The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the Nations land, air, and water resources. Under a mandate of national environmental laws, the Agency strives to formulate and implement actions leading to a compatible balance between human activities and the ability of natural systems to support and nurture life. To meet this mandate, the EPAs Office of Research and Development (ORD) provides data and science support that can be used to solve environmental problems and to build the scientific knowledge base needed to manage our ecological resources wisely, to understand how pollutants affect our health, and to prevent or reduce environmental risks. The National Exposure Research Laboratory (NERL) is the Agencys center for the investigation of technical and management approaches for identifying and quantifying risks to human health and the environment. Goals of the Laboratorys research program are to develop and evaluate technologies for the characterization and monitoring of air, soil, and water; support regulatory and policy decisions; and provide the science support needed to ensure effective implementation of environmental regulations and strategies.