Memorandum on asbestos wipe sampling and cancer risk estimation, December

NYC 9/11 Public Portal Document 1

also taking breaks at this adjacent hotel for another 3 hours a day. He is a smoker.

The levels of outdoor asbestos exposure during the firet 2.5 weeks exposure is estimated to be 500 sZmL. He is both in the open air and in confined spaces. This level is 100 times the highest level found by the HP Environmental study in passive conditions in two buildings damaged but still standing near the World Trade Center.” EPA did not have monitoring equipment in confined spaces, al though it did eventually on the perimeter of Ground Zero. OSHA does not appear to have had personal monitoring equipment on firefighters, only stationary monitor*ig in open areas around Ground Zero.

The level of outdoor asbestos exposure is estimated to be 0.50 s/mL during the second 2.5 weeks, al level consistent with many EPA readings at Ground Zero during the first month. Actually, there would have been a gradual decline of the initial 500 to 0.50 s/mL levels over the month, but the 2-time period per exposure level is convenient for calculations.

From Table 2, the asbestos level inside die contaminated building near Ground Zero is estimated to be 10 s/mL, midway between the “passive” conditions tested in the high-exposure building near Ground Zero, and the level estimated for cleaning out a storage loom.

s/mL X time period (years) total dose (s-year/mL) 500 (15/365)x(12C4) 10.2740 0.50 (15/365)x(12Z24) 0.0103 10 (30/365)x(12C4) 0.4110 total dose (cumulatr/e exposure) 10.6952

His increased risk is 1 in 30 for both mesothelioma and lung cancer. The firefighter has a risk of over 2/1000 for developing asbestosis, and would probably have abnormal radiological findings of the chest

LAB METHODS FOR ASBESTOS, WAYS OF REPORTING RESULTS

This section may be helpful for interpreting the many different ways that asbestos levels are measured analytically, and also the many different ways these levels are reported.

PCM methods for air anti bulk samples

The older method for measuring asbestos in air was by phase contrast microscopy (PCM). PCM measurements are reported as either structures/railliliter ( s/mL) or fibers/milliliter (f/mL). F CM cannot detect fibers and structures with diameters smaller than 0.5 micrometers (0.5 pm or 0.5 um). PCM cannot distinguish asbestos fibers fi-om non-asbestos fibers.

Thus, TEM measurements will give higher readings of asbestos fibers than PCM measurements if most of the fibers are actually asbestos, and if the asbestos fibers themselves have a significant I fraction that are smaller than 0.5 pm. In WTC dusts, all the data I have seen indicates that TEM I measurements are higher than PCM measurements of the same sample. I I I - 15-

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