These toxic chemicals are everywhere. How can we get rid of them?

You may not have heard of “per- and polyfluoroalkyl substances”, but you have been exposed to them every day. Thanks to their unique properties to repel water and oil and resist heat, PFAS, as these chemicals are commonly known, are used in everything from food packaging to raincoats, nonstick frying pans, cosmetics, menstrual products, and firefighting foam. But the same properties that make PFAS so useful also make them nearly indestructible.

“The problem is that PFAS don’t degrade. They accumulate – in the air, soil, water, and ultimately in us,” says Alraune Zech, Assistant Professor of Earth Science at Utrecht University. “And that’s worrying because we know they can be toxic even at low concentrations.” 

PFAS have been found in drinking water and food, in human blood and even in the ice of Antarctica.

Research suggests that exposure to PFAS can increase the risk of certain cancers, damage the liver, or weaken the immune system. But with thousands of different PFAS compounds in use, scientists are still learning about the full extent of their impact on human and environmental health. As Zech’s colleague and associate scientist, Johan van Leeuwen, notes: “While PFOA and PFOS, two of the most studied PFAS compounds, were banned in 2015, new PFAS such as GenX have been produced and used since then, and we don’t yet know the long-term effects of continued exposure.”

Having been used for over 50 years, PFAS are now everywhere. “They have been found in drinking water and food, in human blood and even in the ice of Antarctica,” van Leeuwen says. “The longer they are produced and released to the environment, the bigger the problem becomes.”

Despite ongoing efforts, he says, there are no efficient and sustainable methods to eliminate PFAS from the environment.

Zech and Van Leeuwen are part of an interdisciplinary research collaboration at Utrecht University known as the PFAS Remediation Living Lab, which aims to find sustainable ways to remove these chemicals from the environment. Their unique advantage? They can experiment with contaminated soil and test different remediation methods right at the Utrecht Science Park.

A ”Living Lab” for studying PFAS contamination

The field they’re working on, a small meadow once used for fire training by the university’s Emergency Response Team, was found to be contaminated with PFAS from firefighting foam in levels that posed a risk to humans and animals.

Simply digging up the soil and dumping it in a landfill wouldn’t have solved the problem.

“Simply digging up the soil and dumping it in a landfill – as it’s traditionally done- wouldn’t have solved the problem,” explains Frank Kooiman from Utrecht University’s Campus & Facilities. “PFAS don’t disappear in landfills—they leach out and re-enter the environment through sludge or treated water.”

Similarly, if PFAS-contaminated soil is burned, toxic pollutants are released into the air, which settle back into the soil. “None of these methods is sustainable. We might have cleaned up this 3000 square-metre field in Utrecht, yet shift the problem elsewhere,” he says.

The university saw this PFAS-contaminated field as an opportunity. “We heard from the city of Utrecht about alternative methods using plants to clean up toxins from soil,” Kooiman says. “Couldn’t that work for PFAS too?” This idea led to the creation of the PFAS Remediation Living Lab.

Tracking the PFAS journey

The first step is understanding how PFAS travel through the environment, says environmental hydrologist Stefanie Lutz, who is studying how water moves through the contaminated field to track the journey of these chemicals. “We want to know whether PFAS are seeping deeper into the soil and reaching groundwater, or if they’re sticking closer to the surface,” Lutz explains.

Knowing how PFAS behave will shape how the team approaches remediation on the site. “If we find that most PFAS are indeed staying close to the surface, “waiting” for the next rain to flush them out, that would be a very good indication that capturing PFAS at the drain pipes could be an effective way of cleanup,” says Lutz.

To test this theory, Lutz and her colleagues are measuring the levels of concentration of PFAS. “Until now we have just put bottles under the drain and collected water samples. But we’re now considering a more sophisticated approach by installing a natural material in the water pipes. The sorbent is a clay-like mineral that PFAS are attracted to. We can use it in the field and take it to the lab to measure how much PFAS are collected,” she explains.

Any PFAS we capture with these sorbents will be removed from the water before they spread further into the environment.

“After analysing the water samples, it could be that only very small amounts of PFAS are coming through the drain pipes after all. If that’s the case, stopping the flow there may not be the way to go further with remediation,” says Lutz. “At the same time, any PFAS that we manage to capture with these sorbents for sampling purposes will be removed from the water before they spread further into the environment. So we’ll already be helping to clean up the field of PFAS, even as we’re learning what works best.”

It's a feedback loop that also helps accelerating solutions. “Once we understand how PFAS move through the water cycle, we could actively push that water flow in the direction we want it to go, to concentrate as many PFAS as possible in one place, to apply remediation methods there,” Lutz foresees.

Can soap wash away PFAS?

In a bid to flush PFAS more efficiently, Van Leeuwen and Zech’s lab tried on an unconventional solution: soap. More specifically, a natural, biodegradable soap that could help flush PFAS out of the soil faster than plain rainwater alone. “PFAS compounds cling to surfaces, behaving more like viruses than conventional organic contaminants,” explains Van Leeuwen. “Just like how soap helps wash away viruses, we thought it might work for PFAS too—and it did.”

Their initial lab results show that adding bio-based soap to water can effectively wash PFAS out of the soil with minimal water and energy use. “The next step is to test the soap solution for different soil settings and to see for which types of PFAS this method is most effective. Eventually we want to apply it to the contaminated field to speed up the process of flushing out PFAS,” Zech adds.

Harnessing nature’s microbial power

Meanwhile, George Kowalchuk, head of the Ecology and Biodiversity research group at Utrecht University, is investigating a different approach: whether microorganisms in the soil might be able to decontaminate or break down PFAS. “Microbes in the soil are incredibly good at breaking down pollutants such as pesticides and petroleum products. Even chemicals they have never encountered before,” he says. “We think there’s potential to find microorganisms that can degrade PFAS too.”

But the living world beneath our feet is vast and complex: one gram of soil alone can contain up to 10 billion microorganisms from thousands of different species. How do you identify the ones that might help break down PFAS? “We really want to understand how PFAS affect the ecology of the site. Because in most biodegradation processes, it’s not just one organism that does it, but a combination of them,” says Kowalchuk. “So instead of isolating a particular organism to see what kind of tricks it can do, we will observe how PFAS affect the composition, functioning and evolution of the soil community.”

Can certain microbes tolerate PFAS and can they work together to degrade them?

Kowalchuk’s team will use, among other things, the university’s state-of-the-art Ecotron module of the Netherlands Plant-Ecophenotyping Centre (NPEC) to study how PFAS affect the microbial community in the soil. “With the Ecotron, we can recreate the conditions in the field, including soil pH, temperature and humidity, and even the plants and microorganisms present. We can then inject a cocktail of PFAS, leave it for several weeks and see what’s happened,” he explains. “Can certain microbes tolerate PFAS and can they work together to degrade them? Or do they transform PFAS into something else? And what are the by-products?

Kowalchuk’s hope is that by understanding how PFAS impact these ecosystems, they can enhance natural processes to degrade the chemicals, both here and in other contaminated areas. “If we know that adding certain nutrients, for example, promotes microbial activity against PFAS, we can recreate those conditions in the real world and let nature do the work,” he says.

As the researchers from the PFAS Remediation Living Lab continue their work, they remain optimistic that sustainable solutions can be found to tackle one of the most pervasive contamination problems of our time. Through fieldwork investigations, laboratory experiments, numerical modelling and field-scale pilots, the interdisciplinary team is learning more about how different PFAS move through and interact with the environment. The ultimate goal is to find a way to remove PFAS from the environment—not just for this field at Utrecht Science Park, but for contaminated sites around the world.

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