2002 E-Mail Sent M. Gilsenan

NYC 9/11 Public Portal Document

I ------- 4. + I Tier I Screening Value Action I I +-------------------------- I I I > .162 ng/m3 {E-04 x 1 yr) aggressive cleaning I I (professional?) - if I 1 I readings persist take I I additional action to reduce I I exposure I I ----- +------------ J----------- ---------------------------- 1 I II I .0054 - .162 ng/m3 maintain recommended (i.e.. I I diligent wet/HEPA) cleaning I I methods - consider I I additional monitoring I I + I Ill I < .0054 ng/m3 (E-04 x 30 yr)1 no further action I I + +

* For illustration purposes only. With combustion by-products no longer being formed, Dioxin is unlikely to represent an inhalation hazard in the indoor environment. Dioxin in settled dust may represent a more significant hazard from incidental ingestion/dermal contact. The same approach would be used for dust substituting dioxin load/concentration (I prefer load) for airborne values.

For Monday's call we'll need to get consensus on the tiered approach and get down to the business of identifying exposure media (air,dust - load vs cone) and filling in numbers for COCs.

Finally, I've been having some side bar discussions with members regarding the use of "sentinel substances" as a means for guiding our efforts relating to additional sampling, level of cleanup, and need for follow-up monitoring. Bob Chinery has observed that fiberglass seems to be in high concentration wherever there are readily clearly impacted areas. The question is: can it serve as a reliable indicator for the handful of COCs we'll be dealing with? After speaking with a physician today about the persistently alkaline characteristic of WTC dust, I was thinking if pH might also be able to serve as type of sentinel for identifying significantly impacted dwellings. Anyway, consider this food for though and we'll discuss all of the above in more detail on Monday. Have a nice weekend.

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NYC-WTC_000139424