A New Hampshire town finds out their water has been contaminated by a chemical. Their most basic question — whether the water is safe to drink — doesn’t have a clear answer. Nobody seems to know much about this so-called forever chemical, which is weird because… this has all happened before.

From the Document team at New Hampshire Public Radio, Safe to Drink is a four-part series about the water contamination story that keeps repeating in town after town — and about the people who fought for answers through a maze of chemistry, regulations, and illnesses.