NYC-WTC_000199812

NYC 9/11 Public Portal Document

Th^ TEM specimens from these suspensions were then prepared according to ASTM D6480-99 in all subsequent steps.

5.2.3 Results

The results for the samples collected at 45 Warren Street are shown in Tables Cl 8 and Cl9. Table C18 shows the results for asbestos structures greater than 0.5 pm, and Table C19 shows the results for asbestos fibers and bundles longer than 5 pm. In these samples, surface chrysotile concentrations up to 470,000 structures/cm^ were observed, of which up to 79,000 fibers/cm^ were fibers and bundles longer than 5 pm. Only one amosite fiber, equivalent to a surface concentration of 2200 structures/cm\ was observed. During preparation of the specimens from the 5th Floor at 45 Warren Street, vermiculite particles in the aqueous suspension were found to be visible to the unaided eye. The results for the samples collected at 250 South End Avenue are shown in Tables 20 and 21. Table 20 shows the results for asbestos structures longer than 0.5 pm, and Table 21 shows the results for asbestos fibers and bundles longer than 5 pm. There are two results for each of the two surfaces sampled. The first result is for the dust and debris collected using a toothbrush. It should be noted that the collection areas specified are calculated from the actual area sampled multiplied by the proportion of the total sample analyzed. The second result in each location is for the follow-up wipe sample, and the collection area specified is the actual area sampled. For each sample location, the results for the two measurements in the final column of Tables 20 and 21 should be added to obtain the total asbestos concentration on the sampled surface. Surface chrysotile concentrations of up to 990,000 structures/cm^ were observed, of which up to 46,000 were fibers and bundles longer than 5 pm. No amphibole fibers were detected in these samples. The results show that the dust and debris that have settled on the surfaces in each of the apartments contain substantial amounts of chrysotile. It is important to recognize that the analytical method used is an indirect-transfer method, and that the results from this method, particularly in the case of chrysotile, do not represent the size distribution of the asbestos-containing particles as they existed on the original surface. The analytical method results in the dispersal of large clusters of chrysotile into individual chrysotile fibers and

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