Declines in pulmonary function were also seen in responders who had greater exposure intensity, based on duration. In responders experiencing the highest intensity exposure (duration >2000 hours) FVC declined 170 mL (3.36%) at 1-year follow-up in 2002 (95% CI, 4.74 to 5.04 L) P = 0.016 and 340 mL (6.72%) at 5-year follow-up in 2007 (95% CI, 4.51 to 4.92 L) P < 0.001, whereas FEV1 declined 30 mL (0.75%) in 2002 (95% CI, 3.84 to 4.07 L) P = 0.32, and 120 mL (3.02%) in 2007 (95% CI, 3.7 to 4.03 L) P = 0.035. In the individuals with moderate exposure (1000 to 2000 hours), FVC fell 200 mL (3.81%) in the first year of study in 2002 (95% CI, 4.87 to 5.24 L) P = 0.81 and declined 270 mL (5.14%) in 2007 (95% CI, 4.276 to 5.19 L) P = 0.33, whereas FEV1 fell 80 mL (1.94%) in 2002 (95% CI, 3.9 to 4.17 L) P = 0.83 and 190 mL (4.61%) in 2007 (95% CI, 3.77 to 4.09 L) P = 0.28. In those with the lowest exposure duration (<1000 hours), FVC declined 120 mL (2.42%) in 2002 (95% CI, 4.53 to 5.12 L) P < 0.01 and 160 mL (3.23%) in 2007 (95% CI 4.3 to 5.28 L) P < 0.04, whereas FEV1 remained unchanged in 2002 with P = 0.09 and fell 100 mL (2.51%) in 2007 (95% CI, 3.49 to 4.27 L) P = 0.25 (Figs. 7 and 8) (Table 4).
Exposure Intensity/Arrival Time
Responders who were exposed to the debris cloud at ground zero at the time of the WTC collapse or its immediate aftermath showed declines in FVC of 240 mL (4.74%) in 2002 (95% CI, 4.68 to 4.97 L) P = 0.001, and 410 mL (8.1%) in 2007 (95% CI, 4.46 to 4.85 L) P < 0.001. FEV1 fell 60 mL (1.5%) in 2002 (95% CI, 3.83 to 4.07 L) P = 0.02 and 200 mL (5%) in 2007 (95% CI, 3.65 to 3.96 L) P = 0.001. In individuals who were not present at the time of the WTC collapse and the resulting debris cloud, FVC fell 170 mL (3.26%) in 2002 (95% CI, 4.90 to 5.12 L) and 230 mL (4.41%) in 2007 (95% CI, 4.8 to 5.18 L) P = 0.001. FEV1 declined 50 mL (1.23%) in 2002 (95% CI, 3.92 to 4.13 L) P = 0.13 and 100 mL (2.46%) in 2007 (95% CI, 3.82 to 4.13 L) P = 0.001 (Figs. 9 and 10) (Table 5).
Protective Respiratory Mask Usage
Most responders reported using fit-tested 3M N95 Respirator Masks (3M Corporation, St. Paul, MN), whereas few reported using standard construction dust masks. Individuals who made use of protective respiratory masks showed FVC reductions of 180 mL (3.48%) in 2002 (95% CI, 4.86 to 5.11L) P = 0.068 and 300 mL (5.8%) in 2007 (95% CI, 4.7 to 5.04 L) P = 0.005. FEV1 fell 80 mL (1.97%) in 2002 (95% CI 3.9 to 4.09 L) P = 0.45 and 150 mL (3.69%) in 2007 (95% CI, 3.78 to 4.05 L) P = 0.04. In individuals who did not used protective respiratory masks, FVC fell 240 mL (5.13%) in 2002 (95% CI, 4.04 to 4.83 L) P = 0.026 and 660 mL (14.1%) in 2007 (95% CI, 3.48 to 4.57 L) P = 0.068. FEV1 in this group fell 110 mL (2.91%) in 2002 (95% CI, 3.38 to 3.96 L) P = 0.38 and 420 mL (11.11%) in 2007 (95% CI, 2.89 to 3.8 L) P = 0.21. The number of subjects in these subgroups, however, was very small. (Figs. 11 and 12) (Table 6).
