[peterwwillis]

They say "much" ("a large amount") of it ends up in waterways, which is substantiated. As one tiny example, look at Mr. Trashwheel. It collects ten tons of trash on a rainy day. If you don't believe me, here is a sped-up video of it collecting plastic, styrofoam, and other single-use trash items[1].

And here are statistics on the trash gathered[2]. 649,236 plastic bags, 880,646 plastic bottles, and plenty of other miscellaneous plastic pieces. All of this disrupts natural ecosystems, and is ingested by animals who then get sick, and later gets into us as microplastics when we ingest the animals. This is the reason nearly all of our food and beverages contain microplastics.

If this doesn't seem that bad, the above example is from a single stream into a single harbor in a single city. Now imagine the national scale.

But plastic isn't the only pollutant of US waterways. Bacterial matter, nutrient excess, and industrial toxins regularly find their way through the watershed into main waterways, affecting marine life as well as humans. Waterway pollution is a big issue in the US.

[1] https://www.youtube.com/watch?time_continue=19&v=GgnTBxSMo3g [2] http://blogs.ubalt.edu/ubmag/the-problem-of-plastics/