Neurological and electrophysiological examinations on three groups of workers with different levels of exposure to mercury vapors.

The authors performed neurological, visual evoked potentials (VEP) and electroneurography (ENG) examinations on three groups of workers with occupational exposure to mercury vapors (Hg(0)), and on a control group. The exposure of dental professionals (n = 36) was mild, that of chloralkali plant workers (n = 36) was intermediate, and that of workers from mercury works (n = 77) was very high. Symptoms and signs of micromercurialism were observed only in the group with the highest exposure to Hg(0). In comparison with the control group, a shortening of VEP latency and a decrease in amplitude were found in the exposed groups. The VEP changes correlated with Hg(0) excreted in urine after administration of a chelating agent - sodium 2,3-dimercapto-1-propan sulfonate (DMPS). The frequency of abnormal VEP results increased with increasing levels of exposure. ENG changes were observed only in the group with the highest exposure to Hg(0). An isolated decrease of sural nerve conduction velocity was observed in 18% of total workers. In 70% of the cases, this was associated with an abnormality in VEP. The combination of a decrease in sural nerve conduction velocity and an abnormality of VEP seems to be a characteristic pattern of electrophysiological changes in persons exposed to mercury vapors.