The RJ Lee Group World Trade Center (WTC) dust evaluation studies are believed to be the most extensive forensic building investigation ever performed. The impact of the explosions, fires, and energy produced by the collapse of the WTC Towers released dusts, particles, and vapors into the environment of a type that is unique to the WTC Event. RJ Lee Group analyzed several hundred thousand samples of evidence from multiple buildings both at the site and from encompassing areas, to create an irrefutable chemical signature of the disaster. Here is how we did it.


In April 2002, RJ Lee Group was first retained to oversee and investigate the presence, type, amount, and extent of environmental contaminants in buildings near the site of the WTC collapse and to recommend remediation strategies. To prove that the building had been contaminated with the fallout from the WTC collapse, we needed to be able to distinguish the WTC dust from normal background dust.


Our job was to collect samples (evidence), develop protocols for analysis, recommend a remediation program to include cleansing buildings for reoccupation, and provide an information stream of data to building owners, regulatory bodies, and civic and protective agencies. We had to determine not only how to proceed, but where to look for the evidence, how to sample it and how best to relay the results. As the world was watching, we needed to deliver not only the true data but irrefutable data that would stand up to any scientific scrutiny. Our job was made more difficult by the uniqueness of the event that included two major areas of concern: the dust created by the disaster, and the biological materials resulting from water damage and weather.

The collapse the WTC towers created a pressure cloud of finely pulverized dust and hazardous substances. Under the force of the collapse, this cloud moved towards the surrounding structures. The pressure cloud gathered wind speeds equivalent to an F3 tornado with enough energy to overturn large trucks. It forced its way through every conceivable pathway of the buildings whose HVAC ducts acted like a super highway for the transport of dust into electrical systems, stairwells, and elevator shafts, installed equipment, and light fixtures. Enough dust was deposited in one of the buildings to cover a football field to a depth of four inches. Ultimately, the dust cloud spread to obscure the entire southern end of Manhattan expanding the task at hand to make it even more complicated.

Attempts at remediating areas of mold concern were equally difficult. Without environmental controls, buildings were exposed to high humidity, condensation and outside temperature variations which led to the extensive growth of bacteria and mold. Cleaning of these building components was nearly impossible because of the interconnected nature of the interior walls. Removing these interconnecting components often caused them to be destroyed.


We had to understand the issues surrounding the WTC site so completely that the science would speak for itself, that it would be unquestioned, and that it would become factual evidence. We needed to mobilize quickly to determine the risk in collecting samples as well as site clean-up. This frightening “cocktail" of environmental contamination had never been seen before. It contained components from the planes, jet fuel, fires, standard building materials and electronics that had been pulverized into a fine dust that permeated everything. We needed to know how toxic the dust was, how safe the buildings were structurally, and if clean up would allow reoccupation of the buildings. In order to achieve a 95% confidence we had to collect 100,000 samples from a single location alone.

Having had experience in conducting precise, demanding studies, we were able to assemble manpower and resources to scale up to double our normal capacity for sample collection, processing and analysis. With 100 specially trained technicians ready to collect samples we were prepared to begin work as soon as the FDNY “unfroze" the area. However, within days we found human remains and the process was halted as the FDNY came in to escort the remains. We now realized that we had to treat the dust differently and worked with the FDNY, police, and the community to carefully sample the dust.

The regulations in place to protect our technicians and others entering the area were inadequate. The dust had been transformed into something never seen before. To have protective measures put in place, we needed to build a team of subject matter experts (SMEs) choosing them from our own internal staff as well as other internationally recognized experts. This “team" consisted of experts who knew how to treat individual problems related to failure analysis of steel beams and concrete, environmental experts, toxicologists, structural engineers and design engineers. This team, in addition to our laboratory capabilities, provided all the expertise and instrumentation necessary to develop the regimen that would protect anyone entering the area near the WTC site.

As the dust samples were being processed, our microscopists using electron microscopy were able to identify a unique “signature" or pattern of elements of toxic materials in the samples. The WTC signature dust contained chrysotile, mineral wool and gypsum, as well as partially burned or melted plastic (particles), and spherical particles of iron and silicates modified by exposure to high temperature. An important aspect of the characterization of this dust was the ability to distinguish it from “background dust", i.e., particulate matter that is typical in a normal office environment. With the discovery of the “WTC Dust Signature," we were able to reduce the complexity of the science to a single pattern that could be easily identified. We determined that the dust that was found as a pervasive contaminant in the buildings sampled was unequivocally coming from the WTC Event.

The work we did at the WTC site was some of our finest. We supported more than 100 technicians on site involved in sampling, processing and data collection, some of whom also liaised with city, federal and community organizations. More than 250 additional staff in laboratories in Pennsylvania and Washington state processed and analyzed samples. The workload and the circumstances surrounding the event were intensive and had a great emotional effect on our people. It took great effort to separate the science from the human impact and preserve evidence for the case with sound technical analysis. It required using no shortcuts and offering no presumptions, and having no agenda other than to be objective gatherers of facts. Facts that were not only defendable, but irrefutable.