EPA interim final report on WTC background study, April 2003

NYC 9/11 Public Portal Document

Asbestos. In the days immediately following the disaster, EPA analyzed the settled bulk dust/debris for asbestos content. More than one third of the approximately 150 samples registered an asbestos concentration greater than 1% [EPA 2002c]. Since that time, EPA has taken the position that WTC-related dust should be considered potentially asbestos-contaminated and handled accordingly. Additionally, indoor settled dust samples collected from residential buildings in November and December 2001 indicated that 18% of the indoor locations sampled contained measurable levels of asbestos [NYCDOH, 2002]. Therefore, asbestos is included as a COPC.

Fibrous Glass. Analysis of WTC bulk dust/debris has consistently identified fibrous glass to be a major constituent of the material [Lioy 2002, USGS 2001]. In addition, an NYCDOH/ATSDR study [NYCDOH, 2002] found fibrous glass in the interior settled dust in 41% of the locations sampled at concentrations up to 35%. Air samples collected in areas with fibrous glass in settled dust indicate no fiber levels of immediate concern. Although fiber counts were found in four areas with slightly greater than background (0.004-0.006 free), subsequent re-analysis indicated actual fibrous glass concentrations from these areas as 0.00004 to 0.00026 free. Air samples from remaining areas showed a maximum 0.003 free total fiber count by PCM. These wools may be skin, eye, and respiratory tract irritants. Although there are no standards to evaluate the settled dust content, the presence of fibrous glass in settled dust does indicate a potential for exposure. Therefore, fibrous glass is included as a COPC.

Crystalline Silica. Settled dust and air samples taken in indoor and outdoor areas of residential buildings in November and December of2001 indicate the presence of alpha-quartz. Other forms of crystalline silica were not found. This is consistent with outdoor dust and debris samples collected by the USGS [USGS, 2001] and subjected to mineral analysis. Quartz was found in approximately 49% of the settled dust samples from indoor areas of residential buildings and all of the associated outdoor areas sampled. Levels of quartz ranged as high as an estimated 31.4% of the dust by weight in a residence. Since quartz is a common material in sand, finding this mineral in a city where there is a great deal of concrete is not unusual. However, quartz in dust from a comparison area unaffected by the WTC collapse ranged from non-detect only up to an estimated 2.2% in the residence [NYCDOH, 2002]. Seventeen residential areas and eleven common areas had quartz levels greater than the associated comparison area. Therefore, quartz was deemed to be elevated in some indoor areas of lower Manhattan relative to the comparison area. Additionally, quartz was found in 13% of the respirable fraction air samples taken in these areas, ranging from an estimated 4-19 ug/m3, demonstrating a potential for exposure. Although below occupational standards, this estimated concentration is above the effective NAAQS standard for the silica fraction of respirable particulate matter. Therefore crystalline silica, measured as alpha-quartz, is included as a COPC.

In addition to crystalline silica, calcite, portlandite and gypsum were the most abundant minerals detected in settled dust samples from residential areas in lower Manhattan following the WTC collapse. Mica was detected with much less frequency, generally at less than 0.1% of the dust. Halite (salt) was also detected at trace levels. Calcite, portlandite, and gypsum are typical components of concrete and gypsum based wallboard products, which were present in the WTC buildings. While high concentrations of these minerals in airborne dust constitute a short-term

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