World Trade Center/Twin Towers Case Study

Paul Weihe, Central College ()

On September 11, 2001, civilian planes in flight were forcibly taken, and used as weapons to attack landmark buildings in the United States. Ever since, I have used the attack on the World Trade Center (WTC; lower Manhattan, New York City) as a case study in my Environmental Science class. It has been over a decade since the attack, and although now a historical rather than current event, my students are quite familiar with the events of that day, and are able to participate in a class discussion. I use this as a lead-off “real-life example” the first day of class, but we consider the event from a risk management aspect, with a specific consideration of indoor air quality, so it could be incorporated in units on those topics. The discussion is accompanied by a PowerPoint with relevant photos, obtained from a Google Image search (I own none of the photos).

I begin by showing the iconic image of the burning Twin Towers, and asking how many students are familiar with the event (answer: essentially everyone). I then ask a simple question: “Why did the WTC Twin Towers fall?”

I usually have to wait for a moment; the students wonder about such an obvious question. Someone volunteers: “because they were hit by airplanes.” I then acknowledge that the response makes sense, but state that it is not truly accurate…in fact, the architects built the towers to withstand an aircraft strike…they knew it could happen…in fact, it already HAD happened, and only a short distance away! I show two photos of the aftermath of a US bomber plane striking the Empire State Building in a 1945 accident. The architects of WTC were only too familiar with the hazard.

So…the architects designed the building to withstand the aircraft impacts, AND THEY DID. In fact, both Towers stood for over an hour before collapsing. So, to repeat my question: “what caused the buildings to fall?”

Now the students get it. Someone quickly responds, “burning aircraft fuel made the building weaken,” or something similar. I affirm that this is more accurate…the collapse was really about the fire. I then show an ad from 1981 for Asbestos, featuring the WTC towers. I mention that Asbestos was a commonly-used fire-proofing material, and was used in WTC construction until the 64th floor, and then they switched over to a different material. Question: any idea why the use of Asbestos was abandoned there (and elsewhere)?

Many students have at least heard that Asbestos can damage the lungs. Some students may know that it is an irritant (the fibers act as an abrasive, so every breath can cause tissue damage---asbestosis); it is also a known carcinogen.

And so now we have the crux of the problem: we faced two distinct, very real risks, and someone had to make a decision: should we continue to use a tried-and-true fireproofing (Asbestos), knowing that it will cause indoor air problems and health risk as long as it is in place; or, do we switch to an alternative with less air pollutant risk, but also less track record of demonstrated performance as a fireproofing material?

I make it clear that the fire from the jet fuel was unbelievably hot: hot enough to soften steel! It is unlikely that ANY fireproofing would be able to withstand the blaze indefinitely. I ask the students: BUT…but…what if the fireproofing had held another 30 minutes? Another hour? Two hours? Would more occupants have escaped? Perhaps, would firefighters have been able to extinguish the blaze? No one can really answer such questions.

In fact, this discussion is not meant to provide definitive answers, but to raise questions. I challenge students to think about Environmental Science differently. It seems to work: at the end of the course, I ask students on the Final Exam to relate a favorite Case Study or real-life example. Of dozens presented through the course, this one is mentioned more than any other.