In an observational cohort study, firefighters exposed to the toxic cloud caused by the collapse of the towers had a 19% increased risk of cancer, compared with their peers who were not exposed, Mayris Webber, DrPH, of the New York City Fire Department, and colleagues reported in the Sept. 3 issue of The Lancet.
In a separate cohort of rescue workers, Juan Wisnivesky, MD, of Mount Sinai School of Medicine in New York City, and colleagues found a high incidence of such physical and mental disorders as asthma, sinusitis, depression, post-traumatic stress disorder, and panic disorder.
Webber and colleagues looked at cancer among 9,853 New York City firefighters, using state tumor registries and other appropriate documentation to confirm cancer cases. Of those, 8,927 were exposed to the World Trade Center fallout, while 926 were not.
The researchers compared cancer incidence among the exposed firefighters (until Dec. 31, 2008) with incidence among nonexposed firefighters and also with a reference population from the National Cancer Institute's Surveillance Epidemiology and End Results (SEER) database.
- Compared with the general male population with a similar demographic mix, exposed firefighters had a 10% increased risk of cancer. The standardized incidence ratio was 1.10 (95% CI 0.98 to 1.25).
- All told, the 8,927 exposed firefighters had 263 cases of cancer compared with 238 expected on the basis of the general population data.
- Compared with nonexposed firefighters, the standardized incidence ratio was 1.19 (95% CI 0.96 to 1.47).
- In the nonexposed group, there were 135 cases of cancer, compared with 161 expected from the general population.
Interestingly, the researchers noted, the exposed firefighters had a markedly lower risk of lung cancer than the general population, with a standardized incidence ratio of 0.42 (95% CI 0.20 to 0.86). All nine exposed firefighters with lung cancer were smokers.
The researchers attributed the difference to a "healthy worker" effect, since firefighters have lower smoking rates, tougher pre-employment health requirements, and greater physical fitness than most people.
A link between exposure to the World Trade Center fallout and cancer is "biologically plausible" – although speculative – because the dust contained a range of known carcinogens, the researchers noted.
But the results of the study should be taken with a grain of salt, they said, because the biological plausibility remains speculative, the seven-year study period is short for cancer outcomes, and the apparent excess of cases was not limited to specific cancer sites.
Although the study has some limitations, its value "far outweighs" them, according to James Melius, MD, of the NYS Laborers' Health Fund in Albany, N.Y.
"Despite the remaining uncertainty," Melius argued in an accompanying commentary, this 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."
Earlier this year, a government report concluded there was not enough evidence to link cancer among rescue workers to exposure to World Trade Center dust.
In the second study, Wisnivesky and colleagues looked at 27,449 men and women enrolled in a program that provides regular physical and mental health examinations for rescue and recovery workers.
They calculated the cumulative and annual incidence of a suite of physical and mental disorders over the nine years following the World Trade Center attacks, as well as assessing incidence by level of exposure.
- A nine-year cumulative incidence of 27.6% for asthma, 42.3% for sinusitis, and 39.3% for gastroesophageal reflux disease.
- Among police officers, the cumulative incidence of depression was 7%, compared with 27.5% in other rescue workers. Similarly, police offices had lower levels of post-traumatic stress disorder (9.3% versus 31.9%) and panic disorder (8.4% versus 21.2%) than did other rescue workers at the scene.
- Overall, the cumulative incidence of spirometric abnormalities was 41.8%, of which about three-quarters were low forced vital capacity.
Wisnivesky and colleagues argued that police officers might have been insulated from some of the mental problems by such mechanisms as training and previous experience in dealing with similarly stressful situations.
But, they added, it's also possible there was "under-reporting of psychological symptoms because of perceived job-related repercussions."
They cautioned that the study might not be representative because participation in the program was voluntary and the exact number of people involved in the rescue and recovery effort is not known with certainty.
Nevertheless, they argued, the study found that physical and mental health disorders are common among those involved in a major disaster, so that planning for future events "should anticipate the probability" of similar persistent illness in rescue and recovery workers.
Indeed, the findings "leave no doubt about the necessity of continuing health monitoring, treatment, and research for (World Trade Center) rescue and recovery workers," according to Matthew Mauer, DO, of the New York State Department of Health in Troy, N.Y.
In an accompanying commentary, Mauer wrote that knowledge of the health effects of major disasters "is rapidly improving, and studies such as that reported by Wisnivesky and colleagues represent important steps forward."
But it remains unclear how heavy the burden of disease will eventually be, he noted.
"One cannot help but wonder what will be reported when we mark the 20th anniversary of this tragedy," Mauer wrote. "For now, the view ahead is still murky, much like the plumes of acrid smoke that rose in New York City a decade ago."
The cancer study was supported by the National Institute for Occupational Safety and Health. The authors said they had no conflicts. Comment author Melius reported being employed by a joint labor-management fund for the Laborers Union in New York, which represents many of the workers at the WTC site. He also reported being involved in medical programs for these workers, including firefighters, but without compensation.
The disease burden study was supported by the CDC and the National Institute for Occupational Safety and Health. Wisnivesky reported being a member of the research board of EHE International. All other authors said they had no conflicts of interest.
Comment author Mauer said he had no conflicts.
- Reviewed by Dori F. Zaleznik, MD Associate Clinical Professor of Medicine, Harvard Medical School, Boston and Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner
The LancetSource Reference: Zeig-Owens R, et al "Early assessment of cancer outcomes in New York City firefighters after the 9/11 attacks: an observational cohort study" Lancet 2011; 378: 898–905.
The LancetSource Reference: Melius JM "Medical care for workers exposed to the WTC disaster" Lancet 2011; 378: 854-855.
The LancetSource Reference: Wisnivesky JP, et al "Persistence of multiple illnesses in World Trade Center rescue and recovery workers: a cohort study" Lancet 2011; 378: 888–897.
Additional source: The Lancet
Mauer MP "9/11: The view ahead" Lancet 2911; 378 852-854.