Forever chemicals may not stay ‘forever’ for long. New research is reporting on how the most common two of these extremely resilient materials, which are increasingly contaminating natural environments and the tissues of living animals, can be cheaply and easily broken down.
This group of chemicals is known industrially as PFAS, but is colloquially called “forever chemicals” due to their unique properties. First developed in the 1940s, perfluoroalkyl and polyfluoroalkyl substances (PFAS) have come to enjoy wide-scale use in consumer products as they are not biodegradable, they are water resistant, fire resistant, and quite non-stick; the coating commonly applied to pots and pans today known as Teflon is an example of a brand-name PFAS.
The issue with these chemicals is that their resilience makes them prone to building up gradually in the environment — from which they find their way into the tissues of living plants and animals. This makes them a persistent problem, as they are not naturally degraded in the environment. There is also a growing body of evidence to suggest that they can lead to very unpleasant health outcomes.
Researchers at Northwestern University now point the way towards a solution for this issue, as they have developed a simple and inexpensive procedure that can dismantle two of the most used classes of PFAS compounds into harmless chemicals.
Breaking the unbreakable
“PFAS has become a major societal problem,” said William Dichtel, the Robert L. Letsinger Professor of Chemistry at Northwestern, lead author of the study. “Even just a tiny, tiny amount of PFAS causes negative health effects, and it does not break down. We can’t just wait out this problem. We wanted to use chemistry to address this problem and create a solution that the world can use. It’s exciting because of how simple—yet unrecognized—our solution is.”
The technique that the team developed could finally give us a reliable solution for the disposal of these chemicals that have dangerous effects on natural environments, livestock, and human health. The paper is part of Dichtel’s completed doctoral thesis
PFAS have seen extensive use as nonstick or waterproofing coatings since their development. Apart from cookware, they are also used in waterproof cosmetics, firefighting foams, water-repellent fabrics, and grease- and oil-resistant surfaces.
Due to how commonly used they are, goods that include PFAS often end up in the landfill, from which they leach out into soils and groundwater. From there, they make their way into crops, livestock, and, eventually, our own blood to a staggering extent — it’s estimated that around 97% of people in the U.S. have measurable levels of PFAS in their bloodstream.
The impacts of these compounds on health are not fully understood, but what we do know about them isn’t good. PFAS exposure has been strongly linked with decreased fertility, developmental issues in children, as a promoter of various types of cancer, reduced immunity levels and increased cholesterol levels. As such, several PFASs have recently been declared unsafe for use even in trace amounts by the U.S. Environmental Protection Agency (EPA).
“Recently, the EPA revised its recommendations for PFOA essentially down to zero,” Dichtel said. “That puts several PFAS into the same category as lead.”
Although we have tools at our disposal that can filter PFASs out of water, we don’t have any efficient way to deal with them after the fact. The options we do have require great pressures and high temperatures (up to 400 degrees Celsius) and are thus prohibitively expensive for wide-scale use. They are also not fail-proof, as the team explains:
“In New York state, a plant claiming to incinerate PFAS was found to be releasing some of these compounds into the air,” Dichtel said. “The compounds were emitted from the smokestacks and into the local community.”
“Another failed strategy has been to bury the compounds in landfills. When you do that, you are basically just guaranteeing that you will have a problem 30 years from now because it’s going to slowly leach out. You didn’t solve the problem. You just kicked the can down the road.”
The strength of PFASs comes from the many carbon-fluorine bonds in their molecules, the strongest bonds in organic chemistry. The team, however, found a way to break them. PFAS molecules form long trails of these carbon-fluorine bonds. But, at the end of the molecules lies a grouping of charged oxygen atoms. When heating the PFAS molecule in dimethyl sulfoxide and sodium hydroxide, it breaks down, leaving behind only the reactive bit at the end.
“That triggered all these reactions, and it started spitting out fluorine atoms from these compounds to form fluoride, which is the safest form of fluorine,” Dichtel said. “Although carbon-fluorine bonds are super strong, that charged head group is the Achilles’ heel.”
Unlike previous methods, the one developed by the team uses much lower temperatures and inexpensive reagents, meaning that it can be scaled up to deal with PFAS contamination.
The team is now hard at work to test how effective their approach would be against several other types of PFAS. Right now, they have successfully degraded 10 perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl ether carboxylic acids (PFECAs). These include perfluorooctanoic acid (PFOA) and one of its common replacements, known as GenX, two of the most widely-used PFAS compounds today. Still, that leaves 11,990 other PFAS to be tested.
“Our work addressed one of the largest classes of PFAS, including many we are most concerned about,” he said. “There are other classes that don’t have the same Achilles’ heel, but each one will have its own weakness. If we can identify it, then we know how to activate it to destroy it.”
The study, “Low-temperature mineralization of perfluorocarboxylic acids,” has been published in the journal Science.