How many microplastic particles are really in our bodies?

In the past decade, scientists have been finding evidence of microplastic particles throughout the human body, including the brain and blood, the cardiovascular system, the liver, kidneys, stomach, lungs, even the testicles, and the placenta.

In the last three years, Kara Meister, an assistant professor of otolaryngology-head and neck surgery at Stanford University, has been collecting tonsils she removed from children—and found microplastic particles in all of them. “The question is: are they affecting our health or are they innocent bystanders?” she says.

She’s not alone in asking this question.

How these bits of plastic might be affecting human health is unclear.

“We know definitively that plastic is present in human tissue,” says Susanne Brander, scientific project director of the safer chemicals project at the Pew Charitable Trusts. “What it’s doing to us—that’s the million-dollar question.”

While scientists work to answer that crucial question, a storm has been brewing regarding how microplastics are detected and measured in the human body.  

News articles and commentaries published in scientific journals have questioned some of the more high-profile studies documenting the presence of microplastic particles. Some point to flaws in a study’s methodologies and measurement techniques, or they interpret a study’s results differently than the researchers do. Experts say these debates are a natural part of the scientific process, especially for a relatively new field.

Establishing the presence of microplastics in tissue samples from the human body—and learning more about the effect they’re having—is an urgent public health issue, say many experts. It’s “akin to where we were with tobacco and asbestos in the 1950s. The issue has to be taken very seriously even though we don’t have all the answers,” says Philip Landrigan, a pediatrician and public health physician and director of the Program for Global Public Health and the Common Good at Boston College.

Challenges with measuring microplastics in the body

Evaluating the presence of microplastics in organ or blood samples is a complicated undertaking. Microplastic particles are smaller than five millimeters in diameter, while nanoplastics are smaller than one micrometer in diameter. Most of these particles are invisible to the naked eye.

Results are also vulnerable to potential contamination when the research is conducted amid ambient microplastic particles. After all, these microplastic particles are in our food and drinking water, in dust, suspended in the air, and they can be shed by instruments, synthetic clothing, and other items that are used in operating rooms and laboratories.

Because detecting microplastics in the human body is a relatively new area of science, efforts to figure out the best ways to measure them is ongoing. But that doesn’t mean concerns about the findings to date should be dismissed.

Matthew Campen, a toxicologist at the University of New Mexico College of Pharmacy in Albuquerque, was one of the authors on a widely publicized study in the journal Nature Medicine last year that found microplastic particles in autopsy specimens of the human brain. 

The criticisms Campen and his coauthors received have led them and other researchers to push back against those criticisms, triggering a heated debate. Campen argues that some of the criticisms have come from scientists in different fields, such as analytical chemists, who may have limited experience handling complex biological specimens; however, he concedes that the conversation is important as the science continues to evolve and improve. 

Other experts in the field agree. “All science is questioned and challenged by other scientists—that’s how science works,” says Megan Wolff, a public health expert and executive director of the Physician and Scientist Network Addressing Plastics and Health (P-SNAP). “It’s a self-correcting system.”

How microplastic detection is evolving

Understanding how this type of research works can help us appreciate how and where challenges are likely to arise. Currently, the most commonly used methods rely on sophisticated microscopes and/or approaches that measure the chemical components in tissues that are obtained from surgery or biopsy, Landrigan says.

(Learn how experts who study plastic avoid it in their own homes.)

One of the most common ways scientists try to measure microplastics is by looking at tissue samples under various types of microscope. However, lipids, or fats, in the body can look like polyethylene, a type of plastic, when scientists try to visually detect them in bodily tissues.  

Scientists working in this area are aware of these issues and some have called for better protocols and analytical approaches for measuring microplastics in human tissues and organs.

One technique is called infrared spectroscopy. Researchers shine infrared light on microplastic particles to measure how they absorb the light; then, they compare the spectral findings to plastic polymer spectra in a database to identify the chemical compounds.

By contrast, a different method called pyrolysis gas chromatography involves burning a sample, then testing the gas that comes out of it for certain chemical compounds. A similar and more precise method called pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) has been gaining traction in the field. With Py-GC-MS, researchers rapidly heat a tissue sample so it decomposes into smaller particles. The gases that result are then matched with signatures that are consistent with different types of plastic.

But even Py-GC-MS isn’t foolproof: A study in a 2025 issue of the journal Environmental Science & Technology assessed the efficacy of Py-GC-MS for analyzing nanoplastic and microplastic particles in human blood; the researchers concluded that it is “currently not a suitable analysis method” for detecting polyethylene and polyvinyl chloride particles in blood.

Each of these methods has its challenges and limitations. Which is one reason some scientists are calling for the use of “orthogonal methods,” a term that essentially refers to using multiple approaches to detect and confirm findings.

This approach was used in a study in a 2024 issue of the New England Journal of Medicine, in which researchers analyzed excised carotid plaque specimens for the presence of microplastics and nanoplastics in people being treated for asymptomatic carotid artery disease.

To do this, they used pyrolysis-gas chromatography-mass spectrometry, stable isotope analysis, and electron microscopy. The researchers found that those who had these plastic particles detected had a higher risk of myocardial infarction, stroke, or death from any cause at the 34-month follow-up, compared to those in whom plastic particles were not detected.

(To study microplastic, this scientist is building the ultimate plastic-free lab.)

Some experts, including Meister and Landrigan, view this as a well-designed study, but others disagree. For example, Kevin Thomas, director of the Queensland Alliance for Environmental Health Sciences at the University of Queensland in Brisbane, Australia, thinks what was actually measured in the study is residual lipids in the tissue, rather than plastic particles.   

Looking to the future

Like many areas of science, this one is a work in progress.

“In the field, we’re all trying to improve the analytics that allow us to measure microplastics in human tissues and trying to collaborate and work better together,” says Thomas. “With these materials, it won’t be one technique—it will be a combination of techniques that will give us the answers we’re looking for.”

To minimize background contamination from plastics, Thomas runs what he calls a “plastic-controlled laboratory” at the University of Queensland, which relies on stainless steel instruments, glass and metal containers, and HEPA filters to clean the air.

The ideal lab would have “at least two different analytical methods used on the same sample to have checks and balances,” says Brander. It would also have “samples spiked with plastic to make sure the method is accurate.” That way, the researchers would have a point of reference to measure their findings against.

Additionally, the scientific methods need to be standardized because right now, “we have procedural blanks,” says Campen. “We need well-equipped labs that can do three, four, or five methods to look for microplastics, which is expensive.”

Meister would like to see three categories of instrumentation in these studies—identifying the type of plastic; how much is present; and where it is located at the cellular level in human tissue. “We don’t have a single instrument that can do all three,” she says.  

In addition to honing the scientific methods that are used, research needs to answer the million-dollar question: How does the presence of microplastics and nanoplastics in the body affect human health?

“We know what the chemicals inside microplastics do to us,” says Wolff. “They’re carcinogens, neurotoxins, and endocrine-disrupting chemicals,” meaning they hijack, mimic or interfere with hormones in the body’s endocrine system. “In the public-health world, the question is when do we have proof of harm to start ringing the prevention bells?” Wolff adds.