Lead exposure and cognitive development: persistence and a dynamic pattern.

OBJECTIVES

Although enormous effort has been focused over the past two decades on examining the potential adverse effects of exposure to environmental lead on human health, there has been a debate over the persistence and dynamic pattern of these effects.

METHODOLOGY

Articles relevant to this issue which were published between January 1982 and December 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 Science Citation Index).

RESULTS

Currently available epidemiological evidence 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 resulting from early lead exposure persist over an extended period of time even when exposure decreases.

CONCLUSION

From a public health perspective, it is highly desirable and prudent to reduce the dispersive uses 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 important scientific issue still open for debate.