Neuropsychological effects of lead in children: interactions with social background variables

Following a short and selective summary of findings from psychological studies on lead-induced cognitive dysfunction in man, our own studies in lead-exposed children are briefly described in more detail. These studies, run in the cities of Duisburg and Stolberg, were based on tooth lead levels as the principal indicator of long-term cumulative lead exposure. From a comprehensive sample of neuropsychological outcome measures, only few significant findings emerged, namely lead-related deficits of visual-motor integration and of reaction performance, but not of general intelligence. Without exception, the observed lead effects were small compared to those of social background. An interesting interaction was found between lead exposure and social background for visual-motor integration and for reaction performance: for both these measures, but not for intelligence, the degree of association between performance deficit and lead exposure was more pronounced in socially disadvantaged children than in those from a more middle-class background. This finding was tentatively discussed within a transactional model of development. The common practice of simply controlling the effects of confounding social factors by analysis of covariance or related techniques appears doubtful in this context.