Abstract

Lead exposure is an insidious problem, causing subtle effects in children at low exposure levels where clinical signs are not apparent. Although a target blood lead concentration (Pb(B)) of ten micrograms per deciliter (10 microg/dL) has been used as the basis for environmental decision-making in California for nearly two decades, recent epidemiologic evidence suggests a relationship between cognitive deficits and Pb(B) at concentrations < 10 microg/dL. Based on a published meta-analysis of children's IQ scores and their blood lead concentrations, we developed a new blood lead benchmark: an incremental increase in blood lead concentration (DeltaPb(B)) of 1 microg/dL, an increase that we estimate could decrease the IQ score in an average school child in California by up to one point. Although there is no evidence to date for a threshold for the neurobehavioral effects of lead, a one-point IQ decrement was chosen to represent a de minimus change. To safeguard the intellectual potential of all children, additional efforts to reduce or eliminate multiple-source exposures to lead are warranted.