paraphrase

Original

“At issue is coal's content of uranium and thorium, both radioactive elements. They occur in such trace amounts in natural, or "whole," coal that they aren't a problem. But when coal is burned into fly ash, uranium and thorium are concentrated at up to 10 times their original levels.

In a 1978 paper for Science, J. P. McBride at Oak Ridge National Laboratory (ORNL) and his colleagues looked at the uranium and thorium content of fly ash from coal-fired power plants in Tennessee and Alabama. To answer the question of just how harmful leaching could be, the scientists estimated radiation exposure around the coal plants and compared it with exposure levels around boiling-water reactor and pressurized-water nuclear power plants.

The result: estimated radiation doses ingested by people living near the coal plants were equal to or higher than doses for people living around the nuclear facilities.”

Paraphrase

According to Mara Hvistendahl in an article for Scientific American, the radioactive trace elements of thorium and uranium present in unburned coal are concentrated up to ten times in the fly ash that results after burning. She quotes a study done for Science in 1978, which concluded that people who were living near coal plants took in radiation from the environment at levels that were similar to or higher than those who lived near nuclear plants.