I asked a question about jettisoned rocket parts residing in the ocean, and tagged it with waste, but this tag was removed in an edit, presumably because most other instances of this tag relate waste products from humans or spacecraft in space, so it wasn't considered a good fit.
That got me thinking that perhaps a pollution tag would be useful, and appropriate for my question.
I don't have the rep to create tags, so I'll leave it up to the community to decide.