I'll explore a few locations in the US over the summer and consider swimming in some rivers. How can I assess the water pollution in rivers in the US, preferably before going to the location of interest? Ideally I'd like to input the location (e.g.) and have a clear answer: polluted/non-polluted.
There does seem to be a product category for exactly this.
Notice the section,
"Recommended Tests for Open Water Swimming:" / then / "field test kits which provide instant results (these are suitable for fresh water only and are screening tests)" ...