EPA interim final report on WTC background study, April 2003

NYC 9/11 Public Portal Document

7.1.8 Polycyclic Aromatic Hydrocarbons in Sediment and Soil No citation was found during the literature search for surface loading of PAHs in the indoor residential environment. ATSDR (1995) reported the results of several studies, published from 1973 through 1987, forbackground concentrations (pg/kg) of 15 PAHs in rural, agricultural, and urban soils from the United States and other countries. The ATSDR summary is reproduced here as Table 7-5.

7.2 Comparison of WTC Background Study to Other Studies Section 7.1 summarized the relevant studies that addressed background concentrations of COPCs in the residential indoor environment. This section is focused on the comparison of those studies to the WTC Background Study. As previously mentioned in Section 7.1, there are numerous factors that limit the ability to make direct comparisons between studies cited in the open literature that characterize background levels of the COPCs and the site-specific WTC Background Study. Thus, a qualitative discussion of study comparability needs to viewed accordingly. Still, where studies were identified that addressed background concentrations in a manner relevant to the WTC Background Study a comparison was performed. Where historical studies are described as being generally concordant with the findings in the WTC Background study, some disparities in study design, sampling/analytical protocols and results may still exist.

7.2.1 Comparison of Airborne Asbestos Concentrations The WTC Background Study obtained airborne asbestos measurements from residential dwellings and common spaces. Analysis was performed by TEM using two different counting methods - total asbestos fibers greater than 0.5 pm (as per AHERA counting rules), and asbestos fibers greater than 5 pm (PCMe) - and, by phase contrast microscopy (PCM). The literature review focused on PCMe measurements as this metric employs an analytical technique (TEM) that distinguishes asbestos from other fibrous material and counts only long fibers (i.e., > 5 pm) - those most closely associated with adverse health effects (i.e., cancer).

The Consumer Product Safety Commission (CPSC 1987) Study from the literature review was identified as providing relevant comparisons to the WTC Background Study. This study reported on airborne asbestos concentration in houses that contained asbestos containing material (ACM). In 15 houses in Cleveland and 15 houses in Philadelphia the mean asbestos concentration was 0.00023 free and 0.00007 free, respectively. A total of 30 samples were taken in Cleveland and 29 in Philadelphia (see Table 7-1). In the WTC Background Study, a total of 62 samples from residences and common spaces (see Table 6-1) were obtained. The mean asbestos (PCMe) concentration was 0.00022 s/cc. This value is consistent with the mean value reported from Cleveland and marginally higher than the mean value reported in Philadelphia.

The primary strength of the above comparison is the common metric (PCMe) employed to measure airborne asbestos concentration. It also focuses on urban WORLD TRADE CENTER BACKGROUND STUDY 34

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