Microplastics May Harm the Body by Turning Water Into Damaging Molecules, Study Published in Nature Finds

NEW YORK — Scientists have long linked microplastics to health risks, but how the tiny particles cause harm inside the body has remained unclear. A new study offers a possible answer that challenges a long-held assumption: that plastic is largely inert.

Researchers from Columbia University and the University of California, Berkeley, found that when microplastics come into contact with water, as they do in bottled drinks or once absorbed into the bloodstream, they can spontaneously generate highly reactive molecules known to damage tissue.

The findings were published Wednesday in the journal Nature.

Plastics found throughout the body

Over the past decade, scientists have detected microplastics in nearly every part of the human body, including the lungs, bloodstream and even placentas. The particles have been associated in research with heart attacks, strokes, dementia and other health problems.

Laboratory studies have also shown that microplastics can cause inflammation, oxidative stress and reduced activity in mitochondria, the energy-producing parts of cells. But researchers have struggled to explain the chemistry behind those effects.

The new study identifies a previously overlooked mechanism that may help bridge that gap.

A reactive surface

Plastics are widely used in food packaging, bottles and children's toys in part because they are considered chemically stable. The researchers found that this assumption may not hold for the tiny fragments that break off from larger plastic items.

Plastic is hydrophobic, meaning it repels water. The study found that where microplastics meet water, the water molecules at that boundary become chemically active.

That interaction produces what scientists call reactive oxygen species, or ROS, a type of unstable molecule that can damage cells, proteins and DNA.

Naixin Qian, a postdoctoral researcher at Columbia who helped lead the work, said the molecules generated are "textbook examples of the kinds of molecules that can damage animal and human tissue."

Why size matters

The effect appears to be especially significant for microplastics because breaking plastic into tiny pieces dramatically increases the amount of surface area exposed to water.

Wei Min, a Columbia professor of chemistry and biomedical engineering and senior author of the study, said microplastics alter the water surrounding them, generating high-energy, reactive radicals that "very likely contribute to biological damage" seen in animals and potentially in humans exposed to microplastics.

The research suggests that microplastics that enter the bloodstream or cells could remain chemically active in the body's water-rich environment, continuing to produce harmful molecules.

Challenging assumptions

The findings challenge the common view of microplastics as passive fragments that cause harm mainly through physical irritation or by carrying toxic chemicals.

Previous research has focused on chemical additives in plastics, such as plasticizers and stabilizers, as well as pollutants that cling to plastic particles. The new study suggests the plastic itself, in fragmented form, may be a direct source of harmful chemistry.

Experts told Scientific American that the work gives scientists a new way to think about plastic pollution. It implies that oxidative stress, a process linked to aging and many diseases, may be a direct effect of microplastic exposure rather than a secondary consequence.

What it means for health

Oxidative stress occurs when the body produces more reactive molecules than it can neutralize. Over time, it has been linked to inflammation, cardiovascular disease, neurodegenerative conditions and cancer.

The study does not directly show that microplastics cause specific diseases in people. Rather, it identifies a chemical process that could explain the biological damage observed in earlier laboratory and animal studies.

More research will be needed to determine how much of this reactive activity occurs inside the human body and at what levels it becomes harmful.

Possible solutions

The researchers said their findings could eventually help reduce the harm caused by plastics.

Berkeley chemist Teresa Head-Gordon, a co-author, said that understanding how the most water-repellent microplastics drive chemical reactions could lead to engineering solutions, including redesigning the chemistry of common plastics to reduce their toxic effects on health and the environment.

A growing concern

Global plastic production has grown dramatically over recent decades, and plastic waste breaks down into ever-smaller fragments that spread through water, soil, air and the food supply.

People are exposed to microplastics through food, drinking water and the air they breathe. Studies have found particles in bottled water, seafood, salt and household dust.

There is currently no proven way to remove microplastics from the body, and experts generally recommend reducing exposure where possible, such as avoiding heating food in plastic containers and limiting the use of single-use plastics.

What's next

The researchers said further studies will examine how the reactive molecules produced by microplastics affect living cells and organs, and whether certain types of plastics are more harmful than others.

The work adds to growing calls from scientists and health advocates for stronger action to curb plastic pollution, as evidence mounts that the problem may pose risks not only to the environment but also to human health.