EPA draft letter to FEMA regarding 114 Liberty, July 2003

NYC 9/11 Public Portal Document

Location Matrix Sample Average Maximum Size Concentration Concentration (s/cm^) (s/cm^) All locations Wipe 11 595,937 4,327,650 Below floor Wipe 1 11,681 Wall Tracking Wipe 9 726,108 4,327,650 Below Light Wipe 1 8,652 Switch Blank Wipe 1 2,164 All Locations Microvacuum 16 284,488 1,115,570 Below Floor Microvacuum 10 369,830 1,115,570 Wall Tracking Microvacuum 1 15,058 I-beam Microvacuum 2 7,636 8,038 (ND) Column Microvacuum 1 8,038 (ND) Pipe Shaft Microvacuum 1 71,592 Front Office Microvacuum 1 743,552 Blank Microvacuum 2 803

ND= asbestos not detected The interpretation of these results is constrained by the scientific uncertainty regarding the potential for the measured concentrations in settled dust to become airborne. There are no standards currently available for assessing potential health consequences from asbestos through the evaluation of wipe or microvacuum samples. A scientific peer review panel (World Trade Center October 21- 22, 2002 Peer Review Meeting Notes. Available at www.tera.org.) recently evaluated the technical soundness of estimating airborne asbestos concentration as a function of asbestos concentration in settled dust for the purpose of setting health-based benchmarks. The panel recommended against such an approach based on the significant uncertainty associated with the numerous factors (such as activity patterns, sample location, surface characteristics, air exchange rates and room volume) that influence this relationship. EPA’s use of surface wipe and microvacuum sampling at its WTC Residential Confirmation Cleaning Study site (110 Liberty St) was intended to provide a measure of cleaning effectiveness, and not a risk-based health assessment. Risk from asbestos is directly related to its concentration in air. Consequently, post-cleaning aggressive (i.e., use of a leaf blower and fans) air sampling was conducted at 114 Liberty St. by DEP’s contractors to insure that asbestos levels in air met risk-based clearance criteria. The EMSL analytical report does not provide detailed information on sample collection, however, it appears many samples were collected from inaccessible areas below the hardwood flooring, or from areas of unknown accessibility such as wall tracking, pipe shafts and I-beams. As a matter of precaution, any residual dust and, thus, potential reservoirs of asbestos, from accessible areas should be cleaned using the technique of vacuuming and wet-wiping.

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