Although the tap-water ban was lifted in the wake of West Virginia's Elk River chemical leak, the long-term ecological impacts of the spill remain uncertain.

On Monday, the 300,000 residents of nine counties in West Virginia were told that they could resume drinking and using their tap water, five days after an estimated 5,000 gallons of the chemical 4-methylcyclohexane methanol (MCMH) leaked into the Elk River near Charleston.

Working with state officials, the utility lifted the ban on drinking water gradually in the region on Monday, so the system would not be overwhelmed by demand. Customers were asked to flush out their water pipes before using any of the water. The utility said the water could still have a faint