WTC.indd10/31/02, 11:25:54 AM1USGS Environmental Studies of the World Trade Center Area,New York City, afterSeptember 11, 2001T wo days after the September 11, 2001, attack on W

orld T rade Center (WTC), the U.S. Geological Survey (USGS) was asked by Smoke streaming from Ground Zero illuminates the night skyline of lower Manhattan in a view looking east from New Jersey . The photo was taken the night of September 16, 2001, by USGS fi eld-crew members T odd Hoefen and Gregg Swayze. the U.S. Environmental Protection Agency (EP A) and the U.S. Public Health Service to conduct a remote sensing and mineralogical characterization study of lower Manhattan around the WTC. This study

, conducted in cooperation with the National Aeronautics an

d Space Administration (NASA) and the Jet Propulsion Laboratory (JPL), was requested to rapidly provide emergency response teams

with information on the concentrations and distribution of asbestos and other materials in the dusts deposited around lower Manhatta

n after the September 11 WTC building collapse in New Y

ork City

. Preliminary results of the study were released via the internet to emergency response teams on September 18 and September 27, 2001. After September 27, additional work was done to fi ll remaining data gaps, and the study report underwent further detailed

peer review . The report was released to the general public via the internet on November 27, 2001. This fact sheet summarizes the res

ults of the interdisciplinary study; the full report can be viewed at http://geology

.cr .usgs.gov/pub/open-fi

le-reports/ofr

-01-0429/ .Study OverviewTheAirborneVisible/Infrared Imaging Spectrometer (AVIRIS), anaircraft-based remote sensing instrument, was flown by JPL/NASAover theWTC area on September 16, 18, 22, and 23, 2001.From September 16 through 19, 2001, a two-person USGS fieldcrew visted lower Manhattan to field calibrate theAVIRIS remotesensing data during daylight hours. On the evenings of September 17and 18, the field crew collected samples of dust and airfall debrisdeposits from 33 outdoor locations within a 1-kilometer radius of theWTC; this sampling occurred after a major rainstorm on September14.Two samples of indoor dust deposits unaffected by rainfall, andtwo samples of material coating a steel beam in theWTC debris closeto Ground Zero were also collected.Preliminary calibration and geo-rectification of theAVIRIS datawere done at JPL/NASAlaboratories in Pasadena. Calibration to surface reflectance, spectral mapping, and interpretation were done at theUSGS Imaging Spectroscopy Lab in Denver, Colorado.The dust, debris, and beam-coating samples were analyzed for avariety of mineralogical and chemical parameters using ReflectanceSpectroscopy (RS), Scanning Electron Microscopy with X-ray microanalysis (SEM), X-Ray Diffraction (XRD), chemical analysis, andchemical leach test techniques in other Denver USGS laboratories.

Photos by Mark Rushing.

in by the force of the collapse.

dows were left open or blown

rounding buildings where wincollapse, including inside sur

generated by the WTC building

Manhattan by the dust cloud

deposits were left in lower Extensive dust and debrisU.S. Department of the InteriorPrinted on recycled paperUSGS Fact Sheet FS-050-02U.S. Geological SurveyOctober 2002WTC.indd10/31/02, 11:26:09 AM2 ResultsHot Spots Identified in the World Trade Center Debris

A VIRIS images obtained from an airplane fl ying over the WTC complex were processed to indicate thermal hot spots, shown as bright red, orange, and yellow spots on the images to the left. The dark areas are shadows of buildings and other structures. The numbers show the original locations of T owers 1 and 2 in the WTC complex. The September 16, 2001 image (left) reveals a number of thermal hot spots in the region where the WTC buildings collapsed. Analysis of these data indicated temperatures greater than 800°F (orange pixels), with some areas reaching over 1300°F (yellow pixels). These results were released to emergency response agencies on September 18, 2001. By September 23 (right), most of these hot spots that were initially detected by A

