PFAS — the "forever chemicals" that linger in water, soil, and human bodies for decades — may not be as invincible as their nickname suggests. A new study from Aarhus University in Denmark has identified a hidden weakness that could lead to cleaner, simpler ways to destroy them.
The research, published in Environmental Science & Technology, pinpoints hydrogen radicals as the dominant force behind PFAS breakdown under intense ultraviolet light. The discovery rewrites the textbook on how these notoriously stable compounds can be eliminated.
A Stubborn Problem Meets a Surprising Solution
Per- and polyfluoroalkyl substances (PFAS) earned their "forever" reputation because of the exceptionally strong carbon-fluorine bonds that hold them together. Used for decades in non-stick coatings, firefighting foams, waterproof fabrics, and food packaging, they have now been detected in drinking water, wildlife, and human blood around the world.
Destroying them has been a serious chemical challenge. Most existing approaches require harsh treatments, added catalysts, or extreme conditions — all of which add cost and complexity.
The new study shows that PFAS can be broken down using intense UV light alone, with no additional chemicals. More importantly, the team identified exactly what is doing the heavy lifting.
Hydrogen Radicals Take Center Stage
When high-energy UV light hits water, it can generate hydrogen radicals — tiny, highly reactive particles. The Aarhus researchers found that these radicals attack PFAS molecules and gradually strip away their fluorine atoms, splitting them into smaller, less persistent substances.
"We know that PFAS are extremely stable because of the strong carbon-fluorine bonds, and breaking those bonds is the main challenge," said Associate Professor Zongsu Wei, who led the study. "By identifying hydrogen radicals as a dominant driver, we now have a clearer direction for how to design more efficient and sustainable technologies to actually destroy these chemicals."
Previous research had largely focused on other reactive species as the primary drivers of degradation. The new finding shifts that picture and offers a concrete chemical target to optimize.
Why It Matters
In lab tests, certain PFAS compounds — including GenX, a notorious replacement for older PFAS — showed up to 49 percent degradation and 21 percent defluorination within just five hours of exposure to simulated solar light. The reaction worked best at wavelengths below 300 nanometers, in the deeper ultraviolet range.
That opens the door to treatment systems that rely on light alone, without expensive catalysts or chemical additives. Cleaner inputs mean simpler operation, lower running costs, and fewer waste streams.
What Comes Next
The Aarhus team sees the finding as a roadmap, not a finished product. Engineers can now design UV reactors, water treatment systems, and industrial processes specifically tuned to maximize hydrogen radical production.
Pilot-scale trials and combinations with other treatment methods are the natural next steps. For utilities, manufacturers, and communities living near PFAS-contaminated sites, the result offers something that has been in short supply: a clear, mechanism-based path toward making forever chemicals a lot less forever.
