GoKawiilPervasive plastic contamination and unreliable methods have clouded the science on microplastics in the human body. In an interview, Australian scientist Cassandra Rauert, who built a plastics-free lab to study human exposure, explores the challenges for researchers.
Scientists have been documenting the presence of microplastics in our oceans and soils, in air, drinking water, and food for more than a decade. More recently, peer-reviewed studies have revealed the presence of microplastics in the human body. But how much plastic do we consume, where is it coming from, and what is it doing to us? Cassandra Rauert, an environmental chemist at the University of Queensland, in Australia, conducts research to better understand the impacts of such exposures. Her work has shown that the current analytical techniques used for detecting plastic in human blood are vulnerable to contamination from the lab environment. And last year, she published an attention-grabbing paper that found lipids present in blood can give false positives for the most commonly produced plastic, polyethylene. All of which suggests that some reported levels of microplastics in humans may be overestimated. In an interview with Yale Environment 360, Rauert describes how, after learning about the potential for microplastics to infiltrate a lab — whether from construction materials, equipment, clothing, or the air — she and her fellow researchers painstakingly rebuilt their workspace, using glass and steel, to drastically reduce the odds of contamination. The hope is that once researchers can accurately measure levels of microplastics in human tissue and blood, they’ll be able to determine what exactly plastic pollution is doing to us. “I don’t think we’ve got really good evidence at all for what effects [microplastics] might be having,” Rauert says. And the much-hyped finding that we eat a credit card’s worth of plastic each week? “That has absolutely been debunked.”
Cassandra Rauert. Courtesy of Cassandra Rauert
Yale Environment 360: Why is it so hard to study microplastics in the human body? Cassandra Rauert: It’s quite a new field. And we’re trying to use analytical techniques that were developed for other purposes. A few years ago, when we first started thinking about human exposure to plastics, we were like, “Oh, we should test some blood and just see what’s in there.” I tested a little bit of my blood and saw screamingly high levels of polyethylene. It just didn’t make sense. When I think about my diet, I’m not eating a lot of plastic-packaged foods. So that’s when we first started to think, “Okay, is there something else going on here with the analysis that we haven’t considered before?” We assessed how reliable current measures are for trying to find microplastics in blood. And what we found is that lipids and fats will give you a false positive for polyethylene. Lipids are made up of the same building blocks as polyethylene, so when we analyze them, they look identical in our analysis instrument. This means that we can mistake a signal from a lipid for polyethylene if we don’t look at the data carefully.
e360: In a paper you published last year you found that 18 previous studies on microplastics in human blood had this issue. Rauert: We were putting [the study] out there to say that you need to think about the data that’s coming out of your instrument, because there’s potential that these lipids, these fats, will give you a false positive. To our knowledge, these previous studies didn’t know about this issue and haven’t considered it, and future studies really should. e360: Another challenge, you found, is that plastic is absolutely everywhere, including in lab equipment. Rauert: In a normal chemistry lab, you’re surrounded by plastics. You have plastic pipettes. You have plastic Petri dishes. Plastics are quite necessary. They can be sterile. They’re single use. They have their purpose, but it means that you’ve got the potential for a lot of plastics to be shedding and to be in the lab around you.
“If your sample has touched plastic — for instance, a urine sample stored in plastic — there’s a potential for contamination.”
We’re talking about very small particles and fibers. You can’t see them — that’s how small — and they’re always in the air around us. If you’re not conscious of this, these small particles and fibers can be accidentally falling into your sample. Or if your sample has touched plastic — for instance, a urine sample that’s stored in plastic — there’s a potential for some of the plastic to come off, which can contaminate your sample. e360: You overhauled your lab to get rid of plastic contamination. What was involved? Rauert: We worked with an architect, and we built the lab pretty much from scratch. The first thing we had to work out is what to build the lab out of. We tested about 30 different construction materials trying to find some that didn’t contain plastics, but also didn’t contain plastic [additives] such as phthalates, but we couldn’t find any. Everything had either plastics or phthalates in them. We can’t have any wood or cardboard in the lab. It can get mold. It can get bacteria. So we ended up going with stainless steel. It was the only way to not have any plastics. Even when you put a glass panel in the window, you have silicon holding the glass in. We tested all these different brands of silicon to try to find ones that had low levels of phthalates. It was a crazy amount of detail that we went to, but it was really worth it. We ended up with three interconnected rooms, and they’re all positive pressure. The idea is that when you open the door, it pushes contamination out rather than bringing it in with you. And then when we commissioned the lab, the first thing we did was put background samplers in there to see what was in the air. In the lab, the plastics and the phthalates are about a hundred times lower than in our normal lab.
The plastics-free lab Cassandra Rauert and colleagues designed at the University of Queensland. The University of Queensland
e360: Is it a little bit disturbing to consider that plastics are so ubiquitous that you have to build a clean room from the ground up just to be able to study them? Rauert: It’s definitely made me think about my house a lot and all of the plastic consumer products that I have, and all the plastic stuff I have in my kitchen, which I have now been exchanging for metal and wood. You really don’t realize how much plastics you use in your everyday life until you start purposely looking for it. It’s just a given. You just grow up with it. e360: As far as we know, how does plastic typically enter our bodies? Rauert: We do know that, in terms of what’s in the air around us, we have higher concentrations inside our houses. We know a lot of these [plastic additives] end up in the dust in your house, so absolutely vacuuming more often is a great way to get rid of these. e360: And what are the biggest sources of plastic in your home? Rauert: We’ve been looking at residential balconies, and we’re seeing high concentrations of [particles from] tires [which are made with synthetic polymers]. There’s a potential for tire [particles] to be getting into your house dust. We still don’t have huge amounts of information on that.
“If we are inhaling [plastic] fibers, do we just cough them up again, or can they actually get deeper into our lungs?”
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