The longitudinal evaluation of verbal-reasoning in lead workers

Four times during the course of a year, asymptomatic lead workers from the printing industry underwent a series of psychological tests assessing memory, attention, verbal-reasoning and spatial skills. In a syntactic reasoning task, the exposed group were less accurate, tended to be slower on the more complex problems and showed less consistent improvement over the year. An examination of subjects with changing blood-lead levels during the year showed that, within the exposed group, those with rising blood-lead levels were less accurate than those whose blood-leads fell or remained constant. This may indicate that effects of changing blood-lead concentrations depend upon overall level of exposure.