Scientists have found that hydrogen radicals generated by intense ultraviolet light can break down PFAS "forever chemicals," a surprising mechanism that could lead to cleaner, cheaper ways to destroy one of the most persistent pollutants on Earth. The work, published this week in the journal Environmental Science & Technology, rewrites part of the textbook on how these stubborn compounds come apart.
Cracking a molecule built to last
Per- and polyfluoroalkyl substances, or PFAS, earned their nickname because the carbon-fluorine bonds that hold them together are among the strongest in organic chemistry. That durability makes them useful in nonstick coatings, firefighting foam and waterproof fabrics — and nearly impossible to get rid of once they leach into soil and groundwater. They accumulate in the environment, in wildlife and in human blood, where they have been linked to cancers, immune effects and developmental harm.
The new research found that highly reactive hydrogen radicals, produced when high-energy UV light hits water at wavelengths below 300 nanometers, attack PFAS molecules and gradually strip away their fluorine atoms. As the fluorine peels off, the molecules break into smaller, far less persistent fragments. Crucially, the process requires no added chemicals — only light and water — which sets it apart from many existing treatment schemes that depend on expensive catalysts or harsh reagents.
Overturning an assumption
The finding challenges a long-held belief about how PFAS degradation happens. Earlier studies had largely credited other reactive species with doing the heavy lifting; by pinpointing hydrogen radicals as a dominant driver, the team behind the study, led by researchers at Aarhus University in Denmark, gives chemists a clearer target to engineer around. "Once you know which species is actually doing the work, you can design a system to maximize it," one of the researchers noted in materials accompanying the paper.
That clarity matters because the gap between a laboratory result and a working treatment plant is wide. The reaction performs best under intense UV that is energy-hungry to produce, and scaling it to the volumes handled by a municipal utility will demand engineering that does not yet exist. The authors are careful to frame the work as a mechanistic advance — a map of the chemistry — rather than a finished technology.
Still, a sharper map changes what engineers can build. If hydrogen radicals are the workhorse, designers can chase reactor geometries, light sources and water chemistries that produce more of them per unit of energy, potentially shrinking the power bill that has kept UV-based destruction on the lab bench. Some researchers are already exploring whether the same radicals can be coaxed from cheaper light sources, or paired with existing carbon filters that first concentrate the chemicals and then feed them into a destruction step.
Why it matters in the U.S.
The stakes are especially high in the United States, where PFAS contamination has touched drinking water from coast to coast. Michigan became a national flashpoint after high levels turned up in communities near Grand Rapids, prompting one of the most aggressive state cleanup efforts in the country. The Environmental Protection Agency has since set the first nationwide limits on several PFAS compounds in drinking water, putting utilities under pressure to find affordable ways to remove them.
Current options — granular activated carbon, ion exchange, reverse osmosis — can capture PFAS, but they mostly concentrate the chemicals rather than destroy them, leaving a toxic residue that must be incinerated or buried. A method that genuinely breaks the molecules apart, using little more than light, could change that calculus. For now, the discovery is a promising lead rather than a deployed fix, but it offers a rare piece of good news in a contamination story that has felt, until now, all but permanent.