Law Department notice on WTC document preservation, Oct 2001

NYC 9/11 Public Portal Document

reliably measured. The TEM analysis of asbestos data in response to the WTC disaster suggests that the minimum detection limit may now be approximately 15 to 20 s/mm2.

A significant issue with regard to indoor spaces was the potential exposure from asbestos in dust. In assessing the need for asbestos abatements in indoor spaces in New York City, the City relied on the NESHAP definition of asbestos-containing material, which defines asbestos-containing material as 1 percent or more asbestos by volume. This is not a health standard, and dust with less than 1 percent asbestos could pose a health risk. Risk assessors employ a mathematical formula to estimate the amount of asbestos in dust that can be expected to become airborne in order to evaluate the potential risk to human health from asbestos in dust. This factor is known as the “K Factor.” However, this factor is not deemed reliable at this time. The panel that completed the peer review for EPA’s indoor standards did not endorse the asbestos-settled dust benchmark because the “the K-factor methodology is, at this time, inadequate for predicting inhalation exposure fi-om asbestos surface loading measurement.”

We believe EPA should review the AHERA standard and determine whether the standard needs to be revised in light of the fact that better filters are available today, and continue the work of the indoor COPC group to develop health-related screening levels for asbestos in dust

Benchmarks for Exposure to Multiple Pollutants. The synergistic impacts of multiple pollutants on human health in the aftermath of an air quality emergency, such as occurred on September 11, are unknown. Synergistic effects have been documented between asbestos and cigarette smoke. For example, the lung cancer risk from exposure to asbestos is increased if the individual exposed to asbestos is a cigarette smoker. Researchers interviewed indicated that there could be other synergistic effects caused by the wide array of pollutants generated by the collapse of the WTC, but research is not available to make this determination.

114 Report No. 2003-P-00012

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