Environmental Studies of the World Trade Center
area after the September 11, 2001 attack.
U. S. Geological Survey, Open File Report OFR-01-0429
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, Colorado
2Jet Propulsion Lab
Pasadena, California
3U.S. Environmental Protection Agency, Region 8
Denver, Colorado
4Analytical Imaging and Geophysics, LLC
Boulder, Colorado
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
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
(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)
Next section: continue to the Introduction, below.
Back to Table of Contents
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).
Next section: click on the link to Results of Imaging Spectroscopy
Mapping, below
Back to Table of Contents
Results of Imaging Spectroscopy Mapping
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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.
Back to Table of Contents
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.
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References
Acknowledgements
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