Measurements of extremely low-frequency magnetic fields around video display terminals.

Abstract

of extremely low-frequency magnetic fields around video display terminals. Scand J Work En viron Health 12 (1986) 609-613. The extremely low-frequency (ELF) magnetic field emissions of seven video display terminal (VDT) models were measured. A measuring coil with a linearized frequency response (50 Hz to 25 kHz) was used. The dominating ELF magnetic field around the terminals was the 50 or 60 Hz asymmetric triangular waveform from the vertical deflection coil of the cathode ray tube. At the distance of 50 em, the magnetic field strength was still slightly higher than the background level in usual office rooms, but several orders of magnitude lower than the thresholds of known interaction mechanisms. Some recent experiments suggest that certain biological effects may occur at field strengths only a few times higher than those found at the position of VDT operators, but the significance of these effects to human health is not known.

Early pregnancy loss and exposure to 50‐Hz magnetic fields

“…The coil was shielded against electric fields, and its frequency response was linearized between 50 Hz and 5 kHz. The construction principles of the meter and its calibration were similar to those described by Juutilainen and Saali [1986]. Because the coil is sensitive to the direction of the magnetic field, it was rotated to find the maximal reading in each measuring point.…”

Effects of low-frequency magnetic fields on embryonic development and pregnancy.

“…Video display terminals with a cathode ray tube display emit extremely low-frequency magnetic fields at 50 or 60 Hz and very low-frequency magnetic fields at 15-30 kHz. The strength of the extremely low-frequency magnetic field is a few amperes per meter (a few microteslas) at the surface of the terminal and about 0.1-0.3 Aim (0.1-004 IlT) at the operator's position (48,49). In addition to low-frequency magnetic fields, video display terminals emit several other types of electromagnetic energy, including optical radiation, radiofrequency radiation, and static electric fields.…”

Measurements of Electromagnetic Emissions from Video Display Terminals at the Frequency Range from 30 Hz TO 1 MHz

“…In the ELF range results are available for B fields (Stuchly and Lecuyer 1983;Juutilainen and Saali 1986). Broadband antennas and field-strength meters have usually been employed, giving the amplitude and rms (root-mean-square) value of the field strength.…”