The chemical that contaminated West Virginia's Elk River is one among tens of thousands of industrial compounds that haven't been tested for their risks to human health, several experts said Friday. Water quality authorities now trying to certify when local tap water might be safe again have little to guide them.

"West Virginia is getting a hard lesson in how little we know about these chemicals," said environmental engineer Scott Simonton at Marshall University in Charleston, W.Va., who studies water quality issues....