The expected decline in FEV1 in smokers has been estimated at approximately 0.5% per year (20 to 30 mL).4,5 Previous studies of rescue workers at the WTC sites have demonstrated reductions in lung volumes which have exceeded the decreases expected because of age-related changes alone.3 In this study, FVC declined 190 mL (3.7%) in 2002, whereas FEV1 appeared to be unaffected at 1 year following the WTC exposure. Spirometry measurements continued to decline in 2007, with FVC falling 330 mL (6.4%) and FEV1 160 mL (4.0%), about twice the expected decline for an average smoker for the study period.
Occupational studies of first responders with histories of chronic and repetitive respiratory exposures, such as firefighters, have reported an excessive decline in function in the first year following exposure, with subsequent PFT recovery.6–8 These studies also report differences in pulmonary function declines between individuals, based on exposure intensities such as arrival time at ground zero, and other variables.9,10
Pulmonary functional classifications remained unchanged over the study period in 95% of our subjects, whereas 5.3% of our cohort deteriorated from “normal” to “mild airway disease,” and none progressed to “moderate” or “severe disease” classifications, by ATS criteria.
In our study, significant differences were seen in pulmonary function in individuals who (1) experienced the debris cloud of the WTC collapse, (2) were exposed for longer periods of time, or (3) developed respiratory symptoms following exposure. Although some of these findings are consonant with observations noted in other responder groups studied,3,6,7,8,10–13 the type of pulmonary dysfunction observed in our cohort tended to be of a more restrictive or mixed pattern than obstructive in nature.
In our cohort, the FVC—a measure that is arguably more commonly affected in restrictive defects—was more prominently impacted by the WTC exposure than FEV1, more often identified as a measure of obstructive processes. This is not surprising, given the complex mix of dust and debris particles inhaled at the WTC collapse,1,2,14 which may have elicited a response similar to the pulmonary effects observed in some historical environmental exposures.15–17 The changes we observed in our cohort were particularly true for smokers, who showed continued FVC declines in the follow-up study period, whereas FEV1 declines between smokers and nonsmokers remained flat. These observations may point to a mixed defect developing in WTC-exposed smokers, with early restrictive changes, possibly followed by later appearing obstructive changes.14,18–20
In addition, the similarity in degree of pulmonary declines between our cohort and others studied7,12,13,21 seems to further dispel any postulated distinctions in the severity of pulmonary effects expected between responders having histories of chronic pulmonary exposures and those who do not. This may bode well for the ESU cohort, and possibly thousands of other exposed non-ESU NYPD officers, who share similar training, physical attributes (mean height, weight, body mass index), as well as postexposure spirometry, and have a lower mean age and lower smoking rates (NYPD Personnel Bureau data). Nevertheless, exposure to the unprecedented environmental event that the WTC disaster represents makes it impossible to confidently draw upon historical events or the relatively early reported findings, for predicting the nature of possible long-term sequelae, or for further prognostication, and may, in fact, require a new paradigm.14
Cohort subjects were members of the Emergency Services Unit, a self-selected group of officers who undergo specialized training for specific technical and physical capabilities required in rescue and recovery (ie, confined space operations, rappelling), who traditionally underreport symptoms and tend to downplay physical complaints and may have exhibited a well-observed reticence on the part of law enforcement populations, toward disclosing symptoms, for fear of stigmatization or job loss (healthy worker effect). Nevertheless, there is no evidence that the nature of this physical training has any significant impact upon pulmonary function parameters.22
The NYS WTC Disability Law was passed by the NYS Legislature in 2005,23,24 creating a presumption of causal relationship for any disabilities arising from exposure to the WTC disaster, and awarding those entitled with higher, tax-free pensions than otherwise granted, thus providing an incentive for symptom reporting. It is difficult to assess how this development may have impacted the responses to the questionnaire in 2007, or may have partially blunted any “healthy worker effect.” None of the members of this cohort retired because of a pulmonary disability related to the WTC disaster thus far (NYPD Personnel Bureau data).
