No cognitive deficits in men formerly exposed to lead

Objectives: The objective of the study was to investigate long-term cognitive effects resulting from low-to-moderate lead exposure below current threshold values. Executive functions, attention, visuospatial and visuomotor functioning in workers formerly exposed to lead were investigated. Methods: 48 men formerly exposed to lead and with a mean current blood level (PbB) of 5.4 mu g Pb/100 ml were investigated, together with 48 matched controls (PbB: 4.7 mu g Pb/100 ml) out of a pool of 61 males. The two groups were matched for age, years spent in education, verbal intelligence and gram alcohol consumption per week. The following neuropsychological tests were used: modified Wisconsin card sorting test, block design test, visual recognition test, simple reaction time, choice reaction and digit symbol substitution. Lead exposure was assessed using both current and cumulative measurements. Results: There were no significant differences in cognitive parameters between the two groups. When analyzing dose-response relationships, negative correlations were found between PbB and performance in the block design test, and between PbB and scores in the visual recognition and digit symbol substitution tests. High cumulative exposure (IBL > 5000 and duration of exposure > 5 years) correlated only with wrong reactions in the choice reaction test. Conclusions: The results of our study indicate that cognitive deficits resulting from low-level exposure to lead are reversible. The study was limited to low-level longterm exposure (all PbB values were always below 55 mu g Pb/100 ml), and extrapolation of these results to persons heavily exposed to lead is not possible.