In this case, the lab gloves are shedding materials that superficially resemble microplastics under a microscope but aren't actually microplastics. (I was concerned about that at first too because of the overlap between food service gloves and lab gloves!)

What are negative consequences attributed to have microplastics, and have to the compare to the risks associated with say drinking alcohol?

Is that finding robust under the possibility that the microplastics in the sample were introduced by the gloves used to handle the sample? One could, for example, explain that result with a hypothesis that the reason there's more microplastics in brain tissue is that they had more hands touch them with lab gloves than the liver and kidney samples.

It's the finding that brain tissue seems to concentrate microplastics at a much higher rate than other tissue in the body

If I remember correctly, the method they used to detect microplastics, which involves pyrolysis, gives much the same result for lipids (which brain tissue has a lot of) as pure hydrocarbon plastics like PE and PP, because they all feature relatively long hydrocarbon chains and the pyrolysis products will contain the same short-chain hydrocarbons.

I find it concerning that there seems to be such a concerted effort to downplay the significance of that finding

There is nothing to be concerned about. This is just the (re)discovery of basic chemistry and the natural response to misguided alarmism.

Before I ask, I want to disavow any suspicions people may have that I'm a shill for asking, so to borrow from a related subject: I hate the idea of bioaccumulative toxins. 3M and DuPont executives behind not just the original per- and polyfluorinated chemicals, but the replacements like GenX that are basically a nearly identical molecule with just a few atoms changed belong in prison, not in boardrooms, to say nothing of all the people complicit in distributing them in consumer products.

I may have taken the bait from the plastics industry on this one, I really don't know, but wasn't one of the pushbacks something along the lines of "well yes, there are microplastics, and yes, they do accumulate in the body, but you shouldn't worry about it - there isn't really any evidence of systemic harm being caused by them"?

Do you know if there are studies that do show evidence of harm from microplastic accumulation? It sounds really bad at face value, but I still want good, hard evidence before I'm ready to add an industry to my personal list of perpetrators of crimes against humanity.

Similar issues plagued tests of iron concentration in seawater. Sample collection was contaminating the samples for years, until a procedure to collect a non-contaminated sample was developed by John Martin. He was able to finally figure out that actually most ocean water was iron deficient (that is to say: iron was the limiting factor in phytoplankton growth). Testing for environmental contaminants, especially in things that are commonly used by human civilization is really tricky.

If microplastics are everywhere in flesh/brains/etc., how do you construct a blank without them? Isn't that the very issue here?