Flint's parents are not stupid. The moment they found out there's a problem they switched their kids to the bottled water that was being given away for free.
This does not stop lying Congresscritters from claiming they are poisoned. It makes great demagoguery. They've been playing from the "Republicans want to poison your kids with dirty air and water!!" script since the first Earth Day. The LIVs lap it up like anti-freeze.