We're hearing a lot about microplastics — those teeny pieces of plastic that have become so ubiquitous in our water, air and soil that they can now be found in human blood. These minuscule pieces of plastic are the product of broken-down waste because plastic does not biodegrade like other materials. Plastics make up a bulk of our packaging, toys, cars, toiletries and building materials; the list goes on and on.
What's more, plastics are made up of numerous toxins and chemicals that, when broken down, seep into every aspect of our lives. But how do they actually get into our bodies?
How Microplastics Enter the Human Body
In a new study published in the journal Science of the Total Environment, researchers explore how microplastics enter our blood at the molecular level. For this research, scientists focused on polystyrene plastics, which are most often used in food packaging, and nanotubes used in sporting goods, coatings and electronics.
They found that microplastics likely enter the human body via diet and inhalation before being engulfed by macrophages, a white blood cell that surrounds and kills foreign materials as part of your body's immune response. A receptor found on macrophages known as TIM4 binds to the microplastics in an effort to break them down.
Read More: We're All a Little Plastic on the Inside
Microplastic Effects on Humans
According to study author Masafumi Nakayama, a professor at Ritsumeikan University in Honshu, Japan, by understanding the macrophage process, researchers can better understand how they impact health in the body.
When TIM4 receptors become damaged while trying to bind to microplastics, for example, the immune response causes inflammation in the body. But if the receptor remains unharmed when binding to and engulfing the microplastic, then no inflammation results. Whether or not the receptor is damaged depends on the microplastic's type, size and shape. For this study, researchers compared carbon nanotubes to polystyrene.
"This is the reason why carbon nanotubes cause inflammation in the body, and polystyrenes generally don't," says Nakayama.
This is the first time we've looked at this process at a molecular level. But we already know that nanoplastics may be able to penetrate cell membranes in the gut and make their way to other organs, says Michael Kleinman, a professor of environmental toxicology at the University of California Irvine, who was not involved in the study.
"These can also deposit on sensitive lung tissues and could trigger irritation and inflammation," he says.
Read More: Microplastics Are Everywhere. What Are They Doing to Our Health?
Are Microplastics Harmful?
Once microplastics and their smaller cousins, nanoplastics, break down in the environment, it's hard to remove them from water and air because they're so tiny. And there's still a lot that we don't know about how harmful these contaminants can be. But there likely is an impact.
"There is evidence from animal and cell culture studies that NP (nanoplastics) exposures are pro-inflammatory and can induce oxidative stress," says Kleinman. "When they occur in humans, these changes could be associated with lung and heart diseases, but definitive human studies are lacking at this time."
Kleinman contends that BPA (Bisphenol A), phthalates and heavy metals that break down in plastics are known to be toxic to humans. The plastics that contain leachable toxic components like BPA are probably worse for us, but they're far from the only problem.
"The physical presence of nanoplastics in biological tissues may be sufficiently irritating that they can induce local inflammation in the lungs and gut linings," says Kleinman.
We're only beginning to understand the breadth of the problem because the research into how microplastics impact human health is still in its infancy.
Read More: The Fight Against Microplastics
How to Avoid Microplastics
Kleinman says that we still don't know enough about how many nanoplastics are distributed in our environment and how much they build up in our bodies. And if they are already broken down in the air, water and soil, avoiding them becomes next to impossible.
While in your own life, you can reduce plastic exposure by buying produce and foods not wrapped in plastics, choosing glass containers instead of plastic, bringing your own bags, avoiding plastic water bottles, etc., it's hard to know our full exposure. Because, in the end, microplastics are a societal and global problem that can't just be solved at home.
Read More: Americans Rank First in Plastic Waste Contribution
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Environment International. Discovery and quantification of plastic particle pollution in human blood
Science of The Total Environment. Tim4, a macrophage receptor for apoptotic cells, binds polystyrene microplastics via aromatic-aromatic interactions
Professor at Ritsumeikan University in Honshu, Japan. Masafumi Nakayama
Britannica. Polystyrene
Professor of environmental toxicology at the University of California Irvine. Michael Kleinman
National Institute of Environmental Health Sciences. Bisphenol A (BPA)
Sara Novak is a science journalist based in South Carolina. In addition to writing for Discover, her work appears in Scientific American, Popular Science, New Scientist, Sierra Magazine, Astronomy Magazine, and many more. She graduated with a bachelor’s degree in Journalism from the Grady School of Journalism at the University of Georgia. She's also a candidate for a master’s degree in science writing from Johns Hopkins University, (expected graduation 2023).
