World Trade Center asbestos situation memorandum, December 2001

NYC 9/11 Public Portal Document

Table 3. ATSDR AIR LEVEL FINDINGS COMPARED TO LEVEL CHOSEN BY REGION 1

Background ambient air levels are from studies determined to be the most credible by the ATSDR®*

Concentration in TEM Equivalent concentration in structures per milliliter PCM fibers per milliliter (s/mL). This includes all (PCM f/mL). PCM fibers asbestos fibers and are only those single fibers bundles of fibers, and so which are longer than 5 is higher than “PCM” micrometers with a certain fibers. aspect ratio.

expressed as expressed as exponential exponential

ATSDR finding: outside air, rural, no 0.00001 (1 X 10’®) 0.0000002 (2x 10’^) known source of asbestos contamination nearby

ATSDR finding: outside air, urban, no 0.0001 (1 X W^) 0.000002 (2x10-®) know source of asbestos contamination nearby

ATSDR finding: 1988 EPA survey of 94 0.006 (6x 10’’) 0.0001 (1 X 10-^) public buildings containing asbestos materials, mean concentration

ATSDR finding; 1988 EPA survey of 41 0.03 (3 X 10’2) 0.005 (5x 10"*) schools containing asbestos materials, mean concentration

AHERA TEM clearance test level, the “70 0.02 (2 X 10-2) 0.01 (1 X 10-®) structures per square centimeter” level, approximately converted to s/mL and PCM equivalent f/mL. This is an unsafe level for long term exposures.®®

Region 1 level for background outside air, 0.045 (4.5 X 10'2) unknown used for risk assessment

Region 1 failed to use real-world background dust levels

There was no reason for Region 1 to have gone through any calculation process to project background dust levels from air levels. Typical background dust levels are well established, just like typical air levels.

Region 1 chose to ignore the fact that the same reference®® they used for K-factors also contained real world data for typical dust levels, which are widely recognized by industrial hygienists and other asbestos abatement specialists. See Table 2 for typical dust levels for buildings with or without asbestos contamination problems. Compare 200 s/cm^ a real world background level for buildings that do not contain asbestos materials, with Region I's calculated level of45,000 s/cm^.

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