Kleinman, Eli J. MD, MPH; Cucco, Robert A. MD; Martinez, Charles MD; Romanelli, John MD; Berkowitz, Israel MD; Lanes, Norman MD; Lichtenstein, David MD; Frazer, Somjen; Lit, M; Moran, William AD
* Demonstrate familiarity with previous studies of changes in pulmonary function and associated factors among responders to the 2001 World Trade Center (WTC) disaster.
* Summarize the new findings in the New York Police Department Emergency Services Unit (ESU) cohort, including similarities and differences compared to other groups.
* Discuss the implications for continued follow-up of WTC responders and for urban disaster planning and preparedness.
Individuals who were present in the vicinity of the World Trade Center (WTC) collapse on September 11, 2001, were exposed to debris, dust and, more than 400 identified airborne pollutants.1,2 Early and persistent reductions in pulmonary function, compared with baseline measurements, have been reported in a variety of responder groups.3 Members of the New York City Police Department (NYPD) Emergency Services Unit (ESU)—a cohort without chronic pulmonary exposures—were deployed at the WTC site and exposed, along with other first responders, local residents, employees, and visitors, from the first moments of the disaster, through the protracted course of rescue and cleanup operations, nearly 1 year later.
Pulmonary function parameters (forced vital capacity [FVC], forced expiratory volume in the first second [FEV1]) were compared with baseline preexposure data, in 206 emergency service unit members of the NYPD, at 1 year following the WTC disaster, and after 5 more years of follow-up, examining the observed data for possible associations with (1) varying exposure intensities, (2) protective respiratory mask use, (3) respiratory symptoms, and (4) smoking history (Table 1).
The NYPD ESU of the Special Operations Division is a cohort comprised of individuals who have the same entry requirements and training as thousands of other patrol officers within the NYPD. They receive additional training geared to the particular tasks of rescue and recovery, some which require the maintenance of special technical and physical skills, and must also undergo mandatory annual Spirometry, as part of federal OSHA (Occupational Safety and Health Administration) certification required for the use of Specialized Contained Breathing Apparatus. The cohort is composed of 206 subjects, of which 98% are male and 2% are female, 84.5% white, 8.7% black, 6.3% Hispanic, and less than 1% Eskimo.
The average age in 2001 was 38.9 years, body mass index 30.4, mean height 70.6 inches, and mean weight 209.5 lbs, which rose to 211.7 lbs in 2002 and 215.4 lbs in 2007.
A smoking history was obtained in 18% of subjects in 2002 and 21.6% in 2007.
Participants responded to questionnaires regarding: location at the time of WTC collapse, number of hours engaged in rescue/recovery, protective respiratory mask use, smoking history, and presence of upper or lower respiratory symptoms. Subjects were interviewed and examined by clinicians from the NYPD Medical Division and underwent a series of laboratory evaluations including routine blood and urine analysis, electrocardiogram, chest radiography and spirometry.
Baseline spirometry measurements were available for all of the study subjects prior to 9/11/01, as part of federal OSHA requirements for this specialized unit, who mandate annual pulmonary function testing (PFT). Spirometers used were manufactured by Spacelab Burdick Spirotouch Systems, Deerfield, Wisconsin.
Acceptability criteria for spirometry were in keeping with American Thoracic Society (ATS) guidelines,4 and included smooth flow volume curve, reproducibility of two best FVC within 5% variation, and expiratory plateau greater than 1 second. Data were selected for those who responded to the WTC site with reproducible data within 36 months prior to 9/11/01 and appeared for follow-up postexposure PFT in 2002 and 2007. Thirty-seven spirometry results from the original complement of 241 subjects were omitted for failure to meet acceptability criteria.
Spirometry measurements of FEV1 and FVC, 80% of predicted or greater, were characterized as “Normal.” Reductions in pulmonary function to levels 60% to 79% of predicted, were characterized as “Mild,” to levels 40% to 59% of predicted, as “Moderate,” and levels less than 40% of predicted, as “Severe,” as defined by ATS criteria.4
Exposure Intensity/Arrival Time
Respondents were questioned regarding their location at the time of the collapse of the WTC towers. Experiencing the WTC debris cloud at ground zero at the time of collapse, or its immediate aftermath on 9/11/01, was defined as “Early Arrival Exposure.” Arrival at an interval following the collapse, but not experiencing the debris cloud, was designated as lower intensity “Later Arrival Exposure.”
Duration of exposures at the WTC site were divided into “Greater than 2000 Hours,” “Between 1000 and 2000 Hours,” and “Less than 1000 Hours.”
Protective Respiratory Mask Usage
The use of any type of Protective Respiratory Mask, for any portion of time at the WTC site, was defined as “Positive,” and if no respirator or mask was worn at any time, as “Negative.”
Complaints of Respiratory Symptoms were defined as “Symptomatic” for any positive responses to the questionnaire symptom list for upper or lower respiratory complaints and “Asymptomatic” if no respiratory symptoms were reported.
