Recent studies have shown that microfibers can end up in the stomachs of marine animals, including seafood, like oysters. When you eat an oyster stuffed with the fibers you get a gut full too.
Ever heard of the Great Pacific Garbage Patch? The debris consists of small plastic particles. The flotilla ranges in size from 270,000 sq miles (the size of Texas) to 5,800,000 sq miles or "twice the size of the continental United States."
But the crap in the Pacific Patch is too hefty to end up inside a tuna. And you were sweating a nuke war...