NYC-WTC_000232959

NYC 9/11 Public Portal Document

Twenty-three buildings (approximately 79%) had levels of at least one of these materials in the dust at levels higher than the maximum found in the comparison buildings. Four of these buildings (buildings 4, 5, 6, and 9) contained all four materials above levels seen in the comparison areas above 59th Street in at least one indoor sample (Table 7). Seven of the 23 buildings were only impacted by SVF in indoor areas (buildings 13, 14, 17, 18, 25, 26, and 28). One building was only impacted by asbestos (building 11). The remaining 11 buildings were impacted by some combination of fibers and minerals. No clear pattern emerges in terms of which fibers or minerals occurred in the indoor dust of a building. Three of these building had only the two fiber types present (buildings 15, 24, and 27). One of these building had only the two minerals present (building 8).

The limited number of buildings sampled and the limited number of indoor locations that were sampled make it difficult to draw conclusions about the relationship of geographical location and the number of different materials found in the dust above the levels found in the comparison locations. However, buildings close to the World Trade Center tend to have a greater number of these materials found.

5. Significance of Minerals and Fibers in the Settled Surface Dust

The results previously discussed indicate minerals, asbestos, and SVF are all found at higher percentages in the samples from lower Manhattan when compared to the sampled areas above 59th Street. These findings are based on comparing the percent of each mineral and fiber in the settled surface dust. However, to determine the total mineral and fiber content in a room, the amount of dust present would also need to be known. Because surface loading is not known, we cannot demonstrate that the total amount of mineral and fiber is increased in any given area. However, these data indicate the components and quality of the dust in lower Manhattan is different from that of the comparison areas above 59th Street.

The increased crystalline minerals and fibers in the settled surface dust indicate a potential for contact with these materials. The magnitude of this contact will vary with dust loading (which is unknown) and activity in the area. Residents may come into contact with the dust directly (i.e., skin, eyes). Additionally, the dust may also become re-suspended in the air through activities such as cleaning. In this way the settled surface dust may be a reservoir for material in the air. Therefore settled surface dust results are important both to evaluate direct contact, as well as to evaluate the potential for airbome/inhalation exposures.

6. Significance of Minerals and Fibers in Air

The settled surface dust samples suggest the potential for airborne particles and fibers. The air samples taken indicate that some of these materials are present in the air at measurable levels. Because the air samples were taken over several hours, they provide an understanding of average air levels over the course of the day. Some of these air samples were taken during normal daily activity outdoors in common areas and in residences. They represent the impact of vehicular traffic, walking, and normal activity in the area. As such they are a good measure of average exposure at that time and place. No samples were taken

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NYC-WTC_000232997