In a previous study (publication 1968), 13 subjects exposed to extremely low frequency electromagnetic fields, the authors observed a significant decrease in lymphocyte, CD4, CD3, and CD2 counts and an increase in natural killer cells.
Six months following the end of this study, hematological and immunological parameters were measured again for 6 of the same subjects and the results were compared with earlier values. The first aim of the present study was to examine the evolution of hematological values after cessation of occupational exposure. The second aim was to address the controversy regarding comparable effects of electromagnetic fields on animals (mice were exposed in the same room in which the human subjects had been exposed for 109 days).
Exposure duration: 8 h/day for 5 years
Exposure duration: repeated daily exposure for 109 days
|Setup||The subjects worked in a laboratory located above the transformers, 13 kV high voltage bus bars and a power generator|
|Additional info||The measurements were preformed at 3 h intervals when the transformers were functioning normally. Control subjects worked in the same building as those exposed, doing the same type of work, but located 50 m away from the transformers and high voltage bus bars.|
|magnetic flux density||200 nT||minimum||measured||-||at the floor level|
|magnetic flux density||6,600 nT||maximum||measured||-||at the floor level|
|magnetic flux density||300 nT||minimum||measured||-||to at 1.5 m above the floor|
|magnetic flux density||1,500 nT||maximum||measured||-||to at 1.5 m above the floor|
|electric field strength||1 V/m||minimum||measured||-||-|
|electric field strength||220 mV/cm||maximum||measured||-||-|
|Setup||mice were housed in standard plastic cages (4 mice/cage) which were placed directly on the floor in the same laboratory loacted above the transformers and high voltage bus bars.|
|Additional info||Control mice were housed in the same standard plastic cages and kept in an animal exposure facility under identical light and temperature conditions.|
Six months after exposure had ceased, total lymphocyte counts had increased, as had CD4, CD3, and CD19 counts (+13%, +28%, +22%, and +17%, respectively). Natural killer cell counts were decreased by 26% (not significant) in the same human subjects.
The total lymphocyte, leukocyte, CD4, and natural killer cell counts of the exposed mice at 109 days were significantly lower than those of controls. Additionally, plasma glucose levels (at 30 days) and amylase activity (at 109 days) were significantly lower, whereas plasma sodium and chloride levels were significantly elevated at 109 days.
Data from this study suggest that chronic exposure to a 0.2-6.6-µT magnetic field can lead to decreased immunological parameters in both human and mice.
(Remark of evaluator: the magnetic field of the earth has a flux density from about 30 to 60 µT).