Estimated change in blood lead concentration in control populations.

Investigators have conducted several studies to assess the effectiveness of lead hazard interventions in reducing children's blood lead levels. For practical and ethical reasons, many of these studies have not included control populations. It is, therefore, impossible for researchers to determine to what extent the reported decline in blood lead concentrations has resulted from intervention versus other factors. In the current retrospective analysis, the authors estimated the change in children's blood lead levels in control populations at 12-mo follow-up. The results suggest that an average 9% decline may be attributed to factors that are unrelated to intervention. Declines of approximately 25% have been reported following several lead-hazard interventions. For these studies, the results of the authors' analysis suggest that approximately 16% of the decline is attributed directly to the intervention.