The Center for Grassroots Oversight

This page can be viewed at

Follow Us!

We are planning some big changes! Please follow us to stay updated and be part of our community.

Twitter Facebook

Environmental Impact of 9/11 Attacks

USGS assessment of chemicals released during the collapse of the World Trade Center

Project: Environmental Impact of the 9/11 Attacks
Open-Content project managed by Derek, paxvector

add event | references

Scientists who work for the US Geological Survey watch the World Trade Center towers collapse on their television sets. “We sat at home, watched that gray-white cloud roll over Lower Manhattan, and knew damned well that the dust was going to hurt a lot of people,” Gregg Swayze, a USGS geophysicist, will later tell the St. Louis Post-Dispatch. “I knew we had the best technology in the world to determine precisely what was in that dust.” (Schneider 2/10/2002) Swayze and other USGS scientists quickly get to work making arrangements to use USGS and NASA equipment to determine the composition of the dust clouds (see September 12, 2001).

Roger Clark, the astrophysicist who heads the US Geological Survey (USGS)‘s portion of the AVIRIS program in Denver, contacts Robert Green, head of the AVIRIS program at NASA’s Jet Propulsion Laboratory in Pasadena. (The AVIRIS, or Airborne Visible Infrared Spectrometer, is a remote-sensing unit used by NASA to determine the chemical composition of a planet’s surface and atmosphere by analyzing the infrared signatures of minerals that are reflected from the ground and comparing them with the unique peaks and curves of the signatures of thousands of minerals and materials in the USGS database. (Schneider 2/10/2002) AVIRIS has been used before to scan Superfund toxic sites to map hot spots of harmful substances.) (Revkin 9/17/2002) He asks Green for NASA permission to use the AVIRIS over New York City and parts of New Jersey to determine the chemical composition of the dust and debris resulting from the collapse of the World Trade Center. (Schneider 2/10/2002) NASA gives the go-ahead on September 13 (see September 13, 2001).

Robert Green, head of the AVIRIS program at NASA’s Jet Propulsion Laboratory in Pasadena, informs Roger Clark, the astrophysicist who heads the US Geological Survey (USGS)‘s portion of the AVIRIS program in Denver, that NASA will permit the USGS team to use AVIRIS in an attempt to determine the chemical composition of the dust and debris that resulted from the collapse of the World Trade Center (see September 12, 2001). The crew will mount the unit to a de Havilland Twin Otter prop plane owned by NASA, which will make several passes over the WTC and surrounding area. “The Federal Emergency Management Agency and the White House Office of Science and Technology Policy… signed off on the flight. And the Air Force [has] agreed not to shoot the Twin Otter down,” the St. Louis Post-Dispatch will later report. (Schneider 2/10/2002)

NASA’s de Havilland Twin Otter propeller plane makes 14 passes over the region affected by the WTC collapse. The infrared-scanning AVIRIS unit, located underneath the plane, records infrared signatures of minerals reflected from the ground (see September 12, 2001). After the flight, the data tapes are sent to NASA’s Jet Propulsion Lab in Pasadena where NASA scientists Robert Green and Frank Loiza are waiting to review the data. The tapes arrive 2 a.m. the next morning. (Schneider 2/10/2002)

NASA scientists, Robert Green and Frank Loiza, perform the first analysis of the AVIRIS data (see 12:00 p.m. September 16, 2001-2:00 a.m. September 17, 2001) and determine that there are a total of 34 fires burning at the World Trade Center site with temperatures ranging from 800 degrees to 1,000 degrees. They pass this and all subsequent data to the White House and other government agencies that are involved in responding to the environmental impact of the attacks. (Schneider 2/10/2002)

US Geological Survey (USGS) geophysicists Gregg Swayze and Todd Hoefen fly to New York City to get calibration data from the ground that will supplement the data collected by AVIRIS (see 12:00 p.m. September 16, 2001-2:00 a.m. September 17, 2001). They collect 35 dust samples from a variety of locations around Ground Zero including window ledges, flower pots and car windshields. While “AVIRIS offers a bird’s-eye view…,” Roger Clark, a USGS astrophysicist, later explains to the St. Louis Post-Dispatch, “The ground samples… gave us up-close, specific information on specific points.” On September 19 they send their data to the USGS office in Denver over the Internet. The next day, scientists will begin conducting a variety of tests on the samples (see September 20, 2001). (Schneider 2/10/2002; Schneider 2/10/2002)

At the White House’s request, NASA’s de Havilland Twin Otter prop plane, equipped with the AVIRIS unit (see September 12, 2001), conducts additional flights over Manhattan (see 12:00 p.m. September 16, 2001-2:00 a.m. September 17, 2001), collecting data on the chemical composition of the dust and debris that was distributed throughout the city when the World Trade Center’s twin towers collapsed. (Schneider 2/10/2002)

US Geological Survey (USGS) scientists begin performing tests on the dust samples collected by USGS geophysicists, Gregg Swayze and Todd Hoefen, during the previous three days (see September 17, 2001-September 19, 2001-). Roger Clark (the astrophysicist who heads the AVIRIS program at USGS), Gregg Swayze, Todd Hoefen and Eric Livo (another USGS scientist) analyze samples in the Imaging Spectroscopy Lab and Gregory Meeker (head of the USGS’s microbeam laboratory) views samples with the scanning electron microscope and conducts energy dispersive spectroscopy. Other USGS scientists study the samples using X-ray diffraction, X-ray fluorescence, as well as chemical analysis and chemical leach testing. Within hours, the results from the various tests indicate the presence of asbestos and an “alphabet soup of heavy metals.” Each of the different techniques used to determine the chemical components of the dust “back each other up,” Swayze later explains to the St. Louis Post-Dispatch. “Some techniques can see more than others, and we were throwing in every technique we had in house,” he says. Tests revealed the dust to be extremely alkaline with a pH of 12.1 (out of 14). (Schneider 2/10/2002) and that some of it was as caustic as liquid drain cleaner. (Schneider 2/10/2002) “We were startled at the pH level we were finding,” Swayze adds. “We knew that the cement dust was caustic, but we were getting pH readings of 12 and higher. It was obvious that precautions had to be taken to protect the workers and people returning to their homes from the dust.” Sam Vance, an environmental scientist with the EPA, sends the results to officials at the EPA, the New York health department and US Public Health Service. (Schneider 2/10/2002)

After USGS scientists complete their analysis of the dust samples collected in New York City (see September 17, 2001-September 19, 2001-) —which found asbestos, an “alphabet soup of heavy metals,” and an extremely high pH level (see September 20, 2001) —the team emails the results to “all the government contacts the team had” including people at the EPA and FEMA, as well as to the federal emergency response coordinator. The EPA never informs the public of the dust’s high pH. “We anticipated that the results would have been shared with the people on the ground, those at risk, but it looks like the information never got to those who needed it,” Geoffrey Plumlee, a geochemist, will later tell the St. Louis Post-Dispatch. (US Geological Survey 11/27/2001; Schneider 2/10/2002; Schneider 2/10/2002; US Geological Survey 10/2002 pdf file) Some scientists will suggest that the dust’s high pH is a major cause of what will come to be known as the “WTC cough” (see September 9, 2002).

Creative Commons License Except where otherwise noted, the textual content of each timeline is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike