There's a new contamination problem that people are calling "the new asbestos." It's per- and polyfluoroalkyl substances, more commonly known as PFAS. PFAS has been linked to numerous health problems, and cities and towns across the country have been finding them in their water supplies—especially towns or around military bases. Why? Because PFAS was commonly used in firefighting foam that was sprayed liberally on tarmacs and airstrips. Maureen Sullivan is the Pentagon's point person for addressing this mushrooming problem. She said the cost of cleaning up PFAS contamination could exceed $2 billion and take a generation to complete. We spoke to her at the annual conference of the Environmental Council of the States in Stowe, Vt.