OCCUPATIONAL EXPOSURE TO LEAD AND NEUROPSYCHOLOGICAL DYSFUNCTION

Objective-To evaluate the neuropsychological effects of current low le vel and previous higher levels of exposure to lead and evaluate the re lation between effects of lead and bone lead. Methods-A neuropsycholog ical test battery was given to 54 storage battery workers with well do cumented long term exposure to lead. The effect was studied in two sub groups: those whose blood lead had never exceeded 2.4 mu mol/1 (the lo w BPbMax group, n=26), and those with higher exposure about 10 years e arlier (the high BPbMax group, n=28). In both groups, the recent expos ure had been low. Correlations between the test scores and the indices of both long term and recent exposure-including the content of lead i n the tibial and calcaneal bone-and covariance analyses were used to a ssess the exposure-effect relation. Age, sex, and education were contr olled in these analyses. Results-Analyses within the low BPbMax group showed a decrement in visuospatial and visuomotor function (block desi gn, memory for design, Santa Ana dexterity), attention (digit symbol, digit span), and verbal comprehension (similarities) associated with e xposure to lead and also an increased reporting of subjective symptoms . The performance of the high BPbMax group was worse than that of the low BPbMax group for digit symbol, memory for design, and embedded fig ures, but there was no reporting of symptoms related to exposure, prob ably due to selection in this group. No relation was found between the output variables and the tibial lead concentration. The calcaneal lea d concentrations were related to the symptoms in the low BPbMax group. Conclusions-Neuropsychological decrements found in subjects with high past and low present exposure indicate that blood lead concentrations rising to 2.5-4.9 mu mol/1 cause a risk of long lasting or even perma nent impairment of central nervous system function. Milder and narrowe r effects are associated with lower exposures; their reversibility and time course remain to be investigated. History of blood lead gives a more accurate prediction of the neuropsychological effects of lead tha n do measurements of bone lead.