The 9/11 Firefighters and Cancer Incidence: 'We Owe Them'

F. Perry Wilson, MD, MSCE


September 15, 2021

This transcript has been edited for clarity.

Welcome to Impact Factor, your weekly dose of commentary on a new medical study. I'm Dr F. Perry Wilson of the Yale School of Medicine.

September 11, 2001, was the day I learned the difference between the French word attaque, which you would use if someone attacked someone else, and the word attentat — for an attack against a building.


The latter was new to me, but the word was blared across every TV screen in Paris, where I had been working as a singing waiter in a gap year between college and medical school. The tidbit of knowledge got buried away as I sat watching 24-hour news coverage in a language I was only starting to understand.

For some reason, it's that word that keeps coming back to me — attentat. It can also be used to mean assassination — so much more cruel than a simple attack. It was surreal being out of the country on 9/11. I returned that Thanksgiving to see my country completely changed: flags hanging from every building and armed guards with assault rifles at every street corner.

Two thousand nine hundred and ninety-six people had died on that day, and I learned a new word. It wasn't fair.

The only thing that uplifted me were the stories of heroism, from the epic to the earthly. The boldness of the Flight 93 passengers. The bravery of the Fire Department of New York.

Three hundred forty-three firefighters died on 9/11. But thousands more were exposed to debris, particulate matter, fumes, and gases from the collapsed buildings. The World Trade Center site was a witch's brew of carcinogenic compounds, including benzene, arsenic, asbestos, sulfuric acid, phthalate esters, and pesticides.

That means the firefighters who survived the events of 9/11, or worked onsite afterward, might face an increased risk for cancer in the future. Now, 20 years out, we have some fairly robust follow-up on just those statistics, thanks to this paper appearing in BMJ Occupational and Environmental Medicine.

The researchers would follow over 10,000 male firefighters present at the World Trade Center on or just after 9/11. But before we look at the cancer incidence, we have to be aware of the major sources of potential bias here.

First, firefighters are not like the rest of us. They are way braver, obviously, but more important for this discussion, they tend to be in better physical shape and are less risk-averse. The researchers get around this issue by comparing the FDNY firefighters to another cohort, the Career Firefighter Health study, examining 8813 firefighters active on September 11 but living elsewhere in the country — no exposure to the Trade Center.


Compared with the New York guys, these firefighters were less likely to be White, more likely to smoke, and more likely to have military combat experience.

The other thing to bear in mind is that firefighters who worked at the World Trade Center were and are eligible for free health exams, including blood work and CT scans, even after retirement. That opens the door to surveillance bias; you might catch more cancers than otherwise, simply because you're looking closer and not because there is a true difference in incidence.

But enough with the caveats. Let me show you the results.

The age- and race-adjusted incidence of any cancer was 15% higher among the World Trade Center firefighters than in the general population. It was 5% higher among the control firefighters.


The highest risk was seen in prostate and thyroid cancers, with a markedly lower rate of lung cancer (which is explained by the fact that firefighters are less likely to smoke cigarettes than the general population). The weirdest finding no doubt is the high rate of thyroid cancers in the FDNY firefighters. There's not much that gives you thyroid cancer, save ionizing radiation, and multiple studies have reported no such radiation at the WTC site.

But was all this just due to the fact that these guys were being watched so closely? It's hard to tell. The detected cancers tended to be smaller and at an earlier stage in the FDNY group, which does suggest surveillance bias.

The authors tried to account for that by lagging the diagnosis for 2 years, essentially pretending everyone who got a cancer diagnosis got diagnosed 2 years later than they did. This attenuated the effect, but it was still there. Of course, it's possible 2 years isn't enough. When they lagged by 5 years, most of the effect was gone.


I'll also point out that, while the authors don't give us age-adjusted mortality data, 97.6% of the FDNY firefighters were still alive at the end of this 20-year follow-up, compared with 93% of the control firefighters. This is not to suggest that working at the World Trade Center is protective, but perhaps those health screenings really did make a difference, or perhaps FDNY firefighters are just a different breed.

In the end, though, I really hope we don't need to learn too much about the environmental health impacts of major terrorist attacks. Whether or not these firefighters are at increased risk for cancer, I don't think anyone can argue that we owe our close and careful attention to their health now and into the future. Anything less would just be un-American.

F. Perry Wilson, MD, MSCE, is an associate professor of medicine and director of Yale's Clinical and Translational Research Accelerator. His science communication work can be found in the Huffington Post, on NPR, and here on Medscape. He tweets @fperrywilson and hosts a repository of his communication work at

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