Two years ago, barely anyone had heard of PFAS, or per- and polyfluoroalkyl substances. Today, at Bloomberg Environment, we report almost daily on the chemicals. We know that 97% of Americans have a detectable amount of PFAS in their blood, but we don’t yet know all of the effects of the chemicals on our health. And they’re also so prevalent that the EPA administrator says there are more than 600 PFAS chemicals on the marketplace in the U.S., and the Organization for Economic Cooperation and Development says there could be 5,000 types worldwide. Now states are racing to regulate PFAS, while the federal government lags behind.