NYC-WTC_000232959

NYC 9/11 Public Portal Document

including two from an indoor area. Quartz, calcite, and gypsum were reported for all of these samples. Each of these was occasionally reported as a major constituent of the material, i.e., estimated at 20% or higher. Twenty-six of these samples contained mica, usually estimated as trace or less than 5% of the material. Portlandite was only noted in two samples at trace levels, including the one indoor sample analyzed.

1. Association of Asbestos and Synthetic Vitreous Fibers

Based upon the sampling results, it appears that SVF is likely to be found in settled surface dust whenever asbestos is detected in the settled surface dust. All of the six outdoor and five common areas that had asbestos in settled surface dust also had SVF in the settled surface dust (Table 9). Of the ten residences that contained asbestos in settled surface dust, a little more than half also contained SVF. However, this does not hold true in areas without asbestos, where the absence of asbestos does not indicate an absence of SVF. Of the eight outdoor areas without asbestos in the settled surface dust, three contained SVF. Similarly, SVF was found in approximately 25% of the common areas and in approximately 36% of the residences without asbestos in the dust. Although the presence of asbestos in the dust seems to correspond to SVF, the absence of asbestos does not predict or correspond to a presence or absence of SVF in settled surface dust, in either indoor or outdoor areas of lower Manhattan.

2. Association of Asbestos and Synthetic Vitreous Fiber Levels Outside of and Within a Building

Outdoor settled surface dust was collected at 14 buildings in lower Manhattan. One purpose for collecting outdoor dust was to determine if the contents of the outdoor dust at a location would reflect the type of indoor dust. In the case of fibers, there is little correlation in the indoor and outdoor dust composition. High levels of outdoor SVF are associated with both high and low indoor levels. The presence or absence of asbestos in settled surface dust shows a similar lack of correlation. The outdoor settled surface dust samples do not correspond with indoor dust composition for either group of fibers. This lack of association could, in part, be due to whether and how frequent interiors and exteriors had been cleaned.

In contrast, indoor levels of fibers in settled surface dust did seem to correspond within a building. Buildings with elevated SVF levels in the common area tended to have elevated levels in the residences. A similar pattern was seen between the two residences sampled in the same building. For example, SVF was often found in both residences sampled within the same building, or was absent in both residences. Within this limited data set, fiber levels in one area of a building seem to weakly correspond with fiber levels in other areas of the same building. However, none of these data represent total dust loading, only the relative amount of fibers within the dust.

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NYC-WTC_000232995