Did Morgulduin pollute the lower Anduin ?

[Inziladun]

Originally Posted by Morthoron

Orcs gotta drink, don't they? Perhaps they had a higher tolerance for e-coli, dysentery, cholera and other waterborne diseases. Perhaps Tolkien was thinking of the Thames, which supposedly looked black and sorcerous until health reforms reduced dumping of human waste, animal offal and manufacturing slag over the last 100 years:

That sounds more like what Sharkey's Men were trying to do in the Shire.

'They're always a-hammering and a-letting out a smoke and a stench, and there isn't no peace even at night in Hobbiton. And they pour out filth a purpose; they've fouled all the lower Water, and it's getting down into Brandywine.'

The Scouring of the Shire

What was going on in Morgul looks like something different, more of a spritual decay and corruption rather than a physical pollutant.