A study of lead service lines in Flint's damaged drinking water system reveals a Swiss cheese pattern in the pipes' interior crust, with holes where the lead used to be.The findings—led by researchers at the University of Michigan—support the generally accepted understanding that lead leached into the system because that water wasn't treated to prevent corrosion. While previous studies had pointed to this mechanism, this is the first direct evidence. It contradicts a regulator's claim earlier this year that corrosion control chemicals would not have prevented the water crisis.