A top environmental official at the Centers for Disease Control and Prevention said the scientific community is just beginning to grasp the scope of how much drinking water could be contaminated with a potentially toxic class of industrial chemicals.

The presence and concentrations of perfluorinated chemicals in U.S. drinking water is “one of the most seminal public health challenges for the next decades,” Patrick Breysse, a senior official at the CDC, said at an Oct. 17 conference in North...