The Plastic Inside You: What Science Is Learning About Microplastics and Your Health

Plastic is everywhere. It is in our water bottles, food containers, clothes, and furniture. Over time, plastic breaks down into smaller and smaller pieces. These pieces are called microplastics when they are smaller than five millimeters and nanoplastics when they are even smaller. They are now so common that scientists say almost no person on Earth is free of them. The question remains: if no one is free from them, what is happening to us, and what can we do about this environmental pollution?

For years, people assumed these particles simply passed through the body without causing harm. New research says that is not true. Microplastics have been found in human blood, lungs, liver, breast milk, and newborn stool. They have also been found in the human brain and in every human placenta tested in one 2024 study, with amounts ranging from 6.5 to 790 micrograms per gram of tissue. Dr. Matthew Campen, the lead researcher on that study, said he is especially concerned about the placenta because it forms and grows in only eight months, giving plastic less time to build up there than in other organs, yet it still does.

Physical Health: A Growing List of Concerns

The clearest physical health warning so far comes from a 2024 study published in The New England Journal of Medicine. Researchers led by Dr. Raffaele Marfella studied about 300 patients in Italy undergoing surgery to clear plaque from an artery in the neck. They found that patients who had microplastics inside that plaque were four and a half times more likely to have a heart attack, a stroke, or to die within about three years, compared to patients without plastic in their plaque. In the study, 20 percent of the patients with plastic in their arteries had a major health event, compared to just 7.5 percent of those without it.

The two most common plastics found in the arteries were polyethylene, used in bags and bottles, and polyvinyl chloride, used in pipes and medical equipment. The researchers were careful to say this study shows a strong link, not proof that the plastic itself causes heart attacks and strokes. But they also found that patients with more plastic in their arteries had higher levels of inflammation in their blood, which may be one way plastic harms the body. It is well known that inflammation is not only involved in physical health but also seems to play a significant role in psychiatric disorders such as depression and possibly Alzheimer’s.

Animal and lab studies raise additional concerns. Scientists at Stanford Medicine report that microplastics are linked to inflammation, immune system problems, tissue damage, and problems in how organs develop. Dr. Juyong Brian Kim, who studies this at Stanford, found that these particles can get inside cells and change how genes behave. Dr. Kara Meister, also at Stanford, found microplastics in the tonsils of children, raising questions about their effects on a child’s hormones and thyroid.

At the University of Texas at Austin, a research group called EMPATHIC is studying whether microplastics play a role in cancer, including the rise in cancer among younger people. Their early work shows that microplastics can cause changes inside cells before any damage is visible under a microscope. The researchers point out that microplastics are not one substance. They come in many sizes, shapes, and chemical types, which is part of why they are so hard to study and regulate.

Mental Health: A Newer and Troubling Picture

Physical health is not the only concern. A growing number of doctors are looking at what microplastics might be doing to our mood and our minds. Dr. Mitchell Liester explains that microplastics have been found in human blood, lungs, liver, placenta, breast milk, and brain tissue, and that a 2025 review confirmed these particles can cross into the brain.

Once inside the body, plastic particles can carry chemicals that interfere with hormones, including estrogen, testosterone, thyroid hormone, and cortisol, the hormone tied to stress. Dr. Liester writes that these chemicals disrupt the primary systems that control reproductive function, metabolism, sleep, stress response, and mood.

Research also shows that microplastics can affect brain chemicals tied to mood, including dopamine, serotonin, glutamate, and GABA. Lower dopamine is linked to a loss of pleasure and to depression. Lower serotonin markers are linked to anxiety and depression as well. Some scientists believe part of this effect starts in the gut. Microplastics appear to disturb healthy gut bacteria and make the gut lining more permeable, which can trigger inflammation that reaches the brain through what researchers call the gut-brain connection.

Animal studies add more detail. Animals exposed to nanoplastics have shown depression-like behavior, trouble interacting socially, and changes similar to those seen in autism spectrum disorder. Researchers stress that these are animal studies, not proof of the same outcome in people. Still, doctors say the pattern is concerning enough to take seriously, especially since children and pregnant women are exposed to the same plastic-filled environment as everyone else.

How many infants are fed with baby bottles made of plastic? When I was a young girl and one of my sisters had her first child, my mother boiled glass baby bottles in a special pot on the stove. Nipples were similarly treated to a bubbling hot bath on the stove. Did the nipples release microplastics into the infant? That question is left up in the air because plastics weren’t so widespread in everything we use.

What Experts Say We Should Do

No one is telling people to panic, and no one claims you can remove all plastic from your life. But researchers and physicians have specific, doable advice for lowering your exposure.

Deborah Bennett, an exposure scientist at the University of California, Davis, recommends these changes.

Do not microwave food in plastic containers, since heat can release large numbers of particles into your food.

Store leftovers in glass or stainless steel instead of plastic.

Choose sheets and bedding made from cotton, linen, or wool rather than synthetic fabrics.

Wash synthetic clothing in cold water and let it air dry, since heat and tumbling in a dryer break fabric down into microfibers.

Drink tap water instead of bottled water, since bottled water contains far more microplastic particles.

Cut back on fast food and heavily processed food, since the packaging carries more chemicals.

Swap plastic cooking utensils for wooden or metal ones.

Choose wood or natural rubber toys for young children.

Cut back on scented personal care and cleaning products, since fragrance often hides plastic-based chemicals.

Dust and vacuum regularly, ideally with a vacuum that has a HEPA filter, since household dust carries plastic fibers that we can breathe in.

Dr. Liester adds a few more ideas to protect mental as well as physical health. He suggests:

filtering drinking water

switching to glass containers for food storage

eating more fiber- and antioxidant-rich foods, which may help protect the gut and lower inflammation.

He also encourages people to support stricter rules on plastic production and disposal, since personal choices alone cannot solve a problem this widespread.

Dr. Desiree LaBeaud at Stanford put the bigger challenge simply. Plastic never goes away, she said; it just breaks down into finer and finer particles. That’s why many researchers say the long-term fix has to include less plastic production in the first place, not just smarter choices by individual households.

Plastic production is not slowing down. Estimates suggest 10 to 40 million metric tons of plastic waste enter the environment every year, and that number could double by 2040. That means the amount of plastic in our air, food, and water is likely to keep rising unless something changes on a much larger scale.

For now, the science is still developing. Researchers are honest that they do not yet know exactly how much microplastic it takes to cause harm or which effects are the most serious. They do agree that these particles are inside almost all of us, that early research links them to real physical and mental health risks, and that small, steady changes at home can lower how much we take in. Until governments and industries make bigger changes, those small steps are the most practical tools people have.