Published in Nature, a study reveals that everyday plastics spontaneously generate damaging reactive oxygen species simply by contacting water. The research overturns decades of assumptions about chemical inertness, showing that hydrophobic polymers like polypropylene and polyethylene trigger surface electrical charges that strip electrons from water molecules.
How Plastics Turn Chemically Reactive in Water
For decades, the case for plastic safety relied on a simple premise: the material is chemically inert. That presumed stability is why polymers wrap food, bottle water, and line children’s toy boxes without raising alarms. A joint team from Columbia University and the University of California, Berkeley, upended that assumption by demonstrating that standard plastics become chemically active the moment they touch water.
When large plastic items break down into microplastics and nanoplastics, their surface area expands relative to their volume. That enormous new surface area interacts directly with surrounding moisture. Wei Min, a professor of chemistry and biomedical engineering at Columbia University, led the research team alongside Teresa Head-Gordon at UC Berkeley. Biological stakes were underscored by Naixin Qian, a postdoctoral researcher who worked in Min’s group and helped direct the project.
The biggest surprise was that plastics, long considered chemically inert, could generate highly reactive radicals simply by coming into contact with water, without external triggers such as UV light.
Wei Min, professor of chemistry and biomedical engineering at Columbia University
The Hydrophobic Mechanism Behind Hydroxyl Radicals
The chemical activity stems from the molecular structure of the plastics themselves. Plastic surfaces are hydrophobic, meaning they repel water and prevent water molecules from forming the hydrogen bonds they maintain in a liquid state. This disruption alters local electrical environments and triggers spontaneous electron transfers.
According to molecular dynamics simulations and theoretical calculations, hydroxide ions near the water-repelling plastic surfaces lose electrons easily, which gives rise to volatile hydroxyl free radicals. These reactive oxygen species are capable of damaging lipids, proteins, and DNA.
Laboratory tests confirmed clear variations across polymer types. The most water-repelling materials — such as polyethylene and polypropylene — showed much stronger radical-generating activity than more hydrophilic polymers like polyethylene terephthalate. While pointing out that this particular mechanism for generating reactive oxygen species might help account for health effects observed previously, the investigators cautioned that these findings on their own are insufficient to prove microplastics directly bring about specific illnesses.
Cellular Impacts Observed in Laboratory Tests
To test biological effects, researchers introduced polystyrene particles to red blood cells from mice. Under microscope observation, red blood cells broke apart after making physical contact with the plastic surfaces. Similar tests showed that the surface electric charge attracted biological molecules like DNA, damaging both proteins and cells.
Such interactions carry profound consequences given that human blood is roughly 50 percent water and individual human cells are generally 60 to 80 percent water. Microplastics found inside the human body enter through ingestion, inhalation, and absorption, lodging themselves in fluid-rich environments where this newly identified chemistry can flourish.
Connections between exposure to micro- and nanoplastics and conditions including heart attack, stroke, dementia, brain tumors, cellular inflammation, and oxidative stress have been documented in past research featured in journals such as the New England Journal of Medicine, Nature Medicine, and Nature Health. While prior studies established associations between plastic pollution and biological harm, the new findings help explain the specific mechanism of how those reactive oxygen species form. Hao Chen at the New Jersey Institute of Technology describes the results as very important, noting that while they do not directly answer how dangerous microplastics might be, they provide a starting point to help understand the interaction between microplastics and cells. Matthew Campen of the University of New Mexico views the findings as an essential foundational piece for grasping this dynamic.
Experts Urge Caution Regarding Experimental Findings
Independent toxicologists note that while the study offers a critical building block for understanding cellular interactions, the work remains experimental. Wagner says the study’s findings are exciting and gives scientists a new way to look at the effects of plastic pollution.
Appearing on 14 October 2026 in Nature as an experimental investigation entitled Intrinsic physicochemical activity at microplastic-water interfaces, the work was published with no reported competing interests from the authors.
Readers concluding practical next steps from the evidence should consult qualified professionals regarding chemical exposures and health concerns. Individuals looking to limit daily exposure can utilize glass or stainless steel water bottles and avoid heating food in plastic containers.