VIRIS had been eliminated or reduced in intensity

.1221Materials Found in the Dust Deposits andBeam Insulation SamplesSamples of the dusts were analyzed using several different methods.All of the results indicate that the dust deposits formed fromtheWTC collapse are heterogeneous and are composed largely ofparticles of glass fibers, gypsum wallboard, concrete, paper, windowglass, and other miscellaneous materials commonly used in buildingconstruction or found in office buildings.The USGS detected chrysotile asbestos in more than two thirds ofthe dust samples studied, at levels less than 1 weight percent.Analyses of the material coating a steel beam in theWTC debris detectedthe presence of chrysotile asbestos at levels as high as 20 percent (byvolume) of the coating material.To date, the USGS has not detectedamphibole asbestos minerals in any of the dust or beam-coatingsamples, although small amounts of amphibole asbestos have beendiscovered by another group studying theWTC dusts.Agrowingbody of medical research indicates that chrysotile asbestos is lesscarcinogenic than amphibole asbestos, although this is still underdebate within parts of the medical community. of the dust samples. This photo illustrates the fl

uffy , heterogeneous nature500 micronsGlassfibersConcreteGlass shard Black and white scanning electron microscope images reveal the extremely complex makeup of the dusts on a microscopic scale. The length of the white bar on each SEM image indicates the scale.50 micronsConcreteGlass fiberChrysotileasbestosGlass fiber20 microns

Particles enriched in a variety of metals such as iron, lead (red arrows), zinc (white arrow), antimony

, and bismuth have been identified by SEM analysis. Many of these par

ticles are less than 1–2 microns in size, and can potentially be inhaled should the dusts be disturbed and become air

borne.WTC.indd10/31/02, 11:26:28 AM3Mapping Constituents Found in Dust Using AVIRIS Remote Sensing DataAVIRIS remote sensing measures the amount of light reflected from the ground surface in the visible through near-infrared spectrum. Individualminerals or other dust components have characteristic light reflection features across the visible and infrared spectrum, which can be used to map spatial variations in the materials making up the dusts deposited around theWTC. For further information about spectral theory, processing techniques,and applications, see http://speclab.cr.usgs.gov.

Asbestos An A VIRIS image from September 16th (left), keyed to the absorption and refl ectance features of chrysotile and other potential asbestos-forming minerals in the dusts, does not indicate widespread distribution of either chrysotile or amphibole asbestos in amounts above the detection limit of the instrument (3–5 percent). Instead, A

VIRIS mapping has identifi

ed isolated pixels or pixel clusters (each pixel is approximately 2 m by 4 m) where potential asbestos-forming minerals may occur in the area around the WTC (indicated as red spots on the image). In these areas, minerals that may be asbestiform may be present in concentrations of a few percent to tens of percent. Further fi eld sampling and laboratory analysis would be needed to confi rm the presence of these minerals, and to determine if they occur as asbestos. The white numbers in the upper

-central portion of the image indicate where T owers 1 and 2 stood in the WTC complex. Spatial V ariations in Dust Makeup The A VIRIS image at right shows spatial variations in the refl

ectance characteristics of concrete, gypsum, and iron-rich materials. The image indicates that the dust plume generated by the building collapse gener

ally traveled to the south-southeast from the WTC. It also shows that heavier , coarser materials with abundant concrete and steel (dark red and yellow pixels) tended to settle closer to the WTC than lighter

, fi ner particles composed of powdered gypsum wallboard, concrete, glass fi bers, and paper (dark blue, light blue, green, and orange pixels).1212WTC.indd10/31/02, 11:26:33 AM4 ResultsWhat Is the Chemical Makeup of the Dust Deposits?1010010001000010000071011121314 

# Alkalinity (mg/kg)pHSolid lye drain cleanerBaking sodaLiquid draincleanerLiquid bleachCement powderWTC indoordustsWTC outdoordustsMilk of MagnesiaCaustic alkalinityNon-caustic alkalinityThe chemical makeup of the dust samples, althoughquite variable, reflects the chemical contributions of materials used in building construction or found in buildings,such as glass fibers, concrete, gyspum wallboard, steelgirders, wiring, ductwork, electronics, computers, paper,and many others.The mean concentrations of some heavy metals in theWTC dust samples (such as antimony, molybdenum, zinc,copper, lead, chromium, manganese, nickel, and barium)are relatively high compared to their mean concentrationsin natural soils from the eastern United States.0.00000010.0000010.000010.00010.0010.010.1110100 

