A blood lead benchmark for assessing risks from childhood lead exposure

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 (PbB) of ten micrograms per deciliter (10 mu g/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 mu g/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 (Delta Pb-B) of 1 mu g/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.