Green Glossary: Coal Ash

A frightening Christmas week accident in Tennessee—called what may be the nation's largest such spill-brought notoriety to the term "coal ash." Here's how the New York Times described the accident: "The spill took place at the Kingston Fossil Plant, a generating plant about 40 miles west of Knoxville on the banks of the Emory River, which feeds into the Clinch River, and then the Tennessee River just downstream." Coal ash is term used to describe residues generated in the combustion of coal.

Even though coal ash has been found to contain "contain significant quantities of heavy metals like arsenic, lead and selenium, which can cause cancer and neurological problems," authorities predictably played down the danger. "Most of that material is inert," said Gilbert Francis Jr., a Tennessee Valley Authority spokesman. "It does have some heavy metals within it, but it's not toxic or anything." Regardless, the spill is likely to reignite a much needed debate over whether "the federal government should regulate coal ash as a hazardous material."

The Times added: "United States coal plants produce 129 million tons of postcombustion byproducts a year, the second-largest waste stream in the country, after municipal solid waste." A 2007 E.P.A. report said that over about a decade, "67 towns in 26 states had their groundwater contaminated by heavy metals from such dumps."