EEG findings in chlor-alkali workers subjected to low long term exposure to mercury vapour

The cerebral effect of long term (mean 15.6, SD 8.9 years) and low (about 25 micrograms/m3 air) exposure to mercury vapour was studied in a group of 41 workers in a chlor-alkali plant and in a group of matched referents by electroencephalography (EEG). In the visually interpreted EEGs only a tendency for an increased number of EEG abnormalities, especially focal ones, could be seen in the exposed subjects. In the computerised EEG (cEEG), however, the exposed workers had significantly slower and more attenuated EEGs than the referants. This difference was most prominent in the occipital region, became milder parietally, and was almost absent frontally. Our results suggest that cEEG may show early effects on the brain of exposure to mercury vapour.