WTC environmental investigation report, Sep 2002

NYC 9/11 Public Portal Document

Final Technical Report of the Public Health Investigation Page 25 of 56 lower Manhattan is higher than that of the selected comparison areas above 59th Street (Figure 11).

2. Mineral Analysis of Settled Surface Dust

Settled surface dust samples were analyzed for crystalline minerals potentially associated with the material from the collapsed World Trade Centers. The results reported here are expressed as a mass percent of the dust (weight of minerals per weight of dust). Quantification of the minerals in dust is not exact due to variations in particle size and other methodological interference. Therefore, these data will only be considered semiquantitatively and should be considered estimated values, noted by the "J" qualifier.

Quartz, calcite, portlandite, and gypsum were the most abundant minerals detected (see Table 7). Mica was detected with less frequency than the other minerals, and generally estimated at approximately 0.1%J of the dust. Halite (salt) was also detected at trace levels.

Mineral components of concrete (quartz calcite, and portlandite) and other building materials (gypsum, mica, and halite) in the indoor settled surface dust of some areas of lower Manhattan were estimated at higher percentages than for the comparison areas above 59th Street.

Quartz was detected in all 14 outdoor dust samples, 21 of the 26 common area samples, and only 30 of the 57 samples from residences in lower Manhattan. Neither cristobalite nor tridymite, other forms of crystalline silica, were found in any of the settled surface dust samples. For this discussion quartz will refer to the alpha-quartz form of crystalline silica. Levels of quartz were estimated as from 0.05%J to 31%J in residences, and from 0.03%J to 25%J in common areas. Estimated quartz content in outdoor samples ranged from 1%J

to 27%J. Because quartz is a common material (i.e., silica sand), finding this mineral in the city where there is a lot of concrete building material is not unusual. However, quartz in dust from the comparison areas above 59th Street was estimated from nondetect to 1%J in the common areas and from nondetect to 2% 3 in the residences. Figure 16 shows the locations where the estimated maximum quartz content in settled surface dust was greater than or similar to estimated quartz content in the dust samples from the comparison areas above 59th Street. Fifteen residences, six common areas, and 12 outdoor areas had estimated quartz levels higher than the associated comparison areas above 59th Street. Therefore, quartz was elevated in some indoor areas of lower Manhattan relative to the comparison areas above 59th Street. Outdoor dust samples were not taken from the comparison areas, due to insufficient amounts of dust. Figures 13-16 compare the indoor and outdoor locations in lower Manhattan to the indoor samples above 59th to show the relative

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