Building materials from which the WTC Towers were constructed include structural steel, asbestos-containing insulation material, other insulating fibrous material (mineral wool and glass fibers), cement and aggregate (concrete), wallboard, ceiling tiles, ducts, wiring, paint, plate glass, and other components. Building contents of the WTC included computers and other electronic equipment, fluorescent lights, furniture, office supplies, and a myriad of other items. The brittle and friable components of these materials were pulverized during the collapse and the combustible components were partially burned in the ensuing fires.
The catastrophic structural collapse of the WTC resulted in coarse fragmentation as well as fine particle dust generation including asbestos and various chemicals of concern. The hazardous materials in the dust originated from many common sources. The National Resources Defense Council (NRDC) report estimated more than 1.2 million tons of building materials collapsed during the WTC Event containing an estimated 300 to 400 tons of asbestos. (NRDC, 2002) Additionally, 50,000 personal computers were destroyed, with each containing approximately 4 pounds of lead. (NRDC, 2002) Additionally, thousands of fluorescent light bulbs, thousands of light switches and other mercury-containing items were destroyed, releasing thousands of grams of mercury into the surrounding environment. These materials, properly contained and applied in their consumer products and form, presented no particular environmental or health hazard. It was, however, the pulverization of these items caused by the WTC collapse that liberated and rendered them bio-accessible, thus creating an environmental hazard.
