CHARACTERIZATION OF SETTLED DUST FROM THE COLLAPSE OF THE WORLD TRADE CENTER

The collapse of the World Trade Center on 9/11 released an enormous amount of dust into the environment of Lower Manhattan. Over the next several days the bulk of the airborne dust settled out. We collected representative samples of settled dust six days later for analysis by polarized light microscopy, continuous scan x-ray diffraction and analytical transmission electron microscopy. The major crystalline phases were the minerals commonly found in construction materials such as gypsum, calcite and quartz. Polarized light microscopy showed that the overwhelming fiber present was synthetic vitreous fiber. No asbestos of any fiber-type was detectable by light microscopy. Using transmission electron microscopy trace amounts of chrysotile asbestos was readily detected in all the settled dust samples. Air samples collected starting, 26 days post-9/11, found airborne asbestos concentrations in Lower Manhattan had returned to background levels which are below the sensitive of our analysis – 0.00009f/mL. Synthetic vitreous fibers (commonly found in the settled dust) were found in the air samples at low concentrations but higher than the historical background. The asbestos exposures associated with the events of 9/11, prior to returning to background, were modeled from available data and reasoned assumptions. We used risk assessment to predict that the increased incidence of asbestos-related cancer among the residents of Lower Manhattan from the collapse of the WTC will be negligible.