LEAD-EXPOSURE AND COGNITIVE-DEVELOPMENT - PERSISTENCE AND A DYNAMIC PATTERN

Objectives: Although enormous effort has been focused over the past tw o decades on examining the potential adverse effects of exposure to en vironmental lead on human health, there has been a debate over the per sistence and dynamic pattern of these effects. Methodology: Articles r elevant to this issue which were published between January 1982 and De cember 1996 were retrieved from Medline and adjunct searching methods (i.e. hand searching of key journals, review of the bibliographies of reports known to be relevant, consulting with experts, and use of Scie nce Citation Index). Results: Currently available epidemiological evid ence suggests that 'low' level exposure to lead in early childhood is likely to cause a moderate but real and detectable effect on cognitive development, and this effect appears to persist into later childhood. The findings from four long-term prospective studies seem to support the constant decrement model which assumes that cognitive deficits res ulting from early lead exposure persist over an extended period of tim e even when exposure decreases. Conclusion: From a public health persp ective, it is highly desirable and prudent to reduce the dispersive us es of lead. Since lead is ubiquitous and persistent in the environment and may have a subtle and persistent effect on cognitive development, how to set the environmental standards for lead exposure is an import ant scientific issue still open for debate.