NYC-WTC_000199812

NYC 9/11 Public Portal Document

asbestos concentration of 0.016 structure/mL. Some contamination of the exterior air sample by chrysotile might have been expected, given that asbestos-containing debris from the collapse of the buildings had accumulated on the exterior window ledges to the maximum depth possible. No asbestos structures of any size were detected on the open field blank. All horizontal surfaces of Apartment lOD were covered by a thick layer of dust and debris that contained asbestos. It is important to take into account that the indoor air concentration results reported were obtained under passive sampling conditions with no active ventilation and minimum disturbance of the surface dust and debris. Disturbance of the dust by routine methods of dry dusting and vacuuming would significantly increase the airborne asbestos concentrations in the apartment. Based on the amount of visible dust and debris on surfaces in the apartment, the airborne asbestos could increase by orders of magnitude.

5.2 Dust and Debris Samples Collected from Surfaces in Buildings

5.2.1 Sample Collection

At 45 Warren Street, dust and debris were visible on surfaces in the apartments. A wet non-woven cloth was used to collect dust and debris samples in accordance with ASTM D6480-99. At 250 South End Avenue, a window had been broken and the hard surfaces of furniture were coated with a layer of dust and debris sufficiently thick that it could be swept up with a brush. A new toothbrush was first used to remove dust and debris from a known area of the surface, and the collected material was transferred to a plastic container, after which a wet non­ woven cloth was used to collect the visible dust and debris that still remained on the surface. Sampling was conducted in accordance with ASTM D6480-99. Each wet cloth was stored in a plastic container.

5.2.2 Sample Analysis / The wipe samples were analyzed according to ASTM D6480-99. For each of the two dust and debris samples collected using a toothbrush at the 250 South End Avenue location, a known weight of the dust and debris sample was dispersed in 100 mL of filtered distilled water.

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NYC-WTC_000199848