Columbia and UC Berkeley researchers found that microplastic surfaces in contact with water produce reactive oxygen species, offering a possible mechanism for links between plastic particles and disease.
Microplastics are everywhere: in oceans, soil, food, drinking water and the human body. Researchers have found them in blood, lungs, placentas and brains. Yet a basic question has lingered over this growing body of evidence. Plastics are often described as chemically inert, so how might tiny fragments of them cause harm?
A study published in Nature offers an answer. Researchers at Columbia University and the University of California, Berkeley, report that when microplastics touch water, their surfaces generate reactive oxygen species, highly reactive molecules that can damage living tissue. The team also identified the chemical mechanism behind the effect.
Microplastics, said Wei Min, a professor of chemistry and biomedical engineering at Columbia, change the water that surrounds them, “generating high-energy, reactive radicals.” He added: “Water is a key active player here, rather than just a spectator.”
Small particles, big surfaces
The finding hinges on surface area. As plastics break down into micro- and nanoparticles, their surface area grows enormously relative to their volume. A material that seems unreactive as a bottle or a bag can behave very differently when divided into countless tiny fragments, each exposing new surface to its surroundings.
Reactive oxygen species, or ROS, include molecules such as hydroxyl radicals and hydrogen peroxide. Cells produce small amounts of them during normal metabolism and use them as signals, but in excess they damage proteins, fats and DNA, a condition known as oxidative stress that is associated with inflammation, aging and many diseases.
The body has defenses against ROS, including antioxidant enzymes and molecules such as glutathione and vitamins C and E. Problems arise when production outpaces those defenses. A steady source of radicals from particles lodged in tissues could, in principle, tip that balance locally, although the study does not measure that directly.
“ROS are textbook examples of the kinds of molecules that can damage animal and human tissue,” said Naixin Qian, a postdoctoral researcher in Min’s lab.
How plastic makes radicals
The Berkeley group led by Teresa Head-Gordon provided the theoretical explanation. Plastics are hydrophobic, meaning they repel water. Calculations showed that near such a water-repellent surface, hydroxide ions, negatively charged fragments of water molecules, can more easily give up an electron. When they do, they become hydroxyl radicals, among the most reactive of all ROS.
Head-Gordon said the results show that “the most hydrophobic microplastics interacting with water can drive chemical reactivity.”
The interface between water and a water-repellent surface has become a topic of intense interest in chemistry. In recent years, researchers have reported that tiny water droplets and water at certain interfaces can drive reactions that do not occur in bulk water, though some of those findings have been debated. The new work extends that idea to the surfaces of plastic particles.
Active inside the body
The implications reach into human health. Because blood is mostly water, microplastics that enter the bloodstream or cells may remain chemically active, potentially generating ROS wherever they lodge.
That could help explain findings from other studies. Research published in major journals has linked exposure to micro- and nanoplastics with heart attack, stroke, dementia and brain tumors. One widely reported study found that patients whose arterial plaques contained microplastics had a higher risk of heart attack, stroke or death. Such studies show associations, not causes, and the new work offers a possible mechanism rather than proof that microplastics cause disease.
Beizhan Yan of Columbia’s Lamont-Doherty Earth Observatory, a co-author, said the work also indicates that radicals can form on hydrophobic plastic surfaces in water. He noted that microplastics can form in manufacturing discharges and laundromats, and that microwave heating and sunlight exposure during the storage of bottled water can also generate them.
A growing concern
Members of the Columbia team previously reported, in a 2024 study, about 240,000 detectable plastic fragments per liter of bottled water, mostly nanoplastics. That was 10 to 100 times more than earlier estimates.
Policymakers are paying increasing attention. A U.S. federal program launched in 2026 is directing $144 million toward combating toxic microplastics in the human body, and the Environmental Protection Agency recently added microplastics to a federal list of possible drinking water contaminants for the first time.
The new study leaves important questions open. Laboratory measurements of ROS at plastic surfaces do not reveal how much is generated inside the body, where particles may become coated with proteins and other molecules that could change their behavior. Different plastics, particle sizes and shapes may also produce different amounts of reactive species.
Plastic particles also carry other potential hazards. Many contain chemical additives, such as plasticizers and flame retardants, that can leach out, and their surfaces can collect pollutants and microbes from the environment. Separating the effects of the plastic itself from those of the substances it carries is one of the major challenges in microplastics research.
The work was funded by the National Institutes of Health, and the authors declare no competing interests. Its central message challenges a common assumption: the plastic fragments accumulating in the environment and the body may not be passive debris but tiny chemical reactors.
Notes
- “Intrinsic physicochemical activity at microplastic–water interfaces.” Nature, 14 October 2026.
- Columbia University. “Microplastics are chemically active, and could cause biological harm.” EurekAlert!, 14 October 2026. https://www.eurekalert.org/news-releases/1147261.
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