Distinguishability of the video display terminal (VDT) as a source of magnetic field exposure

Magnetic field strength or its surrogate has been used as the measurement of exposure in all studies involving field exposure. Video display terminals (VDTs) are considered a minor source on this scale because its field strengths lie in the low range of magnetic fields. Several experiments show, however, that field strength may not be the only relevant variable in determining exposure. This paper explores the use of a method based on "effects functions" to determine the extent to which the VDT can be distinguished from other sources. It is shown that VDT exposure may be of consequence if exposure depends on certain types of time variation of the field. Because of the incompleteness of science in this area, this is a demonstration of a method rather than an actual demonstration of VDT as a significant source of exposure.