VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

Section II. Exposure Assessment and Risk Characterization Approach Exposure assessments and risk characterizations for all contaminants focus on the inhalation pathway. For most chemicals, potential health risks are evaluated by comparing the measured air levels at locations near Ground Zero to established benchmarks for inhalation exposure and to typical urban background levels. Occupational Safety and Health Administration (OSHA) Permissible Exposure Limits (PELs), National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Levels (RELs), and Agency for Toxic Substances and Disease Registry (ATSDR) Minimal Risk Levels (MRLs) are among the benchmarks included in this evaluation. Where available, benchmarks established to protect against acute and subchronic exposures are used. Benchmarks that are intended to protect against exposures lasting more than one year or throughout a lifetime, such as EPA’s Reference Concentrations (RfCs), were only used if other more appropriate benchmark values were not available. Table 1 provides a summary of the inhalation benchmarks used in this analysis.

EPA’s Region 2, in consultation with federal health agencies, also used benchmark values to compare with measured air concentrations. These are described and listed in Appendix A, and are also cited on EPA’s WTC web site: http://www.epa.gov/wtc . Region 2 used existing standards where appropriate, and for other contaminants, developed unique standards specifically for the purpose of evaluating the air measurement data from the WTC site. Some of the existing standards which they used included occupational standards such as OSHA PELs, which were used for all site workers conducting response/demolition activities covered by OSHA, and environmental standards such as National Ambient Air Quality Standards (NAAQS: e.g., for lead) and the Asbestos Hazard Emergency Response Act (AHERA) level of concern for asbestos to evaluate monitoring data from the site perimeter and beyond where residents or non- WTC site workers may have been exposed. In cases where appropriate standards did not exist, the Region developed risk-based screening criteria. The risk assessment paradigm detailed in EPA’s “Hazard Evaluation Handbook: A Guide to Removal Actions” (HEH; EPA, 1997b) was employed in the development of these risk-based criteria. Screening levels that the Region developed reflect the most current toxicity criteria (Slope Factors and RfCs) on EPA’s IRIS database (http://www.epa.gov/iris ). The Region developed benchmark values for cancer and non-cancer effects. Details of the Region’s derivation procedure are provided in Appendix A.

Some of the benchmarks used by the Region were also used as benchmarks in this report, such as the AHERA standard, while others were not. The unique benchmarks developed by Region 2 for evaluating WTC air measurements were not used in this report. The Region needed to develop and utilize those benchmarks in order to provide daily data reports that were readily understandable. Only existing benchmarks were used in this report, and in some cases, cancer or non-cancer screening exercises that went beyond a simple comparison to a benchmark were employed (e.g., dioxin-like compounds, see discussion below). Efforts are underway within EPA to develop benchmarks and similar standards to evaluate the impacts from a short-term inhalation exposure such as that experienced by some individuals at the WTC site. One such effort entails the development of Acute Exposure Guideline Levels. Final AEGLs are available for some contaminants, such as vinyl chloride, methylene chloride, methyltrichlorosilane, and others, but finalized (or draft) AEGLs are not currently available for the contaminants evaluated in this report.

DRAFT~DO NOT QUOTE OR CITE 15 October 2002

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