Smokers' responses were defined as “Positive” for any smoking activity prior to or during the study period and “Negative” if there was no past or current smoking history.
Associations of spirometry data with Smoking History, Respiratory Symptoms, Exposure Duration, Exposure Location/Arrival Time, and Protective Facial Mask Usage were tested via two-tailed t tests, 95% confidence intervals and P values, utilizing IBM SPSS Software Version 19 (IBM, SPSS Predictive Analytics, Chicago, IL).
One year following exposure to the 2001 WTC disaster, 206 members of the NYPD ESU participated in our study, 34% of whom experienced the debris cloud of the WTC collapse, whereas 66% arrived at the site at a later time, 46% were exposed for greater than 2000 hours, 41% were exposed between 1000 and 2000 hours, and 14% were exposed for less than 1000 hours. A protective respiratory mask of some type was worn by 94% of participants for most of their exposure time.
When questioned regarding the presence of upper or lower respiratory symptoms in 2002, 81% responded affirmatively, whereas 15.5% denied any respiratory symptoms. Eighteen percent of participants responded affirmatively to a history of smoking. Upon reevaluation in 2007, 139 individuals returned for follow-up (retention rate, 67.5%), of which 42.8% were symptomatic, 57.2% asymptomatic, and 22% were smokers. Sixty-seven individuals (30.5%) in the original cohort failed to reappear in 2007 because of service retirement (70.1%), nonpulmonary medical disabilities (17.9%), and the remaining (12%) for unknown reasons.
Pulmonary function data prior to 9/11/01 and follow-up testing in 2002 and 2007 are summarized in Table 1. The baseline FVC of 206 subjects tested within 36 months prior to 9/11/01 averaged 5.16 L (95% CI, 5.05 to 5.26 L). FVC measurements decreased by 190 mL (3.68%) in 2002 and by 330 mL (6.4%) in 2007 (95% CI, 4.86 to 5.08 and 4.69 to 4.97; P < 0.01), respectively.
FEV1 averaged 4.05 L pre-9/11/01, and 3.99 L in 2002, and fell 160 mL (3.95%) in 2007 (95% CI, 3.91 to 4.07 and 3.78 to 4.00) P = 0.02 (Figs. 1 and 2) (Table 1).
Pulmonary studies remained unchanged in functional classification from preexposure measurements (>80% predicted) in (95%) of the 206 subjects. In 5.3% of the subjects, pulmonary function parameters deteriorated from “Normal” to “Mild” reduction (60% to 79% of predicted). No subjects in the study population decreased to a “Moderate” (40% to 59% predicted) or “Severe” reduction in classification of pulmonary function (<40% predicted).
Significant pulmonary function declines were seen in individuals who complained of respiratory symptoms (upper or lower) at 1-year postexposure in 2002 and in 2007, with FVC declining 240 mL (4.67%) in 2002 (95% CI, 4.76 to 5.05 L) P = 0.03 and 470 mL (9.14%) in 2007 (95% CI, 4.49 to 4.85 L) P = 0.01. In asymptomatic individuals, FVC declined 120 mL (2.31%) in 2002 (95% CI, 4.92 to 5.23 L) P = 0.23 and 150 mL (2.88%) in 2007 (95% CI, 4.84 to 5.26 L) P = 0.17. (Fig. 3)
In symptomatic individuals, FEV1 declined 80 mL (2.01%) in 2002 (95% CI, 3.79 to 4.01 L) P = 0.24 and 260 mL (6.53%) in 2007 (95% CI, 3.58 to 3.86 L) P < 0.01. In asymptomatic individuals, FEV1 declined 30 mL (0.72%) in 2002 (95% CI, 4.02 to 4.25 L) P = 0.92 and remained unchanged in 2007 (95% CI, 3.97 to 4.29 L) P = 0.66. (Fig. 4) (Table 2)
Individuals with a positive smoking history showed reductions in FVC of 250 mL (4.84%) at 1-year postexposure in 2002 (95% CI, 4.63 to 5.19 L) P = 0.05 and 450 mL (8.72%) in 2007 (95% CI, 4.44 to 4.98 L) P = 0.02. In nonsmokers, FVC fell 160 mL (3.11%) in 2002 (95% CI, 4.87 to 5.10 L) P = 0.09 and 280 mL (5.4%) in 2007 (95% CI, 4.70 to 5.02 L) P < 0.01 (Fig. 5).
FEV1 in the smoking subgroup was less affected over the study period, than FVC, declining 70 mL (1.74%) in 2002 (95% CI, 3.74 to 4.16 L) P = 0.16 and 170 mL (4.23%) in 2007 (95% CI, 3.62 to 4.07 L) P = 0.07. Similarly, in non-smokers, FEV1 fell 70 mL (1.72%) in 2002 (95% CI, 3.92 to 4.09 L) P = 0.74 and 170 mL (4.18%) in 2007 (95% CI, 3.78 to 4.04L) P = 0.05 (Fig. 6) (Table 3).
