Gov. Tom Wolf’s administration on Tuesday received preliminary regulatory approval to set a statewide drinking water limit on the presence of two forms of highly toxic chemicals, nicknamed “forever chemicals." The proposed rule, approved by the Environmental Quality Board, would set a limit of 14 parts per trillion for perfluorooctanoic acid and 18 parts per trillion for perfluorooctane sulfonic acid. The rule applies to all 3,117 water systems, the Department of Environmental Protection said. Both chemicals belong to the group of perfluoroalkyl and polyfluoroalkyl substances, known collectively as PFAS, and which are used in products like nonstick cookware, carpets, firefighting foam and fast-food wrappers.The rule still requires approval by another regulatory board, and could take months. Currently, there is no national limit, although the federal government has issued an advisory level of 70 parts per trillion or below.Earlier this year, the state Department of Environmental Protection said that about one-third of the more than 400 sites it had tested across Pennsylvania were found to contain one of the chemicals.The chemicals have turned up increasingly in public water systems and private wells around the country after the federal government in 2013 ordered public water systems with more than 10,000 customers to test for it.Studies have found “associations” between the chemicals and cancer, thyroid disease, ulcerative colitis and other health issues, although state officials say their effects on human health are not fully understood.