Table of Contents

Navigating through this report: At the end of each section will be a link to the next section in the sequence below, or click on the links to go directly to a section or sub-section.

• Executive Summary
• Introduction

  Asbestos Definitions.

• Imaging Spectroscopy Mapping Results

  Field spectral measurements and calibration site.

  Thermal Hot Spot Maps: Sept 16 and 23, 2001

  Asbestiform Minerals Map

  Dust and Debris Plume Map

  Ferrous and Ferric-Bearing Materials Map

  Clays and other Materials Map

  Organic Compounds Map

  Water Sediment Map

• Sample Collection in the WTC Area
• Laboratory Studies of Samples

  Overview

  X-Ray Diffraction (XRD) Analysis

  Laboratory Reflectance Spectroscopy (RS) Studies

  Reflectance Spectroscopy

  Laboratory Spectra of WTC Samples

  Description of Spectroscopy Methods and Results

  Possible Sources of Abestos in the WTC Dust

  Spectral Detectability of Chrysotile

  Spectral Interference

  Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDS)

  Chemical Compositions

  Sampling and analytical methods

  Chemistry Table 1,

  Results

  Interpretation

  Leachate Studies

  Leaching of World Trade Center dusts using a simulated precipitation leaching procedure

  Results

  Leach Table 1

  Interpretation

  Summary and potential environmental implications

• Integration of Results and Conclusions
• References

Results of these studies to date lead to several important conclusions:

