NYC-WTC_000209427

NYC 9/11 Public Portal Document

Table 2. TYPICAL ASBESTOS DUST LEVELS INSIDE BUILDINGS^^ Levels of asbestos found from testing of a large number of interiors with or without asbestos building materials and/or asbestos contamination problems

structures per square centimeter (s/cm^)

“BACKGROUND” - If “background” is defined as the level in a building less than 200 where there are no asbestos containing building materials, then background should be considered to be at or below 200 s/cm‘\ Testing of three government buildings in Maryland with no asbestos containing materials showed levels below 200 s/cm^.

A western state building with no asbestos containing materials had even lower less than 160 levels, an average mean concentration of 160 s/cm^.

“RECENTLY CLEANED HARD SURFACES” - Buildings with asbestos 86 to 320 containing materials where hard surfaces had been recently cleaned.

“LOW” - Average of a wide range of measurement (6.5 to over 4.3 million 1000 s/cm^) for buildings with asbestos containing materials. This level was described as “low," but not “background." See the earlier entry in this table for levels inside buildings where no asbestos containing materials are used. If “background" is defined as the levels found in buildings not containing asbestos materials, then the “low" level of 1000 stem^ is high in comparison.

“ABOVE BACKGROUND” - Levels that are considered to be definitively 10,000 above background

“HIGH” - Levels considered high and “in the range of a significant accidental 100,000 release from an abatement site"

Appendix B shows that if a person were exposed over a lifetime to this level, the risk of cancer would be more than 2 in 1000. The AHERA TEM clearance test is also erratic and not reproducible, and the failure to use full aggressive conditions (leaf blower directed at all surfaces) can result in abnormally low readings. Thus, the use of K-factors, combined with the results of an ultrasonication test of carpet, or the ASTM 5755 microvacuum method for smooth surfaces, may provide a rough indicator of a potential for hazardous exposures.

As discussed in the following section, EPA’s Region 1 also uses these K-factors as a way of estimating asbestos air concentrations from settled dust levels. However, the values Region 1 inserted into the K-factor risk assessment formula were questionable for its year 2000 Brookfield, Connecticut School System risk assessment.

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