NYC-WTC_000199812

NYC 9/11 Public Portal Document

significantly elevated if the asbestos-containing dust and debris on the surfaces was disturbed by routine methods of dry dusting and vacuuming. The results of the TEM analyses for asbestos in the air samples collected at 250 South End Avenue are shown in Tables 14 through 17. Because these samples were heavily loaded with large numbers of chrysotile fibers, the counting of stmctures greater than 0.5 pm had to be terminated after TEM examination of only one grid opening for each of the indoor samples. Examination of the TEM specimens for asbestos structures greater than 5 pm was continued. The maximum concentration of chrysotile structures greater than 0.5 pm was estimated to be 3.74 structures/mL, with an upper 95% confidence limit of 4.53 structures/mL, based on the TEM examination of only one grid opening. The maximum concentration of chrysotile fibers longer than 5 pm was 0.29 fiber/mL, with an upper 95% confidence limit of 0.35 fiber/mL. In Sample 250SEA-10D-A5, two fibers of richterite asbestos (longer than 5 pm) were detected, corresponding to an upper 95% confidence limit for the airborne richterite asbestos concentration of 0.030 fiber/mL (fibers longer than 5 pm). During the limited TEM examination of Sample 250SEA-10D-A5 for asbestos stmctures greater than 0.5 pm, one amosite fiber (longer than 5 pm) was detected, corresponding to an estimated upper 95% confidence limit for airborne amosite of 0.23 stmcture/mL. The maximum mean airborne concentration of PCM-equivalent chrysotile fibers observed under the passive conditions of the air sampling indoors was 0.075 fiber/mL, and the maximum upper 95% confidence limit was 0.12 fiber/mL. The two PCM-equivalent amphibole fibers (richterite asbestos) detected correspond to an upper 95% confidence limit of 0.030 fiber/mL. The maximum mean concentration of PCM-equivalent asbestos fibers and bundles (chrysotile + amphibole) was found to be 0.081 fiber/mL in Sample 250SEA-10D-A5, with an upper 95% confidence limit of 0.13 fiber/mL. Chrysotile was detected in the exterior sample collected outside the apartment window at 250 South End Avenue. The concentration of chrysotile structures greater than 0.5 pm was 0.22 structure/mL, with an upper 95% confidence limit of 0.27 structure/mL; the mean concentration of chrysotile fibers'longer than 5 pm was 0.022 fiber/mL, with an upper 95% confidence limit of 0.043 fiber/mL. In this exterior sample, one fiber of amosite (shorter than 5 pm) was detected, corresponding to an upper 95% confidence limit for the airborne amosite

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NYC-WTC_000199843