Tomblin emphasized that the U.S. Centers for Disease Control and Prevention has said the water is safe as long as it contains less than 1 part per million of the coal-cleaning chemical, which leaked into the Elk River from the Freedom Industries tank farm 1.5 miles upstream from the water intake.

Outside public health experts, though, have said the lack of much data on the chemical -- not an unusual situation for most chemicals -- makes it hard to be sure the CDC number is adequately protective, especially for young children.