According to an article (by Dr. David J. Prezant, Chief Medical Officer of Fire Department of the City of New York (FDNY), USA and his colleagues from FDNY and Albert Einstein College of Medicine of Yeshiva University and Montefiore Medical Center in the Bronx, NY, USA) that was published in this week’s 9/11 Special Issue of The Lancet, New York male firefighters, who were in action during the 9/11 disaster at the World Trade Center, have a higher proportion of cancer compared to their non-exposed colleagues and a comparable sample of New York’s general population.
Researchers evaluated an eligible 9,853 male firefighters, all with existing health records dating back to well before 9/11 for the study. They assessed the number of cancer incidences in terms of potential links to exposure in the first 7 years following the 9/11-disaster and compared cancer incident rates in WTC-exposed firefighters with those in non-exposed firefighters. After adjusting variables, such as age, race, ethnic origin, and secular trends, the results were compared with figures from the US National Cancer Institute Surveillance Epidemiology and End Results (SEER) reference population.
The study originally comprised of more than 10,000 participants, of which 576 firefighters were excluded for age reasons (they would have been aged 60 years or older on 9/11/2001) as their small number could have generated statistically unstable age-adjusted rates. Other exclusions included 32 women, 13 Asians, and 8 Native Americans as well as 85 individuals who were diagnosed with cancer prior to 1996*.
From a total of 9,853 eligible participants, the ethnic breakdown consisted of 94% non-Hispanic white individuals, 3% non-Hispanic black and 3% Hispanic male firefighters with an average age of 44 years on 11 September 2001.
Findings revealed 263 cancer cases of firefighters in action at the WTC compared with an estimated 238 cases from the general population data; the non-exposed group showed 135 diagnosed cancer cases in comparison to 161 cases expected from the general population.
During a comparison of cancer incidents in WTC-exposed FDNY firefighters with that of the U.S.’s general male population with a similar demographic mix (using standardized incidence rations [SIR]), WTC-exposed FDNY firefighters showed a 10% increased risk of cancer and a 19% increased risk (adjusted for surveillance bias) compared with WTC-non-exposed FDNY firefighters.
Lower cancer rates in non-exposed firefighters compared to rates from the general population can be explained due to the ‘healthy worker effect’, in that FDNY firefighters have fewer smokers, strict pre-employment health requirements, and greater physical fitness standards than the general population.
There was no significant increase in specific types of cancers in WTC firefighters compared to site-specific cancers among the non-exposed group and that of the general male population; however, this may be due to the small number of participants failing to make a statistical impact. The authors nevertheless detected a trend of increased risk in 10 out of 15 studied types of cancer, including stomach-cancer, colon-, melanoma-, prostate-, thyroid-, non-Hodgkin lymphoma, bladder-, kidney-, pancreas-, and esophagus-cancer.
The authors noted a 58% lower rate of lung cancer in WTC exposed participants compared with the general population with no increased risk to the non-exposed group. Of the nine WTC firefighters diagnosed with lung cancer, all were smokers.
According to the authors:
“An association between WTC exposure and cancer is biologically plausible, because some contaminants in the WTC dust, such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and dioxins, are known carcinogens. Although some contaminants could cause cancer directly, WTC exposure could also trigger chronic inflammation, through microbial infections, autoimmune diseases, or other inflammatory disorders, all of which have been reported as factors in oncogenesis, both experimentally and epidemiologically. We believe the observed relative excess in cancer cases in WTC-exposed firefighters was unlikely to be the result of non-WTC firefighting exposures, because since 9/11, structural fires have decreased, personal protective equipment has improved, self-contained breathing equipment use has increased, and smoking rates in firefighters have declined. Our findings support continued monitoring of firefighters and other WTC-exposed cohorts to fully assess cancer risk related to these unique exposures.”
Dr James M. Melius from the New York State Laborers’ Health Fund in New York, USA, says in a linked comment:
“This report and future cancer studies should provide reassurance that medical follow-up is being done in a way that will detect new disease patterns in a timely manner and, hopefully, while there is time to intervene. The study also comes at an important time for the federally funded medical follow-up of these workers, which has just been guaranteed for the next 5 years. This medical program does not currently cover cancer treatment. The findings from the accompanying study show an increased overall cancer risk in these WTC-exposed firefighters, and significantly raised cancer risk at a few specific sites (i.e., melanoma, thyroid, prostate, and non-Hodgkin lymphoma) compared with the general population. These heightened risks, tempered by concerns about potential surveillance bias, support careful consideration of the addition of cancer to the medical disorders covered in the program. Waiting to do so until definitive cancer studies have been completed (probably many years from now) would be unfair and would pose a hardship for workers who willingly risked their health by responding without hesitation to the WTC crisis. Meanwhile, the New York City Fire Department and other groups caring for this population need to continue their efforts to assess cancer and other long-term health effects of WTC exposure.”
Written by Petra Rattue