Terry Gross

In August 2015, Dr. Mona Hanna-Attisha was having a glass of wine in her kitchen with two friends, when one friend, a water expert, asked if she was aware of what was happening to the water in Flint, Mich.

Hanna-Attisha, a pediatrician in Flint, knew that the city had changed its water source the previous year. Instead of channeling water from the Great Lakes, residents were now drinking water from the nearby Flint River. She had been aware of some problems with bacteria after the switch, but she thought everything had been cleared up.