Duke University researchers have confirmed what many people in Kingston, Tenn., already knew: Dust and river sediment containing toxic metals and radioactivity from the Dec. 22, 2008, coal ash spill can harm human health and the environment.

The Duke study was published earlier this month in the online version of the journal Environmental Science & Technology.

Scientists analyzed radium, arsenic (both can cause cancer) and mercury in the wet coal-ash sludge and determined that when it dries, the sludge becomes toxic dust.

The particulates are so smallthe size of bacteriathat they can burrow deeply into the lungs. People with lung infections, asthma, emphysema and even diabetes are particularly at risk. While federal and Tennessee environmental officials say their monitoring hasn’t detected airborne dust at levels above national air quality standards, that doesn’t mean the dust isn’t present.

Even the fish are threatened. Mercury in the water breaks down into methylmercury, which accumulates in fish tissue. People who eat the fish also risk accumulating unsafe levels of methylmercury in their bodies.

North Carolina has 12 containment ponds, which combined contain 1.3 million tons of coal ash. Duke Energy and Progress Energy own the ponds. (See “EPA rates 12 N.C. coal residue impoundments with a ‘high hazard potential’.”)

“There are hundreds of similar coal-ash storage ponds located in the United States, and all are located next to rivers,” Avner Vengosh, associate professor of earth and ocean sciences at Duke’s Nicholas School of the Environment said in a release about the study. “Yet the water in these containment ponds is not regulated.”