Recent studies have found that microplastics, tiny fragments and fibers of the petrochemical-based materials, are everywhere. They contaminate our salt and float around in our beer, and fish and shellfish are full of it. Another study from earlier this year estimated that 114 plastic fibers fall onto the average dinner plate during a 20-minute meal. So it seemed inevitable that researchers would eventually find bits of the material inside of us: scientists in Austria recently claimed they detected microplastics in human stools for the first time. 

The study, conducted by the Medical University of Vienna in cooperation with the Environment Agency Austria, was recently presented at the United European Gastroenterology Week in Vienna. The research team recruited eight people from nations across the globe, including Finland, Italy, Japan, Poland, Russia and the Netherlands. Each participant was instructed to keep a food journal of everything they ate for one week before a stool sample was taken. All of the subjects ate some food wrapped or packaged in plastic, and six of them ate seafood during the week.

The Environment Agency then tested their feces using newly developed analytical procedures designed to find 10 different types of plastic. What they discovered is that the poop was studded with nine types of plastic. On average, there were 20 microparticles per 10 grams of stool, ranging from 50 micrometers, half the size of a human hair, to 500 micrometers. 

“This is the first study of its kind and confirms what we have long suspected, that plastics ultimately reach the human gut,” lead researcher Philipp Schwabl of the Medical College, who presented the findings says in a statement. “Of particular concern is what this means to us, and especially patients with gastrointestinal diseases. While the highest plastic concentrations in animal studies have been found in the gut, the smallest microplastic particles are capable of entering the blood stream, lymphatic system, and may even reach the liver.”

Considering how much plastic is in the environments we live in, it’s not surprising that some of it would turn up in humans. But critics of the study caution that the research needs to be taken with a grain of plastic-free salt. They point out that the sample size, just eight people, is very small. The research has yet to go through the peer-review process meaning any potential errors have not been detected. Then there’s the possibility that, considering how many flecks of plastic are around us, the plastic could have been contaminated from the lab or another source. 

The authors say they plan to submit a full-fledged study for peer review in the coming months. Whether or not their study is accepted, it raises legitimate questions. How much plastic are we exposed to? What do we know about the impact of plastic on human health? 

There are few readily available answers to those questions. Currently, we have not studied most plastics in-depth enough to say whether one type is safe and another is not, says Karin B. Michels, chair of the epidemiology department at UCLA. “We inhale plastic from our shower curtain when the water hits it, we’re surrounded by plastic floors, we get it from pants that are coated in plastic. Plastic is everywhere,” she says. “We eat it, inhale it, we get it through our skin. We use plastic because we’re trying to make our life more comfortable. The question is, is that bad?” 

Animal research on several types of plastics suggests there is something to worry about. Chemicals in plastic have been linked to disruptions in the endocrine system, infertility, metabolic effects like obesity and diabetes, and even impact the brains of developing embryos. Patricia Hunt at Washington State University who studies reproduction and exposure to bisphenol A (BPA), a plastic additive linked to many of these effects, says that animal studies are one thing, but studying plastic exposure in humans is much more difficult.

That’s because almost everyone is already contaminated by plastics. She’s not worried so much about microplastics in our stool, which are large enough to have passed through our systems. Instead, she’s more concerned with the plastic bits and residues mixed into our food and water, that cling to dust particles in the air to which we’re exposed daily, that leach chemicals we absorb. The problem is so widespread, she says, that it’s made designing studies on humans difficult, since even people in remote parts of the world are contaminated. 

The plastic components we’ve studied most, phthalates and bisphenol A, show that we have reasons to worry about their toxicity and impact on developing children. Even “safer” alternatives to plastics like BPA aren’t a solution. In a recent study, Hunt and her colleagues found that many of the “BPA-free” products on the market, which often substitute a different form of bisphenol for BPA, led to the same type of genetic damage as BPA. 

The FDA is not regulating these products because there’s not enough evidence that they are harming humans. Both Hunt and Michels say a lot more effort and funding needs to go into research on plastics. “We can’t base recommendations or regulations on animal studies alone,” Michels says. “We need a lot more studies on plastics including those used in food containers and wrapping materials. The bottom line is we have to be very concerned about plastics in general since there are indications they are harmful to our health. But we’re not at the point where we can say this plastic is bad and this one is not.”

Getting rid of plastic already in the environment means designing novel ways of disposing of microplastics, like finding microbes than can digest and break them down. Hunt suggests scientists need to practice green chemistry: testing the health impacts of plastics before they make it on the market.

Epidemiologists and the American Academy of Pediatrics recommend avoiding using certain plastics with children. Plastic shouldn’t be exposed to heat, like in the dishwasher, since that can cause it to start leaching chemicals.  Michels, for one, warns that food should never be heated up in the microwave in plastic. Soda bottles, which are designed for one time use, should never be refilled. She herself uses glass and stainless steel containers when she can. At the grocery store deli, she tries to avoid plastic as well, asking for foods like cheese to be wrapped in paper. Michels avoids taking receipts, which are coated in BPA. 

But then again, plastic is so prevalent, completely avoiding it could be a major challenge. “Should you stop eating yogurt, which is all in plastic tubs, or fish? How far do you want to go?” Michels says. “There are so many products in plastic containers that have not been sufficiently studied.”