Thanks for the replies. For the record, Pittsburgh is no longer the smokey city it once was - we have daylight once more.
Now I'll grant that some of the 'iron work' was of the cottage industry type. But I can't see this being the source of the 'forest of spears' and weaponry (forgive me; I'm without a book at the moment) that appears in battle such as when Turgon breaks the leaguer of Gondolin. Or when the Númenóreans march on Middle Earth.
I think that what makes fantasy, well, fantasy is the lack of waste products.
As a child, I read Edgar Rice Burrough's Tarzan books. I tried to live like Tarzan (though I had to go home at night, and avoided all girls, even those named Jane), and had some limited success with mimicking the ape man's arboreal exploits. One thing that always evaded my best efforts was the ability to track my cousins and other wild animals by their 'spore,' or scent. Why, Tarzan could, with a few whiffs, tell what animal went where and when. Me, not so much, no matter how closely I placed my nose to the dirt.
Later it dawned on me what I was missing, besides an acute sense of smell and the ability to speak and read French. The animals and people in Tarzan's world reeked!
They do in Middle Earth as well, but because it's fantasy, we choose to ignore it like the piles of slag and slurry-filled streams beside the armories.