46 male spot welders and a control group (n=45) from the same factory were examined (mean employment period = 3.8 years). Both groups were matched according to demographical characteristics, employment conditions and exclusion criteria. The workers were exposed to dynamic electromagnetic fields 40h/week (6 days/week). Prior to start of each working shift (following 12 h fasting), blood samples were obtained. Concentration of metal fume (confounder variable) was measured to control effects on antioxidant activity.
Exposure duration: 40 h/week for 3.8 years (mean time)
|Distance between exposed object and exposure source||1 m|
|electric field strength||20 V/m||minimum||measured||-||at the worker's chest|
|electric field strength||133 V/m||maximum||measured||-||at the worker's chest|
|magnetic flux density||8.8 µT||minimum||measured||-||at the worker's chest|
|magnetic flux density||84 µT||maximum||measured||-||at the worker's chest|
The mean concentration of the total antioxidant activity was higher in the exposed group than in the non-exposed group; however this difference was insignificant. In the red blood cells of the exposed group, a significant decrease in superoxide dismutase activity and glutathione peroxidase activity was observed. A significant negative correlation between magnetic field intensity and superoxide dismutase activity and glutathione peroxidase activity was observed. There was no significant correlation between metal fume exposure and antioxidant acitvity.
The findings may suggest a dose-response relationship between magnetic field strength and erythrocyte antioxidant activity, which might occur even at the recommended levels of exposure.The results indicate that extremely low frequency magnetic fields could influence the red blood cell antioxidant activity and might act as an oxidative stressor.