[maltyr]

A quick search led me to this review, which has a number of studies linked in references, including a few that studied humans.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9885170/

Quote from the abstract: The direct consequences of MPs and NPs on the thyroid, testis, and ovaries are documented. Still, studies need to be carried out to identify the direct effects of MPs and NPs on the hypothalamus, pituitary, and adrenal glands.

[simonh]

Disappointingly nothing in that study relates these health impacts to known levels of microplastics in humans. That means there’s no way to tell, from that study, if the levels of microplastics to be found in you and me are likely to have material impact.

I definitely feel we should be more serious about reducing use of plastics, especially for uses likely to contribute to microplastic levels, but it’s going to be hard to convincingly make that case without quantifying these risks in relation to actual human microplastics levels.

[londons_explore]

One doesn't reduce the use of plastics without using something else as a replacement.

If we replace all plastic cups with glass cups, might we get micro-glass inside ourselves instead?

Glass, mostly silicon dioxide, might sound harmless, but glass can chip off in microscopic sharp fragments (think fiberglass dust - which some suggest might be as bad as asbestos). Glass also slightly dissolves in water (this is how glasses start to look frosty after enough dishwashing - they're dissolving), and slightly evaporates (everything has a vapour pressure!). And obviously the glass isn't pure - there can be all kinds of deliberate and accidental additives.

Am I worried about glass? No. But it seems naive to wholesale replace plastic with something else until there is a decent understanding of the replacement.