Lead Contamination of Surface Soils in Philadelphia from Lead Smelters and Urbanization

Lead contamination was introduced into U.S. surface soils at high concentrations during the last century, mainly as a result of lead-based paints and leaded gasoline products. Although these products have not been available or used since the 1995 ban on lead additives in gasoline for automobiles, lead continues to remain in the surface soils of inner cities. Lead (Pb) is a neurotoxin that has been linked to violence and reduced intelligence in children from long-term exposure to contaminated soils. Philadelphia is a city with a history of industrialization and provided a home to several Pb smelters, which extracted Pb from minerals and recycled Pb-waste to use in manufacturing these commercial products. Soils were analyzed in former industrial and non-industrial locations within Philadelphia. Overall, Pb concentrations were found to be higher at locations near former lead smelters than residential sites. Pb concentrations were also elevated in a soil sample adjacent to an old home with visibly weathering paint. One soil sample was further analyzed for its mineralogical composition and was found to contain Pb mostly in the form of an organic compound similar to the tetraethyl-lead compound in leaded gasoline. This study suggests that gasoline was an important source for Pb in surface soils, and that Pb contamination in Philadelphia soils may be quite widespread and not limited to former lead smelter sites and areas adjacent to buildings that contain lead-paint. Further analyses are necessary in order to create a more detailed perspective of existing trends in Pb contamination in Philadelphia soils.