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You're eating, drinking, and breathing microplastics. Now what?

What are the health implications of eating 250 pieces of microplastic per day?

Anna Robuck

Marine Science

University of Rhode Island

A new study led by Kieran D. Cox and researchers at the University of Victoria in British Columbia confirms a logical but cringe-worthy conclusion: humans are consuming plastic. The researchers estimate that humans are eating about 250 pieces of microplastic per day, or roughly 94,000 microplastics in a given year. The average amount consumed varies with age and gender, but the basic premise remains.

Microplastics are tiny pieces of plastics, generally less than 5 mm (one-fifth of an inch) in width. Most consumed by humans are tinier still, frequently in the micrometer range and invisible to the naked eye (25,400 micrometers = one inch). These tiny plastic pieces can form from the breakdown of mismanaged plastic waste over time, or can be directly created for different commercial or industrial applications, like microbeads in facial wash and toothpaste. Synthetic fibers called microfibers can also slough off clothing during the laundry process.

These tiny fragments and fibers have garnered a surge of research attention over the past decade, buoyed by public interest and a continuing stream of viral videos and photos viscerally demonstrating the impacts of plastics on ocean creatures like turtles, whales, and seabirds. The ever-expanding body of research continues to detect plastic pollution in air, water, the deepest reaches of the ocean, and creatures of all shapes and sizes in between.

It was only a matter of time before someone started quantitatively exploring plastic ingestion in our own bodies. But humans are difficult study subjects compared to other organisms. It’s hard to safely and ethically investigate plastics in human subjects, and some of the most obvious screening approaches involve combing through a particularly unappealing type of sample 💩.

Two apples in a clear plastic bag

Life in plastic, not so fantastic. 

Sophia Marston on Unsplash 

Researchers in this study got around some of the challenges of human research by instead focusing on existing, published data. They combed through datasets detailing microplastic counts in honey, salt, alcohol, tap water, sugar, bottled water, seafood, and air, and used these figures in combination with dietary habit data, estimates of drinking water consumption, and data about how much we breathe to arrive at an estimate regarding the number of tiny plastic pieces American children and adults may be consuming via eating, drinking, and breathing.

They found our air, water, and food contain variable concentrations of microplastics, and different ages and genders are likely consuming different amounts of microplastics per day. These results aren’t surprising. Our food system is grossly reliant on plastic at virtually every step of production, transport, and storage. Plastic is durable yet not infallible, and it’s unrealistic to think we can surround ourselves and our food with it and avoid tiny pieces breaking free here and there during its life cycle.

The study’s drinking water findings highlight this particularly well—tap water contains about four plastic particles per liter, while the bottled variety contains about 94 particles per liter. Water is naturally plastic free, leaving just one key variable driving these plastic concentrations (hint: it's the plastic bottle!). 

What may be most surprising about their results is their understated nature. The study focused on food, water, and air, but only included plastic concentrations from food items with rigorous data, meaning that studies had to report exact counts or average concentrations of plastic. The existing studies also had to note what kind of plastic was found in a given sample (fiber, fragment, etc.), and note what methods were used to verify that a given particle was actually plastic. Twenty-six studies met these criteria. 

This means the study only estimates the number of microplastics ingested via 15% of the calories comprising a typical American diet—and the researchers still found hundreds of pieces ingested per day. This approach still leaves out some of the most common and healthful food groups due to limited data, such as meat, vegetables, dairy, grains, and fruits. We still have scant idea what microplastic concentrations are associated with roughly 85% of a typical diet, and that’s cause for concern.

Yet cause for concern shouldn’t be a cause for panic. More than anything this study highlights the necessity for further research and conscientious consideration of our relationship with plastic. As one of the study’s authors pointed out, hazard is much different from risk. We know plastic abounds in the natural environment, and now we know we are consuming it, drinking it, and breathing it. We could be eating plastic and sending it down the drain with each bathroom break. 

Empty plastic water bottle

Brian Yurasits on Unsplash

On the flip side, we could be absorbing plastic bits into our tissues and cells, prompting bodily responses that we haven’t quite picked up on or barely understand. Realistically, something between the two is likely ongoing, but we don’t have enough information to actually identify risks or harmful effects from the information at hand, much less deduce what human plastic ingestion means beyond individual exposure.

Wildlife proxies tell us figuring out how plastic could be hurting us is worth the time and effort—some species are being decimated by plastic, while others seem unfazed or even slightly aided and abetted by plastic exposure. Given our often unnecessary use of single-use and disposable plastics, data outlining the exposure and risk of plastic indulgences, such as that presented in this new publication, will be key to make informed choices. This type of information will likely also provide yet another reason to stymie the burgeoning tide of plastic production and waste choking environments around the globe.

Comment Peer Commentary

We ask other scientists from our Consortium to respond to articles with commentary from their expert perspective.

Max Levy

Chemical Engineering

University of Colorado Boulder

Really enjoyed this! I totally agree that the jury is out on the actual health implications of microplastics. I’m curious if there are any studies that actually sought to answer the most interesting question that you touched on: are we pooping plastic? It’s obviously super unlikely that these come out in the urine (I think the size limit on kidney filtration is less than 6 nanometers). So maybe these plastics are building up in the liver and eventually sailing away? Seems like a reasonably easy experiment to look at stool samples… not that I’d volunteer to be that grad student.

Anna Robuck responds:

Someone has looked at a small subset of samples, and yes, we are pooping them out!

Molly Sargen

Bacteriology

Harvard University

Yikes! Like Anna said, this seems like a logical conclusion. It’s great that this group decided to investigate, since a study about humans brings more awareness to the issue. Personally, I’d heard about microplastics in toothpaste, but I didn’t realize their prevalence in the environment and other areas of my life until Massive’s articles this week. This study raises two big questions for me: 1) How are microplastics permeating so many of the materials we use every day? Do  they come from primarily from degradation of larger plastics or commercial microplastics? 2) Where do microplastics ultimately end up in humans? If they don’t pass through the body, they likely accumulate somewhere. It’s concerning that microplastics are intentionally used in so many commercial products when questions like these have so little research. 

Anna Robuck responds:

Hi Molly! Great questions. I’ll answer to the degree my expertise allows…microplastics are everywhere because plastics are everywhere. Plastic products and containers fracture and shed tiny pieces all the time during use, in addition to products with tiny plastics purposely added for one supposed benefit or another. This degradation from larger plastics is significant source of plastic exposure, both to humans and wildlife. And I don’t think we know where plastics end up in humans yet! There is some evidence suggesting plastic fibers could puncture cell membranes or tissues, or become embedded in human tissues, but honestly we don’t have nearly enough data to describe plastic fate and transport within the human body yet.