NYC-WTC_000234740

NYC 9/11 Public Portal Document

DRAFT

The collection of microvac or wipe asbestos samples is not an approved sampling method for asbestos. Individuals are not trained or certified in the collection of these samples. Thereby, the collection of these samples is not standardized and limits the ability to reproduce the results. Further, the New York State Department of Health Environmental Laboratory Accreditation Program does not certify laboratories for the performance of the sample analyses.

The lack of approval for these methods is based on the limitations for these methods and concerns regarding their applicability, evaluation, and interpretation.

1. The ASTM D5755 document indicates the following limitations: 5.1.1 This test method does not describe procedures or techniques required to evaluate the safety or habitability of buildings with ACM or compliance with federal, state or local regulations or statutes. 5.1.2. At present, a single relationship between asbestos containing dust and potential human exposure does not exist.

2. Asbestos fibers are an inhalation hazard and there has been no direct correlation reported between settled dust and airborne levels. It can be inferred that higher settled dust levels have the potential to lead to higher airborne levels, but without a direct correlation, these levels would be based on supposition. The use of aggressive (e.g. air circulating fans during sampling) TEM air samples would be more appropriate in determining public risk.

3. The screening values are set with 1,000 17cm’ or the background. The background level using microvac sampling is unknown. For practical purposes the screening value is therefore being set at 1,000 I7cm’.

4. The basis of the 1,000 f/cm^ appears to be the analytical sensitivity for the ASTM microvac sampling methodology. (ASTM D5755 §16.8- “An analytical sensitivity of approximately 1000 asbestos structures/ cm’ [calculated for the detection of a single asbestos stmcture] has been designed for this analysis”). This is parallel to the discussions and criticisms of the current standards.

5. When determining the background, the presence of inplace ACM and the history of ACM usage in the building must be obtained. Of particular concern, the clearance for re-occupancy after an asbestos project has not included microvac sampling. We do not know what level will be found at these sites when compared to buildings constructed without ACM.

Bulk sampling for asbestos containing material requires the collection of a sample about “the size of a penny”. The concern regarding the use of microvac or wipe sampling methods is therefore in areas where less material than “the size of a penny” is present or where air sampling does not disclose levels above the clearance levels for re-occupancy after an abatement project?

CITY_21MC100_008755804

NYC-WTC_000234740