Memorandum on asbestos wipe sampling and cancer risk estimation, December

NYC 9/11 Public Portal Document

experimental study are given. Then, the conversion factors are estimated for WTC asbestos dusts.

Settled dust level conversion factors found from controlled study

A study was performed by Millette and Hays to provide a correlation between the level of asbestos in settled dusts and the amount which will become airborne^ (resuspended) as the lesult of certain activities. This study used real world situations of asbestos contamination, primarily after the San Francisco earthquake. Table 1 shows the experimental results, along with the calculated “K-factor”, the factor for multiplying the settled dust level by to find the air level. As can be seen, the air concentrations increase as the activity level increases.

I Table 1. Resuspensbn K-Faclors for settled asbestos dusts determined from controlled asbestos studies by Millette and Hays. ®

ACTIVITY SETTLED DUST AIR LEVEL K-FACTORS LEVEL structuresAnilliiter multlp^ the settled dust structuresZsquare (s/mL) level by this number to centimeter (s/cm’) get the air level I Carpet cieanhg 23.000 0.09 3.9x W® I (ordinary vacuum) (0.0000039 ) Broom Sweeping 760,000 53.6 7.1 X 10*® ( 0.000071 ) Cleaning Storage Area 870,000 2.7 3.1 X 10”® ( 0.0000031 ) Gym-Athletic Activities 9,700 0.23 2.4x10'® I (0.000024 ) I Cable Pull 2,000,000 28.9 1.4 x 10'® (0.000014 )

Resuspenslon factors for settled dusts from World Trade Center

The Millette and Hays study can be used to predict airborne levels of the WTC dusts. Data is ovailable fi-om the Ground Zero Task Force study for two apartment buildings.® Settled asbestos levels along with airbome^sbestos levels were measured under passive conditions. Estimations are then made of the fraction of the settled dust which will become resuspended.

The WTC dusts are unusual in that the particles of asbestos are smaller than usually, having a greater likelihood.of becoming resuspended.’ This appears to be the case. The actual measured fraction of asbestos that was suspended in air over settled dusts under passive conditions (no activities taking place to stir them up) were HIGHER than measured in the Millette and Hays study when a carpet was being vacuumed. It is reasonable and prudent to predict that if the WTC dusts were being vacuumed, the resuspension factor would be higher than actually measured under passive conditions, which means they would be higher than found in the Millette and Hays study. The resuspension factor for the WTC dusts have been predicted to be 10 times higher I under vacuuming conditions than under passive conditions, which is 10 times higher than found I I

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