Asymptomatic sensorimotor polyneuropathy in workers exposed to elemental mercury.

Neurologic and electrodiagnostic evaluations and urine mercury level determinations were performed on 138 chlor-alkali plant workers, some of whom were chronically exposed to inorganic mercury vapor. Eighteen subjects had a mild polyneuropathy on clinical examination. These subjects had significantly (p less than 0.05) elevated urine mercury indexes, reduced sensation on quantitative testing, prolonged distal latencies with reduced sensory evoked response amplitudes, and increased likelihood of abnormal needle electromyography compared with the remaining 120 subjects. Similar results were found for subgroups matched by sex and age. We conclude that elemental mercury exposure is associated with a sensorimotor polyneuropathy of the axonal type; the degree of neurologic impairment appears related to the magnitude of exposure.