Particles less than 10 micrometers are most likely to be absorbed across the GI epithelium.

“if you're encountering a microplastic that's less than 2.5 microns you could absorb it both in your gut or via your lungs”

“and again the Plastics have a very difficult time crossing the GI epithelium um so when you look at animal studies we would see that um it's about. 3% maybe with a ceiling of about 1.7% of microplastics have the capacity to be absorbed across uh the GI epithelium and of course it's heavily heavily size dependent so it's the particles that are going to be less than 10 microns”

“the pulmonary epithelium requires them to be smaller than 2.5 uh microns um”