WTC environmental investigation report, Sep 2002

NYC 9/11 Public Portal Document

Final Technical Report of the Public Health Investigation Page 29 of 56 detection limit of 0.001 f/cc. Because the levels found were within the range measured in the comparison areas above 59th Street, no TEM or SEM re-analysis was performed on these air samples, and the composition of these fibers is unknown (i.e., asbestos, SVF, cellulose).

2. Minerals in Air

Air samples of different particulate sizes, representing inhalable (PMIOO), thoracic (PMIO), and respirable (PM4 and PM2.5) fractions were collected in selected building locations. Not all size fractions were collected at every location. The samples were analyzed by XRD for the same crystalline minerals seen in the settled surface dust samples. Each of the four size fractions was collected with a separate sampling device. The PMIOO fraction collected particles with an aerodynamic diameter of 100 microns and lower. The PMIO fraction collected particles with an aerodynamic diameter of 10 microns and lower and so on. The results reported here are expressed as the mass of mineral per unit volume of air or micrograms per cubic meter of air (pg/m^). Quantification of the minerals is not exact due to variations in particle size as compared to the particle size used in the standard curve and other methodological interference. Therefore, these data will only be considered semiquantitative and should be treated as estimated values, noted by the "J" qualifier.

Due to changes in sample volume, the detection limit of minerals in each fraction varied, allowing lower concentrations to be recorded in the PMIO and PMIOO fractions compared to the PM4 fraction. Care must be taken when comparing results between fractions for this reason. Additionally, although the PM4 fraction should be a subset of the PMIO and PMIOO fractions, PM4 results are sometimes higher than PMIO or PMIOO from the same location. Therefore, due to uncertainties in the quantification and general quality assurance/quality control concerns, data will not be associated to a specific building sampling location or correlated between size fractions at the same location.

The comparison air samples, taken in areas above 59th Street, contained no quartz, cristobalite, tridymite, calcite, portlandite, mica, or halite above method detection limits (Table 11). Gypsum was found at least once in all size fractions collected in the comparison areas above 59th Street. Gypsum concentrations were estimated at 3 pg/m^J (PM2.5), 5 pg/m^J (PM4), 3 pg/m^J (PMIO), and 3 pg/m^J (PMIOO) (Table 11).

All of the minerals found in the settled surface dust were seen in at least one air sample from lower Manhattan (Table 11). Quartz, calcite, portlandite, and gypsum were detected at similar frequencies in each of the larger size fractions, PMIOO, PMIO, and PM 4. Table 11 shows the frequency of detection and the range of estimated values for each size fraction sampled. Quartz and gypsum were each detected once in the PM 2.5 fraction. The PM 2.5 size fraction was only collected toward the end of the project, and there are fewer samples for this size fraction.

Estimated levels of minerals in air, including quartz^ calcite.

http://www.atsdr.cdc.gOv/asbestos/lowermanhattan/ResSamp_Sep2002_Text.html 07/18/2003 NYC-WTC_000178416