Assessing the contribution from lead in mining wastes to blood lead

Lead has been recognized for years as an environmental pollutant of concern for young children. Nonetheless, many children in the United States still experience high body burdens of lead. Reducing exposure to lead must include an assessment of all potential sources of lead and a definition of routes of exposure. In this paper, the relationships between soil lead and blood lead concentrations in residents in communities with high soil lead concentrations resulting from past mining and ore processing (milling) activities are compared to those derived from studies in urban communities or communities with operating smelters. The impact of mine waste-derived lead in soil (usually in the form of lead sulfide) on blood lead is less than that for lead in soil derived from smelter, vehicle, or paint sources. Possible reasons for a reduced impact of lead sulfide on blood lead in children in mining communities include the following: lead from mining sources contributes less to lead in the immediate environment of children than lead from other sources; mine wastes typically are of larger particle size, which decreases the bioavailability of lead in the gastrointestinal tract; and lead sulfide is absorbed less in the gastrointestinal tract compared to other lead species. A reduced impact of mine waste-derived lead on blood lead may be important from a regulatory point of view. Expensive cleanup actions for lead-contaminated soils in mining communities based on acceptable soil lead concentrations derived from smelter or urban communities may be questionable in terms of reducing blood lead in children.