News Release

9/11 mortality study shows that, so far, World Trade Center-exposed rescue workers and

civilians have had lower death rates than New York City general population

Peer-Reviewed Publication

The Lancet_DELETED

A study assessing mortality from all causes in 9/11 NYC World Trade Center survivors shows that, so far, exposed rescue workers and civilians have lower death rates than a comparable sample of the New York City population. The findings are reported in an Article in this week's 9/11 special issue of The Lancet, written by Dr Hannah Jordan, Dr Steven Stellman, and colleagues at the World Trade Center Health Registry, New York City Department of Health and Mental Hygiene, NY, USA.

In this study, deaths occurring in 2003-09 in World Trade Center (WTC) Health Registry participants residing in New York City were identified through linkage to New York City vital records and the National Death Index. Study participants were categorised as rescue and recovery workers (including volunteers) (RRWs) or non-rescue and non-recovery participants (including lower Manhattan residents, area workers, school staff and students, and commuters and passers-by on 9/11) (NRNRs). The researchers calculated standardised mortality ratios (SMR), for New York City from 2000 to 2009 and used it as the comparison reference group. Relative mortality risk was also calculated within the cohort for participants who experienced high and medium exposure compared to those who had low exposure.

The study identified 156 deaths in 13 337 RRWs and 634 deaths in 28 593 NRNRs. All study participants combined were 43% less likely to have died from any cause than the New York City general population (SMR 0.57) (adjusting for age, sex, race, and calendar year). RRWs were 55% less likely to have died from any cause (SMR 0.45) compared with the city's general population, while NRNRs were 39% less likely to die (SMR 0.61). No increased SMRs for diseases of the respiratory system or heart, or for blood cancers, were found.

In RRW, higher exposure was not associated with higher all-cause mortality. Among NRNRs, both intermediate and high levels of WTC-related exposure were significantly associated with mortality when compared with low exposure (22% higher risk for intermediate exposure and 56% higher for high exposure). Among NRNRs, those with high levels of exposure were twice as likely to die from heart disease-related mortality when compared to those with low exposure.

The authors say: "Because most illnesses that are established or possible sequelae of WTC-related exposures have long latency or long median survival periods, the absence of a relation between reported dust-cloud exposure by itself and mortality risk in our study is not surprising."

The researchers suggest two reasons for lower mortality in the WTC-exposed population. The first is the widely recognised worker cohort effect—most of those exposed were employed, and employed people as a whole are healthier than the general population. Secondly, volunteers for health studies (such as the WTC Health Registry) are also usually in better health than the general population. The healthy worker and healthy volunteer effects are expected to diminish over time, so that if excess deaths among WTC Health Registry enrollees occur in the future, it will be possible to detect them through the registry's on-going analyses.

Respiratory and mental illnesses have been the most common conditions associated with 9/11 exposure. WTC-exposed individuals might also be at risk for premature death due to respiratory diseases, both new onset and existing, as well as complications of mental disorders, including substance abuse and other risk taking behaviors. Cardiovascular disease (CVD) has been associated with pollutant exposure and psychological stress in other settings, and therefore higher rates of CVD mortality might have resulted from 9/11-related exposures. Cancer is also a condition being evaluated because of concern about potential exposures to carcinogens in the WTC dust cloud; however, only now has sufficient time passed since the WTC disaster to begin the complex scientific process of determining whether or not cancer may be linked to WTC exposure. Most cancers have many different risk factors and can take decades to develop. As an exception, some blood cancers can develop a few years after exposure.

The authors conclude: "Among World Trade Center Health Registry participants residing in New York City, overall death rates in 2003󈝵 were not higher than expected when compared to the general New York City population.

However, within the cohort, non-rescue and non-recovery participants with high levels of WTC-related exposure had an increased risk of all-cause mortality and heart-disease-related mortality compared with those with low exposure. Continued monitoring of all-cause mortality and disease-specific mortality will be needed."

In a linked Comment, Dr James M. Feeney, Saint Francis Hospital and Medical Center Hartford, CT, USA, and Dr Marc K. Wallack, Metropolitan Hospital Center, New York City, USA, say: "Outside of psychiatric research, few data on the long-term sequelae of any terrorist event exist, but researchers caring for the WTC victims and responders are systematically rectifying that lack of reliable information. The study by Jordan and colleagues replaces supposition and assertion founded on anecdote with cold, hard, incontrovertible, well presented data. Most of the focus on disaster management is on preparation, critical mortality, and response, and that is why this article is so important. As a society, the more data we have about the events, plans, opportunities responses, motivations, modus operandi, and especially the aftermath, the more devices we have to take the terror out of terrorism."

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To interview Dr Hannah Jordan or Dr Steven Stellman, World Trade Center Health Registry, New York City Department of Health and Mental Hygiene, NY, USA, please contact Susan Craig/Chanel Caraway, NYC Health Department Press Office. T) +1 347.396.4177 E) pressoffice@health.nyc.gov

Dr James M. Feeney, Saint Francis Hospital and Medical Center Hartford, CT, USA. T) +1 860 830 1724 E) feeneymd@yahoo.com


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