Environmental assessment report, 100 Church Street, April 2002

NYC 9/11 Public Portal Document

4.4.4 Total Particulate Matter Samples and Results Twenty-eight (28) samples were collected from inside computers and related equipment and analyzed for total dust. The results of this sampling are presented in Table 8 in Appendix A. Samples were collected of dust present inside the computers to determine the extent of dust accumulation. A sample was also collected from a TRC West 29* Street New York office computer to represent background control concentration of dust present in a computer. As can be seen from Table 8, only one sample was found to be higher than the control sample taken from TRC’s office.

Sampling Methodology Sampling was conducted utilizing a 37-millimeter filter cassette with a 5 micron PVC filter attached to an air sampling pump. A short piece of tygon tubing was attached to the end of the cassette to micro.vacuum a measured surface area to collect dust present on the internal computer components. Analysis of the filter was via gravimetric analysis following NIOSH Sampling and Analytical Method 0500.

4.4.5 Dioxin Wipe Sampling and Results Table 9a in Appendix A presents the sampling and results for dioxin. Dioxins were detected in low concentrations in fourteen (14) of the twenty (20) wipe samples collected. TRC incorporated these results into a site specific human health risk assessment to determine the risk associated with the concentrations found at 100 Church Street. TRC conducted this risk assessment following United States Environmental Protection Agency (USEPA) protocols. A conservative, that is a highly protective, estimate of risk of cancer associated with the dioxin wipe and air concentrations was found to be 8.5E-07 (or 8.5 in ten million) which is less than (i.e., better than) the target cancer risk level of one in one million. The human health risk assessment calculations and assumptions can be found in Appendix B of this report.

These results notwithstanding, the NYCLD space was re-cleaned in an effort to remove any residual dioxin from surfaces. As each floor is re-cleaned, TRC is resampling surfaces for dioxin.

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