Draft document with asbestos data tables, DEP Box 09

NYC 9/11 Public Portal Document

•V 1 ‘ DRAFT

The Risk Assessment Process Based on EPA (1989a) guidance, a four-part process was used to estimate the chance that exposure to airborne asbestos resulting from the return of recovered vehicles to normal use will result in adverse health effects. This process involves hazard identification, exposure assessment, toxicity assessment, and risk characterization.

Hazard Identification During the hazard identification step, data is collected and evaluated to determine what chemicals are present and at what levels. The memorandum referenced above lists asbestos, silica, fiberglass, cement dust, gypsum, calcite, and mica as the main constituents in the WTC dust and debris. With the exception of asbestos, these dust constituents were not present at levels associated with adverse health effects.

A total of 236 air samples were collected from FDNY and NYPD vehicles recovered from the WTC site. These vehicles were repaired, subjected to a “cursory” cleaning, and returned to service. The sampling protocol specified that the vehicles be driven with windows closed and ventilation systems on full during sampling. Table 1 provides a summary of the air sampling data. Asbestos was reported in 12 of 236 samples at detectable concentrations. Detected concentrations ranged from 0.0005 fibers/mL to 0.23 fibers/mL. The average detected asbestos concentration was 0.048 fibers/mL (note: fibers/mL and fibers/cc are interchangeable). These data represented a reasonable worst case and were used as a surrogate to estimate risk associated with other vehicles recovered from the WTC site.

Exposure Assessment The second part of the risk assessment process is the exposure assessment. In this step, the data that was collected during the hazard identification is used to determine the extent to which people might be exposed. The amount of risk depends on the amount of exposure. The exposure assessment component of the risk assessment (i) defines the human receptors of concern, (ii) identifies the exposure pathways, (iii) estimates exposure point concentrations, and (iv) estimates the average daily exposure. The average

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