Extreme confidence is probably a mistake. Chronic diseases are rampant and we don't have good answers for what the causes are.
Have we been using the same exact compounds and processes and habits for 40 years? Every new advance is a chance for some new fuck up, and it takes time to realize it, if we ever do.
There's a huge range of possibilities between arsenic and "minor harm."
We have decent reason to believe they are active in the endocrine system, and pretty good reason to believe there are population-level endocrine issues (obesity and fertility).
Given that these plastics seem to accrue intergenerationally (i.e. babies are being born "poisoned" by them), an apparently minor, apparently not-very-acute issue could actually end up being a much, much, much bigger problem than any of the examples you listed.
That's incorrect, after invention of a leaded fuel, the first health concerns were raised in 1 or 2 years of production, and major heath investigation happened in 4 years time. We just lobbied (bribed) our way to continue using it regardless for half a century. And even a century later leaded fuel is widely used even in the USA, and probably even worse in other countries.
You're totally right, my choice of language should have been better. Thanks for the correction!
Is the situation all that different for plastics? I'm not sure. We've been running health studies on them for a while and the harmful effects of BPA, Teflon, PFAS, and the androgenic affects of most polymers are pretty well known at this point.
My point is mainly that how long we've been using something is not a great way to determine safety.
Your argument might have made sense if excess consumption of carbohydrate, saturated fat, and other nutrition deficient foods did not skyrocket over the same time frame.
This is a big part of the struggle with in vitro vs in vivo studies. We can have a repeatable result with in vitro effects, but can't confidently say what the macro effect will be. We might be able to say it doesn't "directly" cause none, some, or all of those, but we can't definitively say it doesn't contribute at all.
Personally I'm of the opinion that is evidence large scale studies are needed on live subjects. I'm not educated enough to know if that is feasible or reasonable, but I am confident you can't be "sure" until that is done.
There's effectively no way to test this with fully unadulterated control group. The entire planet more or less is covered in microplastics.
It's not clear how, even theoretically, you get better evidence than "this is what we see in vitro, and the effect seems analogous at population scale."
Sure, maybe there isn't, I can't argue that with my knowledge.
What I am confident on is there won't be significant societal change with that level of evidence. Most of those health issues have "easy" reasons they can be associated with (right or wrong), and it's going to be tough convincing people that in vitro effects are enough reason to significantly curtail (nevermind ban) plastics.
"Significant societal change" doesn't always have to come from getting masses of people onboard. It can also happen, and often does happen, by people entrusted with power to make decisions even in the absence of complete information.
One heuristic such a person might use would be, "gee, are we really going to take the position that if you pollute so quickly and so widespread that it becomes nearly impossible to demonstrate specific harm, that you can just keep on doing that?"
I mean, given we've shrouded almost every consumable item in them, for approximately 40 years (maybe more!) we can be whatever harm they do is minor.
Like, it's not carcinogenic. It's far below, say, asbestos. Or arsenic. Or thalidomide.
We can be extremely confident, whatever the effects of micro and nano plastics, they're not even close to those levels of danger