American Scientist

Avner Vengosh, a geochemist at Duke University, has provided a balanced scientific perspective on contentious water issues, from water quality and sharing issues in Jordan, Israel, and Palestine, to those related to hydraulic fracturing in the United States. His article on uranium in the groundwater in India was among the editor’s choices for best papers of 2018 in the journal Environmental Science & Technology Letters. Vengosh testified last April at a U.S. Congressional briefing on the Environmental Protection Agency’s coal ash amendments. He spoke to special issue editor Katie L. Burke about his research.

Among the issues that you are looking at, what do you see as the most dire?

I have noticed that people look at the future in terms of water availability: How much water is available for how many people? But in those calculations, they don’t take water quality into account. The fact that you have such-and-such volume of water doesn’t mean that it’s good water to consume.

You can think about water quality as two issues. The one that keeps everyone alert is the man-made contaminants—anthropogenic contaminants—that can leach out from wastewater treatment plants into water resources.

There is a huge difference in the types of anthropogenic contaminants between the developing and the developed world. In the developed world, the issue is microcontaminants coming from drugs or from pesticides. In developing countries, wastewater is the number one source of anthropogenic contamination, and basic contaminants such as pathogens and nitrate are the predominant sources of contamination. They have the largest impact in terms of human health in the developing world, especially in Africa and some places in India, where wastewater is not treated.

The more hidden contaminants are what we call the geogenic contaminants. These are the contaminants that are coming from aquifer rocks, typically in groundwater. You don’t get sick immediately from consuming this water. In some ways, geogenic contaminants are more dangerous than anthropogenic contaminants because you don’t see them and you don’t feel them, and you think that they are part of nature. But many studies have demonstrated that they have toxic effects.

I’m talking about arsenic or hexavalent chromium that we are finding in North Carolina in concentrations above what health regulations recommend. I’m talking about uranium, which we are finding in groundwater all over India. Fluoride is a very common naturally occurring contaminant that is causing fluorosis in Africa, South America, and India. And salinity is a naturally occurring contaminant that is not only problematic for human health, but also affects agricultural water use (see "A Delta in Peril"). There may be enough water, but the water quality becomes a limiting factor.

How did you end up studying uranium in the groundwater in India?

For the past two or three years, my team and I have been studying water quality in India. When we tested the water in our lab, we were struck by the very high concentration of uranium in the groundwater sample from Rajasthan. At first we thought, “Maybe that’s a localized area with high uranium.” But then we tested a sample from Gujarat— which is a different Indian state—that was similarly high in uranium.

We started to look for literature on this issue, and we found isolated papers reporting relatively high levels of uranium in the groundwater. When we integrated all the data, we found that there is a systematic pattern in which the overuse of groundwater led certain aquifers under certain chemical conditions to become oxidized. This oxidation induced high solubility of uranium in the groundwater.

When we integrated all the data, we found that there is a systematic pattern in which the overuse of groundwater led certain aquifers under certain chemical conditions to become oxidized. This oxidation induced high solubility of uranium in the groundwater.

Uranium is not a localized groundwater issue as we had previously thought; it’s occurring all over India. In some places it is higher than others, and we are still studying what specific factors determine high levels of uranium in the groundwater. Is it the geology we can see? Is it the pH condition of the groundwater? Is it the oxidation? Combining those factors, we see a higher prevalence of uranium under certain geological type of aquifer rocks, in types of geochemical conditions that enable uranium to be more enriched in local groundwater.

This contamination is a large-scale phenomenon in India and could be affecting other countries that have similar geological and geochemical conditions. Long-term exposure to uranium can result in kidney diseases, which are a major health issue in places like Rajasthan.

What other natural contaminants have you found in the water?

In addition to uranium, we found high concentrations of fluoride, which is a tricky element. We need it when we grow up, but if we have too much of it, it causes fluorosis. Fluoride is incorporated into the material of our bones and teeth, the mineral apatite. And when we have too much fluoride, especially in the period when children are moving from nursing into drinking water, it can start to accumulate. In the case of mild fluorosis, it will affect the color of the teeth. More severe fluorosis will cause teeth degradation with a lot of pain. And in even more severe cases, fluoride is incorporated into the bones and causes those children to become crippled. It’s a really widespread issue not only in India, but also in Africa and Central America, as well as some other areas.

