I agree with Forrest's reply and would like to add the following:
: Furthermore, the Trow used iron in great amounts, but so
: do the armies of the west.
: By your reasoning, every river in the west should also be
: 'poisoned,' as well, because the living use iron, too.
Iron was the gift of the Trow granted by Nyx. They used iron intensively and almost exclusively in their buildings, monuments and armaments. The forge of the Trow, Tharsis is a volcano, which suggests monumental quantities of the element being smelted, worked into tools and used to erecty vast constructions.
That which was unusable or spent must surely have been discarded in rivers and the surrounding wasteland as Trow don't strike me as proprietors of any sort of recycling facilities.
The quantity used by the light would not have nearly rivalled the fixation their towering neighbours had for it. That is even if they were able to get their hands on it. The Trow believed it was theirs alone and would have made it very difficult for a lesser race to attain it. Remembering that the Trow were not as isolated as they became after TFL.
Also, the Trow had been using iron since before humans had even come into existence. What's more, the rusty rivers of blood are only seen in and around Rhi'anon, the historical centre of Trow civilisation where the bulk of temples and buildings would have been.
I do not see how the humans could have used iron enough for it to pollute their rivers and kingdoms to the extent which it has poisoned the Trow domain.