# Concentration in solid (percent)

Calcium

Magnesium

Sulfur

Iron

Aluminum

Organic Carbon

Carbonate Carbon

Sodium

Potassium

T itanium

Barium

Strontium

Zinc

Manganese

Lead

Phosphorous

Copper

Cerium

Yttrium

Chromium

Nickel

Lanthanum

Antimony

V anadium

Molybdenum

Lithium

Thorium

Rubidium

Cobalt

Niobium

Scandium

Uranium

Cadmium

Arsenic

Gallium

Beryllium

Silver

Cesium

Bismuth

Thallium

SiliconWTC sample rangeWTC sample meanEastern US soilmean The plot to the right compares the concentration ranges and mean concentrations of chemical elements in the WTC dusts (this study) to the mean concentrations of the same elements in soils from the eastern United States (other studies).Chemical leach tests were performed in which 1 part dust was mixed with 20 partswater and the resulting water solution analyzed.The results indicate that the dusts can bechemically reactive should they come into contact with rain or wash water, or moisturein the eyes, mouth, and respiratory system. Some metals in the dusts, such as aluminum,chromium, and antimony, are quite soluble.Any water or moisture that comes into contactwith the dusts initially becomes alkaline to caustic, due to the dissolution of calciumhydroxide from the concrete particles.This is especially true for indoor dust samplesthat have not been exposed to rainfall. Fortunately, continued reactions of water andatmospheric carbon dioxide with the dusts help to neutralize their caustic alkalinity.What Happens When the Dusts Come into Contact with Water? The plot at left shows the alkalinity and pH of the WTC dust samples and common household materials when all are diluted by 20 parts water

. The indoor WTC dusts, when added to water

, can generate high pH values and caustic alkalinity (composed of caustic, reactive hydroxyl ions). Howeve

r , the

in door WTC dusts do not generate as much caustic alkalinity as equivalent weights of cement, liquid drain cleaner , liquid bleach or solid lye drain cleaner

. In contrast, the outdoor WTC dusts generate somewhat lower pH values and smaller amounts of alkalinity that is mostly noncaustic (composed primarily of carbonate and bicarbonate ions).Implications for Dust CleanupAs stated in the initial USGS report to emergencyresponse workers on Sept. 27, 2001, the materials identified by this study in theWTC dust and debris (chrysotileasbestos, glass fibers, alkaline concrete particles, potentially soluble metals) indicate that cleanup of dusts andtheWTC debris should be done with appropriate respiratory protection and dust control measures.

For further information about the USGS study

, contact: Roger Clark(AVIRIS)

Geoff Plumlee(dust chemistry)(303)-236-1332, rclark@usgs.gov303) 236-1204, gplumlee@usgs.gov Greg Meeker(materials characterization)

Gregg Swayze(fieldsampling)(303) 236-3188, gmeeker@usgs.gov(303) 236-0925, gswayze@usgs.gov USGS, NASA/JPL study team:Roger Clark, Rob Green, Gregg Swayze, Greg Meeker, Steve Sutley, Todd Hoefen, Eric Livo, Geoff Plumlee,Betina Pavri, Chuck Sarture, Steve Wilson, Phil Hageman, Paul Lamothe, Sam Vance, Joe Boardman, IsabelleBrownfield, Carol Gent, Laurie Morath, Joseph Taggart, Pete Theodorakos, and Monique Adams Where T

o Get Health Information about the DustsThe USGS studies summarized here provide scientific information about the materialand chemical makeup of the dust deposits left by theWTC building collapse.This information, along with information provided by many other emergency-response studies and longterm monitoring studies, can be used by the medical community to help understand potentialhuman health effects that may result from exposure to dusts generated by the initial buildingcollapse, and from longer-term exposure to dusts remobilized during cleanup.There are a number of different web sites that provide health-related information ontheWTC collapse, such as: the U.S. EPA(www.epa.gov), NewYork Department of PublicHealth (www.nyc.gov/html/doh/home.html), and the Environmental and OccupationalHealth Sciences Institute (eohsi.rutgers.edu/wtc/index.shtml).The USGS and NASA/JPLteam members whoparticipated in this study respectfully acknowledgethe memory of the many who lost their lives intheWorld Trade Center attack; those injured; thefamilies and friends of those lost and injured;and the heroic efforts of the countless emergencyworkers, health care professionals, constructioncrews, scientists, and others who have made a difference on and since September 11, 2001.98