NYC-WTC_000230857

NYC 9/11 Public Portal Document

Submitted to American Industrial Hygiene Association. October 2, 2001

approximately two city blocks from the focal point and a second approximately four city blocks along the radian. A graphical depiction of the sample location plan is presented in figure 2. A number was assigned to each location (as noted in figure 1) and this number is used as a descriptor for each sample of surface residue.

Subsequently, eleven air samples were collected within two building structures located near the collapsed WTC towers. Building structure A sustained limited damage but some areas of the lower floors were littered with paper debris and were coated with a layer of surface residue (see figure 5) . Building structure B sustained major damage with most areas littered with paper debris and coated with a layer of surface residue. Air samples within these two buildings were collected using 25 mm diameter, banded AHERA TEM cassettes (0.45 pm pore size mixed cellulose ester collection filter plus 5 pm pore size diffusion filter and cellulose support pad) (Zefon Analytical Accessories). Air sampling pumps (Gillian model/PN 800845) were calibrated at 2.0 liters per minute (EPM) and collection times varied with total air volumes ranging from 488 - 558 liters. Air sample locations are listed in Table 1. During air sample collection within Building A, routine loading and unloading of equipment was occurring in the loading dock area, routine office work was being performed within the 3”''’ floor office, debris removal associated with the repair of broken windows was occurring in the 11“* floor office, and no work was being performed in the 36* floor office where windows were still intact. During air sample collection in Building B, no work was being conducted in the 3"* floor office space but contractors staged their various repair activities in the 3”'‘* floor staging area. On upper floors (6* and 9*) of Building B, debris removal associated with preparations to repair broken windows was underway during air sample collection, with this activity concentrated on the 6* floor.

Asbestos content of the surface residue was determined by PLM using EPA method 600/R-93/116 dated July 1993 with visual volume estimation of the weight/weight percentage (w/w%) of asbestos. Quantitation of asbestos content was also determined independently for all samples of surface residue using the EPA 400 point count method.

Particle characterization was performed by MVA, Inc. in the following manner (Millette, 2001). The dust samples were characterized by both gravimetric measurement of sieve size fractions and by microscopical analyses. The samples were sieved using standard 4- inch diameter brass sieves (U.S. Standard Sieve Mesh #s 50 and 200). The gravimetric determinations were made of the following size fractions: >300pm, 75 - 300pm, and <75pm. The fractions were combined and examined by stereomicroscopy utilizing a Zeiss Stemi 2000 stereomicroscope having a magnification range from 6.5X to 47X. The components of the samples were then analyzed utilizing an Olympus BH-2 polarized light microscope (PEM) having a magnification range from 40X to lOOOX. A visual estimate was made of the relative percentage by volume of loosely aggregated separable fibrous lint (hair + natural fibers + manmade fibers). Each identified constituent was rated as to whether it was "common" (consistently found throughout the sample) or "present" (detected but infrequently). The fine portions were analyzed by scanning electron microscopy (SEM) and transmission electron microscopy. The SEM analysis was done with a JEOE 6400 equipped with a Noran Voyager energy dispersive x-ray

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