eats posed by coal ash contamination. He noted that his previous work as well as other research indicates that coal ash was leaking from the sites where it is stored into water supplies, thereby spreading selenium and arsenic into well water.
"The bottom line is that we need to protect the health of North Carolinians from the naturally occurring threat of hexavalent chromium while also protecting them from harmful contaminants, such as arsenic and selenium, which our previous research has shown do derive from leaking coal ash ponds," he said. "The impact of leaking coal ash ponds on water resources is still a major environmental issue."
The findings contradict two major assumptions about hexavalent chromium made prior to the study. For a long time, scientists have assumed that significant levels of the toxin are indications of human activities.
The study, however, shows that the high levels of the chemical found in well water should not necessarily be blamed on coal ash.
"There are still a lot of questions that will need to be scrutinized in the study," said Sam Perkins, the Catawba Riverkeeper. Perkins is one of many environmental advocates who have been pressuring Duke Energy to clean up coal ash sites.
"However, decades of research has concluded that hexavalent chromium 'rarely occurs naturally,'" he added, referring to the EPA's topological profile for chromium-6.
Perkins believes that the discovery of naturally-occurring hexavalent chromium should not lessen the pressure to clean up coal ash from unlined pits located throughout the state.
"The most important thing to remember is that Dr. Vengosh's research has for years identified problems and contamination from unlined coal ash," Perkins said. "A paper from Dr. Vengosh earlier this year concluded unlined coal ash was indeed contaminating groundwater. Duke Energy's own data and engineering reports have confirmed this."
This is not the first time the chemical has been found in nature. As Vengosh noted, studies in both California and Mexico found naturally-occurring chromium-6 leaking into water from rock formations. However, he said, this is the first time that it seems to have happened from the kinds of rock found in North Carolina.
Debates over exposure to the chemical have also brought up the environmental balance between chromium-6 and chromium-3, a less toxic chemical relative. Although high levels of the letter can be poisonous, the EPA says that it is an "essential human dietary element" in fruits, vegetables, and meat. It is harder and more expensive to test for a particular kind of chromium than for total chromium, and it has most often been assumed that most of the chemical measured would be of the nontoxic kind.
David Buchwalter is an associate professor in North Carolina State University's Department of Biological Sciences. "In normal groundwater environments, you'd expect most of the chromium to be chromium-3," he said.
But according to Vengosh's study, the Piedmont of North Carolina is not a typical environment.
"The concentration of hexavalent chromium in groundwater is almost identical to the concentration of total dissolved chromium, measured by a totally different technique" Vengosh said. "That means, when you will find chromium in groundwater, it is actually composed of its toxic form of hexavalent chromium, not the less toxic trivalent form."
This fact, said Buchwalter, raises "a big red flag" about how safe the drinking water is in the wells located in the studied area. According to him, the paper brings up more pressing matters besides the policy issues on coal ash that it may address and the future research it could inspire.
"My first inclination would not be a research question, but a practical question of how we're going to provide safe water for these people," he said.
The questions regarding the meaning of the presence of chromium have been at the center of an unusual and very public dispute between Governor McCrory's administration and a number of the state's top public health scientists. State toxicologist Ken Rudo alleged in depositions 