Recovery of slowed nerve conduction velocity in lead-exposed workers

Summary Maximum motor nerve conduction velocities in the median nerve (MCV) and blood lead (PbB) were repeatedly measured in 14 lead exposed workers with an initial PbB from 0.7 to 4.0 mol/kg (median 2.3 mol/kg) for a period from 3 months to 7 years: A certain dose of Calcium Disodium Ethylenediaminetetraacetic Acid (CaEDTA) was injected intravenously into most of the subjects during the period.In seven subjects, MCV improved by more than 4 m/s during the observation period which involved the first two successive measurements of MCV and PbB, but the remaining seven subjects showed the minimal alteration (within ± 4.0 m/s). The initial value of MCV was significantly slower (P < 0.01) and the decrease in PbB was significantly greater (P < 0.05) in the group of subjects having shown the improvement of MCV by more than 4 m/s.The initial value of MCV was significant in determining the alteration in MCV in multiple regression analysis and, together with the change in PbB, explained 31% of the alteration in MCV between the first two successive measurements. The initial level of PbB, dose of CaEDTA, time interval between the measurements and age played no essential part in the alteration in MCV.The alteration in MCV throughout the whole observation period in each subject significantly correlated with the concurrent change in PbB (r=–0.573, P < 0.001).