No, I don’t have any hard evidence to back up that suspicion, but I feel pretty safe concluding that Christe Todd Whitman is lying when she claims nobody knew how dangerous the air was in Lower Manhattan 15 years ago. The reason is asbestos.
I remember being astounded at the time that people weren’t super-concerned about asbestos contimanation. The towers were built at a time when asbestos was still a very popular material. Aside from its carciogenicity, asbestos is a wonderful material with many advantages (fireproof, excellent elecrrical and heat insulator, not subject to decay), one which one can obtain for literally just the effort of digging it out of the ground. So quite naturally it found wide use.
I was once system and network manager in a building that was built before the nasty truth about asbestos became widely known. It made running new network wiring a constant headache; one couldn’t so much as drill through most walls in that building without spending thousands of dollars to protect against liberating asbestos fibers.
Those towers were obviously full of asbestos-containing building materials, so naturally so was the dust left by their collapse. Any claims the dust was not hazardous were obviously baloney. If any initial measurements indicated a lack of hazard, that was reason not to abandon extreme caution but to suspect the quality of the measurements.