (field present) consisted of four periods: (1) onset period (increase in field from 0 to the desired intensity, constant slope, maximum 7 s); (2) observation period (constant field, 7 s); (3) response period (maximum 4 s, i.e., until the subject responded); and (4) offset period (decrease in field to 0, same slope, maximum 7 s). There was no delay before the beginning of the next trial. Non-signal trials had the same time-course as signal trials, but no electric field was presented.
Parameters
Measurand Value Type Method Mass Remarks
electric field strength 30 kV/m minimum measured - -
electric field strength 65 kV/m maximum measured - in the screening session, field intensity was increased in steps of 10 kV/m from 30 up to 65 kV/m

Exposure 2

Main characteristics
Frequency 60 Hz
Type
Exposure duration repeated exposures each in four periods with a total maximum of 25 s
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
electric field strength 35 kV/m maximum measured - in the screening session, field intensity was increased in steps of 5 kV/m from 20 up to 35 kV/m
electric field strength 8 kV/m minimum measured - -
electric field strength 17 kV/m - measured - -
electric field strength 26 kV/m - measured - -
electric field strength 35 kV/m maximum measured - -
Additional parameter details

All subjects were subsequently tested using the SDT rating procedure with two blocks of trials (total of four AC intensities; two intensities/block). For seven subjects, the intensities were chosen on the basis of the results of the psychophysical staircase and spanned the estimated threshold (two above, two below). For nine subjects, four predetermined intensities (8, 17, 26, and 35 kV/m) were used, spanning the entire working range of the exposure chamber. The AC sensitive subjects participated in a further two or three sessions.

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • before exposure
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

None of 16 investigated subjects detected the local DC fields. In contrast, 9 of 16 subjects were sensitive to local AC electric fields, although detection thresholds were widely variable between subjects.
When local exposure was limited to the dorsal forearm, performance was similar to that found when the forearm and hand were exposed. In contrast, subjects did not reliably detect the AC electric fields when exposure was limited to the hand (either hairy or glabrous skin), although a minority of subjects (3 of 9) showed some evidence of detecting fields presented to the glabrous palm.
Subjects were unable to detect AC electric fields when the hair was removed from the forearm and hand, suggesting that the evoked sensation is dependent on movement of hair located in the exposed region.

Study character:

Study funded by

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