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World Trade Center Indoor Environmental Assessment: Selecting Contaminants of Potential Concern and Setting Health-Based Benchmarks (May, 2003)

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(This Program Ended in 2003)

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Summary

Table 1 - health-based benchmarks

In February 2002, A multi-agency task force headed by EPA was specifically formed to evaluate indoor environments for the presence of contaminants that might pose long-term health risks to local residents. As part of this evaluation, a task force sub-committee was established (COPC Committee) to identify contaminants of potential concern that are likely associated with the WTC disaster and establish health-based benchmarks for those contaminants in support of planned residential cleanup efforts in Lower Manhattan.

A systematic risk-based approach was used to select COPC. The goal was to identify those contaminants most likely to be present within indoor environments at levels of health concern. The following chemicals were identified as COPC:

Health-based benchmarks were developed to be protective of long-term habitability of residential dwellings. A hierarchical approach was employed for developing benchmark values, including relevant and appropriate environmental standards/regulations (HUD standard for lead in indoor dust); calculation of health-based benchmarks employing conventional environmental risk assessment paradigms and guidance (asbestos, dioxin and PAHs); and adaptation of occupational standards with additional safety factors (fibrous glass and crystalline silica).

Table 1 lists the health-based benchmarks for the COPC for indoor air and settled dust. Benchmarks for asbestos, fibrous glass and crystalline silica in settled dust are not provided because these three minerals exert their toxicity primarily through the inhalation route of exposure. Therefore, a health-based benchmark for settled dust would be a function of the relationship between the mineral content in settled dust and indoor air. Due to the numerous factors that influence the relationship between fiber concentration in settled dust and indoor air, including surface porosity, activity patterns, air exchange rates and interior volume, the COPC Committee elected against setting benchmarks for COPC in settled dust based on projected concentrations in indoor air.

Table 1

COPC
Indoor Air
Settled Dust
Asbestos 0.0009 S/cc n/a
Lead 0.7 ug/m3 25 ug/ft2
MMVF 0.01 S/cc n/a
Dioxin 0.001 ng/m3 2 ng/m2
PAH 0.2 ug/m3 150 ug/m2
Silica 5 ug/m3 n/a

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