How are people in India responding to the groundwater contamination?

Given the groundwater quality, which people are now coming to understand is problematic, they want to replace much of the groundwater supply with surface water. But in a place like Rajasthan, surface water needs to be imported from the Himalayas or from other states in India. You need to bring the water. When you bring water from one state to another, people start to talk about water wars (see "Dying for a Drink").

We are working now with people from the state of Punjab in India to convert groundwater into surface water. The idea is to take water from canals that are already established, but then, the communities downstream will be affected. I can see a major potential conflict within India and also with areas of Pakistan that are downstream from this region. And because the groundwater table is going down so dramatically, and given the drought and also the depletion of the surface water, this conflict over water is going to be a major issue in the future. It’s all connected.

When we’re doing research, it is always important to consider how it will affect people and regulation. Sometimes it’s not simple, because of government resistance or water authorities. We are forcing them to engage with different issues.

How did you end up testing for hexavalent chromium in North Carolina?

The North Carolina Department of Environmental Quality discovered that in some parts of the state, drinking water wells located near coal ash ponds have high levels of hexavalent chromium—high levels meaning 20 parts per billion, whereas North Carolina recommends no more than 0.07 parts per billion (see the 2016 paper in Environmental Science and Technology Letters). Hexavalent chromium is potentially carcinogenic. People who have seen the movie Erin Brockovich know it is about water contamination from the industrial production of hexavalent chromium.

When we started this study, everybody was convinced that industrial production was the source of all the hexavalent chromium in the world. People thought that hexavalent chromium contamination [in North Carolina] came from coal ash leaking into the groundwater and flowing into wells that are located near the coal ash ponds.

We had assumed, “Okay, we found hexavalent chromium in the well water, there must also be the other contaminants that occur in coal ash.” But we didn’t find them. The chemistry had nothing to do with what we expect to find with coal ash contamination. So we widened our search and collected samples from wells 10 miles, 50 miles, 100 miles away. And we found hexavalent chromium everywhere, regardless of the distance or proximity to a coal ash pond.

We’re going to reach a point where there will be no alternative but to put resources into improving water quality.

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We started to see a pattern where hexavalent chromium contamination would occur mostly in specific rocks that contain chromium. On the coast, the aquifer is composted of sedimentary rocks that do not contain chromium. But in the Piedmont [region of North Carolina], some rocks—such as basaltic rock, which were found near the coal ash ponds—are more likely to have higher chromium levels than other types of rocks. We did the mapping and found that, first, hexavalent chromium is everywhere, not only in those wells near coal ash ponds. And second, it’s geogenic and has nothing to do with anything man-made.

When we’re doing research, it is always important to consider how it will affect people and regulation. Sometimes it’s not simple, because of government resistance or water authorities. We are forcing them to engage with different issues.

Is there any way to filter these naturally occurring contaminants out of the water so that you can still drink it?

Any contaminants can be treated, especially if it’s a charged element. Reverse osmosis will remove anything in the water that is charged. For elements such as uranium, fluoride, and hexavalent chromium, reverse osmosis desalination will take it out. But contaminants that are not charged, such as arsenic III, will go through. So, in principle, to take care of arsenic, you need something more than just reverse osmosis.

What do you see as the future of water quality?

Water quality has been relatively neglected and treated as secondary to water supply, but we’re going to reach a point where there will be no other alternative but to put resources into improving water quality.

At the end of the day, the technology is there to do that. The problem is the readiness to pay, and the ability of the political and administrative infrastructure to enforce and to carry out the needed technological remediation. If you’re looking from the perspective of pure technology, there are no limitations. The real limitation is the huge cost. And even more, the recognition that we have no choice but to pay, and to put resources into water quality.

An extended interview with Avner Vengosh is below.