[AyanamiKaine]

Microplastics have always fascinated me, because I keep seeing article after article about how much microplastic exists around us, but far less strong evidence about its actual effects. That is not to say there are no effects, of course. Maybe we just have not found them yet.

A friend of mine worked on her bachelor’s thesis about the effects of microplastics on the immune system, specifically T cells. Her result was that the microplastic particles she studied were too large to interact with T cells.

She probably will not publish this result because she thinks it is not interesting enough. Classic file-drawer problem in academic science.

While I encourage her to do it anyways as a negative results is also interesting but she wanted results that are worthing of headlines in magazines.

[legitster]

> She probably will not publish this result because she thinks it is not interesting enough. Classic file-drawer problem in academic science.

It's truly insane that everyone in the academic class understands the fundamental problems of herding and sampling bias and yet every incentive is in place to do this.

[etrautmann]

Having lived this reality, people respond to incentives. Your have to very fundamentally re-architect the incentives and career progression in academia to make publication of null results more common. The other side of this is reducing the time and hassle of publication. Right now I’m unlikely to battle for 1.5-3 years to get something through peer review for a result that nobody will find interesting.

[cortesoft]

I think this is exactly what the person you are replying to is saying; everyone knows it, but the people in charge of setting up the incentives still don’t seem interested in changing the incentives.

[a_bonobo]

Yes, this has been my experience in the Australian academic system as well: everything is broken and nobody with the power to change it, cares.

China seems to make some strides for their own academics, thinking loudly about moving away from glam publications as career incentives: https://www.ft.com/content/64a811f1-b132-4211-8a8c-2252cf964...

It's supposedly about the worry of leaking state secrets, but it will have positive outcomes apart from that.

[ransom1538]

More devastating, the null results we would be really valuable with machines that can think. (Not humans that don't give a shit).

[anonym29]

>people respond to incentives

Careful, you're starting to sound dangerously close to an Austrian economist!

[ ;) ]

[pfdietz]

"Show me the incentive and I'll show you the outcome." -- Charlie Munger

[dlcarrier]

It's worse than that.

It wouldn't take much time for her to publish it then move on to something that looks good on a resumé, but it could actively work against her if she published something that doesn't substantiate the status quo. If you get labeled a science denier, because you published a negative result for a politically-charged subject, even when you agree with the overall cause, it'll be nearly impossible to get a job in the field, even with a flawless resumé.

[bee_rider]

I’m not sure who the academic class is (are grad students, postdocs, and tenured professors really in the same class?).

Anyway, the people setting the incentives are the ones handing out the grants.

[zug_zug]

> but far less strong evidence about its actual effects.

Yeah, but we shouldn't take absence of evidence as evidence of absence. The fact is that it's just really really hard to establish a causal relationship, even if it's there, because of all the cofounders. Heck even if you constructed a study with a known poison, like lead, and you might not see the results in a single study. You could give 50 participants water with flint levels of lead in it for a month, and you might not get scientifically significant result just due to the wide variance in a population.

Or another example is just thinking how hard it would be construct a study with a control, when every single construction material has plastics in it and they are floating in the air around us all the time (as mentioned in the article). Could it affect mental or reproductive wellbeing? Certainly. Can we construct a study to establish either way? Not easily.

And one of the plasticizers they talk about, pthalates, are known to be endocrine disruptors (i.e. mess with hormones).

[marcosdumay]

> Yeah, but we shouldn't take absence of evidence as evidence of absence.

That's wrong. Yes, we should.

Each and every study that doesn't find evidence for what they are looking for is evidence for its absence.

[unparagoned]

That’s wrong. Only if the studies are powerful enough and are looking at the right stuff can you make any reasonable conclusions.

If the studies are powerful enough then that absolutely isn’t evidence of absence at all.

[Xirdus]

Evidence can be strong or weak. Every positive study result is evidence of presence, usually strong evidence. Every negative study result is evidence of absence, usually very weak evidence.

[rTX5CMRXIfFG]

And yet, people can be extremely vigilant about a positive correlation when it doesn’t fit their personal agenda, going as far as questioning methodology in even the least pragmatic ways possible; or, become accepting of the absence of evidence as evidence of absence when weak/no correlation is convenient to their own biases.

