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The collapse of the World Trade Center (WTC) on September 11, 2001, generated large amounts of dust and smoke that settled in the surrounding indoor and outdoor environments in southern Manhattan. Sixteen dust samples were collected from undisturbed locations inside two uncleaned buildings that were adjacent to Ground Zero. These samples were analyzed for morphology, metals, and organic compounds, and the results were compared with the previously reported outdoor WTC dust/smoke results. We also analyzed seven additional dust samples provided by residents in the local neighborhoods. The morphologic analyses showed that the indoor WTC dust/smoke samples were similar to the outdoor WTC dust/smoke samples in composition and characteristics but with more than 50% mass in the <53-microm size fraction. This was in contrast to the outdoor samples that contained >50% of mass above >53 microm. Elemental analyses also showed the similarities, but at lower concentrations. Organic compounds present in the outdoor samples were also detected in the indoor samples. Conversely, the resident-provided convenience dust samples were different from either the WTC indoor or outdoor samples in composition and pH, indicating that they were not WTC-affected locations. In summary, the indoor dust/smoke was similar in concentration to the outdoor dust/smoke but had a greater percentage of mass <53 microm in diameter.

The explosion and collapse of the World Trade Center (WTC) was a catastrophic event that produced an aerosol plume impacting many workers, residents, and commuters during the first few days after 11 September 2001. Three bulk samples of the total settled dust and smoke were collected at weather-protected locations east of the WTC on 16 and 17 September 2001; these samples are representative of the generated material that settled immediately after the explosion and fire and the concurrent collapse of the two structures. We analyzed each sample, not differentiated by particle size, for inorganic and organic composition. In the inorganic analyses, we identified metals, radionuclides, ionic species, asbestos, and inorganic species. In the organic analyses, we identified polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, polychlorinated dibenzodioxins, polychlorinated dibenzofurans, pesticides, phthalate esters, brominated diphenyl ethers, and other hydrocarbons. Each sample had a basic pH. Asbestos levels ranged from 0.8% to 3.0% of the mass, the PAHs were > 0.1% of the mass, and lead ranged from 101 to 625 microg/g. The content and distribution of material was indicative of a complex mixture of building debris and combustion products in the resulting plume. These three samples were composed primarily of construction materials, soot, paint (leaded and unleaded), and glass fibers (mineral wool and fiberglass). Levels of hydrocarbons indicated unburned or partially burned jet fuel, plastic, cellulose, and other materials that were ignited by the fire. In morphologic analyses we found that a majority of the mass was fibrous and composed of many types of fibers (e.g., mineral wool, fiberglass, asbestos, wood, paper, and cotton). The particles were separated into size classifications by gravimetric and aerodynamic methods. Material < 2.5 microm in aerodynamic diameter was 0.88-1.98% of the total mass. The largest mass concentrations were > 53 microm in diameter. The results obtained from these samples can be used to understand the contact and types of exposures to this unprecedented complex mixture experienced by the surviving residents, commuters, and rescue workers directly affected by the plume from 11 to 12 September and the evaluations of any acute or long-term health effects from resuspendable dust and smoke to the residents, commuters, and local workers, as well as from the materials released after 11 September until the fires were extinguished. Further, these results support the need to have the interior of residences, buildings, and their respective HVAC systems professionally cleaned to reduce long-term residential risks before rehabitation.