EPA interim final report on WTC background study, April 2003

NYC 9/11 Public Portal Document

detection limit (Van Orden et al. 1995).

Presented in Table 7-1 is a summary of U.S. residential building average asbestos concentrations by direct TEM as found in the literature search.

7.1.2 Settled Asbestos Dust Measurements Ewing (2000) reported a geometric mean of 1000 s/cm^ for samples collected in six buildings without friable asbestos-containing surfacing materials. The 28 microvacuum samples were collected and analyzed as described in the ASTM Method D 5755-95 or the earlier draft-EPA method (Clark 1989). The sampled surfaces would be considered non-porous and usually had visible dust on them. The surface types included polished stone, metal, polished wood, and plastic. Neither the types of buildings nor their locale were identified. The Study reported a geometric, ratiier than arithmetic, mean as a measure of central tendency. Table 7- 2 is extracted from that report.

7.1.3 Airborne Man-Made Vitreous Fibers Measurements Man-made vitreous fibers (MMVFs) are also known as synthetic vitreous fibers (SVFs). ATSDR (2001) reported that airborne concentrations of MMVFs in outdoor and indoor air samples usually are <0.0001 free. Measurements at workplaces that manufacture MMVF have been reported to be <0.1 to 1 free. Airborne concentrations > 1 free have been observed during the installation of insulation in a home or building, but these high levels would drop to pre­ installation values within 1 or 2 days.

As summarized by ATSDR (2002), a report by Carter et al. (1999) used both PCM and SEM to study air samples from 51 residential and commercial buildings throughout the United States. Only 2 of the 50 samples analyzed by SEM were found to contain respirable MMVFs. The MMVF concentrations were not included in the ATSDR (2002) summary.

7.1.4 Man-Made Vitreous Fibers in Settled Dust or Soil According to the ATSDR (2002), no data exist pertaining to the ambient levels of MMVFs in soil or sediment. The literature search also has not located data on MMVF loading in residences.

7.1.5 Lead Levels in the Ambient Air As reviewed by ATSDR (1999), lead levels in the ambient air vary widely but usually decrease witii increasing distance (both vertical and horizontal) from emission sources. The EPA (1996) has established the National Ambient Air Quality Standard for lead of 1.5 pg/m’, quarterly average concentration. Composite urban air measurements of lead for 1991 were reported at 0.08 pg/m’ (EPA 1996). In 1988, the average lead concentration for 139 urban air-monitoring sites around the United States was 0.085 pg/m’ and remained relatively unchanged, at 0.04 pg/m^, when estimated between 1994 and 1995 (ATSDR, 1999). Indoor air lead levels are generally 0.3 to 0.8 times lower than the corresponding outdoor

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