EPA/DEP letter re: Validity of 114 Liberty Street test data,

NYC 9/11 Public Portal Document

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. EPA’s WTC Residential Confirmation Cleaning Study can be obtained at http://www.epa.gov/wtc.

Primarily, 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 regulatory-based and 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. The scope of work developed for the clean up activities was designed for the removal of debris from the collapse of the World Trade Center and did not include the removal or remediation of pre-existing building materials. As a matter of precaution, any residual dust and, thus, potential reservoirs of asbestos, from currently accessible areas should be cleaned using the technique of vacuuming and wet-wiping.

Asbestos containing materials (ACMs), such as floor tiles, were observed during DEP’s cleaning of the building. Some of the ACMs may be present under the hardwood flooring, thus samples collected from this location may be more representative of the building materials contained within the building rather than indicating contaminatios-from other sources. Additionally, DEP noted and reported the presence of thermal system insulation and damaged asbestos-containing fireproofing within the building. Building representatives were provided with this information and were informed of the provisions of Title 15, Chapter 1 of the Rules of the

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