A study published in Nature and reported by Ars Technica found that microplastics are not chemically inert in water. Columbia University chemist Wei Min and his team showed that polystyrene powder in water generated hydroxyl radicals—a type of reactive oxygen species that can damage DNA, proteins, and lipids. The effect appeared with five other plastics as well, including polyethylene, polypropylene, PVC, PET, and acrylic. Water-repellent plastics like polyethylene and polypropylene produced the most radicals.
The researchers used multiple detection methods and controls to rule out contamination, though Min acknowledged that impurities cannot be completely excluded. In lab tests, the radicals caused the protein lysozyme to clump and fragmented mouse red blood cells. Adding caffeine, which neutralizes radicals, largely stopped the damage. The team also found that a surfactant coating on the plastic reduced both electric charge and radical production, supporting the idea that the water-plastic interface is responsible.
While the study does not address commercial implications, the findings could matter for businesses that rely on plastic packaging, water filtration, or biomedical devices. If microplastics in drinking water can generate reactive chemicals, companies may face new questions about product safety and liability. However, Min stressed that whether microplastics directly cause human disease is still being researched, and the magnitude of this effect relative to normal cellular processes remains unclear.