DIFFUSE LEAD AND CHILDREN'S BLOOD LEAD LEVELS IN INDIANAPOLIS

Lead contamination in the environment has been greatly reduced since the phase-out of leaded gasoline and lead-based paints almost twenty years ago. Why then are high blood lead levels, a sure sign of lead intake and a grim warning of retardation, seen in many urban youth populations? The paradigm has been that the intake mechanism has been via ingestion of lead-based paints from poorly maintained structures. This paradigm has defacto concentrated the bulk of money available for lead abatement programs toward lead paint removal and stabilization. Although a laudable effort, research in Baltimore and New Orleans indicates that lead deposited on soils of yards and playgrounds is mainly a legacy of airborne deposition from leaded gasoline exhaust, and thus lead-paint focused programs do not adequately address this reservoir of potentially harmful lead.

To begin addressing the question of lead sources and sinks in an urban area like Indianapolis (which exhibits clusters of extremely high blood-lead levels in children), we collected and analyzed surface soil samples from approximately 100 sites in Marion County. We also collected soils from rural sites outside of Marion County for comparison. Our sampling strategy was designed to provide a comprehensive catalog of soil lead status in the county, and additionally we focused on several discrete sampling strategies, including sampling several profiles at depth, sampling in grids as a function of distance from roadways, and sampling across a variety of soil types. We found several interesting features: 1) lead concentrations typically ranged from 50 - 300 ug/g, 2) lead decreased exponentially away from roads, often decreasing from ~400 ug/g to background values of 50 ug/g at a distance of 50 m from a road, and 3) extremely high values (up to 1000 ug/g) are found within 1 km of the lead smelting plant in southeastern Indianapolis. A comparison to Indiana Public Health records of blood lead levels shows correlation between high soil lead and high blood lead levels. The regional characteristics of the high soil lead values indicate airborne rather than lead-paint sources to these areas. We plan, however, to perform more rigorous biostatistical evaluation of correlation to support or refute this troubling suggestion.