Determination of the distribution of conduction velocities in workers exposed to lead, zinc, and copper.

By measuring the distribution of conduction velocities (DCV) in sensory fibres of the median nerve, the effects of asymptomatic increased lead, zinc, and copper absorption on the conduction velocities of slower and faster nerve fibres were examined in 29 gun metal founders with blood lead (BPb) concentrations of 22-59 (mean 39) micrograms/dl (1.1-2.8 (mean 1.9) mumol/l). The results indicated that the conduction velocities of slower fibres were inversely affected by lead absorption, resulting in a significant reduction in the velocities at the BPb level of 40-59 micrograms/dl; on the other hand, the conduction velocities of faster fibres and the conventional sensory nerve conduction velocity were presumably positively affected by zinc absorption without a significant reduction in the velocities of faster fibres. It is suggested that assessment of the possible antagonistic effect of zinc is essential when conduction velocities are not decreased in lead exposed workers.