Past adult lead exposure is associated with longitudinal decline in cognitive function

Objective: To determine whether adults with past exposure to neurotoxicants have progressive declines in cognitive function years after exposure has c eased, and whether tibia lead is a predictor of the magnitude of change. Me thods: A total of 535 former organolead manufacturing workers with a mean a ge of 55.6 years, a mean duration of 16 years since last occupational lead exposure, and low blood lead levels at the first study visit and 118 contro ls were evaluated with neurobehavioral tests two to four times over 4 years . "Peak" tibia lead levels, estimated from current levels measured by X-ray fluorescence, were used to predict changes in cognitive function over time . Results In former lead workers, peak tibia lead ranged from -2.2 to 98.7 mug Pb/g bone mineral. Compared to controls, former lead workers performed worse over time for three tests of visuo-constructive ability and verbal me mory and learning (p < 0.05). In former lead workers, peak tibia lead predi cted declines for six tests of verbal memory and learning, visual memory, e xecutive ability, and manual dexterity (p < 0.05 for four tests and < 0.10 for two additional tests). On average, for these six tests, an increase of 15.7 <mu>g/g of peak tibia lead was equivalent in its effects on annual tes t decline to 5 more years of age at baseline. Conclusions: These are the fi rst data to suggest that cognitive function can progressively decline due t o past occupational exposures to a neurotoxicant.