Even if you do eat them, there's no evidence (or I suppose I should say no evidence yet) of microplastics being harmful when ingested. Nanoplastics, on the other hand, have been found to impact animal embryos and cells grown in labs.
A problem with microplastics is that they come bundled with numerous xenoestrogens and other harmful contaminants. This too is what makes them very harmful, especially when conceiving a child.
Granted, if one uses an indoor clothes dryer, some could disperse into the air which one can then breathe in.
I understand that our culture has done a major disservice to cotton.