Original sentence: Chat piles left behind by the mining companies contain lead dust that has blown around the city.Elevated lead levels in Picher children have led to learning disabilities and other problems.Picher's recent notability has been due to its location near the United States Environmental Protection Agency's Tar Creek Superfund site, which had a long history of underground lead and zinc mining until around 1970.Since the children of Picher have been found to have elevated levels of lead in their bodies, the EPA has since declared Picher to be one of the most toxic areas in the United States.The lead and zinc have also seeped into groundwater, ponds, and lakes, many of which still are used by children for swimming