Potential exposures to airborne and settled surface dust in residential areas of lower Manhattan following the collapse of the World Trade Center — New York City, November 4-December 11, 2001

Morbidity and Mortality Weekly Report, Feb 21, 2003

Following the terrorist attacks of September 11, 2001, which destroyed the World Trade Center (WTC) in lower Manhattan, the New York City (NYC) Department of Health and Mental Hygiene (DOHMH) and the Agency for Toxic Substances and Disease Registry (ATSDR), with assistance from the U.S. Public Health Service (PHS) Commissioned Corps Readiness Force* and the WTC Environmental Assessment Working Groupt, assessed the composition of outdoor and indoor settled surface and airborne dust in residential areas around the WTC and in comparison areas. This report summarizes the results of the investigation, which found 1) similar levels of airborne total fibers in lower and in upper Manhattan, 2) greater percentage levels of synthetic vitreous fibers (SVF) and mineral components of concrete and building wallboard in settled dust of residential areas in lower Manhattan than in upper Manhattan, and 3) low levels of asbestos in some setded surface dust in lower Manhattan residential areas (1). Based in part on the results of this investigation, the U.S. Environmental Protection Agency (EPA) is cleaning and sampling residential areas as requested by lower Manhattan residents. In addition, to assess any short- or longterm health effects of smoke, dust, and airborne substances around the WTC site, DOHMH and ATSDR are developing a registry that will track the health of persons who were most highly exposed to these materials.

During November 4-December 11, 2001, air and settled surface dust samples were collected in and around 30 residential buildings within three concentric circles surrounding the WTC site in lower Manhattan, including 59 residential units (2). In addition, five residential units in four buildings located north of 59th Street (approximately 5 miles northeast of the WTC site) were sampled for purposes of comparison. Attention was focused on building material constituents 1) that have irritant properties (e.g., SVF, including fiberglass and gypsum) or might have negative long-term health effects (e.g., crystalline silica and asbestos) and 2) that were reasonably presumed to be either in the initial WIC collapse dust cloud or in dust generated by subsequent rescue and recovery activities at the WTC site. All samples collected during the Investigation were analyzed for the presence of asbestos, SVF, crystalline mineral components of concrete (e.g., silica, calcite, and portlandite), and crystalline mineral component s of building wallboard (e.g., gypsum, mica, and halite).

At each sampling location, time-weighted air sampling was conducted for three or four particulate matter (PM) fractions (i.e., PM 100 microns, 10 microns, 4 microns, and 2.5 microns) (3-5). Each PM fraction was analyzed for crystalline minerals by using X-ray diffraction (XRD) analysis (6). The XRD analysis for crystalline minerals was semiquantitative (i.e., estimated). Air samples for fibers were analyzed first by phase contrast microscopy (PCM) (5). If the concentration of total fibers was higher than the maximum concentration of fibers found in the comparison homes (0.003 fibers per cubic centimeter of air [f/cc]), the sample was re-analyzed for asbestos fibers by using transmission electron microscopy (TEM) (5). In addition, scanning electron microscopy (SEM) to look for SVF was used for PCM fiber counts >0.003 f/cc if the settled surface dust sample from that area contained SVF.

Settled surface dust samples also were taken at each sampling location and analyzed for crystalline minerals and fibers (Figure). Fiber analysis of settled dust samples for asbestos and SVF was conducted by using polarized light microscopy (PLM) (7). If asbestos levels were below the detection limit (i.e., <1%), samples were re-analyzed by using TEM (7). The dust samples also were analyzed for crystalline mineral content by using XRD.

Air Sampling Results

For 111 (94.9%) of the 117 air samples, the concentrations of fibers found in lower Manhattan residential areas were similar to the concentration of fibers found in comparison areas (<0.003 f/cc). The six lower Manhattan areas that had elevated total fiber counts were re-examined by TEM and SEM to determine the types of fibers; the results indicated that neither asbestos nor SVF (e.g., fiberglass) contributed to the elevated total fiber counts.

Air sampling results for minerals detected quartz and other building material constituents in lower Manhattan. No other forms of crystalline silica were detected in any air samples except for a one-time detection of cristobalite (15 micrograms per cubic meter [[micro]g/[m.sup.3]](ss)). The estimated concentrations of these minerals in air were low. In some locations, mineral components of concrete (quartz [nor detected (ND)-19 [micro]g/[m.sup.3[section]], calcite [ND-14 [micro]g/[m.sup.3[section]]], and portlandite [ND-95 [micro]g/[m.sup.3[section]]]) and mineral components of building wallboard (gypsum [ND-15 [micro]g/[m.sup.3[section]]], mica [ND-43 [micro]g/[m.sup.3[section]]], and halite [ND-19 [micro]g/[m.sup.3[section]]]) were detected at higher estimated levels in air samples in lower Manhattan than in samples collected in comparison areas. Gypsum was the only mineral detected in the comparison building air samples (ND-5 [micro]g/[m.sup.3[section]]). No other minerals tested (i.e., quartz, calcite, po rtlandire, mica, and halite) were detected in comparison building air samples.

Settled Surface Dust Results

In lower Manhattan, asbestos and SVF were found in some indoor settled dust samples from residential units and common areas (Table 1). No asbestos or SVF was detected in the comparison area dust samples. Quartz, calcite, portlandite, and gypsum comprised a higher percentage of the dust in 29 samples from buildings in lower Manhattan compared with eight samples from comparison area buildings (Table 2). Only two (2.1%) of the 97 dust samples collected provided enough bulk material for pH analysis. The samples, which were collected from two outdoor locations in lower Manhattan, had pH values of 8.6 and 9.8, respectively.