Few environmental challenges are as persistent as per- and polyfluoroalkyl substances (PFAS). These are the so‑called “forever chemicals” and they have earned their name through sheer chemical stubbornness. Built around ultra-strong carbon–fluorine bonds, PFAS compounds resist degradation, accumulating in water, soils, wildlife and, increasingly, human tissues. The result is a long-term contamination problem that has outpaced our ability to deal with it effectively.
PFAS contain extremely strong carbon-fluorine bonds that do not naturally degrade. Because of this, they accumulate in the environment, wildlife, and the human body over time.
A new study provides a significant piece of the puzzle. Researchers have shown that intense ultraviolet (UV) light can trigger a reaction in water that generates hydrogen radicals, which are highly reactive species capable of breaking down PFAS molecules without the need for additional chemicals. The finding does not eliminate the PFAS problem overnight, but it offers something arguably just as valuable: a clearer understanding of how these chemicals can be destroyed.
Breaking the unbreakable
The difficulty with PFAS lies in chemistry. Carbon–fluorine bonds are among the strongest in organic chemistry, making them exceptionally resistant to both biological degradation and conventional treatment processes. Most current approaches therefore focus on removal rather than destruction—filtering PFAS out of water using activated carbon or membranes, only to face the problem of disposal later.
The new research shifts attention toward degradation. When water is exposed to high-energy UV light—particularly at wavelengths below 300 nanometres—it can produce hydrogen radicals. These radicals are highly reactive and, crucially, capable of attacking PFAS molecules at their weakest points. Over time, they strip away fluorine atoms, fragmenting the molecule into smaller, less persistent compounds.
Earlier work tended to emphasise other reactive species, such as hydrated electrons or hydroxyl radicals, as the main drivers of PFAS breakdown. Yet by identifying hydrogen radicals as a dominant player, the new study reshapes how chemists and engineers approach treatment system design.
From removal to destruction
The distinction between removing and destroying PFAS is more than semantic. As Associate Professor Zongsu Wei, who led the study, has emphasised, filtration alone does not solve the problem—it merely transfers contaminants from one phase to another. What remains needed is a sustainable, scalable way to dismantle PFAS molecules entirely.
The challenge is that even with UV-generated radicals, degradation can be slow. Intermediate compounds may form as PFAS structures are dismantled piece by piece, and not all breakdown pathways are fully understood. Yet knowing which reactive species are doing the work provides a clear direction for optimisation. It suggests that future systems might be engineered to maximise hydrogen radical production while minimising energy input.
In practical terms, this could mean new classes of photochemical reactors designed specifically for PFAS destruction—systems that use tailored UV wavelengths, optimised reactor geometry and controlled water chemistry to accelerate radical formation. The ultimate goal would be to move from laboratory-scale demonstrations to continuous, industrial-scale processes.
Canadian parallels: radical chemistry meets environmental engineering
The emerging focus on targeted reaction mechanisms has strong parallels with Canadian research into water treatment and environmental chemistry. Canadian universities and research institutes have been active in developing advanced oxidation and reduction processes, many of which rely on reactive radicals to degrade persistent contaminants.
For example, research groups across Canada have explored the use of UV photolysis, electrochemical systems and plasma-based methods to generate reactive species capable of breaking down recalcitrant pollutants. These approaches are conceptually aligned with the new findings: rather than relying on bulk removal, they aim to engineer the right reactive environment to dismantle pollutants at the molecular level.
There are also intersections with Canadian work in granular and soft-matter systems, particularly in how materials respond to external energy inputs such as vibration or light. At McGill University, studies into reconfigurable metamaterials highlight how structure and energy input can interact to create controllable transformations in matter. While the physics differs from PFAS chemistry, the underlying principle is similar: understanding a system’s internal mechanisms allows engineers to switch between states—in one case, mechanical; in the other, chemical.
Meanwhile, Canadian research into granular jamming and fluidisation has demonstrated how materials can transition between solid-like and fluid-like states under controlled conditions. In a chemical context, UV activation plays an analogous role, converting relatively inert water into a reactive medium capable of transforming otherwise stable compounds. In both cases, the system’s behaviour hinges on how energy is introduced and managed.
Despite the promise, the UV–hydrogen radical pathway is not without its challenges. High-energy UV light is energy-intensive to produce, raising questions about cost and sustainability. Reactor design must also ensure that light penetrates effectively and that radicals have sufficient opportunity to interact with PFAS molecules before they recombine or dissipate.
There is also the matter of scale. PFAS contamination is not confined to laboratory volumes—it exists in groundwater systems, industrial effluents and municipal supplies. Any viable technology will need to operate reliably at large scale, often in complex, mixed-chemical environments.
Yet the history of environmental engineering suggests that such challenges are not insurmountable. Many now-standard treatment methods, from ozone disinfection to membrane filtration, began as niche, energy-intensive processes before becoming optimised and widely adopted.
The real significance of the new findings lies not in delivering an immediate solution, but in refining the roadmap. PFAS have long been described as practically indestructible, a characterisation that has sometimes obscured the fact that they are not immune to chemistry—they are simply difficult targets. By identifying hydrogen radicals as a key agent of degradation, researchers have narrowed the search for effective intervention strategies.
In that sense, the study represents a shift from empirical trial-and-error towards mechanism-driven design. Rather than asking what might work, scientists can now ask what must be optimised.