The study of how plastic pollution affects humans and animals is a relatively new field. There isn’t much research published yet, nor are there more than two ways to reliably test for plastics in the body. However, researchers have long insisted that micro- and nanoplastics (MNPs) accumulate in the human body, likely contributing to comorbidities.

Almost a year ago, in February 2025, a study was published regarding plastic findings in cadaver brains. In one of these brains, researchers found that 0.48% of it comprised microplastics — enough plastic to make a spoon.

On January 13, The Guardian’s environmental editor, Damian Carrington, published a lengthy article giving voice to the growing number of scientists who believe that the conclusion on microplastics inside humans is flawed. Carrington wrote:

There is no suggestion of malpractice, but researchers told the Guardian of their concern that the race to publish results, in some cases by groups with limited analytical expertise, has led to rushed results and routine scientific checks sometimes being overlooked.

The Guardian has identified seven studies that have been challenged by researchers publishing criticism in the respective journals, while a recent analysis listed 18 studies that it said had not considered that some human tissue can produce measurements easily confused with the signal given by common plastics.

One of the scientists who is skeptical, Dr. Dušan Materić at the Helmholtz Centre for Environmental Research in Germany, called the February 2025 study a joke. “Fat is known to make false positives for polyethylene,” he stated. “The brain has [approximately] 60% fat.” Polyethylene is one of the most common plastics used.

Carrington further explained, “The problem is that some small molecules in the fumes derived from polyethylene and PVC can also be produced from fats in human tissue. Human samples are ‘digested’ with chemicals to remove tissue before analysis, but if some remains the result can be false positives for MNPs.”

What’s significant and ironic about Carrington’s reporting is that it is a reversal from what — who else? — The Guardian had been printing previously. Writers there had gone all in on MNP internal pollution of the human body. Carrington’s piece represents a major shift in tone.

The Washington Post, however, took the opposite tack. Climate reporter Shannon Osaka argues that even if some of the conclusions in papers like last year’s are not accounting for false positives, what is certain is that other plastics have been detected by scientists in the brain.

“Researchers pointed to the fact that animal studies show clearly that tiny plastics can reach the brain,” Osaka explains. “Researchers have exposed rats and mice to fluorescently tagged nanoplastics in their food, and found those same tiny plastics deep in the brain.”

She insists that it’s “certain” that some microplastics “reach the human body.” Notice she didn’t assert that MNPs linger in internal organs, a claim made by many of these scientists. I don’t think any scientist would argue that people are exposed to and have ingested MNPs. However, there is some doubt about whether those plastics can even accumulate in human organs such as the brain. As environmental chemist Cassandra Rauert told The Guardian, “From what we know about actual exposure in everyday life, it is not biologically plausible that that mass of plastic would actually end up in these organs.”

Taking a step back, we need to analyze the political stakes at play. In science today, findings are rarely neutral; there’s likely a political motive driving divergent conclusions. Is this anti-MNP-ism motivated strictly by helping people, or justifying environmentalist dogma? And even if it’s true that humans have MNPs in their internal organs, how does this affect their health?

Like any science worth its salt, the debate is raging, and if science is allowed to do its thing, some interesting conclusions may be forthcoming on MNPs and their effects on humans. In the meantime, be discerning about sensationalist studies declaring that humans are riddled with MNPs. It’s likely scaremongering to manipulate environmental policy.