Health Effects From 9-11 Attacks: Special Lancet Issue

Jim Kling

September 01, 2011

September 1, 2011 — The latest issue of The Lancet is devoted to the 10th anniversary of the September 11, 2001, attacks on the New York City World Trade Center (WTC), and features 3 studies of the health effects of those events on emergency responders. Two studies show increases in health problems among responders, including heightened risk for cancer and respiratory conditions, and a third shows a reduced death rate.

One of these studies focuses on 9853 male New York City firefighters who responded to the World Trade Center fire. The researchers had access to participants' health records going back well before the September 2001 attacks. They examined cancer incidence before the attacks, as well as during the following 7 years among both exposed firefighters and nonexposed firefighters.

The latest issue of The Lancet is devoted to the 9/11 attacks

Among WTC-exposed firefighters, there were 263 cases of cancer, compared with 135 cases in the nonexposed group. Models predicted that 161 cases should be expected in a nonexposed population. The exposed firefighters had a 10% increased risk of developing cancer when compared with a similar demographic mix of the male population of the United States. When compared with nonexposed New York firefighters, they had a 19% increased risk. Nonexposed firefighters had lower cancer rates than the general US male population, probably because they have lower smoking rates, are likely to be in better physical condition, and must meet stringent pre-employment health requirements.

According to the authors, the increased cancer rates among WTC-exposed firefighters could potentially be explained by contaminants in the WTC dust, including known carcinogens such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and dioxins. Exposure could also have led to chronic inflammation, which is believed to play a role in oncogenesis.

The results suggest that WTC-exposed firefighters should continue to be monitored for cancer incidence, the authors write.

Physical and Mental Illness

A second study considered physical and mental illness among rescue and recovery workers involved in the 9/11 attack. The study followed 27,449 of the approximately 50,000 rescue and recovery workers estimated to have been involved. The participants had voluntarily enrolled in the federally funded WTC Screening, Monitoring, and Treatment Program, which provides regular physical and mental health examinations to WTC rescue and recovery workers. Participants included police officers, firefighters, construction workers, and municipal workers.

The researchers divided participants into 4 categories based on their levels of exposure, each calculated by using days at WTC site, work in the pile of debris, and exposure to the dust cloud: low (14% of workers), intermediate (65%), high (18%), and very high (3%) exposure.

The participants were followed for 9 years after the attacks. There has been concern that inhalation of alkaline dust could cause respiratory problems, and the study suggests that concern could be warranted. Nine-year cumulative incidence rates were as follows: asthma, 28%; sinusitis, 42%; gastroesophageal reflux disease (GERD), 39%; and spirometric abnormalities, 42%.

Mental disorders also occurred at high cumulative rates, including depression (28%), post-traumatic stress disorder (PTSD, 32%), and panic disorder (21%). By comparison, police officers had cumulative incidence rates of 7% for depression and 9% for PTSD.

Disorders generally occurred at higher incidence in workers who had higher exposure. The trend held true for asthma, sinusitis, and GERD. Comorbidity was also common. About half (48%) of those who reported asthma also reported at least 1 mental health condition; 38% of those with sinusitis reported at least 1 mental health condition, as did 43% of those with GERD. The reverse was also true: 69% of rescue workers with PTSD reported at least 1 physical malady, as did 70% of those with depression and 72% with panic disorder.

This study supports previous findings that New York City police officers have lower risk of developing mental health disorders than some other responders. "Possible reasons for these findings include training, previous experience in dealing with similar stressors, self-selection of individuals with high resilience during recruitment into the workforce, and possible under-reporting of psychological symptoms because of perceived job-related repercussions," the authors write.

All-Cause Mortality Lower

Finally, a study of all-cause mortality rates among rescue workers and civilians involved in the 9/11 WTC attack found that death rates were lower than those in a comparison group drawn from the general New York City population.

For the period between 2003 and 2009, the team cross-referenced WTC Health Registry participants with New York City vital records and the National Death Index. Participants were categorized as rescue and recovery workers (including volunteers [RRWs]) or nonrescue and nonrecovery participants (NRNRs), a group that included lower Manhattan residents, area workers, school staff and students, and commuters and passersby.

The researchers also calculated standardized mortality ratios (SMRs) for residents of New York City between 2000 and 2009. Within-group comparisons were made between participants who were subjected to high and medium exposure and those who were subjected to low exposure.

There were 156 deaths among 13,337 RRWs and 634 deaths among 28,593 NRNRs. After adjustment for age, sex, race, and calendar year, compared with the general New York City population, study participants had a 43% reduction in all-cause mortality (SMR, 0.57). There were a 55% reduction of all-cause mortality (SMR, 0.45) among RRWs and a 39% reduction in NRNRs (SMR, 0.61).

There was no link between higher exposure and increased mortality rates among RRWs. Among NRNRs, higher exposures were associated with higher all-cause mortality rates (22% higher risk for intermediate exposure compared with low exposure and 56% higher for high exposure). NRNRs with high exposure levels were more than twice as likely to die of heart disease than those with low exposure.

The fact that death rates are not higher than those in the general population is not that surprising, the authors say, because the illnesses studied tend to have long latency or long survival periods. The finding that death rates are actually lower could be explained by the worker cohort effect: Most participants were employed, and those who are employed are healthier than the general population. Second, voluntary participants in health studies tend to be healthier than the general population. Both effects are likely to wane over time, so risk for premature death related to WTC-exposure will probably show up in the ongoing analyses of WTC Health Registry enrollees, the authors note.

An accompanying editorial (no author listed) offered the following reflection: "This anniversary should also remind us that the incomprehensible, large­scale loss of human life can obscure the small and terrifying tragedies that befall individuals and families. The tenth anniversary of 9/11 should be about the people who died, together with the families and communities that have been left behind — not only in America, but also in Iraq, Afghanistan, and all places that have suffered terrorist­related incidents worldwide."

One author of the study on physical and mental health effects among first responders is a member of the research board of EHE International. The other authors have disclosed no relevant financial relationships.

Lancet. 2011;378:898-905. 2011;378:879-887. 2011;378:888-897.


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