NYC-WTC_000199582

NYC 9/11 Public Portal Document

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Chemical Reason Refractory Ceramic fiber-containing materials are not expected to be present in the WTC Ceramic buildings, as they are mainly used in industrial high temperature applications. Fibers Limited sampling conducted by NYCDOH, 2002 did not indicate any ceramic (RCF) fibers in four indoor air samples analyzed by scanning electron microscopy (SEM). Mold Mold was not directly associated with the WTC collapse. However, it may have resulted from the combination of water damage and inoperable HVAC systems. Guidelines for identifying and removing mold are provided through a NYCDOH website (see Appendix A).

Setting Benchmarks for the Contaminants of Potential Concern (COPCs)

A tiered approach was used to evaluate the health risks posed by contaminants that might be present in the indoor environment (air and settled dust). For each COPC, three levels were established:

Tier I Level above which, after elimination of potential indoor sources (combustion by-products, stored chemicals, etc.), aggressive clean-up action should be taken expeditiously along with follow-up sampling to confirm attainment of Tier III level

Tier II Range where diligent cleaning should continue, after elimination of potential indoor sources (combustion by-products, stored chemicals, etc.), with follow­ up sampling to confirm attainment of Tier III level

Tier III Level below which the risk is negligible or consistent with the New York City background level found in the aforementioned Background Study ( see Introduction).

The following hierarchal approach was employed for developing benchmark values; l)Use of relevant and appropriate environmental standards/regulations; 2) Calculation of risk-based benchmarks using EPA risk assessment guidance; and, 3) Adaptation of occupational standards with additional safety factors. Accordingly, a review of environmental standards/regulations was conducted for each of the six COPCs. As a result of this exercise Tier I screening levels for lead in indoor air and settled dust were set using EPA’s National Ambient Air Quality Standard (NAAQS) and the U.S. Housing and Urban Development’s (HUD’s) standard for floors, respectively. The clearance criteria established in the Asbestos Hazard Emergency Response Act (AHERA, 1986) of 70 structures/mm2 was utilized to evaluate asbestos samples from the ambient air monitoring effort. As detailed in Appendix B, the upper bound estimate for exposure duration to contaminants in the ambient air was one year. However, given the potential for extended exposure in residential dwellings, AHERA was deemed less appropriate to this setting.

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