updated 1/29/2009 3:46:28 PM ET 2009-01-29T20:46:28

High levels of arsenic and elevated levels of radioactive radium have been found in the sludge released in a massive coal ash spill at a Tennessee power plant, Duke University scientists reported.

The scientists, working with the United Mountain Defense coal industry watchdog group, on Wednesday said results of their environmental testing raise "questions about the safety of storing ash" and the need for caution during the cleanup to make sure toxins don't escape the site.

Otherwise, they said, "exposure to radium- and arsenic-containing particulates in the ash could have severe health implications" for those living near the plant. Both substances are potential carcinogens.

Some 1.1 billion gallons of sludge containing 5.4 million cubic yards of coal ash breached an earthen holding facility Dec. 22 at the Tennessee Valley Authority's Kingston Fossil Plant, about 40 miles west of Knoxville, damaging a dozen lakeside homes and posing an environmental threat to the community.

TVA has been spending $1 million a day on a gigantic recovery effort, vacuuming ash particles from the river and scooping the sludge out of inlets. The agency also has built temporary dams and distributed by helicopter more than 80 tons of grass seed to hold the rest in place.

The Tennessee Department of Environment and Conservation is overseeing the cleanup with help from the Tennessee Department of Health and the U.S. Environmental Protection Agency.

EPA spokeswoman Dawn Young and TDEC spokeswoman Tisha Calabrese-Benton said it was difficult to comment on the Duke research without seeing the work, while TVA issued a statement saying it was "eager to review the findings."

"I can tell you, however, that (TDEC) is working in close coordination with (other the agencies) for the protection of public health in the area of the spill and to ensure that the area is appropriately cleaned for the long-term protection of both the community and the environment," Calabrese-Benton said.

"We have stated throughout this process that coal ash does contain small amounts of some contaminants that could be harmful to human health under certain conditions, primarily ingestion and inhalation," she added. "From the point TDEC was initially notified of the ash release, the department recognized the potential inhalation hazard presented by the ash and acted to protect local public health."

The Duke tests did find only trace amounts of arsenic away from the site, in river water a couple of miles downstream. That confirms continued monitoring by state and federal agencies that has found drinking water safe, as well as air quality remaining clean.

Avner Vengosh, associate professor of earth and ocean sciences at Duke, said that he and graduate student Laura Ruhl collected solid ash and water samples from an ash-filled inlet of the Emory River and water samples a couple of miles downstream on Jan. 9 some three weeks after the mishap.

Vengosh's team found a combined content of radium-228 and radium-226 of 8 picocuries per gram in the solid ash samples, compared with an average 5-6 picocuries per gram reported by EPA in most bottom and fly ash.

They also found arsenic levels of 95 parts per billion in water in the ash-filled inlet, but low concentrations downstream in the Emory and Clinch rivers. The EPA standard for safe public drinking water is less than 10 parts per billion.

"The good news is we detected only trace amounts in waters beyond the dammed tributary," Vengosh said. "The data suggest that in less than three weeks since the spill, river flow has diluted the arsenic content.

"The river is clean, but the water from areas like the dammed tributary, where the coal ash accumulated, still contains high arsenic levels."

TVA said Duke's radiation and arsenic levels "differ significantly from those found by TVA and independent labs."

"We still take the Duke report very seriously and will have the site rechecked," the agency said.

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