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|Open-File Report 01-0429                                                

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## Environmental Studies of the World Trade Center area after the September 11, 
2001 attack.

Version 1.1

Published November 27, 2001

Roger N. Clark1, Robert O. Green2, Gregg A. 
Swayze1, Greg Meeker1, Steve Sutley1, Todd M. 
Hoefen1, K. Eric Livo1, Geoff Plumlee1, Betina 
Pavri2, Chuck Sarture2, Steve Wilson1, Phil 
Hageman1, Paul Lamothe1, J. Sam Vance3, Joe 
Boardman4 Isabelle Brownfield1, Carol Gent1, 
Laurie C. Morath1, Joseph Taggart1, Peter M. 
Theodorakos1, and Monique Adams1

___________1U. S. Geological Survey, Denver, 
Colorado2Jet Propulsion Lab Pasadena, 
California3U.S. Environmental Protection Agency, Region 8 Denver, 
Colorado4Analytical Imaging and Geophysics, LLC Boulder, Colorado

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|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 
        SummaryIntroduction
        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 MapSample 
        Collection in the WTC AreaLaboratory 
        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 implicationsIntegration 
        of Results and ConclusionsReferences
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### Executive Summary

This web site describes the results of an interdisciplinary 
environmental characterization of the World Trade Center (WTC) area after 
September 11, 2001.

Information presented in this site was first made available 
to the World Trade Center emergency response teams on September 18, 2001 
(Thermal hot spot information), and September 27, 2001 (maps and compositional 
results).

The Airborne Visible / Infrared Imaging Spectrometer 
(AVIRIS), a hyperspectral remote sensing instrument, was flown by JPL/NASA over 
the World Trade Center (WTC) area on September 16, 18, 22, and 23, 2001 (Link to the AVIRIS JPL data facility). A 
2-person USGS crew collected samples of dusts and airfall debris from more than 
35 localities within a 1-km radius of the World trade Center site on the 
evenings of September 17 and 18, 2001. Two samples were collected of indoor 
locations that were presumably not affected by rainfall (there was a rainstorm 
on September 14). Two samples of material coating a steel beam in the WTC debris 
were also collected. The USGS ground crew also carried out on-the-ground 
reflectance spectroscopy measurements during daylight hours to field calibrate 
AVIRIS remote sensing data. Radiance calibration and rectification of the AVIRIS 
data were done at JPL/NASA. Surface reflectance calibration, spectral mapping, 
and interpretation were done at the USGS Imaging Spectroscopy Lab in Denver. The 
dust/debris and beam-insulation samples were analyzed for a variety of 
mineralogical and chemical parameters using Reflectance Spectroscopy (RS), 
Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), chemical analysis, 
and chemical leach test techniques in U.S. Geological Survey laboratories in 
Denver, Colorado.

|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 
        800oF in these hot spots (some over 1300oF) . 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 (http://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)
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Next section: continue to the Introduction, below.

Back to 
Table of Contents

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### Introduction

The information in this report describes the results of an 
interdisciplinary environmental characterization of the World Trade Center (WTC) 
area following requests from other Federal agencies after the attack on 
September 11, 2001. The scientific investigation included two main aspects: 1) 
imaging spectroscopy mapping of materials to cover a large area around the WTC 
and 2) laboratory analysis of samples collected in the WTC area.

Spectroscopy is a tool that detects chemical bonds in 
molecules (solid, liquid or gas) through absorption (or emission) features in 
the spectrum of the material. Imaging spectroscopy obtains a spectrum for every 
spatial pixel in an image format. Data from the Airborne Visible/Infrared 
Imaging Spectrometer (AVIRIS) were collected over the WTC area by NASA/JPL for 
this study. The results of the imaging spectroscopy mapping are shown below.

The analytical techniques applied to this study include 
X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) with elemental 
analysis by Energy Dispersive Spectroscopy (EDS), laboratory Reflectance 
Spectroscopy (RS), leachable metals, and X-Ray Fluorescence Spectroscopy 
(XRF).

For definitions of asbestos, CLICK HERE(use the back button on your browser to return here).

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Next section: click on the link to Results of Imaging Spectroscopy 
Mapping, below

Back to 
Table of Contents

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|Results of 
      Imaging Spectroscopy Mapping
      Click on the link above to see:
      Thermal Hot Spot Maps: Sept 16 and 23, 2001Asbestiform Minerals MapDust and Debris Plume MapFerrous and Ferric-Bearing Materials MapClays and other Materials MapOrganic Compounds MapWater Sediment Map
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Table of Contents



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Sample 
Collection in the WTC Area

link to Sample Collection in the WTC Arealink to Sample Collection in the WTC Area

Ground sampling consisted of collecting debris from 35 
locations in the WTC area, including 33 dust, 2 concrete, and 2 steel beam 
insulation samples.

Optical photographs of a typical dust sample on the left 
(sample WTC01-27) and what appeared to be an insulation coating from a steel 
beam on the right (WTC01-8). The coating contains as much as 20% chrysotile 
asbestos. Scale bar is 10 millimeters.

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Back to 
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### Laboratory Studies of Samples

#### Overview

The objective of the laboratory analysis was to characterize 
the samples for potential environmental impacts and to provide feedback to 
imaging spectral analysis and field confirmation of the imaging spectroscopy 
results. In certain cases the laboratory studies provide better detection levels 
than airborne imaging spectroscopy, thus providing complimentary information 
that allowing a more robust characterization of the entire site.

|X-Ray 
        Diffraction (XRD) AnalysisLaboratory 
        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 InterferenceScanning 
        Electron Microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDS)Chemical 
        Compositions
        Sampling and analytical methods
          Chemistry 
            Table 1,
          Results
          InterpretationLeachate 
        Studies
        Leaching of World Trade Center dusts using a simulated 
          precipitation leaching procedure
          Results
          Leach 
            Table 1
          Interpretation
          Summary and potential environmental implications
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

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### Integration 
of Results and Conclusions

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#### References

#### Acknowledgements

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      SurveyURL: 
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