Researchers from Duke University recently found high concentrations of radioactive contaminants in coal ash from three major U.S. coal-producing basins. Compared to normal soil, the researchers found that this ash was five times more radioactive, and up to 10 times more radioactive than its parent coal. This raises concerns of how coal ash may affect environmental and human health. 

According to a news release, the researchers collected samples of coal and coal ash from the nation's three major coal-producing areas--the Illinois, Appalachian and Powder River basins--to compare their radioactivity. 

"Until now, metals and contaminants such as selenium and arsenic have been the major known contaminants of concern in coal ash," Avner Vengosh, professor of geochemistry and water quality at Duke's Nicholas School of the Environment, said in the release. "This study raises the possibility we should also be looking for radioactive elements, such as radium isotopes and lead-210, and including them in our monitoring efforts."

From their study, the researchers found that the Illinois basin had the highest levels of radioactivity. The Appalachian basin had the second-highest, followed by the Powder River, which is located in Wyoming and Montana. According to their study, the ratio of radium and uranium in the parent coal was also consistent with that found in the remaining coal ash.

"This means we can predict how much potential radioactivity will occur in coal ash by measuring the uranium content in the parent coal, which is easily discerned," Vengosh explained in the release. "This analysis can be applied to all coal ash worldwide, and is useful information for regulators, industries and scientists alike."

Even though the isotopic ratios of coal and coal ash varied between basins, they remained uniform within each individual one. This makes each basin easily distinguishable, which can help researchers better predict the source of contamination.

The researchers also found that when coal was burned, radium became concentrated in coal ash, while the lead reattached to fly ash, making it more radioactive, according to the release.

"Radioactive radium and lead-210 ends up concentrated in these tiny particles of fly ash, which though individually small, collectively comprise the largest volume of coal ash waste going into holding ponds and landfills," Nancy Lauer, lead author and Ph.D. student in Vengosh's lab, said in the release. "Because of the tiny size of the fly ash particles, they are much more likely to be suspended in air if they are disposed in a dry form. People breathing this air may face increased risks, particularly since tiny particles tend to be more enriched in radioactivity,"

U.S. power plants can limit the amount of toxins that escape into the air when coal is burned by installing smokestack scrubbers, but this does not prevent against leaks from landfills or spills that pose major threats, as the release noted.

Currently coal ash disposal sites are not monitored for radioactivity. However, the U.S. Environmental Protection Agency has planned to implement the first-ever regulations on the disposal of coal ash this October. Researchers believe that this study opens the door future evaluation of how these contaminants affect human health and the environment, according to the release.

Their study was recently published in Environmental Science & Technology.

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