The Freedom Industries facility sits on the banks of the Elk River last Friday, in Charleston, W.Va., site of a chemical spill that has led to a ban on using tap water in the area. The CDC says pregnant women in affected areas should drink only bottled water. Tom Hindman/Getty Images hide caption

itoggle caption Tom Hindman/Getty Images

An air-monitoring station near the TVA Kingston Fossil Plant in Kingston, Tenn. Stations such as this one are used to monitor clean-air compliance of TVA coal-fired plants. Wade Payne/AP hide caption

itoggle caption Wade Payne/AP

State and local leaders break ground at a Louisville, Ky., coal-burning power plant in November 2012. Dylan Lovan/AP hide caption

itoggle caption Dylan Lovan/AP