Per- and polyfluoroalkyl substances, or PFAS, are not present in all U.S. water sources at detectable levels under current testing. But PFAS, also known as "forever chemicals," are widespread. PFAS, a group of manufactured chemicals used in products since the 1940s, have been linked to decreased fertility, developmental delays, increased risk of cancer and more.AllSides highlights content from Gigafact, a network of newsrooms that respond to online claims. View the full fact brief on Maine Trust for Local News.