A group of synthetic chemicals called per- and polyfluoroalkyl substances—PFAS, for short—are used in a wide range of consumer, manufacturing, and fire safety products. But these chemicals contaminate the environment and some are linked to health problems in people. More information is needed to help government agencies and others address PFAS-related risks. But this group of chemicals is large, diverse, hard to study, and difficult to fully remove from the environment. In this report, we discuss technologies to detect and treat PFAS contamination and assess its health effects. We also offer policymakers additional actions to consider.