PFAS, often called “forever chemicals”, are notoriously difficult to remove from the environment. Their extreme chemical stability means they can persist in water and the human body for decades, creating a major global pollution challenge.

Now, researchers have made an important discovery that could change how we tackle the problem.

In a new study, scientists found that PFAS can be broken down using intense light, without adding chemicals. But the real breakthrough is how this happens. The study shows that hydrogen radicals - highly reactive species formed from water under UV light - play a central role in the process.

This is significant because it challenges previous assumptions. Earlier research mainly pointed to other reactive species as the key drivers of PFAS degradation. By identifying hydrogen radicals as the main actors, the study provides a clearer understanding of the underlying mechanism.

Why does that matter? Because knowing what actually drives the reaction makes it much easier to design better treatment technologies.

Hydrogen radicals are extremely reactive and can attack PFAS molecules, gradually stripping away fluorine atoms and breaking the molecules into smaller, less persistent compounds. The study also shows that this process is most effective under high-energy UV light, particularly at wavelengths below 300 nanometers.

According to Associate Professor Zongsu Wei from Aarhus University, who led the research, this insight is a key step forward:

“We know that PFAS are extremely stable because of the strong carbon-fluorine bonds, and breaking those bonds is the main challenge. 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, rather than just removing them,” he says.

Wei emphasizes that most current solutions only move PFAS from one place to another:

"Today, many technologies can filter PFAS out of water, but they don’t eliminate them. The real goal is degradation: to break the molecules down completely. Understanding the mechanism is essential if we want to achieve that in a green and scalable way.” 

The findings do not solve the PFAS problem overnight. The process is still relatively slow, and some intermediate compounds may form along the way. But by identifying the true driver of the reaction, the research provides a crucial piece of the puzzle.

In short, the study shows that even the most persistent pollutants may be vulnerable, if we understand the chemistry well enough to target them effectively.

WHAT ARE PFAS?

• PFAS (per- and polyfluoroalkyl substances) are a large group of man-made chemicals used since the 1940s
• Found in everyday products such as waterproof clothing, food packaging, firefighting foam, and non-stick cookware
• Known as “forever chemicals” because they are extremely difficult to break down in nature
• They accumulate in water, soil, animals, and humans
• Linked to health risks such as cancer, liver damage, and hormone disruption
• Most current water treatment methods remove PFAS but do not destroy them

Contact

Associate Professor Zongsu Wei
Department of Biological and Chemical Engineering
Mail: zwei@bce.au.dk
Tel.: +4593522047