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07-09-2011 | Article

9/11 exposure ‘may have increased firefighters’ cancer risk’


Free abstract

MedWire News: Firefighters exposed to the attacks on the World Trade Center (WTC) in 2001 appear to have a modest excess of cancer cases compared with the general male population, although the researchers caution against overinterpreting the findings.

After the 9/11 attacks, many first responders, including approximately 12,500 firefighters, were exposed to aerosolised dust comprising pulverised cement, glass fibers, asbestos, lead, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and polychlorinated furans and dioxins. In addition, they were exposed to burning jet fuel fumes at the time, and diesel fumes from heavy equipment over the subsequent 10-month recovery effort.

Mayris Webber, from the Albert Einstein College of Medicine Montefiore Medical Center in Brooklyn, New York, USA, and colleagues examined data on 9853 men employed as firefighters in 1996.

Person-time on and after 9/11 for 8927 firefighters was classified as WTC-exposed, while all person-time before 9/11 and person-time for 926 firefighters that did not attend 9/11 was classified as non-WTC-exposed. Confirmed cancer cases were compared with data from the US National Cancer Institute Surveillance Epidemiology and End Results (SEER) reference population.

Over 61,884 person-years for exposed firefighters and 60,761 person-years for non-exposed firefighters, there were 263 and 135 observed cases of cancer, respectively, compared with 238 and 161 expected cases, respectively. This gave standardized incidence ratios (SIRs) of 1.10 and 0.84, respectively, or an SIR of 1.32 for exposed versus non-exposed groups.

Interestingly, the team notes in The Lancet that, although WTC exposure was associated with increased SIRs for cancer in 10 of 15 sites included in the analysis, WTC-exposed participants had significantly lower rates of lung cancer compared with the general population, at an SIR of 0.42.

Correcting for possible surveillance or lead-time bias reduced the SIR for exposed versus non-exposed individuals for all cancer sites from 1.32 to 1.19. Similar effect sizes were observed on secondary analyses.

While noting the persistence of the excess cancer cases after correction, the team warns: "We remain cautious in our interpretation of these findings because the time interval since 9/11 is short for cancer outcomes, the recorded excess of cancers is not limited to specific sites, and the biological plausibility of chronic inflammation as a possible mediator between WTC-exposure and cancer outcomes remains speculative."

By Liam Davenport