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.

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.

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