Mhm and microplastics have yet to prove themselves to be small as predicted. They will get to that point if not already. It is more about the smallest the polymers can theoretically get. DNA makes errors just cause of age it doesn't need much help for damage.
It certainly seems like a potential problem. I imagine there are biologists keeping an eye on less complicated organisms so that we at least know what to expect.
We really aren't more complicated than most mammals and we are kinda all getting poisoned at the same rates. We kinda need to eat those critters and get most of our microplastics from the food chain. The amounts in the body are only gonna increase. A bit too quickly for nature's liking given scale.