Internal routing form for WTC environmental documents, date unknown

NYC 9/11 Public Portal Document

As discussed previously, we have developed the clearance level (that is, the risk-based cleanup goal) to determine when cleaning can cease at a residence under the Indoor Air Residential Assistance Program - WTC Dust Cleanup. The development of this level has been consistent with the NCP. For example, under the NCP, removals performed either by EPA with Superfund monies or by responsible parties need to attain applicable or relevant and appropriate requirements (ARARs) “to the extent practicable considering the exigencies of the situation.” [Section 300.415(j) of the NCP] For the Indoor Air Residential Assistance Program - WTC Dust Cleanup there are not any directly applicable standards. So, as is a common practice in removal actions under the NCP, we have developed a risk-based clearance number for asbestos in air, taking into consideration other standards. We have consulted with peers in the scientific community regarding the use of this level as an extremely protective long-term risk guideline.

I do want to make you aware that achieving this level of high sensitivity in analysis, which will enable us to detect .0009 f/cc of asbestos in air, is a scientific challenge. To attain this low a detection limit in a technically practical manner, a large volume of air needs to be collected. This increases the potential for filter “overload.” Filter “overload” creates a problem because it impairs the ability of the microscopist viewing the sample results to see the entire field of vision under the microscope. Filter “overload” in asbestos testing terminology indicates that enough small specks of dust have been captured on the same filter to interfere. The microscope used for asbestos analysis in this program magnifies objects up to 20,000 times, so even the tiniest speck of dirt or dust can obscure small fibers of asbestos. EPA will perform ongoing evaluation of the sampling program as the cleanup progresses and may reduce sample volumes should filter “overload” become a routine occurrence. We will keep all members of the public informed of our results and any related issues.

Cleaning Program and Testing Methods

As you are aware, in early May, EPA, NYC and FEMA announced that direct assistance would be provided to residents of Manhattan living south and west of Canal, Allen and Pike Streets. This direct assistance program offers the residents in this area three options: 1) residents may have their homes professionally cleaned and sampled by licensed asbestos contractors; 2) residents may have their homes sampled for asbestos without cleaning; and 3) residents may be reimbursed for a vacuum cleaner equipped with a high efficiency particulate air filter for their own home use.

The cleanup program also includes both pre- and post-cleaning sampling at 200 of the residences cleaned and testing at 50 of the testing only apartments for dioxin, mercury and the target analyte list (TAL) metals. There are 23 metals on the TAL (aluminum, antimony, arsenic, barium, beryllium, cadmium, calcium, chromium, cobalt, copper, iron, lead, magnesium, manganese, nickel, potassium, selenium, silver, sodium, thallium, vanadium, and zinc).

We are testing for asbestos in air in the cleanup program based on the sampling data indicating that asbestos is the primary contaminant of long term exposure concern, as well as the fact that there is broad agreement among scientists on the sampling and measurement methods. The reason we are testing residences for dioxin, mercury and the TAL metals is primarily to

NYC-WTC_000151601