Computed tomographic (CT) examinations were performed only when chest radiographs were read as “abnormal”; thus, detailed anatomic correlations to the PFT data were not routinely made.
The extent of use of respiratory protection devices such as masks and respirators, and their specific types, could not be more clearly ascertained, because of the chaotic situation attending the first days of the disaster. Such information might have better informed about the relative effectiveness of different respirator types and their mode of use.
The number of individuals in some of the subgroups studied was quite small, affecting the ability to extrapolate findings and draw larger conclusions.
The demographics of this cohort were not sufficiently large or diverse to distinguish differences related to gender, race, or ethnicity.
A cohort of responders from the Emergency Services Unit of the NYPD—having no history of repetitive pulmonary exposures—underwent serial PFT and clinical evaluations, before September 11, 2001, at 1 year following the 2001 WTC disaster and after more than 5 years of follow-up, in 2007. Significant declines in pulmonary function were observed in 5.3% of subjects, compared with their baseline preexposure measurements.
The reduced pulmonary function in this cohort was most significantly associated with (1) the presence of respiratory symptoms and (2) a history of high-intensity exposure, as defined by experiencing the debris cloud of the WTC towers collapse, or by the extended number of hours working at the WTC site. More severe pulmonary deficits were also observed in individuals who failed to don protective respiratory masks, and among smokers, as has been reported in other studies.6,7,9 Nevertheless, because of the small number of subjects in some of our subgroups (nonsmokers and non–mask wearers), wider conclusions cannot be drawn. Our findings do, however, mirror reports from other responder cohorts—both with and without histories of chronic, recurring pulmonary exposures—suggesting a similar pulmonary response across responder groups to the exposure of the WTC disaster debris cloud.13,25
The relatively mild pulmonary effects seen in most responder cohorts studied,8,11–13 the absence of pulmonary disabilities resulting from the WTC exposure in our cohort, and the dearth of such disabilities in thousands of other exposed NYPD responders, thus far (NYPD Personnel Bureau data), may provide encouraging expectations regarding the long-term prognosis for these groups. Nevertheless, despite objectively mild spirometry declines,12,13,26 and the fact that our cohort has fared well clinically over the study period, persistent or worsening pulmonary function seen in a significant number of subjects remains a continued concern and may be a harbinger of further difficulties arising in the future.14,19 Some of the subgroups in this cohort (smokers, symptomatic, and highly exposed) merit especially close observation, to monitor whether their pulmonary functions stabilize, resolve, or worsen over time, as the greater pulmonary declines observed in this study, may signal increased risk.
Moreover, the observations made in this study underscore the need for a comprehensive approach to urban disaster planning and preparedness.26 Particular attention is necessary for establishing guidelines for the use of effective personal protective gear, and limitations of tours of duty for workers engaged in rescue and recovery in environments where the potential exists for toxic exposure. Support for monitoring programs and long-term follow-up for exposed individuals, and for innovative approaches to more effective smoking cessation programs, may also be crucial. Attention to these issues will help guide clinicians and urban planners as to the direction and focus of existing monitoring programs and will be critical in helping to protect first responders and ordinary citizens caught up in the midst of natural or man-made urban calamities.
The authors gratefully acknowledge the Cornell University-NY Hospital Queens, SUNY Downstate/Long Island College Hospital, and Kingsborough Community College for providing additional venues for the NYPD WTC Medical Monitoring Program; the Office of the Police Commissioner and Chief of Personnel of the NYPD for their support; and the NYPD Police Surgeons and Nurses for providing the clinical evaluations. They extend special thanks to NYPD Det Sherise Elmore and SPAA Eileen Leone for their invaluable assistance with logistics, data entry, and the clerical requirements of this study.
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©2011The American College of Occupational and Environmental Medicine
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