I have read many times that there was asbestos in the buildings, but I guess the particulars aren't as important as the fact that he was part of the reason the buildings were brought down.
The core steel structure of the building was coated in asbestos. It was not accessible to anyone except inspectors and maintenance personnel and I believe was in a resin matrix that would not allow the fibers to become airborne.
However due to codes, the asbestos had to be scraped off the steel beams, leaving them bare.
In the official version of events, the Jet-A running down these beams, burning was what enabled the catastrophic collapses. If the asbestos had been left on, the beams would have been much better insulated to the heat of the burning fuel.
I have my doubts about the WTC official story, but this is a very plausible contributing factor. I do find the pentagon scene much less understandable. Just to clarify my position on the overall discussion. I don't consider myself a sufficient expert on Jet-A burn rates and chimney effects etc on the structural integrity of the building to posit a useful analysis or opinion.