Draft document with asbestos data tables, DEP Box 09

NYC 9/11 Public Portal Document

-X (. > DRAFT daily exposure estimates combine the exposure point concentrations with assumptions about the magnitude (how much), frequency (how often), and duration of exposure (how long). The point at which exposure occurs (i.e., exposure point) and the pathways through which a receptor comes in contact with the exposure point(s) (i.e., exposure pathways) are discussed below for the receptors quantitatively evaluated in the risk assessment:

• New York City Personal Vehicle Commuter: The potential exposure point for the Commuter is air space inside the vehicle where asbestos fibers are resuspended as a result of the vehicles ventilation system and during an occasional interior cleaning. The exposure pathway for the Commuter is inhalation of airborne asbestos fibers. The Commuter was assumed to be exposed for two hours, one hour, and one-half hour per day (representative of different lengths of commute), 6 days per week, for 10 years (length of service for recovered vehicle).

Estimation of Exposure Point Concentrations The exposure point concentration (EPC) is the measured or estimated amount of a chemical in the environmental medium of concern at the point of human contact. The environmental media of concern is the interior airspace of the vehicle.

For the purpose of this risk assessment, the exposure point concentration is calculated as specified in Chapter 6 of the Risk Assessment Guidance for Superfund (EPA, 1989) and the Supplemental Guidance to RAGS: Calculating the Concentration Term (EPA, 1992). This statistical method uses a confidence interval to calculate a theoretical concentration. The calculated concentration is the 95% upper confidence limit (UCL) on the arithmetic average. This means that the chance that the actual average concentration of airborne asbestos exceeds the 95% UCL is estimated to be less than 5%. Data from all 236 samples collected were considered in calculating the 95% UCL. Non-detected results were entered into the data set as one-half of the non-detected value. This is done to address uncertainty in the true asbestos concentration stemming from limitations in the laboratory’s ability to detect very small concentrations. It is assumed, for purposes of the risk assessment, that the true asbestos concentration is somewhere between zero and the laboratory’s limit of detection. The 95% UCL was calculated using the following formula:

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