Neurophysiological studies on workers exposed to lead.

Nerve conduction and somatosensory evoked potential studies were undertaken on 46 workers exposed to a combination of organic and inorganic lead. In addition electroencephalograms were carried out on 20 of the workers; the results were compared with those obtained for workers not exposed to lead. The workers exposed to lead had a mean blood lead concentration of 2.35 mumol/l (48.7 micrograms/100 ml), whereas the concentration for workers not exposed to lead was 0.76 mumol/l (15.8 micrograms/100 ml). The mean maximum motor conduction velocities of the median and the posterior tibial nerves were significantly lower in the workers exposed to lead than in the controls. Similarly, the distal latency for these two nerves was significantly prolonged for the workers exposed to lead. No significant differences for the two groups of workers were seen in the nerve conduction and distal latency measurements of the median (sensory) and the sural nerves. The EEG studies of the 20 workers exposed to lead showed no abnormalities. The somatosensory evoked potential of the median (sensory) and posterior tibial nerves were significantly prolonged when measured at the negative and positive deflections. The results suggest that, in addition to nerve conduction velocities, somatosensory evoked potential and distal latency are suitable measurements to detect subclinical neurological damage among workers exposed to lead. As these changes were seen at blood lead concentrations of 2.35 mumol/l (48.7 micrograms/100 ml) there may be a need for more stringent monitoring of workers exposed to lead.