Residential sampling protocol, World Trade Center, Oct 2001

NYC 9/11 Public Portal Document

(wtc residential plan oct18.wpd Page 2T)

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ASBESTOS Considerations for using the asbestos "1% rule" for cleaning up bulk contamination associated with the World Trade Center terrorists attacks.

Purpose: The purpose of this fact sheet is to discuss the basis of the 1% rule for asbestos containing material (ACM) and suggest how it may be applied to cleaning up asbestos contaminated debris from the World Trade Center coUapse. The intent is to provide guidance for the use of bulk sampling results that will be protective of public health.

Background: The definition of asbestos containing material was first found in the Asbestos Hazard Emergency Response legislation of the United States Code. The term "asbestos­ containing material" means any material which contains more than 1 percent asbestos by weight (see. United States Code, Title 15 - Commerce and Trade, Chapters 53 - Toxic Substances Control, Subchapter II - Asbestos Hazard Emergency Response, Sec. 2642. Definitions; which can be found at http://www4.law.comeU.edu/uscode/15/2642.html ).

This definition was codified in the Code of Federal Regulations (40 CFR Chi, Part 763 [7-1-00]) where a counting technique using polarized fight microscopy (PLM) is used to determine percent asbestos. % asbestos = (a/n) X 100% where a = number of asbestos counts, n = number of nonempty points counted (400), If a = 0, report “No asbestos detected”. If 0< a <5 report “<1% asbestos”.

Historical derivation of the definition of "asbestos containing material": Two different accounts of the discussions leading to the definition of asbestos-containing material containing greater than 1% asbestos exist were identified.

1) The first account suggest that in the late 197O's when EPA was looking at the different methods to examine bulk material for asbestos they considered several different methods including polarized light microscopy (PLM), electron microscopy, x-ray diffraction (XfRD), and others. EPA eventually settled upon XRD. XRD had a detection limit of approjumately 1% asbestos in bulk material. Eventually the limitations of XRD became an obstacle to reliable asbestos determinations and EPA looked toward PLM to replace XRD as the analytical tool of choice. However, even though PLM can detect well below 1% asbestos, the 1% number had become well accepted and had been written into legislation, and so therefore 1% remained the legally enforceable number.

2) The second account suggests that the 1% rule has a political basis and resulted as a

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