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

Abstract

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). 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) microg/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). 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). Chelated lead might be a more predictive indicator of the effect of lead on the conduction velocities of faster fibers than blood lead.