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.
1. McGee JK, Chen LC, Cohen MD, et al. Chemical analysis of World Trade Center fine particulate matter for use in toxicologic assessment. Environ Health Perspect. 2003;111:972–980.
2. Lioy PJ, Weisel CP, Millette JR, et al. Characterization of the dust/smoke aerosol that settled east of the World Trade Center (WTC) in lower Manhattan after the collapse of the WTC. 11 September 2001. Environ Health Perspect. 2002;110:703–714.
3. Banauch GI, Hall C, Weiden M, et al. Pulmonary function after exposure to the World Trade Center collapse in the New York city fire department. Am J Respir Crit Care Med. 2006;174:312–319.
4. Crapo RO, Hankinson JL, Irvin C, et al. American thoracic society: standardization of spirometry. Am J Respir Crit Care. 1994;152:1107–1136.
5. Kerstjens HA, Rijcken B, Schouten JP, et al. Decline of FEV1 by age and smoking status: facts, figures, and fallacies. Thorax. 1997;52:820–827.
6. Prezant DJ, Weiden M, Banauch GI, et al. Cough and bronchial responsiveness in firefighters at the World Trade Center site. N Engl J Med. 2002;347:806–815.
7. Skloot G, Goldman M, Fischler D, et al. Respiratory symptoms and physiologic assessment of iron workers at the World Trade Center site. Chest. 2004;125:1248–1255.
8. Banuch GI, Alleyne D, Sanchez R, et al. Persistent hyperactivity and reactive airway dysfunction in firefighters at the World Trade Center. J Respir Crit Care Med. 2003;168:54–62.
9. Feldman DM, Baron SL, Bernard BP, et al. Symptoms, respirator use and pulmonary function changes among New York city firefighters responding to the World Trade Center disaster. Chest. 2004;125:1256–1264.
10. Herbstman JB, Frank R, Schwab M, et al. Respiratory effects of inhalation exposure among workers during the clean-up effort at the World Trade Center disaster site. Environ Res. 2005;99:85–92.
11. Banauch GI, Dhala A, Alleyne D, et al. Bronchial hyper-reactivity and other inhalation lung injuries on rescue/recovery workers after the World Trade Center collapse. Crit Care Med. 2005;33:S102–S106.
12. Herbert R, Moline J, Skloot G, et al. The World Trade Center disaster and the health of workers: five-year assessment of a unique medical screening program. Environ Health Perspect. 2006;114:1853–1858.
13. Aldrich TK, Gustave J, Hall CB, et al. Lung function in rescue workers at the World Trade Center after 7 years. N Engl Med. 2010,8;362:1263–1272.
14. Singh N, Davis GS Review: occupational and environmental lung disease. Curr Opin Pulm Med. 2002;8:117–125.
15. Blank GR Disposable particle masks. Occup Health Safety. 2005 May;74;(5:82,84–85
16. Mossman BT, Borm PJ, Castranova V, et al. Mechanisms of action of inhaled fibers, particles and nanoparticles in lung and cardiovascular diseases. Part Fibre Toxicol. 2007;4:4.
17. Gurgueira SA, Lawrence J, Coull B, Murthy GG, Gonzalez-Flecha B Rapid increases in the steady-state concentration of reactive oxygen species in the lungs and heart after particulate air pollution inhalation. Environ Health Perspect. 2002;110:749–755.
18. Ryu JH, Colby TV, Hartman TE, Vassallo R Smoking-related interstitial lung diseases: a concise report. Euro Respir J. 2001;17:122–132. Review.
19. Smith TJ Occupational exposure and dose over time: limitations of cumulative Exposure. Am J Ind Med. 1992;21:35–51.
20. Steele MP, Speer MC, Loyd JE, et al. Clinical and pathologic features of familial interstitial pneumonia. Am J Respir Crit Care Med. 2005;172:1146–1152.
21. Mauer PM, Cummings KR, Carlson GA Health effects of New York State personnel who responded to the World Trade Center disaster. J Occup Environ Med. 2007:49:1197–1205.
22. Clark AL, Skypala I, Coats AJ Ventilatory efficiency is unchanged after physical training in healthy persons despite an increase exercise tolerance. J Cardiovasc Risk. 1994;1:347–351.
23. NYS Legislative Bill S7456-2009 & A10741-2009 amending Chapter 104 of the laws of 2005 enacting the September 11th Worker Protection Task Force Act. Section 1 & 3 (2009).
24. NYS Legislative Bill 3659-A and B, Amendment 6281—A. Pataki, G. “World Trade Center Disability Law.” 2005.
25. Salzman S, Moosavy FM, Miskoff JA, Friedmann P, Fried G, Rosen MJ Early respiratory abnormalities in emergency services police officers at the World Trade Center site. J Occup Environ Med. 2004;46:113–122.
26. Scanlon P World Trade Center cough—a lingering legacy and a cautionary tale. N Engl J Med. 2002;347:840–842.
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