World Trade Center asbestos situation memorandum, December 2001

NYC 9/11 Public Portal Document

%

Region I’s Technical Appendix for the Brookfield School System^^’ states the following;

The results ... of the fifty-one (51) Method D5755-95 samples were compared to the benchmark chosen by EPA based on the asbestos fiber levels found in ambient (outside) air measured by Transmission Electron Microscopy (TEM), within the range 0.01 - 0.045 fibers/structures per cubic centimeter (f/cc) [this is the same as structures per miiiiiiter, ors/mL]... In order to compare the benchmark levels from cubic centimeter(cc) to settled dust levels in square centimeter (cm2) and allowing for the aerodynamic properties of these fibers, a K-factormust be applied. After the application of the appropriate K-factor we calculated a benchmark of 45,000 structures per square centimeter (s/cm2).

EPA established benchmark levels of ambient (outside) air measured by Transmission Electron Microscopy (TEM) within the range 0.01 - 0.045 fibers/structures per cubic centimeter (f/cc)

More recent studies in which asbestos air and surface dust levels were measured by TEM have been used to calculate additional K-factors. Based on these controlled studies for reentrainment of settled fibers into air, the K-factor of 10-6 [ten to the minus six, or 0.000001] was used. As shown in Section 7.0, the 0.045 f/co corresponds to 45,000 s/cm2 after the application of the K- factor.

The problems with Region I's risk assessment are discussed below:

Region 1 misrepresentation of background air ieveis and safety ieveis

Region 1 knowing used a false value for the average or background level of asbestos in “ambient” outside air for its risk assessment. The level of0.045 s/mL came from the one, outlying hipest level found in an early 1983 study of outside air.^' There was actually a wide range of values, most of which showed no detectable asbestos whatsoever. This one high value of 0.045 s/mL was an outlier, the highest recorded. It could well have been measured near an asbestos mine or processing facility, or near a natural rock outcropping of an asbestos mineral deposit.

It is unconscionable for Region 1 to have used the 0.045 s/mL highest outlier value from the study. At a minimum, it should have used the mean (average) for all of the measurements, most of which showed no asbestos at all.

Since 1983, however, much more definitive studies with increased sensitivity have become available for background air levels. Region 1 should have used the peer reviewed level for ambient outside air from these more recent studies established by Ihe Agency for Toxic Substances and Disease Registry (ATSDR) of the Centers for Disease Control (CDC). The ATSDR is an authoritative source for this information for EPA, and is funded through EPA statutes to develop this information in a Toxicological Profile for Asbestos.^ The early 1983 study used by Region 1 was not even mentioned by the ATSDR.

-13-

NYC-WTC_000140149