urring 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 that the state was misleading homeowners regarding how safe their drinking water was by citing safe drinking water guidelines set by the federal government.
The consequence of that deposition was severe blowback from top administration officials. McCrory's chief of staff, Thomas Stith, accused Rudo of lying under oath. However, Rudo has maintained the veracity of his testimony both in a public statement and in a subsequent deposition. As a result of the controversy, North Carolina's chief epidemiologist, Dr. Megan Davies, resigned in protest against the "false narrative" that the administration was circulating about coal ash.
Currently there is no federal drinking water standard for chromium-6, though there is one for total chromium of 100 parts per billion. It assumes that most of the chemical will be of the nontoxic chromium-3 variety.
Out of all 50 states, California is the only one with a statewide chromium-6 standard, which is set at 10 parts per billion.
It is this dearth of guidance and jumble of regulations, said Vengosh, that makes it difficult for those who rely on wells for their drinking water to know how to react.
"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.
Vengosh cautioned that he was not a health expert, but said that California's hexavalent chromium standard appears to be a reasonable point at which concern should begin. The study discovered wells—both close to and far from coal ash pits—that exceeded the standard.
This fact, according to Vengosh, will probably pressure additional states to set their own chromium-6 standards, and it also indicates the necessity for the federal government to set guidelines rather than leaving the problem to the states.
"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."