Radioactive contaminants are present in ash from all three of the major U.S. coal-producing regions, Duke University researchers say in a paper published Tuesday.
Coal ash has gotten attention mostly for the elements in it, such as arsenic and selenium, that reach toxic doses in water. The Duke-led study may add to public health and environmental concerns over the material.
Researchers found that levels of radioactivity in ash were up to five times higher than in soils and up to 10 times higher than in coal itself. Burning coal concentrates radioactivity, metals and other contaminants left in ash.
The Duke study found coal and ash from the Illinois basin held the most radioactivity, followed by the Appalachian and Powder River region of Wyoming and Montana.
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The Environmental Protection Agency, in contrast, says coal ash is only slightly more radioactive than average soil. Duke Energy, which recently sampled groundwater near ash ponds for a broad range of radioactive isotopes, says radioactive elements were not detected or were extremely low, similar to what's in soil.
Radium isotopes and lead-210 occur naturally in coal. The Duke team says that when coal is burned, radium and lead-210 become concentrated and attach to tiny particles in fly ash.
Fly ash is a lightweight material that’s captured as it goes up power plant smokestacks. Duke Energy and other utilities have for years stored the ash mixed with water.
Now utilities are transitioning to ash stored in dry form. That makes the tiny, radioactive-enriched particles more likely to float in the air, where people could breathe them in, the Duke researchers said.
If ash stored in landfills can’t be controlled, such as by wetting or covering it with vegetation, communities downwind could be at risk, said Duke’s Avner Vengosh.
Those risks would have to be evaluated in further research, he said, but suggests radioactive elements in ash should be more closely monitored.
The state Department of Environment and Natural Resources, in assessing Duke’s power plants under the North Carolina coal ash law, says it is doing limited sampling for strontium, uranium and radium.
The study, whose lead author was Ph.D. student Nancy Lauer, was published Tuesday in the journal Environmental Science & Technology.