'Ticking time bomb': PFAS chemicals in drinking water alarm scientists over health risks

Greater detection of toxic PFAS chemicals in drinking water systems nationwide has alarmed state and local leaders and prompted Congress to seek urgent action from EPA.

TUCSON, Ariz. -- A family of colorless and tasteless man-made chemicals -- largely unregulated by the U.S. Environmental Protection Agency -- has become a growing concern for drinking water safety in thousands of American communities, as scientists increasingly see links to liver damage, high cholesterol, weakened immune systems and cancer. "They basically fulfill the characteristics of a ticking time bomb," said Dr. Bo Guo, a University of Arizona hydrologist and expert on per- and polyfluoroalkyl substances, or PFAS, which are commonly used in hundreds of consumer products and in firefighting foams, a top source of PFAS contamination. "They're very dangerous and they're migrating very slowly," Guo said of the heat-resistant chemicals. WATCH: ABC News Live Prime investigates PFAS contamination in drinking water systems nationwide, 7p/9p ET. Streaming on Hulu, ABC News apps and ABCNews.com/live.