[fc417fc802]

> It seems to me most scientists in the field are terrified of microplastics

Got anything you can point to? I haven't looked for a while but last time I did the evidence of harm appeared quite minimal. I recall that it was quite toxic in aquatic environments that had already been contaminated with (previously mostly harmless) low levels of heavy metals.

PTFE is similar in that it too hangs around in the environment for ages which is certainly a cause for concern. Yet it seems to be difficult to track down any known concrete negative effects. (If you are aware of any I would be interested in learning about them.)

[tw04]

Sure, here’s one that’s particularly disturbing and I can’t imagine long term is classified as benign.

https://www.npr.org/sections/health-shots/2024/05/22/1252831...

[fc417fc802]

I think this still fits the pattern I was referring to. Observation of a concerning trend but minimal or no direct evidence of harm. In this case accumulation in reproductive organs.

That article cites (https://pmc.ncbi.nlm.nih.gov/articles/PMC9134445).

> Animal studies have shown exposure to microplastics can impact sperm quality and male fertility,

That paper covers numerous aspects. Regarding specifically reproductive harm in mammals, it in turn cites numerous other studies at which point it becomes rather time consuming for me to get up to speed in the nuances of a field that I'm not intimately familiar with.

Having checked at least a few of the relevant citations, it looks like (most of?) the research in animal models involves short term acute rather than long term low level exposure. Not being an expert in this specific area I can't readily assess the quality or applicability of such studies. At least from what I looked through just now I'm not at all convinced that what the current animal studies are showing is (necessarily) directly relevant to low level environmental exposure.

https://pubmed.ncbi.nlm.nih.gov/30176444/

> exposed to 5 μm polystyrene MP at the concentrations of 100 (approximately 1.456 × 106 particles/L) and 1000 μg/L (approximately 1.456 × 107 particles/L) for the toxicological experiment.

https://pubmed.ncbi.nlm.nih.gov/32659591/

> the 0.5 μm, 4 μm, 10 μm polystyrene microplastics (PS-MPs) treatment groups were given 100 μL PS-MPs (10 mg/mL) by oral gavage once a day.

From my perspective there are a couple huge red flags here, and they seem to be present in all the studies I checked just now. I didn't immediately see comparisons of these protocols to the environmental conditions in the world at large (either current or predicted). Neither did I immediately see quantification of the degree and nature of the observed tissue accumulation in comparison to that observed in tissue samples collected in the wild. The latter is of particular concern because these accumulations in the laboratory happened very rapidly (over the course of a few weeks) in the face of acute exposure and impacts were then immediately measured. That doesn't really resemble what's going on in the world at large.

It is of course entirely possible that I missed something when quickly looking over studies that are outside my area of expertise. Apologies if so.

Lest it seem to you that I'm being overly pedantic here consider the difference in outcome for chlorine exposure between long term low level (ie tap water) and short term acute (ie poisoning).