My personal, extremely unprofessional hypothesis on this is that it is at least in some part due to inhaling basically aerosolized depleted uranium, or taking basically microscopic shrapnel from rounds on target nearby.
A 10s, M1A1s, Bradleys, many different combat vehicles were using DU in some form or another, if not for the first time, certainly for the first time at such a large scale.
DU is a wonderful kind of hell material that can either partially 'moltenify' or splinter and shatter depending on its velocity and angle of impact with whichever material, to put it in very over simplistic terms.
You also basically cannot metabolize it out, its stuck in you forever.
Of course I am not a biologist or materials science expert, there was a ton of other insane shit going on as well.
I can't imagine breathing anywhere near hundreds of flaming oil wells is good for your health either.
EDIT: People do not widely know that breathing in the smoke from a wood bon fire for 30 minutes is something like the equivalent of smoking a few packs of cigarettes in terms of carcinogen exposure, scale that up to 100s petroleum wells burning for weeks or months.
And then there is Wooly Pete, White Phosphorus... that shit is extremely bad to be in close proximity to.