NYC-WTC_000209427

NYC 9/11 Public Portal Document

safe. Even higher levels could be considered safe at remote locations wrhere no one comes in contact with the material. The key to determining whether there is a risk is exposure. If there is no exposure pathway i.e., a way for the asbestos to get into your body, such as contact with the material, or people driving over the material so that they breathe in the fibers, there is no risk. Levels of 1 % or less could present a risk where there is enough activity to stir up soil and cause asbestos fibers to become airborne.

A research study found that soils containing as little as 0.001% asbestos can lead to hazardous air concentrations.'**

Suitable Action Levels ... Airborne dust clouds were generated from mixtures of soils with different asbestos varieties in bulk concentrations ranging from 1 to 0.001 % asbestos. ... The experiments showed very clearly that even the lowest bulk amphibole asbestos content tested (0.001%) was still capable of producing measurable airborne asbestos concentrations (greater than 0.01 fibers mL '

EPA always regulates toxic dusts on interior surfaces by the amount per surface area, not the % in a dust

Region 2 and the NYC DEP benchmark for asbestos dust inside buildings is flawed on its face just because it is based on a percentage, and not on a concentration per surface area. There are no EPA standards for dusts or other solid contaminants inside buildings that are expressed in terms of mass/mass or volume/volume, such as percent or parts per million. Instead, EPA sets safety standards based on the amount of solid toxic material on a given surface area for inside exposures. This is because that is the way exposures occw. Consider the following:

A child puts her tongue on a certain area of a window sill. Which is worse. Example A or B? A: The window sill has a layer of dust 1/100 inch thick. The dust is 0.5% lead. B: The window sill has a layer of dust 1/10,000 inch thick. The dust is 5% lead. Answer: Example A is worse, even though the absolute concentration of the lead in the dust itself is lower. The exposure, or the total amount of lead, is 10 time higher in Example A, even though the concentration of the lead in the dust itself is lower in Example A.

A room is covered with asbestos-contaminated dust. Children come into the room to practice gymnastics. The activity level is enough to stir up all of the dust on the floor causing it to be airborne, whether it is 1/1000 or even 1/10 inch thick. Which is worse. Example C or D? C: The floor is covered with 1/100 inch of dust containing 0.5% asbestos. D: The floor is covered with 1/10,000 inch of dust containing 5% asbestos. Answer: Example C is worse, since 10 times as much asbestos will become airborne in Example C compared to Example D, even though the concentration of the asbestos in the dust itself is lower in Example C.

The “surface concentration” is what is important for solid toxics like asbestos inside homes, businesses, and schools. The concentration of the asbestos in the dust itself is less relevant. What is important is the total amount of asbestos on a given surfaces. Although EPA does not have any regulati ons for the surface concentration of asbestos in interior dusts, it does have

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