Repeated neurobehavioral investigations in workers exposed to mercury in a chloralkali plant

Mercury exposed workers of a chloralkali electrolysis plant were investigated with neurobehavioral methods. At the beginning of the investigation an average exposure of 12 years was stated. Four periods of investigations were carried out over the course of 7 years. A low exposed group (n = 34-50, 21-26 micrograms Hg/l Urine) and a high exposed group (n = 14-21, 111-152 micrograms/l Urine) were defined for each of the time periods using 53 micrograms/l Urine as discriminating level. Controls (n = 37-43) were recruited from non-exposed departments of the factory. Age, verbal intelligence and gender were controlled statistically to reduce potential confounding. Symptoms and personality traits did not covary significantly with the exposure. Finger dexterity, tapping, and aiming were variables out of 13 performance measurements, which showed repeatedly a lower level of performance corresponding with increasing current exposure. However, dose-response relations could not be demonstrated by partial correlations to the concentration of mercury in Urine. Subgroups of 30 controls, 37 low exposed and 14 high exposed workers were examined in a follow-up study with repeated measurements. Significant exposure effects were shown for finger dexterity and aiming.