Duke Scientist Discusses Study Of Carcinogen, Coal Ash

Oct 27, 2016

As Duke Energy and environmentalists have debated the safety of private wells near coal ash ponds, they've disagreed about the source of a carcinogen called hexavalent chromium. Scientists at Duke University figured out how to identify the chemical’s source. Conclusions from the study of 376 private wells say coal ash likely isn't to blame. WFAE's David Boraks talked with the study's lead author, Avner Vengosh about his research and recommendations.

Avner Vengosh
Credit Duke University

VENGOSH: This study's part of kind of a long-term study, that we've been investigating the water quality in North Carolina. And we also were investigating coal ash and how coal ash affects the environment.

And we found that unlike previous thinking, that hexavalent chromium is not derived from human activities, or anthropogenic sources, but rather is naturally occurring, and basically arrives in many parts of the Piedmont groundwater in North Carolina and (beyond).

Q: Is this finding surprising? Does this show a problem that we don't know about, or might not have focused on so much?

VENGOSH: Absolutely, I mean if you go to the EPA website, you see (the) major conceptual idea was that hexavalent chromium was very rare, and not stable in groundwater, and if we do find it, it's indicating that you have some industry involved. Where, what we're finding is it's a very common and different level of contamination. And the really kind of surprising and amazing results that's coming from the study that everywhere that we see chromium it's actually composed of this hexavalent chromium which is extremely abundant throughout the Piedmont area.

Q: So it's coming from naturally occurring rock?

VENGOSH: Right, so it's coming from rocks, we see that some rocks contribute more chromium than others. So we have some idea to see where to look for it. But basically the data shows that it's coming from interaction of the ground water with rocks.

Q.  So, not human sources as we've thought in the past.


Q. Duke Energy is responding to this news and saying that coal ash basins are now ruled out a source of hexavalent chromium in wells, and I guess that's what you're saying. Does that mean we don't have to worry about anything?

VENGOSH: Absolutely not.  I'm very happy that Duke Energy is supporting our research. And if it's the case, they should look at what we just published a couple of months ago, that we showed that all coal ash ponds in North Carolina are leaking into the environment and causing contamination of shallow ground water and surface water nearby.

So coal ash ponds are a serious threat to the health and to the environment in North Carolina. Now what we are saying is that hexavalent chromium is a separate problem and it's not related to the coal ash. But we do not say that the coal is clear, and in fact we do have very strong evidence that (it is) contaminating the environment with other contaminants like arsenic, selenium, boron, strontium, and these contaminants are existing already in the groundwater resources in North Carolina.

Coal ash ponds at Duke Energy's Riverbend Steam Station in Mount Holly in January.
Credit David Boraks / WFAE

Q. Is there more research underway?

VENGOSH: Yes, we are just in the beginning. And in the next stage, we will try to get a more larger data set, and more information for predicting where and what circumstances you would have elevated levels.

And I think one of the things that should come out from this paper is the notion that a standard should be set for hexavalent chromium.  One of the problems that homeowners are kind of facing is that there's not any official drinking water standard for hexavalent chromium in the United States.

And this lack of ... reference is making things much more complicated because we really don't know what is a safe level, because there is no standard.

HOST: That’s Duke University scientist Avner Vengosh talking to WFAE environmental reporter David Boraks about a study that found coal ash likely isn’t to blame for hexavalent chromium in wells near coal ash ponds. 


June 10, 2016, Duke.edu, "Coal Ash Ponds Found to Leak Toxic Chemicals"

June 10, 2016, Environmental Science & Techology, "Evidence for Coal Ash Ponds Leaking in the Southeastern U.S."

Oct. 26, 2016, Duke.edu, "Hexavalent Chromium is widespread in N.C. wells, but not linked to coal ash"

Oct. 26, 2016, Environmental Science & Technology Letters"Origin of Hexavalent Chromium in Drinking Water Wells from the Piedmont Aquifers of North Carolina"