In recent years, there’s been a wave of studies reporting that humans are basically full of microplastics: They’ve been found in our brains, arteries, and even in placentas.
But some scientists, quoted and cited in an article published by the Guardian this week, have critiqued some of those findings, saying that microplastics research has been muddied by issues like contamination and false positives.
One chemist even told the outlet that these criticisms are “forcing us to re-evaluate everything we think we know about microplastics in the body.”
However, other scientists who study microplastics and human health say that this framing is overblown.
While they concede that the field of studying microplastics in our bodies is new—and that some concerns over study methodologies are valid—readers should not conclude that the entire area of study is filled with errors.
And, they add, it’s an irrefutable fact that microplastics are present in human bodies.
What are the critiques of microplastic studies?
When plastics break down, they form these tiny fragments we call microplastics, defined as pieces less than 5 millimeters in length.
There are also nanoplastics, which are even smaller particles, usually considered smaller than 1,000 nanometers—which is about 100 times smaller than the diameter of a human hair.
Research has found them in the air, the soil, and our bodies. But in comments to scientific journals and a recent Guardian article, some scientists have challenged the way that researchers have identified these microplastics, particularly in human organs.
One study, which said that the levels of microplastics in human brains are rapidly rising, was critiqued for having limited controls around contamination, and for not validating potential false-positives.
“Fat is known to make false-positives for polyethylene. The brain has [approximately] 60% fat,” Dr. Dušan Materić, at the Helmholtz Centre for Environmental Research in Germany, told the Guardian.
Other studies, which found microplastics in arteries, were criticized for not testing blank samples taken in the operating room, basically a way to measure if there’s any background contamination to start.
Researchers who wrote comments to scientific journal editors also generally highlighted that the “the analytical approach” used in some microplastic studies is “not robust enough to support [their] claims.”
What do these critiques really mean?
Microplastics researchers do understand that there are methodological challenges to studying microplastics in human organs. That’s because the field itself is still new.
“The tools are in their infancy,” Kara Meister, a pediatric ear, nose, and throat doctor with Stanford Medicine who also studies how our environment—including the presence of microplastics—affects our immune system, told Fast Company.
“None of these tools [to detect microplastics] were developed specifically to look at this problem, so we’re borrowing from other science and then trying to apply that to a brand new field,” she adds.
The critiques, then, do have truth to them.
Yes, microplastics can be confused with fats, Meister says. That’s because microplastics are often made from polymers (meaning something with repeated bonds or a predictable structure), which is also how several human tissues like fats are made. Scientific tools can’t always parse the two.
And yes, limiting contamination is a challenge. That’s because microplastics are everywhere.
“When we take human tissue, whether that’s a blood sample or a tissue sample from the body, we’re doing it in an operating room that is full of plastic,” Meister says.
In her lab, she uses metal instruments and wraps samples in sterile foil, but there are still ambient microplastics that might lead to some element of contamination.
And yes, there are issues around having a positive or negative control in a study—basically, a control to compare a sample to show this is what it looks like with or without microplastics.
“In a perfect study, we would know, if I took this tonsil and I spiked it with known polyethylene, are we picking that up right in the tools?” she says. “The problem is that the plastics that you can buy in a laboratory setting to be able to test these, they’re not actually what we’re encountering in real life.”
In real life, microplastics are not one specific thing; they have multiple characteristics. Take microplastics from a plastic bottle—if those contaminate your body, your body isn’t only seeing the polyethylene.
Your body also sees “things like BPA, heavy metals, dyes, ink—all the things that come with it,” Meister says. Microplastics are also known to carry bacteria and other proteins, “like a little raft” they attach to.
This means when scientists look for microplastics in our bodies, they’re not just looking for one thing.
“It’s really hard to measure, because it’s a category of a whole bunch of diverse different things. And we also know that there are over 350,000 different proprietary chemicals in the world.”
Along with all these challenges, it’s also difficult for researchers to compare their findings across labs or research techniques. There aren’t standards for how to measure microplastics or tools researchers should use.
Scientists know about these caveats
So there are challenges to measuring microplastics, but scientists working to study this already know that.
