Follow-up Studies in Lead-Exposed Children

Seventy-six children out of 114 first tested at age 6 in 1982 were retested in 1985 at age 9. The range of blood lead values had been 3.9–22.8 μg/dl in 1982 (x g = 8.2) and was 4.4–21.4 μg/dl (x g = 7.8) in 1985; tooth lead concentrations were also available (x g = 4.68 μg/g; 1.8–28.2). Neuropsychological testing (WISC-R, Bender Gestalt test, Vienna Reaction Device and Delayed Reaction Times) and neurophysiological testing (sensory nerve conduction velocities = NCV and visual evoked potentials = VEP) was repeated in this group of children. Consistent associations with lead exposure (blood and teeth) after correction for confounding were, again, established for performance on the Vienna Reaction Device and for VEP latencies. Few significant but inconsistent associations were found for intelligence, delayed reaction times and NCV. These results are compatible with the hypothesis that some effects of lead on the CNS do not disappear with ageing over 3 years, if exposure remains unchanged.