Calcium disodium ethylenediaminetetraacetate-chelated lead as a predictor for subclinical lead neurotoxicity: follow-up study on gun-metal foundry workers

Abstract

Objectives: To examine if chelated lead was a more predictive indicator of the subclinical effect of lead on conduction velocities of faster or slower nerve fibers as compared with blood lead (BPb). Methods: Distribution of conduction velocities (DCV) in large myelinated fibers of the sensory median nerve was measured twice at a 1-year interval in 17 male gun-metal foundry workers with BPb concentrations of 22–59 (mean 40.2) μg/dl and a mobilization yield of lead into urine (MPb) by calcium disodium ethylenediaminetetraacetate of 0.15–2.09 (mean 1.19) mg/24 h for the 1st year and in 20 healthy males (controls). Results: Yearly changes in the conduction velocities of faster fibers were significantly correlated with the corresponding change in MPb (P < 0.05) but not with that in BPb (P > 0.05). In ten workers showing an increase in MPb during the 1-year period (0.44 mg/24 h on average) the conduction velocities of faster fibers were decreased significantly, resulting in the values being significantly lower in all the workers combined than in the controls (P < 0.05). On the other hand, in the remaining workers, who showed a lesser extent of reduction in MPb (0.08 mg/24 h on average), the DCV did not change (P > 0.05). Conclusion: Chelated lead might be a more predictive indicator of the effect of lead on the conduction velocities of faster fibers than blood lead.