Min, however, pointed out that this indicates that microplastics are making people sick by generating ROS. While animal studies often indicate that ROS are the cause of oxidative stress and chronic inflammation, ROS can be produced in numerous ways, including through basal metabolic activity.
Min admitted that it was rather tricky to compare the magnitude of this effect to the impact of ROS produced by our own cells.
A local problem
“If you’re really at the interface, you might be significantly affected by this effect, whereas if you’re only a few microns away, you don’t feel it anymore,” Min said. Exposure is another unknown here. Min also pointed out that no one can yet say how many microplastics the average person absorbs each year through food, water and air.
The plastics studied were mostly fresh powders purchased in the laboratory, unlike the altered particles we encounter in the environment. In the team’s tests, older particles with more oxidized surfaces produced somewhat weaker signals. “This aging process is very heterogeneous,” Min said. “Some microplastic particles were made 50 years ago, others five days ago.” Finally, there remains the question of size.
Microplastics are generally defined as particles smaller than five millimeters, while the minimum limit varies between 100 and 1,000 nanometers. Min’s team did not test the impact of varying the size of microplastic particles on water interface chemistry, but the researchers suspect it could play a role. The same mass of plastic divided into nanoparticles has a much larger surface area, which could make the effect greater. “This could be another reason why nanoplastics are more dangerous,” Min said.
The researchers argue that if water-repellent surfaces determine the water interface chemistry, plastics could be designed to be less water-repellent, either by changing their molecular structure or by including additives. But first, the team wants to focus on the question left open by their study. “We really want to see how much this effect directly contributes to diseases or biological problems in animals and humans,” Min said.
Nature, 2026. DOI: 10.1038/s41586-026-11141-y
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