Congress has allocated billions of dollars to address contamination caused by the ubiquitous class of “forever” chemicals known as PFAS—with billions more also earmarked in recent legal settlements with manufacturers—but drinking water managers, construction sector experts and other stakeholders say the true cost of cleanup could be much higher.

The prevalence of PFAS, short for per- and polyfluoroalkyl substances, is a real and growing concern. Thousands of different chemicals have been used in everything from firefighting foam and construction materials to clothing and household products, and have been detected in food sources, water supply, wildlife and human tissue—with new ones still being discovered. Some are identified as a threat to human health, even in small amounts.