For decades, many have assumed that plastics are chemically inert in most environments, especially when they come into contact with water. A recent study led by Naixin Qian and colleagues, published in Nature, overturns that assumption by demonstrating that common plastics can generate highly reactive hydroxyl radicals (HO•) at the plastic‑water interface.
Mechanism of radical formation
The researchers examined six different types of microplastics, observing that each produced varying levels of free radicals when immersed in water. The most hydrophobic plastics generated the greatest amounts. The energy that drives this reactivity stems from an electrostatic effect that is intrinsic to many polymers. This effect not only supplies the energy needed for radical formation but also tends to attract charged biomolecules toward the plastic surface before any radical damage occurs.
Hydroxyl radicals are the neutral form of the hydroxide ion (OH–). As free radicals, they are extremely short‑lived because of their high reactivity, a property that mirrors the behavior of isolated oxygen molecules released at the interface. In cellular biology, such radicals are well known for their capacity to damage DNA and other critical biomolecules, prompting organisms to evolve sophisticated mechanisms for radical capture and repair.
Observed biological impact
To assess the biological consequences of the newly identified radicals, the team exposed mouse red blood cells to polystyrene (PS) microplastics. The exposure resulted in fatal damage to the cells, indicating that the radicals—and the electrostatic attraction of biomolecules—can have severe effects on cellular integrity.
The authors note that their findings suggest at least three distinct pathways through which micro‑ and nanoplastics (MNPs) could harm living organisms: direct chemical reactivity via radical generation, electrostatic attraction of charged biomolecules, and the consequent cellular damage observed in laboratory tests.
Broader implications and ongoing debate
These results add a new dimension to the ongoing debate about the health risks posed by MNPs. While the prevalence of microplastics in human tissues remains uncertain, reliable detection in biological samples continues to be a major obstacle. The study’s insight into radical generation may help address this blind spot by providing a mechanistic basis for how plastics behave once inside an organism.
Beyond immediate health concerns, the discovery also offers clues about the ageing process of plastics themselves. If water exposure can trigger radical formation, it may influence how plastics degrade over time, potentially altering their environmental impact.
Scientists emphasize that the findings do not yet quantify the risk to humans, but they do underscore the need for further investigation into how widespread MNP exposure translates into measurable health outcomes. As detection methods improve, researchers hope to clarify whether the mechanisms observed in the laboratory are active in real‑world exposures.
In summary, the study challenges the long‑standing view of plastics as chemically inert, revealing that common polymers can produce short‑lived, highly reactive hydroxyl radicals when they encounter water. This mechanistic insight opens new avenues for research into the health effects of microplastics and highlights the importance of developing more sensitive detection techniques for these pervasive particles.
Mitchell Landsberg is a Senior Technology Correspondent at News Raise. He covers consumer electronics, artificial intelligence, software developments, and digital privacy trends.
