Q&A and FAQ regarding WTC response, Oct 2001

NYC 9/11 Public Portal Document

MAY-29-2002 21:25 U;S. EPA/DEPP 212 6373772 P.07/08

12. (Disorganized clcan-up resulting in re-contamination of previously cleaned areas)

Issue - Concern has been raised that the cleanup is disorganized and is resulting in cross­ contamination of previously cleaned areas.

Response - £PA is not aware of significant re-contamination of cleaned areas to date. The NYCDOH, with the assistance of ATSDR and EPA, is conducting indoor dust and air sampling for asbestos in buidings impacted by the WTC disaster to evaluate the effectiveness of apartmenthuiding cican-ups. The results of this study naay be able to provide information to evaluate the re-contamination issue.

13. (Cleanup using AHERA is not working)

Issue - EPA is trying to use the AHERA statute as the authority for i's cleanup. EPA is trying to adapt these insensitive test methods, the AHERA TEM clearance tejt for air, and the PLM test for % asbestos, to situations which were not intended by the regulations.

Response - EPA has riot used the AHERA statute as the authority for its cleanup. The authority for EPA actions at the World Trade Center is the Stafford Act and the Federal Response Plan. The microscopy methodology (TEM) prescribed by AHERA for airborne asbestos was used because it is more sensitive than PCM and is able to distinguish asbestos from non-asbestos fibers whereas PCM can not. As previously discussed, percent mesurements of asbestos in bulk materail by PLM were intended to inform regulatory concerns rather than serve as a measure of risk. Clean-up activities by EPA were conducted as part of its mission assignment in the Federally Declared Disaster. The AHERA standard was used as a benchmark to guage public health protectiveness in an emergency response situation.

14. (PCM-equivalent correction factor)

Issue - Risk assessments for asbestosis should be based on total TEM fiber counts rather than PCM equivalents because ATSDR has reviewed studies showing that asbestosis is associated with shorter asbestos fibers.

Response - The scientific literature indicates that asbestosis (diffuse interstitial fibrosis of the lungs) is associated with chronic, IJgh-dose exposure to asbestos. Hi'^./i ically, the asbestos analysis in occupational studies of highly exposed worker populations was performed by PCM, thereby providing limited Lifoimation on the role of short fibers in inducing asbestosis. Mechanistically, the ability of pulmonary macrophages to clear short fibers should make them less fibrogenic than longer fibers. The ATSDR Toxicological Profile for Asbestos (2000) states, “A number of animal studies have indicated that long fibers (5 urn or more) have a higher

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