Summary
A new study from Spain’s Autonomous University of Barcelona reveals that tea bags made from nylon, polypropylene, and cellulose release billions of micro- and nanoplastic particles when steeped in boiling water.
These particles, which can enter human intestinal cells, may pose health risks, potentially affecting the digestive, respiratory, endocrine, and immune systems.
Researchers urge regulatory action to mitigate plastic contamination in food packaging.
Consumers are advised to use loose-leaf tea with stainless steel infusers or biodegradable tea bags to minimize exposure.
In a sense, but clarity of language can be the difference between accurate conclusions and misrepresentation. Just on data presentation alone, formal issuance of a correction is absolutely necessary.
Following on from that is where the issues with study design and methodology come in, and in my opinion they are both so flawed as to lead to spurious conclusions.
The other major problems I see so far:
as mentioned previously, their brewing methodology is so different from what would be done under normal conditions/at home that comparison between the two is meaningless. A good paper should discuss these differences and explain why some conclusions can still be drawn, but this one just makes a direct comparison.
the authors used empty mesh sleeves from an unnamed aliexpress vendor for their samples. We have no idea whether these sleeves are in use by any tea manufacturer, we don’t know anything about how they were made, and we don’t even know whether they were intended for food usage.
one of the three samples produced only cellulose particles, which a) isn’t a plastic and b) is a component of plant cell walls. I don’t know the cellulose particle concentration in a kale smoothie, but I’m certain that it’s higher. And yet the authors still just report this figure alongside the others.
Ultimately, the only thing this paper demonstrates is that certain types of thin-fibre plastic will, when handled roughly, shed nanoparticles. This isn’t a new conclusion, and doesn’t provide us with anything actionable with respect to our tea drinking habits.
I’ve mentioned it before in another comment, but this conclusion about plastic microparticles is a very minor part of their paper - it has already been established by Hernandez et al in 2019 (Environ Sci Technol) that billions of particles were released from plastic teabags, and another study by Banaei et al from the same lab as the OP posted study in 2023 (J Haz Mat) adapted/refined the method to try to mimic traditional tea preparation. That method section may give you a bit more insight as to what exactly they did and why, e.g. they say “The stirring speed was gradually augmented since the weight of the teabags slowed down the stirring speed…” And “the teabags were squeezed… eliminated… [And] the remaining solution was left to cool down on constant stirring…” I’d advise you to look at that paper - it might actually address your problem #1.
For #2, that’s fair. I think they had the details on the chemical composition of those (nylon-6), but they didn’t do any digging on if any manufacturers use them. I’m not exactly sure that’s in the scope of their study as they were just looking for any consumer teabags that could reasonably be used and consumed by people.
For #3, that’s also fair, and if you look at their data in the microscopy sections, it doesn’t look like cellulose gets taken up by the different cell lines. I think you can think of it as a control for plastic microparticles, but yeah, I guess they didn’t specify. That’s on them.
I think the novelty of this study isn’t the plastic particles per se but it is that they looked at the biological interaction between these particles and intestinal cells. There’s a lot there to discuss there in terms of the science and whether they could draw the conclusions they do. They did not show mechanism of action, such as what sorts of biology get affected after uptake of these particles (e.g. they could have done some transcription studies or looked at inflammatory markers or other transcription factors that get up/downregulated, or looked at what cytokines get secreted by ELISA or luminex), which all points to a severe limitation of the study. The uptake experiments also simply don’t have the right controls - they should have used other particles to see whether it’s simply a difference in cell uptake that’s independent of plastic. They could’ve also determined which organelle the particles were sequestered into rather than just saying it colocalized to the nucleus. And much more.
Long story short, from my perspective as a scientist, the issues you bring up are mostly trivial because it seems like there’s no standard protocol in place, and what they did was reasonable (also reproducible via stir bar and temp) even though it is not exactly how you’d brew tea at home. The study has its limitations, and much of it is on the biological side. I don’t have the expertise to comment much on their chemical analytical techniques.
You should know that critical methodological issues were reported with Hernandez, viz. they failed to discriminate particle identity. A recreation of their experiment demonstrated that the vast majority/virtually all of the particles were actually soluble oligomers that were subsequently crystallized by their preparation technique, i.e. not microplastics.
Your reading of their paper is extremely generous, but I’m not sure where you get the idea that analysis of the interaction between microplastics and endothelial cells is novel; the citations in this paper alone should be enough to tell you otherwise. The sole novelty of this paper is in drawing a link between existing studies on cell interaction and real-world situations, which is evident right from the title: “Teabag-derived micro/nanoplastics as a surrogate for real-life exposure scenarios”.
There may well be further room for experimentation in this arena, but this paper falls flat. Their methodology is so far off anything that could be described as “real-world” that it is spurious to draw any subsequent conclusions.
I would love to see the citations for the critical issues with Hernandez, if you have them. Do these also apply to this paper? Are you suggesting that what they have here are characterized improperly and aren’t actually plastic microparticles but rather oligomers?
As for the generous reading of the paper, you’ve gotten that wrong - I take issue with many parts of the biological aspects of the paper, but I still think that their method to extract microparticles passes muster. The application of those to intestinal cells is novel, but as I’ve mentioned, there are some issues there. I still find the paper to contribute to the literature, and I do not agree with your assessment that this paper ought to be retracted. We can agree to disagree, and only time and future citations will tell whether this paper was worthwhile.
Ok, it’s evident that reading papers of this sort is perhaps new-ish territory for you, but I sincerely commend your curiosity.
To whit: if you read the Results and Discussion section of Banaei, you will find at least 5 inline citations that refer to other papers that have investigated plastic microparticle interaction with intestinal cells going all the way back to 2004, and multiple other papers discussing microparticle interaction with other cell types. What this paper does is absolutely not novel. It isn’t necessarily worthless, but it is very much not new.
Per the methodological issues with Hernandez, there is a formalized process in scientific publishing for ensuring that critical discourse about a paper is presented alongside the original work. If you search for Hernandez (or any other paper) in PubMed and scroll down past the abstract, you’ll find related articles. If there are any formal comments/critiques/corrections, those will be listed first with a different subheading.