Ideally, Meister says, researchers would measure microplastics in three ways: identify (what is the polymer; is it polyethylene, for example, or maybe PVC?); quantify (how many particles, and how big are they?); and localize (where are they within human tissue?).
The problem is, there isn’t yet one measurement technique that can answer all three of those questions.
“That leaves triangulating different types of measurements and some gaps in the science,” she says. “We will get there, but it’s going to take trial and error to get better standards and accelerate the data.”
Megan Wolff, executive director of the Physician and Scientist Network for Advocacy on Plastics and Health, put it this way on LinkedIn: “methodological uncertainty is a normal feature of science, especially in a newly evolving discipline.”
In some cases, the critiques raised in the Guardian article were also acknowledged by the original study authors. These caveats, though, may not always be clear in media stories or to the general public.
Concerns over framing
Critiquing studies itself isn’t controversial, Wolff added; that’s part of how science evolves. But Wolff took issue with the way the critiques were framed.
In both the Guardian’s headline and lede, the article highlights a quote calling the critiques of the brain study “a bombshell.”
That phrase is attributed to Roger Kuhlman, a chemist formerly at the Dow Chemical Company, and the same source who said that the critiques are “forcing us to re-evaluate everything we think we know about microplastics in the body.”
The fact that this chemist formerly worked at Dow, a major plastics manufacturer, was a controversial choice to Wolff. Dow has “a vested interest in casting doubt on the science of plastics, microplastics, and human health, she wrote.
Kulhman’s “bombshell” comment was in response to a study assessing a specific analysis method for quantifying plastics in human blood, and which found those tools are “not a suitable analysis method” for two types of plastic, polyethylene and polyvinyl chloride, in uhman tissue.
In a statement to Fast Company, Kuhlman stood by this framing, and his concerns about the way that “questionable results” in scientific studies have been “trumped to popular media outlets as solid scientific facts.”
“Scientists have traditionally been conservative with public descriptions of early-stage results for good reason,” he added. “I hope the article in The Guardian and related reports help level-set public expectations to the true state of current scientific understanding, which is that we know almost nothing about concentrations of micro- and nanoplastics in human bodies.”
Kuhlman also disputed the idea that his experience at Dow would color his comments. “I am not, nor have I ever been, a corporate spokesman—I was a lab rat,” he said. “Both throughout and after my employment, environmental issues (especially climate change) have been critical to me and guided my priorities and thinking.”
Should concerns diminish the whole field?
Even with some problematic studies, cross contamination, and difficulties quantifying microplastics in human tissue, Wolff emphasized that there are a few irrefutable facts about microplastics and our bodies, “regardless of measurement techniques,” Wolff adds.
Those facts are: Microplastics are present in human bodies, “from blood to brains to bones”; microplastics are made of fossil carbon and chemical additives, many of which are known to be toxic; and hazardous chemicals are always leaching out of plastics—including when we eat off plastic, drink out of plastic, or wear plastic—meaning that plastic degrades throughout its environment.
So maybe scientists don’t know how many microplastics are in our bodies, or what exactly they’re doing to us. But they’re trying to figure that out.
And as Leonardo Trasande, director of NYU Langone Health’s Center for the Investigation of Environmental Hazards, put it in his own LinkedIn post: “As a new field, there are of course going to be bumps in the road and a need to recalibrate our understanding.”
But the Guardian article, he added, risks damaging all researchers who study this. “It implies that the entire field is lacking in rigor,” he wrote. “That’s just not the case.”
In a statement to Fast Company, the Guardian said it would not be providing additional comments “as the story speaks for itself.”
When it comes to studying microplastics in our bodies, the question of exactly how many there are in our brains or blood might not even be the most important one, scientifically, to ask.
“It’s probably there, yeah,” Meister says. “Is it actually harming us? That’s the question we’re trying to answer.”
Even if we don’t know specifically how they’re impacting human health, “we know that microplastics are hurting the environment,” Meister says.
Wolff, in her post on LinkedIn, was even more blunt: “The science, for its own part, is clear,” she wrote. “Exposure to plastic is harmful, be it through large items or tiny particles.”
