(This article by Brian Bienkowski of Environmental Health News was originally posted Sept. 26, 2014, and is used here with permission.) A persistent chemical formerly used in Scotchgard still contaminates most fish in U.S. rivers and the Great Lakes despite a phase-out a dozen years ago, a new federal study shows. U.S. Environmental Protection Agency researchers found perfluorooctane sulfonic acid (PFOS) in all of the 157 fish sampled from nearshore waters in the five Great Lakes and in 73 percent from 162 rivers.