One thing I learned from this article is that even though the plastic particles themselves are poorly studied the chemical additives, such as phthalates and bisphenols, are very well studied and are known toxins. So even if the tiniest plastic particles (smaller than the ones your friend studied, that can cross from your gut into your bloodstream), don't affect your health at all, you still don't want to ingest these things because of the other chemicals in them.