Raleigh, N.C. — A Duke University study released Wednesday morning suggests that families who rely on well water need to be wary of a cancer-causing chemical at the heart of North Carolina's coal ash controversies even if they live nowhere near a current or retired power plant.
The study finds that hexavalent chromium, a carcinogen many people know from the movie "Erin Brockovich," can leach into groundwater from certain kinds of rock formations strewn throughout the North Carolina Piedmont, an area that cuts a broad swath through the central part of the state. More than 90 percent of the wells sampled for the Duke study had detectable levels of the chemical.
Along with selenium, lead and arsenic, hexavalent chromium, or chromium-6, is one of the toxins scientists have been most concerned about when they study whether coal ash is contaminating local water supplies near 14 current and former coal-fired power plants. Controversy over advising well owners near coal ash pits about whether their water was safe to drink, and specifically what kind of health risk hexavalent chromium poses, is at the center of an ongoing controversy enveloping Gov. Pat McCrory's administration and some of North Carolina's top public health scientists.
The new paper indicates that coal ash is likely not the culprit that deposited chromium-6 in wells near those power plants.
"I don't think they should be relieved by this information. This is an indication they have a much bigger problem," said Avner Vengosh, professor of geochemistry and water quality at Duke’s Nicholas School of the Environment and the study's lead author. "The fact we are evaluating a naturally occurring source doesn't mean we're giving a green light to coal ash."
The study was published Wednesday in the Environmental Science and Technology Letters, a peer-reviewed journal.
Vengosh said this latest finding raises the specter of a larger public health issue in addition to any threats posed by coal ash contamination. He pointed to his prior work and other research indicating that coal ash was leaching from its storage sites into water supplies, spreading selenium and arsenic.
"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," Vengosh said. "The impact of leaking coal ash ponds on water resources is still a major environmental issue."
Officials with the North Carolina's Department of Environmental Quality, which is responsible for addressing environmental threats, declined to comment for this report.
Almost always toxic in North Carolina
The findings in Vengosh's study run counter to two major assumptions about hexavalent chromium. In particular, scientists have long assumed that significant levels of chromium-6 are markers of human activities.
The Duke paper indicates the high levels found in North Carolina wells shouldn't 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, one of many environmental advocates who have pushed Duke Energy to clean up coal ash sites.
"However, decades of research has concluded that hexavalent chromium 'rarely occurs naturally,'" he added, pointing to the EPA's topological profile for chromium-6.
Vengosh's finding that there is naturally occurring chromium-6, Perkins said, shouldn't dampen the push to clean up coal ash from unlined pits across 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."
Finding hexavalent chromium in nature isn't a completely new finding. Vengosh points out that studies in California and Mexico found naturally occurring hexavalent chromium leaching into water from rock formations rich in the material. But this is the first time it has appears to have emerged from the sort of rocks found in North Carolina, he said.
Debates over chromium exposure have also focused on the environmental balance between chromium-6 and its less toxic cousin, chromium-3. Although high levels of Chromium-3 can be toxic, the EPA describes it as an "essential human dietary element" found in fruits, vegetables and meat. It's easier and cheaper to test for total chromium rather than a particular variety, and the most common assumption has been the bulk of chromium measured would be the nontoxic variety.
"In normal groundwater environments, you'd expect most of the chromium to be chromium-3," said David Buchwalter, an associate professor in North Carolina State University's Department of Biological Sciences.
But Vengosh's paper argues North Carolina's Piedmont 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 explained. "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."
That, Buchwalter said, raises "a big red flag" about the safety of drinking water drawn from wells in the studied area. Buchwalter read Vengosh's paper at the request of WRAL News. He said that beyond the coal ash policy issues it may address and further research it could inspire, the study points to more pressing considerations.
"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.
No standards exist
Those questions of what the presence of chromium means have been at the heart over an unusual and very public spat between the McCrory administration and some of the state's top scientists. In depositions, Ken Rudo, a state toxicologist, alleged the state was misleading homeowners about the safety of their drinking water by citing federal safe drinking water guidelines.
That deposition led to harsh blow back from top administration officials. Thomas Stith, the governor's chief of staff, called a late-night news conference to accuse Rudo of lying under oath. Rudo has stood by his statements both in a rare public statement as well as a subsequent deposition. The controversy prompted Dr. Megan Davies, the state's chief epidemiologist, to resign in protest over the "false narrative" that the administration was laying out over coal ash.
The issue is complicated, but there currently is no federal drinking water standard for hexavalent chromium. There is a standard for total chromium of 100 parts per billion, which assumes most chromium will be nontoxic chromium-3.
Of the 50 states, only California has a statewide chromium-6 standard, set at 10 parts per billion.
That lack of guidance and mishmash of regulations makes it hard for well-owners to know how to react, Vengosh said.
"If you are a homeowner and you have these values for chromium, you really don't know how it relates to any health standard," he said.
Cautioning that he was not a health expert, Vengosh said the California standard for chromium-6 seems to be a reasonable point for concern. His paper found wells, both near coal ash pits and far from them, that exceeded that standard.
That, he said, will likely prod more states to set their own standards for chromium-6 and points to a need for the federal government to set guidelines rather than leave states to wrestle with these questions.
"We need urgently a standard for hexavalent chromium," Vengosh said. "We need to know what thousands of well owners should be doing. ... This is an emergency even worse than coal ash."