ELF electromagnetic fields
The aim of the study was to investigate the possible acute effects of exposure to electricand magnetic fields. Twenty six experienced linesmen, aged 25 to 52, were studied during two working
days while performing a simulated routine inspection of insulators on steel poles of a 400 kV power
line. During one of the working days the inspection was performed on a power line in operation and
on the other day the same procedure was performed on an identical power line, which was not in
operation. The two days were found to be comparable with regard to the physical workload which, on
the basis of heart rate measurements, was estimated to be high. Exposure to the electric and magnetic
fields was measured using a device designed for on-worker sampling on each linesman. The mean
exposure for the working day was estimated to be 2-8 kV/m (SD = 0-35) and 23-3 PT (SD = 4.2). The
possible effects ofexposure were studied using a battery offour automated performance tests, EEG, a
mood scale, and a questionnaire to assess subjective symptoms. All workers were examined
immediately before and after each workday. Furthermore, blood samples were collected for each
subject on three different occasions during each workday. The battery of behavioural tests comprised
a test of simple reaction time, a vigilance test, a test of short term memory (digit span), and a
perceptual test (symbol digit). The four EEG recordings for each worker were judged blindly and
sorted with regard to amount and stability of alpha activity. The blood samples were used for an
analysis of possible changes during the workday with regard to the following hormones: thyroid
stimulating hormone, luteinising hormone, follicle stimulating hormone, prolactin, cortisol,
testosterone, and neopterin. Detailed analyses of the results using both parametric and nonparametric
tests showed no statistically significant difference between the two conditions which could
be attributed to exposure to electric and magnetic fields.
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