How plants could help us detect, and even destroy, dangerous ‘forever chemicals’ – Grist todayheadline

The vision

“I think a lot of people now are aware of PFAS, or concerned about it, or want to know whether it’s present in their water, their food. The whole purpose of what we’re trying to do is develop something that’s simple and cost effective to answer that question for them.”

— Bryan Berger, professor of chemical engineering at the University of Virginia

The spotlight

Last fall, we wrote a story about how a group of researchers, together with the Mi’kmaq Nation in Maine, have been working to address contamination from PFAS — per- and polyfluoroalkyl substances, a group of pernicious, human-made chemical compounds sometimes known as “forever chemicals.” The substances, which have been increasingly linked to health issues, are a common problem for farmers and other landowners in the state of Maine. The group had seen some early success using hemp plants to draw PFAS out of the soil, on a parcel of land the tribe had acquired at a former Air Force base. But many questions remained — for them and others working on this issue — about how the chemicals travel and accumulate, what safe uses for contaminated land might be, and how to actually break down these forever chemicals.

“I think everybody is struggling with that question, trying to figure out, what does ‘forever’ mean? How long will it persist in soil? How will it transport through the environment?” Bryan Berger, one of the researchers, told me at the time. In addition to the work with the Mi’kmaq Nation’s hemp experiment, his lab has been looking at a range of ways that the plant kingdom might help us track and maybe even eliminate PFAS contamination.

I’ve been eager to follow up with Berger, a chemical engineer at the University of Virginia, about what he and his collaborators have learned so far in striving to answer those questions. At the time, the group had just received a four-year grant from the Environmental Protection Agency to continue studying the remediation potential of hemp plants, as well as other pursuits, like how to give farmers better testing tools to know when their land is contaminated. But over the past couple of months, as with so many research projects, the group has faced setbacks. Their grant (already approved by Congress) was unexpectedly terminated in May, along with a slate of other grants focused on PFAS research — previously considered a pretty nonpartisan issue.

The group appealed, and the EPA reinstated their grant in late June, with no further explanation.

“Because of this whole situation, I don’t feel as totally sure about [the funding] as I did when we first got the grant,” Chelli Stanley, co-founder of an environmental organization called Upland Grassroots and one of the key collaborators on the Maine project, told the Maine Morning Star. “But of course, we are just going to go forward and do all of our work, I’m sure maybe at an accelerated pace in some ways, just to do as much testing as we can.”

As Berger shared with me, that work is still in its early stages, but has yielded some exciting results for the team.

One of the first questions in the battle to try and contain PFAS is whether the chemicals are present in a given area — say, a farm or a field — and if so, where they might be coming from. The mounting evidence that PFAS may be hazardous to human health has led the chemicals to be banned in many places. “The expectation was that you should see a reduction in PFAS levels accumulating in soil and crops,” Berger said, “but that has not happened.” There are still unregulated sources causing the substances to spread.

Giving land and water managers better testing tools to track PFAS is something his lab had been working on for a long time. Testing for PFAS is currently done with a mass spectrometer, a sophisticated piece of lab equipment. This yields high-quality data, but it’s very expensive and time-consuming, Berger said — running around $400 per sample, with a one- to two-week turnaround time. “There’s just a huge shortage of infrastructure to do testing at the scale necessary,” he said. Land stewards need a simple test akin to a pH strip that can measure PFAS — and Berger and his team developed something close: a biosensor, in the form of a fluorescent microbe that glows when it’s exposed to PFAS.

Through the collaboration with the Mi’kmaq Nation, Berger and his collaborators tested the biosensors on water samples taken near the tribe’s land at the former Air Force base — and in a report published in October, they found that the sensors could effectively detect the high levels of the chemicals, even in samples that contained other contaminants.

“So we have a direct testing method that could be used, that’s kind of a cheap, fast point of detection,” Berger said. It won’t replace the more sophisticated lab testing, but offers an option for farmers who want to test, say, across hundreds of acres.

To build on this work, Berger hopes to develop a way to embed the same technology within a plant — which he calls “a new twist on an old idea.” The old idea refers to the concept of sentinel plants: traditionally, a plant susceptible to certain diseases or pests that farmers would monitor to see when those pests were present, and then tailor control measures accordingly. “What if we then go a step further and engineer the plant to indicate a signal to tell you that there’s PFAS present — you know, maybe you apply a pesticide and then it turns on,” Berger said. As with the microbes his team tested, that signal could be fluorescence — meaning the plants would literally glow when PFAS are present. A warning sign like this would mean farmers wouldn’t need to take an extra step of regular testing, even with simple microbe kits; they could just look at the sentinel plant to see when PFAS show up. “Then you’re getting real time data,” Berger said.

Another thing he and the team in Maine have been working on is understanding whether food grown in PFAS-contaminated soil or fed by PFAS-contaminated water is then contaminated as well, and therefore unsafe to eat. The obvious answer would seem to be yes — but it depends on how the substances travel, where they accumulate, and whether certain plants could be resistant to taking them up.

“If there are cultivars that are PFAS resistant, that could be another tool in the arsenal for growers,” Berger said. Similarly, if farmers understood that PFAS were only gathering in a part of the plant that was nonedible, they may still be able to safely grow certain crops while simultaneously working on remediation. Just recently, the team had a breakthrough finding on that front.

“We did a study where we looked at accumulation of PFAS in potatoes, which are kind of an important part of Maine’s agricultural heritage,” Berger said. “They’re very proud of their Maine potatoes.” That study, published by the Central Aroostook Soil and Water Conservation District in Maine, one of the grant partners, found that PFAS did not accumulate in the edible root of the potato — the chemicals were only stored in the green leafy portions.

“So you could grow potatoes even if there was PFAS present in the irrigation water, which is what they found,” Berger said. The team plans to continue testing other common crops like broccoli, brussels sprouts, and kale, as well as culturally significant plants for the Mi’kmaq Nation, like fiddleheads and ash trees.

While these are heartening findings from just the first few months of the grant, one of the biggest questions that remains for anybody working on PFAS is what, if anything, can be done to actually get rid of the chemicals. According to Berger and his collaborators, there is currently no scalable, cost-effective way to destroy PFAS. “It’s the million-dollar question,” Berger said.

But his lab has been testing one possible approach, essentially mimicking photosynthesis in a specially engineered microbe and using the energy from that process to break down PFAS that the microbe had absorbed. “So, kind of making plants or other microorganisms divert some of that energy or electrons into PFAS destruction,” Berger said. The initial, early-stage trials have shown promise, though there is still more research to be done before the approach could be attempted in a real-life application. “It’s not a perfect solution ready to go or anything, but those are promising things we’re doing that are different from what is currently out there,” Burger said. Actually breaking down PFAS within a contaminated plant or microbe would mean that the substances wouldn’t spread further — unlike other disposal methods, like incineration, which can release the chemicals into the air.

“If it works, it’s the most environmentally benign way we could do things because it’s almost all biological,” Berger said.

— Claire Elise Thompson

More exposure

A parting shot

In this photo from 2019, dairy farmer Fred Stone held a small press conference on his land in Arundel, Maine, calling on public officials to take action to avoid future PFAS contamination on farms. He shuttered his farm after discovering the levels of PFAS in his cows’ milk, and became a leading advocate for action. Many farms in the state, like Stone’s, were exposed to the chemicals through the application of sludge, or biosolids — a treated wastewater product that was long used as a fertilizer.

IMAGE CREDITS

Vision: Mia Torres / Grist

Parting shot: Gregory Rec/Portland Portland Press Herald via Getty Images