In 1981, the EPA began investigating the area where the companies once operated for radioactive materials. Five areas were identified as having abnormally high levels of gamma radiation, including the locations of both companies and three primarily residential areas. In 1993, a sixth area was identified. Radioactive materials were identified at 100 properties located near the companies' former facilities in Camden and Gloucester City, as well as the company locations themselves. In 1996, due to the levels of contamination in the areas, the Welsbach and General Gas Mantle site was added to the National Priorities List, which consists of areas in the United States that are or could become contaminated with dangerous substances. The EPA demolished the General Gas Mantle building in late 2000 and only one building remains at the former Welsbach site. Since it was declared a Superfund site, the EPA has removed over 350,000 tons of contaminated materials from the Welsbach/General Gas Mantle site.