How exactly do microplastics damage the body? New research offers an answer
Over the past decade, scientists have found microplastics in nearly every part of the human body — in people’s lungs, bloodstreams and even placentas.
The health consequences of these tiny polymer particles remain murky, but researchers have linked them to a higher chance of heart attacks, strokes and inflammatory bowel syndrome, among other concerns.
Now, scientists think they’ve identified, for the first time, a mechanism that may explain how microplastics raise the risk of some of these ailments. The finding calls into question a long-held assumption about plastics.
In a study published Wednesday in the journal Nature, scientists describe how tiny plastic particles cause chemical reactions with water that generate chemically unstable molecules called free radicals. In the body, these free radicals may cause oxidative stress and inflammation, according to the research.
In essence, the findings suggest that microplastics could be chemically active in water, including in water-rich cells or the bloodstream.
Microplastics are “like a permanent little factory” generating these free radicals, said Wei Min, a professor of chemistry at Columbia University who is an author of the study. “Our cells are 60 to 70% water and therefore this effect could be ubiquitous.”
For their research, Min and his co-authors used several microscope techniques to watch water react to microplastics and saw free radicals develop — the first time the process has been observed in detail, they say. Then, the scientists mixed the microplastics with mouse blood in the laboratory and watched what happened.
“We draw red blood cells from mice, and then we mix red blood cells with microplastics, and then the red blood cells get broken,” Min said. “We do show immediate biological consequences. Proteins get damaged. Cells get damaged.”
Graham Cooks, a professor of chemistry at Purdue University who was not involved in the study, said the work is important and connects observations rooted in chemistry and biology to a flurry of research that has linked microplastics to health concerns.
“It’s direct evidence of the fact that microplastics have a significant role in biological processes — and an unwelcome role,” Cooks said. “I think it’s going to have strong repercussions in a practical sense.”
Scientists have long thought of most plastics as chemically inert — meaning they are stable and do not easily react with other chemicals. The material is not supposed to easily degrade, which makes it useful for items like food storage containers and is why it can persist for hundreds to thousands of years. But the study busts apart that idea, revealing instead that plastic does cause a chemical reaction in water.
“Once something is deeply embedded like that in scientific minds and in everybody’s minds, there’s no reason to take some plastic and sit and do some careful experiments,” Cooks said. “Everybody knows nothing is going to happen, except that they don’t.”
Plastic is hydrophobic, meaning it repels water. The new study shows, however, that when the two substances are next to each other, plastic can create an electrical field, which peels away electrons from water molecules and releases free radicals. This effect is not much of a concern with large chunks of plastic, but smaller particles create stronger electrical fields.
And microplastics offer much more surface area for reactions to take place relative to consolidated, bulk plastic.
“It’s the magic of the size of the plastic. Nothing else. It’s not the plastic that’s reacting. It’s the water that’s reacting,” Cooks said.
To illustrate these concepts, Min described a plastic credit card: “If you break the whole credit card of plastic into micron-sized microplastics, the interfacial area that can be exposed to water increases by more than 1,000-fold,” he said.
The researchers think this mechanism has been overlooked and could be contributing to the health risks associated with microplastics. But more research is needed.
“We cannot conclude by saying, ‘OK, this is exactly how plastic exerts its toxicity,’” Min said. “But we can certainly say that this could be a contributing factor. It’s just that how big this factor is requires some further studies.”
Microplastics have become ubiquitous. Scientists have found microplastic pollution in snow near the summit of Mount Everest and in the deepest parts of the ocean, like the Mariana Trench. People regularly inhale or consume microplastics in food and drinks.
Cooks said microplastics should be recognized as a source of pollution and a societal problem that requires collective action and government cleanup efforts.
“We are all full of microplastics already. … This chemistry is going on,” he said. “How do we remove it from the environment or from acquisition by people — ingestion — and how do we avoid forming microplastics?”
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