Further results on this study population are published in Tiwari et al (2013).
A total of 293 male volunteers participated in the study and were divided into two groups: an exposure group (n=142) including subjects with occupational exposure to high voltage substations for more than 2 years, and the control group (n=151) including individuals without such an exposure. The age, socioeconomic status and lifestyle factors were matched between both groups. A blood sample was taken from each subject between 8 and 10 o'clock in the morning.
The exposure group was partly divided into the following subgroups: based on distance of work place to a transformer: 1) less than 2 m (n=?), 2) less than 10 m (n=?); based on total exposure duration: 3) 2-5 year (n=42), 4) 6-13 years (n=45), 5) 14-30 years (n=55); based on frequency of exposure (hours/day): 6) 1-3 h (n=59), 7) 4-6 h (n=45), 8) 7-9 h (n=38); based on exposure level (depending on job title): 9) low (n=87), 10) medium (maintenance; n=44), 11) high (live-line work; n=11).
No parameters are specified for this exposure.
No significant changes in the adrenaline level were found between the exposure group and the control group or between the subgroups.
A tendency towards increased DNA damage in the exposure group compared to the control group was found though the significance was not stated.
Regarding oxidative stress, the lipid peroxidation concentration was significantly increased in the exposure group compared to the control group (remark EMF-Portal: the significance specifications for nitric oxide were contradictory).
The total exposure duration had a significant effect on oxidative stress with the highest values found in subgroup 5 (exposure for more than 14 years). However, no consistent trend was found.
Regarding the exposure level, subgroup 11 (high level) showed significantly increased oxidative stress parameters compared to subjects with a lower exposure level (subgroups 9 and 10). A medium exposure level (subgroup 10) resulted in a significantly increased lipid peroxidation compared to a low exposure level (subgroup 9).
The authors conclude that occupational exposure to extremely low frequency fields in substations could induce oxidative stress in the blood depending on the level of exposure.