The highest concentrations of “forever chemicals” in the Big Sioux River are in Sioux Falls and just south of Watertown, according to a report from South Dakota Mines.
The study, conducted by East Dakota Water Development District and researchers at the school, tested water for per- and polyfluoroalkyl substances (PFAS) at 13 sites from northeast South Dakota to the Iowa border between September 2024 and the end of 2025.
The chemicals have been used in industry and consumer products — from nonstick cooking pans to firefighting foam — since the 1940s and don’t break down easily in the environment or in the human body. PFAS exposure may be linked to negative developmental and reproductive effects, and an increased risk of some cancers, according to the Environmental Protection Agency…