Asbestos Sampling Post 9/11

Sep 18, 2019

Last week, Americans across the country remembered the 18th anniversary of the attacks that occurred during 9/11. These attacks not only killed thousands of Americans in the initial strike but also created environmental conditions that continue to affect citizens exposed to the toxic dust of the World Trade Center collapse to this day. In this blog, we will discuss the asbestos testing methodologies used during the clean up of the World Trade Center debris. 

World Trade Center Asbestos Background

The World Trade Center’s twin towers finished construction in the early 1970s, well before the bans for asbestos-containing materials later on in that decade. During this time asbestos may have been present in various materials such as floor tile for offices, thermal system insulation for mechanical areas, fireproofing materials, and various materials that would have been used during this time period that are asbestos-containing. The World Trade Center twin towers contained 110 floors each prior to their destruction, with many of those floors potentially containing some form of asbestos. 

Sampling Methodologies

After the collapse, the EPA contacted sampling of between a 5-12 mile radius to look for Containments of Potential Concern (COPCs) which included a variety of containments such as asbestos, lead, PAHS, silica, and a variety of other containments. The EPA used air sampling and dust sampling methods to determine the amount of asbestos contamination throughout the island of Manhattan. The testing involved collecting sampling inside of buildings and outdoor utilizing Phase Contrast Microscopy (PCM) air sampling, Transmission Electron Microscopy (TEM) air sampling, and dust sampling. The PCM method is a fiber counting method that does not differentiate between asbestos and non-asbestos, only fibers of the same size. The TEM method air sampling method can actually identify the asbestos fibers present using electron microscopy to determine the composition of the fibers. The TEM dust sampling using a TEM cassette used for air sampling and converts it into a micro vacuum to sample porous materials.


From this information, the EPA was able to gather data on the asbestos present in the island of Manhattan and develop protocols for cleaning and abating asbestos dust from residential dwelling areas. The research showed elevated levels were found primarily in common areas inside of the residential dwellings vs other areas of homes. The testing completed also detailed the levels of Dioxin and other containments found. One interesting finding was the high alkalinity of the dust discovered due to the drywall.


In conclusion, the destruction of the World Trade Center caused environmental contamination in the surrounding area due to disturbing the lead, asbestos, and other toxins present. The toxins released cause respiratory illness for many of the first responders and survivors of this tragedy. The full extent of those affected is hard to determine due to the long latency period of the asbestos based illnesses of 10-40 years. The asbestos testing methodologies used by the EPA are common sampling methods that we also use at Indoor Science. For more information about these methodolgies please look at our previous blogs on asbestos air sampling and dust sampling. To look into the EPA report, follow the link.