[Xirdus]

I'd say it's very sensible to assume absence up front before there's convincing evidence of presence. Sure, personal biases influence our evidence thresholds a lot, and often people demand unfair rigor that cannot be practically met. But the opposite is also true - sometimes people will believe in presence with zero evidence if they like it enough. The latter is far, far more dangerous than the former.

[zug_zug]

That's not right, a negative study often still can give evidence that something is true, but it just didn't meet the p=.05 threshold.

[Xirdus]

p<=0.05 is so easy to achieve for actual positive results (just increase sample size) that I don't think it's productive to treat any result with p>0.05 as positive evidence for any purpose other than deciding to rerun the study with a bigger sample size.

[customguy]

Absence in the results of whatever we measured for. Just take the sheer hybris of "junk DNA": We don't understand this, so it's probably junk.

[Xirdus]

Note that we didn't call it junk DNA until we learned a whole lot about how DNA works and formulated a theory in which junk DNA doesn't do anything for good reasons. In a way, lack of understanding prevented us from calling it junk DNA earlier.

Of course it's still possible for the theory to be wrong and the so-called junk DNA being actually important. It's only junk according to our classical, non-quantum and non-relativistic theory of junkiness.

[customguy]

> Note that we didn't call it junk DNA until we learned a whole lot about how DNA works and formulated a theory in which junk DNA doesn't do anything for good reasons. In a way, lack of understanding prevented us from calling it junk DNA earlier.

Thanks for noting that, you totally caught me since I actually don't even really remember the stuff I read about that, which was probably false to begin with: https://en.wikipedia.org/wiki/Junk_DNA#Junk_DNA_and_non-codi...

So upon further consideration, since I don't really know anything about the research of the impact of microplastics, I'll apologize for speaking of scientific hybris so flimsily, that was really the hybris of the layman (me).

I'm still skeptical, not of science but of the harmlessness of microplastics. Not because of any evidence I have, but because it's just so us... this cycle of putting something everywhere before we even know it exists, finding out it exists, going "nahhh it's probably fine" for years, decades or centuries, and then "oh shit". Which I'll admit is not scientific and not really a useful contribution to this conversation, either :P

[app13]

I participated in research from 2017-2022 that found similar results regarding bio-interactions, generally.

Learned a lot about making microfludic flow cells at least

[jagged-chisel]

> ... too large to interact with T cells.

Also, unfortunately, a result that industry and the anti-regulation crowd will use to say microplastics are harmless.

[w10-1]

also, asbestos is too small to interact with T-cells, so it must be safe.

[nostrademons]

It's not really analogous. One of the hypothesized ways that microplastics are harmful is that they disrupt the immune system; there has been evidence found of this in bivalves. Another is that they cause inflammation, which is also mediated by T-cells. A null result on the impact of microplastics on human T-cells is directly relevant to these hypotheses.

The mechanism of harm for asbestos is known to be that the fibers enter the lungs and can't be expelled, eventually leading to cancer. Its interaction with T-cells is quite irrelevant there.

[pfdietz]

I understand asbestos fibers literally get tangled with DNA, and that this can be demonstrated in vitro.

[Supermancho]

>>>> ... too large to interact with T cells.

>>> Also, unfortunately, a result that industry and the anti-regulation crowd will use to say microplastics are harmless.

>> also, asbestos is too small to interact with T-cells, so it must be safe.

> It's not really analogous.

Ironically, this is missing the point. They were commenting on flawed reasoning. This shouldn't need to be spelled out, as it's part of the conversation context.

Sometimes "dunking" comments are a variation on https://www.instagram.com/p/DY2DRKDhqaa - where everyone is arguing about who is wrong, because they aren't treating it like a conversation.

[NoImmatureAdHom]

She should at least put it on https://www.biorxiv.org/ !

[guelo]

One thing I learned from this article is that even though the plastic particles themselves are poorly studied the chemical additives, such as phthalates and bisphenols, are very well studied and are known toxins. So even if the tiniest plastic particles (smaller than the ones your friend studied, that can cross from your gut into your bloodstream), don't affect your health at all, you still don't want to ingest these things because of the other chemicals in them.

[codybontecou]

Can microplastics never get small enough to interact with T cells?

[Borg3]

Once microplastics fall apart futher, to nano-plastic, it will start to get absorbed by T cells because they want to destroy any invaders. Once absorbed, T-Cell start to produce H2O2 to destroy anything they absorbed. Unfortunately, plastics are mostly chemically neutral and so, it cannot be destroyed like that. T-Cells produce more H2O2, eventually it leaks outside and start inflamation of surrunding tissue. There is research about it.

[dzhiurgis]

AKA nanoplastic-induced oxidative stress, but it's actually macrophages (and neutrophils), not T-cells.

The reason this is problem is because cells can never destroy nano-plastic so they keep self destroying forever (chronic inflammation).

I still have my doubts about actual scale of this, especially how we still haven't solved pm2.5 pollution or even asbestos and heavy metals. And then there's PFAS, VOCs, Phthalates and Bisphenols. There's insane amounts of benzene in gas stations and traffic jam, yet no one really gives a fuck (until there's like a ppm in a sunscreen lol).

You are most likely to inhale it due to plastic abundance in environment, just like thousands of other things. It doesn't even have ICD yet. Ingested microplastic unlikely to breakdown while it travels thru your body.

p.s. my partner de-plastified a lot of my life (thru a lot of opposition of me) to the point where a lot of plastic objects feel gross now.

[Terr_]

> macrophages

Right, and when it comes to "what happens when the macrophage can't destroy what it engulfed", we can probably learn a lot from parallel work studying tattoos, where the ink-particles are similarly "attacked".

Plus it's a lot easier to create studies or even just observe the cells in question.

[Shog9]

Link to that research, please. It would add meaningfully to this discussion.

[BobbyTables2]

So microplastics are indeed harmless!

(/s)

Too bad common discourse is too distracted to consider nanoplastics…

By the time the public tires of microplastics debates, they’ll be in no mood to relitigate nanoplastics

[Retric]

There’s a transition point where things stop being micro plastics, then nano plastics, and become specific chemicals.

Those molecules may be toxic but the interactions are distinct from microplastics or nano plastics.

[tristor]

Unknown to me, but something useful to know is that there is something smaller than microplastics called nanoplastics. The distinguishing factor is that nanoplastics are particles smaller than 1 micron, while microplastics are particles between 1 micron and around 5 millimeters. As your other respondent notes, at some point you're talking about single molecules. As plastics is an entire category and not a single thing, there's no one size where that happens, but some polymers have chains that are as little as 0.01 (1/100th of a) micron in size.

As far as I am aware, we have yet to have effective, replicable research on what if any biointeractions exist with nanoplastic particles, including single polymer chains.

[cwillu]

> 5 millimeters

TIL thermoplastic pellets are “microplastics” :)

[tristor]

I don't make the definition

[schiffern]

I expect many researchers are using fresh lab-made microplastics, which are indeed mostly harmless. However part of the problem is that real-world plastics are chemical sponges that absorb toxins (heavy metals, PCBs, etc) from the environment and deliver them in a concentrated dose into the body.

https://www.eurekalert.org/news-releases/923529

[gruez]

>However part of the problem is that real-world plastics are chemical sponges that absorb toxins (heavy metals, PCBs, etc) from the environment and deliver them in a concentrated dose into the body.

>https://www.eurekalert.org/news-releases/923529

But your linked study only talks about biofilms and E.coli?

[magicalist]

> Her result was that the microplastic particles she studied were too large to interact with T cells.

Her "result" of what? Was there an actual experiment and what was its scope or was this by surveying literature?

Microplastics are of a pretty large range of size, and then there are nanoplastics below that.

I'm also not an expert, but a quick search shows a number of results of microplastics affecting T cells, some directly and some in terms of immune signaling, so this negative result doesn't seem that definitive.

(as usual, the difficulty is in teasing out in vivo effects)

[vitally3643]

I'm not an expert but I'm going to condescend about an expert's "results" anyway.

Very informative, thank you for your comment. You have truly contributed to the conversation. Good job.

[magicalist]

> I'm not an expert but I'm going to condescend about an expert's "results" anyway.

I mean it's a detail free second hand anecdote about someone's informal discussion of their bachelor's thesis. Which part of that is the basis of a good scientific conversation?