The state's governor says up to 5,000 gallons (18,927 liters) of the industrial chemical 4-methylcyclohexane methanol, or Crude MCHM, leaked into the river Thursday. A state of emergency for nine counties went into effect yesterday; the President has issued a declaration of emergency. Schools and businesses in Charleston are closed.
The chemical, which smells like licorice, can cause headaches, eye and skin irritation, and difficulty breathing from prolonged exposures at high concentrations." NYT:

The owner of the ruptured tank, Freedom Industries, processes and stores chemicals used in the coal industry in 14 tanks on the Elk River, 2.5 miles upstream from the junction of the Kanawha River in downtown Charleston. An Environmental Protection Agency report on the chemical facility showed no violations in the last three years.