• The dusts released from the WTC building collapse are largely composed of particles of glass fibers, gypsum, concrete, paper, and other miscellaneous materials commonly used in building construction.
• Laboratory analyses (RS, SEM, XRD) have detected chrysotile asbestos only in trace levels (less than 1 weight percent) in over two thirds of the dust and airfall debris samples. To date, no amphibole asbestos minerals have been detected in any of the dust samples. For definitions of asbestos, CLICK HERE (use the back button on your browser to return here).
• Laboratory analyses of the material coating a steel beam in the WTC debris have detected the presence of chrysotile asbestos (a serpentine mineral) at levels as high as 20% (by volume) of the coating material. No amphibole asbestos has been detected in this beam coating material.
• AVIRIS mineral maps do not show widespread distribution of chrysotile or amphibole asbestos at the few-percent detection limit of the instrument at the ground surface. AVIRIS mapping keyed to the detection of minerals that may occur in asbestiform habits has identified isolated pixels or pixel clusters (each pixel is approximately 2m x 2m) in the area around the WTC. In these areas, potentially asbestiform minerals might be present in concentrations of a few percent to tens of percent. Some spectral absorption strengths in the AVIRIS data are similar to those observed in spectra of the chrysotile asbestos-bearing beam coating. The absorption features mapped by AVIRIS only indicate the presence of serpentine mineralogy and not if the serpentine has asbestos form. Non-asbestiform serpentine minerals can occur naturally in rocks and such rocks may have been used in building materials. The AVIRIS maps could indicate areas of higher concentrations of asbestos or simply areas of non-asbestiform mineralogy and would need field sampling and laboratory analysis to confirm the presence of any asbestos. The AVIRIS maps show the surface materials only and not any buried materials.
• AVIRIS mineral maps show a few isolated pixels of amphibole minerals, but these pixels are isolated with no clusters like those seen in the chrysotile pixels. The few mapped amphibole pixels are at a statistical noise level in the WTC area similar to the pixel noise level mapped throughout the city. The absorptions mapped by AVIRIS only indicate the presence of amphibole mineralogy, which can occur naturally (non-asbestiform) in rocks that are used in building materials, and field sampling of those pixels would be necessary to confirm the presence of asbestos. The AVIRIS maps of serpentine chrysotile and amphibole mineralogy are consistent with laboratory analyses of the field samples.
• Laboratory analyses and the AVIRIS mapping results indicate the dusts are variable in composition, both on a fine scale within individual samples and on a coarser spatial scale based on direction and distance from the WTC. Replicate mineralogical and chemical analyses of material from the same sample reveal variability that presumably is due to the heterogeneous mixture of different materials comprising the dusts. The spatial variability is observed at large scales of tens of meters to centimeter and smaller scales. AVIRIS mapping suggests that materials with higher iron content settled to the south-southeast of the building 2 collapse center. Chrysotile may occur primarily (but not exclusively) in a discontinous pattern radially in west, north, and easterly directions perhaps at distances greater than 3/4 kilometer from ground zero.
• Although only trace levels of chrysotile asbestos have been detected in the dust and airfall samples studied to date, the presence of up to 20 volume % chrysotile in material coating steel beams in the WTC debris, and the potential areas indicated in the AVIRIS mineral maps indicates that asbestos can be found in localized concentrations.
• Chemical leach tests of the dusts and airfall debris samples indicate that the dusts can be quite alkaline. When reacted with rain water or wash water from cleanup efforts, the dusts can produce slightly alkaline to very alkaline solutions, due to partial dissolution of concrete, gypsum, and glass fiber particles. Indoor dust samples generated the highest pH levels (11.8) in the leach tests, indicating that dusts that have not been exposed to rainfall since September 11th are substantially more alkaline than those that have been leached by rainfall.
• At least some heavy metals and metalloids (such as aluminum, chromium, antimony, molybdenum, and barium) are readily leached from the dusts into rain or wash water. Indoor dust samples showed greater proportions of leachable metals than outdoor dust samples. These metals may also be potentially bioavailable if the dusts are accidentally inhaled or ingested. Chemical leach tests of the material coating steel girders in the WTC debris indicate that the coatings can contain soluble chromium.
• AVIRIS data collected on September 16, 2001, revealed a number of thermal hot spots in the region where the WTC buildings collapsed. Analysis of the data indicated temperatures greater than 800^oF in these hot spots (some over 1300^oF) . Over 3 dozen hot spots of varying size and temperature were present in the core zone of the WTC. By September 23, most of these fires that were observable from an aircraft had been eliminated or reduced in intensity.
• Our finding that trace levels of asbestos are present in the dust samples is consistent with results of other studies carried out by the U.S.Environmental Protection Agency (www.epa.gov). Our results provide further clarification by showing that 1) elevated concentrations of asbestos may be present in beam coatings and possible localized area as indicated by the AVIRIS maps, and 2) asbestos in the dusts and beam coating materials is composed only of chrysotile asbestos and does not contain amphibole asbestos. A significant body of research conducted over the last twenty years by toxicologists, epidemiologists and mineralogists has indicated that chrysotile asbestos is less carcinogenic than the amphibole asbestos minerals (Ross, 1999; Skinner et al., 1988; Van Oss et al., 1999; McDonald, 2001). This conclusion, however, has not been universally accepted by the scientific community. A recent and thorough discussion of these ongoing issues can be found in Nolan, et al. (2001).
• Results of our mineralogical characterization studies, chemical leach tests, and AVIRIS mapping provide further support for the EPA and New York Department of Public Health recommendations that cleanup of dusts and the WTC debris should be done with appropriate respiratory protection and dust control measures. These results include: the presence of up to 20 volume % chrysotile in material coating steel beams in the WTC debris (which could be unintentionally released into the air as dust during cleanup); the small areas in the AVIRIS mineral maps indicating that asbestos might be found in localized concentrations in the dusts; the highly alkaline nature of the dusts; and, the presence of potentially bioavailable metals in the dusts.
• For information on the health aspects of the dusts, readers are referred to web sites of the EPA: (http://www.epa.gov) and New York department of Public Health: ( http://www.nyc.gov/html/em/health.html, and http://www.nyc.gov/html/doh/html/alerts/911.html)

U.S. Department of the Interior | U.S. Geological Survey
URL: <http://pubs.usgs.gov/of/2001/ofr-01-0429/>
Questions or Assistance: Contact USGS
Page Last Modified: Fri Dec 16 17:28 EDT 2005