A NEUROLOGICAL AND NEUROPHYSIOLOGICAL STUDY OF CHLORALKALI WORKERS PREVIOUSLY EXPOSED TO MERCURY-VAPOR

Neurological and neurophysiological examinations were conducted in 77 former chloralkali workers previously exposed to mercury vapour and 53 referents. The exposure had ceased on average 12.3 years prior to the study. There was a higher prevalence of reduced distal sensation (13. 0% vs 1.9%), postural tremor (18.2% vs 7.5%) and impaired coordination (10.4% vs 1.9%) among the exposed subjects as compared to the referen ts. Abnormal Romberg's test (6.5% vs 0%) and line walking (7.8% vs 0%) were also more prevalent. The first negative peak in visual evoked re sponse (N75) was bilaterally prolonged, and the median motor (55.9 m/s vs 58.0 m/s) and sensory nerve conduction velocity (55.6 m/s vs 59.0 m/s) were slightly reduced among the highly exposed subjects. The resu lts indicate that slight neurological abnormalities, which in most cas es could not be classified as disease, may persist many years after ex posure cessation.