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.

Hmm, interesting. Maybe I’m being dense here. Let’s say that the teabag is that 7.14g of salt you mentioned - a chunk of salt, let’s say. They either A) try to dissolve 300 of those (each 7.14g) in 600 ml of water or B) they dissolve 1 chunk in 350 ml water. Like you said, they either report A) 3.57 g/ml or B) 0.204 g/ml.

I’m really just saying that either way, it’s still 7.14 g/chunk. Quite a lot of salt/particles per chunk/teabag.

I think maybe I don’t have an issue with them reporting the concentration because I didn’t interpret them as saying that they were saying there’s a billion particles per ml of a regular cup of brewed tea - it was always apparent to me that it was about the number of particles in a teabag (in this case, half a teabag with just a ml volume). I think we’re ultimately just arguing clarity of their language.

Effectively, they are reporting effectively particles per half a teabag, right? So the numbers really should be double, is that what you’re saying?

As for the massively different concern, agreed, but maybe in a different way that doesn’t change my conclusions. Let me illustrate. My question to you is, if you dissolve (insert anything here) in a smaller volume of water, would you expect to get out more or less of the dissolved particles than if you were to dissolve the same thing in a larger volume?

My answer is less. The reason is because there are fewer water molecules to pull away particles when there’s a smaller volume of water. I suspect that their methodology underestimates the amount of plastic particles than if they were to use a very large chamber to brew 1 teabag to 350 ml water.

A saw another comment you made - Maybe you think that teabags are colliding with one another, but they are all spinning in the same direction in a beaker with a magnetic stirrer, so there’s not really all that much agitation.

Thanks for the clarification of the concerns.

For concentration, it’s not typical for 2 reasons. 1) their instrument may have a detection limit, so if they brewed 1 teabag per 300 ml, they’d have to concentrate it in another way. 2) they’re pooling a batch of teabags, which gives an average, reducing variability teabag to teabag.

Besides mimicking the exact real world scenarios, I think I don’t get what the issue is with concentration. If you boil something that’s dissolvable in a larger volume of water, you’ll typically get out more “pieces” than if you were to do it in a smaller volume. In the experiment, if anything, they may be underestimating the particle release.

For mixing, this method is super standard in the lab. I think that when the methods say 750 RPM, they’re talking about the speed of the stir bar - most definitely with the mass of the 300 wet teabags in that volume, the whole mixture isn’t actually going to get to 750 RPM. If it did, everything would spill out the side, over the top lol

Fair point about incubation time. Do we have a standard for how long people keep their teabags in hot water? I usually don’t take it out of the container when drinking it to go, and if it sits over a few hours and there’s stuff left over, I will usually finish the drink.

In any case, what’s the lowest amount of plastic microparticles we’re okay with? Above, the other commenter said 20k after every generous interpretation moving the number lower. Isn’t that still an insane amount for one drink?

I think my issue with the commenter’s first comment is that they call for the paper’s retraction over what is completely standard in lab science.

Right. You still drink 300-350 ml per cup. It doesn’t matter if you did 1 teabag per 300 ml or 300 teabags per 300 ml. In the first instance, you would have to measure 300 ml to get the X particles per cup. In the second instance, you can get the X particles per ml which is effectively per cup, or more accordingly, per teabag. It’s the same. Please correct me if I’m wrong, but I think your math of 23k particles per teabag is not mathing.

Also, usually you don’t measure 1 teabag because of individual variability, so what they are doing is getting the average amount of particles from those 300 teabags. Much more accurate.

They likely are using a magnetic stir bar. 750 RPM will not virtually blend it. This video shows it going at 3000 RPM max for reference. (https://youtu.be/fzzV75aMM1c) In a large container, the water at the bottom will be swirling faster than the water at the top. And also, 95 C will not be at an active boil - that’s at 100 C. It suggests to me that they boiled water, then poured it into the teabag beaker.

I think that maybe you haven’t worked in a lab before, so it seems like the methodology isn’t right, but as a scientist, this passes the sniff test for me. Honestly, this part isn’t even the novel part of their study - the interesting part is that they found that intestinal cells took up the particles, but I digress.

“The study shows that, when brewing tea, polypropylene releases approximately 1.2 billion particles per milliliter, with an average size of 136.7 nanometres; cellulose releases about 135 million particles per milliliter, with an average size of 244 nanometres; while nylon-6 releases 8.18 million particles per milliliter, with an average size of 138.4 nanometres.”

What do you mean no it doesn’t?

So if you extrapolate the data, that’s 1 teabag per 2 ml water. Let’s be generous and say that 1 ml is about what you’d get in a cup of tea. That’s 8.18 million to 1.2 billion particles per teabag depending on the type. Let’s be generous and cut that in half due to the RPM of stirring. Maybe cut that in half again for that unspecified amount of time. Hell, let’s cut it in half again because maybe you brew at lower than 95 C. On the low end, we still have 1 million plastic microparticles per teabag. That’s insane.

That’s what it says in the article.

“Moreover, one arm of the administration cannot sue another, so the military cannot sue the EPA, and the case would never end up in court where the Chevron decision would come into play, said Walter Mugdan, a former EPA Superfund director. Instead, it would be resolved internally by a presidential administration instead of the judiciary.”

But fighting soldiers versus fighting civilians is completely different, isn’t it? Isn’t that why we’re not really cool with the conflict in Gaza?